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Application Report

High-Performance CMOS Image Sensor Power Supply inIndustrial Camera and Vision

Wenting Wu
ABSTRACTThis application note provides solutions for powering the high-performance CMOS image sensors of industrial
machine vision cameras or vision sensors for factory automation and control applications. This application reportshows the importance of selecting the right components to generate better power supply rails. Three different
solutions are approached, including a discrete solution and two integrated solutions based on different PMICs,
which feature:• Specific power sequences• Flexible capabilities for driving large output capacitors• Improved efficiency performances• Small sizes

Table of Contents
1 Introduction.............................................................................................................................................................................3
2 TI Solutions............................................................................................................................................................................. 5
3 Test Results...........................................................................................................................................................................19
4 Analysis................................................................................................................................................................................. 24
5 Summary............................................................................................................................................................................... 26
6 References............................................................................................................................................................................ 27
7 Revision History................................................................................................................................................................... 27

List of Figures
Figure 1-1. Specific Power Sequencing Needs........................................................................................................................... 4
Figure 2-1. Block Diagram of Discrete Solution Board................................................................................................................ 6
Figure 2-2. Block Diagram of PMIC TPS65000 Solution............................................................................................................. 7
Figure 2-3. Block Diagram of PMIC TPS650330-Q1 Solution..................................................................................................... 7
Figure 2-4. Power Supply Rejection Ration Versus Frequency and Input Voltage......................................................................9
Figure 2-5. Power Supply Rejection Ratio Versus Frequency and Output Current..................................................................... 9
Figure 2-6. Output Noise Versus Output Voltage.........................................................................................................................9
Figure 2-7. Noise Versus Frequency and CFFx.......................................................................................................................... 9
Figure 2-8. Load Transient Response Versus Voutx................................................................................................................... 9
Figure 2-9. The Block Diagram of TPS62841DLC.....................................................................................................................10
Figure 2-10. Efficiency vs Load Current (VOUT=1.8V)..............................................................................................................10
Figure 2-11. The Schematic of Discrete Solution.......................................................................................................................13
Figure 2-12. PCB Board of Discrete Solution............................................................................................................................ 14
Figure 2-13. Block Diagram of the TPS65000........................................................................................................................... 15
Figure 2-14. Block Diagram of the TPS650330-Q1................................................................................................................... 17
Figure 3-1. Power Sequences of CMOS Image Sensor Power Rails........................................................................................20
Figure 3-2. Efficiency of the Digital Rail Supplied by TPS7A90 or TPS62840 in PYTHON 300/500/1300 CMOS Image
Sensors.................................................................................................................................................................................. 21
Figure 3-3. Efficiency of the Digital Rail Supplied by TPS7A90 or TPS62841 in IMX25X/26X CMOS Image Sensors.............21
Figure 3-4. Power Sequences of the Power Rails of the CMOS Image Sensors Using the TPS65000 Solutions.................... 22
Figure 3-5. Power Sequences of the Power Rails of IMX25X/26X CMOS Image Sensors.......................................................23
Figure 4-1. Power Sequence of the Power Rails of PYTHON 300/500/1300 CMOS Image Sensors Using the 120-ms
Delay Time LM3880............................................................................................................................................................... 24
Figure 4-2. The Relationship Between Efficiency of the Whole System and the Intermediate Voltage for Powering
PYTHON 300/500/1300 CMOS Image Sensors.................................................................................................................... 25
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Figure 4-3. The Relationship Between Efficiency of the Whole System and the Intermediate Voltage for Powering
IMX25X/26X CMOS Image Sensors...................................................................................................................................... 25

List of Tables
Table 1-1. Power Requirements of Three High-Performance CMOS Image Sensors.................................................................3
Table 2-1. Power Solutions for Three Example CMOS Image Sensors...................................................................................... 5
Table 2-2. Summary of Devices in the Discrete Solution Board with Their Specifications........................................................ 10
Table 2-3. Setup of the LM3880 with Specific Power Sequencing Requirements..................................................................... 11
Table 2-4. Setup for Required Output Voltages of the LMR36015, TPS7A87, TPS7A90, and TPS62840................................ 11
Table 2-5. Summary of Components in TPS65000 with Their Specifications............................................................................15
Table 2-6. Set Up for Required Output Voltages of the TPS65000EVM Board......................................................................... 15
Table 2-7. Connecting the LM3880EVM Board with the TPS65000EVM Board........................................................................16
Table 2-8. Summary of Components in the TPS650330-Q1 with Their Specifications..............................................................18
Table 3-1. Configurations of the Discrete Solution Board for Six Cases....................................................................................19
Table 3-2. Efficiency of CMOS Image Sensor Power Systems..................................................................................................20
Table 3-3. Efficiency of the Whole System Using the TPS65000 Solutions...............................................................................22
Table 3-4. The Efficiency of the Whole System Using TPS650330-Q1 Solutions..................................................................... 23
Table 4-1. Selections of Resistors for the LMR36015 to Output 3.9V, 4V, 5V and 4.5V............................................................ 24
Table 4-2. Efficiency of the Discrete Solution and the TPS65000 Solution when Only Powering the Digital Rail of
IMX25X/26X CMOS Image Sensors...................................................................................................................................... 25
Table 4-3. TPS6284X and Buck Integrated in the Major Losses Comparison of the TPS65000...............................................25
Table 5-1. The Number of Components Used in each Solution.................................................................................................26

Trademarks
HotRod™ and DCS-Control™ are trademarks of TI.
All trademarks are the property of their respective owners.

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Introduction

1 Introduction
The power supply solutions presented in this application report are designed with the requirements of machine
vision applications for factory automation and logistics in mind. Machine vision has proven itself as a key
technology, addressing the needs of automated manufacturing, including:
•
•
•
•
•

Inspection
Identification
Quality control
Logistics
Robotics

TI information related to the topic of machine vision end equipment in industrial factory automation and control
area can be accessed here. A common block diagram of the industrial camera, as well as related TI products
and TI reference designs, can be accessed here.

1.1 Power Requirements of CMOS Image Sensors and Their Power Design Challenges
CMOS image sensors normally require three power rails with certain sequences for the analog part, pixel part(or interface part), and digital part. The voltage of the analog power rail is usually 3.3 V, the voltage of the pixel
power rail (or interface power rail) is usually 3.3 V or 1.8 V, and the voltage of the digital power rail is usually
1.8 V or 1.2 V. In order to improve the noise performance of CMOS image sensors, sometimes large bypass
capacitors are placed in front of the voltage supply pins of CMOS image sensors. The noise performance of
CMOS image sensors can also be improved by decreasing the fluctuation of each power rail. Generally, theanalog power rail is the most noise-sensitive rail; the pixel power rail is also sensitive to noise. In machine visionapplications, the camera is commonly small in size; for example, a 25-mm cube. Therefore, higher power rail
efficiency is necessary to improve the thermal performance and avoid degrading the color filters of a CMOS
image sensor.
In this application note, three high-performance CMOS image sensors, PYTHON 300/500/1300 series, PYTHON
3000/5000 series, and IMX25X/26X series, are selected as examples to be discussed. Through Table 1-1
and Figure 1-1, it can be seen that the rails of PYTHON series CMOS image sensors require large bypass
capacitors. The current consumption of the PYTHON 3000/5000 series is higher than other CMOS image
sensors. The power requirements of CMOS image sensors vary depending on different manufacturers andfeatures.
Table 1-1. Power Requirements of Three High-Performance CMOS Image Sensors
CMOS Image
Sensors

Power Rails

Rail Names

Voltage

Typ Current
Consumption

BypassCapacitors

Noise Sensitivity
Level

PYTHON
300/500/1300

Analog power rail

VDD_333.3 V

140 mA≤250 uFHigh

PIXEL power rail

VDD_PIXEL

3.3 V

5 mA

≤250 uF

MiddleDigital power rail

VDD_18

1.8 V

80 mA

≤10 uF

Low

Analog power rail

VDD_333.3 V

355 mA≤250 uFHigh

PIXEL power rail

VDD_PIXEL

3.3 V

10 mA

≤250 uF

MiddleDigital power rail

VDD_181.8 V

140 mA≤10 uF

Low

Analog power rail

AVDD

3.3 V

120 mA≤22 uF

High

Interface power
rail

OVDD

1.8 V

11 mA

≤22 uF

MiddleDigital power rail

DVDD

1.2 V

120 mA≤10 uF

Low

PYTHON
3000/5000

IMX25X/26X

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www.ti.com> 0 ms > 0 ms

> 0 ms > 0 ms
1.8 V
3.3 V
VDD_183.3 V

VDD_33
VDD_PIXEL(a) Powering sequences of PYTHON series< 200 ms<200 ms> 0 ms > 0 ms

> 0 ms > 0 ms
1.2 V

1.1 V
DVDD
OVDD

1.1 V

1.8 V
1.7 V

1.7 V

3.3 V

3.15 V

3.15 V

AVDD(b) Powering sequences of IMX series

Figure 1-1. Specific Power Sequencing Needs

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TI Solutions

2 TI Solutions
2.1 Solution Overviews
In this section, three solutions are introduced for powering the CMOS image sensors listed in Section 1.1. In
Table 2-1, the CMOS image sensors listed in Table 1-1 are matched to their suitable power solutions with thenotation YES.
Table 2-1. Power Solutions for Three Example CMOS Image Sensors
CMOS Image Sensors

Discrete Board
TPS65000 Solution(LMR36015
Solution(LMR36015+TPS7A87+ in the Discrete
TPS7A90/TPS6284X+LM3880)
Board Solution+TPS65000
EVM+LM3880 EVM)

TPS650330-Q1
Solution(TPS650330-Q1 EVM
Board)PYTHON 300/500/1300

Yes

Yes

N/A

PYTHON 3000/5000

Yes

N/A

N/A

IMX25X/26X

Yes

Yes

Yes

The first solution is a discrete solution shown in Figure 2-1. The discrete solution can power PYTHON
300/500/1300/3000/5000 series and IMX25X/26X series. For powering the IMX25X/26X series, the voltage
divider resistors and power sequences in the board need to be adjusted.
This solution includes:
•

•
•
•
•

The LMR36015, a wide input voltage buck converter, as the first power stage to convert high input voltages(5V, 12 V or 24 V) into a low intermediate voltage (4 V). This intermediate 4-V rail serves as the input voltage
for the second power stage, generating power rails for the CMOS image sensor and the power supply of thesequencer. In addition, the 4-V power rail can be used to power other electronic blocks of a camera.
The TPS7A87, a dual LDO device for powering the noise-sensitive analog rail and pixel rail (or interface rail)of the CMOS image sensors.
The TPS7A90, a single LDO for powering the digital rail of CMOS image sensors.
TPS6284X family low input voltage buck converters (TPS62840 for powering the digital rail of PYTHON
300/500/1300/3000/5000 series CMOS image sensors, and TPS62841 for powering the digital rail of
IMX25X/26X series CMOS image sensors).
The LM3880 analog sequencer to control the specific power sequence of each power rail.

The 2-pin header placed between the first power stage and the second stage is used for disconnecting thesestages to test them individually. There is a 3-pin header set between the TPS7A90 and TPS6284X, used tochoose either TPS7A90 as the digital rail power supply or TPS6284X as the digital rail power supply. There arethree 3 × 2 pins used to adjust the correct power sequences of power systems, according to power sequences
shown in Figure 1-1.
Highlighted features of the discrete solution board include:
•
•
•
•
•
•
•
•

Input voltage: 5 V / 12 V / 24 V, transients up to 60 V
4 V as intermediate voltage
Three low-noise and high PSRR output voltage rails (typically 1.2 V–3.3 V)
Output current up to 500 mA
Output capacitors up to 250 µF
Controlled power-up and power-down sequencing
Active output discharge
Small size (25 mm × 24 mm)

The second solution is mainly based on PMIC TPS65000 with the block diagram shown in Figure 2-2. Thissolution can support both powering the PYTHON 300/500/1300 series and IMX25X/26X series. For powering
the IMX25X/26X series, voltage divider resistors and power sequences in the board need to be modified. In
this solution, the LMR36015 in the discrete solution board is used as the first power stage to convert high input
voltages (5 V, 12 V, or 24 V) into a low intermediate voltage (4 V). The TPS65000 EVM is used as the second
power stage to convert the 4-V intermediate voltage to 3.3 V for the analog rail, 3.3 V for the PIXEL rail or 1.8 V
for the interface rail, and 1.8 V or 1.2 V for the digital rail. The LM3880 EVM is used to control the specific power
sequence of each rail.

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The third solution is based on PMIC device TPS650330-Q1 with the block diagram shown in Figure 2-3. Thissolution can support powering IMX25X/26X series CMOS image sensors. The input voltage of the system canbe up to 18.3 V. Voltage requirements and specific power sequence requirements of different CMOS image
sensors can be configured by setting up registers of the TPS650330-Q1 on the GUI.
CMOS image sensor
Discrete Solution Board
Analog_EN

Vin1

LDO1
500 mA

EN1

Vout1

Analog

3.3 V / 140 mA
VDD_33
3.3 V / 5 mA

LDO2
500 mAPIXEL_EN/
EN2
Interface_EN

PoE
DC
Adapter

VDD_PIXEL

Vin2

12 V 24 V (36 V)

Vin
EN

Buck
1.5 A

Vout2

PIXEL/IO
Interface

1.8 V / 80 mA
VDD_18Vout

PYTHON
300/500/1300
CMOS image sensor

TPS7A87

LMR36015
3.3 V / 355 mA
VDD_33Vin3LDO
500 mA

EN3
VCC
External Signal

EN

FLAG1
LM3880

Vout3

Digital

3.3 V / 10 mA
VDD_PIXEL
1.8 V / 140 mA

TPS7A90

VDD_18FLAG2PYTHON
3000/5000
CMOS image sensor

FLAG3
Digital_EN

Vin3

Buck
750 mA

EN3

Vout3

Digital

3.3 V / 120 mA
AVDD

TPS62840/TPS62841
1.8 V / 11 mA
FLAG1

OVDD
Digital_EN

Digital_EN

Analog_EN

Analog_EN

PIXEL_EN

PIXEL_EN

1.2 V / 120 mA

FLAG2
FLAG3

PYTHON
300/500/1300/3000/5000

DVDD

IMX25X/26X
CMOS image sensor

IMX25X/26X
CMOS image sensor

Sequence controlling signals for power railsof each CMOS image sensor

Figure 2-1. Block Diagram of Discrete Solution Board

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CMOS image sensor

Analog_EN

Vin1

LDO2
300 mA

EN1

AnalogVout1

3.3 V / 140 mA
VDD_33
3.3 V / 5 mA

12 V / 24 V (36V)
PoE

LDO1
300 mA

Vin3

Buck
600 mAVout2

PIXEL/IO
Interface

1.8 V / 80 mA
VDD_184V

Vin

DC
Adapter

VDD_PIXEL

Vin2
PIXEL_EN/
EN2
Interface_EN
Buck
1.5 A

EN

Vout

EN3

Vout3

DigitalPYTHON
300/500/1300
CMOS image sensor

LMR36015
TPS65000 EVM

3.3 V / 355 mA
VDD_33
3.3 V / 10 mA
VDD_PIXEL
1.8 V / 140 mA

FLAG1

VCC
External Signal

LM3880EN

VDD_18

FLAG2
FLAG3

FLAG1

IMX25X/26X
CMOS image sensor

Digital_EN

Digital_EN

Analog_EN

Analog_EN

PIXEL_EN

PIXEL_EN

FLAG2
FLAG3

PYTHON
300/500/1300
CMOS image sensor

IMX25X/26X
CMOS image sensor

Sequence controlling signals for power railsof each CMOS image sensor

Figure 2-2. Block Diagram of PMIC TPS65000 Solution
12 V Input Voltage
PoE
DC
Adapter

Vin1

Buck1
1500 mA

Vout1

Vin4

LDO
300 mA

Vout4

Vin3

Buck3
1200 mA

Vout3

3.3 V, 120 mA

AVDD

OVDD

4V

1.8 V, 11 mA
DVDD

Vin2

Buck2
1200 mA

Vout2

1.2 V, 120 mA

IMX25X/26X
CMOS image sensor

SEQ
TPS650330-Q1 EVM

Figure 2-3. Block Diagram of PMIC TPS650330-Q1 Solution

2.2 Design of the Discrete Solution Board
2.2.1 Device Selection
When selecting devices, the specifications of power management devices that can meet the power requirementsof each rail in the CMOS image sensor listed in Table 1-1 must be emphasized firstly. These include:•••

Input voltage range (Vin)
Output voltage range (Vout)
Output current range (Iout)

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Output capacitance (Cout)
Output voltage tolerance

Other considerations of designing the discrete solution board are presented in Section 2.2.3. Besides, since thedigital rail of a CMOS image sensor is not noise-sensitive, both LDO TPS7A90 and buck converter TPS6284X
can be considered for powering the digital rail.
a) LMR36015 4.2-V to 60-V, 1.5-A ultra-small synchronous step-down converter
The LMR36015 regulator is an easy-to-use, synchronous, step-down DC/DC converter. With integrated high-side
and low-side power MOSFETs, up to 1.5 A of output current is delivered over a wide input voltage range of 4.2
V to 60 V. Tolerance goes up to 66 V. The transient tolerance reduces the necessary design effort to protect
against overvoltages and meets the surge immunity requirements of IEC 61000-4-5. The LMR36015 uses
peak-current-mode control to provide optimal efficiency and output voltage accuracy. Load transient performanceis improved with the FPWM feature in the 1-MHz regulator. Precision enable gives flexibility by enabling a directconnection to the wide input voltage or precise control over device startup and shutdown. The power-good
flag, with built-in filtering and delay, offers a true indication of system status, eliminating the requirement foran external supervisor. The LMR36015 is in a HotRod™ package that enables low noise, higher efficiency, andthe smallest package-to-die ratio. The device requires few external components and has a pinout designed
for a simple PCB layout. The small solution size and feature set of the LMR36015 are designed to simplify
implementation for a wide range of end equipment, including the space-critical applications of ultra-small fieldtransmitters and vision sensors. The LMR36015 device is available in the VQFN-HR (12) package with body size
2 mm × 3 mm.
The LMR36015 device has several versions, defined by the switching frequency and whether there is forced
PWM (FPWM) mode or not. In the discrete solution, the LMR36015FB version is used with FPWM mode addinga 1-MHz switching frequency.
b) LDOs selected
Two LDOs are used to power noise-sensitive rails, analog rails, and PIXEL or IO interface rails. For powering
noise-sensitive rails, the following LDO specifications become more important.
•
•
•
•
•
•

Low noise in full temperature range.
High PSRR (power supply rejection ratio), even at low headroom-voltage (VIN-VOUT).
High accuracy.
Active output discharge.
Stabile with large output capacitors.
Adjustable start-up inrush control.

TPS7A87 Dual 500 mA Low-Noise (3.8 μVRMS) LDO Voltage Regulator and TPS7A90 Single 500 mA
High-Accuracy, Low-Noise, Low-Dropout (LDO) Voltage Regulator
Both the TPS7A87 and TPS7A90 are low-noise (TPS7A87, 3.8 μVRMS and TPS7A90, 4.7 μVRMS), lowdropout (LDO) voltage regulators capable of sourcing 500 mA with only 100 mV of maximum dropout. Eachoutput of the TPS7A87 is adjustable from 0.8 V to 5.2 V with external resistors, and the TPS7A90 output isadjustable from 0.8 V to 5.7 V with external resistors. Wide input voltage ranges of the TPS7A87 and TPS7A90
support operation as low as 1.4 V and up to 6.5 V. With 1% output voltage accuracy (over line, load, andtemperature) and soft-start capabilities to reduce inrush current, both LDOs are ideal for powering sensitive
analog low-voltage devices, including:
•
•
•
•
•

Voltage-controlled oscillators (VCOs)
Analog-to-digital converters (ADCs)
Digital-to-analog converters (DACs)
Complementary metal oxide semiconductor (CMOS) sensors
Video application-specific integrated circuits (ASICs)

The TPS7A87 device is available in the WQFN (20) package with body size 4 mm × 4 mm. The TPS7A90 device
is available in WSON (10) with body size 2.5 mm × 2.5 mm.

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100

80

VINx = 1.4 V
VINx = 1.45 V
VINx = 1.5 V

VINx = 1.55 V
VINx = 1.6 V
VINx = 1.65 V

60

40

20

0
10

100

1k

10k
100k
Frequency (Hz)

1M

80

60

40

20

0
10

10M

Figure 2-4. Power Supply Rejection Ration Versus
Frequency and Input Voltage

100

1k

10k
100k
Frequency (Hz)

1M

10M

Figure 2-5. Power Supply Rejection Ratio Versus
Frequency and Output Current
10

14

CFFx = 0 μF
CFFx = 0.01 μF
CFFx = 0.1 μF

CFFx = 10 nF, C NR/SSx = 10 nF
CFFx = 100 nF, C NR/SSx = 1 μF
121Noise (μV/√Hz)

Output Votlage Noise ( μV RMS)

IOUTx = 10 mA
IOUTx = 50 mA
IOUTx = 100 mA
IOUTx = 250 mA
IOUTx = 500 mA

VINx = 1.7 V

Power-Supply Rejection Ratio (dB)

Power-Supply Rejection Ratio (dB)

100

10

8

0.1

0.01

6

4
0.8

1.6

2.4
3.2
4
Output Voltage (V)

4.8

0.001
1E+1

5.6

Figure 2-6. Output Noise Versus Output Voltage

1E+2

1E+3
1E+4
1E+5
Frequency (Hz)

1E+6

1E+7

Figure 2-7. Noise Versus Frequency and CFFx

AC-Coupled Output Votlage (mV)50
IOUTx = 1 mA to 500 mA
IOUTx = 10 mA to 500 mA
IOUTx = 50 mA to 500 mA
IOUTx = 100 mA to 500 mA

25

0

-25

-50
0

200

400
600
Time (μs)

800

1000

Figure 2-8. Load Transient Response Versus Voutxc) TPS6284X 60-nA IQ, 1.8-V to 6.5-VIN, High-Efficiency 750-mA Step-Down Converter
The TPS6284X is a high-efficiency step-down converter with an ultra-low operating quiescent current of typically
6 nA. The device contains special circuitry to achieve just 150-nA IQ in 100% mode to further extend battery
life near the end of discharge. The device uses DCS-Control™ to cleanly power radios and operate with atypical switching frequency of 1.8 MHz in Power-Save Mode. The device extends the light-load efficiency down
to a load current range of 1 μA and below. 16 predefined output voltages can be selected by connecting a
resistor to pin VSET, making the device flexible for various applications with a minimum amount of external
components. The STOP pin on the device immediately eliminates any switching noise in order to take a

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noise-free measurement in data acquisition systems. The TPS6284X provides an output current of up to 750 mA
with an input voltage of 1.8 V to 6.5 V.
The TPS6284X device is available in 8-pin SON with body size 1.5 mm × 2 mm, 6-pin WCSP with body size
0.97 mm × 1.47 mm, and 8-pin HVSSOP with body size 3 mm × 5 mm.
The TPS6284X device has several versions defined by output voltage range, mode selection function, and stopfunction. In the discrete solution, the TPS62840DLC version with mode selection function is used to power the
1.8-V digital rail of the PYTHON 300/500/1300/3000/5000 series CMOS image sensors. The TPS62841DLC
version, also with mode selection function but with 0.8-V to 1.55-V output voltage range, is used to power the
1.2-V digital rail of the IMX25X/26X series CMOS image sensors.
Typical Application

VIN

VIN

MODE

MODE

RUN/STOP

STOP

90
85

VOUT

SW

CI
4.7 µF
GND

95

CO
10 µF

VOS

Efficiency (%)

TPS62841 DLC

100
L
2.2 µH

80
75
70
65

VIN = 1.8V
VIN = 2.5V
VIN = 3.0V
VIN = 3.6V
VIN = 4.2V
VIN = 5.0V
VIN = 6.5V

60
55
50

ENABLE

EN

VSET

45
40
100n

RSET

Figure 2-9. The Block Diagram of TPS62841DLC

1P

10P

100P
1m
10m
Output Current (A)

100m

1

Figure 2-10. Efficiency vs Load Current(VOUT=1.8V)d) LM3880 Three-Rail Simple Power Sequencer with Fixed Time Delay
The LM3880 simple power supply sequencer offers the easiest method to control the power-up and power-down
sequencing of multiple independent voltage rails. By staggering the start-up sequence, it is possible to avoid
latch conditions or large in-rush currents that can affect the reliability of the system. Available in a 6-pin
SOT-23-6 package, the Simple Sequencer contains a precision enable pin and three open-drain output flags.
The open-drain output flags permit the device being pulled up to distinct voltage supplies separate from thesequencer VDD (so long as they do not exceed the recommended maximum voltage of 0.3 V greater than the
VDD), so as to interface with ICs requiring a range of different enable signals. When the LM3880 is enabled,
the three output flags are sequentially released after individual time delays, thus permitting the connected power
supplies to start up. The output flags follow a reverse sequence during power down to avoid latch conditions.
EPROM capability allows every delay and sequence to be fully adjustable. The body size of LM3880 is 2.90 mm
× 1.60 mm.
The LM3880 has several versions defined by delay time. In the discrete solution, the LM3880MF-1AB is selected
to provide a 30-ms delay time between each power rail of the CMOS image sensors.
Table 2-2lists the previously mentioned power management devices with their corresponding power rail of
CMOS image sensors. Table 2-3lists FLAGs of the LM3880 assigned to control the power sequences.
Table 2-2. Summary of Devices in the Discrete Solution Board with Their Specifications
Devices

Power Railof CMOS
Image Sensors
Supplied

Vin

Vout

Iout

Cout

Selected SW
Frequency

LMR36015FB

As the first powerstage to convert
high input voltage(12 V/24 V)
from PoE or DC
adapter to a 4
V intermediate
voltage

4.2 V–60 V

Vref to Vin-0.4 V

1.5 A

-

1 MHz (Used in
FPWM mode)

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Table 2-2. Summary of Devices in the Discrete Solution Board with Their Specifications (continued)
Devices

Power Railof CMOS
Image Sensors
Supplied

TPS7A87

Vin

Vout

Iout

Cout

Selected SW
Frequency

VDD_33 and
1.4 V–6.5 V
AVDD (LDO1 of
TPS7A87)VDD_PI
XEL and OVDD(LDO2 ofTPS7A87)

0.8 V to 5.2 V(Vdo=0.1 V at 0.5A)

500 mA≥10 uF-TPS7A90

VDD_18 andDVDD

1.4 V–6.5 V

0.8 V to 5.7 V(Vdo=0.1 V at 0.5A)

500 mA≥10 uF-

TPS62840DLC

VDD_18

1.8 V–6.5 V

1.8 V–3.3 V

750 mA

3 uF to 40 uF

1.8 MHz (Used in
FPWM mode)

TPS62841DLC

DVDD

1.8 V–6.5 V

0.8 V–1.55 V

750 mA

3 uF to 40 uF

1.8 MHz (Used in
FPWM mode)

Table 2-3. Setup of the LM3880 with Specific Power Sequencing Requirements
CMOS Image Sensor

Controlled Power RailFLAG in LM3880

Power Up Order

Power Down OrderPYTHON
300/500/1300/3000/5000

VDD_33

FLAG2

2

2

VDD_PIXEL

FLAG3

3

1

VDD_18

FLAG1

1

3

AVDD

FLAG3

3

1

OVDD

FLAG2

2

2

DVDD

FLAG1

1

3

IMX25X/26X

2.2.2 Considerationa) Setting Output Voltages
The output voltages of the LMR36015, TPS7A87, and TPS7A90 can be set up by defining resistor divider
networks. Equation 1 can be used to calculate output voltages for the TPS7A87 and TPS7A90. This resistive
network must provide a current greater than or equal to 5 μA for optimum noise performance. Vref is nominally
0.8 V.

••

R1 = R2 Vout/Vref − 1
Vref max /R2 > 5 µ A(1)

R1 is the resistor between FB pin and OUT pin of TPS7A87 or TPS7A90.
R2 is the resistor between FB pin and ground.

In the LM36015, the voltage divider network is comprised of RFBT and RFBB. The output voltage can becalculated using Equation 2. The recommended value for RFBT is 100 kΩ, with a maximum value of 1 MΩ.
If 1 MΩ is selected for RFBT, then a feed-forward capacitor must be used across this resistor to provide anadequate loop phase margin. Vref is nominally 1 V.
RFBT = RFBB Vout/Vref − 1(2)

The output voltage of the TPS62840 or TPS62841 is set by a single external resistor connected between the
VSET and GND pins. For more details, please refer to the TPS6284X data sheet.
Table 2-4. Setup for Required Output Voltages of the LMR36015, TPS7A87, TPS7A90, and TPS62840
DeviceOutput Voltage Required

Value of R1

Value of R2

LMR36015FB

4V

100 KΩ

33.2 KΩTPS7A87

3.3 V

33.2 KΩ

10.7 KΩ

1.8 V

13.7 KΩ

11 KΩ

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Table 2-4. Setup for Required Output Voltages of the LMR36015, TPS7A87, TPS7A90, and TPS62840(continued)
DeviceOutput Voltage Required

Value of R1

Value of R2

TPS7A90

1.8 V

13.7 KΩ

11 KΩ

1.2 V

5.9 KΩ

11.8 KΩTPS62840DLC

1.8 V

Rset 0 KΩ

TPS62841DLC

1.2 V

Rset 15.8 KΩ

b) Soft-Start Capacitor (CNR/SS) and Feed-Forward Capacitor (CFF) for the TPS7A87 and TPS7A90
The CNR/SS capacitor serves the dual purpose of both reducing output noise and setting the soft-start ramp
during turn on. The CFF capacitor optimizes the transient, noise, and PSRR performance of the LDO. Both ofthem can influence the start-up time of the LDO, as shown in Equation 3.
tstartup = tref + tCFF

(3)

V +C
tref = ssI ss
ss

•
•
•
•

tCFF = 3R1 × CFF

tref is determined by the internal soft-start charging circuit.
Vss is internal reference voltage.
Iss is soft start current.
tCFF is determined by the top resistor in resistor divider network and feedforward capacitor.

If tCFF< tref, there is no issue with the power good (PG) function. If tCFF> tref, there is a problem on the power
good (PG) function. Refer to thePros and Cons of Using a Feedforward Capacitor with a Low-Dropout Regulator
Application Report for more details. In the design of the discrete solution board, specific start-up time and goodtransient performance are required. A higher CFF value can lower output currents of the LDO during soft start
to avoid reaching the fold-back current limitation, but a higher CFF value lasts the start-up time and causes the
problem with the power good function. A higher CSS value can improve linearity by increasing start-up time toimprove the transient performance of LDO, but it also increases start-up time. In the discrete solution board,a 10-nF capacitor is selected for the CFF. The SS_CTRLx pin is connected to the GND to provide a lower
current, 6.2 μA, so a smaller value capacitor at 820 pF can be selected for CSS. Considering the needs for
accurate control of start-up time, ceramic capacitors with COG-rated dielectric materials are used to provide agood capacitive stability.
c) Inductor and Capacitor Selections for the LMR36015 and TPS6284X
If simulation results are combined through WEBENCH simulation results, the inductor value 4.7 µH is selected
for the LMR36015. More information about inductor selection can be found in the LMR36015 data sheet. The
2.2-µH inductor value used for the TPS62840 and TPS62841 refers to the TPS6284X data sheet.
A minimum ceramic capacitance of 4.7 μF is required on the input of the LMR36015, according to the
LMR36015 data sheet. In addition, a small-size 220-nF ceramic capacitor must be placed at the input, andas close as possible to the regulator. This provides a high-frequency bypass path for the control circuits internal
to the device. In the discrete solution board, the 4.7-μF, 50-V, X7R (or better) ceramic capacitor is chosen as
shown in Figure 2-11 . The input capacitor value 4.7 µF used for the TPS62840 and TPS62841 refers to the
TPS6284X data sheet.
In the discrete solution board, the value of the output capacitor can be calculated as at least 7.3 μF. If simulation
results are combined through WEBENCH, the output capacitor value of two 22 µF in parallel is selected for
LMR36015. The output capacitor value 10 µF used for the TPS62840 and TPS62841 refers to the TPS6284X
data sheet.

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Cboot
25V
0.1uF

U4
10
2

VIN
VIN

BOOT

9

EN

1
11

SW
NC

PGND
PGND

PG

8

5

VCC

FB

7

2
4

TP13

RPG

J4

100k
TP1

Rfbt
100k

1

CINx2
220nF
50V

GND

G

2

CINx1
220nF
50V

6

AGND

CFF
50V
22pF
Cout
22µF
10V

LMR36015FBRNXR
Ccc
1µF
10V

VCC_4V

3
1

4.7uH

1
2

1
2

12
3

5004
CIN
50V
4.7uF

J6

L1

4
2

J0
1
3

J5

4

Coutx
22µF
10V

GND
Rfbb
33.2k

GND
VCC_4VU1
VCC_4VEN

FLAG2

5 FLAG2

EN1

18

GND

CNR/CSS1

VCC_4V

25V
820pF

19

Re2
10.0k

JEN
1
2
3

FLAG3

GND

GND

4 FLAG3

CIN2
10V
10uF

2

Pixel/Interface

LM3880MF-1AB/NOPB
GND

FLAG1

2
4
6

AnalogPixel/Interface
Digital2
46AnalogPixel/Interface
Digital2
46AnalogPixel/Interface
DigitalSS_CTRL1

PG1

17NR/SS1

FB1

16

4
5

IN2
IN2

6

EN2

7

OUT2
OUT2

1
3
5

FLAG3

1
3
5

PG2

9

NR/SS2

FB2

10

GND
GND

3
13

PAD

21

Digital

9
10

IN
IN

OUT
OUT

1
2

7

EN

PG

5

6

SS_CTRL

FB

3

NR/SS

GND
PAD

4
11

GND
CNR/CSS3
8

J8
TP10

GND
GND

RPG2
100k

J2

TP3
R21
33.2k

1

Cff2
25V
0.01µF

1
2

COUT2
10V
10uF

G

R22

GND
GND

10.7k
GND

GND

U2

CIN3
10V
10uF

VCC_4V
TP9

1
2

COUT1
10V
10uF

G

TPS7A8701RTJR

J_FLAG3

TP8

1

Cff1
25V
0.01µF11
12

SS_CTRL2

J_FLAG2
FLAG2

J1

TP2
R11
33.2k

R12

TP15

25V
820pF

GND

RPG1
100k

TP14

GND

CNR/SS2

GND

J_FLAG1
1
3
5

14
15

10.7k

8

GND

OUT1
OUT1

2

IN1
IN1

20

1
2
3

TP12

25V
820pF

GND

TP16RPG3
100k

GND

0OHM

G

11.0k

GND
GND
J9
GND

L2

2

VIN

SW

7

3

MODE

VOS

8

4

EN

6

STOP

5

2.2uH

J10
COUT4
10µF
10V

TP11
1

VSET

1
2

G

2

Digital

COUT3
10V
10uF

1

R32

GND

CIN4
10V
4.7uF

J3

TP4

Cff3
25V
0.01µFTPS7A9001DSKR
U2_DC

GND

R31
13.7k

3
1

FLAG1

3

Analog

GND

4
2

VCC

6 FLAG1

R3
100k

2

1

R2
100k

2

R1
100k

U3

1
2

1
2

Re1
22.0k

CIN1
10V
10uF

1

0
GND

TPS62840DLCR
GND

GND

GND

Figure 2-11. The Schematic of Discrete Solution
2.2.3 Discrete Solution PCB Board Description
The discrete solution PCB board is shown in Figure 2-12. The body size is 25 mm × 24 mm without considering
test points. J6 is used to disconnect the first and second power stage and then test them individually. J8 is used
to choose either the TPS7A90 or TPS6284X for powering the digital rail of the CMOS image sensors. J_FLAG1,
J_FLAG2, and J_FLAG3 are used to select powering sequences where row 1 is selected for analog rail, row 2 isselected for the PIXEL or interface rail, and row 3 is selected for digital rail.

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Figure 2-12. PCB Board of Discrete Solution

2.3 Design of the TPS65000 Solution
2.3.1 Device Selection
TPS65000 2.25 MHz Step-Down Converter with Dual LDOs and SVS Power Management IC (PMIC)The TPS6500XX devices are single-chip power management (PWM) ICs for portable applications. It contains asingle step-down converter and two low-dropout (LDO) regulators. The step-down converter enters a low-powermode at light load for maximum efficiency across the widest possible range of load currents. For low-noise
applications, the devices can be forced into fixed-frequency PWM through a pin. The step-down converter issmall because of the small inductor and capacitors. The step-down converter has a power good status output
for sequencing. The LDOs can supply 300 mA and operate with an input voltage range from 1.6 V to 6 V.
A step-down converter or main battery can power the LDOs directly. The step-down converter and the LDOs
have separate voltage inputs that enable maximum design and sequencing flexibility. The TPS6500XX device isavailable in the VQFN (16) package with body size 3 mm × 3 mm, and WQFN (20) with body size 3 mm × 3 mm.
The TPS6500XX device has several versions defined by output voltages and whether there is supply voltage
supervisor or not. In this solution, the TPS65000 version is used.

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3 x 3 mm2QFN

TPS65000/TPS65001
Oscillator
SSCG

VINDCDCSW
Buck Converter
600 mA

EN_DCDCFB_DCDC

MODE

PG

SupplyVoltage
Supervisor

MR
RSTSNS

VINLDO1

TRST
RST

VLDO1

LDO1
300 mA

EN_LDO1FB_LDO1PGND

VINLDO2

VLDO2

LDO2
300 mA

EN_LDO2FB_LDO2
AGND
Bandgap Reference

Joint Function/Pin

TPS65001 Only Function/Pin

Figure 2-13. Block Diagram of the TPS65000
As shown in Table 2-5, and compared with the specifications in Table 1-1, it can be seen that the TPS65000
solution can support powering the PYTHON 300/500/1300 and IMX25X/26X CMOS image sensors.
Table 2-5. Summary of Components in TPS65000 with Their Specifications
Component

Power Railof CMOS
Image Sensors
Supplied

Vin

Vout

LDO1

VDD_PIXEL and
OVDD

1.6 V–6 V

LDO2

VDD_33 and
AVDD

Buck

VDD_18 and
DVDD

Iout

Cout

Selected SW
Frequency

0.7 V to VINLDO- 300 mA
Vdo (Vdo=0.37 V)≥10 uF-

1.6 V–6 V

0.7 V to VINLDO- 300 mA
Vdo (Vdo=0.37 V)≥10 uF-

2.3 V–6 V

0.6 V-VinDC/DC

10 uF–22 uF

2.25 MHz (Used in
FPWM mode)

600 mA

2.3.2 Configurations of theTPS65000 Solution
As introduced in Section 2.1, the TPS65000 solution consists of the LMR36015 from the discrete solution
board, TPS65000EVM board, and LM3880EVM board to provide power supplies for PYTHON 300/500/1300 and
IMX25X/26X CMOS image sensors. The output voltage of the LMR36015 is set to 4 V. Several resistors need to
be changed according to Table 2-6 to provide certain output voltage for each rail of the CMOS image sensors.
The LM3880EVM can be configured as shown in Table 2-7 in order to provide the specific powering sequencesof each rail of the CMOS image sensors.
Table 2-6. Set Up for Required Output Voltages of the TPS65000EVM Board
CMOS Image Sensor Power Rail Of CMOS TPS65000
Image Sensors

Voltage

Top-resistor In
Corresponding
Resistor Divider
Network

Bottom-resistor
In Corresponding
Resistor Divider
NetworkPYTHON
300/500/1300

V_33

LDO2

3.3 V

162 KΩ

28.7 KΩ

V_PIXEL

LDO1

3.3 V

162 KΩ

28.7 KΩ

V_18

Buck

1.8 V

953 KΩ

470 KΩ

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Table 2-6. Set Up for Required Output Voltages of the TPS65000EVM Board (continued)
CMOS Image Sensor Power Rail Of CMOS TPS65000
Image Sensors

Voltage

Top-resistor In
Corresponding
Resistor Divider
Network

Bottom-resistor
In Corresponding
Resistor Divider
Network

IMX25X/26X

AVDD

LDO2

3.3 V

162 KΩ

28.7 KΩ

OVDD

LDO1

1.8 V

470 KΩ

180 KΩ

DVDD

Buck

1.2 V

475 KΩ

475 KΩ

Table 2-7. Connecting the LM3880EVM Board with the TPS65000EVM Board
CMOS Image Sensor

Controlled Power RailFLAG from the LM3880EVM
Board

Pin Connected in the
TPS65000EVM BoardPYTHON 300/500/1300

V_33

FLAG2

Pin 2 of JP2 (ENLDO2)

V_PIXELFLAG3

Pin 2 of JP1 (ENLDO1)

V_18

FLAG1

Pin 2 of JP6 (ENDCDC)

AVDD

FLAG3

Pin 2 of JP2 (ENLDO2)

OVDD

FLAG2

Pin 2 of JP1 (ENLDO1)

DVDD

FLAG1

Pin 2 of JP6 (ENDCDC)

IMX25X/26X

2.4 Design of TPS650330-Q1 Solution
2.4.1 Device Selection
TPS650330-Q1 Three Step-Down Converters with One High PSRR LDO Integrated Power Management IC(PMIC)The TPS650330-Q1 device is a highly integrated power management IC for automotive camera modules. This
device combines three step-down converters and one low-dropout (LDO) regulator. The BUCK1 step-down
converter has an input voltage range up to 18.3 V for connections to Power over Coax (PoC). All converters
operate in a forced fixed-frequency PWM mode. The LDO can supply 300 mA and operate with an input voltage
range from 3.0 V to 5.5 V. The step-down converters and the LDO have separate voltage inputs that enablemaximum design and sequencing flexibility. The TPS650330-Q1 is available in a 24-pin VQFN package (4.0 mm
× 4.0 mm).

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BOOTCAP
0.1 …F

4 V < VI < 18.3 V

PVIN_B1

BUCK1
3.0 V to 4.0 V
1.5 A

10 …F

LX_B1

1.5 µH

FB_B1

10 …F

PWR_PADVSYS_S

GND
Safety Power
Domain Circuits

AGND

VSYS
10 …F

VREG
Gate Drive
LDO

V1P8_INT

AGND

1 …F

REFSYS
1 …F

AGND

LX_B2

1 µH

1.8 V

PVIN_B2
BUCK2
0.9 V to 1.9 V
1200 mA

10 …F

FB_B2

10 …F

PWR_PAD

LX_B3

1 µH

1.2 V / 1.1 V

PVIN_B3
BUCK3
0.9 V to 1.9 V
1200 mA

10 …F

FB_B3

10 …F

PWR_PAD

3.3 V / 2.8 V / 2.9 V
VINLDOLDO
2.7 V to 3.3 V
300 mA

1 …F

1 …F

AGND

1 …F

nINT

SEQ

nRSTOUTSCL
2

I C and Digital Logic

SDA

GPIO
DGND
VIO

Figure 2-14. Block Diagram of the TPS650330-Q1
As shown in Table 2-8 and compared with the specifications in Table 1-1, it can be seen that the TPS650330-Q1
solution can support powering IMX25X/26X CMOS image sensors.

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Table 2-8. Summary of Components in the TPS650330-Q1 with Their Specifications
Component

Power Railof CMOS
Image Sensors
Supplied

Vin

Vout

Iout

Cout

Selected SW
Frequency

LDO

AVDD

3 V–5.5 V

2.7 V–3.3
V(Vdo=150mV–
300mV)

300 mA

1 uF–4 uF

-

Buck1

As the first power 4 V–18.3 V
stage to transform
high input voltage(12 V) from PoE
or DC adapter toa 4-V intermediate
voltage

3 V-4 V

1500 mA

6.8 uF–14 uF

2.3 MHz FPWM

Buck2

DVDD

3 V–5.5 V

0.9 V-1.9 V

1200 mA

6.8 uF–12 uF

2.3 MHz FPWM

Buck3

OVDD

3 V–5.5 V

0.9 V-1.9 V

1200 mA

6.8 uF–12 uF

2.3 MHz FPWM

2.4.2 Configurations of the TPS650330-Q1 Solution
Hardware configuration can be done according to the TPS650330-Q1EVM User’s Guide, which is available on
request at the TPS650330-Q1 product page. As shown in Figure 2-1, buck 1 in the TPS650330-Q1 is used as
the first power stage to convert the 12-V input voltage to 4-V intermediate voltage. Buck 2 in the TPS650330-Q1
is used to power 1.2 V for the digital rail, and buck 3 powers 1.8 V for the interface rail. The LDO in the
TPS650330-Q1 sets the analog rail to 3.3 V. These configurations can be set up in the TPS650330-Q1 GUI.
For powering IMX25X/26X CMOS image sensors, the power-on sequences are set to 20-ms delay time between
every power rail and the power-off sequences are set to 4-ms delay time between every power rail.

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Test Results

3 Test Results
All three solutions have been tested for power sequencing performance, efficiency, line transient and loadtransient. Besides, the 4-V intermediate voltage is adjusted to identify the relationship between the intermediate
voltage of a multi-stage system and the whole system efficiency.

3.1 Test Results of the Discrete Solution Board
3.1.1 Setup
As introduced in previous sections, the discrete solution supports power supplies of all the CMOS image sensors
listed in Table 1-1, which may require large capacitors and high current consumption up to 500 mA. Furthermore,
the discrete solution board can be configured for six cases, as shown in Table 3-1.
Table 3-1. Configurations of the Discrete Solution Board for Six Cases
CMOS Image Sensors

Case

Case Number

PYTHON 300/500/1300

LMR36015+TPS7A87+TPS7A90 1+LM3880 (30-ms delay)
LMR36015+TPS7A87+TPS6284
0+LM3880 (30-ms delay)

PYTHON 3000/5000

1.

2
2.

LMR36015+TPS7A87+TPS7A90 3+LM3880 (30-ms delay)
LMR36015+TPS7A87+TPS6284
0+LM3880 (30-ms delay)

IMX25X/26X

Configurations of Discrete
Solution Board

4

LMR36015+TPS7A87+TPS7A90 5+LM3880 (30-ms delay)
LMR36015+TPS7A87+TPS6284
1+LM3880 (30-ms delay)

1.

6
2.

Follow Table 1-1 and Table
2-4 to set up the rightvoltage for each power rail.
Put headers in J5, J6,
between pin 1 and pin 2 inJ8 for TPS7A90 or between
pin 2 and pin 3 in J8
for TPS62840, row 2 in
J_FLAG1, row 3 in J_FLAG2
and row 1 in J_FLAG3.
Follow Table 1-1 and Table
2-4 to set up the rightvoltage for each power rail.
Put headers in J5, J6,
between pin 1 and pin 2 inJ8 for TPS7A90 or between
pin 2 and pin 3 in J8
for TPS62841, row 3 in
J_FLAG1, row 2 in J_FLAG2
and row 1 in J_FLAG3.

a) Power Sequencing Test Setup
For each case shown in Table 3-1, the power sequence of each rail is tested under 12-V input voltage for thewhole system. The LM3880 is enabled by an external signal. In this test, the external signal is provided by awaveform generator. Three tip-barrel test probes are separately put in the output of each power rail in front ofloads. A current probe is used to observe the current performance of each power rail.
b) Efficiency Test Setup
In total, four sets of digital multi-meters are used. In each set, one digital multi-meter is set as current meter(AM), and another is set as voltage meter (VM). One set is placed between the DC power supply and the inputof the discrete solution board to measure input power. The other three sets are separately placed in front of three
outputs.
3.1.2 Test Results
Power sequence results are shown in Figure 3-1. According to Table 2-3, the test results of whether choosing
the TPS7A90 or the TPS6284X for digital rails are the same (case one has the same results as case two, casethree has the same results as case four, and case five has the same results as case six), so in Figure 3-1, only
the results of cases one, three, and five are presented.

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Efficiency results for the whole system are shown in Table 3-2. The table shows that if the digital rail is supplied
by a buck converter like the TPS6284X, rather than a LDO like the TPS7A90, the efficiency of the whole system
can be improved. Figure 3-2 and Figure 3-3 show the efficiency of digital rails in the whole systems. The
efficiency is calculated by the output power of the digital rail over the input power (12 Vin) of the whole system.
The fixed loads for the digital rail are removed and replaced by an electronic load here with current from 10
mA to 450 mA. In both figures, it can be seen that the efficiency is influenced by load currents. There is anintersection point in each figure. After the intersection point, the efficiency of the digital rail using the TPS6284X
increases more quickly than the efficiency of the digital rail using LDO TPS7A90.

Figure 3-1. Power Sequences of CMOS Image Sensor Power Rails
Table 3-2. Efficiency of CMOS Image Sensor Power Systems
CMOS Image Sensor

Efficiency
5 Vin

PYTHON 300/500/1300

2012 Vin24 Vin

LMR36015+TPS7A87+TP 61%
S7A90+LM3880 (30-ms
delay)

55%

50%

LMR36015+TPS7A87+TP 74%
S62840+LM3880 (30-ms
delay)

65%

53%

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Table 3-2. Efficiency of CMOS Image Sensor Power Systems (continued)
PYTHON 3000/5000

75
70
65
60
55
50
45
40
35
30
25
20
15
10
5

58%

53%

LMR36015+TPS7A87+TP 72%
S62840+LM3880 (30-ms
delay)

68%

61%

LMR36015+TPS7A87+TP 55%
S7A90+LM3880 (30-ms
delay)

43%

36%

LMR36015+TPS7A87+TP 71%
S62841+LM3880 (30-ms
delay)

62%

50%

70
60
50
Efficiency (%)

Efficiency (%)

IMX25X/26X

LMR36015+TPS7A87+TP 61%
S7A90+LM3880 (30-ms
delay)

40
30
20
10

Efficiency_TPS7A90
Efficiency_TPS62840

Efficiency_TPS7A90
Efficiency_TPS62841

0
0

0.05

0.1

0.15 0.2 0.25 0.3
Output Current (A)

0.35

0.4

0.45
D001

Figure 3-2. Efficiency of the Digital Rail Supplied
by TPS7A90 or TPS62840 in PYTHON 300/500/1300
CMOS Image Sensors

0

0.05

0.1

0.15 0.2 0.25 0.3
Output Current (A)

0.35

0.4

0.45
D002

Figure 3-3. Efficiency of the Digital Rail Supplied
by TPS7A90 or TPS62841 in IMX25X/26X CMOS
Image Sensors

3.2 Test Results of TPS65000 Solutions
Configurations of the TPS65000 solutions are described in Section 2.3.2 and the repeating testing procedurein Section 3. The test results of TPS65000 solutions are shown as follows. Figure 3-4presents the power
sequences of the power rails of the CMOS image sensors. Table 3-3 summarizes the efficiency of the wholesystem for powering the PYTHON 300/500/1300 and IMX25X/26X CMOS image sensors. The efficiency of thewhole system can be improved even more than the discrete solution according to Section 4.3.

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Figure 3-4. Power Sequences of the Power Rails of the CMOS Image Sensors Using the TPS65000
Solutions
Table 3-3. Efficiency of the Whole System Using the TPS65000 Solutions
CMOS Images Sensor

Efficiency
5 Vin

12 Vin24 VinPYTHON 300/500/1300

75%

66%

54%

IMX25X/26X

72%

63%

51%

3.3 Test Results of the TPS650330-Q1 Solutions
The following configurations of TPS650330-Q1 solutions are described in Section 2.4.2 and repeating test
procedures in Section 3. Test results of the TPS650330-Q1 solutions are shown as follows. Section 1 presents
power sequences for the power rails of IMX25X/26X CMOS image sensors. Table 3-4 summarizes the efficiencyof the whole system for powering IMX25X/26X CMOS image sensors. The efficiency of the whole system can befurther improved.

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Test Results

Figure 3-5. Power Sequences of the Power Rails of IMX25X/26X CMOS Image Sensors
Table 3-4. The Efficiency of the Whole System Using TPS650330-Q1 Solutions
Input Power of the TPS650330-Q1
AfterEnabling the Solution

Output Power of TPS650330-Q1

Efficiency

0.84 W

0.509 W61%

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4 Analysis
4.1 Power Sequence Modification of PYTHON Series CMOS Image Sensors
There is no limitation on the maximum power-up and power-off time in the datasheet of PYTHON series CMOS
Image Sensor. In order to keep the power-off sequence in a safety range, the LM3880 with longer delay time
can be used. Figure 4-1 shows the power sequences of the power rails of PYTHON 300/500/1300 CMOS image
sensors using LM3880 with 120-ms delay.

Figure 4-1. Power Sequence of the Power Rails of PYTHON 300/500/1300 CMOS Image Sensors Using the
120-ms Delay Time LM3880

4.2 Efficiency of the Whole System Influenced by Changing the Intermediate Voltage
Based on the TPS65000 solution, the 4-V intermediate voltage supplied by the LMR36015 in the discrete board
is adjusted in this section. A more suitable intermediate voltage when designing power rails can be consideredaccording to the relationship between the efficiency of the whole system and the intermediate voltage.
Considering the output voltage range of the buck, dropout voltages of the LDO, and accuracy of output voltages
in the TPS65000, the 4-V intermediate voltage powering PYTHON 300/500/1300 case is changed into 4.5 V
and 5 V to repeat efficiency tests for the whole power system. The 4-V intermediate voltage powering the
IMX25X/26X case is adjusted into 3.9 V, 4.5 V, and 5 V. Table 4-1 lists resistors values for adjusting theoutput voltages of the LMR36015 into 3.9 V, 4.5 V, and 5 V. As shown in Figure 4-2 and Figure 4-3 , theefficiency decreases when the intermediate voltage increases. The increasing intermediate voltage can improvethe efficiency of the first power stage (the LMR36015), but it causes more power dissipation on LDOs. For thissystem, power dissipation on LDOs have more impact on the whole system efficiency.
Table 4-1. Selections of Resistors for the LMR36015 to Output 3.9V, 4V, 5V and 4.5V
Output Voltage of the LMR36015

RFBT

RFBB

3.9 V

100 K

34.8 KΩ

5V

100 K

24.9 KΩ

4.5 V

100 K

28.7 KΩ

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Analysis
63

58
Efficiency@12Vin

Efficiency@12Vin

57

62

56
55
Efficiency (%)

Efficiency (%)

61
60
59

54
53
52
51

58

50
57
56
3.5

49
4

4.5
Intermediate Voltage (V)

5

48
3.5

5.5
D003

4

4.5
Intermediate Votage (V)

5

5.5
D004

Figure 4-2. The Relationship Between Efficiency of Figure 4-3. The Relationship Between Efficiency ofthe Whole System and the Intermediate Voltage
the Whole System and the Intermediate Voltage forfor Powering PYTHON 300/500/1300 CMOS Image
Powering IMX25X/26X CMOS Image Sensors
Sensors

4.3 Comparison of the Efficiency of the Discrete Solution Using the TPS62841 and the
Efficiency of the TPS65000 Solution Through Powering IMX25X/26X CMOS Image Sensors
Comparing the efficiency of the discrete solution using the TPS62841 in Table 3-2 and the efficiency of
the TPS65000 solution in Table 3-3, the second power stage of the TPS65000 solution has a better
efficiency performance than the second power stage of the discrete solution using the TPS62841 for powering
IMX25X/26X CMOS image sensors.
When disabling the dual-LDO TPS7A87 and LDOs in the TPS65000 to make only the TPS62841 and the buckin TPS65000 work, efficiencies can be tested again. The results are shown in Table 4-2. It can be identified that
TPS62841 has a better efficiency performance than the buck integrated in the TPS65000. Major losses of the
TPS62841 and the buck integrated in the TPS65000 are calculated according to the parameters in their data
sheets, as shown in Table 4-3. The losses of the TPS62841 are less than losses of the buck integrated in the
TPS65000.
However, LDOs integrated in the TPS65000 have a better quiescent operation current performance than that of
the TPS7A87, which can be observed when enabling only LDOs in both solutions. The current through GND pinof TPS7A87 is about 1 mA higher than the quiescent operation current of the TPS65000. Therefore, the total
efficiency of the TPS65000 is better than the second stage of the discrete solution board with using TPS62841,
and can be explained.
Table 4-2. Efficiency of the Discrete Solution and the TPS65000 Solution when Only Powering the Digital
Rail of IMX25X/26X CMOS Image Sensors
Efficiency of Powering Only the Digital Rail of IMX25X/26X CMOS Image Sensors
Solutions

Efficiency
4-V Intermediate Voltage (5 Vin/12 Vin/24 Vin)

Discrete solution with using TPS62841(LMR36015+TPS7A87+TS62841+LM3880)

79.5%

LMR36015 (from discrete solution board)+TPS65000EVM+LM3880EVM

79.4%

Table 4-3. TPS6284X and Buck Integrated in the Major Losses Comparison of the TPS65000
LossesTPS62841

Buck Inside the TPS65000

High-side MOSFET conduction loss

1182.7 uW

657.2 uW

Low-side MOSFET conduction loss

2545.6 uW

2758. 2uW

Conduction loss in the inductor

2872.8 uW3346.8 uW

Total losses

6.6 mW

6.8 mW

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5 Summary
CMOS image sensors usually feature three supply rails in an industrial camera, the analog rail, the PIXEL rail(or interface rail), and the digital rail. The analog rail and PIXEL rail (or interface rail) are more sensitive tonoise. So for these two rails, a LDO with high PSRR, low noise, and fast transient response are expected touse and ensure optimal image qualities. Besides, the ability of the LDO to drive high capacitance must also be
considered when powering high-performance CMOS image sensors. The digital rail is less sensitive to noise,
so in order to improve the whole system efficiency and thermal performance, the digital rail can choose a buckconverter.
The intermediate voltage of the power system is chosen as 4 V to improve the efficiency of the whole system.
CMOS image sensors can be supplied by a discrete solution using several LDOs and bucks, as well as a
PMIC solution with LDOs and bucks integrated. The number of components used in the discrete solution, thePMIC TPS65000 solution, and the PMIC TPS65033-Q1 solution are compared in Table 5-1. The TPS650330-Q1
solution benefits from less components used, so the BOM is saved just as well as in the PMIC TPS65000
solution. The discrete solution can support more conditions by selecting and modifying components flexibly. In
general, the discrete solution is more flexible, and can even achieve a smaller size than a PMIC integrated
solution, but the PMIC integrated solution can simplify the design of outside circuits. For example, the
TPS650330-Q1 integrates a sequencer into a single chip, which greatly decreases the number of components
used in the whole system. The specific choices between the discrete solution and PMIC integrated solution must
be based on a real situation.
Table 5-1. The Number of Components Used in each Solution
The Discrete Solution (PYTHON)
LMR36015+TPS7A87+TPS7A90+LM3880

LMR36015+TPS7A87+TPS62840+LM3880

DevicesNumberDevicesNumberTPS7A8701RTJR

1TPS7A8701RTJR

1TPS7A9001DSKR

1TPS62840DLCR

1LM3880MF-1AB/NOPB

1

LM3880MF-1AB/NOPB

1

LMR36015FBRNXR

1

LMR36015FBRNXR

1Capacitors

20

Capacitors

18

Resistors

15

Resistors

12

Inductors

1

Inductors

2

Total

40

Total

36

The Discrete Solution (IMX)
LMR36015+TPS7A87+TPS7A90+LM3880

LMR36015+TPS7A87+TPS62841+LM3880

DevicesNumberDevicesNumberTPS7A8701RTJR

1TPS7A8701RTJR

1TPS7A9001DSKR

1TPS62840DLCR

1LM3880MF-1AB/NOPB

1

LM3880MF-1AB/NOPB

1

LMR36015FBRNXR

1

LMR36015FBRNXR

1Capacitors

20

Capacitors

18

Resistors

15

Resistors

13

Inductors

1

Inductors

2

Total

40

Total

37

TPS65000 Solution (PYTHON and IMX)

TPS650330-Q1 Solution (IMX)

LMR36015FB EVM+ TPS65000 EVM+LM3880 EVM

TPS650330-Q1 EVM

DevicesNumberDevicesNumber

TPS65000RTE

1

TPS650330

1

LM3880MF-1AB/NOPB

1

LMR36015FBRNXR

1Capacitors

12

Capacitors

17

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References

Table 5-1. The Number of Components Used in each Solution (continued)
The Discrete Solution (PYTHON)
Resistors

13

Inductors

2

Total

35

Inductors

3

Total

16

6 References
1. Pros and Cons of Using a Feed-forward Capacitor with a Low-Dropout Regulator

7 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision * (August 2019) to Revision A (July 2021)
Page• Updated the numbering format for tables, figures and cross-references throughout the document...................3

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