RS3235

3A, Ultra Low Dropout Linear Regulator
1 FEATURES

3 DESCRIPTIONSThe RS3235 is a 3A ultra low dropout linear regulator.
This device needs two supply voltages, one is a control
voltage (VCNTL) for the control circuitry, the other is amain supply voltage (VIN) for power conversion, toreduce power dissipation and provide extremely low
dropout voltage.

•

3A Maximum Output Current•

Low Dropout Voltage- 250mV (TYP) at 3A Output Current•

Output Voltage Accuracy: ±2%•

Adjustable Output Voltage•

Fast Transient Response•

Power-On-Reset Monitoring on Both VCNTLand VIN Pins•

Internal Soft-Start•

Current-Limit and Short Current-Limit
Protections•

Low Shutdown Quiescent Current•

Shutdown/Enable Control Function•

Temperature Protection and Over-Current

The functions of thermal shutdown and current-limit
protect the device against thermal and current overloads. A POK indicates the output voltage status with adelay time set internally. It can control other converter
for power sequence. The RS3235 can be enabled byother power systems. Pulling the EN voltage below 0.5V
shut off the output.

Protection Function•

Open-Drain VOUT Voltage Indicator•

ESOP8 and DFN3X3-10 Packages

The RS3235 integrates many functions. A Power-On
Reset (POR) circuit monitors both supply voltages on
VCNTL and VIN pins to prevent erroneous operations.

The RS3235 is available in Green ESOP8 and DFN3X310 packages. It operates over an ambient temperature
range of -40°C to +85°C.

Device Information (1)2 APPLICATIONSPARTNUMBER•

Note Book PC•

Motherboard Applications•

Front Side Bus VTT (1.2V/3A)

RS3235PACKAGEBODY SIZE (NOM)DFN3X3-10

3.00mm×3.00mm

ESOP8

4.90mm x 3.90mm(1) For all available packages, see the orderable addendum at the endof the data sheet.

4 Typical Application Circuit
VCNTL

VIN

POK

VCNTL
VIN

POK

VOUT

VOUT

Enable

EN

EN

GND

FB

Optional

REV A.2

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RS3235
Table of Contents
1 FEATURES ............................................................................................................................................................................... 1
2 APPLICATIONS ...................................................................................................................................................................... 1
3 DESCRIPTIONS ...................................................................................................................................................................... 1
4 Typical Application Circuit .................................................................................................................................................. 1
5 Revision History ..................................................................................................................................................................... 3
6 PACKAGE/ORDERING INFORMATION (1) ..................................................................................................................... 4
7 PIN Configuration and Functions (Top View) ................................................................................................................. 5
8 SPECIFICATIONS ................................................................................................................................................................... 6
8.1 Absolute Maximum Ratings .......................................................................................................................................... 6
8.2 ESD Ratings ...................................................................................................................................................................... 6
8.3 Recommended Operating Conditions ......................................................................................................................... 7
8.4 Electrical Characteristics ................................................................................................................................................ 8
8.5 Typical Characteristics .................................................................................................................................................10
9 Function Description ...........................................................................................................................................................14
9.1 Functional Block Diagram............................................................................................................................................14
9.2 Power-on-Reset.............................................................................................................................................................14
9.3 Internal Soft-Start .........................................................................................................................................................14
9.4 Output Voltage Regulation .........................................................................................................................................14
9.5 Current-Limit Protection .............................................................................................................................................14
9.6 Output Capacitor ..........................................................................................................................................................15
9.7 Short Current-Limit Protection ..................................................................................................................................15
9.8 Thermal Shutdown ........................................................................................................................................................15
9.9 Input Capacitor ..............................................................................................................................................................15
9.10 Enable Control .............................................................................................................................................................15
9.11 Power-OK and Delay .................................................................................................................................................15
9.12 Power Sequencing ......................................................................................................................................................15
9.13 Setting Output Voltage..............................................................................................................................................16
10 Layout ...................................................................................................................................................................................17
10.1 Layout Consideration .................................................................................................................................................17
10.2 Layout Example ...........................................................................................................................................................17
11 PACKAGE OUTLINE DIMENSIONS .............................................................................................................................18
12 TAPE AND REEL INFORMATION .................................................................................................................................20

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RS3235
5 Revision History
Note: Page numbers for previous revisions may different from page numbers in the current version.
VERSION

Change Date

Change Item

A.0

2023/03/02

A.1

2023/08/28

A.2

2024/03/04

Initial version completed
1. Add dropout voltage at IOUT=2A
2. Update the VIN(MIN) input voltage
1. Added MSL
2. Update Electrical Characteristics

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RS3235
6 PACKAGE/ORDERING INFORMATION (1)PRODUCT
RS3235ORDERING
NUMBER

VOUT
Accuracy

PACKAGELEAD

PACKAGEMARKING (2)MSL (3)

PACKAGE OPTION

RS3235YTDC10±2%

DFN3X3-10

RS3235

MSL3

Tape and Reel,5000

RS3235YEK

±2%

ESOP8

RS3235

MSL3

Tape and Reel,4000

NOTE:(1) This information is the most current data available for the designated devices. This data is subject to change without notice and revisionof this document. For browser-based versions of this data sheet, refer to the right-hand navigation.
(2) There may be additional marking, which relates to the lot trace code information(include data code and vendor code)，the logo or theenvironmental category on the device.
(3) MSL, The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications.

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RS3235
7 PIN Configuration and Functions (Top View)
TOP VIEWTOP VIEW
POK

1

8

GND

EN

2

7

FB

VIN

3

6

VOUT

VCNTL

4

5

NC

Thermal
Pad

VOUT

1

10

VCNTL

VOUT

2

9

VIN

VOUT

3

8

VIN

FB

4

7

VIN

POK

5

6

EN

ESOP8

GND

DFN3X3-10

PIN DESCRIPTION
NAME

PIN
DFN3X3-10

ESOP8

GND

Exposed PAD (1)

8

VOUT

1,2,3

6

VIN

7,8,9

3

EN

6

2

FB

4

7

POK

5

1

VCNTL

10

4

NC

/

5

-

/

Thermal Pad

FUNCTION
Ground pin of the circuitry.
Output pin of the regulator. Connecting this pin to load and output
capacitors (10μF at least) is required for stability and improving
transient response. The output voltage is programmed by the resistor
divider connected to FB pin. The VOUT can provide 3A (max.) load
current to loads. During shutdown, the output voltage is quickly
discharged by an internal pull-low MOSFET.
Main supply input pin for voltage conversions. A decoupling capacitor(≥10μF recommended) is usually connected near this pin to filter thevoltage noise and improve transient response. The voltage on this pin
is monitored for Power-On-Reset purpose.
Active-high enable control pin. Applying and holding the voltage on
this pin below the enable voltage threshold shuts down the output.
When re-enabled, the IC undergoes a new soft-start process. Whenleave this pin open, an internal pull-up/low current pulls the EN
voltage and enables/shuts down the regulator.
Voltage Feedback Pin. Connecting this pin to an external resistor
divider receives the feedback voltage of the regulator.
Power-OK signal output pin. This pin is an open-drain output used toindicate the status of output voltage by sensing FB voltage. This pin ispulled low when output voltage is not within the Power-OK voltage
window.
Bias voltage input pin for internal control circuitry. Connect this pin to
a voltage source (+5V recommended). A decoupling capacitor (0.1μF
typical) is usually connected near this pin to filter the voltage noise.
The voltage at this pin is monitored for Power-On-Reset purpose.
No Connection
Thermal pad (exposed center pad) to alleviate thermal stress. Tie to
GND.

(1) Connected to ground plane for better heat dissipation.

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RS3235
8 SPECIFICATIONS
8.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1)(2)
MIN

MAX

VIN

VIN Supply Voltage (VIN to GDN)

-0.3

7

VCNTL

VCNTL Supply Voltage (VCNTL to GND)

-0.3

7

VOUT

VOUT to GND Voltage

-0.3

7

POK to GND Voltage

-0.3

7

EN, FB to GND Voltage

-0.3

7

Package thermal impedance (3)θJA

DFN3X3-10

50

ESOP8

50

Lead Temperature (Soldering,10secs)
Temperature
(1)

(2)
(3)
(4)

UNIT

V

°C/W

260

Junction, TJ (4)

-40

150

Storage, Tstg

-65

150

°C

Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating
Conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltages are with respect to the GND pin.
The package thermal impedance is calculated in accordance with JESD-51.
The maximum power dissipation is a function of TJ(MAX), RθJA, and TA. The maximum allowable power dissipation at any ambient
temperature is PD = (T J(MAX) - TA) / RθJA. All numbers apply for packages soldered directly onto a PCB.

8.2 ESD Ratings
The following ESD information is provided for handling of ESD-sensitive devices in an ESD protected area only.
VALUE
V(ESD)

Electrostatic discharge

Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1)±4000

Charged-device model (CDM), per ANSI/ESDA/JEDEC JS-002(2)±1000

Machine Model (MM)

±200

UNIT
V

(1) JEDEC document JEP155 states that 500 V HBM allows safe manufacturing with a standard ESD control process.
(2) JEDEC document JEP157 states that 250 V CDM allows safe manufacturing with a standard ESD control process.

ESD SENSITIVITY CAUTION
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be
more susceptible to damage because very small parametric changes could cause the device not to meet its publishedspecifications.

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RS3235
8.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted).
MIN

MAX

UNIT

VCNTL

VCNTL Supply Voltage (VCNTL to GND)

3.0

6.0

V

VIN

VIN Supply Voltage (VIN to GND)

1.0

6.0

V

VOUT

VOUT Output Voltage (when VCNTL - VOUT >2V)

0.8

VIN - VDROPV

EN, FB, POK to GND Voltage

-0.3

6.0

V

Continuous Current

03

Peak Current

0

4

IOUT

VOUT Output Current

A

COUT

VOUT output Capacitance (1)

10

2200

uF

ESRCOUTESR of VOUT output capacitor

0

200

mΩ

TJ

Operating Junction temperature

-40

+125

°C

TA

Ambient Temperature

-40

85

°C

(1) In this data sheet, the effective value of capacitance is defined as the actual capacitance under D.C. bias and temperature; not the rated
or nameplate values.

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RS3235
8.4 Electrical Characteristics(Unless otherwise noted, the specifications apply over VCNTL=5V, VIN = 1.8V, VOUT =1.2V, TA = -40°C to +85°C, typical values
are at TA = +25°C) (1)
PARAMETERTEST CONDITIONSTEMPMIN(2)

TYP(3)

MAX(2)UNIT

105

POWER SUPPLY AND CURRENTS
ICNTL

VCNTL Supply Current

EN=HIGH, IOUT=0A,
POK=HIGH

+25°C

130

uA

Full (4)150uA

ISD_VCNTLVCNTL Supply Current at
Shutdown

EN = LOW

Full

1

uA

ISD_VIN

VIN Supply Current at
Shutdown

EN = LOW

+25°C

1

uA

EN = LOW

Full

5

uA

2.9

V

POWER-ON-RESET(POR)
Rising VCNTL POR Threshold+25°C

VCNTL POR Hysteresis+25°C

Rising VIN POR Threshold+25°C

VIN POR Hysteresis

+25°C

2.5

2.7
0.4

0.8

0.9

V
1

0.5

V
V

OUTPUT VOLTAGE
VREF

Reference Voltage

FB=VOUT+25°C

Output Voltage Accuracy

VCNTL=3.0~5.5V, IOUT= 0~3A

+25°C

Load Regulation

IOUT = 0~3A

+25°C

Line Regulation

IOUT=10mA, VCNTL=3.0~5.5V+25°C

VOUT Pull-Low Resistance

VCNTL=5V,VEN=0V,VOUT<0.8V+25°C

FB Input Current

VFB = 0.8V

+25°C

0.8
-2

V
2

10
-0.15

mV
0.15

55
-100

%
%/V
Ω

100

nA

DROPOUT VOLTAGE
VOUT=2.5V
VCNTL = 5.0V
IOUT = 2A

VDROP

VOUT=1.8V
VOUT=1.2V

VIN-to-VOUT Dropout
Voltage

VOUT=2.5V
VCNTL = 5.0V
IOUT = 3A

VOUT=1.8V
VOUT=1.2V

ILIM

+25°C

0.16

Full

0.24

+25°C

0.15

Full

0.21

+25°C

0.14

Full

0.20

+25°C

0.25

Full

0.36

+25°C

0.22

Full

0.33

+25°C

0.21

Full

0.31

+25°C

Current-Limit Level

Full

5.5
4

V
V
V
V
V
V
A

PROTECTIONSISHORTtSD

Short Current-Limit Level
Short Current-Limit Blanking
Time
Thermal Shutdown
Temperature
Thermal Shutdown Hysteresis

VFB<0.2V

+25°C

1.4

A

From beginning of soft-start

+25°C

2

ms

TJ rising

+25°C

160

°C

+25°C

50

°C

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RS3235
ENABLE AND SOFT-START
EN Logic High Threshold
Voltage
VEN
EN Logic Low Threshold
Voltage
EN Internal Pull-Low
REN_PL
ResistancetSS
tON

EN rising+25°C

EN falling

+25°C
+25°C

1.2

800

+25°C

Soft-Start Interval

VOUT = 10% to 90%

Turn On Delay

From being enable to VOUT
rising 10%+25°C

VFB rising

+25°C

Full

V

1400

0.5

V

2000

kΩ

2
1

ms
4

240

ms
us

Power-OK and DELAY
VTH_POK

Rising POK Threshold Voltage
POK Threshold Hysteresis
POK Pull-low Voltage
POK Debounce Interval
POK Delay TimePOK sink 5mA
VFB<falling POK voltage
thresholdFrom VFB=VTH_POK to risingedge of the VPOK

90

93

+25°C

8

+25°C

0.2

+25°C

10

+25°C

1

3

96

%
%

0.4

V
us

4

ms

NOTE:
(1) Electrical table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very
limited self-heating of the device.
(2) Limits are 100% production tested at 25°C. Limits over the operating temperature range are ensured through correlations using statisticalquality control (SQC) method.
(3) Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may varyover time and will also depend on the application and configuration.
(4) TJ = -40°C to +125°C.

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RS3235
8.5 Typical Characteristics
NOTE: The graphs and tables provided following this note are a statistical summary based on a limited number of samples
and are provided for informational purposes only.
VCNTL =5V, VIN = 1.8V, VOUT = 1.2V, TA = -40°C to +85°C, typical values are at TA = +25°C, unless otherwise noted.
400-40℃ VCNTL=5V
25℃ VOUT=1.2V
85℃
125℃

300

Dropout Voltage, Vdrop(mv)Dropout Voltage, Vdrop(mv)

400

200

100

0

-40℃ VCNTL=3.3V
25℃ VOUT=1.2V
85℃
125℃

300

200

100

0
0

0.5

1

1.5

2

2.5

3

0

Output Current, Iout(A)Figure 1. Dropout Voltage vs Output Current

400-40℃ VCNTL=5V
25℃ VOUT=1.8V
85℃
125℃

300

200

100

0

2

2.5

3

-40℃ VCNTL=5V
25℃ VOUT=2.5V
85℃
125℃

300

200

100

0.5

1

1.5

2

2.5

0

3

Output Current, Iout(A)Figure 3. Dropout Voltage vs Output Current

Dropout Voltage, Vdrop(mv)

200
150
100
50

1

1.5

2

2.5

3

Figure 4. Dropout Voltage vs Output Current
450

VCNTL=5V
VOUT=1.2V
IOUT=3A

0.5

Output Current, Iout(A)300

Dropout Voltage, Vdrop(mv)

1.5

0

0

250

1

Output Current, Iout(A)Figure 2. Dropout Voltage vs Output Current
Dropout Voltage, Vdrop(mv)Dropout Voltage, Vdrop(mv)

400

0.5

0

400
350

VCNTL=3.3V
VOUT=1.2V
IOUT=3A

300
250
200
150
100
50
0

-40 -25 -10 5

20 35 50 65 80 95 110 125-40 -25 -10 5

Junction Temperature(℃)

20 35 50 65 80 95 110 125

Junction Temperature(℃)

Figure 5. Dropout Voltage vs Junction
Temperature

Figure 6. Dropout Voltage vs Junction
Temperature

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RS3235
Typical Characteristics
NOTE: The graphs and tables provided following this note are a statistical summary based on a limited number of samples
and are provided for informational purposes only.
VCNTL =5V, VIN = 1.8V, VOUT = 1.2V, TA = -40°C to +85°C, typical values are at TA = +25°C, unless otherwise noted.

300
250

350

VCNTL=5V
VOUT=1.8V
IOUT=3A

Dropout Voltage, Vdrop(mv)Dropout Voltage, Vdrop(mv)

350

200
150
100
50
0

300
250
200
150
100
50
0

-40 -25 -10 5

20 35 50 65 80 95 110 125-40 -25 -10 5

Junction Temperature(℃)

Figure 8. Dropout Voltage vs Junction
TemperaturePower Supply Rejection Ratio(dB)

Reference Voltage, Vref(V)

0.81
0.805
0.8
0.795
0.79
0.785
0.78
0.775
0.77
-40 -25 -10 5

0
-10
-20
-30
-40

-60
-70

20 35 50 65 80 95 110 125

0.1

10

100

Figure 10. VIN Power Supply Rejection Ratio

0130

VCNTL=4.6-5.4V
VIN=1.8V
VOUT=1.2V
RL=10Ω
CIN=10uF
COUT=2x22uF

120
110

ICNTL(uA)Power Supply Rejection Ratio(dB)1Frequency(KHz)

Figure 9. Reference Voltage vs Junction
Temperature-30

VCNTL=5V
VIN=1.8V
VOUT=1.2V
VINPK_PK=200mV
RL=10Ω
CIN=NC
COUT=2x22uF-50

Junction Temperature (℃)-20

20 35 50 65 80 95 110 125

Junction Temperature(℃)

Figure 7. Dropout Voltage vs Junction
Temperature-10

VCNTL=5V
VOUT=2.5V
IOUT=3A-40

VIN=1.8V
VCNTL=5V
EN=5V

100
90
80

-50

70

-60

60
0.1

1

10

100

-40 -25 -10 5

20 35 50 65 80 95 110 125

Junction Temperature(℃)

Frequency(KHz)

Figure 11. VCNTL Power Supply Rejection Ratio

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Figure 12. VCNTL Current vs Junction
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RS3235
Typical Characteristics
NOTE: The graphs and tables provided following this note are a statistical summary based on a limited number of samples
and are provided for informational purposes only.
VCNTL =5V, VIN = 1.8V, VOUT = 1.2V, TA = -40°C to +85°C, typical values are at TA = +25°C, unless otherwise noted.
1.4
1.2
1

0.08

0.8

0.6
0.4
0.2

0.07
0.06

0.05
0.04
0.03
0.02

0

0.01

-0.2

0
20 35 50 65 80 95 110 125-40 -25 -10 5

Junction Temperature(℃)

IOUT

5V/div
1V/div

POK

5V/div

Figure 15. POWER ON

Figure 16. POWER OFF

VOUT

1V/divTime(50ms/div)

POK

5V/div

POK

VOUT

Time(20ms/div)

2A/div

VOUT

VIN

IOUT

2A/div

5V/div
1V/div

POK

Figure 14. VCNTL Current vs Junction
Temperature
VCNTL

5V/div 1V/div 5V/div

VOUT

5V/div

VIN

1V/div

Figure 13. VIN Current vs Junction Temperature

VCNTL

20 35 50 65 80 95 110 125

Junction Temperature(℃)

1V/div-40 -25 -10 5

EN

VIN=1.8V
VCNTL=5V
EN=0

0.09

ISD-VCNTL(uA)

ISD-VIN(uA)

0.1

VIN=1.8V
VCNTL=5V
EN=0

Time(1ms/div)

Time(5ms/div)

Figure 17. Short Circuit First, Then Turn On

Figure 18. Turn On First, Then Short Circuit

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RS3235
Typical Characteristics

5V/div

1V/div
5V/divTime(100μs/div)

Figure 19. ENABLE

Figure 20. Shutdown

VOUT

1V/div

POK

Time(5ms/div)

POK

5V/div

VOUT

IOUT

1V/div

IOUT

POK

5V/div

POK

2A/div

VOUT

5V/divEN

2A/div

VOUT

5V/divEN

1V/div

NOTE: The graphs and tables provided following this note are a statistical summary based on a limited number of samples
and are provided for informational purposes only.
VCNTL =5V, VIN = 1.8V, VOUT = 1.2V, TA = -40°C to +85°C, typical values are at TA = +25°C, unless otherwise noted.

Time(20ms/div)

Time(20ms/div)

Figure 21. Enter Over Temperature Protection

Figure 22. Exit Over Temperature Protection

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RS3235
9 Function Description
RS3235 series low dropout linear regulator (LDO) is a high performance, low dropout voltage regulator. This
device needs two supply voltages, one is a control voltage for the control circuitry, the other is a main supply
voltage for power conversion, to reduce power dissipation and provide extremely low dropout voltage.

9.1 Functional Block Diagram
VCNTL

ThermalShutdown

Turn on Enable
Delay

EN
3µ A

Power-OnReset(POR)

Control Logic
andSoft-Start

EnableEnableSoft-Start

POK

VIN

VOUT
POK
Delay
PWOK

GND

VREF_OKFB

9.2 Power-on-Reset
A Power-On-Reset (POR) circuit monitors both of supply voltages on VCNTL and VIN pins to prevent wrong
logic controls. The POR function initiates a soft-start process after both of the supply voltages exceed their rising
POR voltage thresholds during powering on. The POR function also pulls low the POK voltage regardless theoutput status when one of the supply voltages falls below its falling POR voltage threshold.

9.3 Internal Soft-Start
An internal soft-start function controls rise rate of the output voltage to limit the current surge during start-up.
The typical soft-start interval is about 2ms.

9.4 Output Voltage Regulation
An error amplifier works with a temperature-compensated 0.8V reference and an output NMOS regulates output
to the preset voltage. The error amplifier is designed with high bandwidth and DC gain provides very fasttransient response and less load regulation. It compares the reference with the feedback voltage and amplifies
the difference to drive the output NMOS which provides load current from VIN to VOUT.

9.5 Current-Limit Protection
The RS3235 monitors the current flowing through the output NMOS and limits the maximum current to prevent
load and RS3235 from damages during current overload conditions.

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RS3235
9.6 Output Capacitor
The RS3235 requires a proper output capacitor to maintain stability and improve transient response. The output
capacitor selection is dependent upon ESR (equivalent series resistance) and capacitance of the output capacitor
over the operating temperature. Ultra-low-ESR capacitors (such as ceramic chip capacitors) and low-ESR bulk
capacitors (such as solid tantalum, POSCap, and Aluminum electrolytic capacitors) can all be used as output
capacitors.
During load transients, the output capacitors, depending on the stepping amplitude and slew rate of load current,
are used to reduce the slew rate of the current seen by the RS3235 and help the device to minimize the variationsof output voltage for good transient response. For the applications with large stepping load current, the low ESR
bulk capacitors are normally recommended. Decoupling ceramic capacitors must be placed at the load andground pins as close as possible and the impedance of the layout must be minimized.

9.7 Short Current-Limit Protection
The short current-limit function reduces the current-limit level down to 1.4A (typical) when the voltage on FB
pin falls below 0.2V (typical) during current overload or short circuit conditions.
The short current-limit function is disabled for successful start-up during soft-start interval.

9.8 Thermal Shutdown
A thermal shutdown circuit limits the junction temperature of RS3235. When the junction temperature exceeds+160°C, a thermal sensor turns off the output NMOS, allowing the device to cool down. The regulator regulates
the output again through initiation of a new soft-start process after the junction temperature cools by 50°C,
resulting in a pulsed output during continuous thermal over load conditions. The thermal shutdown is designedwith a 50°C hysteresis to lower the average junction temperature during continuous thermal overload conditions,extending lifetime of the device.
For normal operation, the device power dissipation should be externally limited so that junction temperatures
will not exceed +125°C.

9.9 Input Capacitor
The RS3235 requires proper input capacitors to supply current surge during stepping load transients to preventthe input voltage rail from dropping. Because the parasitic inductor from the voltage sources or other bulk
capacitors to the VIN pin limit the slew rate of the surge currents, more parasitic inductance needs more input
capacitance. Ultra-low-ESR capacitors (such as ceramic chip capacitors) and low-ESR bulk capacitors (such as
solid tantalum, POSCap, and Aluminum electrolytic capacitors) can all be used as an input capacitor of VIN. For
most applications, the recommended input capacitance of VIN is 10μF at least.
However, if the drop of the input voltage is not cared, the input capacitance can be less than 10μF. Morecapacitance reduces the variations of the supply voltage on VIN pin.

9.10 Enable Control
The RS3235 has a dedicated enable pin (EN). A logic low signal applied to this pin shuts down the output.
Following a shutdown, a logic high signal re-enables the output through initiation of a new soft-start cycle. Whenleft open, this pin is pulled up/low by an internal current source to enable/shutdown normal operation. It’s notnecessary to use an external transistor to save cost.

9.11 Power-OK and Delay
The RS3235 indicates the status of the output voltage by monitoring the feedback voltage (V FB) on FB pin. As
the VFB rises and reaches the rising Power-OK voltage threshold (VTHPOK), an internal delay function starts towork. At the end of the delay time, the IC turns off the internal NMOS of the POK to indicate that the output is
ok. As the VFB falls and reaches the falling Power-OK voltage threshold, the IC turns on the NMOS of the POK(after a debounce time of 10μs typical).

9.12 Power Sequencing
The power sequencing of VIN and VCNTL is not necessary to be concerned. However, do not apply a voltage to
VOUT for a long time when the main voltage applied at VIN is not present. The reason is the internal parasitic
diode from VOUT to VIN conducts and dissipates power without protections due to the forward-voltage.
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RS3235
9.13 Setting Output Voltage
The output voltage is programmed by the resistor divider connected to FB pin. The preset output voltage iscalculated by the following equation:
VOUT = 0.8 x (R1+R2)/R2
Where R1 is the resistor connected from VOUT to FB with Kelvin sensing connection and R2 is the resistor
connected from FB to GND. A bypass capacitor(C1) may be connected with R1 in parallel to improve loadtransient response and stability.

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RS3235
10 Layout10.1 Layout Consideration
1.
2.
3.
4.
5.
6.
7.
8.
9.

Please solder the Exposed Pad on the ground pad on the top-layer of PCBs. The ground pad must have wide
size to conduct heat into the ambient air through the ground plane and PCB as a heat sink.
Please place the input capacitors for VIN and VCNTL pins near the pins as close as possible for decouplinghigh-frequency ripples.
Ceramic decoupling capacitors for load must be placed near the load as close as possible for decouplinghigh-frequency ripples.
To place RS3235 and output capacitors near the load reduces parasitic resistance and inductance forexcellent load transient response.
The negative pins of the input and output capacitors and the GND pin must be connected to the groundplane of the load.
Large current paths, shown by bold lines on the figure 23, must have wide tracks.
Place the R1, R2, and C1 near the RS3235 as close as possible to avoid noise coupling.
Connect the ground of the R2 to the GND pin by using a dedicated track.
Connect the one pin of the R1 to the load for Kelvin sensing.

10.2 Layout Example
VCNTL
CCNTL
CIN
VCNTL

VIN

VIN
VOUT

VOUT
COUT

C1
FB
GND

R1

Load

R2

Figure 23. Layout Example

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RS3235
11 PACKAGE OUTLINE DIMENSIONSESOP8 (4)
2.09

b

e

D1

E

5.2

E2

E1

2.09

2.2
D

1.27

0.6

RECOMMENDED LAND PATTERN (Unit: mm)

A2

c

A

A1

L

Symbolθ

Dimensions In Millimeters

Dimensions In Inches

Min

Min

Max

A (1)

Max

1.650

0.065

A1

0.050

0.150

0.002

0.006

A2

1.300

1.500

0.051

0.059

b

0.390

0.470

0.015

0.019

c

0.200

0.240

0.007

0.010

D (1)

4.800

5.000

0.189

0.197

e

1.270 (BSC) (2)0.050 (BSC) (2)D12.090 (REF) (3)0.082 (REF) (3)E22.090 (REF) (3)0.082 (REF) (3)

E

5.800

6.200

0.228

0.244

E1 (1)

3.800

4.000

0.150

0.157

L

0.500

0.800

0.019

0.032

θ

0°

8°

0°

8°

NOTE:
1. Plastic or metal protrusions of 0.15mm maximum per side are not included.
2. BSC (Basic Spacing between Centers), "Basic" spacing is nominal.
3. REF is the abbreviation for Reference.
4. This drawing is subject to change without notice.

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RS3235
DFN3X3-10 (2)
E

e

K

D

E1

L

b

N5

N1
D1

BOTTOM VIEWTOP VIEW

A1

A2

1.7

2.8

A

0.6

2.4

SIDE VIEW

0.24

0.5

RECOMMENDED LAND PATTERN (Unit: mm)

Dimensions In Millimeters

Dimensions In Inches

Min

Max

Min

Max

A (1)

0.700

0.800

0.028

0.031

A1

0.000

0.050

0.000

0.002

Symbol

A2

0.203

0.008

b

0.180

0.300

0.007

0.012

D (1)

2.900

3.100

0.114

0.122

D1

2.300

2.600

0.091

0.103

E (1)

2.900

3.100

0.114

0.122

E1

1.500

1.800

0.059

0.071

e

0.500 TYP

0.020 TYP

k

0.200 MIN

0.008 MIN

L

0.300

0.500

0.012

0.020

NOTE:
1. Plastic or metal protrusions of 0.075mm maximum per side are not included.
2. This drawing is subject to change without notice.

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RS3235
12 TAPE AND REEL INFORMATIONREEL DIMENSIONSTAPE DIMENSION

Reel
DiameterReel Width(W1)

DIRECTION OF FEEDNOTE: The picture is only for reference. Please make the object as the standard.

KEY PARAMETER LIST OF TAPE AND REELDFN3X3-10

Reel
Diameter
13’’

Reel Width
(mm)
12.4

A0
(mm)
3.35

B0
(mm)
3.35

K0
(mm)
1.13

P0
(mm)
4.0

P1
(mm)
8.0

P2
(mm)
2.0

W
(mm)
12.0

Pin1
Quadrant
Q1

ESOP8

13’’

12.4

6.40

5.40

2.10

4.0

8.0

2.0

12.0

Q1

Package TypeNOTE:
1. All dimensions are nominal.
2. Plastic or metal protrusions of 0.15mm maximum per side are not included.

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RS3235
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These resources are intended for skilled developers designing with RUNIC products You will be solely
responsible for: (1) Selecting the appropriate products for your application; (2) Designing, validating and testing
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trademarks are the property of their respective owners; (5) For change details, review the revision history
included in any revised document. The resources are subject to change without notice. Our company will not beliable for the use of this product and the infringement of patents or third-party intellectual property rights due
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