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Application Note: SY7088
2.3V Minimum Input and 5.5V Maximum Output
3A Peak Current Synchronous Boost with Output Disconnect
Preliminary Specification

General DescriptionFeatures

SY7088 is a high efficiency synchronous boost
regulator that converts up to 5.5V output voltage. Itadopts NMOS for the main switch and PMOS for thesynchronous switch. It can disconnect the output frominput during the shutdown mode.

Ordering Information
SY7088 □(□□□□)□□□ □Tempera ture CodePacka ge Code
Optiona l Spec Code

Ordering Number
SY7088DGC

Package typeDFN2x3-8••••••••

2.3-5.0V input voltage range
Adjustable output voltage from 2.5V to 5.5V
Pseudo-constant frequency: 1MHz
3A peak current limit
Input under voltage lockout
Load disconnect during shutdown
Output over voltage protection
Low RDS(ON) (main switch/synchronous switch)
at 5.0V output: 70/100mohm• Compact package: DFN2x3-8Applications
Note----• All Single Cell Li or Dual Cell Battery Operated
Products as MP-3 Player, PDAs, and Other
Portable Equipment.

Typical Applications

Figure 1. Schematic Diagram

AN_SY7088 Rev. 0.1A

Figure 2. Efficiency Figure1

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SY7088
Pinout (top view)(DFN2x3-8)

Top mark: VTxyz (Device code: VT, x=year code, y=week code, z= lot number code)
Name
LX
EN
SGND

DFN2x3-8
1, 234

FB5

IN

6OUT
PGND

7, 89

DescriptionInductor node. Connect an inductor between IN pin and LX pin.
Enable pin. Internal integrated with 1Mohm pull down resistor.
Signal ground pin.
Feedback pin. Connect a resistor RH between OUT and FB, and a resistor RL between
FB and GND to program the output voltage. VOUT=1.2V*(RH/RL+1).
Signal input pin. Decouple this pin to GND pin with at least 1.0uF ceramic cap fornoise immunity consideration.
Power output pin. Decouple this pin to GND pin with at least 10uF ceramic cap.
Power ground pin.

Absolute Maximum Ratings (Note 1)
EN-----------------------------------------------------------------------------------------------------------------------VOUT+0.3V
Other Pins----------------------------------------------------------------------------------------------------------------------- 6V
Power Dissipation, PD@ TA=25°C DFN2x3-8-------------------------------------------------------------------------- TBDPackage Thermal Resistance (Note 2)
θ JA ---------------------------------------------------------------------------------------------------------------- TBD
θ JC ---------------------------------------------------------------------------------------------------------------- TBD
Junction Temperature Range -------------------------------------------------------------------------------------------- 150°C
Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------------- 260°C
Storage Temperature Range ---------------------------------------------------------------------------------- -65°C to 150°C

Recommended Operating Conditions (Note 3)
IN ------------------------------------------------------------------------------------------------------------------- 2.3V to 5.25VOUT----------------------------------------------------------------------------------------------------------------- 2.5V to 5.5V
EN, FB-------------------------------------------------------------------------------------------------------- 0V to VOUT+0.3V
Junction Temperature Range -------------------------------------------------------------------------------- -40°C to 125°C
Ambient Temperature Range --------------------------------------------------------------------------------- -40°C to 85°C

AN_SY7088 Rev. 0.1A2

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SY7088
Electrical Characteristics(VIN =2.4V, VOUT=5V, IOUT=500mA, TA = 25°C unless otherwise specified)Parameter
Input Voltage
Output Voltage Range
Quiescent Current

SymbolVIN
VOUT
VIN
VOUTIQ

Shutdown Current

ISHDN

Linear charge current

ICHARGE

Soft-start time
Input Vin UVLO threshold
Vin UVLO hysteresis
EN Rising Threshold
EN Falling Threshold
Low Side Main FET RON
Synchronous FET RON
Main FET Current Limit
Feedback Reference Voltage
Minimum on time
Max on time
OUT pin OVP protection
OUT pin OVP hysteresis
Thermal Shutdown Temperature
Thermal Shutdown hysteresis

Tss
VUVLO
Vhys
VENH
VENL
RDS(ON)1RDS(ON)2
ILIM
VREF
TON_MIN
TON_MAX
VOVP
VOVP_HYS
TSD
THYS

Test Conditions

Min
2.3
2.5

Typ230
0.1
1.2
1.0
0.5

Io=0A,VEN=VIN=2.3V,
VOUT=5.0V
VEN=0V, VIN=2.4V
VOUT<1V
1V≤VOUT<VIN -0.2VMax
5.25
5.51A
2.3

0.1
1.20.4
VOUT=5.0V
VOUT=5.0V

70
100
3
1.182

1.2
100
260.2
150
20Unit
VV
µA
µA
µA

1.218

msVVVVmΩmΩ
AV
nsµs
VV℃℃

Note 1: Stresses beyond the “Absolute Maximum Ratings” may cause permanent damage to the device. These arestress ratings only. Functional operation of the device at these or any other conditions beyond those indicated in theoperational sections of the specification is not implied. Exposure to absolute maximum rating conditions may affectdevice reliability.
Note 2: θ JA is measured in the natural convection at TA = 25°C on a two-layer Silergy Evaluation Board..
Note 3: The device is not guaranteed to function outside its operating conditions.

AN_SY7088 Rev. 0.1A3

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SY7088
Typical Performance Characteristics
Load Transient

Efficiency vs. Load Current(VIN=3.3V, VOUT=5.0V, IO=0.1- 1.0A)

100

Efficiency (%)

95

∆VOUT

0.2V/div

IL1A/div

90

85

80
VIN=2.5V, VOUT=5.0V
VIN=3.3V, VOUT=5.0V
VIN=4.2V, VOUT=5.0V

757000.2

0.4

0.6

0.8

11.2

1.4

1.6

1.8

2

Time (200µs/div)

Load Current (A)Startup from Enable

Shutdown from Enable(VIN=3.3V, VOUT=5.0V, IO=1.0A)(VIN=3.3V, VOUT=5.0V, IO=1.0A)

EN

2V/divEN

2V/div

VOUT

5V/div

VOUT

5V/div

LX

5V/div

LX

5V/divIL

2A/divIL

2A/divTime (800µs/div)

Time (4ms/div)

Output Ripple

Short Circuit Protection(VIN=3.3V, VOUT=5.0V, IO=1.0A)(VIN=3.3V, VOUT=5.0V, IO=1.0A to Short)∆VOUT

0.1V/div

LX2V/div

IL

2V/divIL

1A/div

2A/divTime (1µs/div)

AN_SY7088 Rev. 0.1A

VOUTTime (20ms/div)

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SY7088
Applications Information
Because of the high integration for SY7088, only input
capacitor CIN, output capacitor COUT, inductor L andfeedback resistors (R1 and R2) need to be selected forthe targeted applications specifications.
Feedback resistor dividers R1 and R2:
Choose R1 and R2 to program the proper output voltage.
To minimize the power consumption under light loads,
it is desirable to choose large resistance values for both
R1 and R2. A value of between 10kΩ and 1MΩ isrecommended for both resistors. If VOUT is 5.0V,
R1=470kΩ is chosen, using following equation, then R2
can be calculated to be 148.4kΩ:

current to be about 40% of the maximum output
current. The inductance is calculated as:

L=((VOUT − VIN )VIN 2)
VOUT FSW × I OUT,MAX × 40%

where FSW is the switching frequency and IOUT,MAX isthe maximum load current.
The SY7088 regulator IC is quite tolerant of different
ripple current amplitude. Consequently, the final choiceof inductance can be slightly off the calculation value
without significantly impacting the performance.

VOUT

R2 =

1.2V
R1
VOUT − 1.2V

R1
1.2VFB
GND

R2Input capacitor CIN:

The ripple current through input capacitor is calculatedas:

I CIN_RMS =VIN ⋅ (VOUT − VIN )2 3 ⋅ L ⋅ FSW ⋅ VOUT

To minimize the potential noise problem, place atypical X5R or better grade ceramic capacitor reallyclose to the IN and GND pins. Care should be taken tominimize the loop area formed by CIN, and IN/GND
pins. In this case, a 22uF low ESR ceramic capacitor isrecommended.
Output capacitor COUT:
The output capacitor is selected to handle the output
ripple noise requirements. Both steady state ripple andtransient requirements must be taken into consideration
when selecting this capacitor. For the best performance,
it is recommended to use X5R or better grade ceramic
capacitor with 10V rating and greater than 22uF
capacitance.
Output inductor L:
There are several considerations in choosing thisinductor.
1) Choose the inductance to provide the desiredripple current. It is suggested to choose the ripple

AN_SY7088 Rev. 0.1A2) The saturation current rating of the inductor must
be selected to be greater than the peak inductor
current under full load conditions.

V V (VOUT − VIN )ISAT,MIN >  OUT  × IOUT, MAX + INVVOUT 2 × FSW × L
 IN 3) The DCR of the inductor and the core loss at theswitching frequency must be low enough toachieve the desired efficiency requirement. It isdesirable to choose an inductor withDCR<50mohm to achieve a good overall
efficiency.
Enable Operation
Pulling the EN pin low (<0.4V) will shut down thedevice. During shutdown mode, the SY7088 shutdown
current drops to lower than 1uA, Driving the EN pinhigh (> 1.2V) will turn on the IC again.
Layout Design:
To achieve a higher efficiency and better noise
immunity, following components should be placed
close to the IC: CSIN, COUT, L, RH and RL.
1) It is desirable to maximize the PCB copper areaconnecting to GND pin to achieve the best thermal andnoise performance. If the board space allowed, aground plane is highly desirable. PGND and SGND
pins are recommended to connect to exposed paddle
directly. Reasonable via holes are recommended to beplaced under the exposed paddle for the better
performance consideration.

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SY70882) For boost converter, the output current isdiscontinuous. So the loop area formed by COUT, OUT
and PGND must be minimized.
3) The decoupling capacitor of IN to GND CSIN must
be placed as close as possible with IN pin.

5) The components RH, RL and the trace connecting tothe FB pin must NOT be adjacent to the LX node on
the PCB layout to minimize the noise coupling to FBpin.

4) The PCB copper area associated with LX pin must
be minimized to improve the noise immunity.

PCB Layout Suggestion

AN_SY7088 Rev. 0.1A

6

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SY7088DFN2x3-8 Package Outline

Top View

Side View

Bottom View
Notes:All dimension in MM and exclude mold flash & metal burr

AN_SY7088 Rev. 0.1A