2024年10月29日发(作者：伏凌兰)

ApplicationNote:SY8253

HighEfficiency,500kHz,3A,23VInput

SynchronousStepDownRegulator

GeneralDescription

TheSY8253isahighefficiency500kHzsynchronous

step-downDC-DCconvertercapableofdelivering3A

8253operatesoverawideinput

voltagerangefrom4.5Vto23Vandintegratesmain

switchandsynchronousswitchwithverylowR

DS(ON)

tominimizetheconductionloss.

Lowoutputvoltagerippleandsmallexternalinductor

andcapacitorsizesareachievedwith500kHz

tstheinstantPWM

architecturetoachievefasttransientresponsesforhigh

stepdownapplications

Features























lowR

DS(ON)

forinternalswitches(top/bottom):

105mΩ/50mΩ

4.5-23Vinputvoltagerange

3Aoutputcurrentcapability

500kHzswitchingfrequency

InstantPWMarchitecturetoachievefasttransient

responses.

Cycle-by-cyclepeakcurrentlimitation

Internalsoftstartlimitstheinrushcurrent

OrderingInformation

SY8253

□(□□)□

TemperatureCode

PackageCode

OptionalSpecCode

Packagetype

TSOT23-8

TSOT23-6

Note

--

--

Hic-cupmodeoutputshortcircuitprotection

±1.5%0.6Vreference

Powergoodindicator(SY8253AIConly)

TSOT23-8/TSOT23-6package

Applications











SetTopBox

PortableTV

AccessPointRouter

DSLModem

LCDTV

OrderingNumber

SY8253AIC

SY8253ADC

TypicalApplications

ticDiagram(SY8253AIC)

AN_ential-preparedforInternalUseOnly1

SY8253

ticDiagram(SY8253ADC)

AN_ential-preparedforInternalUseOnly2

SY8253

Pinout

(

topview)

BS

GND

FB

LX

IN

EN

(TSOT23-8)

PartNumber

SY8253AIC

SY8253ADC

Packagetype

TSOT23-8

TSOT23-6

(TSOT23-6)

TopMark

XUxyz

XTxyz

①

Note

①：

x=yearcode,y=weekcode,z=lotnumbercode.

Pin

Name

BS

GND

FB

SS

PG

EN

IN

LX

TSOT23-8

1

2

3

4

5

6

7

8

TSOT23-6

1

2

3

/

/

4

5

6

PinDescription

lethispintoLXpin

with0.1uFceramiccap.

Groundpin

tthispintothecenterpointoftheoutput

resistordivider(asshowninFigure1)toprogramtheoutputvoltage:

Vout=0.6*(1+R1/R2)

default1mssoft-start.

tacapacitorfromthispintoground

=Css*0.6V/4uA.

Leavethispinopenfor

ainoutput.

loat.

lethispintoGNDpinwithatleast1uFceramiccap

tthispintotheswitchingnodeofinductor

AbsoluteMaximumRatings

(Note1)

SupplyInputVoltage------------------------------------------------------------------------------------------------------------------V

BS-LX,SS-------------------------------------------------------------------------------------------------------------------------------V

Allotherpins----------------------------------------------------------------------------------------------------------------VIN+0.3V

PowerDissipation,PD@TA=25°C,TSOT23-8/TSOT23-6-----------------------------------------------------------1.5W

PackageThermalResistance(Note2)

θ

JA------------------------------------------------------------------------------------------------------------------------66°C/W

θ

JC------------------------------------------------------------------------------------------------------------------------15°C/W

JunctionTemperatureRange---------------------------------------------------------------------------------------------------150°C

LeadTemperature(Soldering,10sec.)--------------------------------------------------------------------------------------260°C

StorageTemperatureRange-----------------------------------------------------------------------------------------65°Cto150°C

RecommendedOperatingConditions

(Note3)

SupplyInputVoltage---------------------------------------------------------------------------------------------------4.5Vto23V

JunctionTemperatureRange-----------------------------------------------------------------------------------------40°Cto125°C

AmbientTemperatureRange------------------------------------------------------------------------------------------40°Cto85°C

AN_ential-preparedforInternalUseOnly3

SY8253

ElectricalCharacteristics

(V

IN

=12V,V

OUT

=3.3V,L=4.7uH,C

OUT

=47uF,T

A

=25°C,I

OUT

=1Aunlessotherwisespecified)

Parameter

InputVoltageRange

QuiescentCurrent

ShutdownCurrent

FeedbackReference

Voltage

FBInputCurrent

TopFETRON

TopFETPeakCurrent

Limit

BottomFETRON

BottomFETValley

CurrentLimit

ENRisingThreshold

ENFallingThreshold

PowerGoodThreshold

Symbol

V

IN

I

Q

I

SHDN

V

REF

I

FB

R

DS(ON)1

I

LIM,TOP

R

DS(ON)2

I

LIM,BOT

V

ENH

V

ENL

V

PG

TestConditions

I

OUT

=0

,

V

FB

=V

REF

*105%

EN=0

V

FB

=3.3V

Min

4.5

0.591

-50

5.1

3.0

1.5

Typ

100

5

0.6

105

6

50

3.7

Max

23

10

0.609

50

6.9

4.5

0.4

Unit

V

µA

µA

V

nA

mΩ

A

mΩ

A

V

V

%V

REF

%V

REF

%V

REF

%V

REF

µs

µs

µs

µs

µA

ms

ms

PowerGoodDelayTime

OutputOVPResponse

Time

OutputOVPOffTime

Soft-startCharging

Current

ShortCircuitProtection

WaitTime

ShortCircuitProtection

OffTime

InputUVLOThreshold

InputUVLOHysteresis

MinONTime

MinOFFTime

ThermalShutdown

Temperature

ThermalShutdown

Hysteresis

T

PG_F

T

PG_R

T

OVP

t

OFF,OVP

I

SS

t

WAIT,SCP

t

OFF,SCP

V

UVLO

V

HYS

T

SD

T

HYS

V

FB

falling,PGfromhightolow

V

FB

rising,PGfromlowtohigh

V

FB

rising,PGfromhightolow

V

FB

falling,PGfromlowtohigh

PGfallingedge

PGrisingedge

90

95

115

110

10

60

10

1000

4

1.9

15

0.3

80

160

150

15

4.5V

V

ns

ns

℃

℃

Note1:Stressesbeyondthe“AbsoluteMaximumRatings”re

onaloperationofthedeviceattheseoranyotherconditionsbeyondthoseindicatedinthe

retoabsolutemaximumratingconditionsfor

extendedperiodsmayaffectdevicereliability.

Note2:

θ

JAismeasuredinthenaturalconvectionatT

A

=25°Conatwo-layerSilergyEvaluationBoard.

Note3:Thedeviceisnotguaranteedtofunctionoutsideitsoperatingconditions.

AN_ential-preparedforInternalUseOnly4

SY8253

BlockDiagram

(SY8253AIC)

IN

CurrentSense

Internal

Power

Input

UVLO

4.5V

PWM

Control&

Protect

Logic

Cur

rentSense

Internal

SST

Thermal

Protection

BS

LX

EN

1.5V

FB

0.6V

GND

(SY8253ADC)

AN_ential-preparedforInternalUseOnly5

SY8253

TypicalPerformanceCharacteristics

rrent

100

90

80

70

60

50

40

30

20

10

0

110

V

IN

=7V,V

OUT

=5V

V

IN

=12V,V

OUT

=5V

V

IN

=19V,V

OUT

=5V

V

IN

=23V,V

OUT

=5V

100

90

80

70

60

50

40

30

20

10

0

110

V

IN

=5V,V

OUT

=3.3V

V

IN

=12V,V

OUT

=3.3V

V

IN

=19V,V

OUT

=3.3V

V

IN

=23V,V

OUT

=3.3V

rrent

LoadCurrent(mA)

LoadCurrent(mA)

rrent

100

90

80

70

60

50

40

30

20

10

0

110

V

IN

=5V,V

OUT

=1.2V

V

IN

=12V,V

OUT

=1.2V

V

IN

=19V,V

OUT

=1.2V

V

IN

=23V,V

OUT

=1.2V

LoadCurrent(mA)

AN_ential-preparedforInternalUseOnly6

SY8253

ShortCircuitProtection

(V

IN

=12V,V

OUT

=3.3V,0AtoShort)

ShortCircuitProtection

(V

IN

=12V,V

OUT

=3.3V,3AtoShort)

V

OUT

2V/div

V

OUT

2V/div

I

L

2A/div

I

L

2A/div

Time(10ms/div)Time(10ms/div)

AN_ential-preparedforInternalUseOnly7

SY8253

Operation

TheSY8253isahighefficiency500kHzsynchronous

step-downDC-DCconvertercapableofdelivering3A

8253operatesoverawideinput

voltagerangefrom4.5Vto23Vandintegratesmain

switchandsynchronousswitchwithverylowR

DS(ON)

tominimizetheconductionloss.

Lowoutputvoltagerippleandsmallexternalinductor

andcapacitorsizesareachievedwith500kHz

tstheinstantPWM

architecturetoachievefasttransientresponsesforhigh

stepdownapplications

OutputcapacitorC

OUT

:

Theoutputcapacitorisselectedtohandletheoutput

eadystaterippleand

transientrequirementsmustbetakenintoconsideration

bestperformance,

itisrecommendedtouseX5Rorbettergradeceramic

capacitorgreaterthan22uFcapacitance.

OutputinductorL:

Thereareseveralconsiderationsinchoosingthis

inductor.

1)Choosetheinductancetoprovidethedesired

ggestedtochoosetheripple

currenttobeabout40%ofthemaximumoutput

uctanceiscalculatedas:

L



V

OUT

(1



V

OUT

/V

IN,MAX

)

F

SW

I

OUT,MAX

40%

ApplicationsInformation

BecauseofthehighintegrationintheSY8253IC,the

applicationcircuitbasedonthisregulatorICisrather

putcapacitorC

IN

,outputcapacitorC

OUT

,

outputinductorLandfeedbackresistors(R

1

andR

2

)

needtobeselectedforthetargetedapplications

specifications.

FeedbackresistordividersR

1

andR

2

:

ChooseR

1

andR

2

toprogramtheproperoutputvoltage.

Tominimizethepowerconsumptionunderlightloads,

itisdesirabletochooselargeresistancevaluesforboth

R

1

andR

2

.Avalueofbetween10kΩand1MΩis

OUT

is3.3V,

R

1

=100kischosen,thenusingfollowingequation,R

2

canbecalculatedtobe22.1k:

V

OUT

R

1

whereFswistheswitchingfrequencyandI

OUT,MAX

is

themaximumloadcurrent.

TheSY8253regulatorICisquitetolerantofdifferent

uently,thefinalchoice

ofinductancecanbeslightlyoffthecalculationvalue

withoutsignificantlyimpactingtheperformance.

2)Thesaturationcurrentratingoftheinductormust

beselectedtobegreaterthanthepeakinductor

currentunderfullloadconditions.

I

SAT

,

MIN



I

OUT

,

MAX



3)

V

OUT

(1-V

OUT

/V

IN

,

MAX

)

2F

SW

L

R

2



V

OUT

0.6V

0.6V

R

1

.

0.6V

FB

GND

R

2

InputcapacitorC

IN

:

Theripplecurrentthroughinputcapacitoriscalculated

as：

TheDCRoftheinductorandthecorelossatthe

switchingfrequencymustbelowenoughto

desirabletochooseaninductorwithDCR<50mΩ

toachieveagoodoverallefficiency.

I

CIN_RMS

I

OUT



D(1D)

.

Tominimizethepotentialnoiseproblem,placea

typicalX5Rorbettergradeceramiccapacitorreally

ouldbetakento

minimizetheloopareaformedbyC

IN

,andIN/GNDpins.

Inthiscase,a10uFlowESRceramiccapacitoris

recommended.

ExternalBootstrapCap

Thiscapacitorprovidesthegatedrivervoltagefor

internalhighsideMOSEFET.A100nFlowESR

ceramiccapacitorconnectedbetweenBSpinandLX

pinisrecommended.

BS

CB

100nF

LX

AN_ential-preparedforInternalUseOnly

8

SY8253

LoadTransientConsiderations:

TheSY8253regulatorICintegratesthecompensation

componentstoachievegoodstabilityandfasttransient

applications,addingaceramic

capacitorinparallelwithR1mayfurtherspeedupthe

loadtransientresponsesanditisrecommendedfor

applicationswithlargeloadtransientsteprequirements.

3)ThePCBcopperareaassociatedwithLXpinmust

beminimizedtoavoidthepotentialnoiseproblem.

4)ThecomponentsR

1

andR

2

,andthetraceconnecting

totheFBpinmustNOTbeadjacenttotheLXneton

thePCBlayouttoavoidthenoiseproblem.

5)IfthesystemchipinterfacingwiththeENpinhasa

highimpedancestateatshutdownmodeandtheINpin

isconnecteddirectlytoapowersourcesuchasaLi-Ion

battery,itisdesirabletoaddapulldown1Mohm

resistorbetweentheENandGNDpinstopreventthe

noisefromfalselyturningontheregulatoratshutdown

mode.

PCBLayoutSuggestion:

Soft-Start:

TheSY8253providesprogrammablesoft-starttime

imumsoft-starttimeis1mstypically

tacapacitoracrossSS

pinandGNDtoprogramthesoft-starttime.

Tss(ms)=Css(nF)*0.6V/4uA

LayoutDesign:

ThelayoutdesignofSY8253regulatorisrelatively

bestefficiencyandminimumnoise

problem,weshouldplacethefollowingcomponents

closetotheIC:C

IN

,L,R1andR2.

1)ItisdesirabletomaximizethePCBcopperarea

connectingtoGNDpintoachievethebestthermaland

oardspaceallowed,a

groundplaneishighlydesirable.

2)C

IN

p

areaformedbyC

IN

andGNDmustbeminimized.

(SY8253AIC)

AN_ential-preparedforInternalUseOnly

9

SY8253

TSOT23-8PackageOutlineDrawing

TopviewSideviewA

SideviewB

Notes:AlldimensioninMMandexcludemoldflash&metalburr

AN_ential-preparedforInternalUseOnly10

SY8253

TSOT23-6LPackageOutlineDrawing

1.90

2.80-3.10

2

.

4

0

0.95

0.6

0

1

.

0

0

2

.

7

0

-

3

.

0

0

0.30-0.50

RecommendedPadLayout

1

.

5

0

-

1

.

7

0

1.00(max)

0.95TYP

1.90TYP

0

.

0

1

-

0

.

1

0

.

1

-

0

.

2

0

0.3-0.6

Notes:AlldimensioninMM

Alldimensiondon’tnotincludemoldflash&metalburr

AN_ential-preparedforInternalUseOnly

0

.

2

5

R

E

F

11

SY8253

Taping&ReelSpecification

orientation

TSOT23-8

Feedingdirection

TSOT23-6

Feedingdirection

rTape&Reelspecificationforpackages

AN_ential-preparedforInternalUseOnly12

SY8253

Reel

Width

Reel

Size

Package

types

TSOT23-8

TSOT23-6

Tape

width

(mm)

8

8

Pocket

pitch(mm)

4

4

Reelsize

(Inch)

7

7

Reel

width(mm)

8.4

8.4

Trailer

length(mm)

400

400

Leaderlength

(mm)

160

160

Qtyper

reel

3000

3000

:NA

AN_ential-preparedforInternalUseOnly13

2024年10月29日发(作者：伏凌兰)

ApplicationNote:SY8253

HighEfficiency,500kHz,3A,23VInput

SynchronousStepDownRegulator

GeneralDescription

TheSY8253isahighefficiency500kHzsynchronous

step-downDC-DCconvertercapableofdelivering3A

8253operatesoverawideinput

voltagerangefrom4.5Vto23Vandintegratesmain

switchandsynchronousswitchwithverylowR

DS(ON)

tominimizetheconductionloss.

Lowoutputvoltagerippleandsmallexternalinductor

andcapacitorsizesareachievedwith500kHz

tstheinstantPWM

architecturetoachievefasttransientresponsesforhigh

stepdownapplications

Features























lowR

DS(ON)

forinternalswitches(top/bottom):

105mΩ/50mΩ

4.5-23Vinputvoltagerange

3Aoutputcurrentcapability

500kHzswitchingfrequency

InstantPWMarchitecturetoachievefasttransient

responses.

Cycle-by-cyclepeakcurrentlimitation

Internalsoftstartlimitstheinrushcurrent

OrderingInformation

SY8253

□(□□)□

TemperatureCode

PackageCode

OptionalSpecCode

Packagetype

TSOT23-8

TSOT23-6

Note

--

--

Hic-cupmodeoutputshortcircuitprotection

±1.5%0.6Vreference

Powergoodindicator(SY8253AIConly)

TSOT23-8/TSOT23-6package

Applications











SetTopBox

PortableTV

AccessPointRouter

DSLModem

LCDTV

OrderingNumber

SY8253AIC

SY8253ADC

TypicalApplications

ticDiagram(SY8253AIC)

AN_ential-preparedforInternalUseOnly1

SY8253

ticDiagram(SY8253ADC)

AN_ential-preparedforInternalUseOnly2

SY8253

Pinout

(

topview)

BS

GND

FB

LX

IN

EN

(TSOT23-8)

PartNumber

SY8253AIC

SY8253ADC

Packagetype

TSOT23-8

TSOT23-6

(TSOT23-6)

TopMark

XUxyz

XTxyz

①

Note

①：

x=yearcode,y=weekcode,z=lotnumbercode.

Pin

Name

BS

GND

FB

SS

PG

EN

IN

LX

TSOT23-8

1

2

3

4

5

6

7

8

TSOT23-6

1

2

3

/

/

4

5

6

PinDescription

lethispintoLXpin

with0.1uFceramiccap.

Groundpin

tthispintothecenterpointoftheoutput

resistordivider(asshowninFigure1)toprogramtheoutputvoltage:

Vout=0.6*(1+R1/R2)

default1mssoft-start.

tacapacitorfromthispintoground

=Css*0.6V/4uA.

Leavethispinopenfor

ainoutput.

loat.

lethispintoGNDpinwithatleast1uFceramiccap

tthispintotheswitchingnodeofinductor

AbsoluteMaximumRatings

(Note1)

SupplyInputVoltage------------------------------------------------------------------------------------------------------------------V

BS-LX,SS-------------------------------------------------------------------------------------------------------------------------------V

Allotherpins----------------------------------------------------------------------------------------------------------------VIN+0.3V

PowerDissipation,PD@TA=25°C,TSOT23-8/TSOT23-6-----------------------------------------------------------1.5W

PackageThermalResistance(Note2)

θ

JA------------------------------------------------------------------------------------------------------------------------66°C/W

θ

JC------------------------------------------------------------------------------------------------------------------------15°C/W

JunctionTemperatureRange---------------------------------------------------------------------------------------------------150°C

LeadTemperature(Soldering,10sec.)--------------------------------------------------------------------------------------260°C

StorageTemperatureRange-----------------------------------------------------------------------------------------65°Cto150°C

RecommendedOperatingConditions

(Note3)

SupplyInputVoltage---------------------------------------------------------------------------------------------------4.5Vto23V

JunctionTemperatureRange-----------------------------------------------------------------------------------------40°Cto125°C

AmbientTemperatureRange------------------------------------------------------------------------------------------40°Cto85°C

AN_ential-preparedforInternalUseOnly3

SY8253

ElectricalCharacteristics

(V

IN

=12V,V

OUT

=3.3V,L=4.7uH,C

OUT

=47uF,T

A

=25°C,I

OUT

=1Aunlessotherwisespecified)

Parameter

InputVoltageRange

QuiescentCurrent

ShutdownCurrent

FeedbackReference

Voltage

FBInputCurrent

TopFETRON

TopFETPeakCurrent

Limit

BottomFETRON

BottomFETValley

CurrentLimit

ENRisingThreshold

ENFallingThreshold

PowerGoodThreshold

Symbol

V

IN

I

Q

I

SHDN

V

REF

I

FB

R

DS(ON)1

I

LIM,TOP

R

DS(ON)2

I

LIM,BOT

V

ENH

V

ENL

V

PG

TestConditions

I

OUT

=0

,

V

FB

=V

REF

*105%

EN=0

V

FB

=3.3V

Min

4.5

0.591

-50

5.1

3.0

1.5

Typ

100

5

0.6

105

6

50

3.7

Max

23

10

0.609

50

6.9

4.5

0.4

Unit

V

µA

µA

V

nA

mΩ

A

mΩ

A

V

V

%V

REF

%V

REF

%V

REF

%V

REF

µs

µs

µs

µs

µA

ms

ms

PowerGoodDelayTime

OutputOVPResponse

Time

OutputOVPOffTime

Soft-startCharging

Current

ShortCircuitProtection

WaitTime

ShortCircuitProtection

OffTime

InputUVLOThreshold

InputUVLOHysteresis

MinONTime

MinOFFTime

ThermalShutdown

Temperature

ThermalShutdown

Hysteresis

T

PG_F

T

PG_R

T

OVP

t

OFF,OVP

I

SS

t

WAIT,SCP

t

OFF,SCP

V

UVLO

V

HYS

T

SD

T

HYS

V

FB

falling,PGfromhightolow

V

FB

rising,PGfromlowtohigh

V

FB

rising,PGfromhightolow

V

FB

falling,PGfromlowtohigh

PGfallingedge

PGrisingedge

90

95

115

110

10

60

10

1000

4

1.9

15

0.3

80

160

150

15

4.5V

V

ns

ns

℃

℃

Note1:Stressesbeyondthe“AbsoluteMaximumRatings”re

onaloperationofthedeviceattheseoranyotherconditionsbeyondthoseindicatedinthe

retoabsolutemaximumratingconditionsfor

extendedperiodsmayaffectdevicereliability.

Note2:

θ

JAismeasuredinthenaturalconvectionatT

A

=25°Conatwo-layerSilergyEvaluationBoard.

Note3:Thedeviceisnotguaranteedtofunctionoutsideitsoperatingconditions.

AN_ential-preparedforInternalUseOnly4

SY8253

BlockDiagram

(SY8253AIC)

IN

CurrentSense

Internal

Power

Input

UVLO

4.5V

PWM

Control&

Protect

Logic

Cur

rentSense

Internal

SST

Thermal

Protection

BS

LX

EN

1.5V

FB

0.6V

GND

(SY8253ADC)

AN_ential-preparedforInternalUseOnly5

SY8253

TypicalPerformanceCharacteristics

rrent

100

90

80

70

60

50

40

30

20

10

0

110

V

IN

=7V,V

OUT

=5V

V

IN

=12V,V

OUT

=5V

V

IN

=19V,V

OUT

=5V

V

IN

=23V,V

OUT

=5V

100

90

80

70

60

50

40

30

20

10

0

110

V

IN

=5V,V

OUT

=3.3V

V

IN

=12V,V

OUT

=3.3V

V

IN

=19V,V

OUT

=3.3V

V

IN

=23V,V

OUT

=3.3V

rrent

LoadCurrent(mA)

LoadCurrent(mA)

rrent

100

90

80

70

60

50

40

30

20

10

0

110

V

IN

=5V,V

OUT

=1.2V

V

IN

=12V,V

OUT

=1.2V

V

IN

=19V,V

OUT

=1.2V

V

IN

=23V,V

OUT

=1.2V

LoadCurrent(mA)

AN_ential-preparedforInternalUseOnly6

SY8253

ShortCircuitProtection

(V

IN

=12V,V

OUT

=3.3V,0AtoShort)

ShortCircuitProtection

(V

IN

=12V,V

OUT

=3.3V,3AtoShort)

V

OUT

2V/div

V

OUT

2V/div

I

L

2A/div

I

L

2A/div

Time(10ms/div)Time(10ms/div)

AN_ential-preparedforInternalUseOnly7

SY8253

Operation

TheSY8253isahighefficiency500kHzsynchronous

step-downDC-DCconvertercapableofdelivering3A

8253operatesoverawideinput

voltagerangefrom4.5Vto23Vandintegratesmain

switchandsynchronousswitchwithverylowR

DS(ON)

tominimizetheconductionloss.

Lowoutputvoltagerippleandsmallexternalinductor

andcapacitorsizesareachievedwith500kHz

tstheinstantPWM

architecturetoachievefasttransientresponsesforhigh

stepdownapplications

OutputcapacitorC

OUT

:

Theoutputcapacitorisselectedtohandletheoutput

eadystaterippleand

transientrequirementsmustbetakenintoconsideration

bestperformance,

itisrecommendedtouseX5Rorbettergradeceramic

capacitorgreaterthan22uFcapacitance.

OutputinductorL:

Thereareseveralconsiderationsinchoosingthis

inductor.

1)Choosetheinductancetoprovidethedesired

ggestedtochoosetheripple

currenttobeabout40%ofthemaximumoutput

uctanceiscalculatedas:

L



V

OUT

(1



V

OUT

/V

IN,MAX

)

F

SW

I

OUT,MAX

40%

ApplicationsInformation

BecauseofthehighintegrationintheSY8253IC,the

applicationcircuitbasedonthisregulatorICisrather

putcapacitorC

IN

,outputcapacitorC

OUT

,

outputinductorLandfeedbackresistors(R

1

andR

2

)

needtobeselectedforthetargetedapplications

specifications.

FeedbackresistordividersR

1

andR

2

:

ChooseR

1

andR

2

toprogramtheproperoutputvoltage.

Tominimizethepowerconsumptionunderlightloads,

itisdesirabletochooselargeresistancevaluesforboth

R

1

andR

2

.Avalueofbetween10kΩand1MΩis

OUT

is3.3V,

R

1

=100kischosen,thenusingfollowingequation,R

2

canbecalculatedtobe22.1k:

V

OUT

R

1

whereFswistheswitchingfrequencyandI

OUT,MAX

is

themaximumloadcurrent.

TheSY8253regulatorICisquitetolerantofdifferent

uently,thefinalchoice

ofinductancecanbeslightlyoffthecalculationvalue

withoutsignificantlyimpactingtheperformance.

2)Thesaturationcurrentratingoftheinductormust

beselectedtobegreaterthanthepeakinductor

currentunderfullloadconditions.

I

SAT

,

MIN



I

OUT

,

MAX



3)

V

OUT

(1-V

OUT

/V

IN

,

MAX

)

2F

SW

L

R

2



V

OUT

0.6V

0.6V

R

1

.

0.6V

FB

GND

R

2

InputcapacitorC

IN

:

Theripplecurrentthroughinputcapacitoriscalculated

as：

TheDCRoftheinductorandthecorelossatthe

switchingfrequencymustbelowenoughto

desirabletochooseaninductorwithDCR<50mΩ

toachieveagoodoverallefficiency.

I

CIN_RMS

I

OUT



D(1D)

.

Tominimizethepotentialnoiseproblem,placea

typicalX5Rorbettergradeceramiccapacitorreally

ouldbetakento

minimizetheloopareaformedbyC

IN

,andIN/GNDpins.

Inthiscase,a10uFlowESRceramiccapacitoris

recommended.

ExternalBootstrapCap

Thiscapacitorprovidesthegatedrivervoltagefor

internalhighsideMOSEFET.A100nFlowESR

ceramiccapacitorconnectedbetweenBSpinandLX

pinisrecommended.

BS

CB

100nF

LX

AN_ential-preparedforInternalUseOnly

8

SY8253

LoadTransientConsiderations:

TheSY8253regulatorICintegratesthecompensation

componentstoachievegoodstabilityandfasttransient

applications,addingaceramic

capacitorinparallelwithR1mayfurtherspeedupthe

loadtransientresponsesanditisrecommendedfor

applicationswithlargeloadtransientsteprequirements.

3)ThePCBcopperareaassociatedwithLXpinmust

beminimizedtoavoidthepotentialnoiseproblem.

4)ThecomponentsR

1

andR

2

,andthetraceconnecting

totheFBpinmustNOTbeadjacenttotheLXneton

thePCBlayouttoavoidthenoiseproblem.

5)IfthesystemchipinterfacingwiththeENpinhasa

highimpedancestateatshutdownmodeandtheINpin

isconnecteddirectlytoapowersourcesuchasaLi-Ion

battery,itisdesirabletoaddapulldown1Mohm

resistorbetweentheENandGNDpinstopreventthe

noisefromfalselyturningontheregulatoratshutdown

mode.

PCBLayoutSuggestion:

Soft-Start:

TheSY8253providesprogrammablesoft-starttime

imumsoft-starttimeis1mstypically

tacapacitoracrossSS

pinandGNDtoprogramthesoft-starttime.

Tss(ms)=Css(nF)*0.6V/4uA

LayoutDesign:

ThelayoutdesignofSY8253regulatorisrelatively

bestefficiencyandminimumnoise

problem,weshouldplacethefollowingcomponents

closetotheIC:C

IN

,L,R1andR2.

1)ItisdesirabletomaximizethePCBcopperarea

connectingtoGNDpintoachievethebestthermaland

oardspaceallowed,a

groundplaneishighlydesirable.

2)C

IN

p

areaformedbyC

IN

andGNDmustbeminimized.

(SY8253AIC)

AN_ential-preparedforInternalUseOnly

9

SY8253

TSOT23-8PackageOutlineDrawing

TopviewSideviewA

SideviewB

Notes:AlldimensioninMMandexcludemoldflash&metalburr

AN_ential-preparedforInternalUseOnly10

SY8253

TSOT23-6LPackageOutlineDrawing

1.90

2.80-3.10

2

.

4

0

0.95

0.6

0

1

.

0

0

2

.

7

0

-

3

.

0

0

0.30-0.50

RecommendedPadLayout

1

.

5

0

-

1

.

7

0

1.00(max)

0.95TYP

1.90TYP

0

.

0

1

-

0

.

1

0

.

1

-

0

.

2

0

0.3-0.6

Notes:AlldimensioninMM

Alldimensiondon’tnotincludemoldflash&metalburr

AN_ential-preparedforInternalUseOnly

0

.

2

5

R

E

F

11

SY8253

Taping&ReelSpecification

orientation

TSOT23-8

Feedingdirection

TSOT23-6

Feedingdirection

rTape&Reelspecificationforpackages

AN_ential-preparedforInternalUseOnly12

SY8253

Reel

Width

Reel

Size

Package

types

TSOT23-8

TSOT23-6

Tape

width

(mm)

8

8

Pocket

pitch(mm)

4

4

Reelsize

(Inch)

7

7

Reel

width(mm)

8.4

8.4

Trailer

length(mm)

400

400

Leaderlength

(mm)

160

160

Qtyper

reel

3000

3000

:NA

AN_ential-preparedforInternalUseOnly13