Name: ERJ-3EKF1000V
SKU: ERJ-3EKF1000V

- 31 -`

AUGUST08,2012|DATASHEET| Rev3.1

IR3894

12AHighlyIntegratedSupIRBuck

Single‐InputVoltage,SynchronousBuckRegulator

PD‐97745

Thesmallsignalvaluemaybeobtainedfromthe

manufacturer’sdatasheets,designtoolsorspicemodels.

Alternatively,theymayalsobeinferredfrommeasuringthe

powerstagetransferfunctionoftheconverterandmeasuring

thedoublepolefrequencyf

andusingequation(17)

tocomputethesmallsignalc

.

Theseresultto:

=24.9kHz

ESR

=5.3MHz

/2=300kHz

SelectcrossoverfrequencyF

=100kHz

SinceF

<Fs/2<F

ESR

,TypeIIIisselectedtoplacethe

poleandzeros.

DetailedcalculationofcompensationTypeIII:

DesiredPhaseBoostΘ=70°

1sin

17.6 kHz

1sin









1sin

567.1 kHz

1sin









Select:

0.5* 8.8 kHz and

FF 



0.5* 300 kHz

FF



SelectC

=2.2nF.

CalculateR

,C

andC

:

2* * * *

;1.75 kΩ

oo oosc

FLCV







SelectR

=1.82kΩ:

33 3

; 9.9 nF, Select: 10 nF

2* *

CC C



 



22 2

; 354 pF, Select: 220 pF

2* *

CC C



 



CalculateR

,R

andR

:

44 4

; 127 Ω, Select: 100 Ω

2* *

RR R



 



545

-; 4.1 kΩ,

2* *

RRR







SelectR

=4.02kΩ:

656 6

* ; 2.87 kΩ Select: 2.87 kΩ

ref

oref

RRR R

 



SettingthePowerGoodThreshold

InthisdesignIR3894isusedinnormal(non‐tracking,

non‐sequencing)mode,thereforethePGoodthresholdsare

internallysetat90%and120%ofVref.Atstartupassoonas

Vsnsvoltagereaches0.9*0.5V=0.45V(Fig.15),andafter

1.28msdelay,PGoodsignalisasserted.

AslongastheVsns

voltageisbetweenthethresholdrange,Enableishigh,andno

faulthappens,thePGoodremainshigh.

ThefollowingformulacanbeusedtosetthePGood

threshold.V

out(PGood

_TH

)

canbetakenas90%ofVout.Choose

R8=2.87KΩ.

(_)

7( 1)*8 (34)

0.9*

74.02

out PGood TH

Vref









ThePGoodisanopendrainoutput.Hence,itisnecessaryto

useapullupresistor,R

,fromPGoodpintoVcc.Thevalue

ofthepull‐upresistormustbechosensuchastolimitthe

currentflowingintothePGoodpintobelessthan5mAwhen

theoutputvoltageisnotinregulation.Atypicalvalueused

is49.9kΩ.

OVPcomparatoralsouses

VsnssignalforoverVoltage

dectection.WithabovevaluesforR7andR8,OVPtrippoint

(Vout_

OVP)

is

*1.2*( 7 8)/ 8 1.44 (35)OVPVout Vref R R R V







VrefBypassCapacitor

Aminimumvalueof100pFbypasscapacitorisrecommended

tobeplacedbetweenVrefandGndpins.Thiscapacitorshould

beplacedascloseaspossibletoVrefpin.

- 32 -`

AUGUST08,2012|DATASHEET| Rev3.1

IR3894

12AHighlyIntegratedSupIRBuck

Single‐InputVoltage,SynchronousBuckRegulator

PD‐97745

APPLICATIONDIAGRAM



Figure28:ApplicationCircuitfora12Vto1.2V,12APointofLoadConverter



Suggestedbillofmaterialsfortheapplicationcircuit



Part

Reference Qty Value Description Manufacturer Part Number

Cin

1 330uF

SMD Electrolytic F size 25V

20%

Panasonic

EEV-FK1E331P

4 10uF

1206, 25V, X5R, 20%

TDK C3216X5R1E106M

C1 C5 C6 3 0.1uF 0603, 25V, X7R, 10% Murata GRM188R71E104KA01B

Cref 1 1nF

0603, 25V, COG, 5%

Murata GRM1885C1E102JA01D

C4 1 2200pF 0603,50V,X7R Murata GRM188R71H222KA01B

C2 1 220pF

0603, 50V, NP0, 5% Murata GRM1885C1H221JA01D

Co 8 22uF

0805, 6.3V, X5R, 20%

TDK C2012X5R0J226M

CVcc 1 2.2uF

0603, 16V, X5R, 20%

TDK C1608X5R1C225M

C3 1 10nF

0603, 25V, X7R, 10%

Murata GRM188R71E103KA01J

Cvin 1 1.0uF

0603, 25V, X5R, 10%

Murata GRM188R61E105KA12D

Lo 1 0.51uH SMD 11.0x7.2x7.5mm, 0.29mΩ Vitec 59PR9876N

R3 1 1.82K

Thick Film, 0603,1/10W,1%

Panasonic ERJ-3EKF1821V

R5 R7 2 4.02K

Thick Film, 0603,1/10W,1%

Panasonic ERJ-3EKF4021V

R6 R8 2 2.87K

Thick Film, 0603,1/10W,1%

Panasonic ERJ-3EKF2871V

R4 1 100

Thick Film, 0603,1/10W,1%

Panasonic ERJ-3EKF1000V

Rt 1 39.2K

Thick Film, 0603,1/10W,1%

Panasonic ERJ-3EKF3922V

R1 Rpg 2 49.9K

Thick Film, 0603,1/10W,1%

Panasonic ERJ-3EKF4992V

R2 1 7.5K

Thick Film, 0603,1/10W,1%

Panasonic ERJ-3EKF7551V

U1 1 IR3894 PQFN 5x6mm IR IR3894MPBF



- 33 -`

AUGUST08,2012|DATASHEET| Rev3.1

IR3894

12AHighlyIntegratedSupIRBuck

Single‐InputVoltage,SynchronousBuckRegulator

PD‐97745

Figure29:ApplicationCircuitfora5Vto1V,12APointofLoadConverter

Suggestedbillofmaterialsfortheapplicationcircuit

Part

Reference Qty Value Description Manufacturer Part Number

Cin

1 330uF

SMD Electrolytic F size 25V

20%

Panasonic

EEV-FK1E331P

6 10uF

1206, 25V, X5R, 20%

TDK C3216X5R1E106M

C1 C5 C6 3 0.1uF 0603, 25V, X7R, 10% Murata GRM188R71E104KA01B

Cref 1 1nF

0603, 25V, COG, 5%

Murata GRM1885C1E102JA01D

C4 1 2200pF 0603,50V,X7R Murata GRM188R71H222KA01B

C2 1 91pF

0603, 50V, NP0, 5% TDK C1608C0G1H910J

Co 4 47uF

0805, 6.3V, X5R, 20%

TDK C2012X5R0J476M

CVcc 1 2.2uF

0603, 16V, X5R, 20%

TDK C1608X5R1C225M

C3 1 6.8nF

0603, 25V, X7R, 10%

Murata GRM188R71H682KA01D

Cvin 1 1.0uF

0603, 25V, X5R, 10%

Murata GRM188R61E105KA12D

Lo 1 0.4uH SMD 11.0x7.2x7.5mm, 0.29mΩ Vitec 59PR9875N

R3 1 2K

Thick Film, 0603,1/10W,1%

Panasonic ERJ-3GEYJ202V

R5 R6 R7

R8 4 3.32k

Thick Film, 0603,1/10W,1%

Panasonic ERJ-3EKF3321V

R4 1 100

Thick Film, 0603,1/10W,1%

Panasonic ERJ-3EKF1000V

Rt 1 39.2K

Thick Film, 0603,1/10W,1%

Panasonic ERJ-3EKF3922V

Rpg 1 49.9K

Thick Film, 0603,1/10W,1%

Panasonic ERJ-3EKF4992V

U1 1 IR3894 PQFN 5x6mm IR IR3894MPBF



Part #	ERJ-3EKF1000V
Description	RES THKFLM 0603 100 OHM 1% 1/10W 100PPM/ C SMD - Cut TR (S
Category	CHIP RESISTOR
Availability	Out of Stock
Qty	0

ERJ-3EKF1000V

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