IR3637SPBF

3

Rev. 1.1

06/16/05

www.irf.com

PARAMETER

SYM

TEST CONDITION

MIN

TYP

MAX

UNITS

PIN DESCRIPTIONS

This pin is connected directly to the output of the switching regulator via resistor divider to

set the output voltage and provide feedback to the error amplifier.

This pin provides biasing for the internal blocks of the IC as well as powers the low side

driver. A minimum of 0.1

µF, high frequency capacitor must be connected from this pin to

ground to provide peak drive current capability.

Output driver for the synchronous power MOSFET.

IC's ground pin. This pin must be connected directly to the ground plane. A high frequency

capacitor (0.1 to 1

µF) must be connected from Vcc and Vc pins to this pin for noise free

operation.

Output driver for the high side power MOSFET. The negative voltage at this pin may cause

instability for the gate drive circuit. To prevent this, a low forward voltage drop diode (e.g.

BAT54 or 1N4148) is required between this pin and ground.

This pin is connected to a voltage that must be at least 4V higher than the bus voltage

(assuming 5V threshold MOSFET) and powers the high side output driver. A minimum of

0.1

µF, high frequency capacitor must be connected from this pin to ground to provide

peak drive current capability.

Compensation pin of the error amplifier. An external resistor and capacitor network is

typically connected from this pin to ground to provide loop compensation.

This pin provides user programmable soft-start function. Connect an extrnal capacitor

from this pin to ground to set the start up time of the output. The converter can be shut-

down by pulling this pin below 0.4V. During shutdown the upper FET is turned off and the

lower FET is turned on.

Error Amp

Fb Voltage Input Bias Current

Fb Voltage Input Bias Current

Transconductance

Oscillator

Frequency

Ramp-Amplitude Voltage

Output Drivers

Rise Time, Hdrv, Ldrv

Fall Time,Hdrv, Ldrv

Dead Band Time

Max Duty Cycle

Min Duty Cycle

SS=3V, Fb=0.6V

SS=0V, Fb=0.6V

Vcc=12V, 2V to 2V

Fb=0.6V, Freq=400kHz

Fb=1V

450

360

40

81

-0.1

-64

600

400

1.25

30

30

150

85

800

440

60

60

200

0

µA

µA

µmho

kHz

V

ns

ns

ns

%

%

PIN#

PIN SYMBOL

PIN DESCRIPTION

1

2

3

4

5

6

7

8

Fb

Vcc

LDrv

Gnd

HDrv

Vc

Comp

SS / SD

Freq