IR3521 datasheet(4/45 Pages) IRF

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IR3521

Page 4

V3.03

PIN#

SYMBOL

PIN DESCRIPTION

SS/DEL1

Programs output 1 startup and over current protection delay timing. Connect an

external capacitor to LGND to program.

IIN1

Output 1 average current input from the output 1 phase IC(s). This pin is also used

to communicate over voltage condition to phase ICs.

VDRP1

Output 1 Buffered IIN1 signal. Connect an external RC network to FB1 to program

converter output impedance.

ROSC/OVP

Connect a resistor to LGND to program oscillator frequency and OCSET1, OCSET2,

FB1, FB2, VDAC1, and VDAC2 bias currents. Oscillator frequency equals switching

frequency per phase. The pin voltage is 0.6V during normal operation and higher

than 1.6V if over-voltage condition is detected.

PSI_L

Digital output to communicate the systems power state to phase ICs PSI_L pin.

CLKOUT

Clock output at switching frequency multiplied by phase number. Connect to CLKIN

pins of phase ICs.

PHSOUT

Phase clock output at switching frequency per phase. Connect to PHSIN pin of the

first phase IC.

PHSIN

Feedback input of phase clock. Connect to PHSOUT pin of the last phase IC.

VCCL

Output of the voltage regulator, and power input for clock oscillator circuitry. Connect

a decoupling capacitor to LGND. No external power rail connection is allowed.

VCCLFB

Non-inverting input of the voltage regulator error amplifier. Output voltage of the

regulator is programmed by the resistor divider connected to VCCL.

VCCLDRV

Output of the VCCL regulator error amplifier to control external transistor. The pin

senses 12V power supply through a resistor.

PGOOD

Open collector output that drives low during startup and under any external fault

condition. And it monitors output voltages, if any of the voltage planes fall out of

spec, it will drive low. Connect external pull-up. ( Output voltage out of spec is

defined as 350mV to 240mV below VDAC voltage )

SVC

SVC (Serial VID Clock) is an open drain output of the processor and input to

IR3521, requires an external bias voltage and should not be floated

EPAD

LGND

Local ground for internal circuitry and IC substrate connection.

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