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FN6899.0

December 22, 2009

ISL95870A Functional Pin Descriptions

PIN NUMBER SYMBOL

DESCRIPTION

1

LGATE

Low-side MOSFET gate driver output. Connect to the gate terminal of the low-side MOSFET of the

converter.

2

PGND

Return current path for the LGATE MOSFET driver. Connect to the source of the low-side MOSFET.

3

GND

IC ground for bias supply and signal reference.

4

RTN

5

VID1

Logic input for setpoint voltage selector. Use in conjunction with the VID0 pin to select among four

setpoint reference voltages.

6

VID0

Logic input for setpoint voltage selector. Use in conjunction with the VID1 pin to select among four

setpoint reference voltages.

7

SREF

Soft-start and voltage slew-rate programming capacitor input and setpoint reference voltage

amplifier.

8

SET0

Voltage set-point programming resistor input.

9

SET1

Voltage set-point programming resistor input.

10

FB

Voltage feedback sense input. Connects internally to the inverting input of the control-loop error

transconductance amplifier. The converter is in regulation when the voltage at the FB pin equals the

voltage on the SREF pin.

11

OCSET

connects from this pin to the sense node.

12

VO

the overcurrent detection circuit.

13

FSEL

Input for programming the regulator switching frequency. Pull this pin to VCC for 1MHz switching.

Pull this pin to GND with a 100kΩ resistor for 600kHz switching. Leave this pin floating for 500kHz

switching. Pull this pin directly to GND for 300kHz switching.

14

PGOOD

Power-good open-drain indicator output. This pin changes to high impedance when the converter is

able to supply regulated voltage.

15

EN

Enable input for the IC. Pulling EN above the rising threshold voltage initializes the soft-start

sequence.

16

PHASE

and inductor current polarity detector input.

17

UGATE

High-side MOSFET gate driver output. Connect to the gate terminal of the high-side MOSFET of the

converter.

18

BOOT

Positive input supply for the UGATE high-side MOSFET gate driver. The BOOT pin is internally

connected to the cathode of the Schottky boot-strap diode. Connect an MLCC between the BOOT pin

and the PHASE pin.

19

VCC

Input for the IC bias voltage. Connect +5V to the VCC pin and decouple with at least a MLCC to the

GND pin.

20

PVCC

Input for the LGATE and UGATE MOSFET driver circuits. The PVCC pin is internally connected to the

anode of the Schottky boot-strap diode. Connect +5V to the PVCC pin and decouple with a MLCC to

the PGND pin.

ISL95870, ISL95870A, ISL95870B