SC1155(2000) Ver la hoja de datos (PDF) - Semtech Corporation

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SC1155
(Rev.:2000)

PROGRAMMABLE SYNCHRONOUS DC/DC HYSTERETIC CONTROLLER WITH VRM 9.0 VID RANGE

Semtech Corporation 

PROGRAMMABLE SYNCHRONOUS

DC/DC HYSTERETIC CONTROLLER

WITH VRM 9.0 VID RANGE

SC1155

PRELIMINARY - August 7, 2000

PIN DESCRIPTION

Pin Pin Name Pin Function

1

IOUT Current Out. The output voltage on this pin is proportional to the load current as measured

across the high side MOSFET, and is approximately equal to 2 x RDS(ON) x ILOAD.

2 DROOP Droop Voltage. This pin is used to set the amount of output voltage set-point droop as a

function of load current. The voltage is set by a resistor divider between IOUT and AGND.

3

OCP Over Current Protection. This pin is used to set the trip point for over current protection by a

resistor divider between IOUT and AGND.

4 VHYST Hysteresis Set Pin. This pin is used to set the amount of hysteresis required by a resistor

divider between VREFB and AGND.

5 VREFB Buffered Reference Voltage (from VID circuitry).

6 VSENSE Output Voltage Sense.

7 AGND Small Signal Analog and Digital Ground.

8 SOFTST Soft Start. Connecting a capacitor from this pin to AGND sets the time delay.

9

NC Not connected

10 LODRV Low Drive Control. Connecting this pin to +5V enables normal operation. When LOHIB is

grounded, this pin can be used to control LOWDR.

11 LOHIB Low Side Inhibit. This pin is used to eliminate shoot-thru current.

12 DRVGND Power Ground. Insure output capacitor ground is connected to this pin.

13 LOWDR Low Side Driver Output. Connect to gate of low side MOSFET.

14

DRV Drive Regulator for the MOSFET Drivers.

15 VIN12V 12V Supply. Connect to 12V power rail.

16 BOOT Bootstrap. This pin is used to generate a floating drive for the high side FET driver.

17 HIGHDR High Side Driver Output. Connect to gate of high side MOSFET.

18 BOOTLO Bootstrap Low. In desktop applications, this pin connects to DRVGND.

19 HISENSE High Current Sense. Connected to the drain of the high side FET, or the input side of a current

sense resistor between the input and the high side FET.

20 LOSENSE Low Current Sense. Connected to the source of the high side FET, or the FET side of a current

sense resistor between the input and the high side FET.

21 IOUTLO This is the sampling capacitors bottom leg. Voltage on this pin is voltage on the LOSENSE pin

when the high side FET is on.

22 INHIBIT Inhibit. If this pin is grounded, the MOSFET drivers are disabled. Usually connected to +5V

through a pull-up resistor.

23 VID4(1) Programming Input (MSB).

24 VID3(1) Programming Input.

25 VID2(1) Programming Input.

26 VID1(1) Programming Input.

27 VID0(1) Programming Input (LSB).

28 PWRGD(1) Power Good. This open collector logic output is high if the output voltage is within 5% of the set

point.

3

© 2000 SEMTECH CORP.

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