VRM9.0 PROGRAMMABLE, MULTI-PHASE,

HIGH PERFORMANCE PWM CONTROLLER

SC1146

© 2000 SEMTECH CORP.

652 MITCHELL ROAD NEWBURY PARK CA 91320

July 25, 2000

4

The SC1146 is patent pending

NOTE: (1) All logic inputs and outputs are open collector TTL compatible.

PIN DESCRIPTION

Pin #

Pin Name

Pin Function

1V

CC 5V

Supply voltage input (5V nominal)

2

Divsel

Connect to Gnd for four phase operation and to logic High for three Phase

operation.

3

Clksel

Clock Select: Logic High selects internal clock. Logic Low selects external

clock.

4

Extclk

External Clock Input. The output frequency is determined by (Clock Input

Freq.)/4. Output freq.= (Clock Input)/4. Pull up to Vcc5v to select internal

clock.

5R

REF

Connects to external reference resistor. Sets the operating frequency of

the internal clock and the ramp time for the PWM. Reference voltage at

this pin is 2.05V. Trimmed to set 250µA at 8MHz.

6VID0

(1)

Programming Input (LSB)

7VID1

(1)

Programming Input

8VID2

(1)

Programming Input

9VID3

(1)

Programming Input

10

VID4

(1)

Programming Input (MSB)

11

OC+

Over current comparator. Non-Inverting input.

12

OC-

Over current comparator. Inverting input.

13

COMP

Compensation Pin. Compensation is acheived by connecting a capacitor in

series with a resistor between this pin and FBG. A 300K ohm resistor

must also be directly connected between this pin and FBG.

14

FB

Feedback input connected to supply output.

15

BG

OUT

Bandgap Reference Output. Output resistance = 3Kohm. Must be

bypassed with 4.7nF-100nF capacitor to FBG. This capacitor programs the

soft start time.

16

FBG

Feedback Ground. This pin must be connected to return side of output

caps. This pin is not internally connected to GND.

17

ENABLE

Connects to 5V to ENABLE. Connect to GND to disable entire device.

18

GND

Ground Pin

19

DRV2

Phase 2 output, output voltage range ~.3V - V

20

DRV0

Phase 0 output, output voltage range ~.3V - V

21

VCC2

Supply voltage for the DRV0-3, may be connected to +5V or +12V supply.

There is no Undervoltage Lockout on this pin.

22

DRV1

Phase 1 output, output voltage range ~.3V - V

23

DRV3

Phase 3 output, output voltage range ~.3V - V

24

PWRGOOD

Power good should be pulled-up to 5V supply via a 3K - 10K resistor.