US2076

4-4

Rev. 1.3

4/26/98

TYPICAL APPLICATION

TYPICAL APPLICATION

Figure2- Typical application of US2076 in a flexible motherboard with the 4 bit VID output voltage selection. This circuit

uses a single jumper that programs the output voltage in 16 steps with 0.1V steps from 2V to 3.5V, designed for Intel P55

™,P54™,

AMD K5 & K6

™ as well as Cyrix M1™ and M2™ applications. The Vcc2Det pin automatically shuts down the I/O when a single plane

processor is dropped in the socket.

Ref Desig

Description

Qty

Part #

Manufacturer

U1

LDO/Switcher IC

1

US2076CT (TO220)

Unisem

US2076CM (TO263) (note 1)

Q1

MOSFET

1

IRL3303 (TO220)

International

IRL3103S (TO263)

(note 1)

Rectifier

D1

Schottky Diode

1

MBR1045CT (TO220)

Motorola

MBRB1545CT (TO263) (note1)

D2

Diode, GP

1

1N4148

L2

Inductor

1

Core:T50-18,L=4 uH

Micro Metal

Turns: 10T, 18 AWG

(core)

L1

Inductor

1

L=2 uH

R1

Resistor

1

22 ohm,5%, SMT 1206 size

R2

Resistor

1

10 ohm, 5%, SMT 1206 size

R4A

Resistor

1

806 ohm,1%, SMT 0805 size

R4B

Resistor

1

90.9 kohm,1%, SMT 0805 size

R5A

Resistor

1

1.24 kohm,1%, SMT 0805 size

R5B

Resistor

1

2.49 kohm,1%, SMT 0805 size

R5C

Resistor

1

4.99 kohm,1%, SMT 0805 size

R5D

Resistor

1

10 kohm,1%, SMT 0805 size

R5E

Resistor

1

1.30 kohm,1%, SMT 0805 size

R6

Resistor

1

ohm,1%, SMT 0805 size

R7

Resistor

1

ohm,1%, SMT 0805 size

R8

Resistor

1

10 kohm,5%, SMT 0805 size

C3

Capacitor

1

1 uF,Ceramic, SMT 0805 size, Z5U

C1

Capacitor

1

EEUFA1A681L, 680uF,10V, Elect

Panasonic

C4

Capacitor

1

470pF,Ceramic, SMT 0805 size

C2

Capacitor

1

6MV1500GX, 1500uF,6.3V, Elect

Sanyo

C6

Capacitor

1

EEUFA1A681L, 680uF,10V, Elect

Panasonic

C7

Capacitor

4

6MV1500GX, 1500uF,6.3V, Elect

Sanyo

HS1

Heat Sink

1

For MOSFET , 577002

Aavid

HS2

Heat Sink

1

For Schottky Diode , 577002

Aavid

HS3

Heat Sink

1

For US2076 , 507222 (I/O Load Current<5A)

Aavid

576602 (I/O Load Current< 3.5A)

Note 1: For the applications where it is desirable to eliminate the heat sink, the US2076CM for U1 when load current is

less than 1.5A, the IRL3103S for Q2 and MBR1545CT for D1 in TO263 packages with minimum of 1" square copper pad

can be used.

U1

1

2076app2-1.2

12V

5V

C1

L1

R1

Q2

D1

C3

R2

C4

C2

R5A

R5B

R5C

R5D

R5E

C7

L2

C6

R4A

Drv

V12

Vfb1

Gnd

Vfb2

Vout

Vin

1

2

3

4

5

6

7

R7

R6

2

3

4

5

6

7

8

JP1

D2

CPU

I / O

Vcc2 Det

Core

R8

5V

R4B