UCC3588

PRELIMINARY

DESCRIPTION

The UCC3588 synchronous step-down (Buck) regulator provides accurate

high efficiency power conversion. Using few external components, the

UCC1588 converts 5V to an adjustable output ranging from 3.5VDC to

2.1VDC in 100mV steps and 2.05VDC to 1.3VDC in 50mV steps with 1%

DC system accuracy. A high level of integration and novel design allow this

16-pin controller to provide a complete control solution for today’s

demanding

microcontroller

power

requirements. Typical

applications

include on board or VRM based power conversion for Intel Pentium II

microprocessors,

as

well

as

other

processors

from

a

variety

of

manufacturers. High efficiency is obtained through the use of synchronous

rectification.

The softstart function provides a controlled ramp up of the system output

voltage. Overcurrent circuitry detects a hard (or soft) short on the system

output voltage and invokes a timed softstart/shutdown cycle to reduce the

PWM controller on time to 5%.

The oscillator frequency is externally programmed with RT and operates

over a range of 50kHz to 800kHz. The gate drivers are low impedance to-

tem pole output stages capable of driving large external MOSFETs. Cross

conduction is eliminated by fixed delay times between turn off and turn on

of the external high side and synchronous MOSFETs. The chip includes

undervoltage lockout circuitry which assures the correct logic states at the

outputs during power up and power down.

(continued)

5-Bit Programmable Output BiCMOS Power Supply Controller

FEATURES

• 5-Bit Digital-to-Analog Converter

(DAC) supports Intel Pentium II

• Microprocessor VID Codes

• Compatible with 5V or 12V Systems

• 1% Output Voltage Accuracy

Guaranteed

• Drives 2 N-Channel MOSFETs

• Programmable Frequency to 800kHz

• Power Good OV / UV / OVP Voltage

Monitor

• Undervoltage Lockout and Softstart

Functions

• Short Circuit Protection

• Low Impedance MOSFET Drivers

• Chip Disable

SLUS311 - JULY 1999

4

11

15

5

6

7

8

3

16

12

9

10

1

2

14

13

UCC3588

VCC

DRVHI

PWRGOOD

D0

D1

D2

D3

D4

SS/ENBL

GND

COMP

VFB

VSENSE

ISNS

DRVLO

RT

R2

47k

C5

33nF

C16

10

µF

R1

10K

C4

C3

C2

C1

++

++

RTN

D0

D1

D2

D3

D4

R3

200k

C6

220pF

C7 22pF

R7

15k

C13

1nF

R8

20k

R4

3

Ω

R5

3

Ω

R6

0.003

Ω

C15

150

µF

C12

C11

C10

C8

+

+

RTN

VOUT

L1

1.6

µH

Q2

IRL3103

Q1

IRL3103

D2

D1

12V IN

5V IN

C8-C12 1500

µF

+++

C1-C4

1500

µF

+

C14

150

µF

C9

+

APPLICATION DIAGRAM

UDG-98158