UCC3588
PRELIMINARY
5-Bit Programmable Output BiCMOS Power Supply Controller
FEATURES
DESCRIPTION
• 5-Bit Digital-to-Analog Converter
(DAC) supports Intel Pentium II
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.
• 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
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%.
• Undervoltage Lockout and Softstart
Functions
• Short Circuit Protection
• Low Impedance MOSFET Drivers
• Chip Disable
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)
APPLICATION DIAGRAM
12V IN
5V IN
+
C15
150µF
C16
10µF
R1
10K
R4
3Ω
UCC3588
Q1
IRL3103
VCC
DRVHI
15
11
4
13
L1
R6
0.003Ω
+
+
+
+
1.6µH
DRVLO 14
C8-C12 1500µF
PWRGOOD
D0
VOUT
C1-C4
1500µF
C1 C2 C3 C4
R5
3Ω
D0
D1
D2
D3
D4
ISNS
2
Q2
IRL3103
D1
VSENSE
VFB
5
1
10
9
D2
6
+
+
+
+
+
+
C6
220pF
R3
200k
D3
COMP
C14
150µF
7
C8
C9
C10
C11
C12
D4
C7 22pF
8
D1 D2
SS/ENBL
GND
3
12
RT
16
R7
15k
R8
20k
C5
33nF
R2
47k
C13
1nF
RTN
RTN
UDG-98158
SLUS311 - JULY 1999
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