鈥?/div>
Chip Disable
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鈥檚
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)
APPLICATION DIAGRAM
12V IN
5V IN
+
C16
10碌F
R1
10K
UCC3588
15
+
C1
D0
D1
D2
D3
D4
+
C2
+
C3
+
C4
C1-C4
1500碌F
11
4
5
6
7
8
3
PWRGOOD DRVLO
D0
D1
D2
D3
D4
SS/ENBL
RT
16
C5
33nF
GND
12
R7
15k
R2
47k
C13
1nF
ISNS
VSENSE
VFB
COMP
14
2
1
10
9
R3
200k
C6
220pF
+
C8
+
C9
+
C10
+
C11
+
R5
3鈩?/div>
VCC
DRVHI
13
R4
3鈩?/div>
Q1
IRL3103
L1
1.6碌H
R6
0.003鈩?/div>
C15
150碌F
C8-C12 1500碌F
VOUT
Q2
IRL3103
+
C14
150碌F
C12
C7 22pF
D1
D2
R8
20k
RTN
RTN
UDG-98158
SLUS311 - JULY 1999
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