Synchronous Buck Controller
a
with Dual Linear Regulator Controllers
ADP3171
FEATURES
FUNCTIONAL BLOCK DIAGRAM
Fixed 1.2 V N-Channel Synchronous Buck Driver
Two On-Board Linear Regulator Controllers
Total Accuracy 1% over Temperature
High Efficiency Current-Mode Operation
Short Circuit Protection
Power Good Output
Overvoltage Protection Crowbar Protects Switching
Output with No Additional External Components
VCC
CT
8
SET
UVLO
AND BIAS
OSCILLATOR
DRVH
DRVL
PWM
RESET
LOGIC
CROWBAR
REF
REFERENCE
1
GND
DAC +20%
DAC –20%
APPLICATIONS
Auxiliary System Supplies for Desktop
Computer Systems
1.5V
PWRGD
3
4
LRFB1
General-Purpose Low Voltage Supplies
LRDRV1
1.8V
CS–
LRFB2
CMP
CS+
FB
7
5
LRDRV2
g
m
COMP
1.2V
ADP3171
GENERAL DESCRIPTION
The ADP3171 contains two fixed output voltage linear regulator
controllers that are designed to drive external N-channel
MOSFETs. These linear regulators are used to generate the
auxiliary voltages required in most motherboard designs and have
been designed to provide a high bandwidth load-transient response.
The ADP3171 is a highly efficient output synchronous buck
switching regulator controller optimized for converting a 5 V
main supply into the auxiliary supply voltages required by
processors and chipsets. The ADP3171 provides a fixed
output voltage of 1.2 V at up to 15 A, depending on the
power ratings of the external MOSFETs and inductor. The
ADP3171 uses a current-mode, constant off time architecture to
drive two N-channel MOSFETs at a programmable switching
frequency that can be optimized for regulator size and efficiency.
The ADP3171 is specified over the commercial temperature
range of 0°C to 70°C and is available in a 14-lead SOIC package.
The ADP3171 provides accurate and reliable short circuit
protection and adjustable current limiting. It also includes an
integrated overvoltage crowbar function to protect the load in
case the output voltage exceeds the nominal programmed
voltage by more than 20%.
REV. 0
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© Analog Devices, Inc., 2002