LTC1753
5-Bit Programmable
Synchronous Switching
Regulator Controller for
Pentium® III Processor
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FEATURES
DESCRIPTIO
The LTC®1753 is a high power, high efficiency switching
regulator controller optimized for 5V input to a digitally
programmable 1.3V-3.5V output. The internal 5-bit DAC
programs the output voltage from 1.3V to 2.05V in 50mV
incrementsandfrom2.1Vto3.5Vin100mVincrements. The
precision internal reference and an internal feedback system
provide an output accuracy of ±1.5% at room temperature
and typically ±2% over temperature, load current and line
voltage shifts. The LTC1753 uses a synchronous switching
architecture with two external N-channel output devices,
providing high efficiency and eliminating the need for a high
power,highcostP-channeldevice.Additionally,itsensesthe
output current across the on-resistance of the upper N-
channel FET, providing an adjustable current limit without an
external low value sense resistor.
■
5-Bit Digitally Programmable 1.3V to 3.5V Fixed
Output Voltage, VRM 8.4 Compliant
■
Fast Transient Response: 0% to 100% Duty Cycle
■
Phase Lead Compensation for Remote Sensing
■
Overtemperature Protection
■
Flags for Power Good and Overvoltage Fault
■
19A Output Current Capability from a 5V Supply
■
Dual N-Channel MOSFET Synchronous Driver
■
Initial Output Accuracy: ±1.5%
■
Excellent Output Accuracy: ±2% Typ Over Line,
Load and Temperature Variations
High Efficiency: Over 95% Possible
■
■
Adjustable Current Limit Without External Sense
Resistors
■
Available in 2O-Lead SSOP and SW Packages
The LTC1753 free-runs at 300kHz and can be synchronized
to a faster external clock if desired. It provides a phase lead
compensation scheme and under harsh loading conditions,
the PWM duty cycle can be momentarily forced to 0% or
100% to reduce the output voltage recovery time.
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APPLICATIO S
Power Supply for Pentium® III, AMD-K6®-2, SPARC,
ALPHA and PA-RISC Microprocessors
High Power 5V to 1.3V-3.5V Regulators
■
■
, LTC and LT are registered trademarks of Linear Technology Corporation.
Pentium is a registered trademark of Intel Corporation.
AMD-K6 is a registered trademark of Advanced Micro Devices, Inc.
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TYPICAL APPLICATIO
PV
CC
12V
V
IN
5V
+
+
+
C
**
IN
0.1µF
10µF
0.1µF
10µF
1200µF
× 4
600Ω
5.6k
5.6k
Q1A*
V
†
I
CC
PV
CC
MAX
L
O
Q1*
Q2*
PWRGD
FAULT
G1
1.3µH
18A
V
OUT
20Ω
1.3V TO
3.5V
14A
I
FB
CPU
5
VID0 TO VID4
OUTEN
LTC1753
††
C
+
OUT
Q2A*
2700µF
× 5
G2
V
FB
NC
COMP
SS
SGND
GND
SENSE
R
C
15k
C1
150pF
C
SS
0.1µF
C
C
* SILICONIX SUD50N03-10
** SANYO 10MV1200GX
† PANASONIC ETQP 6FIR3LFA
†† SANYO 6MV2700GX
1µF
4700pF
1753 F01
Figure 1. 5V to 1.3V-3.5V Supply Application
1