LM2720 5-Bit Programmable, High Frequency Multi-phase PWM Controller
February 2000
LM2720
5-Bit Programmable, High Frequency Multi-phase PWM
Controller
General Description
The LM2720 provides an attractive solution for power sup-
plies of high power microprocessors exhibiting ultra fast load
transients. Compared to a conventional single-phase supply,
an LM2720 based multi-phase supply distributes the thermal
and electrical loading among components in multiple phases
and greatly reduces the corresponding stress in each com-
ponent. The LM2720 can be programmed to control either a
3-phase converter or a 4-phase converter. Phase shift
among the phases is 120藲 in the case of three phase and 90藲
with four-phase. Because the power channels are out of
phase, there can be significant ripple cancellation for both
the input and output current, resulting in reduced input and
output capacitor size. Due to the nominal operating fre-
quency of 2 MHz per phase, the size of the output inductors
can be greatly reduced which results in a much faster load
transient response and a dramatically shrunk output capaci-
tor bank. Microprocessor power supplies with all surface
mount components can be easily built.
The internal high speed transconductance amplifier guaran-
tees good dynamic performance.
The internal master clock frequency of up to 8 MHz is set by
an external reference resistor. An external clock of 10 MHz
can also be used to drive the chip to achieve frequency con-
trol and multi-chip operation.
The LM2720 also provides input under-voltage lock-out with
hysteresis, input over-current protection and output voltage
power good detection.
Features
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Ultra fast load transient response
Enables all surface-mount-design
Selectable 2, 3, 4 phase operation
Clock frequency from 40 kHz to 10 MHz
Precision load current sharing
5-bit programmable from 3.5V to 1.3V
VID code compatible to VRM 8.X specification
Output voltage is 2.0V for VID code 11111
Selectable internal or external clock
Digital 16-step soft start
Input under-voltage lock-out, over-current protection
Open-drain power good signal output
Applications
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Servers and workstations
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High current, ultra-fast transient microprocessors
Pin Configuration
24-Pin Plastic SOIC
DS101322-1
Top View
See NS Package Number M24B
漏 2000 National Semiconductor Corporation
DS101322
www.national.com
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