LM2720_09 Datasheet, PDF (1/10 Pages) National Semiconductor (TI) – 5-Bit Programmable, High Frequency Multi-phase PWM Controller

LM2720
OBSOLETE
February 3, 2000
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° in the case of three phase and 90° 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 ca-
pacitor size. Due to the nominal operating frequency of 2 MHz
per phase, the size of the output inductors can be greatly re-
duced which results in a much faster load transient response
and a dramatically shrunk output capacitor bank. Micropro-
cessor 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 control
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
■ ^{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
■ ^{Servers and workstations}
■ ^{High current, ultra-fast transient microprocessors}
Pin Configuration
24-Pin Plastic SOIC
Top View
10132201
See NS Package Number M24B
© 2009 National Semiconductor Corporation 101322
101322 Version 3 Revision 1 Print Date/Time: 2009/03/26 20:37:33
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