LM2688 Datasheet, PDF (1/8 Pages) National Semiconductor (TI) – Non-synchronous Step-down Controller for Pentium Microprocessors

July 1997
LM2688
Non-synchronous Step-down Controller for Pentium
Microprocessors
General Description
The LM2688 is a low-cost non-synchronous voltage-mode
PWM controller which maintains an accurate and adjustable
output voltage for high current, low voltage DC/DC applica-
tions such as the Pentium microprocessor family. By using
different combinations of feedback resistors, the regulator
output voltage can be precisely adjusted to match different
requirements. Coming in an 8-lead surface mount package,
the LM2688 can be used to control a buck regulator with an
load current up to 10A. An on-chip precision trimmed refer-
ence allows tight voltage regulation and an internal 150 kHz
fixed-frequency oscillator eliminates extra components to set
the switching frequency. The LM2688 also provides an ON/
OFF pin which enables the CPU to shutdown the regulator
when necessary. Self protection features include a two stage
current limit for the output switch and an over temperature
shutdown for complete protection under fault conditions. The
controller also provides internal loop gain compensation,
minimizing the number of external components.
Features
n Adjustable output voltage
n Available in 8-pin surface mount
n Guaranteed 0.5A gate drive current
n Supply voltage up to 40V
n 150 kHz fixed frequency internal oscillator
n TTL shutdown capability
n Low power standby mode, I_Q typically <85 µA
n Thermal shutdown and current limit protection
Applications
n Controller for voltage regulators for Pentium, Pentium
MMX, K5, K6 MMX, Alpha and PowerPC processors
n Efficient pre-regulator for linear regulators
Typical Application
Pentium Processor Power Supply
For more information about the above application, please refer to the Application Hints section.
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