National Semiconductor LP38691-ADJ LP38693-ADJ Specifications and User Manual
Summary
These high-reliability CMOS linear regulators provide stable, adjustable voltage (1.25V to 9V) with ultra-low dropout performance for demanding portable electronics. Engineered for wide temperature ranges and designed for stability using ceramic capacitors, they are ideal components for battery-powered devices, notebook computers, hard disk drives, and scientific instrumentation. This documentation provides comprehensive technical specifications, application circuits, power limits, and connection guides essential for system designers ensuring optimal electrical performance.
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-A /L -A ro t C in r R la to rs ith ju ta le tp t S ta le ith ra ic tp t C ito rs
October 24, 2008
LP38691-ADJ/LP38693-ADJ 500m A Low Dropout CMOS Linear Regulators with Adjustable Output Stable with Ceramic Output Capacitors General Description Features The LP38691/3-ADJ low dropout CMOS linear regulators pro- Output voltage range of 1.25V - 9V vide 2.0% precision reference voltage, extremely low dropout
2.0% adjust pin voltage accuracy (25°C)
voltage (250m V @ 500m A load current, VOUT = 5V) and ex-
Low dropout voltage: 250m V @ 500m A (typ, 5V out)
cellent AC performance utilizing ultra low ESR ceramic output
Wide input voltage range (2.7V to 10V)
capacitors.
Precision (trimmed) bandgap reference
The low thermal resistance of the LLP and SOT-223 pack-
ages allow the full operating current to be used even in high Guaranteed specs for -40°C to +125°C
ambient temperature environments. 1µA off-state quiescent current The use of a PMOS power transistor means that no DC base Thermal overload protection drive current is required to bias it allowing ground pin current
Foldback current limiting
to remain below 100 µA regardless of load current, input volt-
SOT-223 and 6-Lead LLP packages
age, or operating temperature.
Enable pin (LP38693-ADJ)
Dropout Voltage: 250 m V (typ) @ 500m A (typ. 5V out). Ground Pin Current: 55 µA (typ) at full load.
Applications
Adjust Pin Voltage: 2.0% (25°C) accuracy.
Hard Disk Drives Notebook Computers Battery Powered Devices Portable Instrumentation
Typical Application Circuits
VOUT = VADJ x (1 + R1/R2)
Note: *Minimum value required for stability.
© 2008 National Semiconductor Corporation www.national.com
Page Summary Contents For National Semiconductor LP38691-ADJ LP38693-ADJ Specifications and User Manual
Manual Details
| Brand | National |
|---|---|
| Pages | 14 |
| File Size | 335.42 KB |
| Published | June 18, 2026 |
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Frequently Asked Questions
What is the low dropout voltage?
The typical low dropout voltage is 250 mV at a 500 mA load current (for a 5V output).
How is the regulated output voltage set?
It is set by connecting the ADJ pin to external resistors R1 and R2, according to the typical application circuit formula V_OUT = V_ADJ x (1 + R1/R2).
What operating environment can these regulators handle?
They are guaranteed to operate from -40°C to +125°C junction temperature.
Are ground pin currents a concern at full load?
No, the typical ground pin current is only 55 µA at full load.