R1 = R2

VO

1.25V

- 1

VO = VREF

R1

R2

+ 1

LP8340

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SNVS221D – FEBRUARY 2003 – REVISED APRIL 2013

OUTPUT VOLTAGE SETTING (ADJ VERSION ONLY)

The output voltage is set according to the amount of negative feedback (Note that the pass transistor inverts the

feedback signal). This feedback is determined by R1 and R2 with the resulting output voltage represented by the

following equation:

(1)

Use the following equation to determine the values of R1 and R2 for a desired VOUT (R2 = 100kΩ is

recommended).

(2)

MINIMUM LOAD CURRENT

A minimum load of 100

μA is required for regulation and stability over the entire operating temperature range. If

actual load current fall below 100

μA it is recommended that a resistor of value RL = VO/100μA be placed

between VO and ground.

START UP CONSIDERATIONS

Under certain operating conditions, overshoot of VOUT at start-up can occur. The observed overshoot is a

function of rise time of VIN waveform, COUT, start-up load current, and VIN−VOUT differential. The relationship

between these conditions is shown in the Typical Performance Characteristics curves (Minimum Input Voltage

Rise Time). VIN rise times above the curve result in <5% overshoot.

Customers are encouraged to check the suitability of LP8340 in their specific application.

Copyright © 2003–2013, Texas Instruments Incorporated

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