3

LM2591HV

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SNVS074E – MAY 2001 – REVISED MAY 2016

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Copyright © 2001–2016, Texas Instruments Incorporated

5 Description (continued)

Other features include a specified ±4% tolerance on output voltage under all conditions of input voltage and

output load conditions, and ±15% on the oscillator frequency. External shutdown is included, featuring typically

90-

μA standby current. Self-protection features include a two stage current limit for the output switch and an over

temperature shutdown for complete protection under fault conditions.

6 Pin Configuration and Functions

KTT Package

5-Pin DDPAK/TO-26

Top View

NDH Package

5-Pin TO-220

Top View

Pin Functions

PIN

I/O

DESCRIPTION

NO.

NAME

1

I

This is the positive input supply for the IC switching regulator. A suitable input bypass

capacitor must be present at this pin to minimize voltage transients and to supply the

switching currents needed by the regulator.

2

Output

O

approximately

3

Ground

—

Circuit ground.

4

Feedback

I

Senses the regulated output voltage to complete the feedback loop. This pin is directly

connected to the Output for the fixed voltage versions, but is set to 1.23 V by means of a

resistive divider from the output for the Adjustable version. If a feedforward capacitor is used

(Adjustable version), then a negative voltage spike is generated on this pin whenever the

output is shorted. This happens because the feedforward capacitor cannot discharge fast

enough, and because one end of it is dragged to Ground, the other end goes momentarily

negative. To prevent the energy rating of this pin from being exceeded, a small-signal

Schottky diode to Ground is recommended for DC input voltages above 40 V whenever a

feedforward capacitor is present (See Test Circuits). Feedforward capacitor values larger

than 0.1

μF are not recommended for the same reason, whatever be the DC input voltage.

5

ON/OFF

I

The regulator is in shutdown mode, drawing about 90

μA, when this pin is driven to a high

level (

≥ 2 V), and is in normal operation when this Pin is left floating or driven to a low level

(

≤ 0.6 V). The typical value of the threshold is 1.3 V and the voltage on this pin must not

exceed 25 V.