5

LT1120A

Pin 1 (Ground).

Pin 2 (Feedback): This is the feedback point of the

regulator. When operating, it is nominally at 2.5V.

Optimum source resistance is 200k to 500k. The feedback

pin should not be driven below ground or more positive

than 5V.

Pin 3 (Shutdown): A logic 1 shuts off main regulator.

Caution: noise or leakage into the shutdown pin can affect

output voltage.

Pin 4 (Regulator Output): Main output, requires 10

µF

damaging device.

Pin 5 (Input Supply): Bypass with 10

µF cap. Must always

be more positive than ground.

Pin 6 (Reference): 2.5V can source or sink current. May

be shorted to ground or up to 5V. Voltages in excess of 5V

can damage the device.

Pin 7 (Comparator Output): May be connected to any

voltage from ground to 36V more positive than ground

Pin 8 (Comparator Input): Inverting comparator input.

–

+

100k

5

7

6

REFERENCE

8

–INPUT

120k

COMPARATOR

OUT

2

FEEDBACK

3

SHUTDOWN

1

GROUND

REF

2.5V

1120A BD01

The LT1120A is especially suited for micropower system

applications. For example, the comparator section of the

LT1120A may be used as a battery checker to provide an

indication of low battery. Another type of system applica-

tion for the LT1120A would be to generate the equivalent

of split supplies off of a single power input. The regulator

section provides regulated output voltage and the

reference, which can both source and sink current is then

an artificial system ground providing a split supply for

the system.

For many applications the comparator can be frequency

compensated to operate as an amplifier. Compensation

values for various gains are given in the data sheet. The

comparator gain is purposely low to make it easier to

frequency compensate as an amplifier. The NPN output is

capable of sinking 10mA and can drive loads connected to

voltages in excess of the positive power supply. This is

useful for driving switches or linear regulators off of a

higher input voltage.