5

LTC1261L

ground with at least a 1

µF capacitor placed in close

proximity to the chip. See the Applications Information

section for details.

µF capacitor

µFcapacitor

GND (Pin 4): Ground. Connect to a low impedance

ground. A ground plane will help to minimize regulation

errors.

ADJ (COMP for fixed versions) (Pin 5): Output Adjust/

Compensation Pin. For adjustable parts this pin is used

to set the output voltage. The output voltage is divided

down with an external resistor divider and fed back to this

pin to set the regulated output voltage. Typically the

resistor string should draw

≥10µA from the output to

minimize errors due to the bias current at the adjust pin.

Fixed output voltage parts have the internal resistor

string connected to this pin inside the package. The pin

can be used to trim the output voltage if desired. It can

also be used as an optional feedback compensation pin to

reduce output ripple on both the adjustable and fixed

output voltage parts. See the Applications Information

section for more information on compensation and out-

put ripple.

OUT (Pin 6): Negative Voltage Output. This pin must be

bypassed to ground with a 1

µF or larger capacitor. The

value of the output capacitor and its ESR have a strong

effect on output ripple. See the Applications Information

section for more details.

REG (Pin 7): This is an open-drain output that pulls low

when the output voltage is within 5% of the set value. It

will sink 5mA to ground with a 5V supply. The external

circuitry must provide a pull-up or REG will not swing

pulled up to 6V above ground without damage.

SHDN (Pin 8): Shutdown. When this pin is at ground the

LTC1261L operates normally. An internal 5

µA pull-down

keeps SHDN low if it is left floating. When SHDN is pulled

high, the LTC1261L enters shutdown mode. In shut-

down, the charge pump is disabled, the output collapses

to 0V and the quiescent current drops to 5

µA typically.

TEST CIRCUITS

Fixed Output

1

2

3

4

8

7

6

5

SHDN

REG

OUT

COMP

GND

0.1

µF

1261L TCO1

3.3

µF

5V

10

µF

+

LTC1261L-X

Adjustable Output

1

2

3

4

8

7

6

5

SHDN

REG

OUT

ADJ

GND

0.1

µF

1261L TCO2

3.3

µF

LTC1261L