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LTC1261

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FEATURE

DESCRIPTIO

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Regulated Negative Voltage from a

Single Positive Supply

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Can Provide Regulated – 5V from a 3V Supply

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REG Pin Indicates Output is in Regulation

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Low Output Ripple: 5mV Typ

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Supply Current: 600

µA Typ

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Shutdown Mode Drops Supply Current to 5

µA

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Up to 15mA Output Current

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Adjustable or Fixed Output Voltages

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Requires Only Three or Four External Capacitors

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Available in SO-8 Packages

The LTC

designed to provide a regulated negative voltage from a

single positive supply. The LTC1261CS operates from a

single 3V to 8V supply and provides an adjustable output

voltage from –1.25V to – 8V. An on-chip resistor string

allows the LTC1261CS to be configured for output volt-

ages of – 3.5V, – 4V, – 4.5V or – 5V with no external

components. The LTC1261CS8 is optimized for applica-

tions which use a 5V or higher supply or which require

low output voltages. It requires a single external 0.1

µF

capacitor and provides adjustable and fixed output voltage

options in 8-pin SO packages. The LTC1261CS requires

one or two external 0.1

µF capacitors, depending on input

voltage. Both versions require additional external input

and output bypass capacitors. An optional compensation

capacitor at ADJ/COMP can be used to reduce the output

voltage ripple.

Each version of the LTC1261 will supply up to 12mA

output current with guaranteed output regulation of 5%.

The LTC1261 includes an open-drain REG output which

pulls low when the output is within 5% of the set value.

Output ripple is typically as low as 5mV. Quiescent current

is typically 600

µA when operating and 5µA in shutdown.

The LTC1261 is available in a 14-pin narrow body SO

package and an 8-pin SO package.

Switched Capacitor

Regulated Voltage Inverter

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GaAs FET Bias Generators

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Negative Supply Generators

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Battery-Powered Systems

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Single Supply Applications

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APPLICATI

– 4V Generator with Power Valid

, LTC and LT are registered trademarks of Linear Technology Corporation.

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2

3

4

8

7

6

5

LTC1261-4

SHDN

REG

OUT

COMP

GND

C2

0.1

µF

LTC1261 • TA01

C4

3.3

µF

AT 10mA

POWER VALID

5V

C1

1

µF

5V

10k

C3*

100pF

*OPTIONAL

Waveforms for – 4V Generator with Power Valid

0V

OUT

–4V

5V

SHDN

0V

5V

POWER VALID

0V

0.2mS/DIV

LTC1261 • TAO2