7

LTC1550L/LTC1551L

–

+

–

+

S2

S3

S1

S4

C1

CLK

900kHz

CHARGE

PUMP

LINEAR

REGULATOR

1550L/51L BD

ADJ

REG

58mV

1.167V

*SHDN

*SHDN FOR LTC1550L, SHDN FOR LTC1551L

** FIXED OUTPUT VERSIONS ONLY

COMP2

**

**

+

1.225V

OVERVIEW

The LTC1550L/LTC1551L are switched capacitor, inverting

charge pumps with internal linear post-regulators. The

LTC1550L/LTC1551L provide a regulated, low ripple output

at up to 20mA load current with the appropriate input

voltage as output load current depends on the input/

output voltage combination. Consult the graph provided in

the Typical Performance Characteristics section and the

Electrical Characteristics table for guaranteed test points.

The LTC1550L/LTC1551L are ideal for use as bias voltage

generators for GaAs transmitter FETs in portable RF and

cellular telephone applications. The LTC1550L features an

active-low Shutdown pin (SHDN) that drops quiescent

current to below 1

µA. The LTC1551L is identical to the

LTC1550L, except that the Shutdown pin is active-high

(SHDN). All members of the LTC1550L/LTC1551L family

feature a 900kHz charge pump frequency. The LTC1550L/

LTC1551L come standard with fixed – 4.1V, –2.5V, –2V

and adjustable output voltages. The LTC1550L/LTC1551L

can be configured for other fixed output voltages; contact

Linear Technology for more information.