LTC1261_15 Datasheet, PDF (1/18 Pages) Linear Technology – Switched Capacitor Regulated Voltage Inverter

LTC1261
Switched Capacitor
Regulated Voltage Inverter
FEATURES
n _{Regulated Negative Voltage from a}
Single Positive Supply
n _{Can Provide Regulated –5V from a 3V Supply}
n _{REG Pin Indicates Output is in Regulation}
n _{Low Output Ripple: 5mV Typ}
n _{Supply Current: 600µA Typ}
n _{Shutdown Mode Drops Supply Current to 5µA}
n _{Up to 15mA Output Current}
n _{Adjustable or Fixed Output Voltages}
n _{Requires Only Three or Four External Capacitors}
n _{Available in SO-8 Packages}
APPLICATIONS
n _{GaAs FET Bias Generators}
n _{Negative Supply Generators}
n _{Battery-Powered Systems}
n _{Single Supply Applications}
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
DESCRIPTION
The LTC^®1261 is a switched-capacitor voltage inverter
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
voltages 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 0.1µF
capacitor and provides adjustable and fixed output voltage
options in 8-lead SO packages. The LTC1261CS requires
one or two external 0.1µF 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 600µA when operating and 5µA in shutdown.
The LTC1261 is available in a 14-lead narrow body SO
package and an 8-lead SO package.
TYPICAL APPLICATION
5V
C1
C2
1µF
0.1µF
*OPTIONAL
–4V Generator with Power Valid
1 _VCC
SHDN ⁸
2 _C1+
REG ⁷
3
LTC1261-4
C1^–
OUT
6
4 _{GND COMP} 5
5V
10k
C3*
100pF
POWER VALID
V_OUT = –4V
AT 10mA
C4
+ 3.3µF
LTC1261 • TA01
Waveforms for –4V Generator with Power Valid
0V
OUT
–4V
5V
SHDN
0V
5V
POWER VALID
0V
For more information www.linear.com/LTC1261
0.2ms/DIV
LTC1261 • TA02
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