LTC1261
Switched Capacitor
Regulated Voltage Inverter
FEATURES
DESCRIPTION
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
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 applications 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.
n
APPLICATIONS
n
n
n
n
GaAs FET Bias Generators
Negative Supply Generators
Battery-Powered Systems
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.
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
Waveforms for –4V Generator with Power Valid
–4V Generator with Power Valid
5V
VCC
SHDN
8
2
C1
1µF
C2
0.1µF
7
REG
C1 +
LTC1261-4
3
6
OUT
C1 –
4
*OPTIONAL
GND
COMP
0V
10k
POWER VALID
5
C3*
100pF
+
1
5V
C4
3.3µF
VOUT = –4V
AT 10mA
LTC1261 • TA01
OUT
–4V
SHDN
5V
0V
5V
POWER VALID
0V
0.2ms/DIV
LTC1261 • TA02
1261fb
For more information www.linear.com/LTC1261
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