LTC3260
Low Noise Dual Supply
Inverting Charge Pump
FEATURES
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DESCRIPTION
The LTC
®
3260 is a low noise dual polarity output power
supply that includes an inverting charge pump with both
positive and negative LDO regulators. The charge pump
operates over a wide 4.5V to 32V input range and can deliver
up to 100mA of output current. Each LDO regulator can
provide up to 50mA of output current. The negative LDO
post regulator is powered from the charge pump output.
The LDO output voltages can be adjusted using external
resistor dividers.
The charge pump employs either low quiescent current
Burst Mode operation or low noise constant frequency
mode. In Burst Mode operation the charge pump V
OUT
regulates to
–0.94 •
V
IN
, and the LTC3260 draws only
100µA of quiescent current with both LDO regulators on.
In constant frequency mode the charge pump produces
an output equal to –V
IN
and operates at a fixed 500kHz
or to a programmed value between 50kHz to 500kHz us-
ing an external resistor. The LTC3260 is available in low
profile (0.75mm) 3mm x 4mm 14-pin DFN and thermally
enhanced 16-pin MSOP packages.
L,
LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
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V
IN
Range: 4.5V to 32V
Inverting Charge Pump Generates –V
IN
Charge Pump Output Current Up to 100mA
Low Noise Negative LDO Post Regulator
(I
LDO–
= 50mA Max)
Low Noise Independent Positive LDO Regulator
(I
LDO+
= 50mA Max)
100µA Quiescent Current in Burst Mode
®
Operation
with Both LDO Regulators On
50kHz to 500kHz Programmable Oscillator Frequency
Stable with Ceramic Capacitors
Short-Circuit/Thermal Protection
Low Profile 3mm
×
4mm 14-Pin DFN and Thermally
Enhanced 16-Pin MSOP Packages
APPLICATIONS
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Low Noise Bipolar/Inverting Supplies
Industrial/Instrumentation Low Noise Bias
Generators
Portable Medical Equipment
Portable Instruments
TYPICAL APPLICATION
±12V Outputs from a Single 15V Input
15V
V
IN
EN
+
LDO Rejection of V
OUT
Ripple
10µF
LDO
+
LTC3260
ADJ
+
BYP
+
GND
BYP
–
ADJ
–
10µF
12V
909k
100k
100k
909k
V
LDO+
10mV/DIV
AC-COUPLED
V
LDO–
10mV/DIV
AC-COUPLED
V
OUT
10mV/DIV
AC-COUPLED
V
IN
= 15V
V
LDO+
= 12V
V
LDO–
= –12V
f
OSC
= 500kHz
I
LDO+
= 50mA
I
LDO–
–50mA
1µs/DIV
3260 TA01b
EN
–
MODE
1µF
C
+
C
–
V
OUT
RT
10nF
10nF
–15V
10µF
LDO
–
10µF
3260 TA01a
–12V
200k
3260f
1