LTC1682/LTC1682-3.3/LTC1682-5
Doubler Charge Pumps with
Low Noise Linear Regulator
FEATURES
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DESCRIPTIO
Low Output Noise: 60
µ
V
RMS
(100kHz BW)
Adjustable or Fixed Boosted Output
Adjustable Output Voltage Range: 2.5V to 5.5V
Fixed Output Voltages: 3.3V, 5V
Wide Input Voltage Range: 1.8V to 4.4V
Uses Small Ceramic Capacitors
No Inductors Required
Output Current up to 50mA
550kHz Switching Frequency
Low Operating Current: 150µA
Low Shutdown Current: 1µA
Internal Thermal Shutdown and Current Limiting
Available in 8-Pin MSOP and SO Packages
APPLICATIO S
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VCO Power Supplies in Cellular Phones
2-Way Pagers
Wireless PCMCIA Cards
Portable Medical Instruments
Low Power Data Acquisition
Remote Transmitters
The LTC
®
1682/LTC1682-3.3/LTC1682-5 are doubler charge
pumps with an internal low noise, low dropout (LDO) linear
regulator. These parts are designed to provide a low noise
boosted supply voltage for powering noise sensitive devices
such as high frequency VCOs in wireless applications.
An internal doubler charge pump converts a 1.8V to 4.4V
input to a boosted output, while the internal LDO regulator
converts the boosted voltage to a low noise regulated output.
The adjustable version allows the user to set V
OUT
via external
resistors connected to FB. The regulator is capable of supply-
ing up to 50mA of output current. Shutdown reduces the
supply current to < 5µA, removes the load from V
IN
by
disabling the regulator and discharges V
OUT
to ground
through a 100Ω switch.
The LTC1682 LDO regulator is stable with only 2µF on the
output. Small ceramic capacitors can be used, reducing PC
board area.
The LTC1682/LTC1682-3.3/LTC1682-5 are short-circuit and
over temperature protected. The parts are available in 8-pin
MSOP and SO packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
4.2V VCO Power Supply, V
IN
= 2.5V to 4.4V
SHUTDOWN
8
4.7µF
7
V
IN
2.5V TO
4.4V
6
0.22µF
4.7µF
5
C
–
GND
4
C
+
V
IN
SHDN
LTC1682
FB
36k
3
15k
1µF
1k
1000pF
1000pF
4.7µF
1682 TA01
CPO
V
OUT
1
2
4.2V
4.7µF
1000pF
B
P
VCO
MURATA
MQE001-902
M
C
f
OUT
902MHz
100k
V
C
AMPLITUDE
10dB/DIV
U
Open-Loop Close-In Phase Noise
CENTER = 902MHz
SPAN = 100kHz
SWP = 10 sec
RES BW = 1kHz
VBW = 30Hz
REF = 0dBm
1682 TA02
U
U
1
LINER [ LINEAR TECHNOLOGY ]
