LTC1682_15 Datasheet, PDF (1/12 Pages) Linear Technology – Doubler Charge Pumps with Low Noise Linear Regulator

FEATURES
s _{Low Output Noise: 60µVRMS (100kHz BW)}
s _{Adjustable or Fixed Boosted Output}
s _{Adjustable Output Voltage Range: 2.5V to 5.5V}
s _{Fixed Output Voltages: 3.3V, 5V}
s _{Wide Input Voltage Range: 1.8V to 4.4V}
s _{Uses Small Ceramic Capacitors}
s _{No Inductors Required}
s _{Output Current up to 50mA}
s _{550kHz Switching Frequency}
s _{Low Operating Current: 150µA}
s _{Low Shutdown Current: 1µA}
s _{Internal Thermal Shutdown and Current Limiting}
s _{Available in 8-Pin MSOP and SO Packages}
U
APPLICATIO S
s _{VCO Power Supplies in Cellular Phones}
s _{2-Way Pagers}
s _{Wireless PCMCIA Cards}
s _{Portable Medical Instruments}
s _{Low Power Data Acquisition}
s _{Remote Transmitters}
LTC1682/LTC1682-3.3/LTC1682-5
Doubler Charge Pumps with
Low Noise Linear Regulator
DESCRIPTIO
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
Open-Loop Close-In Phase Noise
4.7µF
V_IN
2.5V TO
4.4V
0.22µF
4.7µF
8 _CPO
7 _C+
SHUTDOWN
V_OUT ¹
4.2V
4.7µF
2
SHDN
B
P
1000pF
VCO
MURATA
MQE001-902
LTC1682
6 _VIN
FB ³
36k
1µF
M
C
5 _C–
GND ⁴
15k _1k
1000pF
1000pF
f_OUT
902MHz
100k
V_C
AMPLITUDE
10dB/DIV
4.7µF
1682 TA01
CENTER = 902MHz
SPAN = 100kHz
SWP = 10 sec
RES BW = 1kHz
VBW = 30Hz
REF = 0dBm
1682 TA02
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