1
LTC1682/LTC1682-3.3/LTC1682-5
Doubler Charge Pumps with
Low Noise Linear Regulator
■
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
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.
Open-Loop Close-In Phase Noise
CENTER = 902MHz RES BW = 1kHz
SPAN = 100kHz VBW = 30Hz
SWP = 10 sec REF = 0dBm
1682 TA02
4.2V VCO Power Supply, V
IN
= 2.5V to 4.4V
■
VCO Power Supplies in Cellular Phones
■
2-Way Pagers
■
Wireless PCMCIA Cards
■
Portable Medical Instruments
■
Low Power Data Acquisition
■
Remote Transmitters
AMPLITUDE
10dB/DIV
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
36k
SHUTDOWN
15k
100k
4.7µF
0.22µF
V
IN
2.5V TO
4.4V
4.7µF
4.2V
1
2
3
4
8
7
6
5
V
OUT
SHDN
FB
GND
CPO
C
+
V
IN
C
–
1682 TA01
LTC1682
VCO
MURATA
MQE001-902
1µF
4.7µF
1000pF
1k
B
M
P
C
1000pF
1000pF
4.7µF
V
C
f
OUT
902MHz
