LTC1550_15 Datasheet, PDF (1/12 Pages) Linear Technology – Low Noise, Switched Capacitor Regulated Voltage Inverters

LTC1550/LTC1551
Low Noise, Switched
Capacitor Regulated
Voltage Inverters
FEATURES
s _{Regulated Negative Voltage from a Single}
Positive Supply
s _{Low Output Ripple: Less Than 1mVP-P Typ}
s _{High Charge Pump Frequency: 900kHz Typ}
s _{Small Charge Pump Capacitors: 0.1µF}
s _{Requires Only Four External Capacitors}
s _{Fixed – 4.1V or Adjustable Output}
s _{Shutdown Mode Drops Supply Current to < 1µA}
s _{High Output Current: Up to 10mA, VCC = 5V}
s _{Output Regulation: 5%}
s _{Available in SO-8 and 16-Lead SSOP}
U
APPLICATIONS
s _{GaAs FET Bias Generators}
s _{Negative Supply Generators}
s _{Battery-Powered Systems}
s _{Single Supply Applications}
, LTC and LT are registered trademarks of Linear Technology Corporation.
DESCRIPTION
The LTC^®1550/LTC1551 are switched capacitor charge
pump voltage inverters which include internal linear post-
regulators to minimize output ripple. Output voltages are
fixed at – 4.1V, with ripple voltages typically below 1mV_P-P.
The LTC1550 is also available in an adjustable output
voltage version. The LTC1550/LTC1551 are ideal for use
as bias voltage generators for GaAs transmitter FETs in
portable RF and cellular telephone applications.
The LTC1550/LTC1551 operate from single 4.5V to 6.5V
supplies and draw typical quiescent currents of 4.25mA
with a 5V supply. Each device includes a TTL compatible
Shutdown pin which drops supply current to 0.2µA typi-
cally. The LTC1550 Shutdown pin is active low (SHDN),
while the LTC1551 Shutdown pin is active high (SHDN).
Only four external components are required: an input bypass
capacitor, two 0.1µF charge pump capacitors and a filter
capacitor at the linear regulator output. The adjustable LTC1550
requires two additional resistors to set the output voltage. The
LTC1550/LTC1551 will supply up to 10mA output current
with a 5V supply, while maintaining guaranteed output
regulation of ±5%.
The fixed voltage LTC1550/LTC1551 are available in S0-8
plastic packages. The adjustable LTC1550 is available in a
16-pin SSOP.
TYPICAL APPLICATION
V_CC
+ _4.7µF
C_IN
– 4.1V Generator with 1mV_P-P Noise
1
SHDN
2
V_CC
8
SENSE
7
CP_OUT
LTC1551
3 _C1+
GND ⁶
4
V_OUT
C1^{– 5}
C1
0.1µF
C_CP
0.1µF
FERRITE BEAD
C_OUT
10µF
V_OUT = –4.1V
I_LOAD = 5mA
C_L
0.1µF
1550/51 F01
V_OUT Output Noise and Ripple
V_OUT
AC COUPLED
2mV/DIV
10µs/DIV
1550/51 TA02
1