LTC1550L_15 Datasheet, PDF (1/12 Pages) Linear Technology – 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}
s _{Small Charge Pump Capacitors: 0.1µF}
s _{Requires Only Four External Capacitors}
s _{Fixed – 4.1V, –2.5V, –2V or Adjustable Output}
s _{Shutdown Mode Drops Supply Current to <1µA}
s _{High Output Current: Up to 20mA (Depending on}
V_CC to V_OUT Range)
s _{Output Regulation: 2.5% Over Line, Load and}
Temperature
s _{Available in 8-Lead MSOP, 8-Lead Narrow SO and}
16-Lead Narrow SSOP
U
APPLICATIO S
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.
TYPICAL APPLICATIO
3.6V
+ _2.2µF
C_IN
1
SHDN
2
V_CC
8
REG
7
CP_OUT
LTC1550L-2
3 _C1+
GND ⁶
4
V_OUT
C1^{– 5}
R1
10k
POWER VALID
C_CP
0.1µF
C1
0.1µF
C_OUT
10µF
V_OUT = –2V
I_LOAD = 5mA
C_L
0.1µF
1550L/51L TA01
Figure 1. – 2V Generator with 1mV_P-P Noise
LTC1550L/LTC1551L
Low Noise, Switched
Capacitor Regulated
Voltage Inverters
DESCRIPTIO
The LTC^®1550L/LTC1551L are switched capacitor charge
pump voltage inverters which include internal linear post-
regulators to minimize output ripple. The LTC1550L fixed
output voltage versions include –4.1V, –2.5V and –2V with
ripple voltages typically below 1mV_P-P. The LTC1550L is
also available in an adjustable output voltage version. The
LTC1550L/LTC1551L are ideal for use as bias voltage
generators for GaAs transmitter FETs in portable RF and
cellular telephone applications.
The LTC1550L/LTC1551L operate from single 2.7V to
5.5V supplies and draw typical quiescent currents of
3.5mA with a 5V supply. Each device includes a TTL
compatible Shutdown pin which drops supply current to
0.2µA typically. The LTC1550L Shutdown pin is active low
(SHDN), while the LTC1551L 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 LTC1550L/LTC1551L require two additional re-
sistors to set the output voltage. The LTC1550L/LTC1551L
will supply up to 20mA (depending on V_CC to V_OUT range),
while maintaining guaranteed output regulation of ±2.5%.
Both fixed voltage and adjustable LTC1550L/LTC1551L
are available in 8-lead MSOP and SO plastic packages: the
adjustable LTC1550L is also available in a 16-pin SSOP
with the REG pin.
V_OUT Output Noise and Ripple
V_OUT
AC COUPLED
2mV/DIV
5µs/DIV
1550L/51L TA01a
1