Datasheet

LTC1261
11
1261fb
For more information www.linear.com/LTC1261
TYPICAL APPLICATIONS
APPLICATIONS INFORMATION
Table 2. Output Voltages Using the Internal Resistor Divider
PIN CONNECTIONS OUTPUT VOLTAGE
ADJ to RADJ –5V
ADJ to RADJ, R0 to GND –4.5V
ADJ to RADJ, R1 to R0 –4V
ADJ to RADJ, R1 to GND –3.5V
ADJ to R1 –1.77V
ADJ to R0 –1.38V
ADJ to GND –1.24V
There are some oddball output voltages available by con-
necting ADJ to R0 or R1 and shorting out some of the
internal
resistors. If one of these combinations gives you
the output voltage you want, by all means use it!
The internal resistor values are the same for the fixed
output versions of the LTC1261 as they are for the
adjustable. The output voltage can be trimmed, if desired,
by connecting external resistance from the COMP pin to
OUT or ground to alter the divider ratio. As in
the adjustable
parts, the absolute value of the internal resistors may vary
significantly from unit to unit. As a result, the further the
trim shifts the output voltage the less accurate the output
voltage will be. If a precise output voltage other than one
of the available fixed voltages is required, it is better to
use an adjustable LTC1261 and use precision external
resistors. The internal reference
is trimmed at the factory
to within 3.5% of 1.24V; with 1% external resistors the
output will be within 5.5% of the nominal value, even
under worst case conditions.
The LTC1261 can be internally configured with nonstan-
dard fixed output voltages. Contact the Linear Technology
Marketing Department for details.
3.3V Input, –4.5V Output GaAs FET Bias Generator
2
3
4
5
8
13
12
11
10
9
SHDN
REG
OUT
ADJ
R
ADJ
C1
+
C1
–
C2
+
C2
–
R1
0.1µF
100pF
1µF
NC
LTC1261 • TA03
3.3µF
–4.5V BIAS
10k
7 6
14
0.1µF
SHUTDOWN
3.3V
V
BAT
LTC1261
V
CC
R0 GND
GaAs
TRANSMITTER
P-CHANNEL
POWER SWITCH
+