Datasheet
LTC1261L
10
1261lfa
APPLICATIONS INFORMATION
TYPICAL APPLICATIONS
RESISTOR SELECTION
Resistor selection is easy with the fixed output voltage
versions of the LTC1261L—no resistors are needed! Se-
lecting the right resistors for the adjustable parts is only
a little more difficult. A resistor divider should be used to
divide the signal at the output to give 1.23V at the ADJ
pin with respect to V
OUT
(Figure 5). The LTC1261L uses
a positive reference with respect to V
OUT
, not a negative
reference with respect to ground (Figure 1 shows the
reference connection). Be sure to keep this in mind when
connecting the resistors! If the initial output is not what
you expected, try swapping the two resistors.
LTC1261L
GND
R1
4
5
6
1261L F05
V
OUT
= –1.23V
R2
R1 + R2
R2
ADJ
OUT
( )
Figure 5. External Resistor Connections
1mV Ripple, 5V Input, –4V Output GaAs FET Bias Generator
5V Input, –4V Output GaAs FET Bias Generator
1
2
3
4
8
7
6
5
SHDN
REG
OUT
COMP
V
CC
C1
+
C2
–
GND
100pF
1261 TA03
3.3µF
–4V BIAS
10k
P-CHANNEL
POWER SWITCH
0.1µF
SHUTDOWN
5V
V
BAT
LTC1261L-4
GaAs
TRANSMITTER
1µF
+
1
2
3
4
8
7
6
5
SHDN
REG
OUT
COMP
V
CC
C1
+
C2
–
GND
100pF
1261 TA04
10µF
–4V BIAS
100µH
10k
P-CHANNEL
POWER SWITCH
0.1µF
SHUTDOWN
5V
V
BAT
10µF
LTC1261L-4
GaAs
TRANSMITTER
1µF
+ +
The LTC1261L can be internally configured for other fixed
output voltages. Contact the Linear Technology Marketing
department for details.