QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 445
TRIPLE OUTPUT POWER SUPPLY FOR LCD PANELS
LT1944-1
DESCRIPTION
Demonstration circuit 445 is a highly integrated three-
output converter designed as a low-cost, small size so-
lution to provide bias voltages in small portable TFT-LCD
panels. It is capable of providing 5V/30mA, 15V/2.5mA,
and –10V/1mA using the LT1944-1 dual step-up con-
verter from an input as low as 2.7V. 5V and 15V outputs
are adjustable with a change in the feedback resistors.
The third output is a negative level shifted voltage off the
main regulators.
Design files for this circuit board are available. Call
the LTC factory.
QUICK START PROCEDURE
Refer to Figure 1 for proper measurement equipment
setup and follow the procedure below:
NOTE:
When measuring the output ripple, see Figure 2
for proper scope probe technique.
1.
Apply a voltage source to the input of the circuit be-
tween the Vin
and GND terminals. The circuit will start
up at an input voltage higher than 1.2V. Do not apply
more than 6V to the input.
NOTE:
The 6V maximum is set by the voltage rating of
the input capacitor, the absolute maximum rating for
Vin and shutdown pins of LT1944-1 is 15V.
2.
Attach voltmeters or oscilloscope probes between
each output
and its closest
GND terminal to monitor
the outputs. Switch on the desired channel(s) by set-
ting JP1 and JP2 to the run position.
3.
Connect the proper load at each output.
+
–
+
–
+
–
+
–
LOAD
LOAD
+
–
+
–
+
–
+
–
LOAD
+–
+–
+–
Figure 1.
Proper Measurement Equipment Setup
VIN
GND
Figure 2.
Scope Probe Placement for Measuring Output Ripple
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 445
TRIPLE OUTPUT POWER SUPPLY FOR LCD PANELS
Table 1.
Performance Summary
PARAMETER CONDITION VALUE
Minimum Input Voltage 1.2V
Maximum Load Current at 5V Output (minimum) Vin = 2.7V to 4.2V 30mA
Maximum Load Current at 15V Output (minimum) Vin = 2.7V to 4.2V 2.5mA
Maximum Load Current at -10V Output (minimum) Vin = 2.7V to 4.2V 1mA
Typical Output Ripple at 5V Vin=3.3V, Iout1=30mA, Iout2=2.5mA, Iout3=1mA 120mV
Typical Output Ripple at 15V Vin=3.3V, Iout1=30mA, Iout2=2.5mA, Iout3=1mA 50mV
Typical Output Ripple at -10V Vin=3.3V, Iout1=30mA, Iout2=2.5mA, Iout3=1mA 15mV
2
