A
.38 Watt LCD Single DC/DC Converter
2401 Stanwell Drive · Concord, California 94520 · Ph: 925/687-4411 or 800/542-3355 · Fax: 925/687-3333 · www.calex.com · Email: sales@calex.com
1
eco: 010918-2, eco# 041007-1, eco# 050628-1
Features
5 Volt Input
Positive or Negative LCD Bias Output
Simple 4 Terminal Operation
Low Cost
Small Sealed SIP Package
5 Year Warranty
Description
The Model 5S25.030LCD DC/DC converter provides a low
cost way to derive the bias voltage for LCD displays in
systems where only 5 volt digital voltage is available.
The LCD model converts 5 volt inputs to an isolated 25
volts DC at up to 750 milliwatts of power. The simple 4 terminal
operation allows for quick system design.
The isolated output allows the LCD converter to be
connected in either a positive output mode for color displays
or as a negative bias for monochrome displays.
The LCD is packaged in an environmentally rugged plastic
case. The use of special potting compounds allows the
converters to be water washed and operate over the full -40°
to 85°C industrial temperature range.
Applications Information
Connecting To Your System
Figure 1 shows the input and output connections for the LCD
series of converters. The output should be bypassed with at
least a 4.7 µF tantalum capacitor. For lower noise operation,
especially at low temperatures this value may be increased to
10 or 20 µF as required.
Figure 1.
The output of the LCD model should be bypassed with a 4.7 to 20µF
tantalum. The input may need to be bypassed if the converter is
more than 1 to 2 inches from the input source or if the source
impedance is high.
The input should be bypassed if it is more than about 1 or
2 inches from the input supply or if the input source impedance
is large. A 1 to 20 µF tantalum works well for the input bypass.
Figure 2.
The LCD series may be connected to supply either a positive or
negative LCD bias voltage as shown.
For a positive LCD Bias voltage connect pin 3 to pin 2 and
take the positive bias voltage from pin 4. For a negative bias
voltage connect pin 4 to pin 2 and take the negative bias
voltage from pin 3. These connections are shown in figure 2.
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Specifications subject to change without notice.
NOTE
(1)
Water Washability - Calex DC/DC converters are designed to
withstand most solder/wash processes. Careful attention should
be used when assessing the applicability in your specific
manufacturing process. Converters are not hermetically sealed.
A
.38 Watt LCD Single DC/DC Converter
2401 Stanwell Drive · Concord, California 94520 · Ph: 925/687-4411 or 800/542-3355 · Fax: 925/687-3333 · www.calex.com · Email: sales@calex.com
2
eco: 010918-2, eco# 041007-1, eco# 050628-1
direct digital control of the LCD bias voltage. The basic circuits
shown work for either positive or negative bias voltages. Due
to the fact that the LCD series converters are isolated from the
input circuits they can't "tell" how they are hooked up. As long
as the load current flows from out of the +output to the -output,
what is called ground is arbitrary.
Circuit D
Minimum Parts Regulator
Circuit C
Regulated Bias Adjust
Circuit A
Low Power Bias Adjust
Circuit B
Low Cost Bias Adjust
Generating Adjustable Bias Voltages
Most LCD Applications require an adjustable LCD bias voltage.
Since every system has different requirements for adjustability
and power level, several typical circuits are given. These
circuits although shown with trimpot adjustment, may be
easily adapted to digital control by connecting a D/A converter
output to the bottom of the divider resistors. This will allow
Pin Out
Figure 3.
Circuits A-D show several increasingly accurate methods for controlling the LCD Bias voltage as may be required for your specific display. In
all cases the divider resistors and trimpot should be selected to give the proper range of output voltage as required by your circuit. These circuits
may be used for positive or negative LCD bias adjustments as required. Just insert the circuits shown between the LCD output and any ground
connections as shown in figure 2.
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