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.38 Watt LCD Single Series DC/DC Converters
Features
! 3 or 5 Volt Inputs
! Positive or Negative LCD Bias Output
! Simple 4 Terminal Operation
! Low Cost
! Small Sealed SIP Package
! 5 Year Warranty
Description Selection Chart
The LCD Series of DC/DC converters provides a low cost way Input Range
Output
to derive the bias voltage for LCD displays in systems where VDC
Model
only 3 or 5 volt digital voltages are available. Min Nom Max VDC mA
The LCD series converts 3 or 5 volt inputs to an isolated 25 3S25.015LCD 3.0 3.3 3.6 25 15
volts DC at up to 750 milliwatts of power. The simple 4 terminal
5S25.030LCD 4.5 5.0 5.5 25 30
operation allows for quick system design.
Load Regulation,
The isolated output allows the LCD converter to be 25% Typical
25% to 100% Load
connected in either a positive output mode for color displays
Line Regulation 1.3% / % VIN Typical
or as a negative bias for monochrome displays.
Efficiency 60% Typical
The LCD series is packaged in an environmentally rugged
Operating Temperature Range
plastic case. The use of special potting compounds allows the -40° to 85°C
(Case)
converters to be water washed and operate over the full -40°
Specifications subject to change without notice.
to 85°C industrial temperature range.
Applications Information 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
Connecting To Your System
voltage connect pin 4 to pin 2 and take the negative bias
Figure 1 shows the input and output connections for the LCD voltage from pin 3. These connections are shown in figure 2.
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.
A
Figure 1.
The output of the LCD series 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 Figure 2.
2 inches from the input supply or if the input source impedance The LCD series may be connected to supply either a positive or
is large. A 1 to 20 µF tantalum works well for the input bypass. negative LCD bias voltage as shown.
CompuMess Elektronik GmbH · Lise-Meitner-Str.1 · 85716 Unterschleissheim
Tel 089-321501-0 · Fax 089-321501-11 · www.compumess.de · www.netzteile.de
1 eco: 010918-2, 9/2001
.38 Watt LCD Single Series DC/DC Converters
Pin Out
Generating Adjustable Bias Voltages
Most LCD Applications require an adjustable LCD bias voltage. direct digital control of the LCD bias voltage. The basic circuits
Since every system has different requirements for adjustability shown work for either positive or negative bias voltages. Due
and power level, several typical circuits are given. These to the fact that the LCD series converters are isolated from the
circuits although shown with trimpot adjustment, may be input circuits they can't "tell" how they are hooked up. As long
easily adapted to digital control by connecting a D/A converter as the load current flows from out of the +output to the -output,
output to the bottom of the divider resistors. This will allow what is called ground is arbitrary.
Circuit A Circuit B
Low Power Bias Adjust Low Cost Bias Adjust
Circuit C A
Circuit D
Regulated Bias Adjust Minimum Parts Regulator
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.
CompuMess Elektronik GmbH · Lise-Meitner-Str.1 · 85716 Unterschleissheim
Tel 089-321501-0 · Fax 089-321501-11 · www.compumess.de · www.netzteile.de
2 eco: 010918-2, 9/2001