Status
Active: In Production.
Description
The MAX1543 evaluation kit (EV kit) is a fully assembled
and tested surface-mount circuit board that provides
the voltages and features required for active-matrix,
thin-film transistor (TFT) liquid-crystal displays (LCDs).
The EV kit contains a step-up switching regulator, a
positive two-stage charge pump for the TFT gate-on
supply, and a negative single-stage charge pump for
the TFT gate-off supply. Also included are two operational
amplifiers that can be used to drive the LCD
backplane (VCOM) or the gamma-correction divider
string, and a logic-controlled, high-voltage switch with
adjustable delay. The EV kit also evaluates the
MAX1542 after IC replacement.
The EV kit operates from a DC supply voltage of +2.6V
to +5.5V. The step-up switching regulator is configured
for a +8V output providing at least 250mA. The positive
charge pump is configured for a +22V output providing
at least 20mA. The negative charge pump is configured
for a -7V output providing at least 20mA. The two operational
amplifiers are both configured for +4V, each
capable of providing up to ±150mA peak. The high-voltage
switch can be used to delay the startup of the
positive charge pump's output. The delay time is set
with an external capacitor.
The MAX1543 EV kit demonstrates low quiescent current
and high efficiency (85%) for maximum battery life.
Operation at 1.2MHz allows the use of tiny surface-mount
components. The MAX1543 QFN package
(0.8mm maximum height) with low-profile external com-ponents
allows this circuit to be less than 1.25mm high.
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