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The MAX8758 evaluation kit (EV kit) is a fully assembled
and tested surface-mount PC board that provides the
voltages and features required for active-matrix, thin-film
transistor (TFT), liquid-crystal display (LCD) applications.
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. The included high-speed operational
amplifier 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 operates from a +2.2V to +5.5V DC supply
voltage. The step-up switching regulator is configured
for a +8.5V output, providing at least 330mA from 3.0V.
The positive charge pump is configured for a +23V output
providing at least 20mA. The negative charge pump
is configured for a -8V output providing at least 20mA.
The high-speed operational amplifier is configured for
+4.25V, capable of providing up to ±150mA peak. The
high-voltage switch can be used to delay the output of
the positive charge pump's startup. The delay time is set
with an external capacitor.
The MAX8758 EV kit demonstrates low quiescent current
and high efficiency for maximum battery life.
Operation at 1.2MHz allows the use of tiny surface-mount
components. The MAX8758 TQFN package
(0.8mm maximum height) with low-profile external components
allows this circuit to be less than 1.25mm high.
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