The MAX8728 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 display (LCD) panels in
LCD monitors and LCD TVs. The EV kit contains a stepdown
switching regulator, 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 is a logic-controlled,
high-voltage switch with adjustable delay, and
a capacitive dummy load at the gate-on supply for ease
of testing.
The EV kit, as configured, provides the following outputs
from a +10VDC to +13.2VDC power supply. The
step-down switching regulator is configured for a +3.3V
output, providing at least 2A. The step-up switching
regulator is configured for a +13.5V output, providing at
least 500mA. The positive charge pump is configured
for a +28V output, providing at least 50mA. The negative
charge pump is configured for a -6V output, providing
at least 150mA. The high-voltage switch can be
controlled by external logic and can be configured for a
delay set by an external capacitor.
The MAX8728 switches at 1.5MHz, allowing the use of
tiny surface-mount components. The EV kit can also
operate at a lower frequency with component changes.
The MAX8728 TQFN package (0.8mm maximum
height) with low-profile external components allows this
circuit to be less than 2mm high.
Key Features
Configured for +10V to +13.2V Input Range
Output Voltages
+3.3V Output at 2A (Step-Down Switching Regulator)
+13.5V Output at 500mA (Step-Up Switching Regulator)
+28V Output at 50mA (Positive Charge Pump)
-6V Output at 150mA (Negative Charge Pump)
Resistor-Adjustable Switching Regulator and Charge-Pump Output Voltages
Logic-Controlled, High-Voltage Switch with Adjustable Delay
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