The MAX8795A evaluation kit (EV kit) is a fully assembled
and tested surface-mount printed-circuit board
(PCB) that contains a step-up switching regulator, a
positive charge pump postregulated by a high-voltage
linear regulator, a negative charge pump postregulated
by a high-voltage negative linear regulator, and five
high-current operational amplifiers (op amps). The primary
step-up converter is configured for a +14V output
(VMAIN) and provides at least 500mA from a +4.5VDC
supply voltage.
The positive and negative linear-regulator controllers
postregulate the charge-pump outputs for TFT gate-on
and gate-off supplies. The positive linear regulator is
set to +25V output (VPOS) and provides at least 20mA.
The negative linear regulator is set to -10V output
(VNEG) and provides at least 50mA. Power to the positive
charge-pump input comes from the step-up switching-regulator output, while power to the negative charge-pump input comes from the power ground.
The EV kit also features five high-performance op amps
designed to drive the LCD backplane (VCOM). Power
to the VCOM buffers comes from the step-up switching
regulator output. The MAX8795A EV kit demonstrates
low quiescent current and high efficiency for maximum
battery life. High-frequency (1.2MHz) operation allows
the use of tiny surface-mount components to minimize
the thickness of LCD panel designs.
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