The MAX1997 evaluation kit (EV kit) is a fully assembled and tested surface-mount circuit board that provides voltages and features required for active-matrix thin-film transistor (TFT) liquid-crystal displays. The EV kit contains a step-up switching regulator, a positive three-stage charge pump and linear regulator for the TFT gate-on supply, a negative three-stage charge pump and linear regulator for the TFT gate-off supply, a gamma reference, a low-voltage logic supply, and a high-current backplane buffer. The gate-on supply, gate-off supply, and gamma reference supply can be sequenced in any power-up order.
The EV kit operates from a DC supply voltage of +2.7V to +5.5V. The step-up switching regulator is configured for a +9V output providing up to 250mA. The positive charge pump and regulator are configured for a +20V output using two charge-pump stages providing up to 10mA. The negative charge pump and regulator are configured for a -7V output using a single charge-pump stage providing up to 10mA. The gamma reference is configured for +8.6V providing up to 10mA. The low-voltage logic linear-regulator is configured for +2.5V, providing up to 200mA. The backplane buffer is configured for +4.3V and can source or sink current peaks more than 300mA.
The MAX1997 EV kit demonstrates low-quiescent current and high efficiency (85%) for maximum battery life. The EV kit features overload protection for the input and all outputs. Operation at 1.5MHz allows the use of tiny surface-mount components. The MAX1997 QFN package (0.8mm max) with low-profile external components allows this circuit to be less than 1.25mm high.
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