The MAX1729 micropower step-up/step-down DC-DC converter is
ideally suited for electrically controlled birefringence (ECB) and
liquid-crystal-display (LCD) bias-supply generation. It provides
step-up/step-down voltage conversion and reduces output ripple by using a step-up DC-DC converter followed by a linear regulator. This architecture permits a physically smaller inductor than those used in competing SEPIC and flyback topologies. This device features low quiescent current (67µA typical). A logic-controlled shutdown mode further reduces quiescent current to 0.4µA typical.
The MAX1729 features an input that dynamically adjusts the output
voltage to control display color or contrast. It offers two feedback modes:
internal and external. Internal feedback mode allows output voltages between 2.5V and 16V, and is specifically designed to hold temperature drift to ±11ppm/°C. External feedback mode allows the MAX1729 output voltage range to be tailored for various displays.
An on-chip temperature sensor with a positive temperature
coefficient provides compensation for LCD/ECB display temperature
characteristics. In internal feedback mode, the buffered temperature sensor
output is read and used to adjust the output voltage via a digital control
signal. External feedback mode features an additional compensation method in
which the temperature output is summed directly into the feedback network to
provide first-order negative temperature compensation of the output voltage. The
MAX1729 is available in the space-saving 10-pin µMAX package.
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