RT8541A

® RT8541/A 90V Boost DC/DC Converter with APD Current Monitor General Description The RT8541/A is a constant frequency current mode PWM step-up DC/DC converter designed to bias avalanche photodiodes (APD) at high voltage in optical receivers. It includes a voltage doubler charge pump to significantly reduce the noise level at output up to 90V. The RT8541A switching frequency can be adjusted by a resistor while RT8541 is internally set at 650kHz. The RT8541/A has a built-in APD current mirror that delivers 1/5 of the APD current with high accuracy for monitoring the APD current from 0.25μA to 2.5mA. This current can be used as a reference to provide a digital programmed output voltage via the CTRL pin. To protect the optical receiver system, the RT8541/A provides a built-in adjustable APD current limit function by sensing a 200mV voltage threshold between VOUT2 and MONIN pins. Only one resistor is needed to program the desired current limit. A charge pump voltage doubler is designed to achieve significantly lower noise level at the APD comparing to a simple boost converter type bias circuit. The RT8541/A also features a built-in 9ms soft-start function to eliminate the inrush current during start-up interval. The RT8541/A provides a low cost optical receiver solution and can fit in very small PCB area. The RT8541/A is available in the WQFN-16L 3x3 package. Features  Integrated Schottky Diodes for Charge Pump Voltage Doubler  50V, 400mA Internal Switch  High Side Low Nois...