EVALUATION KIT AVAILABLE Digitally Controlled, 0.5% Accurate,
Safest APD Bias Supply MAX1932 General Description Benefits and Features The MAX1932 generates a low-noise, high-voltage output
to bias avalanche photodiodes (APDs) in optical
receivers. Very low output ripple and noise is achieved by
a constant-frequency, pulse-width modulated (PWM)
boost topology combined with a unique architecture that
maintains regulation with an optional RC or LC post filter
inside its feedback loop. A precision reference and error
amplifier maintain 0.5% output voltage accuracy.
The MAX1932 protects expensive APDs against adverse
operating conditions while providing optimal bias.
Traditional boost converters measure switch current for
protection, whereas the MAX1932 integrates accurate
high-side current limiting to protect APDs under
avalanche conditions. A current-limit flag allows easy calibration of the APD operating point by indicating the precise point of avalanche breakdown. The MAX1932 control
scheme prevents output overshoot and undershoot to
provide safe APD operation without data loss. • Unique Architecture Delivers Excellent Accuracy for The output voltage can be accurately set with either
external resistors, an internal 8-bit DAC, an external
DAC, or other voltage source. Output span and offset
are independently settable with external resistors. This
optimizes the utilization of DAC resolution for applications that may require limited output voltage range, such
as 4.5V to 15V, 4.5V to 45V, 20V to 60V, or 40V to 90V. •
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