90V Boost DC/DC Converter with APD Current Monitor

10th September 2007

ES Admin

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Linear Technology has announced the LT3482, a fixed frequency, current mode step-up DC/DC converter with a built-in voltage doubler designed to bias avalanche photodiodes (APDs) in optical receivers. The device can deliver an output of up to 90V from inputs ranging from 2.5V to 16V. The LT3482 features high side APD current monitoring, which offers better than 10% relative accuracy over a -40°C to 85°C temperature range. The integrated power switch, Schottky diodes, and APD current monitor are all on a single die, packaged in a tiny 3mm x 3mm QFN, providing a tiny solution footprint.

The LT3482's internal 48V, 280mA switch uses a voltage doubler to deliver voltages as high as 90V. A constant frequency architecture is used to minimize switching noise and is user selectable at either 625kHz or 1.1MHz. Low output ripple, critical in APD applications, is maintained under 80uVPK-PK without any additional filtering. The integrated high side current monitor produces a current proportional to APD current with better than 10% relative accuracy over four decades of dynamic range in the APD input current range of 250nA to 2.5mA. Additionally, the LT3482 is equipped with both a 1.235V internal reference and an auxiliary reference input (via the CTRL pin), enabling the output voltage to be adjusted while the chip is operating. Other features include soft-start, internal compensation and thermal shutdown.

The LT3482EUD operates from a 0°C to 85°C temperature range whereas the LT3482IUD operates from a -40°C to 85°C temperature range. Both parts are available from stock. Pricing starts at $3.45 each for the LT3482EUD and $4.14 each for the LT3482IUD in 1,000-piece quantities.
Summary of Features of the LT3482:

* High Output Voltage: Up to 90V
* Integrated Schottky Diodes
* 48V, 280mA Internal Switch
* High Side APD Current Monitor
* Adjustable Switching Frequency: 650kHz or 1.1MHz
* Wide VIN Range: 2.5V to 16V
* Low Shutdown Current: <1uA
* Soft-Start
* Internal Compensation
* CTRL Pin Allows Output Adjustment with No Polarity Inversion
* 3mm x 3mm 16-Lead QFN Package