MAX3665

The MAX3665 low-power transimpedance preamplifier for 622Mbps SDH/SONET applications consumes only 70mW at VCC = 3.3V. Operating from a single +3.3V or +5.0V supply, it converts a small photodiode current to a measurable differential voltage. A DC cancellation circuit of MAX3665 provides a true differential output swing over a wide range of input current levels, thus reducing pulse-width distortion. The differential outputs of MAX3665 are back-terminated with 50Ω per side.

The overall transimpedance gain is nominally 8kΩ. For input signal levels beyond approximately 50µAp-p, the amplifier will limit the output swing to 250mV. The MAX3665's low 55nA input noise provides a typical sensitivity of -33.2dBm in 1300nm, 622Mbps receivers.

The MAX3665 is designed to be used in conjunction with the MAX3676 clock recovery and data retiming IC with limiting amplifier. Together they form a complete 3.3V or 5.0V 622Mbps SDH/SONET receiver.

In die form, the MAX3665 is designed to fit on a header with a PIN diode. It includes a filter connection that provides positive bias for the photodiode through a 1.5kΩ resistor to VCC. The device is available in an 8-pin µMAX package.