M02013_15 Datasheet, PDF (15/21 Pages) M/A-COM Technology Solutions, Inc. – CMOS Transimpedance Amplifier with AGC for Fiber-optic Networks up to 3.2 Gbps

M02013
CMOS Transimpedance Amplifier with AGC
for Fiber-optic Networks up to 3.2 Gbps
Rev V8
4.3
Treatment of PINK
PINK requires bypassing to ground with a capacitor when powering a photo diode. If PINK is not used to bias the
photo diode, then it is not necessary to bypass an unused PINK.
4.4
Monitor O/P Calibration
This output is compatible with the DDMI Receive Power Specification (SFF-8472) and MACOM’s DDMI controller
products. Ensure that the voltage on V_MON is in the range of 1V to V_CC. Refer to Figure 4-1.
Because the offset for the monitor output can be in either direction (+ or -), it is not possible to calibrate out the
offset when there is not an input signal present. To properly calibrate the offset, a known input power between -23
dBm to -18 dBm should be used and the resulting monitor output compared with the expected output and the offset
calibrated.
For example, with a responsivity of 1.0, an input power of -20 dBm (equivalent to 10 µW) should result in a monitor
current of 10.0 µA. The offset is found by subtracting the measured monitor current from the expected monitor
current. This offset is then added (with its sign) to all subsequent monitor readings. In this case, if the monitor
current was found to be 8.5 µA, then the offset value to be used is (positive) 1.5µA and all readings should be
corrected by adding 1.5 µA to the monitor value. However, if the reading was 10.7 µA, then the offset is -0.7 µA,
and 0.7 µA should be subtracted from all subsequent monitor readings.
For the example above, if the responsivity is 0.90, then an input power of -20 dBm (still equivalent to 10 µW) should
result in a monitor current of 9.0 µA (0.9 A/W x 10 µW). Again, if the measured current is 8.5 µA, then the offset
would be calculated as +0.5 µA and all readings should be corrected by adding 0.5 µA to the monitor value. If the
measured current is 10.7 µA, then the offset is -1.7 µA and 1.7 µA should be subtracted from all subsequent
monitor readings.
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