Functional Description

02139-DSH-001-D

Mindspeed Technologies

®

10

Mindspeed Proprietary and Confidential

For non-217X implementations, assume that the MON output would go into a resistor that is measured with a

voltage ADC. That being the case, a voltage drop (diode or other) would need to be switched in and out to create

the necessary voltage at the MON pin for both rate settings.

The high impedance O/P source replicates the average photodiode current for monitoring purposes. The IMON pin

can be also used to select between 1G and 10G operation. When the 1G mode is selected, the TIA output is

filtered to reduce the bandwidth to 1G levels and hence improve sensitivity. The device is in low rate mode for

Vmon greater than 1.6 V and in high rate mode for Vmon less than 1 V. The IMON feature can still be used under

the 1G and 10G operations.

Figure 3-2.

Implementation with M0217x

RMON

1.3V

M02139

MON

M0217x

+

-

BW_Sel

(high=10G)

10G Operation:

- RMON value selected to limit full-

scale voltage to <1V

- GPIO is set low

- AD_RxP in voltage mode

1G Operation:

- GPIO is set to an input (high-Z)

- AD_RxP is in current mode (input

voltage ~1.6V)