The OP4520 can hold any combination of four of the following Type B mezzanines. The standard configuration contains one of each.

32 Digital In (OP5353)

Number of channels	32 digital inputs
Isolation	Optical isolator
Connection mode	Anode and cathode available on the connector
Input current	3.6 mA, current limiting diode
Reverse voltage protection	Schottky diode
Maximum reverse voltage protection	30 Volts
Detection threshold	Separate Schmitt Trigger
Voltage range	4 to 50 Vdc

32 Digital Out (OP5360-2)

Number of channels	32 digital outputs 2 banks of 16, fully isolated and independent of each other
Isolation	Galvanic isolator
Output Protection	50 mA resettable fuse
Protection thresholds	Overvoltage: 30.1V Reverse voltage: maximum of 30 V.
Output Voltage range	5 to 30 Vdc max
Output configuration	Push-pull, tri-state output

Number of channels	6 differential outputs
High level (With load) Low level (With load)	2.5 V min @ -20 mA 0.5 V max @ 20 mA
Voltage range	5 Vdc
Delay Low-to-High	55 ns