User Manual

2
Installation
40
CrossCheck CDPD Mobile Unit Manual
2.9.6
Inputs (IP0 to IP3)
The CrossCheck CDPD supports four discrete inputs. The circuit
diagram is shown in Figure 2.19.
Figure 2.19 Input Circuit Diagram
Each input floats to a logic-high state (inactive) when left open.
Grounding an input causes a logic-low state (active). The
CrossCheck CDPD can be configured to detect either logic-high or
logic-low states at the inputs whenever the unit is powered on.
Note – When the CrossCheck CDPD is powered off or in Power
Management mode, it can only detect a logic-low (grounded) input.
The discrete inputs are compatible with properly connected relays and
switches or with standard 3.3 VDC logic levels. A properly connected
relay or switch allows the input to float high in one position and
grounds the input in the other position.
Input Logic High:
Open circuit or V
in
> 2.4 VDC
Input Logic Low:
V
in
< 0.6 VDC
The inputs must remain in either state for at least
200 milliseconds before the CrossCheck CDPD
detects the input.
Input Current (Max)
I
in
< 3 mA
1 mA is typical at 12 VDC.
Input Protection:
Protected up to at least V
Batt
continuous
3K
330K
0.1µF
To logic
470pf
Input
100K
3.3V/10m/A