Rabbit Fox LP3500, User Manual, Page: 28 / 143

22 Fox (LP3500)
3.3 Digital I/O
3.3.1 Digital Inputs
The LP3500 has 16 digital inputs, IN00–IN15. The inputs are factory-configured to be
pulled up to +K in banks of eight, but they can also be pulled up to Vcc or down to 0 V in
banks of eight by changing a surface-mounted 0
Ω
resistor as shown in Figure 9.
Figure 9. LP3500 Digital Inputs [Pulled Up—Factory Default]
The digital inputs are each fully protected
over a range of 0 V to +36 V, and can handle
short spikes of ±40 V. The actual switching
threshold is approximately 1.40 V. Any-
thing below this value is a logic 0, and any-
thing above is a logic 1
.
Pulling the digital inputs to Vcc will
increase the current consumption by about
300 µA for each digital input.
Figure 10. LP3500 Digital Input Protected
Range
330 nF
100 k W
22 k W
Factory
Default
+K
GND
Vcc
0 W
Rabbit 3000®
Microprocessor
+40 V
+36 V
+3.3 V
–40 V
Normal Switching
Levels
Spikes
Digital Input V
oltage
Spikes
Spikes