Z-World Fox LP3500 User Manual - page 28

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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. Anything below this value is a 

logic 0, and anything above is a logic 1

.

Pulling the digital inputs to Vcc will in-

crease the current consumption by about 

300 µA for each digital input.

330 nF

100 k

W

22 k

W

Factory

Default

+K

GND

Vcc

0 

W

Rabbit 3000™

Microprocessor

Figure 10.  LP3500 Digital Input Protected 

Range

+40 V

+36 V

+3.3 V

–40 V

Normal Switching

Levels

Spikes

Digital Input V

oltage

Spikes

Spikes