Wiring Digital Inputs - TomTom LINK 530 Installation Manual

Wiring digital inputs

The digital inputs of the LINK 530 operate according to the principle of a voltage detector. Voltag-
es below 2 Volts are definitively interpreted as being low and voltages higher than 3 Volts are
definitively interpreted as being high. The maximum permissible input voltage is 30 Volts.
Low/high switching (increasing input voltage) typically occurs at 2.8 Volts. High/low switching
(decreasing input voltage) typically occurs at 2.1 Volts. The hysteresis of 0.7 Volts is to avoid rapid
switching.
Interference voltages at the digital inputs must remain below 2 Volts. In order to guarantee this,
the input wire of the connecting cable should never remain unconnected. If a digital input is not
being used, the input wire must be connected to ground (GND). To evaluate a switch, this switch
needs to be designed as a change-over switch, switching the digital input between plus and minus
(ground GND) of the vehicle electrical system voltage (+9 ... 30V).
If no change-over switch is available, an electric load for example, indicator light or resistor,
between the digital input and ground (GND) or between the digital input and the vehicle voltage
(+9 ... 30V) can offer defined levels.
When using inductive loads, a free-wheeling diode must be used in parallel with the load.
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