5.4 Multi-purpose inputs and outputs
70 Acqiris SA220P User's Manual
Direction Low level High level
Input < 0.8 V > 2.0 to 3.45 V
Output In the range 0 to 0.8 V In the range 1.6 to 3.3 V
Table 5.4 - Logic levels.
As an Input
The input is high-impedance and will be pulled high if unconnected via an internal weak pull-up (10 k
pull-up resistor).
Figure 5.3 - Programmable IO schematic
As an Output
The high level output will typically give 1.6 V into 50 Ω. As can be seen in the diagram below, the 3.3
V output buffer has a 50 Ω resistor in series. Therefore the available output high level voltage will
depend on the load applied. In the example below a 50 Ω termination will result in a nominal high
level of 1.6 V.
(Vo = (Rload/(50 + Rload)) * 3.3).
Figure 5.4 - Output equivalent circuit.
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