TN0900 STMICROELECTRONICS | Alldatasheet
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Technical content
June 2012 Doc ID 023288 Rev 1 1/5 TN0900 Technical note Interfacing STM8T143 output in open-drain mode Introduction This application note provides guidelines on how to interface the STM8T143 in output open- drain active-low mode. Refer to the STM8T143 datasheet for a full description of signals, device operation and electrical characteristics.
As a result, the device input pin electrical characteristics, should comply with the following conditions: In addition, the device minimum input high level voltage (VIHmin_DEVICE) should meet the equation below: where: ILKGmax is the STM8T143 maximum leakage current (see the datasheet current characteristics table). IDI is the device input current. Example Below is an example of voltage adaptation between an STM8T143 powered from a 3.3 V supply and a device input powered from 1.8 V: If Rpull-up = 10 kΩ, and device VDD_DEVICE = 1.8 V, since the current sunk by the output pin (IIO) = 1 mA for a specified VOL value, then This current value is well below the 1 mA maximum output current sunk by the STM8T143. As a result, an Rpull-up of 10 kΩ and a device VDD of 1.8 V are fully compliant with the maximum limit of the current sunk by the STM8T143 output pin. At 2 V, VOLmax_STM8T143 = 0.07 V. The device input pin electrical characteristics should consequently comply with the condition below: If the device input current IDI = 200nA, then which gives: VILmax_DEVICE VOLmax_STM8T143> VIHmin_DEVICE VDD_DEVICE Rpull-up ILKGmax IDI+()×()–< 1.8 VILmax_DEVICE 0.07V> VIHmin_DEVICE VDD_DEVICE Rpull-up 10 6– 100 9– 2×+()×()–< VIHmin_DEVICE 1.788V<
Revision history
Table 1. Document revision history 25-Jun-2012 0.1 Initial release.