The datasheet for STM32H745xI does not give the value for R_ADC. Where can it be found?

[MRoss.4]

The datasheet for the STM32H745xI (doc DS12923 Rev 1) states in the notes to Figure 43 (p 191) that the value for R_ADC can be found in Table 96, but it is not given in Table 96. I also cannot find it elsewhere in the datasheet. Where can the value of R_ADC be found?

[DTomi.1]

You're correct, only the maximum external input impedance (R_AIN) is shown. However you may estimate the sampling switch resistance (R_ADC) using R_AIN and internal S/H capacitance (C_ADC) using the following expression:

One thing to note is that R_AIN for the STM32H745xI/G is determined using the following tolerances: "The tolerance is 10 LSBs for 16-bit resolution, 4 LSBs for 14-bit resolution, and 2 LSBs for 12-bit, 10-bit and 8-bit resolutions."

[Imen.D · Accepted solution]

Hello @MRoss.4​ 

Let me first welcome you to the Community 🙂

Here are the R_ADC values related to STM32H7 series:

• Channel Slow: 940 Ohm
• Channel fast: 450 Ohm
• Channel Direct 204 Ohm

Please feel free to come back to me if you need any other information.

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Imen