STM32F042F4 datasheet(81/117 Pages) STMICROELECTRONICS

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STM32F042x4 STM32F042x6

Electrical characteristics

Figure 26. ADC accuracy characteristics

Figure 27. Typical connection diagram using the ADC

1. Refer to Table 54: ADC characteristics for the values of RAIN, RADC and CADC.

2. Cparasitic represents the capacitance of the PCB (dependent on soldering and PCB layout quality) plus the

pad capacitance (roughly 7 pF). A high Cparasitic value will downgrade conversion accuracy. To remedy

this, fADC should be reduced.

General PCB design guidelines

Power supply decoupling should be performed as shown in Figure 13: Power supply

scheme

. The 10 nF capacitor should be ceramic (good quality) and it should be placed as

close as possible to the chip.

2. ADC Accuracy vs. Negative Injection Current: Injecting negative current on any of the standard (non-robust) analog input

pins should be avoided as this significantly reduces the accuracy of the conversion being performed on another analog

input. It is recommended to add a Schottky diode (pin to ground) to standard analog pins which may potentially inject

negative current.

Any positive injection current within the limits specified for IINJ(PIN) and ΣIINJ(PIN) in Section 6.3.14 does not affect the ADC

accuracy.

3. Better performance may be achieved in restricted VDDA, frequency and temperature ranges.

4. Data based on characterization results, not tested in production.

STM32F042F4 Datasheet(PDF) 81 Page - STMicroelectronics