ST10F272M datasheet(66/175 Pages) STMICROELECTRONICS

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A/D converter

ST10F272M

66/176

A/D converter

A 10-bit A/D converter with 16+8 multiplexed input channels and a sample and hold circuit is

integrated on-chip. An automatic self-calibration adjusts the A/D converter module to

process parameter variations at each reset event. The sample time (for loading the

capacitors) and the conversion time is programmable and can be adjusted to the external

circuitry.

The ST10F272M has 16+8 multiplexed input channels on Port 5 and Port 1. The selection

between Port 5 and Port 1 is made via a bit in an XBus register. Refer to the User Manual for

a detailed description.

A different accuracy is guaranteed (Total Unadjusted Error) on Port 5 and Port 1 analog

channels (with higher restrictions when overload conditions occur); in particular, Port 5

channels are more accurate than the Port 1 channels. Refer to Section 24: Electrical

characteristics for details.

The A/D converter input bandwidth is limited by the achievable accuracy: supposing a

maximum error of 0.5LSB (2mV) impacting the global TUE (TUE also depends on other

causes), in worst case of temperature and process, the maximum frequency for a sine wave

analog signal is approximately 7.5 kHz. Of course, to reduce the effect of the input signal

variation on the accuracy down to 0.05LSB, the maximum input frequency of the sine wave

must be reduced to 800 Hz.

If static signal is applied during sampling phase, series resistance must not be greater than

20k

Ω (this taking into account eventual input leakage). It is suggested to not connect any

capacitance on analog input pins, in order to reduce the effect of charge partitioning (and

consequent voltage drop error) between the external and the internal capacitance: in case

an RC filter is necessary the external capacitance must be greater than 10nF to minimize

the accuracy impact.

Overrun error detection / protection is controlled by the ADDAT register. Either an interrupt

request is generated when the result of a previous conversion has not been read from the

result register at the time the next conversion is complete, or the next conversion is

suspended until the previous result has been read. For applications which require less than

16+8 analog input channels, the remaining channel inputs can be used as digital input port

pins.

The A/D converter of the ST10F272M supports different conversion modes:

●

Single channel single conversion: The analog level of the selected channel is

sampled once and converted. The result of the conversion is stored in the ADDAT

●

Single channel continuous conversion: The analog level of the selected channel is

repeatedly sampled and converted. The result of the conversion is stored in the ADDAT

●

Auto scan single conversion: The analog level of the selected channels are sampled

once and converted. After each conversion the result is stored in the ADDAT register.

The data can be transferred to the RAM by interrupt software management or using the

powerful Peripheral Event Controller (PEC) data transfer.

●

Auto scan continuous conversion: The analog level of the selected channels are

repeatedly sampled and converted. The result of the conversion is stored in the ADDAT

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