st10f273m STMicroelectronics, st10f273m Datasheet - Page 71

• Manufacturer Part Number: st10f273m
• Description: 16-bit Mcu With 512 Kbyte Flash Memory And 36 Kbyte Ram
• Manufacturer: STMicroelectronics

ST10F273M
14
A/D converter
A 10-bit A/D converter with 24 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 ST10F273M has 16 + 8 multiplexed input channels on Port 5 and Port 1 respectively.
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
characteristics
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 depends also on other
causes), in worst case of temperature and process, the maximum frequency for a sine wave
analog signal is around 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 a static signal is applied during the sampling phase, a series resistance shall not be
greater than 20kΩ (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 rning channel inputs can be used as digital input port pins.
The A/D converter of the ST10F273M supports different conversion modes:
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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
register.
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
register.
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
for details.
Section 24: Electrical
A/D converter
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