NUMICRO-SDK Nuvoton Technology Corporation of America, NUMICRO-SDK Datasheet - Page 487

• Manufacturer Part Number: NUMICRO-SDK
• Description: KIT EVAUATION NUC100/120/130/140
• Manufacturer: Nuvoton Technology Corporation of America
• Series: NuMicro™r
• Type: MCUr

Specifications of NUMICRO-SDK

• Contents: Board, Cable, CD, Nu-Link
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: NUC100, NUC120, NUC130, NUC140

5.16.4 Functional Description
5.16.4.1 Self-Calibration
5.16.4.2 ADC Clock Generator
The A/D converter operates by successive approximation with 12-bit resolution. This A/D
converter equips with self calibration function to minimum conversion error, user can write 1 to
CALEN bit in ADCALR register to enable calibration function, while internal calibration is finish the
CAL_DONE bit will assert. The ADC has three operation modes: single mode, single-cycle scan
mode and continuous scan mode. When changing the operating mode or analog input channel
enable, in order to prevent incorrect operation, software must clear ADST bit to 0 in ADCR
register.
When chip power on or switch ADC input type between single-end input and differential input, it
needs to do ADC self calibration to minimize the conversion error. User can write 1 to CALEN bit
in ADCALR register to enable self calibration. The operation is process internally and it needs 127
ADC clocks to complete calibration. After CALEN is set to 1, software must wait CAL_DONE bit
set by internal hardware. The detail timing is shown as below:
The maximum sampling rate is up to 600K SPS. The ADC engine has three clock sources
selected by 2-bit ADC_S (CLKSEL[3:2]), the ADC clock frequency is divided by an 8-bit prescaler
with the formula:
The ADC clock frequency = (ADC clock source frequency) / (ADC_N+1);
where the 8-bit ADC_N is located in register CLKDIV[23:16].
In generally, software can set ADC_S and ADC_N to get 16MHz or slightly less.
Because the Bandgap voltage source lacks the driving capability, a conversion rate lower than 15
kHz (@5V) is recommended.
CAL_DONE
ADC_CLK
NuMicro™ NUC100 Series Technical Reference Manual
CAL_EN
Figure 5-95 ADC Converter Self-Calibration Timing Diagram
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Publication Release Date: Oct 22, 2010
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Revision V1.06