Cautions Related To 10-Bit A/D Converter; How To Reduce Current Consumption In Standby Mode - NEC PD789488 User Manual

10.5 Cautions Related to 10-Bit A/D Converter

(1) Current consumption in standby mode
In standby mode, the A/D converter stops operation. Clearing bit 7 (ADCS0) and bit 0 (ADCE0) of A/D
converter mode register 0 (ADML0) to 0 can reduce the current consumption.
Figure 10-7 shows how to reduce the current consumption in standby mode.
Figure 10-7. How to Reduce Current Consumption in Standby Mode
(2) Input range for pins ANI0 to ANI7
Be sure to keep the input voltage at ANI0 to ANI7 within the rating. If a voltage greater than or equal to AV
or less than or equal to AV
the conversion output of the channel becomes undefined, which may affect the conversion output of the other
channels.
(3) Conflict
<1> Conflict between writing to A/D conversion result register 0 (ADCRL0) at the end of conversion and
reading from ADCRL0 using instruction
Reading from ADCRL0 takes precedence. After reading, the new conversion result is written to ADCRL0.
<2> Conflict between writing to ADCRL0 at the end of conversion and writing to A/D converter mode register 0
(ADML0) or analog input channel specification register 0 (ADS0)
Writing to ADML0 or ADS0 takes precedence. ADCRL0 is not written to. No A/D conversion end
interrupt request signal (INTAD0) is generated.
(4) Conversion result immediately after start of A/D conversion
If the band-gap circuit is not used (ADCE0 = 0) or conversion is started before 14
the setting of ADCE, only the first A/D conversion value immediately after A/D conversion has been started is
undefined. Poll the A/D conversion end interrupt request (INTAD0), drop the first conversion result and use
the second and subsequent conversion results. When 14
band-gap circuit (ADCE0 = 1), the first conversion value is normal.
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CHAPTER 10 10-BIT A/D CONVERTER
AV
REF
P-ch
Series resistor string
V
SS
0: Stopped
1: Operating
Band-gap circuit
(even within the absolute maximum ratings) is input into a conversion channel,
SS
User's Manual U15331EJ4V1UD
ADCS0
ADCE0
µ
s has elapsed following
µ
s have elapsed following the activation of the
DD