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19 12-BIT A/D CONVERTER (ADC12A)
19.2 Input Pins and External Connections
19.2.1 List of Input Pins
Table 19.2.1.1 lists the ADC12A pins.
Pin name
I/O*
ADINnm
A
#ADTRGn
I
VREFAn
A
If the port is shared with the ADC12A pin and other functions, the ADC12A input function must be assigned to the
port before activating the ADC12A. For more information, refer to the "I/O Ports" chapter.
19.2.2 External Connections
Figure 19.2.2.1 shows a connection diagram between the ADC12A and external devices.
S1C31 ADC12A
Figure 19.2.2.1 Connections between ADC12A and External Devices
19.3 Clock Settings
19.3.1 ADC12A Operating Clock
The 16-bit timer Ch.k operating clock CLK_T16_k is also used as the ADC12A operating clock. For more informa-
tion on the CLK_T16_k settings and clock supply in SLEEP and DEBUG modes, refer to "Clock Settings" in the
"16-bit Timers" chapter.
Note: When the CLK_T16_k supply stops during A/D conversion (e.g., when the CPU enters SLEEP
or DEBUG mode), correct conversion results cannot be obtained even if the clock supply is re-
sumed after that. In this case, perform A/D conversion again.
19.3.2 Sampling Time
The ADC12A includes a sample and hold circuit. The sampling time must be set so that it will satisfy the time re-
quired for acquiring input voltage (t
input portion.
R
S
19-2
Table 19.2.1.1 List of ADC12A Pins
Initial status*
Hi-Z
Analog signal input
I
External trigger input
Hi-Z
Reference voltage input
* Indicates the status when the pin is configured for the ADC12A.
V
DD
VREFAn
Sensor output
ADINn0
detection
Battery voltage
ADINnm
detection
: acquisition time). Figure 19.3.2.1 shows an equivalent circuit of the analog
ACQ
V
DD
ADINnm
V
SS
Figure 19.3.2.1 Equivalent Circuit of Analog Input Portion
Seiko Epson Corporation
Function
DC-DC
converter
Sensor
R
ADIN
C
ADIN
R
:
Source impedance
S
R
: Analog input resistance
ADIN
C
: Analog input capacitance
V
ADIN
SS
3.3 V
S1C31D50/D51 TECHNICAL MANUAL
(Rev. 2.00)
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