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20 12-BIT A/D CONVERTER (ADC12A)
20.2 Input Pins and External Connections
20.2.1 List of Input Pins
Table 20.2.1.1 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.
20.2.2 External Connections
Figure 20.2.2.1 shows a connection diagram between the ADC12A and external devices.
S1C17 ADC12A
Figure 20.2.2.1 Connections between ADC12A and External Devices
20.3 Clock Settings
20.3.1 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.
20.3.2 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
20-2
Table 20.2.1.1 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
2.5 V output
VREFAn
Sensor output
ADINn0
detection
Battery voltage
ADINnm
detection
: acquisition time). Figure 20.3.2.1 shows an equivalent circuit of the analog
ACQ
V
DD
ADINnm
V
SS
Figure 20.3.2.1 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
S1C17W14/W16 TECHNICAL MANUAL
(Rev. 1.2)
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