Datasheet

 2002-2017 Microchip Technology Inc. DS20001732E-page 13
MCP3221
3.0 PIN FUNCTIONS
Table 3-1 lists the function of the pins.
TABLE 3-1: PIN FUNCTION TABLE
3.1 V
DD
and V
SS
The V
DD
pin, with respect to V
SS
, provides power to the
device as well as a voltage reference for the conversion
process. Refer to Section 6.4 “Device Power and
Layout Considerations” for tips on power and
grounding.
3.2 Analog Input (A
IN
)
A
IN
is the input pin to the sample and hold circuitry of
the Successive Approximation Register (SAR) con-
verter. Care should be taken in driving this pin. Refer to
Section 6.1 “Driving the Analog Input” for more
information. For proper conversions, the voltage on this
pin can vary from V
SS
to V
DD
.
3.3 Serial Data (SDA)
SDA is a bidirectional pin used to transfer addresses
and data into and out of the device. It is an open-drain
terminal, therefore, the SDA bus requires a pull-up
resistor to V
DD
(typically 10 k for 100 kHz and 2 k
for 400 kHz SCL clock speeds). Refer to Section 6.2
“Connecting to the I
2
C Bus” for more information.
For normal data transfer, SDA is allowed to change only
during SCL low. Changes during SCL high are reserved
for indicating the Start and Stop conditions. Refer to
Section 5.1 “I
2
C Bus Characteristics” for more infor-
mation.
3.4 Serial Clock (SCL)
SCL is an input pin used to synchronize the data trans-
fer to and from the device on the SDA pin and is an
open-drain terminal. Therefore, the SCL bus requires a
pull-up resistor to V
DD
(typically 10 k for 100 kHz and
2k for 400 kHz SCL clock speeds. Refer to
Section 6.2 “Connecting to the I
2
C Bus” for more
information.
For normal data transfer, SDA is allowed to change
only during SCL low. Changes during SCL high are
reserved for indicating the Start and Stop conditions.
Refer to Section 6.1 “Driving the Analog Input” for
more information.
Name Function
V
DD
+2.7V to 5.5V Power Supply
V
SS
Ground
A
IN
Analog Input
SDA Serial Data In/Out
SCL Serial Clock In