Datasheet
MCP3221
DS21732D-page 12 2002-2013 Microchip Technology Inc.
3.0 PIN FUNCTIONS
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”, “Device Power and Layout
Considerations”, for tips on power and grounding.
3.2 Analog Input (A
IN
)
AIN 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”, “Driving the
Analog Input”. 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. Since it is an open-
drain terminal, the SDA bus requires a pull-up resistor
to V
DD
(typically 10 k for 100kHz and 2k for
400 kHz SCL clock speeds). Refer to Section 6.2
“Connecting to the I
2
C Bus”, “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”, “I
2
C Bus
Characteristics”.
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”, “Connect-
ing to the I
2
C Bus”).
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”, “Driving the Analog Input”.
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