MCP3221
DS21732C-page 12
2006 Microchip Technology Inc.
3.0
PIN FUNCTIONS
TABLE 3-1:
PIN FUNCTION TABLE
3.1
VDD and VSS
The VDD pin, with respect to VSS, provides power to the
device as well as a voltage reference for the conversion
Considerations”, for tips on power and grounding.
3.2
Analog Input (AIN)
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
Analog Input”. For proper conversions, the voltage on
this pin can vary from VSS to VDD.
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 VDD (typically 10 kΩ for 100 kHz and 2 kΩ for
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
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 VDD (typically 10 kΩ for 100 kHz and
2k
Ω for 400 kHz SCL clock speeds. Refer to
ing to the I2C 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
Input”, “Driving the Analog Input”.
Name
Function
VDD
+2.7V to 5.5V Power Supply
VSS
Ground
AIN
Analog Input
SDA
Serial Data In/Out
SCL
Serial Clock In