MCP3304 Microchip Technology, MCP3304 Datasheet - Page 15

• Manufacturer Part Number: MCP3304
• Description: 13-Bit Differential Input, Low Power A/D Converter with SPI Serial Interface
• Manufacturer: Microchip Technology

4.0
The descriptions of the pins are listed in Table 4-1.
TABLE 4-1:
4.1
Analog input channels. These pins have an absolute
voltage range of V
differential input range is defined as the absolute value
of (IN+) - (IN-). This difference can not exceed the
value of V
occur.
4.2
Ground connection to internal digital circuitry. To
ensure accuracy this pin must be connected to the
same ground as AGND. If an analog ground plane is
available, it is recommended that this device be tied to
the analog ground plane in the circuit. See Section 6.6
for more information regarding circuit layout.
4.3
The CS/SHDN pin is used to initiate communication
with the device when pulled low. This pin will end a con-
version and put the device in low power standby when
pulled high. The CS/SHDN pin must be pulled high
between conversions and cannot be tied low for multi-
ple conversions. See Figure 7-2 for serial communica-
tion protocol.
4.4
The SPI port serial data input pin is used to clock in
input channel configuration data. Data is latched on the
rising edge of the clock. See Figure 7-2 for serial com-
munication protocol.
4.5
The SPI serial data output pin is used to shift out the
results of the A/D conversion. Data will always change
on the falling edge of each clock as the conversion
takes place. See Figure 7-2 for serial communication
protocol.
© 2007 Microchip Technology Inc.
CH0-CH7
DGND
CS/SHDN
D
D
CLK
AGND
V
V
REF
DD
IN
OUT
Name
PIN DESCRIPTIONS
CH0-CH7
DGND
Chip Select/Shutdown (CS/SHDN)
Serial Data Input (D
Serial Data Output (D
REF
Digital Ground
Chip Select / Shutdown Input
Serial Data In
Serial Data Out
Serial Clock
Analog Ground
Reference Voltage Input
+2.7V to 5.5V Power Supply
Analog Inputs
- 1 LSB or digital code saturation will
SS
PIN FUNCTION TABLE
- 0.3V to V
Function
DD
+ 0.3V. The full scale
IN
)
OUT
)
4.6
The SPI clock pin is used to initiate a conversion and to
clock out each bit of the conversion as it takes place.
See Section 6.2 for constraints on clock speed. See
Figure 7-2 for serial communication protocol.
4.7
Ground connection to internal analog circuitry. To
ensure accuracy, this pin must be connected to the
same ground as DGND. If an analog ground plane is
available, it is recommended that this device be tied to
the analog ground plane in the circuit. See Section 6.6
for more information regarding circuit layout.
4.8
This input pin provides the reference voltage for the
device, which determines the maximum range of the
analog input signal and the LSB size.
The LSB size is determined according to the equation
shown below. As the reference input is reduced, the
LSB size is reduced accordingly.
EQUATION
When using an external voltage reference device, the
system designer should always refer to the manufac-
turer’s recommendations for circuit layout. Any instabil-
ity in the operation of the reference device will have a
direct effect on the accuracy of the ADC conversion
results.
4.9
The voltage on this pin can range from 2.7 to 5.5V. To
ensure accuracy, a 0.1 μF ceramic bypass capacitor
should be placed as close as possible to the pin. See
Section 6.6 for more information regarding circuit lay-
out.
Serial Clock (CLK)
AGND
Voltage Reference (V
V
DD
LSB Size =
MCP3302/04
2 x V
8192
REF
DS21697C-page 15
REF
)