MCP3302 datasheet(15/40 Pages) MICROCHIP

15 / 40 page

 2002 Microchip Technology Inc.

DS21697B-page 15

MCP3302/04

4.0

PIN DESCRIPTIONS

The descriptions of the pins are listed in Table 4-1.

TABLE 4-1:

PIN FUNCTION TABLE

4.1

CH0-CH7

Analog input channels. These pins have an absolute

voltage range of VSS - 0.3V to VDD + 0.3V. The full scale

differential input range is defined as the absolute value

of (IN+) - (IN-). This difference can not exceed the

value of VREF - 1 LSB or digital code saturation will

occur.

4.2

DGND

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

Chip Select/Shutdown (CS/SHDN)

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

Serial Data Input (DIN)

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

Serial Data Output (DOUT)

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.

4.6

Serial Clock (CLK)

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

AGND

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

Voltage Reference (VREF)

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

VDD

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.

Name

Function

CH0-CH7

Analog Inputs

DGND

Digital Ground

CS/SHDN

Chip Select / Shutdown Input

DIN

Serial Data In

DOUT

Serial Data Out

CLK

Serial Clock

AGND

Analog Ground

VREF

Reference Voltage Input

VDD

+2.7V to 5.5V Power Supply

LSB Size =

2 x VREF

8192

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