MCP3301T datasheet(13/38 Pages) MICROCHIP

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 2011 Microchip Technology Inc.

DS21700D-page 13

MCP3301

3.0

PIN DESCRIPTIONS

The descriptions of the pins are listed in Table 3-1.

TABLE 3-1:

PIN FUNCTION TABLE

3.1

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 by 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

the

manufacturer’s recommendations for circuit layout.

Any instability in the operation of the reference device

will have a direct effect on the accuracy of the ADC

conversion results.

3.2

Positive Analog Input (IN+)

This pin has an absolute voltage range of VSS-0.3V to

VDD+0.3V. The full scale input range is defined as the

absolute value of (IN+) - (IN-).

3.3

Negative Analog Input (IN-)

This pin has an absolute voltage range of VSS-0.3V to

VDD+0.3V. The full scale input range is defined as the

absolute value of (IN+) - (IN-).

3.4

Ground Connection (VSS)

analog

ground

plane

available,

recommended that this device be tied to the analog

ground plane in the circuit. See Section 5.6 “Layout

Considerations”, for more information regarding

circuit layout.

3.5

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

conversion 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

multiple

conversions.

See

Figure 6-2

for

serial

communication protocol.

3.6

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 6-2 for serial communication

protocol.

3.7

Serial Clock (CLK)

The SPI clock pin is used to initiate a conversion, as

well as to clock out each bit of the conversion as it takes

place. See Section 5.2 “Driving the Analog Input”

for constraints on clock speed, and Figure 6-2 for serial

communication protocol.

3.8

Power Supply (VDD)

The device can operate from 2.7V to 5.5V, but the

performance is applicable from a 4.5V to 5.5V supply

range. To ensure accuracy, a 0.1 µF ceramic bypass

capacitor should be placed as close as possible to the

pin. See Section 5.6 “Layout Considerations” for

more information regarding circuit layout.

MSOP, PDIP,

SOIC

Name

Function

1VREF

Reference Voltage Input

IN(+)

Positive Analog Input

IN(-)

Negative Analog Input

4VSS

Ground

5CS/SHDN

Chip Select / Shutdown Input

6DOUT

Serial Data Out

CLK

Serial Clock

8VDD

+4.5V to 5.5V Power Supply

LSB Size =

2 x VREF

8192

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