Data Sheet

AD7440/AD7450A

Rev. D | Page 9 of 27

PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS

Figure 5. Pin Configuration for 8-Lead SOT-23

Figure 6. Pin Configuration for 8-Lead MSOP

Table 5. Pin Function Descriptions

Mnemonic

Function

V

REF

Reference Input for the AD7440/AD7450A. An external reference must be applied to this input. For a 5 V power supply, the

reference is 2.5 V (±1%) for specified performance. For a 3 V power supply, the reference is 2 V (±1%) for specified

performance. This pin should be decoupled to GND with a capacitor of at least 0.1 µF. See the Reference section for more

details.

V

IN+

Positive Terminal for Differential Analog Input.

V

IN–

Negative Terminal for Differential Analog Input.

GND

Analog Ground. Ground reference point for all circuitry on the AD7440/AD7450A. All analog input signals and any external

reference signal should be referred to this GND voltage.

CS

Chip Select. Active low logic input. This input provides the dual function of initiating a conversion on the AD7440/AD7450A

and framing the serial data transfer.

SDATA

Serial Data. Logic output. The conversion result from the AD7440/AD7450A is provided on this output as a serial data stream.

The bits are clocked out on the falling edge of the SCLK input. The data stream of the AD7450A consists of four leading zeros

followed by the 12 bits of conversion data, which are provided MSB first; the data stream of the AD7440 consists of four

leading zeros, followed by the 10 bits of conversion data, followed by two trailing zeros. In both cases, the output coding is

twos complement.

SCLK

Serial Clock. Logic input. SCLK provides the serial clock for accessing data from the part. This clock input is also used as the

clock source for the conversion process.

V

DD

Power Supply Input. V

a 10 µF tantalum capacitor in parallel.

GND

8

7

6

5

SCLK

2

SDATA

3

CS

4

AD7440/

AD7450A

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SCLK

SDATA

CS

8

7

6

5

AD7440/

AD7450A

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(Not to Scale)