Data Sheet

AD7687

Rev. E | Page 9 of 26

PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS

REF

1

VDD

2

IN+

3

IN–

4

GND

5

VIO

10

SDI

9

SCK

8

SDO

7

CNV

6

AD7687

TOP VIEW

(Not to Scale)

Figure 4. 10-Lead MSOP Pin Configuration

1

REF

2

VDD

3

IN+

4

IN–

5

GND

10 VIO

9SDI

8SCK

7SDO

6 CNV

NOTES

1. FOR THE LFCSP ONLY, THE EXPOSED

PADDLE MUST BE CONNECTED TO GND.

TOP VIEW

(Not to Scale)

AD7687

Figure 5. 10-Lead LFCSP Pin Configuration

Table 8. Pin Function Descriptions

Pin No.

Mnemonic

Function

1

REF

AI

Reference Input Voltage. The REF range is from 0.5 V to VDD, referred to the GND pin. Place a 10 μF

decoupling capacitor as close to the pin as possible.

2

VDD

P

Power Supply.

3

IN+

AI

Differential Positive Analog Input.

4

IN−

AI

Differential Negative Analog Input.

5

GND

P

Power Supply Ground.

6

CNV

DI

Convert Input. This input has multiple functions. On its leading edge, it initiates a conversion and selects

the interface mode: chain or CS (depending on the state of SDI). In CS mode, CNV enables the SDO pin

when low. In chain mode, the data is read while CNV is high.

7

SDO

DO

Serial Data Output. The conversion result is output on this pin. It is synchronized to SCK. SDO also acts as

the BUSY indicator if the feature is enabled.

8

SCK

DI

Serial Data Clock Input. This input primarily shifts data out on SDO when data is valid. In chain mode, the

state of SCK determines if the BUSY indicator feature is enabled. If SCK is low during the CNV rising edge,

the BUSY feature is disabled. If it is high during the CNV rising edge, the BUSY feature is enabled.

9

SDI

DI

Serial Data Input. This input serves multiple functions. It selects the interface mode of the ADC as follows:

Chain mode is selected if SDI is low during the CNV rising edge. In this mode, SDI is used as a data input to

daisy chain the conversion results of two or more ADCs onto a single SDO line. The digital data level on SDI

is output on SDO with a delay of 16 SCK cycles.

CS mode is selected if SDI is high during the CNV rising edge. In this mode, either SDI or CNV can enable

the serial output signals when low, and if SDI or CNV is low when the conversion is complete, the BUSY

indicator feature is enabled.

10

VIO

P

Input/Output Interface Digital Power. Nominally at the same supply as the host interface (1.8 V, 2.5 V, 3 V,

or 5 V).

EPAD

N/A

For the LFCSP only, the exposed paddle must be connected to GND.