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AD7782
(Rev.:Rev0)

Read Only, Pin Configured 24-Bit Σ-Δ ADC

Analog Devices 

AD7782

PIN CONFIGURATION

XTAL1 1

16 XTAL2

REFIN(+) 2

15 VDD

REFIN(–) 3

14 GND

AIN1(+) 4 AD7782 13 MODE

AIN1(–)

5

TOP VIEW

(Not to Scale)

12

DOUT/RDY

AIN2(+) 6

11 CS

AIN2(–) 7

10 SCLK

CH1/CH2 8

9 RANGE

PIN FUNCTION DESCRIPTIONS

Pin No. Mnemonic Function

1

XTAL1

Input to the 32.768 kHz Crystal Oscillator Inverter.

2

REFIN(+) Positive Reference Input. REFIN(+) can lie anywhere between VDD and GND +1 V. The nominal reference

voltage (REFIN(+) – REFIN(–)) is 2.5 V, but the part functions with a reference from 1 V to VDD.

3

REFIN(–) Negative Reference Input. This reference input can lie anywhere between GND and VDD – 1 V.

4

AIN1(+) Analog Input. AIN1(+) is the positive terminal of the fully-differential analog input pair AIN1(+)/AIN1(–).

5

AIN1(–)

Analog Input. AIN1(–) is the negative terminal of the fully-differential analog input pair AIN1(+)/AIN1(–).

6

AIN2(+) Analog Input. AIN2(+) is the positive terminal of the fully-differential analog input pair AIN2(+)/AIN2(–).

7

AIN2(–)

Analog Input. AIN2(–) is the negative terminal of the fully-differential analog input pair AIN2(+)/AIN2(–).

8

CH1/CH2 Channel Select, Logic Input. With CH1/CH2 = 0, channel AIN1(+)/AIN1(–) is selected while the active

channel is AIN2(+)/AIN2(–) when CH1/CH2 = 1.

9

RANGE

Logic Input which configures the input range on the internal PGA. With RANGE = 0, the full-scale input

range is ± 160 mV while the full-scale input range equals ± 2.56 V when RANGE = 1 for a +2.5 V Reference.

10

SCLK

Serial Clock Input/Output for Data Transfers from the ADC. When the device is operated in master mode,

SCLK is an output with one SCLK period equal to one XTAL period. In slave mode, SCLK is generated

by an external source. In slave mode, all the data can be transmitted on a continuous train of pulses.

Alternatively, SCLK can be a noncontinuous clock with the information being transmitted from the AD7782

in smaller batches of data. SCLK is Schmitt triggered (slave mode) making the interface suitable for opto-

isolated applications.

11

CS

Chip Select Input. CS is an active low logic input used to select the AD7782. When CS is low, the PLL

establishes lock and allows the AD7782 to initiate a conversion on the selected channel. When CS is high,

the conversion is aborted, DOUT and SCLK are three-stated, the AD7782 enters standby mode and any

conversion result in the output shift register is lost.

12

DOUT/RDY Serial Data Output/Data Ready Output. DOUT/RDY serves a dual purpose in this interface. When a con-

version is initiated, DOUT/RDY goes high and remains high until the conversion is complete. DOUT/RDY

will then return low to indicate that valid data is available to be read from the device. In slave mode, this acts

as an interrupt to the processor indicating that valid data is available. If data is not read after a conversion,

DOUT/RDY will go high before the next update occurs. In master mode, DOUT/RDY goes low for at least

half an SCLK cycle before the device produces SCLKs. When SCLK becomes active, data is output on

the DOUT/RDY pin. Data is output on the falling SCLK edge and is valid on the rising edge.

13

MODE

The MODE pin selects master or slave mode of operation. When MODE = 0, the AD7782 operates in

master mode while the AD7782 is configured for slave mode when MODE = 1.

14

GND

Ground Reference Point for the AD7782.

15

VDD

Supply Voltage, 3 V or 5 V Nominal.

16

XTAL2

Output from the 32.768 kHz Crystal Oscillator Inverter.

–6–

REV. 0

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