AD7705/AD7706
PIN CONFIGURATIONS
SCLK
1
MCLK IN
2
MCLK OUT
3
CS
4
16
GND
15
V
DD
14
DIN
SCLK
1
MCLK IN
2
MCLK OUT
3
CS
4
16
GND
15
V
DD
14
DIN
AD7705
13
DOUT
TOP VIEW
RESET
5
(Not to Scale)
12
DRDY
AIN2(+)
6
AIN1(+)
7
AIN1(–)
8
11
AIN2(–)
10
REF IN(–)
9
AD7706
13
DOUT
TOP VIEW
RESET
5
(Not to Scale)
12
DRDY
AIN1
6
AIN2
7
COMMON
8
11
AIN3
10
REF IN(–)
9
REF IN(+)
REF IN(+)
PIN FUNCTION DESCRIPTIONS
Pin No.
1
Mnemonic
SCLK
Function
Serial Clock. Schmitt-Triggered Logic Input. An external serial clock is applied to this input
to access serial data from the AD7705/AD7706. This serial clock can be a continuous clock
with all data transmitted in a continuous train of pulses. Alternatively, it can be a noncon-
tinuous clock with the information being transmitted to the AD7705/AD7706 in smaller
batches of data.
Master Clock signal for the device. This can be provided in the form of a crystal/resonator or
external clock. A crystal/resonator can be tied across the MCLK IN and MCLK OUT pins.
Alternatively, the MCLK IN pin can be driven with a CMOS-compatible clock and MCLK
OUT left unconnected. The part can be operated with clock frequencies in the range
500 kHz to 5 MHz.
When the master clock for the device is a crystal/resonator, the crystal/resonator is connected
between MCLK IN and MCLK OUT. If an external clock is applied to MCLK IN, MCLK
OUT provides an inverted clock signal. This clock can be used to provide a clock source for
external circuitry and is capable of driving one CMOS load. If the user does not require it,
this MCLK OUT can be turned off via the CLK DIS bit of the Clock Register. This ensures
that the part is not burning unnecessary power driving capacitive loads on MCLK OUT.
Chip Select. Active low Logic Input used to select the AD7705/AD7706. With this input
hard-wired low, the AD7705/AD7706 can operate in its three-wire interface mode with
SCLK, DIN and DOUT used to interface to the device.
CS
can be used to select the device
in systems with more than one device on the serial bus or as a frame synchronization signal in
communicating with the AD7705/AD7706.
Logic Input. Active low input that resets the control logic, interface logic, calibration
coefficients, digital filter and analog modulator of the part to power-on status.
AD7705: Positive input of the differential Analog Input Channel 2. AD7706: Analog Input
Channel 1.
AD7705: Positive input of the differential Analog Input Channel 1. AD7706: Analog Input
Channel 2.
AD7705: Negative input of the differential Analog Input Channel 1. AD7706: COMMON
Input. Analog inputs for Channels 1, 2 and 3 are referenced to this input.
Reference Input. Positive input of the differential Reference Input to the AD7705/AD7706.
The reference input is differential with the provision that REF IN(+) must be greater than
REF IN(–). REF IN(+) can lie anywhere between V
DD
and GND.
2
MCLK IN
3
MCLK OUT
4
CS
5
6
7
8
9
RESET
AIN2(+)[AIN1]
AIN1(+)[AIN2]
AIN1(–)[COMMON]
REF IN(+)
–6–
REV. A
AD [ ANALOG DEVICES ]
