Data Sheet AD7887
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
CS
1
V
DD
2
GND
3
AIN1/V
REF
4
SCLK
8
DOUT
7
DIN
6
AIN0
5
AD7887
TOP VIEW
(Not to Scale)
06191-003
CS
1
V
DD
2
GND
3
AIN1/V
REF
4
SCLK
8
DOUT
7
DIN
6
AIN0
5
AD7887
TOP VIEW
(Not to Scale)
06191-004
Figure 3. SOIC_N Pin Configuration Figure 4. MSOP Pin Configuration
Table 4. Pin Function Descriptions
Pin No. Mnemonic Description
1
CS
Chip Select. Active low logic input. This input provides the dual function of initiating conversions on the AD7887
and also frames the serial data transfer. When the AD7887 operates in its default mode, the
CS
pin also acts as
the shutdown pin such that with the
CS
pin high, the AD7887 is in its power-down mode.
2 V
DD
Power Supply Input. The V
DD
range for the AD7887 is from 2.7 V to 5.25 V. When the AD7887 is configured for
two-channel operation, this pin also provides the reference source for the part.
3 GND Ground Pin. This pin is the ground reference point for all circuitry on the AD7887. In systems with separate AGND
and DGND planes, these planes should be tied together as close as possible to this GND pin. Where this is not
possible, this GND pin should connect to the AGND plane.
REF
Analog Input 1/Voltage Reference Input. In single-channel mode, this pin becomes the reference input/output.
In this case, the user can either access the internal 2.5 V reference or overdrive the internal reference with the
voltage applied to this pin. The reference voltage range for an externally applied reference is 1.2 V to V
DD
. In two-
channel mode, this pin provides the second analog input channel, AIN1. The input voltage range on AIN1 is
0 to V
DD
.
5 AIN0 Analog Input 0. In single-channel mode, this is the analog input and the input voltage range is 0 to V
REF
. In dual-
channel mode, it has an analog input range of 0 to V
DD
.
6 DIN Data In. Logic Input. Data to be written to the AD7887
’s control register is provided on this input and clocked into
the register on the rising edge of SCLK (see the Control Register section). The AD7887 can be operated as a
single-channel, read-only ADC by tying the DIN line permanently to GND.
7 DOUT Data Out. Logic output. The conversion result from the AD7887 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 consists of four leading zeros
followed by the 12 bits of conversion data, which is provided MSB first.
8 SCLK Serial Clock. Logic input. SCLK provides the serial clock for accessing data from the part and writing serial data to
the control register. This clock input is also used as the clock source for the AD7887’s conversion process.
Rev. E | Page 7 of 24
