Datasheet

Data Sheet AD7634
Rev. B | Page 11 of 32
Pin No. Mnemonic Type
1
Description
36 BIPOLAR DI
2
Input Range Select. See description for Pin 30.
37 REF AO/I
Reference Input/Output. When PDREF/PDBUF = low, the internal reference and buffer are enabled, produc-
ing 5 V on this pin. When PDREF/PDBUF = high, the internal reference and buffer are disabled, allowing
an externally supplied voltage reference up to AVDD volts. Decoupling with at least a 22 F capacitor is
required with or without the internal reference and buffer. See the Voltage Reference Input/Output
section.
38 REFGND AI Reference Input Analog Ground. Connected to analog ground plane.
39 IN− AI
Analog Input. Referenced to IN+.
In the 0 V to 5 V input range, IN− is between 0 V and V
REF
V centered about V
REF
/2. In the 0 V to 10 V
range, IN− is between 0 V and 2 V
REF
V centered about V
REF
.
In the ±5 V and ±10 V ranges, IN− is true bipolar up to ±2 V
REF
V (±5 V range) or ±4 V
REF
V (±10 V range)
and centered about 0 V.
In all ranges, IN− must be driven 180° out of phase with IN+.
40 VCC P High Voltage Positive Supply. Normally 7 V to 15 V.
41 VEE P High Voltage Negative Supply. Normally 0 V to −15 V (0 V in unipolar ranges).
43 IN+ AI
Analog Input. Referenced to IN−.
In the 0 V to 5 V input range, IN+ is between 0 V and V
REF
V centered about V
REF
/2. In the 0 V to 10 V
range, IN+ is between 0 V and 2 V
REF
V centered about V
REF
.
In the ±5 V and ±10 V ranges, IN+ is true bipolar up to ±2 V
REF
V (±5 V range) or ±4 V
REF
V (±10 V range)
and centered about 0 V.
In all ranges, IN+ must be driven 180° out of phase with IN−
45 TEMP AO
Temperature Sensor Analog Output. When the internal reference is enabled (PDREF = PDBUF = low),
this pin outputs a voltage proportional to the temperature of the AD7634. See the Voltage Reference
Input/Output section.
46 REFBUFIN AI
Reference Buffer Input. When using an external reference with the internal reference buffer (PDBUF = low,
PDREF = high), applying 2.5 V on this pin produces 5 V on the REF pin. See the Voltage Reference
Input/Output section.
47 PDREF DI Internal Reference Power-Down Input.
When low, the internal reference is enabled.
When high, the internal reference is powered down, and an external reference must be used.
48 PDBUF DI Internal Reference Buffer Power-Down Input.
When low, the buffer is enabled (must be low when using internal reference).
When high, the buffer is powered-down.
49 EPAD
3
NC
Exposed Pad. The exposed pad is not connected internally. It is recommended that the pad be
soldered to VEE.
1
AI = analog input; AI/O = bidirectional analog; AO = analog output; DI = digital input; DI/O = bidirectional digital; DO = digital output; P = power, NC = no internal
connection.
2
In serial configuration mode (MODE[1:0] = 3, HW/
SW
= low), this input is programmed with the serial configuration register and this pin is a don’t care. See the
Hardware Configuration section and the Software Configuration section.
3
LFCSP_VQ package only.
Table 7. Data Bus Interface Definition
MODE MODE1 MODE0 D0/OB/
2C
D1/A0 D2/A1 D[3] D[4:9] D[10:11] D[12:15] D[16:17] Description
0 0 0 R[0] R[1] R[2] R[3] R[4:9] R[10:11] R[12:15] R[16:17] 18-bit parallel
1 0 1
OB/2C
A0 = 0 R[2] R[3] R[4:9] R[10:11] R[12:15] R[16:17] 16-bit high word
1 0 1
OB/2C
A0 = 1 R[0] R[1] All zeros 16-bit low word
2 1 0
OB/2C
A0 = 0 A1 = 0 All High-Z R[10:11] R[12:15] R[16:17] 8-bit high byte
2 1 0
OB/2C
A0 = 0 A1 = 1 All High-Z R[2:3] R[4:7] R[8:9] 8-bit midbyte
2 1 0
OB/2C
A0 = 1 A1 = 0 All High-Z R[0:1] All zeros 8-bit low byte
2 1 0
OB/2C
A0 = 1 A1 = 1 All High-Z All zeros R[0:1] 8-bit low byte
3 1 1
OB/2C
All High-Z Serial interface Serial interface