REV. A
AD7677
–7–
PIN FUNCTION DESCRIPTIONS (continued)
Pin
No. Mnemonic Type Description
19 DVDD P Digital Power. Nominally at 5 V.
20 DGND P Digital Power Ground
21 DATA[8] DO When SER/PAR is LOW, this output is used as the Bit 8 of the Parallel Port Data Output Bus.
or SDOUT When SER/PAR is HIGH, this output, part of the serial port, is used as a serial data output
synchronized to SCLK. Conversion results are stored in an on-chip register. The AD7677
provides the conversion result, MSB first, from its internal shift register. The DATA format is
determined by the logic level of OB/2C. In serial mode, when EXT/INT is LOW, SDOUT
is valid on both edges of SCLK. In serial mode, when EXT/INT is HIGH: If INVSCLK is
LOW, SDOUT is updated on SCLK rising edge and valid on the next falling edge. If INVSCLK
is HIGH, SDOUT is updated on SCLK falling edge and valid on the next rising edge.
22 DATA[9] DI/O When SER/PAR is LOW, this output is used as the Bit 9 of the Parallel Port Data Output Bus.
or SCLK When SER/PAR is HIGH, this pin, part of the serial port, is used as a serial data clock input
or output, dependent upon the logic state of the EXT/INT pin. The active edge where the
data SDOUT is updated depends upon the logic state of the INVSCLK pin.
23 DATA[10] DO When SER/PAR is LOW, this output is used as the Bit 10 of the Parallel Port Data Output Bus.
or SYNC When SER/PAR is HIGH, this output, part of the serial port, is used as a digital output frame
synchronization for use with the internal data clock (EXT/INT = Logic LOW). When a read
sequence is initiated and INVSYNC is LOW, SYNC is driven HIGH and remains HIGH
while SDOUT output is valid. When a read sequence is initiated and INVSYNC is HIGH,
SYNC is driven LOW and remains LOW while SDOUT output is valid.
24 DATA[11] DO When SER/PAR is LOW, this output is used as the Bit 11 of the Parallel Port Data Output Bus.
or RDERROR When SER/PAR is HIGH and EXT/INT is HIGH, this output, part of the serial port, is used
as an incomplete read error flag. In slave mode, when a data read is started and not complete
when the following conversion is complete, the current data is lost and RDERROR is pulsed high.
25–28 DATA[12:15] DO Bit 12 to Bit 15 of the Parallel Port Data Output Bus. These pins are always outputs regard-
less of the state of SER/PAR.
29 BUSY DO Busy Output. Transitions HIGH when a conversion is started, and remains HIGH until the
conversion is complete and the data is latched into the on-chip shift register. The falling edge
of BUSY could be used as a data ready clock signal.
30 DGND P Must be tied to digital ground.
31 RD DI Read Data. When CS and RD are both LOW, the interface parallel or serial output bus is enabled.
32 CS DI Chip Select. When CS and RD are both LOW, the interface parallel or serial output bus is
enabled. CS is also used to gate the external serial clock.
33 RESET DI Reset Input. When set to a logic HIGH, reset the AD7677. Current conversion if any is aborted.
34 PD DI Power-Down Input. When set to a logic HIGH, power consumption is reduced and conver-
sions are inhibited after the current one is completed.
35 CNVST DI Start Conversion. A falling edge on CNVST puts the internal sample/hold into the hold state and
initiates a conversion. In impulse mode (IMPULSE HIGH and WARP LOW), if CNVST is
held low when the acquisition phase (t
8
) is complete, the internal sample/hold is put into the
hold state and a conversion is immediately started.
36 AGND P Must be Tied to Analog Ground.
37 REF AI Reference Input Voltage
38 REFGND AI Reference Input Analog Ground
39 IN– AI Differential Negative Analog Input
43 IN+ AI Differential Positive Analog Input
NOTES
AI = Analog Input
DI = Digital Input
DI/O = Bidirectional Digital
DO = Digital Output
P = Power
