Data Sheet

AD7607

Rev. C | Page 23 of 32

CONVERSION CONTROL

Simultaneous Sampling on All Analog Input Channels

The AD7607 allows simultaneous sampling of all analog input

channels. All channels are sampled simultaneously when both

CONVST pins (CONVST A, CONVST B) are tied together. A

single CONVST signal is used to control both CONVST x inputs.

The rising edge of this common CONVST signal initiates

simultaneous sampling on all analog input channels.

The AD7607 contains an on-chip oscillator that is used to

perform the conversions. The conversion time for all ADC

conversions are in progress, so when the rising edge of CONVST

is applied, BUSY goes logic high and transitions low at the end

of the entire conversion process. The falling edge of the BUSY

signal is used to place all eight track-and-hold amplifiers back

into track mode. The falling edge of BUSY also indicates that

the new data can now be read from the parallel bus (DB[15:0]),

(DB[7:0]).

Simultaneously Sampling Two Sets of Channels

The AD7607 also allows the analog input channels to be sampled

simultaneously in two sets. This can be used in power-line

protection and measurement systems to compensate for phase

differences between current and voltage sensors. In a 50 Hz

system, this allows for up to 9° of phase compensation; and in a

60 Hz system, it allows for up to 10° of phase compensation.

This is accomplished by pulsing the two CONVST pins

independently and is possible only if oversampling is not in

use. CONVST A is used to initiate simultaneous sampling of

the first set of channels (V1 to V4), and CONVST B is used

to initiate simultaneous sampling on the second set of analog

input channels (V5 to V8), as illustrated in Figure 40.

On the rising edge of CONVST A, the track-and-hold

amplifiers for the first set of channels are placed into hold

mode. On the rising edge of CONVST B, the track-and-hold

amplifiers for the second set of channels are placed into hold

mode. The conversion process begins when both rising edges

of CONVST x have occurred; therefore, BUSY goes high on the

indicates the maximum allowable time between CONVST x

sampling points.

There is no change to the data read process when using two

separate CONVST x signals.

Connect all unused analog input channels to AGND. The results

for any unused channels are still included in the data read because

all channels are always converted.

CONVST A

CONVST B

BUSY

CS/RD

DATA: DB[15:0]

FRSTDATA

V1

V2

V3

V7

V8

V1 TO V4 TRACK-AND-HOLD

ENTER HOLD

V5 TO V8 TRACK-AND-HOLD

ENTER HOLD

AD7607 CONVERTS

ON ALL 8 CHANNELS

Figure 40. Simultaneous Sampling on Channel Sets While Using Independent CONVST A and CONVST B Signals—Parallel Interface Mode