AD7846

REV. E

–9–

BIPOLAR OPERATION

Figure 19 shows the AD7846 set up for

±10 V bipolar opera-

tion. The AD588 provides precision

±5 V tracking outputs

The code table for Figure 19 is shown in Table IV.

DGND

+15V

+5V

R2

10k

C1

1 F

SIGNAL

GROUND

–15V

*ADDITIONAL PINS

OMITTED FOR CLARITY

AD7846*

AD588

(–10V TO +10V)

+15V

–15V

R3

100k

R1

39k

+15V

4

Figure 19. Bipolar

±10 V Operation

Table IV. Offset Binary Code Table for Figure 19

Binary Number

Analog Output

in DAC Latch

MSB

LSB

1111 1111 1111 1111

+10 (32767/32768) V

1000 0000 0000 0001

+10 (1/32768) V

1000 0000 0000 0000

0 V

0111 1111 1111 1111

–10 (1/32768) V

0000 0000 0000 0000

–10 (32768/32768) V

NOTE

1 LSB = 10 V/2

µV.

Full scale and bipolar zero adjustment are provided by varying

the gain and balance on the AD588. R2 varies the gain on the

AD588 while R3 adjusts the +5 V and –5 V outputs together

with respect to ground.

For bipolar zero adjustment on the AD7846, load the DAC with

justed by loading the DAC with all 1s and adjusting R2 until

When bipolar zero and full scale adjustment are not needed, R2

and R3 can be omitted, Pin 12 on the AD588 should be con-

nected to Pin 11 and Pin 5 should be left floating. If a user

wants a +5 V output range, there are two choices. By tying Pin

reduced to unity and the output range is

±5 V. If only a positive

+5 V reference is available, bipolar

±5 V operation is still pos-

give a

±5 V output range. However, the linearity, gain, and

offset error specifications will be the same as the unipolar 0 V to

+5 V range.

Other Output Voltage Ranges

In some cases, users may require output voltage ranges other

than those already mentioned. One example is systems which

need the output voltage to be a whole number of millivolts (i.e.,

1 mV, 2 mV, etc.). If the AD689 (8.192 V reference) is used

with the AD7846 as in Figure 20, then the LSB size is 125

µV.

This makes it possible to program whole millivolt values at the

Output. Table V shows the code table for Figure 20.

DGND

+15V

+5V

SIGNAL GROUND

–15V

*ADDITIONAL PINS

OMITTED FOR CLARITY

AD7846*

AD689

(0V TO 8.192V)

Figure 20. Unipolar Output with AD689

Table V. Code Table for Figure 20

Binary Number

Analog Output

in DAC Latch

MSB

LSB

1111 1111 1111 1111

8.192 V (65535/65536) = 8.1919 V

1000 0000 0000 0000

8.192 V (32768/65536) = 4.096 V

0000 0000 0000 1000

8.192 V (8/65536) = 0.001 V

0000 0000 0000 0100

8.192 V (4/65536) = 0.0005 V

0000 0000 0000 0010

8.192 V (2/65536) = 0.00025 V

0000 0000 0000 0001

8.192 V (1/65536) = 0.000125 V

NOTE

1 LSB = 8.192 V/2

µV.

Multiplying Operation

The AD7846 is a full multiplying DAC. To get four-quadrant

Response when the DAC is used in this fashion.