10

LTC1595/LTC1596/LTC1596-1

Bipolar (4-Quadrant Multiplying) Mode

The LTC1595/LTC1596 can be used with a dual op amp

and three external resistors to provide 4-quadrant multi-

plying operation as shown in Figure 2 (last page). With a

fixed 10V reference, the circuits shown give a precision

bipolar –10V to 10V output swing. Using the LTC1596-1

will cause the power-on reset and clear pin to reset the DAC

to midscale (bipolar zero).

Op Amp Selection

Because of the extremely high accuracy of the 16-bit

LTC1595/LTC1596, thought should be given to op amp

selection in order to achieve the exceptional performance

of which the part is capable. Fortunately, the sensitivity of

INL and DNL to op amp offset has been greatly reduced

compared to previous generations of multiplying DACs.

Op amp offset will contribute mostly to output offset and

gain and will have minimal effect on INL and DNL. For

example, a 500

µV op amp offset will cause about 0.55LSB

INL degradation and 0.15LSB DNL degradation with a 10V

full-scale range. The main effects of op amp offset will be

a degradation of zero-scale error equal to the op amp

offset, and a degradation of full-scale error equal to twice

the op amp offset. For example, the same 500

µV op amp

offset will cause a 3.3LSB zero-scale error and a 6.5LSB

full-scale error with a 10V full-scale range.

Table 2 shows a selection of LTC op amps which are

suitable for use with the LTC1595/LTC1596. For a thor-

ough discussion of 16-bit DAC settling time and op amp

selection, refer to Application Note 74, “

Component and

Measurement Advances Ensure 16-Bit DAC Settling Time.”

Grounding

As with any high resolution converter, clean grounding is

important. A low impedance analog ground plane and star

(LTC1595) must be tied to the star ground with as low a

resistance as possible.

Table 2. 16-Bit Settling Time for Various Amplifiers Driven by the LT1595 DAC. LT1468 (Shaded) Offers Fastest Settling Time While

Maintaining Accuracy Over Temperature

CONSERVATIVE SETTLING TIME

AMPLIFIER

AND COMPENSATION VALUE

COMMENTS

LT1001

120

µs

100pF

Good Low Speed Choice

LT1007

19

µs

100pF

LT1013

75

µs

150pF

LT1077

200

µs

100pF

LT1097

120

µs

75pF

Good Low Speed Choice

LT1112

120

µs

100pF

Good Low Speed Choice Dual

LT1178

450

µs

100pF

Low Power Dual

LT1468

2.5

µs

30pF

Fastest Settling with 16-Bit Performance