DAC16–Typical Performance Characteristics

REV. B

–6–

APPLICATIONS

Power Supplies, Bypassing, and Grounding

All precision converter products require careful application of

good grounding practices to maintain full-rated performance. As

is always the case with analog circuits operating in digital envi-

ronments, digital noise is prevalent; therefore, special care must

be taken to ensure that the DAC16’s inherent precision is main-

tained. This means that particularly good engineering judgment

should be exercised when addressing the power supply, ground-

ing, and bypassing issues using the DAC16.

The DAC16 was designed to operate from +5 V and –15 V

supplies. The +5 V supply primarily powers the digital portion

of the DAC16 and can consume 20 mA, maximum. Although

very little +5 V supply current is used by the reference amplifier,

large amounts of digital noise present on the +5 V supply can

introduce analog errors. It is, therefore, very important that the

+5 V supply be well filtered and regulated. The –15 V supply

provides most of the current for the reference amplifier and all

of the current for the internal DAC. Although the maximum

current in this supply is 10 mA, it must provide a low imped-

ance path for the DAC switch currents. Therefore, it too must

be well filtered and regulated.

The DAC16 includes two ground connections in order to mini-

mize system accuracy degradation arising from grounding er-

rors. The two ground pins are designated DGND (Pin 2) and

AGND (Pin 22). The DGND pin is the return for the digital

circuit sections of the DAC and serves as their input threshold

reference point. Thus, DGND should be connected to the same

ground as the circuitry that drives the digital inputs.

Pin 22, AGND, serves as the reference point for the 9-bit

lower-order DAC as well as the common for the reference am-

plifier, REFGND (Pin 21). This pin should also serve as the

reference point for all analog circuitry associated with the

DAC16. Therefore, to minimize any errors, it is recommended

that AGND connection on the DAC16 be connected to a high

quality analog ground. If the system contains any analog signal

path carrying a significant amount of current, then that path

should have its own return connection to Pin 22.

It is often advisable to maintain separate analog and digital

grounds throughout a complete system, tying them common to

one place only. If the common tie point is remote and an acci-

dental disconnection of that one common tie point were to oc-

cur due to card removal with power on, a large differential

voltage between the two commons could develop. To protect

devices that interface to both digital and analog parts of the

TEMPERATURE – C

–40

0

–20

0

20406080

5

10

15

20

Figure 13. Supply Current vs.

Temperature

BURN-IN TIME – Hours

–1.5

0

–1.0

–0.5

0

0.5

1.0

1.5

200

400

600

800

1000

1200

WORST CASE + DNL

TYPICAL + DNL

TYPICAL – DNL

WORST CASE – DNL

Figure 16. Differential Nonlinearity

vs. Time Accelerated by Burn-In

LOGIC INPUT VOLTAGE – V

ALL DATA BITS

20

0

01

5

234

15

10

5

Logic Input Voltage, All Data Bits

BURN-IN TIME – Hours

–4

0

–3

–2

0

5

4

6

200

400

600

800

1000

1200

WORST CASE + INL

TYPICAL + INL

TYPICAL – INL

WORST CASE – INL

–1

3

2

1

Figure 17. Integral Nonlinearity vs

Time Accelerated by Burn-In

TEMPERATURE – C

50

–40

40

30

20

10

0

–20

0

20406080

DB0 – DB4

DB5 – DB15

Figure 15. Digital Input Current vs.

Temperature

BURN-IN TIME – Hours

–30

0

–20

–10

0

110

120

130

200

400

600

800

1000

1200

WORST CASE

+ GAIN ERROR

TYPICAL

GAIN ERROR

WORST CASE

– GAIN ERROR

Figure 18. Gain Error vs. Time

Accelerated by Burn-In