DAC8562

REV. A

–10–

15

16

DGND

AGND

DATA

DAC-8562

13

+12V OR +15V

10

CE

CLR

1

12

0.1µF

4

REF-02

6

2

0.1µF

Figure 31. Operating the DAC8562 on +12 V or +15 V

Supplies Using a REF02 Voltage Reference

Measuring Offset Error

One of the most commonly specified endpoint errors associated

with real-world nonideal DACs is offset error.

In most DAC testing, the offset error is measured by applying

the zero-scale code and measuring the output deviation from

0 volt. There are some DACs where offset errors may be present

but not observable at the zero scale because of other circuit limi-

tations (for example, zero coinciding with single supply ground).

In these DACs, nonzero output at zero code cannot be read as

the offset error. In the DAC8562, for example, the zero-scale er-

ror is specified to be +3 LSBs. Since zero scale coincides with

zero volt, it is not possible to measure negative offset error.

By adding a pull-down resistor from the output of the

DAC8562 to a negative supply as shown in Figure 32, offset er-

rors can now be read at zero code. This configuration forces the

output P-channel MOSFET to source current to the negative

supply thereby allowing the designer to determine in which di-

rection the offset error appears. The value of the resistor should

be such that, at zero code, current through the resistor is 200

µA

maximum.

15

16

DGND

AGND

DATA

DAC-8562

13

0.1µF

+5V

10

CE

CLR

20

12

200µA MAX

V–

Figure 32. Measuring Zero-Scale or Offset Error

Unipolar Output Operation

This is the basic mode of operation for the DAC8562. As shown

in Figure 30, the DAC8562 has been designed to drive loads as

low as 820

Ω in parallel with 500 pF. The code table for this op-

eration is shown in Table III.

15

16

DGND

AGND

DATA

DAC-8562

13

10µF

0.1µF

0V

+5V

10

CE

CLR

20

12

820

500pF

Ω

Figure 30. Unipolar Output Operation

Table III. Unipolar Code Table

Hexadecimal Number

Decimal Number

Analog Output

in DAC Register

in DAC Register

Voltage (V)

FFF

4095

+4.095

801

2049

+2.049

800

2048

+2.048

7FF

2047

+2.047

000

0

0

Operating the DAC8562 on +12 V or +15 V Supplies Only

Although the DAC8562 has been specified to operate on a

single, +5 V supply, a single +5 V supply may not be available in

many applications. Since the DAC8562 consumes no more than

6 mA, maximum, then an integrated voltage reference, such as

the REF02, can be used as the DAC8562 +5 V supply. The

configuration of the circuit is shown in Figure 31. Notice that

the reference’s output voltage requires no trimming because of

the REF02’s excellent load regulation and tight initial output

voltage tolerance. Although the maximum supply current of the

DAC8562 is 6 mA, local bypassing of the REF02’s output with

at least 0. 1

µF at the DAC’s voltage supply pin is recommended

to prevent the DAC’s internal digital circuits from affecting the

DAC’s internal voltage reference.