TLC7226C, TLC7226I, TLC7226M

QUADRUPLE 8BIT DIGITALTOANALOG CONVERTERS

SLAS060E − JANUARY 1995 − REVISED JANUARY 2003

7

POST OFFICE BOX 655303

PRINCIPLES OF OPERATION

AGND bias for direct bipolar output operation

The TLC7226 can be used in bipolar operation without adding more external operational amplifiers as shown

bipolar output with no additional components. The transfer values are shown in Table 1.

_

+

DAC A

AGND

DGND

TLC7226‡

REF (Vref = 5 V)

OUT

4

18

2

6

3

VDD

5

VSS

−5 V

Output range

(5 V to − 5 V)

‡ Digital inputs omitted for clarity.

Figure 4. AGND Bias for Direct Bipolar Operation

LSB

MSB

DAC LATCH CONTENTS

ANALOG OUTPUT

) V

ref

127

128

1111

1111

) V

ref

1

128

1000

0001

1000

0000

–V

ref

128

128

+* V

ref

0111

1111

0000

0001

* V

ref

127

128

0000

0000

0 V

Table 1. Bipolar (Offset Binary) Code

* V

ref

1

128

AGND bias for positive output offset

The TLC7226 AGND terminal can be biased above or below the system ground terminal, DGND, to provide an

offset analog output voltage level. Figure 5 shows a circuit configuration to achieve this for channel A of the

V

O +

V

BIAS )

D

A

V

I

(1)

specified operation. Since the AGND terminal is common to all four DACs, this method biases up the output

to DGND.