9

®

DAC7615

THEORY OF OPERATION

The DAC7615 is a quad, serial input, 12-bit, voltage output

DAC. The architecture is a classic R-2R ladder configuration

followed by an operational amplifier that serves as a buffer.

Each DAC has its own R-2R ladder network and output op

amp, but all share the reference voltage inputs. The minimum

voltage output (“zero-scale”) and maximum voltage output

word that contains the 12-bit DAC code and a 2-bit address

code that selects one of the four DACs (the two remaining

bits are unused). The converter can be powered from a single

+5V supply or a dual

±5V supply. Each device offers a reset

function which immediately sets all DAC output voltages and

1 and 2 for the basic operation of the DAC7615.

ANALOG OUTPUTS

amplifier can swing to within 2.25V of the supply rails,

over the –40

°C to +85°C temperature range. With V

(single-supply operation), the output can swing to ground.

Note that the settling time of the output op amp will be

longer with voltages very near ground. Also, care must be

If the output amplifier has a negative offset, the output

voltage may not change for the first few digital input codes

swing below ground.

The behavior of the output amplifier can be critical in some

applications. Under short-circuit conditions (DAC output

shorted to ground), the output amplifier can sink a great deal

more current than it can source. See the Specifications table

for more details concerning short circuit current.

FIGURE 1. Basic Single-Supply Operation of the DAC7615.

FIGURE 2. Basic Dual-Supply Operation of the DAC7615.

NOTE: (1) P and U package pin configurations shown. (2) As configured, RESET LOW sets all internal registers

to code 000

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

V

DD

V

OUTD

V

OUTC

V

REFL

V

REFH

V

OUTB

V

OUTA

V

SS

RESETSEL

RESET

LOADREG

LOADDACS

CS

CLK

SDI

GND

Update Selected Register

Update All DAC Registers

Chip Select

Clock

Serial Data In

0.1

µF

0.1

µF

0V to +2.5V

1

µF to 10µF

+5V

+

0V to +2.5V

0V to +2.5V

0V to +2.5V

+2.500V

NOTE: (1) P and U package pin configurations shown. (2) As configured, RESET LOW sets all internal registers

to code 800

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

V

DD

V

OUTD

V

OUTC

V

REFL

V

REFH

V

OUTB

V

OUTA

V

SS

RESETSEL

RESET

LOADREG

LOADDACS

CS

CLK

SDI

GND

Update Selected Register

Update All DAC Registers

Chip Select

Clock

Serial Data In

0.1

µF

0.1

µF

–2.5V to +2.5V

1

µF to 10µF

+5V

–5V

+

0.1

µF

1

µF to 10µF

+

–2.5V to +2.5V

–2.500V

0.1

µF

+2.500V

–2.5V to +2.5V

–2.5V to +2.5V

+5V