DAC7614EB datasheet(9/17 Pages) TI1

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DAC7614

THEORY OF OPERATION

The DAC7614 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

(“full-scale”) are set by external voltage references (VREFL

and VREFH, respectively). The digital input is a 16-bit serial

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

internal registers to either zero-scale (code 000H) or mid-scale

(code 800H). The reset code is selected by the state of the

RESETSEL pin (LOW = 000H, HIGH = 800H). See Figures

1 and 2 for the basic operation of the DAC7614.

ANALOG OUTPUTS

When VSS = –5V (dual supply operation), the output

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

over the –40

°C to +85°C temperature range. With V

SS = 0V

(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

taken when measuring the zero-scale error when VSS = 0V.

If the output amplifier has a negative offset, the output

voltage may not change for the first few digital input codes

(000H, 001H, 002H, etc.) since the output voltage cannot

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 DAC7614.

FIGURE 2. Basic Dual-Supply Operation of the DAC7614.

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

to code 000

H (0V). If RESETSEL is HIGH, RESET LOW sets all internal registers to code 800H (1.25V).

OUTD

OUTC

REFL

REFH

OUTB

OUTA

RESETSEL

RESET

LOADDACS

NIC

CLK

SDI

GND

Reset DACs(2)

Update Selected Register

Chip Select

Clock

Serial Data In

DAC7614(1)

0.1

µF

0.1

µF

0V to +2.5V

µF to 10µF

+5V

0V to +2.5V

+2.500V

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

to code 800

H (0V). If RESETSEL is LOW, RESET LOW sets all internal registers to code 000H (–2.5V).

OUTD

OUTC

REFL

REFH

OUTB

OUTA

RESETSEL

RESET

LOADDACS

NIC

CLK

SDI

GND

Reset DACs(2)

Update Selected Register

Chip Select

Clock

Serial Data In

DAC7614(1)

0.1

µF

0.1

µF

–2.5V to +2.5V

µF to 10µF

+5V

–5V

0.1

µF

µF to 10µF

–2.5V to +2.5V

–2.500V

0.1

µF

+2.500V

–2.5V to +2.5V

+5V

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