MAX531BESD データシートの表示（PDF） - Maxim Integrated

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MAX531BESD

+5V, Low-Power, Voltage-Output, Serial 12-Bit DACs

Maxim Integrated 

+5V, Low-Power, Voltage-Output,

Serial 12-Bit DACs

DIN DOUT SCLK CS CLR

REFIN

REFOUT

INVERTED

R-2R DAC

2.048V

MAX531

AGND DGND

33µF

VDD VSS

0.1µF

0.1µF

VOUT

2R

RFB

2R

BIPOFF CONNECT BIPOFF

TO VOUT FOR G = 1,

TO AGND FOR G = 2,

+5V

OR TO REFIN FOR

BIPOLAR GAIN

0V TO -5V

Figure 3a. MAX531 Typical Operating Circuit

REFIN

DIN SCLK CS DOUT

INVERTED

R-2R DAC

2R

VOUT

MAX538

MAX539

AGND

0.1µF

2R

VDD

MAX539

ONLY

+5V

Figure 3b. MAX538/MAX539 Typical Operating Circuit

Daisy-Chaining Devices

The serial output, DOUT, allows cascading of two or

more DACs. The data at DIN appears at DOUT,

delayed by 16 clock cycles plus one clock width. For

low power, DOUT is a CMOS output that does not

require an external pull-up resistor. DOUT does not go

into a high-impedance state when CS is high. DOUT

changes on SCLK’s falling edge when CS is low. When

CS is high, DOUT remains in the state of the last data

bit.

Any number of MAX531/MAX538/MAX539 DACs can

be daisy-chained by connecting the DOUT of one

device to the DIN of the next device in the chain. For

proper timing, ensure that tCL (CS low to SCLK high) is

greater than tDO + tDS.

Unipolar Configuration

The MAX531 is configured for a gain of +1 (0V to VREFIN

unipolar output) by connecting BIPOFF and RFB to

VOUT (Figure 6). The converter operates from either sin-

gle or dual supplies in this configuration. See Table 1 for

the DAC-latch contents (input) vs. the analog VOUT

(output). In this range, 1LSB = VREFIN (2-12). The

MAX538 is internally configured for unipolar gain = +1

operation.

A gain of +2 (0V to 2VREFIN unipolar output) is set up

by connecting BIPOFF to AGND and RFB to VOUT

(Figure 7). Table 2 shows the DAC-latch contents vs.

VOUT. The MAX531 operates from either single or dual

supplies in this mode. In this range, 1LSB = (2)(VREFIN)

(2-12) = (VREFIN)(2-11). The MAX539 is internally config-

ured for unipolar gain = +2 operation.

Bipolar Configuration

A bipolar range is set up by connecting BIPOFF to

REFIN and RFB to VOUT, and operating from dual

(±5V) supplies (Figure 8). Table 3 shows the DAC-latch

contents (input) vs. VOUT (output). In this range,

1LSB = VREFIN (2-11).

Four-Quadrant Multiplication

The MAX531 can be used as a four-quadrant multiplier

by connecting BIPOFF to REFIN and RFB to VOUT,

using (1) an offset binary digital code, (2) bipolar power

supplies, using dual power supplies, and (3) a bipolar

analog input at REFIN within the range VSS + 2V to VDD

- 2V, as shown in Figure 9.

In general, a 12-bit DAC’s output is (D) (VREFIN) (G),

where “G” is the gain (+1 or +2) and “D” is the binary

representation of the digital input divided by 212 or

4096. This formula is precise for unipolar operation.

However, for bipolar, offset binary operation, the MSB is

really a polarity bit. No resolution is lost, as there are

the same number of steps. The output voltage, howev-

er, has been shifted from a range of, for example, 0V to

4.096V (G = +2) to a range of -2.048V to +2.048V.

Keep in mind that when using the DAC as a four-quad-

rant multiplier, the scale is skewed. Negative full scale

is -VREFIN, while positive full scale is +VREFIN - 1LSB.

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