AD7243 查看數據表（PDF） - Analog Devices

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AD7243

LC2MOS 12-Bit Serial DACPORT

Analog Devices 

AD7243

APPLYING THE AD7243

Power Supply Decoupling

To achieve optimum performance when using the AD7243, the

VDD and VSS lines should each be decoupled to DGND using

0.1 µF capacitors. In noisy environments it is recommended

that 10 µF capacitors be connected in parallel with the 0.1 µF

capacitors.

The internal scaling resistors provided on the AD7243 allow

several output voltage ranges. The part can produce unipolar

output ranges of 0 V to +5 V or 0 V to +10 V and a bipolar out-

put range of ± 5 V. Connections for the various ranges are out-

lined below.

Unipolar (0 V to +10 V) Configuration

The first of the configurations provides an output voltage range

of 0 V to +10 V. This is achieved by connecting the output off-

set resistor ROFS (Pin 13) to AGND. Natural Binary data format

is selected by connecting BIN/COMP (Pin 4) to DGND. In this

configuration, the AD7243 can be operated using either single

or dual supplies. Note that the VDD supply must be ≥+14.25 V

for this range in order to maintain sufficient amplifier head-

room. Dual supplies may be used to improve settling time and

give increased current sink capability for the amplifier. Figure 9

shows the connection diagram for unipolar operation of the

AD7243. Table I shows the digital code vs. analog output for

this configuration.

VDD

VDD

REFOUT

AD7243*

2R

ROFS

REFIN

DAC

2R

VOUT

0V TO + 10V

BIN/

COMP

DGND

AGND VSS

0V OR VSS

*ADDITIONAL PINS OMITTED FOR CLARITY

Figure 9. Unipolar (0 V to +10 V) Configuration

Table I. Unipolar Code Table (0 V to +10 V Range)

Input Data Word

MSB

LSB Analog Output, VOUT

XXXX 1111 1111 1111

XXXX 1000 0000 0001

XXXX 1000 0000 0000

XXXX 0111 1111 1111

XXXX 0000 0000 0001

XXXX 0000 0000 0000

+2 REFIN × (4095/4096)

+2 REFIN × (2049/4096)

+2 REFIN × (2048/4096) = +REFIN

+2 REFIN × (2047/4096)

+2 REFIN × (1/4096)

0V

X = Don’t Care.

Note: 1 LSB = 2 REFIN/4096.

Unipolar (0 V to +5 V) Configuration

The 0 V to +5 V output voltage range is achieved by connecting

ROFS to VOUT. Once again, the AD7243 can be operated using

either single or dual supplies. The table for output voltage vs.

digital code is as in Table I, with 2REFIN replaced by REFIN.

Note, for this range, 1 LSB = REFIN • (2–12 ) = (REFIN/4096).

Bipolar (؎5 V) Configuration

The bipolar configuration for the AD7243, which gives an out-

put range of –5 V to +5 V, is achieved by connecting ROFS to

REFIN. The AD7243 must be operated from dual supplies to

achieve this output voltage range. Either offset binary or two’s

complement data format may be selected. Figure 10 shows the

connection diagram for bipolar operation. An AD586 provides

the reference voltage for the DAC but this could be provided by

the on-chip reference by connecting REFOUT to REFIN.

VDD

VDD

+VIN

ROFS

2R

2R

AD586 VOUT

GND

REFIN

BIN/ COMP

DAC

AD7243*

VOUT

–5V TO + 5V

VDD

DGND

AGND VSS

VSS

*ADDITIONAL PINS OMITTED FOR CLARITY

Figure 10. Bipolar Configuration with External Reference

Bipolar Operation (Two’s Complement Data Format)

The AD7243 is configured for two’s complement data format

by connecting BIN/COMP (Pin 4) high. The analog output vs.

digital code is shown in Table II.

Table II. Two’s Complement Bipolar Code Table

Input Data Word

MSB

LSB

XXXX 0111 1111 1111

XXXX 0000 0000 0001

XXXX 0000 0000 0000

XXXX 1111 1111 1111

XXXX 1000 0000 0001

XXXX 1000 0000 0000

Analog Output, VOUT

+REFIN × (2047/2048)

+REFIN × (1/2048)

0V

–REFIN × (1/2048)

–REFIN × (2047/2048)

–REFIN × (2048/2048) = –REFIN

X = Don’t Care.

Note: 1 LSB = REFIN/2048.

Bipolar Operation (Offset Binary Data Format)

The AD7243 is configured for Offset Binary data format by

connecting BIN/COMP (Pin 4) low. The analog output vs. digi-

tal code may be obtained by inverting the MSB in Table II.

–8–

REV. A

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