Data Sheet

AD7541A

Rev. C | Page 9 of 13

APPLICATIONS INFORMATION

UNIPOLAR BINARY OPERATION (TWO QUADRANT

MULTIPLICATION)

Figure 7 shows the analog circuit connections required for

unipolar binary (two quadrant multiplication) operation. With

a dc reference voltage or current (positive or negative polarity)

applied at Pin 17, the circuit is a unipolar DAC. With an ac

reference voltage or current, the circuit provides two quadrant

multiplication (digitally controlled attenuation). The input/output

relationship is shown in Table 5.

1

2

17

OUT 1

OUT 2

2

GND

18

16

DIGITAL

GROUND

ANALOG

COMMON

AD7541A

C1

33pF

PIN 4 TO

PIN 15

4

15

BIT 1 TO

BIT 12

Figure 7. Unipolar Binary Operation

R1 provides full-scale trim capability (that is, load the DAC

(4095/4096)). Alternatively, full scale can be adjusted by

omitting R1 and R2 and trimming the reference voltage

magnitude.

C1 phase compensation (10 pF to 25 pF) may be required for

stability when using high speed amplifiers. C1 is used to cancel

the pole formed by the DAC internal feedback resistance and

output capacitance at OUT 1.

exhibit a bias current that is low over the temperature range of

times the DAC feedback resistance, nominally 11 kΩ).

Table 4. Recommended Trim Resistor Values vs. Grades

Trim Resistor

JN

KN

R1

100 Ω

100 Ω

R2

47 Ω

33 Ω

Table 5. Unipolar Binary Code Table for Circuit of Figure 7

Binary Number in DAC

MSB

LSB

1 1 1 1

1 1 1 1

1 0 0 0

0 0 0 0

0 0 0 0

0 0 0 0

0 0 0 0

0 0 0 1

0 0 0 0

0 0 0 0

0 0 0 0

0 V