AD7528

REV. B

–8–

DIGITALLY CONTROLLED DUAL TELEPHONE

ATTENUATOR

In this configuration the AD7528 functions as a 2-channel digi-

tally controlled attenuator. Ideal for stereo audio and telephone

signal level control applications. Table IV gives input codes vs.

attenuation for a 0 dB to 15.5 dB range.

Input Code = 256

10 exp

−









Attenuation dB

,

20

DATA BUS

DAC A/DAC B

CS

WR

AD7528

DB0

DB7

DAC A

DAC B

A1

A2

SUGGESTED

OP AMP: AD644

Figure 15. Digitally Controlled Dual Telephone Attenuator

Table IV. Attenuation vs. DAC A, DAC B Code for the Circuit

of Figure 15

Attn. DAC Input

Code In

Attn. DAC Input

Code In

dB

Code

Decimal

dB

Code

Decimal

0.0

1 1 1 1 1 1 1 1

255

0 1 1 0 0 1 1 0

102

0.5

1 1 1 1 0 0 1 0

242

0 1 1 0 0 0 0 0

96

1.0

1 1 1 0 0 1 0 0

228

0 1 0 1 1 0 1 1

91

1.5

1 1 0 1 0 1 1 1

215

0 1 0 1 0 1 1 0

86

2.0

1 1 0 0 1 0 1 1

203

10.0

0 1 0 1 0 0 0 1

81

2.5

1 1 0 0 0 0 0 0

192

10.5

0 1 0 0 1 1 0 0

76

3.0

1 0 1 1 0 1 0 1

181

11.0

0 1 0 0 1 0 0 0

72

3.5

1 0 1 0 1 0 1 1

171

11.5

0 1 0 0 0 1 0 0

68

4.0

1 0 1 0 0 0 1 0

162

12.0

0 1 0 0 0 0 0 0

64

4.5

1 0 0 1 1 0 0 0

152

12.5

0 0 1 1 1 1 0 1

61

5.0

1 0 0 1 0 0 0 0

144

13.0

0 0 1 1 1 0 0 1

57

5.5

1 0 0 0 1 0 0 0

136

13.5

0 0 1 1 0 1 1 0

54

6.0

1 0 0 0 0 0 0 0

128

14.0

0 0 1 1 0 0 1 1

51

6.5

0 1 1 1 1 0 0 1

121

14.5

0 0 1 1 0 0 0 0

48

7.0

0 1 1 1 0 0 1 0

114

15.0

0 0 1 0 1 1 1 0

46

7.5

0 1 1 0 1 1 0 0

108

15.5

0 0 1 0 1 0 1 1

43

For further applications information the reader is referred to

Analog Devices Application Note on the AD7528.

20-Lead Cerdip (Q-20)

0.97 (24.64)

0.935 (23.75)

SEATING

PLANE

0.02 (0.5)

0.016 (0.41)

0.07 (1.78)

0.05 (1.27)

0.15 (3.8)

0.125 (3.18)

0.20 (5.0)

0.14 (3.56)

0.11 (2.79)

0.09 (2.28)

20

110

11

0.28 (7.11)

0.24 (6.1)

PIN 1

0.14 (3.56)

0.125 (3.17)

15

0

0.32 (8.128)

0.29 (7.366)

0.011 (0.28)

0.009 (0.23)

LEAD NO. 1 IDENTIFIED BY DOT OR NOTCH

LEADS ARE SOLDER OR TIN-PLATED KOVAR OR ALLOY 42

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).

20-Lead Plastic DIP (N-20)

SEATING

PLANE

0.021 (0.533)

0.015 (0.381)

0.065 (1.66)

0.045 (1.15)

0.11 (2.79)

0.09 (2.28)

0.145 (3.683)

MIN

0.125 (3.175)

MIN

20

110

11

PIN 1

1.07 (27.18) MAX

0.255 (6.477)

0.245 (6.223)

0.32 (8.128)

0.30 (7.62)

0.011 (0.28)

0.009 (0.23)

0.135 (3.429)

0.125 (3.17)

15

0

LEAD NO. 1 IDENTIFIED BY DOT OR NOTCH

LEADS ARE SOLDER OR TIN-PLATED KOVAR OR ALLOY 42

20-Lead SOIC (R-20)

SEATING

PLANE

0.0118 (0.30)

0.0040 (0.10)

0.0192 (0.49)

0.0138 (0.35)

0.1043 (2.65)

0.0926 (2.35)

0.0500

(1.27)

BSC

0.0125 (0.32)

0.0091 (0.23)

0.0500 (1.27)

0.0157 (0.40)

8

0

0.0291 (0.74)

0.0098 (0.25)

45

11

20

10

1

0.5118 (13.00)

0.4961 (12.60)

0.4193 (10.65)

0.3937 (10.00)

0.2992 (7.60)

0.2914 (7.40)

PIN 1

20-Lead Plastic Leaded Chip Carrier (P-20A)

0.021 (0.53)

0.013 (0.33)

0.032 (0.81)

0.026 (0.66)

0.180 (4.47)

0.165 (4.19)

0.12 (3.05)

0.09 (2.29)

0.020 (0.51) MIN

0.025 (0.64)

MIN

0.060 (1.53)

MIN

3

PIN 1

IDENTIFIER

4

19

18

8

9

14

13

TOP VIEW

(PINS DOWN)

0.356 (9.04)

0.350 (8.89)

SQ

0.048 (1.21)

0.042 (1.07)

0.02

(0.51)

MAX

0.050

(1.27)

BSC

0.02 (0.51)

MAX

0.395 (10.02)

0.385 (9.78)

SQ