ANALOG DEVICES AD7118 Service Manual

LOGDAC

a

FEATURES
Dynamic Range 85.5 dB
Resolution 1.5 dB
Full 625 V Input Range Multiplying DAC
Full Military Temperature Range –558C to +1258C
Low Distortion
Low Power Consumption
Latch Proof Operation (Schottky Diodes Not Required)
Single 5 V to 15 V Supply

APPLICATIONS
Digitally Controlled AGC Systems
Audio Attenuators
Wide Dynamic Range A/D Converters
Sonar Systems
Function Generators

GENERAL DESCRIPTION

The LOGDAC® AD7118 is a CMOS multiplying D/A con­verter which attenuates an analog input signal over the range
0 to –85.5 dB in 1.5 dB steps. The analog output is determined
by a six-bit attenuation code applied to the digital inputs.
Operating frequency range of the device is from dc to several
hundred kHz.

The device is manufactured using an advanced monolithic
silicon gate thin-film on CMOS process and is packaged in a
14-pin dual-in-line package.

CMOS Logarithmic D/A Converter

AD7118*

FUNCTIONAL DIAGRAM

PIN CONFIGURATION

ORDERING INFORMATION

Specified

Temperature Accuracy Package

Model Range Range Option

AD7118KN 0°C to +70°C 0 to 42 dB N-16
AD7118LN 0°C to +70°C 0 to 48 dB N-16
AD7118BQ –25°C to +85°C 0 to 42 dB Q-16
AD7118CQ –25°C to +85°C 0 to 48 dB Q-16
AD7118TQ
AD7118UQ2–55°C to +125°C 0 to 48 dB Q-16

NOTES

1

N = Plastic DIP; Q = Cerdip.

2

To order MIL-STD-883, Class B processed parts, add /883B to part number.

*Protected by U.S. Patent No. 4521,764.

LOGDAC is a registered trademark of Analog Devices, Inc.

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Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.

2

–55°C to +125°C 0 to 42 dB Q-16

1

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] Fax: [phone]

(VDD = +5 V or +15 V, VIN = –10 V dc, I

AD7118–SPECIFICA TIONS

Parameter VDD = +5 V VDD = +15 V VDD = +5 V VDD = +15 V Units Test Conditions/Comments

NOMINAL RESOLUTION 1.5 1.5 1.5 1.5 dB
ACCURACY RELATIVE TO V

AD7118L/C/U

0 dB to –30 dB ±0.35 ±0.35 ±0.4 ±0.4 dB max Accuracy is measured using
–31.5 dB to –42 dB ±0.7 ±0.5 ±0.8 ±0.7 dB max circuit of Figure 1 and includes
–43.5 dB to –48 dB ±1.0 ±0.7 ±1.3 ±1.0 dB max any effects due to mismatch

AD7118K/B/T between RFB and the R-2R

0 dB to –30 dB ±0.5 ±0.5 ±0.5 ±0.5 dB max ladder circuit.
–31.5 dB to –42 dB ±0.75 ±0.75 ±1.0 ±0.8 dB max

MONOTONIC RANGE

Nominal 1.5 dB Steps L/C/U Grade Monotonic Over Full 0 to –72 0 to –72 dB Digital Inputs 000000 to 110000
Nominal 3 dB Steps All Grades Monotonic Over Full Code Range

VIN INPUT RESISTANCE All Grades 9 9 9 9 kΩ min

(PIN 12) L/C/U Grade 17 17 17 17 kΩ max

RFB INPUT RESISTANCE All Grades 9.45 9.45 9.45 9.45 kΩ min

(PIN 13) L/C/U Grade 18 18 18 18 kΩ max

DIGITAL INPUTS

Input High Voltage Requirements V
Input Low Voltage Requirements V
Input Leakage Current ±1 ±1 ±10 ±10 µA max Digital Inputs = V

POWER SUPPLY

V

for Specified Accuracy 5 – 5 – V min

DD

I

DD

Specifications subject to change without notice.

IN

K/B/T Grade Code Range 0 to –66 0 to –66 dB Digital Inputs 000000 to 101100

K/B/T Grade 21 21 21 21 kΩ max

K/B/T Grade 22 22 22 22 kΩ max

IH

IL

3.0 13.5 3.0 13.5 V min

0.8 1.5 0.8 1.5 V max

– 15 – 15 V max

0.5 1 1 2 mA max Digital Inputs = 0 V or V

AD544 except where noted)

TA = +258CT

= T

, T

A

MIN

MAX

(VDD = +5 V or +15 V, VIN = –10 V except where stated, I

AC PERFORMANCE CHARACTERISTICS

0 V, output amplifier AD544 except where noted)

= AGND = DGND = 0 V, output amplifier

OUT

DD

(See Figure 7)

= AGND = DGND =

OUT

DD

These characteristics are included for design guidance only and are not subject to test.

TA = +258CT

Parameter VDD = +5 V VDD = +15 V VDD = +5 V VDD = +15 V Units

DC Supply Rejection, ∆Gain/∆V
Propagation Delay 1.8 0.4 2.2 0.5 µs max Full-Scale Change

Digital-to-Analog Glitch Impulse 225 1200 – – nV secs typ Measured with ADLH0032CG

Output Capacitance (Pin 14) 100 100 100 100 pF max
Input Capacitance Pin 12 and Pin 13 7 7 7 7 pF max
Feedthrough at 1 kHz L/C/U Grade –86 –86 –68 –68 dB max Feedthrough is also deter-

Total Harmonic Distortion –85 –85 –85 –85 dB typ VIN = 6 V rms
Intermodulation Distortion –79 –79 –79 –79 dB typ per DIN 45403 Blatt 4
Output Noise Voltage Density 70 70 70 70 nV/√Hz max Includes AD544 amplifier noise
Digital Input Capacitance 7 7 7 7 pF max

Specifications subject to change without notice.

DD

K/B/T Grade –80 –80 –63 –63 dB max mined by circuit layout

0.01 0.005 0.01 0.005 dB per % max ∆VDD = ±10%,

= T

, T

A

MIN

MAX

Input code = 100000

as output amplifier for input
code transition 100000 to 000000.
C1 of Figure 1 is 0 pF.

Accuracy Specification for K/B/T Grade Devices at TA = +25°C

Accuracy Specification for L/C/U Grade Devices at TA = +25°C

–2–

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