Analog Devices AD7111ABR, AD7111ABN, AD7111UQ-883B, AD7111TE-883B, AD7111LN Datasheet

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LC2MOS LOGDAC

17-BIT DAC

17-BIT LATCH

DECODE LOGIC

8-BIT BUFFER

CONTROL LOGIC

AD7111A

OUT

AGND

DGND

D0 – D7

FEATURES Dynamic Range: 88.5 dB Resolution: 0.375 dB On-Chip Data Latches +5 V Operation AD7111A Pin Compatible with AD7524 Low Power

APPLICATIONS Audio Attenuators Sonar Systems Function Generators Digitally Controlled AGC System

GENERAL DESCRIPTION

The LOGDAC AD7111/AD7111A are monolithic multiplying D/A converters featuring wide dynamic range in a small package. Both DACs can attenuate an analog input signal over the range 0 dB to 88.5 dB in 0.375 dB steps. They are available in 16-pin DIPs and SOIC packages. The AD7111 is also available in a 20-terminal LCCC package.

The degree of attenuation across the DAC is determined by an 8-bit word applied to the onboard decode logic. This 8-bit word is decoded into a 17-bit word which is then applied to a 17-bit R-2R ladder. The very fine step resolution, which is available over the entire dynamic range, is due to the use of this 17-bit DAC.

The AD7111/AD7111A are easily interfaced to a standard 8-bit MPU bus via an 8-bit data port and standard microprocessor control lines. The AD7111 quires a rising edge to load new data to the DAC. The AD7111A WR is level triggered to allow transparent operation of the latches, if required. It should also be noted that the AD7111A is exactly pin and function-compatible with the AD7524, an industry standard 8-bit multiplying DAC. This allows an easy upgrading of existing AD7524 designs which would benefit both from the wider dynamic range and the finer step resolution offered by the AD7111A.

The AD7111/AD7111A are fabricated in Linear Compatible CMOS (LC2MOS), an advanced, mixed technology process that combines precision bipolar circuits with low power CMOS logic.

LOGDAC is a registered trademark of Analog Devices, Inc.

WR input is edge triggered and re-

Logarithmic D/A Converter

AD7111/AD7111A

FUNCTIONAL BLOCK DIAGRAMS

AD7111

17-BIT DAC

17-BIT LATCH

DECODE LOGIC

CONTROL LOGIC

8-BIT BUFFER

D0 – D7

DGND

PRODUCT HIGHLIGHTS

1. Wide Dynamic Range: 0 dB to 88.5 dB attenuation range in

0.375 dB steps.

2. Small Package: The AD7111/AD7111A are available in 16-pin DIPs and SOIC packages.

3. Transparent Latch Operation: By tying the puts low, the DAC latches in the AD7111A can be made transparent.

4. Fast Microprocessor Interface: Data setup times of 25 ns and write pulse width of 57 ns make the AD7111A compatible with modern microprocessors.

OUT

AGND

CS and WR in-

REV. 0

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.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 617/329-4700 Fax: 617/326-8703

AD7111/AD7111A–SPECIFICA TIONS

(VDD = +5 V, VIN = –10 V dc, I

AD7111–ELECTRICAL CHARACTERISTICS

AD711 except where noted)

= AGND = DGND = O V output amplifier

OUT

Parameter TA = +258CTA = T

NOMINAL RESOLUTION 0.375 0.375 0.375 0.375 dB ACCURACY RELATIVE TO

0 dB ATTENUATION

0.375 dB Steps: Accuracy ≤ ±0.17 dB 0 to 36 0 to 36 0 to 30 0 to 30 dB min Guaranteed Attenuation Ranges Monotonic 0 to 54 0 to 54 0 to 48 0 to 48 dB min for Specified Step Sizes

0.75 dB Steps: Accuracy ≤ ±0.35 dB 0 to 48 0 to 42 0 to 42 0 to 36 dB min Monotonic 0 to 72 0 to 66 0 to 72 0 to 60 dB min

1.5 dB Steps: Accuracy ≤ ±0.7 dB 0 to 54 0 to 48 0 to 42 0 to 42 dB min Full Range Is from 0 dB Monotonic Full Range 0 to 78 0 to 85.5 0 to 72 dB min to 88.5 dB

3.0 dB Steps: Accuracy ≤ ±1.4 dB 0 to 66 0 to 54 0 to 60 0 to 48 dB min Monotonic Full Range Full Range Full Range Full Range dB min

6.0 dB Steps: Accuracy ≤ ±2.7 dB 0 to 72 0 to 60 0 to 60 0 to 48 dB min Monotonic Full Range Full Range Full Range Full Range dB min

GAIN ERROR ± 0.1 ± 0.15 ± 0.15 ±0.20 dB max VIN INPUT RESISTANCE 9/11/15 9/11/15 7/11/18 7/11/18 kΩ min/typ/max RFB INPUT RESISTANCE 9.3/11.5/15.7 9.3/11.5/15.7 7.3/11.5/18.8 7.3/11.5/18.8 kΩ min/typ/max DIGITAL INPUTS

VIH (Input High Voltage) 2.4 2.4 2.4 2.4 V min VIL (Input Low Voltage) 0.8 0.8 0.8 0.8 V max Input Leakage Current ± 1 ±10 ± 1 ± 10 µA max Digital Inputs = V

SWITCHING CHARACTERISTICS

RFSH

POWER SUPPLY

NOTE

Sample tested at +25°C to ensure compliance.

Specifications subject to change without notice.

AD7111L/C/U Grades AD7111K/B/T Grades

0 0 0 0 ns min 0 0 0 0 ns min Chip Select to Write Hold Time 350 500 350 500 ns min Write Pulse Width 175 250 175 250 ns min Data Valid to Write Setup Time

10 10 10 10 ns min Data Valid to Write Hold Time 3 4.5 3 4.5 µs min Refresh Time

+5 +5 +5 +5 V 1 4 1 4 mA max Digital Inputs = VIL or V 500 1000 500 1000 µA max Digital Inputs = 0 V or VDD;

MIN

, T

MAXTA

= +258CTA = T

MIN

, T

Units Conditions/Comments

MAX

Chip Select to Write Setup Time

See Figure 6

AC PERFORMANCE CHARACTERISTICS

to test. VDD = +5 V, VIN = –10 V dc except where noted, I

Parameter TA = +258CTA = T

DC Supply Rejection, ∆Gain/∆V Propagation Delay 3.0 4.5 3.0 4.5 µs max Full-Scale Change Measured from

Digital-to-Analog Glitch Impulse 100 100 nV secs typ Measured with AD843 as Output

Output Capacitance, Pin 1 185 185 185 185 pF max Input Capacitance, Pin 15 and Pin 16 7 7 7 7 pF max Feedthrough at 1 kHz –94 –72 –94 –68 dB max Total Harmonic Distortion –91 –91 –91 –91 dB typ VIN = 6 V rms at 1 kHz Output Noise Voltage Density 70 70 70 70 nV/√Hz max Includes AD711 Amplifier Noise Digital Input Capacitance 7 7 7 7 pF max

Specifications subject to change without notice.

AD7111L/C/U Grades AD7111K/B/T Grades

0.001 0.005 0.001 0.005 dB per % max

These characteristics are included for design guidance only and are not subject

= AGND = DGND = O V, output amplifier AD711 except where noted.

OUT

MIN

, T

MAXTA

= +258CTA = T

MIN

, T

Units Conditions/Comments

MAX

∆VDD = ±10%, Input Code = 00000000

WR Going High, CS = 0 V Amplifier for Code Transition

10000000 to 00000000 C1 of Figure 1 is 0 pF

–2–

REV. 0

AD7111/AD7111A

AD7111A–ELECTRICAL CHARACTERISTICS

(VDD = +5 V, VIN = –10 V dc, I AD711 except where noted)

= AGND = DGND = O V output amplifier

OUT

AD7111AC Grade AD7111AB Grade

Parameter TA = +258CTA = T

MIN

, T

MAXTA

= +258CTA = T

MIN

, T

Units Conditions/Comments

MAX

NOMINAL RESOLUTION 0.375 0.375 0.375 0.375 dB ACCURACY RELATIVE TO

0 dB ATTENUATION

0.375 dB Steps: Accuracy ≤ ±0.17 dB 0 to 36 0 to 36 0 to 30 0 to 30 dB min Guaranteed Attenuation Ranges Monotonic 0 to 54 0 to 54 0 to 48 0 to 48 dB min for Specified Step Sizes

0.75 dB Steps: Accuracy ≤ ±0.35 dB 0 to 48 0 to 42 0 to 42 0 to 36 dB min Monotonic 0 to 72 0 to 66 0 to 72 0 to 60 dB min

1.5 dB Steps: Accuracy ≤ ±0.7 dB 0 to 54 0 to 48 0 to 48 0 to 42 dB min Full Range Is from 0 dB Monotonic Full Range 0 to 78 0 to 85.5 0 to 72 dB min to 88.5 dB

3.0 dB Steps: Accuracy ≤ ±1.4 dB 0 to 66 0 to 54 0 to 60 0 to 48 dB min Monotonic Full Range Full Range Full Range Full Range dB min

6.0 dB Steps: Accuracy ≤ ±2.7 dB 0 to 72 0 to 60 0 to 60 0 to 48 dB min Monotonic Full Range Full Range Full Range Full Range dB min

GAIN ERROR ±0.1 ±0.15 ±0.15 ±0.20 dB max VIN INPUT RESISTANCE 9/11/15 9/11/15 7/11/18 7/11/18 kΩ min/typ/max RFB INPUT RESISTANCE 9.3/11.5/15.7 9.3/11.5/15.7 7.3/11.5/18.8 7.3/11.5/18.8 kΩ min/typ/max DIGITAL INPUTS

VIH (Input High Voltage) 2.4 2.4 2.4 2.4 V min VIL (Input High Voltage) 0.8 0.8 0.8 0.8 V max Input Leakage Current ±1 ±10 ±1 ±10 µA max Digital Inputs = V

SWITCHING CHARACTERISTICS

0 0 0 0 ns min

Chip Select to Write Setup Time 0 0 0 0 ns min Chip Select to Write Hold Time 57 57 57 57 ns min Write Pulse Width 25 25 25 25 ns min Data Valid to Write Setup Time 10 10 10 10 ns min Data Valid to Write Hold Time

POWER SUPPLY

+5 +5 +5 +5 V Digital Inputs = VIL or V 1 2 1 2 mA max CS = WR = 0 V 1 1 1 1 mA max Digital Inputs = 0 V or VDD;

See Figure 6

NOTE

Sample tested at +25°C to ensure compliance.

Specifications subject to change without notice.

AC PERFORMANCE CHARACTERISTICS

to test. VDD = +5 V, VIN = –10 V dc except where noted, I

These characteristics are included for design guidance only and are not subject

= AGND = DGND = O V, output amplifier AD711 except where noted.

OUT

AD7111AC Grade AD7111AB Grade

Parameter TA = +258CTA = T

DC Supply Rejection, ∆Gain/∆V Propagation Delay 1 1.5 1 1.5 µs max Full-Scale Change Measured from

0.001 0.005 0.001 0.005 dB per % max

MIN

, T

MAXTA

= +258CTA = T

MIN

, T

Units Conditions/Comments

MAX

∆VDD = ±10%, Input Code = 00000000

WR Going High, CS = 0 V

Digital-to-Analog Glitch Impulse 10 20 10 20 nV secs typ Measured with AD843 as Output

Amplifier for Code Transition 10000000 to 00000000

C1 of Figure 1 is 0 pF Output Capacitance, Pin 1 50 50 50 50 pF max Input Capacitance, Pin 15 and Pin 16 7 7 7 7 pF max Feedthrough at 1 kHz –94 –90 –92 –90 dB max Total Harmonic Distortion –91 –91 –91 –91 dB typ VIN = 6 V rms at 1 kHz Output Noise Voltage Density 70 70 70 70 nV/√Hz max Includes AD711 Amplifier Noise Digital Input Capacitance 7 7 7 7 pF max

Specifications subject to change without notice.

REV. 0

–3–

AD7111/AD7111A

WARNING!

ESD SENSITIVE DEVICE

ABSOLUTE MAXIMUM RATINGS*

(TA = +25°C unless otherwise noted)

VDD (to DGND) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7 V

(to AGND) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .±35 V

Digital Input Voltage to DGND . . . . . –0.3 V to V

to AGND . . . . . . . . . . . . . . . . . . . . . . . . . .–0.3 V to V

OUT

to AGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .±35 V

RFB

AGND to DGND . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 to V

DGND to AGND . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 to V

+ 0.3 V

DD DD

Power Dissipation, DIP . . . . . . . . . . . . . . . . . . . . . . . . . . 1 W

, Thermal Impedance . . . . . . . . . . . . . . . . . . . . 117°C/W

Lead Temperature (Soldering, 10 secs) . . . . . . . . . +300°C

Power Dissipation, SOIC . . . . . . . . . . . . . . . . . . . . . . . . . 1 W

, Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 75°C/W

Power Dissipation, LCCC . . . . . . . . . . . . . . . . . . . . . . . . 1 W

, Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 76°C/W

Lead Temperature (Soldering, 10 secs) . . . . . . . . . +300°C

Operating Temperature Range

Commercial (K, L Versions) . . . . . . . . . . . . .0°C to +70°C

Industrial (B, C Versions) . . . . . . . . . . . . . –40°C to +85°C

Extended (T, U Versions) . . . . . . . . . . . . –55°C to +125°C

Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C

*Stresses above those listed under “Absolute Maximum Ratings” may cause

permanent damage to the device. This is a stress rating only, and functional operation of the device at these or any other conditions above those listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Lead Temperature (Soldering)

Vapor Phase (60 secs) . . . . . . . . . . . . . . . . . . . . . . .215°C

Infrared (15 secs) . . . . . . . . . . . . . . . . . . . . . . . . . .220°C

CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD7111/AD7111A features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.

ORDERING GUIDES

AD7111A ORDERING GUIDE

Specified

Temperature Accuracy Package

Model Range Range Option

AD7111ABN –40°C to +85°C 0 dB to 60 dB N-16 AD7111ACN –40°C to +85°C 0 dB to 72 dB N-16 AD7111ABR –40°C to +85°C 0 dB to 60 dB R-16 AD7111ACR –40°C to +85°C 0 dB to 72 dB R-16

NOTE

N = Plastic DIP; R = SOIC.

TERMINOLOGY

RESOLUTION: Nominal change in attenuation when moving

between two adjacent codes. MONOTONICITY: The device is monotonic if the analog out-

put decreases (or remains constant) as the digital code increases. FEEDTHROUGH ERROR: That portion of the input signal

which reaches the output when all digital inputs are high. See section on Applications.

OUTPUT LEAKAGE CURRENT: Current which appears on the I

terminal with all digital inputs high.

OUT

TOTAL HARMONIC DISTORTION: A measure of the harmonics introduced by the circuit when a pure sinusoid is applied to the input. It is expressed as the harmonic energy divided by the fundamental energy at the output.

AD7111 ORDERING GUIDE

Specified Temperature Accuracy Package Range Range Option

Model

AD7111KN 0°C to +70°C 0 dB to 60 dB N-16 AD7111BQ –40°C to +85°C 0 dB to 60 dB Q-16 AD7111LN 0°C to +70°C 0 dB to 72 dB N-16 AD7111CQ –40°C to +85°C 0 dB to 72 dB Q-16 AD7111UQ/883B –55°C to +125°C 0 dB to 72 dB Q-16 AD7111TE/883B –55°C to +125°C 0 dB to 60 dB E-20A

NOTES

To order MIL-STD-883B, Class B processed parts, add /883B to part number. Contact local sales office for military data sheet and availability.

N = Plastic DIP; Q = Cerdip; E = LCCC; R = SOIC.

ACCURACY: The difference (measured in dB) between the ideal transfer function as listed in Table I and the actual transfer function as measured with the device.

OUTPUT CAPACITANCE: Capacitance from I

OUT

ground. DIGITAL-TO-ANALOG GLITCH IMPULSE: The amount

of charge injected from the digital inputs to the analog output when the inputs change state. This is normally specified as the area of the glitch in either pA-secs or nV-secs depending upon whether the glitch is measured as a current or voltage signal. Glitch impulse is measured with V

= AGND.

PROPAGATION DELAY: This is a measure of the internal delays of the circuit and is defined as the time from a digital input change to the analog output current reaching 90% of its final value.

–4–

REV. 0

AD7111/AD7111A

PIN CONFIGURATIONS

Write Cycle Timing Diagram

CIRCUIT DESCRIPTION

GENERAL CIRCUIT DESCRIPTION

The AD7111/AD7111A consists of a 17-bit R-2R CMOS multiplying D/A converter with extensive digital logic. The logic translates the 8-bit binary input into a 17-bit word which is used to drive the D/A converter. Input data on the D7-D0 bus is loaded into the input data latches using signals. When using the AD7111, the rising edge of

CS and WR control

WR latches

the input data and initiates the internal data transfer to the decoder. A minimum time t

, the refresh time, is required for

RFSH

the data to propagate through the decoder before a new data write is attempted.

In contrast, the AD7111A

WR input is level triggered to allow

transparent operation of the latches if required. The transfer function for the circuit of Figure 1 is given by:

= –VIN 10 exp –

dB = –0.375 N

0.375 N 20

DIP/SOIC

LCCC

where 0.375 is the step size (resolution) in dB and N is the input code in decimal for values 0 to 239. For 240 ≤ N ≤ 255 the output is zero. Table I gives the output attenuation relative to 0 dB for all possible input codes.

Figure 1. Typical Circuit Configuration

The graphs on the last page give a pictorial representation of the specified accuracy and monotonic ranges for all grades of the AD7111/AD7111A. High attenuation levels are specified with less accuracy than low attenuation levels. The range of monotonic behavior depends upon the attenuation step size used.

Table I. Ideal Attenuation in dB vs. Input Code

D3-D0

D7-D4 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111

0000 0.0 0.375 0.75 1.125 1.5 1.875 2.25 2.625 3.0 3.375 3.75 4.125 4.5 4.875 5.25 5.625 0001 6.0 6.375 6.75 7.125 7.5 7.875 8.25 8.625 9.0 9.375 9.75 10.125 10.5 10.875 11.25 11.625 0010 12.0 12.375 12.75 13.125 13.5 13.875 14.25 14.625 15.0 15.375 15.75 16.125 16.5 16.875 17.25 17.625 0011 18.0 18.375 18.75 19.125 19.5 19.875 20.25 20.625 21.0 21.375 21.75 22.125 22.5 22.875 23.25 23.625

0100 24.0 24.375 24.75 25.125 25.5 25.875 26.25 26.625 27.0 27.375 27.75 28.125 28.5 28.875 29.25 29.625 0101 30.0 30.375 30.75 31.125 31.5 31.875 32.25 32.625 33.0 33.375 33.75 34.125 34.5 34.875 35.25 35.625 0110 36.0 36.375 36.75 37.125 37.5 37.875 38.25 38.625 39.0 39.375 39.75 40.125 40.5 40.875 41.25 41.625 0111 42.0 42.375 42.75 43.125 43.5 43.875 44.25 44.625 45.0 45.375 45.75 46.125 46.5 46.875 47.25 47.625

1000 48.0 48.375 48.75 49.125 49.5 49.875 50.25 50.625 51.0 51.375 51.75 52.125 52.5 52.875 53.25 53.625 1001 54.0 54.375 54.75 55.125 55.5 55.875 56.25 56.625 57.0 57.375 57.75 58.125 58.5 58.875 59.25 59.625 1010 60.0 60.375 60.75 61.125 61.5 61.875 62.25 62.625 63.0 63.375 63.75 64.125 64.5 64.875 65.25 65.625 1011 66.0 66.375 66.75 67.125 67.5 67.875 68.25 68.625 69.0 69.375 69.75 70.125 70.5 70.875 71.25 71.625

1100 72.0 72.375 72.75 73.125 73.5 73.875 74.25 74.625 75.0 75.375 75.75 76.125 76.5 76.875 77.25 77.625 1101 78.0 78.375 78.75 79.125 79.5 79.875 80.25 80.625 81.0 81.375 81.75 82.125 82.5 82.875 83.25 83.625 1110 84.0 84.375 84.75 85.125 85.5 85.875 86.25 86.625 87.0 87.375 87.75 88.125 88.5 88.875 89.25 89.625

1111 MUTE MUTE MUTE MUTE MUTE MUTE MUTE MUTE MUTE MUTE MUTE MUTE MUTE MUTE MUTE MUTE

REV. 0

–5–

AD7111/AD7111A

100

–0.2V

200ns

5V 5V

OUT

C1 = 0pF

C1 = 15pF

DATA CHANGE

MSB

For example, the AD7111L is guaranteed monotonic in 0.375 dB steps from 0 dB to –54 dB inclusive and in 0.75 dB steps from 0 dB to –72 dB inclusive. To achieve monotonic operation over the entire 88.5 dB range it is necessary to select input codes so that the attenuation step size at any point is consistent with the step size guaranteed for monotonic operation at that point.

EQUIVALENT CIRCUIT ANALYSIS

Figure 2 shows a simplified circuit of the D/A converter section of the AD7111/AD7111A, and Figure 3 gives an approximate equivalent circuit.

The current source I

LEAKAGE

tion leakages. The resistor R equivalent output resistance of the device which varies with input code (excluding all 0s code) from 0.8R to 2R. R is typically 12 kΩ. C

is the capacitance due to the N channel switches

OUT

and varies from about 20 pF to 50 pF depending upon the digital input. For further information on CMOS multiplying D/A converters, refer to “CMOS DAC Application Guide” which is available from Analog Devices, Publication Number G872b–8–1/89.

is composed of surface and junc-

as shown in Figure 3 is the

Figure 4. Response of AD7111/AD7111A with AD711

0.4V

100

OUT

10 0%

OUT

200ns5V 5V

DATA CHANGE FROM 80H TO 00H.

MSB DATA CHANGE

C1 = 0pF

C1 = 15pF

Figure 5. Response of AD7111/AD7111A with 1/2 OP275

Figure 2. Simplified D/A Circuit of AD7111/AD7111A

Figure 3. Equivalent Analog Output Circuit of AD7111/AD7111A

DYNAMIC PERFORMANCE

The dynamic performance of the AD7111/AD7111A will depend upon the gain and phase characteristics of the output amplifier, together with the optimum choice of PC board layout and decoupling components. Circuit layout is most important if the optimum performance of the AD7111/AD7111A is to be achieved. Most application problems stem from either poor layout, grounding errors, or inappropriate choice of amplifier.

It is recommended that when using thc AD7111/AD7111A with a high speed amplifier, a capacitor (C1) he connected in the feedback path as shown in Figure 1. This capacitor, which should be between 10 pF and 30 pF, compensates for the phase lag introduced by the output capacitance of the D/A converter. Figures 4 and 5 show the performance of the AD7111/AD7111A using the AD711, a high speed, low cost BiFET amplifier, and the OP275, a dual, bipolar/JFET, audio amplifier. The performance without C1 is shown in the middle trace and the response with C1 in circuit shown in the bottom trace.

In conventional CMOS D/A converter design, parasitic capacitance in N-channel D/A converter switches can give rise to glitches on the D/A converter output. These glitches result from digital feedthrough. The AD7111/AD7111A has been designed to minimize these glitches as much as possible.

For operation beyond 250 kHz, capacitor C1 may be reduced in value. This gives an increase in bandwidth at the expense of a poorer transient response as shown in Figures 5 and 11. In circuits where C1 is not included, the high frequency roll-off point is primarily determined by the characteristics of the output amplifier and not the AD7111/AD7111A.

Feedthrough and absolute accuracy are sensitive to output leakage current effects. For this reason it is recommended that the operating temperature of the AD7111/AD7111A be kept as close to 25°C as is practically possible, particularly where the device’s performance at high attenuation levels is important. A typical

plot of leakage current vs. temperature is shown in Figure 10.

Some solder fluxes and cleaning materials can form slightly conductive films which cause leakage effects between analog input and output. The user is cautioned to ensure that the manufacturing process for circuits using thc AD7111/AD7111A does not allow such films to form. Otherwise the feedthrough, accuracy and maximum usable range will be affected.

STATIC ACCURACY PERFORMANCE

The D/A converter section of the AD7111/AD7111A consists of a 17-bit R-2R type converter. To obtain optimum static performance at this level of resolution it is necessary to pay great attention to amplifier selection, circuit grounding, etc.

Amplifier input has current results in a dc offset at the output of the amplifier due to the current flowing through the feedback resistor R

. It is recommended that an amplifier with an input

bias current of less than 10 nA be used (e.g., AD711) to minimize this offset.

–6–

REV. 0

AD7111/AD7111A

1.0

–1.0

078

0.5

–0.5

0.0

66 726048423630241812 54

ATTENUATION – dB

ERROR – dB

= +85°C

= +25°C

V = +5V

Another error arises from the output amplifier s input offset voltage. The amplifier is operated with a fixed feedback resistance, but the equivalent source impedance (the AD7111/ AD7111A output impedance) varies as a function of attenuation l

evel. This has the effect of varying thc “noise” gain of the

plifier, thus creating a varying error due to amplifier offset voltage. It is recommended that an amplifier with less than 50 µV of input offset be used (such as the AD OP07 in dc appli- cations. Amplifiers with higher offset voltage may cause audible “thumps” in ac applications due to dc output changes.

The AD7111/AD7111A accuracy is specified and tested using only the internal feedback resistor. Any gain error (i.e., mismatch of R

to the R-2R ladder) that may exist in the

Typical Performance Characteristics

= +5V

= +25°C

VINAPPLIED TO ALL DATA INPUTS CS = WR = 0V

AD7111/AD7111A D/A converter circuit results in a constant attenuation error over the whole range. The AD7111/AD7111A accuracy is specified relative to 0 dB attenuation, hence “Gain” trim resistors—R1 and R2 in Figure 1—can be used to adjust V

= VIN precisely (i.e., 0 dB attenuation) with input code

OUT

00000000. The accuracy and monotonic range specifications of the AD7111/AD7111A are not affected in any way by this gain trim procedure. For the AD7111/AD7111A L/C/U grades, suitable values for R1 and R2 of Figure 1 are R1 = 500 Ω, R2 = 180 Ω; for the K/B/T grades, suitable value are R1 = 1000 Ω, R2 = 270 Ω. For additional information on gain error the reader is referred to the “CMOS DAC Application Guide,” available from Analog Devices, Inc., Publication Number G872b–8–1/89.

– mA

INPUT VOLTAGE – Volts

432

Figure 6. Typical Supply Current vs. Logic Input Level

0.4

VDD= +5V T

= +25°C

***

ATTENUATION – dB

0.2

0.0

****

–0.2

ERROR – dB

–0.4

–0.6

Figure 7. Typical Attenuation Error for 0.75 dB Steps

Figure 8. Typical Attenuation Error for 3 dB Steps vs. Temperature

27242118151296

Figure 9. Accuracy Specification for K/B/T Grade Devices

= +25°C

at T

REV. 0

–7–

AD7111/AD7111A–T ypical Performance Characteristics

–60

–80

–100

–90

–70

10 10101010

12345

FREQUENCY – Hz

TOTAL HARMONIC DISTORTION – dB

1/2 OP- 275

AD711

VIN= 6V rms INPUT CODE = 0000 0000

= +25°C

C1 = 15pF

2.0 VDD= +5V

= –10V

– nA

DATA INPUT = 1111XXXX

1.5

OUT

1.0

0.5

OUTPUT LEAKAGE CURRENT I

0.0

–40

–15

35 6010

TEMPERATURE – °C

Figure 10. Output Leakage Current vs. Temperature

1/2 OP – 275 C1 = 15pF

–10

V = +5V

–20

T = +25°C

DATA INPUT CODE = 0000 0000 V = 1V rms

NORMALIZED GAIN WITH RESPECT TO 1kHz

–30

1010

FREQUENCY – Hz

1/2 OP – 275 C1 = 0pF

AD711 C1 = 0pF

AD711 C1 = 15pF

4567

1010 1010

Figure 11. Frequency Response with 1/2 OP275 and AD711 Amplifiers

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).

Plastic DIP (N-16)

Figure 12. Distortion vs. Frequency

Figure 13. Accuracy Specification for L/C/U Grade Devices at T

= +25°C

SOIC (R-16)

C1687–10–7/92

Cerdip (Q-16)

–8–

PRINTED IN U.S.A.

LCCC (E-20A)

REV. 0

Analog Devices AD7111ABR, AD7111ABN, AD7111UQ-883B, AD7111TE-883B, AD7111LN Datasheet

Specifications and Main Features

Frequently Asked Questions

User Manual

PRODUCT HIGHLIGHTS

AD7111–ELECTRICAL CHARACTERISTICS

AC PERFORMANCE CHARACTERISTICS

AD7111A–ELECTRICAL CHARACTERISTICS

AC PERFORMANCE CHARACTERISTICS

TERMINOLOGY

RESOLUTION: Nominal change in attenuation when moving

between two adjacent codes. MONOTONICITY: The device is monotonic if the analog out-

put decreases (or remains constant) as the digital code increases. FEEDTHROUGH ERROR: That portion of the input signal

OUTPUT LEAKAGE CURRENT: Current which appears on the I

TOTAL HARMONIC DISTORTION: A measure of the harmonics introduced by the circuit when a pure sinusoid is applied to the input. It is expressed as the harmonic energy divided by the fundamental energy at the output.

ACCURACY: The difference (measured in dB) between the ideal transfer function as listed in Table I and the actual transfer function as measured with the device.

OUTPUT CAPACITANCE: Capacitance from I

ground. DIGITAL-TO-ANALOG GLITCH IMPULSE: The amount

PROPAGATION DELAY: This is a measure of the internal delays of the circuit and is defined as the time from a digital input change to the analog output current reaching 90% of its final value.

CIRCUIT DESCRIPTION

GENERAL CIRCUIT DESCRIPTION

EQUIVALENT CIRCUIT ANALYSIS

DYNAMIC PERFORMANCE

STATIC ACCURACY PERFORMANCE

Analog Devices AD7111ABR, AD7111ABN, AD7111UQ-883B, AD7111TE-883B, AD7111LN Datasheet

Specifications and Main Features

Frequently Asked Questions

User Manual

PRODUCT HIGHLIGHTS

AD7111–ELECTRICAL CHARACTERISTICS

AC PERFORMANCE CHARACTERISTICS

AD7111A–ELECTRICAL CHARACTERISTICS

AC PERFORMANCE CHARACTERISTICS

TERMINOLOGY

RESOLUTION: Nominal change in attenuation when moving

between two adjacent codes. MONOTONICITY: The device is monotonic if the analog out-

put decreases (or remains constant) as the digital code increases. FEEDTHROUGH ERROR: That portion of the input signal

OUTPUT LEAKAGE CURRENT: Current which appears on the I

TOTAL HARMONIC DISTORTION: A measure of the harmonics introduced by the circuit when a pure sinusoid is applied to the input. It is expressed as the harmonic energy divided by the fundamental energy at the output.

ACCURACY: The difference (measured in dB) between the ideal transfer function as listed in Table I and the actual transfer function as measured with the device.

OUTPUT CAPACITANCE: Capacitance from I

ground. DIGITAL-TO-ANALOG GLITCH IMPULSE: The amount

PROPAGATION DELAY: This is a measure of the internal delays of the circuit and is defined as the time from a digital in­put change to the analog output current reaching 90% of its final value.

CIRCUIT DESCRIPTION

GENERAL CIRCUIT DESCRIPTION

EQUIVALENT CIRCUIT ANALYSIS

DYNAMIC PERFORMANCE

STATIC ACCURACY PERFORMANCE

PROPAGATION DELAY: This is a measure of the internal delays of the circuit and is defined as the time from a digital input change to the analog output current reaching 90% of its final value.