LC
2
MOS
Microprocessor-Compatible 14-Bit DAC
AD7538
FEATURES
All grades 14-bit monotonic over the full temperature range
Low cost, 14-bit upgrade for 12-bit systems
14-bit parallel load with double buffered inputs
Small 24-pin, 0.30” DIP and SOIC
Low output leakage (<20 nA) over the full temperature range
FUNCTIONAL BLOCK DIAGRAM
V
DD
23
AD7538
V
REF 1
14-BIT DAC
2
3
4
R
FB
I
OUT
AGND
LDAC
APPLICATIONS
Microprocessor-based control systems
Digital audio
Precision servo control
Control and measurement in high temperature environments
DAC REGISTER
20
INPUT
REGISTER
14
6
19
5
24
21
22
CS
WR
01139-001
DB13 TO DB0
DGND
V
SS
Figure 1.
GENERAL DESCRIPTION
The AD7538 is a 14-bit monolithic CMOS digital-to-analog
converter (DAC) that uses laser trimmed thin-film resistors to
achieve excellent linearity.
The DAC is loaded by a single 14-bit wide word using standard
chip select and memory write logic. Double buffering, which is
optional using LDAC, allows simultaneous updates in a system
containing multiple AD7538s.
A novel low leakage configuration enables the AD7538 to
exhibit excellent output leakage current characteristics over
the specified temperature range.
The AD7538 is manufactured using the linear-compatible
CMOS (LC
2
MOS) process. It is speed compatible with most
microprocessors and accepts TTL or CMOS logic level inputs.
PRODUCT HIGHLIGHTS
1.
Guaranteed Monotonicity.
The AD7538 is guaranteed monotonic to 14-bits over the
full temperature range for all grades.
Low Cost.
The AD7538, with its 14-bit dynamic range, affords a low
cost solution for 12-bit system upgrades.
Small Package Size.
The AD7538 is packaged in a small 24-pin, 0.3" DIP and a
24-pin SOIC.
Low Output Leakage.
By tying V
SS
(Pin 24) to a negative voltage, it is possible to
achieve a low output leakage current at high temperatures.
Wide Power Supply Tolerance.
The device operates on a +12 V to +15 V V
DD
, with a ±5%
tolerance on this nominal figure. All specifications are
guaranteed over this range.
2.
3.
4.
5.
Rev. B
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 that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2009 Analog Devices, Inc. All rights reserved.
AD7538
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
Functional Block Diagram .............................................................. 1
General Description ......................................................................... 1
Product Highlights ........................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
AC Performance Characteristics ................................................ 4
Timing Characteristics ................................................................ 4
Timing Diagram ........................................................................... 5
Absolute Maximum Ratings............................................................ 6
ESD Caution .................................................................................. 6
Pin Configuration and Function Descriptions ............................. 7
Terminology ...................................................................................... 8
DAC Section ...................................................................................... 9
Circuit Information ........................................................................ 10
Equivalent Circuit Analysis ...................................................... 10
Digital Section ............................................................................ 10
Unipolar Binary Operation (2-Quadrant Multiplication) .... 10
Bipolar Operation (4-Quadrant Multiplication) .................... 11
Low Leakage Configuration...................................................... 11
Programmable Gain Amplifier ................................................. 12
Application Hints ........................................................................... 13
Output Offset .............................................................................. 13
General Ground Management.................................................. 13
Microprocessor Interfacing ....................................................... 13
AD7538-to-8086 Interface ........................................................ 13
AD7538-to-MC68000 Interface ............................................... 13
Digital Feedthrough ................................................................... 14
Outline Dimensions ....................................................................... 15
Ordering Guide .......................................................................... 16
REVISION HISTORY
1/09—Rev. A to Rev. B
Updated Format .................................................................. Universal
Changes to Table 1 ............................................................................ 3
Updated Outline Dimensions ....................................................... 15
Changes to Ordering Guide .......................................................... 15
5/87—Rev. 0 to Rev. A
Rev. B | Page 2 of 16
AD7538
SPECIFICATIONS
V
DD
= 11.4 V to 15.75 V
1
, V
REF
= 10 V; V
PIN3
= V
PIN4
= 0 V, V
SS
= −300 mV; all specifications T
MIN
to T
MAX
, unless otherwise noted.
Table 1.
Parameter
2
ACCURACY
Resolution
Relative Accuracy
Differential Nonlinearity
Full-Scale Error
+25°C
T
MIN
to T
MAX
Gain Temperature Coefficient
3
;
ΔGain/ΔTemperature
Output Leakage Current
I
OUT
(Pin 3)
25°C
T
MIN
to T
MAX
T
MIN
to T
MAX
REFERENCE INPUT
Input Resistance (Pin 1)
DIGITAL INPUTS
V
IH
(Input High Voltage)
V
IL
(Input Low Voltage)
I
IN
(Input Current)
25°C
T
MIN
to T
MAX
C
IN
(Input Capacitance)
3
POWER SUPPLY
V
DD
Range
V
SS
Range
I
DD
A, J
Versions
14
±2
±1
±4
±8
±2
B, K
Versions
14
±1
±1
±4
±5
±2
S Version
14
±2
±1
±4
±10
±2
T Version
14
±1
±1
±4
±6
±2
Unit
Bits
LSB max
LSB max
LSB max
LSB max
ppm/°C typ
Test Conditions/Comments
All grades guaranteed
monotonic
Over temperature
Measured using internal R
FB
DAC
Registers loaded with all 1s
±5
±10
±25
3.5
10
2.4
0.8
±1
±10
7
11.4/15.75
−200/−500
4
500
±5
±10
±25
3.5
10
2.4
0.8
±1
±10
7
11.4/15.75
−200/−500
4
500
±5
±20
±150
3.5
10
2.4
0.8
±1
±10
7
11.4/15.75
−200/−500
4
500
±5
±20
±150
3.5
10
2.4
0.8
±1
±10
7
11.4/15.75
−200/−500
4
500
nA max
nA max
nA max
kΩ min
kΩ max
V min
V max
μA max
μA max
pF max
V min/V max
mV min/
mV max
mA max
μA max
All digital inputs 0 V
V
SS
= –300 mV
V
SS
= 0 V
Typical input resistance = 6 kΩ
V
IN
= 0 V or V
DD
Specification guaranteed over
this range
Specification guaranteed over
this range
All digital inputs are V
IL
or V
IH
All digital inputs are 0 V or V
DD
1
2
Specifications are guaranteed for a V
DD
of 11.4 V to 15.75 V. At V
DD
= 5 V, the device is fully functional with degraded specifications.
Temperature range as follows: J, K Versions: 0°C to +70°C
A, B Versions: −25°C to +85°C
S, T Versions: −55°C to +125°C
3
Sample tested to ensure compliance.
Rev. B | Page 3 of 16
AD7538
AC PERFORMANCE CHARACTERISTICS
These characteristics are included for design guidance only and are not subject to test. V
DD
= 11.4 V to 15.75 V, V
REF
= 10 V, V
PIN3
= V
PIN4
=
0 V, V
SS
= 0 V or −300 mV, output amplifier is
AD711
except where noted.
Table 2.
Parameter
Output Current Settling Time
T
A
= 25°C
T
A
= T
MIN
, T
MAX
1.5
Unit
μs max
Test Conditions/Comments
To 0.003% of full-scale range
I
OUT
load= 100 Ω, C
EXT
= 13 pF DAC register alternately loaded
with all 1s and all 0s; typical value of settling time is 0.8 μs
Measured with V
REF
= 0 V. I
OUT
load = 100 Ω, C
EXT
= 13 pF; DAC
register alternately loaded with all 1s and all 0s
V
REF
= ±10 V, 10 kHz sine wave DAC
Register loaded with all 0s
ΔV
DD
= ±5%
DAC register loaded with all 1s
DAC register loaded with all 0s
Measured between R
FB
and I
OUT
Digital-to-Analog Glitch Impulse
Multiplying Feedthrough Error
Power Supply Rejection
ΔGain/ΔV
DD
Output Capacitance
C
OUT
(Pin 3)
C
OUT
(Pin 3)
Output Noise Voltage Density
(10 Hz to 100 kHz)
20
3
5
nV-sec typ
mV p-p typ
±0.01
260
130
15
±0.02
260
130
% per % max
pF max
pF max
nV√Hz typ
TIMING CHARACTERISTICS
V
DD
= 11.4 V to 15.75 V, V
REF
= 10 V, V
PIN3
= V
PIN4
= 0 V, V
SS
= 0 V or −300 mV. All specifications T
MIN
to T
MAX
unless otherwise noted. See
Figure 2 for a timing diagram.
Table 3.
Parameter
1
t
1
t
2
t
3
t
4
t
5
t
6
1
Limit at
T
A
= +25°C
0
0
170
170
140
20
Limit at T
A
= 0°C to +70°C
T
A
= −25°C to +85°C
0
0
200
200
160
20
Limit at
T
A
= −55°C to +125°C
0
0
240
240
180
30
Unit
ns min
ns min
ns min
ns min
ns min
ns min
Test Conditions/Comments
CS to WR setup time
CS to WR hold time
LDAC pulse width
Write pulse width
Data setup time
Data hold time
Temperature range as follows: J, K Versions: 0°C to +70°C
A, B Versions: −25°C to +85°C
S, T Versions: −55°C to +125°C
Rev. B | Page 4 of 16
AD7538
TIMING DIAGRAM
t
1
CS
t
2
5V
0V
t
3
LDAC
5V
0V
t
4
WR
5V
0V
t
5
DATA
t
6
5V
0V
NOTES
1. ALL INPUT SIGNAL RISE AND FALL TIMES MEASURES FROM 10%
TO 90% OF 5V,
t
R
=
t
F
= 20ns.
V
IH
+ V
IL
2. TIMING MEASUREMENT REFERENCE LEVEL IS
.
2
3. IF LDAC IS ACTIVATED PRIOR TO THE RISING EDGE OF WR,
THEN IT MUST STAY LOW FOR
t
3
OR LONGER AFTER WR GOES HIGH.
Figure 2. Timing Diagram
Rev. B | Page 5 of 16
01139-002
