AD AD7948AN-B

a
FEATURES
12-Bit Multiplying DACs
Guaranteed Specifications with +3.3 V/+5 V Supply
0.5 LSBs INL and DNL
Low Power: 5 mW typ
Fast Interface
40 ns Strobe Pulsewidth (AD7943)
40 ns Write Pulsewidth (AD7945, AD7948)
Low Glitch: 60 nV-s with Amplifier Connected
Fast Settling: 600 ns to 0.01% with AD843
+3.3 V/+5 V Multiplying
12-Bit DACs
AD7943/AD7945/AD7948
FUNCTIONAL BLOCK DIAGRAMS
VDD
RFB
AD7943
IOUT1
12-BIT DAC
VREF
IOUT2
CLR
LD1
LD2
DAC REGISTER
AGND
SRI
INPUT SHIFT REGISTER
SRO
APPLICATIONS
Battery-Powered Instrumentation
Laptop Computers
Upgrades for All 754x Series DACs (5 V Designs)
STB1 STB2 STB3 STB4
VDD
GENERAL DESCRIPTION
The AD7943, AD7945 and AD7948 are fast 12-bit multiplying
DACs that operate from a single +5 V supply (Normal Mode)
and a single +3.3 V to +5 V supply (Biased Mode). The
AD7943 has a serial interface, the AD7945 has a 12-bit parallel
interface, and the AD7948 has an 8-bit byte interface. They will
replace the industry-standard AD7543, AD7545 and AD7548
in many applications, and they offer superior speed and power
consumption performance.
The AD7943 is available in 16-lead DIP, 16-lead SOP (Small
Outline Package) and 20-lead SSOP (Shrink Small Outline
Package).
RFB
AD7945
The AD7948 is available in 20-lead DIP, 20-lead SOP and 20lead SSOP.
IOUT1
12-BIT DAC
VREF
AGND
12
CS
WR
INPUT LATCH
12
DB11–DB0
VREF
DGND
RFB
VDD
IOUT1
12-BIT DAC
12
The AD7945 is available in 20-lead DIP, 20-lead SOP and 20lead SSOP.
DGND
AGND
AD7948
DF/DOR
CTRL
DATA OVERRIDE LOGIC
12
LDAC
DAC REGISTER
12
INPUT REGISTERS
WR
CONTROL
LOGIC
CSLSB
12
CSMSB
DATA STEERING LOGIC
8
DB7–DB0
DGND
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
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: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1998
AD7943/AD7945/AD7948–SPECIFICATIONS1
NORMAL MODE
(AD7943: VDD = +4.5 V to +5.5 V; VIOUT1 = VIOUT2 = AGND = 0 V; VREF = +10 V; TA = TMIN to TMAX, unless otherwise noted.
AD7945, AD7948: VDD = +4.5 V to +5.5 V; VIOUT1 = AGND = 0 V; VREF = +10 V; T A = TMIN to TMAX, unless otherwise noted.)
Parameter
B Grades2 T Grade2, 3
Units
Test Conditions/Comments
ACCURACY
Resolution
Relative Accuracy
Differential Nonlinearity
12
± 0.5
± 0.5
12
± 0.5
± 0.5
Bits
LSB max
LSB max
1 LSB = VREF/212 = 2.44 mV when VREF = 10 V
±2
2
5
±2
2
5
LSB max
ppm FSR/°C typ
ppm FSR/°C max
10
100
10
100
nA max
nA max
See Terminology Section
Typically 20 nA over Temperature
6
12
6
12
kΩ min
kΩ max
Typical Input Resistance = 9 kΩ
DIGITAL INPUTS
VINH, Input High Voltage
VINL, Input Low Voltage
IINH , Input Current
CIN, Input Capacitance4
2.4
0.8
±1
10
2.4
0.8
±1
10
V min
V max
µA max
pF max
DIGITAL OUTPUT (AD7943 SRO)
Output Low Voltage (V OL)
Output High Voltage (V OH)
0.2
VDD – 0.2
0.2
VDD – 0.2
V max
V min
4.5/5.5
4.5/5.5
V min/V max
–75
5
–75
5
dB typ
µA max
5
5
µA max
Gain Error
TMIN to TMAX
Gain Temperature Coefficient 4
Output Leakage Current
IOUT1
@ +25°C
TMIN to TMAX
REFERENCE INPUT
Input Resistance
POWER REQUIREMENTS
VDD Range
Power Supply Sensitivity4
∆Gain/∆VDD
IDD (AD7943)
IDD (AD7945, AD7948)
All Grades Guaranteed Monotonic over
Temperature
For 1 CMOS Load
VINH = VDD – 0.1 V min, V INL = 0.1 V max.
SRO Open Circuit. No STB Signal. Typically
1 µA. Typically 100 µA with a 1 MHz STB
Frequency. At Input Levels of 0.8 V and 2.4 V,
IDD Is Typically 2.5 mA.
VINH = VDD – 0.1 V min, V INL = 0.1 V max.
Typically 1 µA. At Input Levels of 0.8 V and
2.4 V, IDD Is Typically 2.5 mA.
NOTES
1
The AD7943, AD7945 and AD7948 are specified in the normal current mode configuration and in the biased current mode for single-supply applications.
Figures 14 and 15 are examples of normal mode operation.
2
Temperature ranges as follows: B Grades: –40°C to +85°C; T Grade: –55°C to +125°C.
3
The T Grade applies to the AD7945 only.
4
Guaranteed by design.
Specifications subject to change without notice.
–2–
REV. B
AD7943/AD7945/AD7948
SPECIFICATIONS1
BIASED MODE
(AD7943: VDD = +3 V to +5.5 V; VIOUT1 = VIOUT2 = AGND = 1.23 V; VREF = +0 V to 2.45 V; TA = TMIN to TMAX, unless otherwise noted. AD7945, AD7948: VDD = +3 V to +5.5 V; VIOUT1 = AGND = 1.23 V; VREF = +0 V to 2.45 V; TA = TMIN to TMAX, unless otherwise noted.)
Parameter
A Grades2 Units
Test Conditions/Comments
ACCURACY
Resolution
12
Bits
Relative Accuracy
Differential Nonlinearity
±1
± 0.9
1 LSB = (VIOUT1 – VREF)/212 = 300 µV When
VIOUT1 = 1.23 V and VREF = 0 V
LSB max
LSB max
Gain Error @ +25°C
TMIN to TMAX
Gain Temperature Coefficient3
±3
±4
2
5
LSB max
LSB max
ppm FSR/°C typ
ppm FSR/°C max
Output Leakage Current
IOUT1
@ +25°C
TMIN to TMAX
Input Resistance
@ IOUT2 Pin (AD7943)
@ AGND Pin (AD7945, AD7948)
See Terminology Section
10
100
nA max
nA max
6
6
kΩ min
kΩ min
DIGITAL INPUTS
VINH, Input High Voltage @ VDD = +5 V
VINH, Input High Voltage @ VDD = +3.3 V
VINL, Input Low Voltage @ VDD = +5 V
VINL, Input Low Voltage @ VDD = +3.3 V
IINH, Input Current
CIN, Input Capacitance3
2.4
2.1
0.8
0.6
±1
10
V min
V min
V max
V max
µA max
pF max
DIGITAL OUTPUT (SRO)
Output Low Voltage (VOL)
Output High Voltage (VOH)
0.2
VDD – 0.2
V max
V min
3.0/5.5
V min/V max
–75
5
dB typ
µA max
5
µA max
POWER REQUIREMENTS
VDD Range
Power Supply Sensitivity3
∆Gain/∆VDD
IDD (AD7943)
IDD (AD7945, AD7948)
All Grades Guaranteed Monotonic
over Temperature
Typically 20 nA over Temperature
This Varies with DAC Input Code
For 1 CMOS Load
VINH = VDD – 0.1 V min, VINL = 0.1 V max.
SRO Open Circuit; No STB Signal; Typically
1 µA. Typically 100 µA with 1 MHz STB
Frequency.
VINH = VDD – 0.1 V min, VINL = 0.1 V max.
Typically 1 µA.
NOTES
1
These specifications apply with the devices biased up at 1.23 V for single supply applications. The model numbering reflects this by means of a “–B” suffix
(for example: AD7943AN-B). Figure 16 is an example of Biased Mode Operation.
2
Temperature ranges as follows: A Versions: –40°C to +85°C.
3
Guaranteed by design.
Specifications subject to change without notice.
REV. B
–3–
AD7943/AD7945/AD7948
AC PERFORMANCE CHARACTERISTICS
NORMAL MODE
(AD7943: VDD = +4.5 V to +5.5 V; VIOUT1 = VIOUT2 = AGND = 0 V. AD7945, AD7948: VDD = +4.5 V to +5.5 V; VIOUT1 =AGND =
0 V. VREF = 6 V rms, 1 kHz sine wave; TA = TMIN to TMAX; DAC output op amp is AD843; unless otherwise noted.) These characteristics are included for Design Guidance and are not subject to test.
Parameter
B Grades
T Grade
Units
Test Conditions/Comments
DYNAMIC PERFORMANCE
Output Voltage Settling Time
600
700
ns typ
Digital to Analog Glitch Impulse
60
60
nV-s typ
Multiplying Feedthrough Error
Output Capacitance
–75
60
30
5
–75
60
30
5
dB max
pF max
pF max
nV-s typ
Digital Feedthrough (AD7945, AD7948) 5
5
nV-s typ
To 0.01% of Full-Scale Range. VREF =
+10 V; DAC Latch Alternately Loaded with
All 0s and All 1s
Measured with VREF = 0 V. DAC Latch
Alternately Loaded with All 0s and All 1s
DAC Latch Loaded with All 0s
All 1s Loaded to DAC
All 0s Loaded to DAC
Feedthrough to the DAC Output with LD1,
LD2 High and Alternate Loading of All 0s
and All 1s into the Input Shift Register
Feedthrough to the DAC Output with CS
High and Alternate Loading of All 0s and
All 1s to the DAC Bus
Total Harmonic Distortion
Output Noise Spectral Density
@ 1 kHz
–83
–83
dB typ
35
35
nV/√Hz typ All 1s Loaded to DAC. VREF = 0 V. Output
Op Amp Is OP07
Digital Feedthrough (AD7943)
Specifications subject to change without notice.
AC PERFORMANCE CHARACTERISTICS
BIASED MODE (AD7943: VDD = +3 V to +5.5 V; VIOUT1 = VIOUT2 = AGND = 1.23 V. AD7945, AD7948: VDD = +3 V to +5.5 V; VIOUT1 = AGND =
1.23 V. VREF = 1 kHz, 2.45 V p-p, sine wave biased at 1.23 V; DAC output op amp is AD820; TA = TMIN to TMAX ; unless otherwise noted.) These
characteristics are included for Design Guidance and are not subject to test.
Parameter
DYNAMIC PERFORMANCE
Output Voltage Settling Time
A Grades
Units
5
µs typ
Digital to Analog Glitch Impulse
60
nV-s typ
Multiplying Feedthrough Error
Output Capacitance
Digital Feedthrough
–75
60
30
5
dB max
pF max
pF max
nV-s typ
Digital Feedthrough (AD7945, AD7948)
5
nV-s typ
Total Harmonic Distortion
Output Noise Spectral Density
@ 1 kHz
–83
dB typ
25
nV/√Hz typ
Test Conditions/Comments
To 0.01% of Full-Scale Range. VREF = 0 V
DAC Latch Alternately Loaded with All 0s and All 1s
VREF = 1.23 V. DAC Register Alternately Loaded
with All 0s and All 1s
DAC Latch Loaded with All 0s
All 1s Loaded to DAC
All 0s Loaded to DAC
Feedthrough to the DAC Output with LD1, LD2
High and Alternate Loading of All 0s and All 1s
into the Input Shift Register
Feedthrough to the DAC Output with CS High
and Alternate Loading of All 0s and All 1s to the
DAC Bus
All 1s Loaded to DAC. VREF = 1.23 V
Specifications subject to change without notice.
–4–
REV. B
AD7943/AD7945/AD7948
AD7943 TIMING SPECIFICATIONS1 (T
A
= TMIN to TMAX, unless otherwise noted)
Limit @
VDD = +3 V to +3.6 V
Limit @
VDD = +4.5 V to +5.5 V
Units
Description
tSTB
tDS
tDH
tSRI
tLD
tCLR
tASB
60
15
35
55
55
55
0
40
10
25
35
35
35
0
ns min
ns min
ns min
ns min
ns min
ns min
ns min
tSV3
60
35
ns max
STB Pulsewidth
Data Setup Time
Data Hold Time
SRI Data Pulsewidth
Load Pulsewidth
CLR Pulsewidth
Min Time Between Strobing Input Shift
Register and Loading DAC Register
STB Clocking Edge to SRO Data Valid Delay
Parameter
2
NOTES
1
All input signals are specified with tr = tf = 5 ns (10% to 90% of 5 V) and timed from a voltage level of 1.6 V. tr and tf should not exceed 1 µs on any digital input.
2
STB mark/space ratio range is 60/40 to 40/60.
3
tSV is measured with the load circuit of Figure 2 and defined as the time required for the output to cross 0.8 V or 2.4 V.
Specifications subject to change without notice.
t STB
STB1,
STB2,
STB4
STB3
tDH
t DS
t SRI
SRI
DB11(N)
(MSB)
DB10(N)
DB0(N)
t ASB
LD1,
LD2,
CLR
SRO
t SV
DB0(N–1)
DB10(N–1)
Figure 1. AD7943 Timing Diagram
1.6mA
TO OUTPUT
PIN
IOL
+2.1V
CL
50pF
200mA
IOH
Figure 2. Load Circuit for Digital Output Timing Specifications
REV. B
–5–
t LD, t CLR
AD7943/AD7945/AD7948
AD7945 TIMING SPECIFICATIONS1 (T = T
A
MIN to T MAX,
unless otherwise noted)
Parameter
Limit @
VDD = +3 V to +3.6 V
Limit @
VDD = +4.5 V to +5.5 V
Units
Description
tDS
tDH
tCS
tCH
tWR
35
10
60
0
60
20
10
40
0
40
ns min
ns min
ns min
ns min
ns min
Data Setup Time
Data Hold Time
Chip Select Setup Time
Chip Select Hold Time
Write Pulsewidth
NOTES
1
All input signals are specified with tr = tf = 5 ns (10% to 90% of 5 V) and timed from a voltage level of 1.6 V.
Specifications subject to change without notice.
tCS
tCH
CS
tWR
WR
tDS
DB11–DB0
tDH
DATA VALID
Figure 3. AD7945 Timing Diagram
AD7948 TIMING SPECIFICATIONS1 (T = T
A
MIN
to TMAX, unless otherwise noted)
Parameter
Limit @
VDD = +3 V to +3.6 V
Limit @
VDD = +4.5 V to +5.5 V
Units
Description
tDS
tDH
tCWS
tCWH
tLWS
tLWH
tWR
45
10
0
0
0
0
60
30
10
0
0
0
0
40
ns min
ns min
ns min
ns min
ns min
ns min
ns min
Data Setup Time
Data Hold Time
CSMSB or CSLSB to WR Setup Time
CSMSB or CSLSB to WR Hold Time
LDAC to WR Setup Time
LDAC to WR Hold Time
Write Pulsewidth
NOTES
1
All input signals are specified with tr = tf = 5 ns (10% to 90% of 5 V) and timed from a voltage level of 1.6 V.
Specifications subject to change without notice.
tCWH
tCWS
CSMSB
tCWH
tCWS
CSLSB
tLWH
tLWS
LDAC
tWR
tWR
WR
tDH
tDS
DB7–DB0
tDH
tDS
DATA
VALID
DATA
VALID
Figure 4. AD7948 Timing Diagram
–6–
REV. B
AD7943/AD7945/AD7948
ABSOLUTE MAXIMUM RATINGS 1
SOP Package, Power Dissipation . . . . . . . . . . . . . . . . . 450 mW
θJA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . . 75°C/W
Lead Temperature, Soldering
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . +215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . +220°C
SSOP Package, Power Dissipation . . . . . . . . . . . . . . . . 875 mW
θJA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 132°C/W
Lead Temperature, Soldering
Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . +215°C
Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . +220°C
(TA = +25°C unless otherwise noted)
VDD to DGND . . . . . . . . . . . . . . . . . . . . . . . . . .–0.3 V to +6 V
IOUT1 to DGND . . . . . . . . . . . . . . . . . . . –0.3 V to VDD + 0.3 V
IOUT2 to DGND . . . . . . . . . . . . . . . . . . . –0.3 V to VDD + 0.3 V
AGND to DGND . . . . . . . . . . . . . . . . . –0.3 V to VDD + 0.3 V
Digital Input Voltage to DGND . . . . . . –0.3 V to VDD + 0.3 V
VRFB, VREF to DGND . . . . . . . . . . . . . . . . . . . . . . . . . . ± 15 V
Input Current to Any Pin Except Supplies2 . . . . . . . . ± 10 mA
Operating Temperature Range
Industrial (A, B Versions) . . . . . . . . . . . . . –40°C to +85°C
Extended (T Version) . . . . . . . . . . . . . . . –55°C to +125°C
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . +150°C
DIP Package, Power Dissipation . . . . . . . . . . . . . . . . 670 mW
θJA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 116°C/W
Lead Temperature, Soldering, (10 sec) . . . . . . . . . . +260°C
NOTES
1
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; 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.
2
Transient currents of up to 100 mA will not cause SCR latch-up.
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 AD7943/AD7945/AD7948 feature 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.
WARNING!
ESD SENSITIVE DEVICE
ORDERING GUIDE
Model
Temperature
Range
Linearity
Error (LSBs)
Nominal
Supply Voltage
Package
Option1
AD7943BN
AD7943BR
AD7943BRS
AD7943AN-B
AD7943ARS-B
AD7945BN
AD7945BR
AD7945BRS
AD7945AN-B
AD7945ARS-B
AD7945TQ
AD7948BN
AD7948BR
AD7948BRS
AD7948AN-B
AD7948ARS-B
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–55°C to +125°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
± 0.5
± 0.5
± 0.5
±1
±1
± 0.5
± 0.5
± 0.5
±1
±1
±1
± 0.5
± 0.5
± 0.5
±1
±1
+5 V
+5 V
+5 V
+3.3 V to +5 V
+3.3 V to +5 V
+5 V
+5 V
+5 V
+3.3 V to +5 V
+3.3 V to +5 V
+5 V
+5 V
+5 V
+5 V
+3.3 V to +5 V
+3.3 V to +5 V
N-16
R-16
RS-20
N-16
RS-20
N-20
R-20
RS-20
N-20
RS-20
Q-20
N-20
R-20
RS-20
N-20
RS-20
NOTE
1
N = Plastic DIP; R = SOP (Small Outline Package); RS = SSOP (Shrink Small Outline Package); Q = Cerdip.
REV. B
–7–
AD7943/AD7945/AD7948
TERMINOLOGY
Relative Accuracy
Output Capacitance
Relative Accuracy or endpoint linearity is a measure of the
maximum deviation from a straight line passing through the
endpoints of the DAC transfer function. It is measured after
adjusting for zero error and full-scale error and is normally
expressed in Least Significant Bits or as a percentage of fullscale reading.
Output Voltage Settling Time
Differential Nonlinearity
Digital to Analog Glitch Impulse
This is the capacitance from the IOUT1 pin to AGND.
This is the amount of time it takes for the output to settle to a
specified level for a full-scale input change. For these devices, it
is specified both with the AD843 as the output op amp in the
normal current mode and with the AD820 in the biased current
mode.
Differential nonlinearity is the difference between the measured
change and the ideal 1 LSB change between any two adjacent
codes. A specified differential nonlinearity of 1 LSB maximum
ensures monotonicity.
This is the amount of charge injected into the analog output
when the inputs change state. It is specified as the area of the
glitch in nV-s. It is measured with the reference input connected
to AGND and the digital inputs toggled between all 1s and all
0s. As with Settling Time, it is specified with both the AD817
and the AD820.
Gain Error
Gain Error is a measure of the output error between an ideal
DAC and the actual device output. It is measured with all 1s
in the DAC after offset error has been adjusted out and is expressed in Least Significant Bits. Gain error is adjustable to
zero with an external potentiometer.
This is the error due to capacitive feedthrough from the DAC
reference input to the DAC IOUT1 terminal, when all 0s are
loaded in the DAC.
Output Leakage Current
Digital Feedthrough
AC Feedthrough Error
Output leakage current is current which flows in the DAC ladder switches when these are turned off. For the IOUT1 terminal,
it can be measured by loading all 0s to the DAC and measuring
the IOUT1 current. Minimum current will flow in the IOUT2 line
when the DAC is loaded with all 1s.
When the device is not selected, high frequency logic activity on
the device digital inputs is capacitively coupled through the
device to show up as noise on the IOUT1 pin and subsequently on
the op amp output. This noise is digital feedthrough.
PIN CONFIGURATIONS
DIP/SOP
SSOP
DIP/SOP/SSOP
DIP/SOP/SSOP
IOUT1 1
16
RFB
IOUT1 1
20
RFB
IOUT1 1
20
RFB
IOUT1 1
20
IOUT2
2
15
VREF
IOUT2 2
19
VREF
AGND 2
19
VREF
AGND 2
19
VREF
AGND 3
14
VDD
AGND 3
18
VDD
DGND 3
18
VDD
DGND 3
18
VDD
AD7943
TOP VIEW 13 CLR
(Not to Scale)
12 DGND
LD1 5
STB1 4
AD7943
TOP VIEW 17 CLR
(Not to Scale)
16 NC
NC 5
AD7945
TOP VIEW 17 WR
(Not to Scale)
16 CS
DB10 5
STB1 4
DB11 4
AD7948
RFB
TOP VIEW 17 WR
(Not to Scale)
16 CSLSB
5
DF/DOR
CSMSB 4
11
STB4
NC 6
15
NC
DB9 6
15
DB0
CTRL 6
15
LDAC
7
10
STB3
LD1 7
14
DGND
DB8 7
14
DB1
DB7 (MSB) 7
14
DB0 (LSB)
STB2 8
9
LD2
SRO 8
13
STB4
DB7 8
13
DB2
DB6 8
13
DB1
SRI 9
12
STB3
DB6 9
12
DB3
DB5 9
12
DB2
11
LD2
DB5 10
11
DB4
DB4 10
11
DB3
SRO 6
SRI
STB2 10
NC = NO CONNECT
–8–
REV. B
AD7943/AD7945/AD7948
AD7943 PIN FUNCTION DESCRIPTIONS
Pin Mnemonic
Description
IOUT1
IOUT2
AGND
DAC current output terminal 1.
DAC current output terminal 2. This should be connected to the AGND pin.
This pin connects to the back gates of the current steering switches. In normal operation, it should be connected
to the signal ground of the system. In biased single-supply operation it may be biased to some voltage between
0 V and the 1.23 V. See Figure 11 for more details.
This is the Strobe 1 input. Data is clocked into the input shift register on the rising edge of this signal. STB3
must be high. STB2, STB4 must be low.
Active low inputs. When both of these are low, the DAC register is updated and the output will change to
reflect this.
Serial Data Input. Data on this line will be clocked into the input shift register on one of the Strobe inputs,
when they are enabled.
This is the Strobe 2 input. Data is clocked into the input shift register on the rising edge of this signal.
STB3 must be high. STB1, STB4 must be low.
This is the Strobe 3 input. Data is clocked into the input shift register on the falling edge of this signal. STB1,
STB2, STB4, must be low.
This is the Strobe 4 input. Data is clocked into the input shift register on the rising edge of this signal. STB3
must be high. STB1, STB2 must be low.
Digital Ground.
Asynchronous CLR input. When this input is taken low, all 0s are loaded to the DAC latch.
Power supply input. This is nominally +5 V for Normal Mode Operation and +3.3 V to +5 V for Biased
Mode Operation.
DAC reference input.
DAC feedback resistor pin.
STB1
LD1, LD2
SRI
STB2
STB3
STB4
DGND
CLR
VDD
VREF
RFB
AD7945 PIN FUNCTION DESCRIPTIONS
Pin Mnemonic
Description
IOUT1
AGND
DAC current output terminal 1.
This pin connects to the back gates of the current steering switches. The DAC IOUT2 terminal is also connected
internally to this point.
Digital Ground.
Digital Data Inputs.
Active Low, Chip Select Input.
Active Low, Write Input.
Power supply input. This is nominally +5 V for Normal Mode Operation and +3.3 V to +5 V for Biased Mode
Operation.
DAC reference input.
DAC feedback resistor pin.
DGND
DB11–DB0
CS
WR
VDD
VREF
RFB
REV. B
–9–
AD7943/AD7945/AD7948
AD7948 PIN FUNCTION DESCRIPTIONS
Pin Mnemonic
Description
IOUT1
AGND
DAC current output terminal 1. Normally terminated at the virtual ground of output amplifier.
Analog Ground Pin. This pin connects to the back gates of the current steering switches. The DAC IOUT2
terminal is also connected internally to this point.
Digital Ground Pin.
DGND
CSMSB
Chip Select Most Significant Byte. Active Low Input. Used in combination with WR to load external data into
the input register or in combination with LDAC and WR to load external data into both input and DAC registers.
DF/DOR
Data Format/Data Override. When this input is low, data in the DAC register is forced to one of two override
codes selected by CTRL. When the override signal is removed, the DAC output returns to reflect the value in
the DAC register. With DF/DOR high, CTRL selects either a left or right justified input data format. For normal
operation, DF/DOR is held high. See Table I.
Table I. Truth Table for DF/DOR CTRL
DF/DOR
CTRL
Function
0
0
1
1
0
1
0
1
DAC Register Contents Overridden by All 0s
DAC Register Contents Overridden by All 1s
Left-Justified Input Data Selected
Right-Justified Input Data Selected
CTRL
Control Input. See DF/DOR description.
DB7–DB0
Digital Data Inputs.
LDAC
Load DAC input, active low. This signal, in combination with others, is used to load the DAC register from
either the input register or the external data bus.
CSLSB
Chip Select Least Significant (LS) Byte. Active Low Input. Used in combination with WR to load external data
into the input register or in combination with WR and LDAC to load external data into both input and DAC
registers.
Table II. Truth Table for AD7948 Write Operation
WR
CSMSB
CSLSB
LDAC
Function
0
0
0
0
0
1
1
1
0
0
1
X
0
0
1
1
1
X
1
0
1
0
0
X
Load LS Byte to Input Register
Load LS Byte to Input Register and DAC Register
Load MS Byte to Input Register
Load MS Byte to Input Register and DAC Register
Load Input Register to DAC Register
No Data Transfer
WR
Write input, active low. This active low signal, in combination with others is used in loading external data into
the AD7948 input register and in transferring data from the input register to the DAC register.
VDD
VREF
Power supply input. This is nominally +5 V for Normal Mode Operation and +3.3 V to +5 V for Biased Mode
Operation.
DAC reference input.
RFB
DAC feedback resistor pin.
–10–
REV. B
AD7943/AD7945/AD7948
Typical Performance Curves
0.5
0.50
LINEARITY ERROR – LSBS
0.4
DNL – LSBS
VDD = +5V
VREF = +10V
OP AMP = AD843
TA = +258C
VDD = +5V
TA = +258C
OP AMP = AD843
0.3
0.2
0.25
0.00
–0.25
0.1
0
–0.50
2
4
6
VREF – Volts
8
10
Figure 5. Differential Nonlinearity Error vs.
VREF (Normal Mode)
3072
2048
INPUT CODE
4095
Figure 7. All Codes Linearity In Normal Mode (V DD = +5 V)
1.0
6
VDD = +5V
TA = +258C
OP AMP = AD843
0.9
1024
0
VDD = +3.3V
TA = +258C
OP AMP = AD820
5
0.8
INL, DNL – LSBS
INL – LSBS
0.7
0.6
0.5
0.4
0.3
0.2
4
3
2
1
0.1
0
2
4
6
VREF – Volts
8
0
0.2
10
Figure 6. Integral Nonlinearity Error vs.
VREF (Normal Mode)
REV. B
0.4
0.6
0.8
1.0
|VREF – VBIAS| – Volts
1.2
1.4
Figure 8. Linearity Error vs. VREF (Biased Mode)
–11–
AD7943/AD7945/AD7948
LINEARITY ERROR – LSBS
1.00
VDD = +3.3V
VREF = 0V
VBIAS = 1.23V
OP AMP = AD820
TA = +258C
0.50
5V
200ns
100
90
VDD = +5V
TA = +258C
VREF = 0V
OP AMP = AD711
0.00
AD711 OUTPUT
10
–0.50
0%
50mV
200ns
–1.00
0
2048
INPUT CODE
1024
3072
4095
Figure 9. All Codes Linearity in Biased Mode
(VDD = +3.3 V)
Figure 11. Digital-to-Analog Glitch Impulse
–50
0
VDD = +5V
TA = +258C
VIN = 6V rms
OP AMP = AD711
–55
THD – dBs
–60
–20
–65
–30
–70
–40
–75
–50
–80
–60
–85
–70
–90
–80
–95
–100
100
VDD = +5V
TA = +258C
VIN = 20V p-p
OP AMP = AD711
–10
DAC LOADED WITH ALL 1S
DAC LOADED WITH ALL 0S
–90
1k
10k
FREQUERCY – Hz
–100
100k
1k
Figure 10. Total Harmonic Distortion vs. Frequency
10k
100k
FREQUENCY – Hz
1M
10M
Figure 12. Multiplying Frequency Response vs.
Digital Code
–12–
REV. B
AD7943/AD7945/AD7948
GENERAL DESCRIPTION
D/A Section
UNIPOLAR BINARY OPERATION
(Two-Quadrant Multiplication)
The AD7943, AD7945 and AD7948 are 12-bit current-output
D/A converters. A simplified circuit diagram is shown in Figure 13. The DAC architecture is segmented. This means that
the 2 MSBs of the 12-bit data word are decoded to drive the
three switches A, B and C. The remaining 10 bits of the data
word drive the switches S0 to S9 in a standard inverting R-2R
ladder configuration.
Figure 14 shows the standard unipolar binary connection diagram for the AD7943, AD7945 and AD7948. When VIN is an
ac signal, the circuit performs two-quadrant multiplication.
Resistors R1 and R2 allow the user to adjust the DAC gain
error. With a specified gain error of 2 LSBs over temperature,
these are not necessary in many applications. Circuit offset is
due completely to the output amplifier offset. It can be removed by adjusting the amplifier offset voltage. Alternatively,
choosing a low offset amplifier makes this unnecessary.
Each of the switches A to C steers 1/4 of the total reference
current into either IOUT1 or IOUT2 with the remaining 1/4 of the
total current passing through the R-2R section. Switches S9 to
S0 steer binarily weighted currents into either IOUT1 or IOUT2. If
IOUT1 and IOUT2 are kept at the same potential, a constant current flows in each ladder leg, regardless of digital input code.
Thus, the input resistance seen at VREF is always constant. It is
equal to R/2. The VREF input may be driven by any reference
voltage or current, ac or dc that is within the Absolute Maximum Ratings.
A1 should be chosen to suit the application. For example, the
OP07 is ideal for very low bandwidth applications (10 kHz or
R2 10V
RFB
VIN
VOUT = –D × VREF
where D is the fractional representation of the digital word
loaded to the DAC. D can be set from 0 to 4095/4096, since it
has 12-bit resolution.
2R
C
2R
B
R
2R
A
2R
S9
AGND
VOUT
A1: OP07
AD711
AD843
AD845
SIGNAL GROUND
NOTES
1. ONLY ONE DAC IS SHOWN FOR CLAIRITY.
2. DIGITAL INPUT CONNECTIONS ARE OMITTED.
3. C1 PHASE COMPENSATION (5 – 15pF) MAY BE REQUIRED
WHEN USING HIGH SPEED AMPLIFIER.
Figure 14. Unipolar Binary Operation
lower) while the AD711 is suitable for medium bandwidth applications (200 kHz or lower). For high bandwidth applications
of greater than 200 kHz, the AD843 and AD847 offer very fast
settling times.
The code table for Figure 14 is shown in Table III.
Table III. Unipolar Binary Code
R
2R
S8
A1
IOUT2
AD7943/45/48
VREF
R
DAC
R1 20V
The device provides access to the VREF, RFB, and IOUT1 terminals of the DAC. This makes the device extremely versatile and
allows it to be configured in several different operating modes.
Examples of these are shown in the following sections. The
AD7943 also has a separate IOUT2 pin. In the AD7945 and
AD7948 this is internally tied to AGND.
When an output amplifier is connected in the standard configuration of Figure 14, the output voltage is given by:
C1
IOUT1
VREF
2R
2R
S0
R/2
RFB
IOUT1
IOUT2
SHOWN FOR ALL 1S ON DAC
Figure 13. Simplified D/A Circuit Diagram
Digital Input
MSB
LSB
Analog Output
(VOUT as Shown in Figure 14)
1111 1111 1111
1000 0000 0001
1000 0000 0000
0111 1111 1111
0000 0000 0001
0000 0000 0000
–VREF (4095/4096)
–VREF (2049/4096)
–VREF (2048/4096)
–VREF (2047/4096)
–VREF (1/4096)
–VREF (0/4096) = 0
NOTE
Nominal LSB size for the circuit of Figure 14 is given by: V REF (1/4096).
REV. B
–13–
AD7943/AD7945/AD7948
BIPOLAR OPERATION
(Four-Quadrant Multiplication)
SINGLE SUPPLY APPLICATIONS
Figure 15 shows the standard connection diagram for bipolar
operation of the AD7943, AD7945 and AD7948. The coding is
offset binary as shown in Table IV. When VIN is an ac signal,
the circuit performs four-quadrant multiplication. Resistors R1
and R2 are for gain error adjustment and are not needed in
many applications where the device gain error specifications are
adequate. To maintain the gain error specifications, resistors
R3, R4 and R5 should be ratio matched to 0.01%.
R4 20kV
R2 10V
RFB
VIN
R5
20kV
C1
IOUT1
VREF
DAC
R1 20V
IOUT2
R3
A1
10kV
A2
AD7943/45/48
VOUT
AGND
SIGNAL GROUND
NOTES
1. ONLY ONE DAC IS SHOWN FOR CLAIRITY.
2. DIGITAL INPUT CONNECTIONS ARE OMITTED.
3. C1 PHASE COMPENSATION (5 – 15pF) MAY BE REQUIRED
WHEN USING HIGH SPEED AMPLIFIER, A1.
Figure 15. Bipolar Operation (Four-Quadrant
Multiplication)
The “-B” versions of the devices are specified and tested for
single supply applications. Figure 16 shows the recommended
circuit for operation with a single +5 V to +3.3 V supply. The
IOUT2 and AGND terminals are biased to 1.23 V. Thus, with 0 V
applied to the VREF terminal, the output will go from 1.23 V (all
0s loaded to the DAC) to 2.46 V (all 1s loaded). With 2.45 V
applied to the VREF terminal, the output will go from 1.23 V (all
0s loaded) to 0.01 V (all 1s loaded). It is important when considering INL in a single-supply system to realize that most
single-supply amplifiers cannot sink current and maintain zero
volts at the output. In Figure 16, with VREF = 2.45 V the required sink current is 200 µA. The minimum output voltage
level is 10 mV. Op amps like the OP295 are capable of maintaining this level while sinking 200 µA.
Figure 16 shows the IOUT2 and AGND terminals being driven
by an amplifier. This is to maintain the bias voltage at 1.23 V
as the impedance seen looking into the IOUT2 terminal changes.
This impedance is code dependent and varies from infinity (all
0s loaded in the DAC) to about 6 kΩ minimum. The AD589
has a typical output resistance of 0.6 Ω and it can be used to
drive the terminals directly. However, this will cause a typical
linearity degradation of 0.2 LSBs. If this is unacceptable then
the buffer amplifier is necessary. Figure 9 shows the typical
linearity performance of the AD7943/AD7945/AD7948 when
used as in Figure 16 with VDD set at +3.3 V and VREF = 0 V.
Suitable dual amplifiers for use with Figure 15 are the OP270
(low noise, low bandwidth, 15 kHz), the AD712 (medium
bandwidth, 200 kHz) or the AD827 (wide bandwidth, 1 MHz).
+3.3V
VDD
Table IV. Bipolar (Offset Binary) Code
Table Digital Input
MSB
LSB
Analog Output
(VOUT as Shown in Figure 15)
1111 1111 1111
1000 0000 0001
1000 0000 0000
0111 1111 1111
0000 0000 0001
0000 0000 0000
+VREF (2047/2048)
+VREF (1/2048)
+VREF (0/2048) = 0
–VREF (1/2048)
–VREF (2047/2048)
–VREF (2048/2048) = –VREF
VIN
RFB
C1
IOUT1
VREF
DAC
IOUT2
AD7943/45/48
AGND
A1
VOUT
A1: OP295
AD822
OP283
DGND
+5V
5.6kV
A1
AD589
SIGNAL GROUND
Figure 16. Single Supply System
NOTE
Nominal LSB size for the circuit of Figure 15 is given by: V REF (1/2048).
–14–
REV. B
AD7943/AD7945/AD7948
MICROPROCESSOR INTERFACING
AD7943 to ADSP-2101 Interface
AD7945 to MC68000 Interface
Figure 19 shows the MC68000 interface to the AD7945. The
appropriate data is written into the DAC in one MOVE instruction to the appropriate memory location.
Figure 17 shows the AD7943 to ADSP-2101 interface diagram.
The DSP is set up for alternate inverted framing with an internally generated SCLK. TFS from the ADSP-2101 drives the
STB1 input on the AD7943. The serial word length should be
set at 12. This is done by making SLEN = 11 (1011 binary).
The SLEN field is Bits 3–0 in the SPORT control register
(0x3FF6 for SPORT0 and 0x3FF2 for SPORT1).
A1 – A23
MC68000
AS
With the 16 MHz version of the ADSP-2101, the maximum
output SCLK is 8 MHz. The AD7943 setup and hold time of
10 ns and 25 ns mean that it is compatible with the DSP when
running at this speed.
ADDRESS
DECODE
CS
AD7945
DTACK
WR
R/W
The OUTPUT FLAG drives both LD1 and LD2 and is brought
low to update the DAC register and change the analog output.
DB11 – DB0
D15 – D0
+5V
AD7943
ADSP-2101
CLR
TFS
STB1
SCLK
STB3
DT
SRI
OUTPUT FLAG
LD1
Figure 19. AD7945 to MC68000 Interface
AD7948 to Z80 Interface
Figure 20 is the interface between the AD7948 and the 8-bit
bus of the Z80 processor. Three write operations are needed to
load the DAC. The first two load the MS byte and the LS byte
and the third brings the LDAC low to update the output.
LD2
STB2
STB4
ADDRESS BUS
A0 – A15
Figure 17. AD7943 to ADSP-2101 Interface
Z80
AD7943 to DSP56001 Interface
Figure 18 shows the interface diagram for the AD7943 to the
DSP56001. The DSP56001 is configured for normal mode
synchronous operation with gated clock. The serial clock, SCK,
is set up as an output from the DSP and the serial word length
is set for 12 bits (WL0 = 1, WL1 = 0, in Control Register A).
SCK from the DSP56001 is applied to the AD7943 STB3 input. Data from the DSP56000 is valid on the falling edge of
SCK and this is the edge which clocks the data into the AD7943
shift register. STB1, STB2 and STB4 are tied low on the
AD7943 to permanently enable the STB3 input.
+5V
AD7943
DSP56001
CLR
SCK
STB3
STD
SRI
OUTPUT FLAG
LD1
LD2
STB1
STB2
ADDRESS
DECODE
CSLSB
LDAC
AD7948
WR
WR
DB7 – DB0
D7 – D0
DATA BUS
Figure 20. AD7948 to Z80 Interface
When the 12-bit serial word has been written to the AD7943,
the LD1, LD2 inputs are brought low to update the DAC
register.
STB4
Figure 18. AD7943 to DSP56001 Interface
REV. B
CSMSB
MREQ
–15–
AD7943/AD7945/AD7948
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
16-Lead Plastic DIP (N-16)
16-Lead SOP (R-16)
16
9
1
8
PIN 1
0.280 (7.11)
0.240 (6.10)
0.060 (1.52)
0.015 (0.38)
0.210 (5.33)
MAX
0.160 (4.06)
0.115 (2.93)
1
8
0.1043 (2.65)
0.0926 (2.35)
PIN 1
0.0118 (0.30)
0.0040 (0.10)
0.015 (0.381)
0.008 (0.204)
0.070 (1.77) SEATING
0.045 (1.15) PLANE
8° 0.0500 (1.27)
0.0192 (0.49)
SEATING 0.0125 (0.32) 0° 0.0157 (0.40)
0.0138 (0.35) PLANE
0.0091 (0.23)
0.0500
(1.27)
BSC
20-Lead Plastic DIP (N-20)
20-Lead Cerdip (Q-20)
0.005 (0.13) MIN
1.060 (26.90)
0.925 (23.50)
20
1
PIN 1
0.060 (1.52)
0.015 (0.38)
0.210 (5.33)
MAX
0.130
(3.30)
MIN
0.160 (4.06)
0.115 (2.93)
20
11
1
10
0.100
(2.54)
BSC
0.070 (1.77) SEATING
0.045 (1.15) PLANE
0.310 (7.87)
0.220 (5.59)
0.325 (8.25)
0.300 (7.62) 0.195 (4.95)
0.115 (2.93)
PIN 1
1.060 (26.92) MAX
0.200 (5.08)
MAX
0.320 (8.13)
0.290 (7.37)
0.150
(3.81)
MIN
0.200 (5.08)
0.125 (3.18)
0.015 (0.381)
0.008 (0.204)
0.023 (0.58)
0.014 (0.36)
20-Lead SOP (R-20)
0.100
(2.54)
BSC
0.070 (1.78) SEATING 15°
0.030 (0.76) PLANE
0°
0.015 (0.38)
0.008 (0.20)
20-Lead SSOP (RS-20)
0.295 (7.50)
0.271 (6.90)
1
10
0.1043 (2.65)
0.0926 (2.35)
0.311 (7.9)
0.301 (7.64)
11
0.4193 (10.65)
0.3937 (10.00)
20
0.2992 (7.60)
0.2914 (7.40)
0.5118 (13.00)
0.4961 (12.60)
0.0118 (0.30)
0.0040 (0.10)
0.060 (1.52)
0.015 (0.38)
0.0291 (0.74)
x 45°
0.0098 (0.25)
20
11
1
10
0.07 (1.78)
0.066 (1.67)
0.078 (1.98) PIN 1
0.068 (1.73)
8° 0.0500 (1.27)
0.0500 0.0192 (0.49)
0° 0.0157 (0.40)
(1.27) 0.0138 (0.35) SEATING 0.0125 (0.32)
PLANE
BSC
0.0091 (0.23)
0.008 (0.203)
0.002 (0.050)
–16–
0.212 (5.38)
0.205 (5.21)
0.022 (0.558)
0.014 (0.356)
PIN 1
0.098 (2.49) MAX
11
0.280 (7.11)
10 0.240 (6.10)
0.0291 (0.74)
x 45°
0.0098 (0.25)
0.0256
(0.65)
BSC
8°
SEATING 0.009 (0.229) 0°
PLANE
0.005 (0.127)
0.037 (0.94)
0.022 (0.559)
REV. B
PRINTED IN U.S.A.
0.100
(2.54)
BSC
9
0.325 (8.26)
0.300 (7.62) 0.195 (4.95)
0.115 (2.93)
0.130
(3.30)
MIN
0.022 (0.558)
0.014 (0.356)
16
0.2992 (7.60)
0.2914 (7.40)
0.4193 (10.65)
0.3937 (10.00)
0.840 (21.34)
0.745 (18.92)
C1901b–0–5/98
0.4133 (10.50)
0.3977 (10.00)