64-Position OTP Digital Potentiometer
AD5273
FEATURES
APPLICATIONS
System calibrations
Electronics level settings
Mechanical potentiometers and trimmer replacement
Automotive electronics adjustments
Transducer circuit adjustments
Programmable filters up to 6 MHz BW 3
GENERAL DESCRIPTION
The AD5273 is a 64-position, one-time programmable (OTP)
digital potentiometer 4 that employs fuse link technology to
achieve permanent program setting. This device performs the
same electronic adjustment function as most mechanical
trimmers and variable resistors. It allows unlimited adjustments
before permanently setting the resistance values. The AD5273 is
programmed using a 2-wire, I2C®-compatible digital control.
During write mode, a fuse blow command is executed after the
final value is determined, thereby freezing the wiper position at
a given setting (analogous to placing epoxy on a mechanical
trimmer). When the permanent setting is achieved, the value
does not change, regardless of the supply variations or environmental stresses under normal operating conditions. To verify the
success of permanent programming, Analog Devices, Inc.,
patterned the OTP validation such that the fuse status can be
discerned from two validation bits in the read mode.
FUNCTIONAL BLOCK DIAGRAM
SCL
SDA
AD0
A
I2C INTERFACE
AND
CONTROL LOGIC
B
AD5273
WIPER
REGISTER
VDD
GND
W
03224-001
64 positions
One-time programmable (OTP) 1 set-and-forget
Resistance setting—low cost alternative over EEMEM
Unlimited adjustments prior to OTP activation
1 kΩ, 10 kΩ, 50 kΩ, 100 kΩ end-to-end terminal resistance
Compact 8-lead SOT-23 standard package
Ultralow power: IDD = 5 μA maximum
Fast settling time: tS = 5 μs typical during power-up
I2C-compatible digital interface
Computer software 2 replaces microcontroller in
factory programming applications
Wide temperature range: −40°C to +105°C
Low operating voltage: 2.7 V to 5.5 V
OTP validation check function
FUSE
LINK
Figure 1.
In addition, for applications that program the AD5273 at the
factory, Analog Devices offers device programming software2
running on Windows® NT®, Windows 2000, and Windows XP
operating systems. This software application effectively replaces
any external I2C controllers, which in turn enhances the user
system’s time-to-market.
The AD5273 is available in 1 kΩ, 10 kΩ, 50 kΩ, and 100 kΩ
resistances and in a compact 8-lead SOT-23 standard package.
It operates from −40°C to +105°C.
Along with its unique OTP feature, the AD5273 lends itself
well to general digital potentiometer applications due to its
effective resolution, array resistance options, small footprint,
and low cost.
An AD5273 evaluation kit and software are available. The kit
includes the connector and cable that can be converted for
factory programming applications.
For applications that require dynamic adjustment of resistance
settings with nonvolatile EEMEM, users should refer to the
AD523x and AD525x families of nonvolatile memory digital
potentiometers.
1
OTP allows unlimited adjustments before permanent setting.
Analog Devices cannot guarantee the software to be 100% compatible to all
systems due to the wide variation in computer configurations.
3
Applies to 1 kΩ parts only.
4
The terms digital potentiometer, VR, and RDAC are used interchangeably.
2
Rev. G
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 ©2002–2008 Analog Devices, Inc. All rights reserved.
AD5273
TABLE OF CONTENTS
Features .............................................................................................. 1
Power Supply Considerations ................................................... 15
Applications ....................................................................................... 1
Controlling the AD5273 ................................................................ 16
General Description ......................................................................... 1
Software Programming ............................................................. 16
Functional Block Diagram .............................................................. 1
I2C Controller Programming .................................................... 17
Revision History ............................................................................... 2
Controlling Two Devices on One Bus ..................................... 18
Specifications..................................................................................... 4
Applications Information .............................................................. 19
Absolute Maximum Ratings............................................................ 6
DAC.............................................................................................. 19
ESD Caution .................................................................................. 6
Programmable Voltage Source with Boosted Output ........... 19
Pin Configuration and Function Descriptions ............................. 7
Programmable Current Source ................................................ 19
Typical Performance Characteristics ............................................. 8
Gain Control Compensation .................................................... 19
Theory of Operation ...................................................................... 13
Programmable Low-Pass Filter ................................................ 20
One-Time Programming ........................................................... 13
Level Shift for Different Voltages Operation .......................... 20
Variable Resistance and Voltage for Rheostat Mode ............. 14
RDAC Circuit Simulation Model ............................................. 20
Variable Resistance and Voltage for Potentiometer Mode .... 14
Evaluation Board ............................................................................ 21
ESD Protection ........................................................................... 15
Outline Dimensions ....................................................................... 22
Terminal Voltage Operating Range.......................................... 15
Ordering Guide .......................................................................... 22
Power-Up/Power-Down Sequences ......................................... 15
REVISION HISTORY
6/08—Rev. E to Rev. F
Updated Fuse Blow Condition to 400 ms Throughout ............... 5
1/08—Rev. E to Rev. F
Changes to Table 1 ............................................................................ 4
Changes to Table 2 ............................................................................ 6
Changes to Table 3 ............................................................................ 7
Inserted Figure 28 ........................................................................... 12
Changes to One-Time Programming Section ............................ 13
Changes to Power Supply Considerations Section..................... 15
Deleted Figure 35 ............................................................................ 15
Changes to Figure 36 ...................................................................... 15
Updated Outline Dimensions ....................................................... 22
Changes to Ordering Guide .......................................................... 22
1/05—Rev. D to Rev. E
Changes to Features.......................................................................... 1
Changes to Specifications ................................................................ 3
Changes to Table 3 ............................................................................ 6
Changes to Power Supply Considerations Section..................... 15
Changes to Figure 35 and Figure 37............................................. 15
Changes to DAC Section ............................................................... 19
Changes to Level Shift for Different Voltages
Operation Section........................................................................... 20
Deleted the Resistance Scaling Section ....................................... 20
Deleted the Resolution Enhancement Section ........................... 20
12/04—Rev. C to Rev. D
Updated Format .................................................................. Universal
Changes to Specifications .................................................................3
Changes to Theory of Operation Section.................................... 13
Changes to Power Supply Consideration Section ...................... 15
Changes to Figure 35, Figure 36, and Figure 37 ......................... 15
11/03—Rev. B to Rev. C
Changes to SDA Bit Definitions and Descriptions .................... 10
Changes to One-Time Programming (OTP) Section................ 11
Changes to Table III ....................................................................... 11
Changes to Power Supply Considerations .................................. 13
Changes to Figure 8, Figure 9, and Figure 10 ............................. 13
Rev. G | Page 2 of 24
AD5273
10/03—Rev. A to Rev. B
Changes to Features .......................................................................... 1
Changes to Applications ................................................................... 1
Changes to Specifications ................................................................. 2
Changes to Absolute Maximum Ratings ........................................ 4
Changes to Pin Function Descriptions........................................... 5
Changes to TPC 7, TPC 8, TPC 13, and TPC 14 Captions ......... 7
Deleted TPC 20; Renumbered Successive TPCs ........................... 9
Change to TPC 21 Caption .............................................................. 9
Change to the SDA Bit Definitions and Descriptions ................10
Replaced Theory of Operation Section ........................................11
Replaced Determining the Variable Resistance and
Voltage Section ................................................................................11
Replaced ESD Protection section.................................................. 12
Replaced Terminal Voltage Operating Range Section ............... 12
Replaced Power-Up Sequence Section ......................................... 12
Replaced Power Supply Considerations Section ......................... 13
Changes to Application section ..................................................... 16
Change to Equation 9 ..................................................................... 17
Deleted Digital Potentiometer Family Selection Guide ............. 19
6/03—Rev. 0 to Rev. A
Change to Specifications .................................................................. 2
Change to Power Supply Considerations Section ....................... 12
Updated Outline Dimensions........................................................ 20
12/02—Revision 0: Initial Version
Rev. G | Page 3 of 24
AD5273
SPECIFICATIONS
VDD = 2.7 V to 5.5 V, VA < VDD, VB = 0 V, −40°C < TA < +105°C, unless otherwise noted.
Table 1.
Parameter
DC CHARACTERISTICS—RHEOSTAT MODE
Resolution
Resistor Differential Nonlinearity 2
10 kΩ, 50 kΩ, 100 kΩ
1 kΩ
Resistor Nonlinearity2
10 kΩ, 50 kΩ, 100 kΩ
1 kΩ
Nominal Resistance Tolerance 3
10 kΩ, 50 kΩ, 100 kΩ
Nominal Resistance, 1 kΩ
Rheostat Mode Temperature
Coefficient 4
Wiper Resistance
DC CHARACTERISTICS—POTENTIOMETER
DIVIDER MODE
Differential Nonlinearity 5
Integral Nonlinearity5
Voltage Divider4 Temperature Coefficient
Full-Scale Error
10 kΩ, 50 kΩ, 100 kΩ
1 kΩ
Zero-Scale Error
10 kΩ, 50 kΩ, 100 kΩ
1 kΩ
RESISTOR TERMINALS
Voltage Range 6
Capacitance 7 A, B
Capacitance7 W
Common-Mode Leakage
DIGITAL INPUTS AND OUTPUTS
Input Logic High (SDA and SCL) 8
Symbol
Conditions
Min
Typ 1
N
R-DNL
Max
Unit
6
Bits
LSB
LSB
LSB
LSB
LSB
RWB, VA = NC
RWB, VA = NC
−0.5
−1
+0.05
+0.25
+0.5
+1
RWB, VA = NC
RWB, VA = NC
TA = 25°C
−0.5
−5
+0.10
+2
+0.5
+5
R-INL
ΔRAB/RAB
−30
0.8
+30
1.6
%
kΩ
ppm/°C
60
100
Ω
+0.1
+0.5
+0.5
LSB
LSB
ppm/°C
LSB
LSB
LSB
LSB
LSB
LSB
RAB
(ΔRAB/RAB)/∆T
Wiper = NC
1.2
300
RW
IW = VDD/R, VDD = 3 V or 5 V
DNL
INL
(ΔVW/VW)/ΔT
VWFSE
Code = 0x20
Code = 0x3F
VWZSE
Code = 0x00
VA, VB, VW
CA, CB
CW
ICM
−0.5
−0.5
VIL
Input Logic High (ADO)
Input Logic Low (ADO)
Input Logic Current
Input Capacitance7
Output Logic Low (SDA)
Three-State Leakage Current
Output Capacitance7
VIH
VIL
IIL
CIL
VOL
IOZ
COZ
0
0
0
0
1
5
GND
f = 5 MHz, measured to GND, code =
0x20
f = 1 MHz, measured to GND, code =
0x20
V A = VB = V W
VIH
Input Logic Low (SDA and SCL)8
10
−1
−1
−6
−6
0
0
25
VDD
V
pF
55
pF
1
nA
0.7
VDD
−0.5
VIN = 0 V or 5 V
3.0
0
0.01
3
VDD +
0.5
+0.3
VDD
VDD
0.4
1
0.4
±1
3
Rev. G | Page 4 of 24
V
V
V
V
μA
pF
V
μA
pF
AD5273
Parameter
POWER SUPPLIES
Power Supply Range
OTP Power Supply8, 9
Supply Current
OTP Supply Current8, 10,11
Power Dissipation 12
Power Supply Sensitivity
DYNAMIC CHARACTERISTICS7, 13, 14
Bandwidth, −3 dB
Symbol
Conditions
VDD
VDD_OTP
IDD
IDD_OTP
PDISS
PSRR
PSRR
TA = 25°C
VIH = 5 V or VIL = 0 V
TA = 25°C, VDD_OTP = 5 V
VIH = 5 V or VIL = 0 V, VDD = 5 V
RAB = 1 kΩ
RAB = 10 kΩ, 50 kΩ, 100 kΩ
Total Harmonic Distortion
BW_1 kΩ
BW_10 kΩ
BW_50 kΩ
BW_100 kΩ
THDW
Adjustment Settling Time
tS1
Power-Up Settling Time—
After Fuses Blown
Resistor Noise Voltage
INTERFACE TIMING CHARACTERISTICS7, 14, 15
SCL Clock Frequency
tBUF Bus Free Time Between
Stop and Start
tHD; STA Hold Time
(Repeated Start)
tLOW Low Period of SCL Clock
tHIGH High Period of SCL Clock
tSU; STA Setup Time for
Start Condition
tHD; DAT Data Hold Time
tSU; DAT Data Setup Time
tF Fall Time of Both SDA and
SCL Signals
tR Rise Time of Both SDA and
SCL Signals
tSU; STO Setup Time for Stop Condition
OTP Program Time
tS2
eN_WB
2.7
4.75
Typ 1
5
0.1
100
0.5
−0.3
−0.05
RAB = 1 kΩ, code = 0x20
RAB = 10 kΩ, code = 0x20
RAB = 50 kΩ, code = 0x20
RAB = 100 kΩ, code = 0x20
VA = 1 V rms, RAB = 1 kΩ, VB = 0 V, f = 1
kHz
VA = 5 V ± 1 LSB error band, VB = 0 V,
measured at VW
VA = 5 V ± 1 LSB error band, VB = 0 V,
measured at VW, VDD = 5 V
RAB = 1 kΩ, f = 1 kHz, code = 0x20
Applies to all parts
fSCL
t1
t2
Min
Max
Unit
5.5
5.25
5
V
V
μA
mA
µW
%/%
%/%
27.5
+0.3
+0.05
6000
600
110
60
0.05
kHz
kHz
kHz
kHz
%
5
μs
5
μs
3
nV/√Hz
400
After this period, the first clock pulse is
generated
1.3
kHz
μs
0.6
μs
t3
t4
t5
1.3
0.6
0.6
t6
t7
t8
0.1
50
0.9
t9
t10
t11
0.6
400
1
μs
μs
0.3
μs
μs
μs
0.3
μs
μs
ms
Typical values represent average readings at 25°C, VDD = 5 V, and VSS = 0 V.
Resistor position nonlinearity error, R-INL, is the deviation from an ideal value measured between the maximum resistance and the minimum resistance wiper
positions. R-DNL measures the relative step change from ideal between successive tap positions. Parts are guaranteed monotonic.
3
VAB = VDD, wiper (VW) = no connect.
4
∆RWB/∆T = ∆RWA/∆T. Temperature coefficient is code-dependent; see the Typical Performance Characteristics section.
5
INL and DNL are measured at VW. INL with the RDAC configured as a potentiometer divider similar to a voltage output DAC. VW with the RDAC configured as a
potentiometer divider similar to a voltage output DAC. VA = VDD and VB = 0 V. DNL specification limits of ±1 LSB maximum are guaranteed monotonic operating
conditions.
6
The A, B, and W resistor terminals have no limitations on polarity with respect to each other.
7
Guaranteed by design; not subject to production test.
8
The minimum voltage requirement on the VIH is 0.7 × VDD. For example, VIH min = 3.5 V when VDD = 5 V. It is typical for the SCL and SDA resistors to be pulled up to VDD.
However, care must be taken to ensure that the minimum VIH is met when the SCL and SDA are driven directly from a low voltage logic controller without pull-up resistors.
9
Different from the operating power supply; the power supply for OTP is used one time only.
10
Different from the operating current; the supply current for OTP lasts approximately 400 ms for the one time it is needed.
11
See Figure 28 for the energy plot during the OTP program.
12
PDISS is calculated from (IDD × VDD). CMOS logic level inputs result in minimum power dissipation.
13
Bandwidth, noise, and settling time depend on the terminal resistance value chosen. The lowest R value results in the fastest settling time and highest bandwidth.
The highest R value results in the minimum overall power consumption.
14
All dynamic characteristics use VDD = 5 V.
15
See Figure 29 for the location of the measured values.
2
Rev. G | Page 5 of 24
AD5273
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted.
Table 2.
Parameter
VDD to GND
VA, VB, VW to GND
Maximum Current
IWB, IWA Pulsed
IWB Continuous (RWB ≤ 1 kΩ, A Open) 1
IWA Continuous (RWA ≤ 1 kΩ, B Open)
Digital Input and Output Voltage to GND
Operating Temperature Range
Maximum Junction Temperature (TJ max)
Storage Temperature
Reflow Soldering
Peak Temperature
Time at Peak Temperature
Thermal Resistance θJA, SOT-23 2
Rating
−0.3 V +6.5 V
GND, VDD
±20 mA
±4 mA
±4 mA
0 V, VDD
−40°C to +105°C
150°C
−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; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
ESD CAUTION
260°C
20 sec to 40 sec
230°C/W
1
Maximum terminal current is bounded by the maximum current handling
of the switches, the maximum power dissipation of the package; the maximum applied voltage across any two of the A, B, and W terminals at a given
resistance.
2
Package power dissipation = (TJ max – TA)/θJA.
Rev. G | Page 6 of 24
AD5273
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
W 1
8
AD5273
A
B
TOP VIEW
GND 3 (Not to Scale) 6 AD0
SCL 4
7
5
SDA
03224-002
VDD 2
Figure 2. Pin Configuration
Table 3. Pin Function Descriptions
Pin No.
1
2
Mnemonic
W
VDD
3
4
GND
SCL
5
SDA
6
7
8
AD0
B
A
Description
Wiper Terminal W. GND ≤ VW ≤ VDD.
Positive Power Supply. Specified for nonOTP operation from 2.7 V to 5.5 V. For OTP programming, VDD_OTP must
be within the window of 4.75 V and 5.25 V and be capable of driving 100 mA.
Common Ground.
Serial Clock Input. Requires a pull-up resistor. If it is driven directly from a logic controller without the pull-up
resistor, ensure that the VIH minimum is 0.7 × VDD.
Serial Data Input/Output. Requires a pull-up resistor. If it is driven directly from a logic controller without the
pull-up resistor, ensure that the VIH minimum is 0.7 × VDD.
I2C Device Address Bit. Allows a maximum of two AD5273 devices to be addressed.
Resistor Terminal B. GND ≤ VB ≤ VDD.
Resistor Terminal A. GND ≤ VA ≤ VDD.
Rev. G | Page 7 of 24
AD5273
TYPICAL PERFORMANCE CHARACTERISTICS
0.5
0.10
RAB = 10kΩ
POTENTIOMETER MODE DNL (LSB)
0.3
VDD = 3V
0.1
TA = –40°C
TA = +85°C
TA = +125°C
0.02
–0.02
–0.1
VDD = 5V
–0.3
TA = +25°C
–0.06
03224-003
–0.5
0.06
0
8
16
24
32
40
CODE (Decimal)
48
56
–0.10
64
03224-006
RHEOSTAT MODE INL (LSB)
RAB = 10kΩ
TA = 25°C
0
Figure 3. RINL vs. Code vs. Supply Voltages
24
32
40
CODE (Decimal)
48
POTENTIOMETER MODE INL (LSB)
0.15
VDD = 5V
0.05
VDD = 3V
0.06
3V
0.02
5V
03224-004
0
8
16
24
32
40
CODE (Decimal)
48
56
–0.10
64
03224-007
–0.06
–0.15
0
Figure 4. RDNL vs. Code vs. Supply Voltages
8
16
24
32
40
CODE (Decimal)
48
56
64
Figure 7. INL vs. Code vs. Supply Voltages
0.10
0.10
POTENTIOMETER MODE DNL (LSB)
RAB = 10kΩ
0.06
TA = +85°C
TA = +125°C
0.02
–0.02
RAB = 10kΩ
TA = 25°C
0.06
3V
0.02
–0.02
TA = +25°C
0
8
16
24
32
40
CODE (Decimal)
48
56
5V
–0.06
03224-005
–0.06
TA = –40°C
–0.10
64
Figure 5. INL vs. Code vs. Temperature
03224-008
POTENTIOMETER MODE INL (LSB)
64
RAB = 10kΩ
TA = 25°C
–0.02
–0.05
–0.10
56
0.10
RAB = 10kΩ
TA = 25°C
RHEOSTAT MODE DNL (LSB)
16
Figure 6. DNL vs. Code vs. Temperature
0.25
–0.25
8
0
8
16
24
32
40
CODE (Decimal)
48
Figure 8. DNL vs. Code vs. Supply Voltages
Rev. G | Page 8 of 24
56
64
AD5273
1.0
TA = 25°C
RAB = 10kΩ
CODE = 0x20
0.020
RAB = 10kΩ
0.9
0.8
0.7
ZSE (LSB)
0.015
0.010
0.6
0.5
VDD = 3V
0.4
VDD = 5V
0.3
0.005
0
1
2
3
4
SUPPLY VOLTAGE (V)
5
03224-012
0
0.2
03224-009
POTENTIOMETER MODE LINEARITY (LSB)
0.025
0.1
0
–40
6
80
100
0.16
TA = 25°C
RAB = 10kΩ
CODE = 0x20
SUPPLY CURRENT (μA)
0.3
VDD = 5.5V
RAB = 10kΩ
0.14
0.2
0.1
0
0.12
0.10
0.08
0
1
2
3
4
SUPPLY VOLTAGE (V)
5
0.04
–55
6
Figure 10. RINL vs. Supply Voltage
–35
–15
5
25
45
65
TEMPERATURE (°C)
85
105
115
Figure 13. Supply Current vs. Temperature
10
0
RAB = 10kΩ
–0.1
1
–0.2
–0.4
SUPPLY CURRENT (mA)
VDD = 5V
–0.3
VDD = 3V
–0.5
–0.6
–0.7
VDD = 5V
TA = 25°C
RAB = 10kΩ
ALL DIGITAL
PINS TIED
TOGETHER
0.1
VDD = 2.7V
0.01
03224-011
–0.9
–20
0
20
40
60
TEMPERATURE (°C)
80
0.0001
100
Figure 11. Full-Scale Error
03224-014
0.001
–0.8
–1.0
–40
03224-013
0.06
03224-010
RHEOSTAT MODE LINEARITY (LSB)
0.4
FSE (LSB)
20
40
60
TEMPERATURE (°C)
Figure 12. Zero-Scale Error
Figure 9. INL vs. Supply Voltage
–0.1
0
–20
0
1
2
3
4
INPUT LOGIC VOLTAGE (V)
5
Figure 14. Supply Current vs. Digital Input Voltage
Rev. G | Page 9 of 24
6
AD5273
VDD = 5.5V
TA = 25°C
400
300
0x10
MAGNITUDE (dB)
–12
10kΩ
100
0
0x08
–18
0x04
–24
0x02
–30
0x01
–36
50kΩ
–100
–42
0
16
8
24
32
40
CODE (Decimal)
48
56
03224-018
0x00
100kΩ
–200
–300
0x20
–6
1kΩ
200
0x3F
0
–48
03224-015
RHEOSTAT MODE TEMPCO (ppm/°C)
500
–54
100
64
1k
10k
FREQUENCY (Hz)
100k
1M
Figure 18. Gain vs. Frequency vs. Code, RAB = 10 kΩ
Figure 15. Rheostat Mode Tempco (∆RWB/RWB)/∆T vs. Code
VDD = 5.5V
30
1kΩ
MAGNITUDE (dB)
0
–10
–20
50kΩ
0x08
–18
0x04
–24
0x02
–30
0x01
–36
0
16
8
24
32
40
CODE (Decimal)
48
56
–48
–54
100
64
Figure 16. Potentiometer Mode Tempco (∆VW/VW)/∆T vs. Code
MAGNITUDE (dB)
–30
0x02
0x01
0x00
0x08
–18
0x04
–24
0x02
–30
0x01
–36
–42
–48
–54
100
1k
10k
100k
FREQUENCY (Hz)
1M
03224-020
–42
03224-017
MAGNITUDE (dB)
0x04
–24
–36
1M
0x10
–12
0x08
–18
100k
0x20
–6
0x10
–12
10k
FREQUENCY (Hz)
0x3F
0
0x20
–6
0x00
1k
Figure 19. Gain vs. Frequency vs. Code, RAB = 50 kΩ
0x3F
0
03224-019
–42
–30
–40
0x10
–12
10
100kΩ
0x20
–6
10kΩ
20
0x3F
0
03224-016
RHEOSTAT MODE TEMPCO (ppm/°C)
40
–48
–54
100
10M
Figure 17. Gain vs. Frequency vs. Code, RAB = 1 kΩ
0x00
1k
10k
FREQUENCY (Hz)
100k
Figure 20. Gain vs. Frequency vs. Code, RAB = 100 kΩ
Rev. G | Page 10 of 24
1M
AD5273
12
1kΩ
6
10kΩ
0
VDD = 5.5V
VA = 5.5V
VB = GND
fCLK = 400kHz
MAGNITUDE (dB)
–6
–12
DATA 0x00
0x3F
50kΩ
–18
VW = 5V/DIV
100kΩ
–24
–30
SCL = 5V/DIV
–42
–48
100
1k
10k
100k
FREQUENCY (Hz)
1M
10M
5V
5V
5μs
03224-024
03224-021
–36
Figure 24. Large Settling Time
Figure 21. −3 dB Bandwidth
TA = 25°C
CODE = 0x20
VA = 2.5V, VB = 0V
VDD = 5.5V
VA = 5.5V
VB = GND
fCLK = 100kHz
DATA 0x20
0x1F
–60
VDD = 5V DC ±1.0V p-p AC
–40
VDD = 3V DC ±0.6V p-p AC
VW = 50mV/DIV
–20
03224-022
1k
10k
FREQUENCY (Hz)
SCL = 5V/DIV
50mV
1M
100k
5V
Figure 22. PSRR vs. Frequency
Figure 25. Midscale Glitch Energy
fCLK = 100kHz
VDD = 5.5V
VA = 5.5V
VB = GND
200ns
03224-025
0
100
OTP PROGRAMMED AT MS
VDD = 5.5V
VA = 5.5V
RAB = 10kΩ
VW = 1V/DIV
VW = 10mV/DIV
w
VDD = 5V/DIV
5V
500ns
03224-023
SCL = 5V/DIV
10mV
1V
Figure 23. Digital Feedthrough
5V
5µs
03224-026
POWER SUPPLY REJECTION RATIO (dB)
–80
Figure 26. Power-Up Settling Time After Fuses Blown
Rev. G | Page 11 of 24
AD5273
VA = VB = OPEN
TA = 25°C
RAB = 1kΩ
RAB = 10kΩ
1
RAB = 50kΩ
0.1
RAB = 100kΩ
0
8
16
24
32
40
CODE (Decimal)
48
64
56
03224-060
CH1 20.0mAΩ
Figure 27. IWB_MAX vs. Code
M200ns
A CH1
T
588.000ns
t8
t9
t6
SCL
t2
t4
t3
t8
t5
t7
t10
t9
t1
SDA
P
32.4mA
Figure 28. OTP Program Energy Plot for Single Fuse
S
P
Figure 29. Interface Timing Diagram
Rev. G | Page 12 of 24
03224-028
0.01
1
03224-027
THEORETICAL IWB_MAX (mA)
10
AD5273
THEORY OF OPERATION
AD5273 requires a VDD_OTP between 4.75 V and 5.25 V to
blow the fuses to achieve a given nonvolatile setting. During
operation, however, VDD can be 2.7 V to 5.5 V. Therefore, a
system supply that is lower than 4.75 V requires an external
supply for OTP. The user is allowed only one attempt to blow
the fuses. If the user fails to blow the fuses on the first attempt,
the fuse structure may change such that they can never be
blown, regardless of the energy applied during subsequent events.
For details, see the Power Supply Considerations section.
The AD5273 is a one-time programmable (OTP), set-and-forget,
6-bit digital potentiometer. The AD5273 allows unlimited 6-bit
adjustments prior to the OTP. OTP technology is a proven costeffective alternative over EEMEM in one-time memory
programming applications. The AD5273 employs fuse link
technology to achieve the memory retention of the resistance
setting function. It comprises six data fuses, which control the
address decoder for programming the RDAC, one user mode
test fuse for checking setup error, and one programming lock
fuse for disabling any further programming once the data fuses
are programmed correctly.
The device control circuit has two validation bits, E1 and E0,
that can be read back in the read mode to check the programming status, as shown in Figure 32. Users should always read
back the validation bits to ensure that the fuses are properly
blown. After the fuses have been blown, all fuse latches are
enabled upon subsequent power-on; therefore, the output
corresponds to the stored setting. Figure 30 shows a detailed
functional block diagram.
ONE-TIME PROGRAMMING
Prior to OTP activation, the AD5273 presets to midscale during power-on. After the wiper is set to the desired position, the
resistance can be permanently set by programming the T bit
and the one-time VDD_OTP to high and by coding the part
properly (see Figure 31). The fuse link technology of the
A
SCL
I2C
SDA
INTERFACE
DECODER
MUX
DAC
REG.
W
B
COMPARATOR
FUSES
EN
FUSE
REG.
03224-031
ONE-TIME
PROGRAM/TEST
CONTROL BLOCK
S
0
1
0
1
1
0
AD0
0
A
T
X
SLAVE ADDRESS BYTE
X
X
X
X
X
X
A
X
X
D5
INSTRUCTION BYTE
D4
D3
D2
D1
D0
A
DATA BYTE
P
03224-029
Figure 30. Detailed Functional Block Diagram
S
0
1
0
1
1
0
AD0
1
A
E1
E0
SLAVE ADDRESS BYTE
D5
D4
D3
DATA BYTE
D2
D1
D0
A
P
03224-030
Figure 31. SDA Write Mode Bit Format
Figure 32. SDA Read Mode Bit Format
SDA Bit Definitions and Descriptions
S = start condition.
P = stop condition.
A = acknowledge.
X = don’t care.
T = OTP programming bit. Logic 1 programs wiper position
permanently.
D5, D4, D3, D2, D1, D0 = data bits.
E1, E0 = OTP validation bits.
0, 0 = ready to program.
0, 1 = test fuse not blown successfully. (For factory setup
checking purpose only. Users should not see these
combinations.)
1, 0 = fatal error. Do not retry. Discard the unit.
1, 1 = programmed successfully. No further adjustments
possible.
AD0 = I2C device address bit. Allows maximum of two
AD5273s to be addressed.
Rev. G | Page 13 of 24
AD5273
The general equation for this operation is
VARIABLE RESISTANCE AND VOLTAGE FOR
RHEOSTAT MODE
If only the W-to-B or W-to-A terminals are used as variable
resistors, the unused A or B terminal can be opened or shorted
with W. This operation is called rheostat mode (see Figure 33).
B
03224-032
B
W
Figure 33. Rheostat Mode Configuration
The nominal resistance, RAB, of the RDAC has 64 contact points
accessed by the wiper terminal, plus the B terminal contact if
RWB is considered. The 6-bit data in the RDAC latch is decoded
to select one of the 64 settings. Assuming that a 10 kΩ part is
used, the wiper’s first connection starts at Terminal B for Data
Register 0x00. This connection yields a minimum of 60 Ω
resistance between Terminal W and Terminal B because of the
60 Ω wiper contact resistance. The second connection is the
first tap point, which corresponds to 219 Ω (RW = 1 × RAB/63 +
RW) for Data Register 0x01, and so on. Each LSB data value
increase moves the wiper up the resistor ladder until the last
tap point is reached at 10,060 Ω (63 × RAB/63 + RW). Figure 34
shows a simplified diagram of the equivalent RDAC circuit.
The general equation determining RWB is
RWB (D ) =
D
× RAB + RW
63
Table 4. RWB vs. Codes; RAB = 10 kΩ; Terminal A Opened
D (Dec)
63
32
1
0
RWB (Ω)
10,060
5139
219
60
Table 5. RWA vs. Codes; RAB =10 kΩ; Terminal B Opened
D (Dec)
63
32
1
0
RWA (Ω)
60
4980
9901
10,060
Output State
Full scale (RAB + RW)
Midscale
1 LSB
Zero scale (wiper contact resistance)
Output State
Full scale
Midscale
1 LSB
Zero scale
The typical distribution of the resistance tolerance from device
to device is process-lot dependent, and it is possible to have
±30% tolerance.
A
D5
D4
D3
D2
D1
D0
RS
RS
W
RS
RDAC
LATCH
AND
DECODER
(1)
where:
D is the decimal equivalent of the 6-bit binary code.
RAB is the end-to-end resistance.
RW is the wiper resistance contributed by the on resistance of
the internal switch.
(2)
B
03224-033
W
W
B
A
63 − D
× RAB + RW
63
Figure 34. AD5273 Equivalent RDAC Circuit
VARIABLE RESISTANCE AND VOLTAGE FOR
POTENTIOMETER MODE
If all three terminals are used, the operation is called the
potentiometer mode. The most common configuration is
the voltage divider operation (see Figure 35).
VI
A
W
B
Because a finite wiper resistance of 60 Ω is present in the zeroscale condition, care should be taken to limit the current flow
between W and B in this state to a maximum pulse current of
20 mA. Otherwise, degradation or possible destruction of the
internal switch contact can occur.
Similar to the mechanical potentiometer, the resistance of the
RDAC between the Wiper W and Terminal A also produces a
complementary resistance, RWA. When these terminals are used,
Terminal B can be opened or shorted to W. Setting the resistance
value for RWA starts at a maximum value of resistance and
decreases as the data loaded in the latch increases in value.
VO
03224-034
A
A
RWA ( D ) =
Figure 35. Potentiometer Mode Configuration
Ignoring the effect of the wiper resistance, the transfer function
is simply
VW (D ) =
D
VA
63
(3)
A more accurate calculation, which includes the wiper
resistance effect, yields
Rev. G | Page 14 of 24
D
RAB + RW
63
VW (D ) =
VA
RAB + 2RW
(4)
AD5273
Potentiometer mode includes op amp feedback resistor
networks and other voltage scaling applications. Terminal A,
Terminal W, and Terminal B can in fact be input or output
terminals, provided that |VAB|, |VWA|, and |VWB| do not exceed
VDD to GND.
ESD PROTECTION
Digital inputs SDA and SCL are protected with a series input
resistor and parallel Zener ESD structures (see Figure 36).
LOGIC
03224-035
340Ω
Figure 36. ESD Protection of Digital Pins
5.5 V after completing the fuse programming process. As a result,
dual voltage supplies and isolation are needed if the system VDD is
outside the required VDD_OTP range. For successful OTP, the fuse
programming supply (either an on-board regulator or rack-mount
power supply) must be rated at 4.75 V to 5.25 V and provide a
100 mA current for 400 ms. Once fuse programming is completed,
the VDD_OTP supply must be removed to allow normal operation
of 2.7 V to 5.5 V; then the device reduces the current consumption
to the μA range.
When operating systems at 2.7 V, use of the bidirectional low
threshold P-Ch MOSFETs is recommended for the supply’s
isolation. As shown in Figure 38, this assumes that the 2.7 V
system voltage is applied first and that the P1 and P2 gates are
pulled to ground, thus turning on P1 first and then P2. As a
result, VDD of the AD5273 approaches 2.7 V. When the AD5273
setting is found, the factory tester applies the VDD_OTP to both
the VDD and the MOSFETs’ gates, thus turning off P1 and P2.
The OTP command should be executed at this time to program
the AD5273 while the 2.7 V source is protected. Once the fuse
programming is complete, the tester withdraws the VDD_OTP and
the AD5273’s setting is fixed permanently.
5V
TERMINAL VOLTAGE OPERATING RANGE
APPLIES FOR OTP ONLY
R1
10kΩ
There are also ESD protection diodes between VDD and the
RDAC terminals. The VDD of AD5273 therefore defines their
voltage boundary conditions (see Figure 37). Supply signals
present on Terminal A, Terminal B, and Terminal W that exceed
VDD are clamped by the internal forward-biased diodes.
2.7V
P1
P2
C1
10µF
VDD
P1 = P2 = FDV302P, NDS0610
A
VDD
AD5273
Figure 38. 5 V OTP Supply Isolated from the 2.7 V Normal Operating Supply
W
AD5273 achieves the OTP function through blowing internal
fuses. Users should always apply the 4.75 V to 5.25 V OTP
voltage requirement at the first fuse programming attempt.
Failure to comply with this requirement can lead to a change in
fuse structures, rendering programming inoperable.
03224-036
B
GND
C2
0.1µF
03224-039
Unlike rheostat mode where the absolute tolerance is high,
potentiometer mode yields an almost ratiometric function of
D/63 with a relatively small error contributed by the RW terms.
Therefore, the tolerance effect is almost cancelled. Although the
step resistor, RS, and CMOS switch resistor, RW, have very different temperature coefficients, the ratiometric adjustment also
reduces the overall temperature coefficient effect to 5 ppm/°C,
except at low value codes where RW dominates.
Figure 37. Maximum Terminal Voltages Set by VDD
POWER-UP/POWER-DOWN SEQUENCES
Because of the ESD protection diodes, it is important to power
VDD first before applying any voltages to Terminal A, Terminal B,
and Terminal W. Otherwise, the diode is forward-biased such that
VDD is powered unintentionally and can affect the rest of the user’s
circuits. The ideal power-up sequence is in the following order:
GND, VDD, digital inputs, and VA/VB/VW. The order of powering
VA, VB, VW, and digital inputs is not important as long as they are
powered after VDD. Similarly, VDD should be powered down last.
POWER SUPPLY CONSIDERATIONS
To minimize the package pin count, both OTP and normal
operating voltage supplies are applied to the same VDD terminal
of the AD5273. The AD5273 employs fuse link technology that
requires 4.75 V to 5.25 V for blowing the internal fuses to achieve
a given setting, but normal VDD can be in the range of 2.7 V to
Care should be taken when SCL and SDA are driven from a low
voltage logic controller. Users must ensure that the logic high
level is between 0.7 × VDD and VDD. Refer to the Level Shift for
Different Voltages Operation section.
Poor PCB layout introduces parasitics that can affect fuse programming. Therefore, it is recommended to add a 10 μF tantalum
capacitor in parallel with a 1 nF ceramic capacitor as close as
possible to the VDD pin. The type and value chosen for both capacitors are important. This combination of capacitor values provides
a fast response and larger supply current handling with minimum
supply drop during transients. As a result, these capacitors increase
the OTP programming success by not inhibiting the proper energy
needed to blow the internal fuses. Additionally, C1 minimizes
transient disturbance and low frequency ripple, while C2 reduces
high frequency noise during normal operation.
Rev. G | Page 15 of 24
AD5273
CONTROLLING THE AD5273
To apply the device programming software in the factory, lay
out the AD5273 SCL and SDA pads on the PCB such that the
programming signals can be communicated to and from the
parallel port (see Figure 40). Figure 41 shows a recommended
AD5273 PCB layout into which pogo pins can be inserted for
factory programming. To prevent damaging the PC parallel
port, 100 Ω resistors should also be put in series to the SCL and
SDA pins. Pull-up resistors on SCL and SDA are also required.
03224-040
Because of the OTP feature, users can program the AD5273 in
the factory before shipping it to end users. Therefore, Analog
Devices offers device programming software that can be implemented in the factory on computers running Windows NT,
Windows 2000, and Windows XP platforms. The software,
which can be downloaded from the AD5273 product page at
www.analog.com, is an executable file that does not require any
programming languages or user programming skills. Figure 39
shows the software interface.
Figure 39. Software Interface
Write
The AD5273 starts at midscale after power-up prior to any OTP
programming. To increment or decrement the resistance, move
the scrollbar on the left. Once the desired setting is found, click
Program Permanent to lock the setting permanently. To write
any specific values, use the bit pattern control in the upper
section and click Run. The format of writing data to the device is
shown in Figure 31. Once the desired setting is found, set the
T bit to 1 and click Run to program the setting permanently.
Read
To read the validation bits and data from the device, click Read.
The user can also set the bit pattern in the upper section and
click Run. The format of reading data from the device is shown
in Figure 32.
Rev. G | Page 16 of 24
13
25
12
24
11
23
10
22
9
21
8
20
7
19
6
18
5
17
4
16
3
15
2
14
1
VDD
R3
100Ω
R4
10kΩ
R5
10kΩ
SCL
SDA
R2 READ
100Ω
R1 WRITE
100Ω
03224-041
SOFTWARE PROGRAMMING
To control the device in both read and write operations, the
program generates the I2C digital signals through the parallel
port LPT1 Pin 2, Pin 3, Pin 15, and Pin 25 for SDA_write, SCL,
SDA_read, and DGND, respectively (see Figure 40).
Figure 40. Parallel Port Connection; Pin 2 = SDA_Write, Pin 3 = SCL,
Pin 15 = SDA_Read, and Pin 25 = DGND
W
VDD
GND
SCL
A
B
AD0
SDA
03224-042
To control the AD5273, users can program the device with
either computer software or with external I2C controllers.
Figure 41. Recommended AD5273 PCB Layout
AD5273
I2C CONTROLLER PROGRAMMING
Write Bit Patterns
0
8
8
0
0
8
SCL
1
0
1
0
1
0
AD0 R/W
X
X
X
X
X
X
X
ACK. BY
AD5273
FRAME 1
SLAVE ADDRESS BYTE
START BY
MASTER
X
X
D5
D4
D3
D2
D1
D0
ACK. BY
AD5273
ACK. BY
AD5273
FRAME 2
INSTRUCTION BYTE
FRAME 1
DATA BYTE
STOP BY
MASTER
03224-043
0
STOP BY
MASTER
03224-044
SDA
Figure 42. Writing to the RDAC Register
0
8
8
0
0
8
SCL
SDA
0
1
0
1
0
1
AD0 R/W
1
X
X
X
X
X
X
START BY
MASTER
X
X
X
ACK. BY
AD5273
D5
D4
D3
D2
D1
D0
ACK. BY
AD5273
FRAME 1
SLAVE ADDRESS BYTE
ACK. BY
AD5273
FRAME 2
INSTRUCTION BYTE
FRAME 1
DATA BYTE
Figure 43. Activating One-Time Programming
Read Bit Pattern
8
0
0
8
SCL
0
1
0
1
1
0
AD0 R/W
E1
ACK. BY
AD5273
START BY
MASTER
FRAME 1
SLAVE ADDRESS BYTE
E0
D5
D4
D3
D2
D1
D0
NO ACK. BY
AD5273
FRAME 2
DATA BYTE FROM SELECTED
RDAC REGISTER
STOP BY
MASTER
03224-059
SDA
Figure 44. Reading Data from the RDAC Register
For users who do not use the software solution, the AD5273 can
be controlled via an I2C-compatible serial bus and is connected
to this bus as a slave device. Referring to Figure 42, Figure 43,
and Figure 44, the 2-wire I2C serial bus protocol operates as
follows:
1.
The master initiates data transfer by establishing a start
condition. A start condition is defined as a high-to-low
transition on the SDA line while SCL is high, as shown in
Figure 42. The byte following the start condition is the
slave address byte, which consists of six MSBs defined as
010110. The next bit is AD0; it is an I2C device address bit.
Depending on the states of the AD0 bits, two AD5273s can
be addressed on the same bus, as shown in Figure 45. The
last LSB is the R/W bit, which determines whether data is
read from or written to the slave device.
2.
A write operation contains one more instruction byte than
the read operation. The instruction byte in the write mode
follows the slave address byte. The MSB of the instruction
byte labeled T is the OTP bit. After acknowledging the
instruction byte, the last byte in the write mode is the data
byte. Data is transmitted over the serial bus in sequences of
nine clock pulses (eight data bits followed by an acknowledge bit). The transitions on the SDA line must occur during
the low period of SCL and remain stable during the high
period of SCL, as shown in Figure 42.
3.
In read mode, the data byte follows immediately after the
acknowledgment of the slave address byte. Data is transmitted over the serial bus in sequences of nine clock pulses
(slight difference from write mode, there are eight data bits
followed by a no acknowledge bit). Similarly, the transitions
on the SDA line must occur during the low period of SCL
and remain stable during the high period of SCL, as shown
in Figure 44.
The slave address corresponding to the transmitted address
responds by pulling the SDA line low during the ninth
clock pulse (this is termed the acknowledge bit). At this
stage, all other devices on the bus remain idle while the
selected device waits for data to be written to or read from
its serial register.
Rev. G | Page 17 of 24
AD5273
When all data bits have been read or written, a stop condition is established by the master. A stop condition is
defined as a low-to-high transition on the SDA line
while SCL is high. In write mode, the master pulls the
SDA line high during the 10th clock pulse to establish a
stop condition, as shown in Figure 42 and Figure 43. In
read mode, the master issues a no acknowledge for the
ninth clock pulse, that is, the SDA line remains high. The
master then brings the SDA line low before the 10th clock
pulse, which goes high to establish a stop condition, as
shown in Figure 44.
CONTROLLING TWO DEVICES ON ONE BUS
Figure 45 shows two AD5273 devices on the same serial bus.
Each has a different slave address because the state of each AD0
pin is different. This allows each device to operate independently.
The master device output bus line drivers are open-drain pulldown in a fully I2C-compatible interface.
A repeated write function gives the user flexibility to
update the RDAC output continuously, except after
permanent programming, when the part is addressed and
receives instructions only once. During the write cycle,
each data byte updates the RDAC output. For example,
after the RDAC has acknowledged its slave address and
instruction bytes, the RDAC output updates after these two
bytes. If another byte is written to the RDAC while it is still
addressed to a specific slave device with the same instruction, this byte updates the output of the selected slave device.
If different instructions are needed, the write mode must
be started again with a new slave address, instruction, and
data bytes. Similarly, a repeated read function of the RDAC
is also allowed.
Rev. G | Page 18 of 24
5V
RP
RP
SDA
MASTER
SCL
SDA SCL
AD0
AD5273
5V
SDA SCL
AD0
AD5273
Figure 45. Two AD5273 Devices on One Bus
03224-045
4.
AD5273
APPLICATIONS INFORMATION
5V
DAC
It is common to buffer the output of the digital potentiometer
as a DAC. The buffer minimizes the load dependence and
delivers higher current to the load, if needed.
2
U3
VOUT
A W
U2
03224-046
U3 2N7002
SIGNAL
100Ω
IL =
(VREF × D )/ 64 | 32 ≤ D ≤ 63
GAIN CONTROL COMPENSATION
As shown in Figure 49, the digital potentiometers are
commonly used in gain controls or sensor transimpedance
amplifier signal conditioning applications.
C2
4.7pF
IL
–V
(5)
RS
RBIAS
LD
IL
Figure 48. Programmable Current Source
R2
B 100kΩ A
03224-047
B
U2
AD8601
CC
RL
–5V
VOUT
VIN
VL
V–
–2.048 + V L
For applications that require high current adjustment, such as a
laser diode driver or tunable laser, consider a booster voltage
source, as shown in Figure 47.
W
102Ω
+5V
OP1177
PROGRAMMABLE VOLTAGE SOURCE WITH
BOOSTED OUTPUT
A
RS
V+
VO
AD8601
Figure 46. Programmable Voltage Reference (DAC)
+V
A
U2
ADR03
U1
W
1µF
4
GND
AD5273
C1
GND
5V
B
U3
AD5273
03224-048
AD5273
3
B
2
6
REF191
U1
VIN
0V TO ...
OUPUT
3
SLEEP
5V
1
U1
VS
R1
47kΩ
W
U1
Figure 47. Programmable Booster Voltage Source
In this circuit, the inverting input of the op amp forces
the VOUT to be equal to the wiper voltage set by the digital
potentiometer. The load current is then delivered by the
supply via the N-Channel FET, N1. N1 power handling must
be adequate to dissipate (VIN − VOUT) × IL power. This circuit
can source a maximum of 100 mA with a 5 V supply. For
precision applications, a voltage reference, such as the
ADR421, ADR03, or ADR370, can be applied at Terminal A
of the digital potentiometer.
PROGRAMMABLE CURRENT SOURCE
A programmable current source can be implemented with the
circuit shown in Figure 48. The load current is the voltage across
Terminal B to Terminal W of the AD5273 divided by RS. At zero
scale, Terminal A of the AD5273 is −2.048 V, which makes the
wiper voltage clamped at ground potential. Depending on the
load, Equation 5 is therefore valid only at certain codes. For
example, when the compliance voltage, VL, equals half of VREF,
the current can be programmed from midscale to full scale of
the AD5273.
VO
VI
03224-049
C1
Figure 49. Typical Noninverting Gain Amplifier
In both applications, one of the digital potentiometer terminals
is connected to the op amp inverting node with finite terminal
capacitance, C1. It introduces a zero for the 1 βo term with
20 dB/dec, whereas a typical op amp GBP has −20 dB/dec
characteristics. A large R2 and finite C1 can cause this zero’s
frequency to fall well below the crossover frequency. Therefore,
the rate of closure becomes 40 dB/dec and the system has a 0°
phase margin at the crossover frequency. The output may ring,
or in the worst case, oscillate when the input is a step function.
Similarly, it is also likely to ring when switching between two
gain values because this is equivalent to a step change at the
input. To reduce the effect of C1, users should also configure
Terminal B or Terminal A rather than Terminal W at the
inverting node.
Rev. G | Page 19 of 24
AD5273
PROGRAMMABLE LOW-PASS FILTER
VO
ωO 2
=
ω
VI
S 2 + O S + ωO 2
Q
Q=
VDD2 = 5V
VDD1 = 2.5V
Rp
(6)
1
R1R2C1C2
(7)
1
1
+
R1C1 R2C2
(8)
SDA1
B
W
C
+2.5V
C
AD8601
B
W C2
SCL2
M2
2.7V–5.5V
2.5V
CONTROLLER
AD5273
Figure 51. Level Shift for Different Voltages Operation
RDAC CIRCUIT SIMULATION MODEL
The internal parasitic capacitances and the external capacitive
loads dominate the ac characteristics of the digital potentiometers. Configured as a potentiometer divider, the −3 dB
bandwidth of the AD5273 (1 kΩ resistor) measures 6 MHz at
half scale. Figure 17 to Figure 20 provide the large signal BODE
plot characteristics of the four available resistor versions: 1 kΩ,
10 kΩ, 50 kΩ, and 100 kΩ. Figure 52 shows a parasitic simulation model. The code following Figure 52 provides a macro
model net list for the 1 kΩ device.
A
B
1kΩ
CW
CA
25pF
55pF
W
.PARAM D = 63, RDAC = 1E3
V+
V–
ADJUSTED TO
SAME SETTINGS
SDA2
D
S
M1
Macro Model Net List for RDAC
R2
A
G
D
CB
25pF
Figure 52. Circuit Simulation Model for RDAC = 1 kΩ
U1
–2.5V
Figure 50. Sallen Key Low-Pass Filter
VO
03224-050
VI
Rp
G
C1
R1
Rp
S
Users can first select some convenient values for the capacitors.
To achieve maximally flat bandwidth where Q = 0.707, let C1 be
twice the size of C2 and let R1 = R2. As a result, R1 and R2 can
be adjusted to the same setting to achieve the desired bandwidth.
A
Rp
SCL1
In ADC applications, it is common to include an antialiasing
filter to band-limit the sampling signal. To minimize various
system redesigns, users can use two 1 kΩ AD5273s to construct
a generic second-order Sallen-Key low-pass filter. Because the
AD5273 is a single-supply device, the input must be dc offset
when an ac signal is applied to avoid clipping at ground. This is
illustrated in Figure 50. The design equations are
ωO =
If the SCL and SDA signals come from a low voltage logic
controller and are below the minimum VIH level (0.7 × VDD),
level-shift the signals for successful read/write communication
between the AD5273 and the controller. Figure 51 shows one of
the implementations. For example, when SDA1 is 2.5 V, M1
turns off, and SDA2 becomes 5 V. When SDA1 is 0 V, M1 turns
on, and SDA2 approaches 0 V. As a result, proper level-shifting
is established. M1 and M2 should be low threshold N-Channel
power MOSFETs, such as FDV301N.
03224-051
There is also a Terminal W capacitance connected to the output
(not shown); its effect on stability is less significant; therefore,
compensation is not necessary unless the op amp is driving a
large capacitive load.
LEVEL SHIFT FOR DIFFERENT VOLTAGES
OPERATION
03224-055
Depending on the op amp GBP, reducing the feedback resistor
may extend the zero’s frequency far enough to overcome the
problem. A better approach is to include a compensation
capacitor, C2, to cancel the effect caused by C1. Optimum
compensation occurs when R1 × C1 = R2 × C2, but this is not
an option because of the variation of R2. As a result, users can
use the relationship described and scale C2 as if R2 were at its
maximum value. However, doing so may overcompensate by
slowing down the settling time when R2 is set to low values. To
avoid this problem, C2 should be found empirically for a given
application. In general, setting C2 in the range of a few picofarads
to no more than a few tenths of a picofarad is usually adequate
for compensation.
*
.SUBCKT DPOT (A,W,B)
*
CA A 0 25E-12
RWA A W {(1-D/63)*RDAC+60}
CW W 0 55E-12
RWB W B {D/63*RDAC+60}
CB B 0 25E-12
*
.ENDS DPOT
Rev. G | Page 20 of 24
AD5273
EVALUATION BOARD
JP5
VCC
JP3
V+
C4
0.1µF
CP3
VREF
C5
0.1µF
ADR03
–IN1
–IN1
CP1
JP1
A
2
JP8
JP7
W VIN
VDD
JP2
C1
10mF
J1
8
7
6
5
4
3
2
1
R1
10kΩ
U1
1
A
2 W
B
V
3 DD
GND AD0
4
SCL SDA
R2
10kΩ
C2
0.1µF
SCL
8
7
6
5
U2
1
A
2 W
B
V
3 DD
GND AD0
4
SCL SDA
C3
0.1µF
AD5170
8
7
6
5
CP4
CP2
8
OUT1
1
3
4 U3A
B
+IN1
C7
10µF
CP6
V–
CP5
AGND
OUT1
CP7
JP4
C8
0.1µF
C9
10µF
AD5171/AD5273
SDA
JP6
–IN2
+IN2
6
7
5
OUT2
U3B
VEE
03224-056
VDD
C6
0.1µF
U4
5
1
TEMP TRIM
2
GND
3 V
4
VOUT
IN
VDD
Figure 53. Evaluation Board Schematic
CP2
VDD
2
JP3
4
U3A
1
V+
V–
JP1
A
W
VO
A
U2
3
11
B
JP7
W
JP4
JP2
OUT1
AD822
03224-058
B
03224-057
VREF
VREF
Figure 55. Evaluation Board
Figure 54. One Possible Configuration—
Programmable Voltage Reference
Rev. G | Page 21 of 24
AD5273
OUTLINE DIMENSIONS
2.90 BSC
8
7
6
5
1
2
3
4
1.60 BSC
2.80 BSC
PIN 1
INDICATOR
0.65 BSC
1.95
BSC
1.30
1.15
0.90
1.45 MAX
0.15 MAX
0.38
0.22
0.22
0.08
SEATING
PLANE
8°
4°
0°
0.60
0.45
0.30
COMPLIANT TO JEDEC STANDARDS MO-178-BA
Figure 56. 8-Lead Small Outline Transistor Package [SOT-23]
(RJ-8)
Dimensions shown in millimeters
ORDERING GUIDE
Model
AD5273BRJ1-R2
AD5273BRJ1-REEL7
AD5273BRJZ1-REEL7 1
AD5273BRJ10-R2
AD5273BRJ10-REEL7
AD5273BRJZ10-REEL71
AD5273BRJ50-R2
AD5273BRJ50-REEL7
AD5273BRJZ50-REEL71
AD5273BRJ100-R2
AD5273BRJ100-REEL7
AD5273BRJZ100-REEL71
AD5273EVAL 2
1
2
RAB (kΩ)
1
1
1
10
10
10
50
50
50
100
100
100
Temperature Range
−40°C to +105°C
−40°C to +105°C
−40°C to +105°C
−40°C to +105°C
−40°C to +105°C
−40°C to +105°C
−40°C to +105°C
−40°C to +105°C
−40°C to +105°C
−40°C to +105°C
−40°C to +105°C
−40°C to +105°C
Package Option
RJ-8
RJ-8
RJ-8
RJ-8
RJ-8
RJ-8
RJ-8
RJ-8
RJ-8
RJ-8
RJ-8
RJ-8
Package Description
8-Lead SOT-23
8-Lead SOT-23
8-Lead SOT-23
8-Lead SOT-23
8-Lead SOT-23
8-Lead SOT-23
8-Lead SOT-23
8-Lead SOT-23
8-Lead SOT-23
8-Lead SOT-23
8-Lead SOT-23
8-Lead SOT-23
Evaluation Board
Z = RoHS Compliant Part.
Users should order samples because the evaluation kit comes with a socket, but does not include the parts.
Rev. G | Page 22 of 24
Ordering Quantity
250
3,000
3,000
250
3,000
3,000
250
3,000
3,000
250
3,000
3,000
Branding
DYA
DYA
DYE
DYB
DYB
DYF
DYC
DYC
DYG
DYD
DYD
DYH
AD5273
NOTES
Rev. G | Page 23 of 24
AD5273
NOTES
Purchase of licensed I2C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I2C Patent
Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips.
©2002–2008 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D03224-0-6/08(G)
Rev. G | Page 24 of 24
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