Data Sheet
FEATURES
Dual-channel, 1024-position resolution
25 kΩ, 250 kΩ nominal resistance
Maximum ±8% nominal resistor tolerance error
Low temperature coefficient: 35 ppm/°C
2.7 V to 5 V single supply or ±2.5 V dual supply
Current monitoring configurable function
SPI-compatible serial interface
Nonvolatile memory stores wiper settings
Power-on refreshed with EEMEM settings
Permanent memory write protection
Resistance tolerance stored in EEMEM
26 bytes extra nonvolatile memory for user-defined
information
1M programming cycles
100-year typical data retention
Nonvolatile Memory, Dual
1024-Position Digital Resistor
ADN2850
FUNCTIONAL BLOCK DIAGRAM
CS
CLK
SDI
SDO
PR
WP
RDY
V
DD
V
SS
GND
*R
WB
FULL SCALE TOLERANCE.
RTOL*
26 BYTES
USER EEMEM
POWER-ON
RESET
EEMEM
CONTROL
EEMEM2
RDAC2
I
1
CURRENT
MONITOR
I
2
SERIAL
INTERFACE
EEMEM1
ADDR
DECODE
ADN2850
RDAC1
REGISTER
W1
RDAC1
B1
RDAC1
REGISTER
W2
B2
V
1
APPLICATIONS
SONET, SDH, ATM, Gigabit Ethernet, DWDM laser diode
driver, optical supervisory systems
Mechanical rheostat replacement
Instrumentation gain adjustment
Programmable filters, delays, time constants
Sensor calibration
Figure 1.
GENERAL DESCRIPTION
The
ADN2850
is a dual-channel, nonvolatile memory, digitally
controlled resistor with 1024-step resolution, offering guaranteed
maximum low resistor tolerance error of ±8%. The device performs
the same electronic adjustment function as a mechanical rheostat
with enhanced resolution, solid state reliability, and superior low
temperature coefficient performance. The versatile programming
of the
ADN2850
via an SPI-compatible serial interface allows 16
modes of operation and adjustment including scratchpad
programming, memory storing and restoring, increment/
decrement, ±6 dB/step log taper adjustment, wiper setting
readback, and extra EEMEM for user-defined information such as
memory data for other components, look-up table, or system
identification information.
In the scratchpad programming mode, a specific setting can
be programmed directly to the RDAC register, which sets the
resistance between Terminal W and Terminal B. This setting can
be stored into the EEMEM and is restored automatically to the
RDAC register during system power-on.
The EEMEM content can be restored dynamically or through
external PR strobing, and a WP function protects EEMEM
contents. To simplify the programming, the independent or
simultaneous linear-step increment or decrement commands
can be used to move the RDAC wiper up or down, one step at a
time. For logarithmic ±6 dB changes in the wiper setting, the
left or right bit shift command can be used to double or halve the
RDAC wiper setting.
The
ADN2850
patterned resistance tolerance is stored in the
EEMEM. The actual full scale resistance can, therefore, be
known by the host processor in readback mode. The host can
execute the appropriate resistance step through a software
routine that simplifies open-loop applications as well as
precision calibration and tolerance matching applications.
The
ADN2850
is available in the 5 mm × 5 mm 16-lead frame
chip scale LFCSP and thin, 16-lead TSSOP. The device is
guaranteed to operate over the extended industrial temperature
range of −40°C to +85°C.
In this data sheet, the terms nonvolatile memory and EEMEM
are used interchangeably and the terms digital resistor and
RDAC are used interchangeably
Rev. F
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02660-001
V
2
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Application Notes
• AN-628: ADN2850 Evaluation Kit User Manual
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Data Sheet
• ADN2850:Nonvolatile Memory, Dual 1024-Position
Digital Resistor Data Sheet
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ADN2850
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Specifications..................................................................................... 4
Electrical Characteristics—25 kΩ, 250 kΩ Versions ............... 4
Interface Timing and EEMEM Reliability Characteristics—25
kΩ, 250 kΩ Versions .................................................................... 6
Absolute Maximum Ratings............................................................ 8
ESD Caution .................................................................................. 8
Pin Configurations and Function Descriptions ........................... 9
Typical Performance Characteristics ........................................... 11
Test Circuits ................................................................................. 14
Theory of Operation ...................................................................... 15
Scratchpad and EEMEM Programming .................................. 15
Basic Operation .......................................................................... 15
EEMEM Protection .................................................................... 16
Digital Input and Output Configuration................................. 16
Serial Data Interface ................................................................... 16
Data Sheet
Daisy-Chain Operation ............................................................. 17
Terminal Voltage Operating Range ......................................... 17
Advanced Control Modes ......................................................... 19
RDAC Structure.......................................................................... 20
Programming the Variable Resistor ......................................... 21
Programming Examples ............................................................ 21
EVAL-ADN2850SDZ Evaluation Kit....................................... 22
Applications Information .............................................................. 23
Gain Control Compensation .................................................... 23
Programmable Low-Pass Filter ................................................ 23
Programmable Oscillator .......................................................... 23
Optical Transmitter Calibration with ADN2841 ................... 24
Incoming Optical Power Monitoring ...................................... 24
Resistance Scaling ...................................................................... 25
Resistance Tolerance, Drift, and Temperature Coefficient
Mismatch Considerations ......................................................... 26
RDAC Circuit Simulation Model ............................................. 26
Outline Dimensions ....................................................................... 27
Ordering Guide .......................................................................... 27
REVISION HISTORY
4/16—Rev. E to Rev. F
Changed CP-16-6 to CP-16-31 .................................... Throughout
Changes to General Description Section ...................................... 1
Changes to Figure 4 and Table 4 ..................................................... 9
Changes to Figure 5 and Table 5 ................................................... 10
Updated Outline Dimensions ....................................................... 27
Changes to Ordering Guide .......................................................... 27
6/12—Rev. D to Rev. E
Changes to Table 1 Conditions ....................................................... 4
Removed Positive Supply Current RDY and/or SDO Floating
Parameters and Negative Supply Current RDY and/or SDO
Floating Parameters, Table 1 ........................................................... 4
Updated Outline Dimensions ....................................................... 25
Added Endnote 2 to Ordering Guide .......................................... 25
4/11—Rev. C to Rev. D
Changes to Figure 10 ...................................................................... 10
4/11—Rev. B to Rev. C
Updated Format .................................................................. Universal
Changes to EEMEM Performance ................................... Universal
Changes to Features Section............................................................ 1
Changes to Applications Section .................................................... 1
Changes to General Description Section ...................................... 1
Changes to Figure 1 ...........................................................................1
Changes to Specifications Section ...................................................3
Changes to Table 2.............................................................................5
Changes to Absolute Maximum Ratings Section ..........................7
Changes to Pin Configuration and Function Descriptions
Section.................................................................................................8
Changes to Typical Performance Characteristics Section ........ 10
Added Figure 15, Figure 16, and Figure 17 ................................. 11
Changes to Figure 21...................................................................... 12
Changes to Theory of Operation Section.................................... 13
Changes to Figure 25...................................................................... 14
Changes to Programming Variable Resister Section ................. 19
Changes to Table 13 ....................................................................... 19
Changes to EVAL-ADN2850EBZ Evaluation Kit Section ........ 20
Added Gain Control Compensation Section.............................. 21
Added Programmable Low-Pass Filter Section .......................... 21
Added Programmable Oscillator Section.................................... 21
Added Resistance Tolerance, Drift, and Temperature
Coefficient Mismatch Considerations Section ........................... 24
Changes to Outline Dimensions Section .................................... 25
Changes to Ordering Guide .......................................................... 25
Rev. F | Page 2 of 30
Data Sheet
9/02—Rev. A to Rev. B
Changes to General Description ..................................................... 1
Changes to Electrical Characteristics ............................................. 2
Changes to Calculating Actual Full-Scale Resistance Section .... 9
Changes to Table VI .......................................................................... 9
Updated Outline Dimensions ........................................................18
ADN2850
Rev. F | Page 3 of 30
ADN2850
SPECIFICATIONS
ELECTRICAL CHARACTERISTICS—25 kΩ, 250 kΩ VERSIONS
Data Sheet
V
DD
= 2.7 V to 5.5 V, V
SS
= 0 V; V
DD
= 2.5 V, V
SS
= −2.5 V, V
A
= V
DD
, V
B
= V
SS
, −40°C < T
A
< +85°C, unless otherwise noted. These
specifications apply to versions with a date code 1209 or later.
Table 1.
Parameter
DC CHARACTERISTICS—RHEOSTAT
MODE (All RDACs)
Resolution
Resistor Differential Nonlinearity
2
Resistor Integral Nonlinearity
2
Nominal Resistor Tolerance
Resistance Temperature Coefficient
3
Wiper Resistance
Symbol
Test Conditions/Comments
Min
Typ
1
Max
Unit
N
R-DNL
R-INL
∆R
WB
/R
WB
(∆R
WB
/R
WB
)/
∆T × 10
6
R
W
R
WB
R
WB
Code = full scale
Code = full scale
Code = half scale
V
DD
= 5 V
V
DD
= 3 V
Code = full scale
−1
−2
−8
35
10
+1
+2
+8
LSB
LSB
%
ppm/°C
Nominal Resistance Match
3
RESISTOR TERMINALS
Terminal Voltage Range
3
Capacitance Bx
3
Capacitance Wx
3
Common-Mode Leakage Current
3, 4
DIGITAL INPUTS AND OUTPUTS
Input Logic
3
High
R
WB1
/R
WB2
V
B
, V
W
C
B
C
W
I
CM
30
50
±0.1
V
SS
60
Ω
Ω
%
V
pF
pF
V
DD
11
80
0.01
±1
f = 1 MHz, measured to GND,
code = half-scale
f = 1 MHz, measured to GND,
code = half-scale
V
W
= V
DD
/2
µA
V
IH
Low
V
IL
Output Logic High (SDO, RDY)
Output Logic Low
Input Current
Input Capacitance
3
POWER SUPPLIES
Single-Supply Power Range
Dual-Supply Power Range
Positive Supply Current
Negative Supply Current
EEMEM Store Mode Current
V
OH
V
OL
I
IL
C
IL
V
DD
V
DD
/V
SS
I
DD
I
SS
I
DD
(store)
I
SS
(store)
I
DD
(restore)
I
SS
(restore)
P
DISS
P
SS
V
DD
= 5 V
V
DD
= 2.7 V
V
DD
= +2.5 V, V
SS
= −2.5 V
V
DD
= 5 V
V
DD
= 2.7 V
V
DD
= +2.5 V, V
SS
= −2.5 V
R
PULL-UP
= 2.2 kΩ to 5 V (see Figure 25)
I
OL
= 1.6 mA, V
LOGIC
= 5 V (see Figure 25)
V
IN
= 0 V or V
DD
2.4
2.1
2.0
0.8
0.6
0.5
4.9
0.4
±1
5
V
V
V
V
V
V
V
V
µA
pF
V
V
µA
µA
mA
mA
µA
µA
µW
%/%
V
SS
= 0 V
V
IH
= V
DD
or V
IL
= GND
V
DD
= +2.5 V, V
SS
= −2.5 V
V
IH
= V
DD
or V
IL
= GND
V
IH
= V
DD
or V
IL
= GND,
V
SS
= GND, I
SS
≈ 0
V
DD
= +2.5 V, V
SS
= −2.5 V
V
IH
= V
DD
or V
IL
= GND,
V
SS
= GND, I
SS
≈ 0
V
DD
= +2.5 V, V
SS
= −2.5 V
V
IH
= V
DD
or V
IL
= GND
∆V
DD
= 5 V ± 10%
2.7
±2.25
2
−4
−2
2
−2
320
−320
10
0.006
5.5
±2.75
5
EEMEM Restore Mode Current
5
Power Dissipation
Power Supply Sensitivity
3
6
30
0.01
Rev. F | Page 4 of 30
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