Nonvolatile Memory, Dual
1024-Position Digital Resistor
Data Sheet
ADN2850
FEATURES
FUNCTIONAL BLOCK DIAGRAM
Dual-channel, 1024-position resolution
25 kΩ, 250 kΩ nominal resistance
ADN2850
ADDR
DECODE
RDAC1
REGISTER
CS
CLK
SDI
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
W1
B1
SERIAL
INTERFACE
RDAC1
SDO
EEMEM1
POWER-ON
RESET
PR
RDAC1
REGISTER
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
WP
EEMEM
CONTROL
W2
B2
RDY
RDAC2
EEMEM2
V
DD
I
V
1
1
26 BYTES
USER EEMEM
CURRENT
MONITOR
I
V
SS
RTOL*
V
2
GND
2
1M programming cycles
100-year typical data retention
*R
FULL SCALE TOLERANCE.
WB
APPLICATIONS
Figure 1.
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
In the scratchpad programming mode, a specific setting can
be programmed directly to the RDAC2 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
GENERAL DESCRIPTION
PR
WP
external
strobing, and a
function protects EEMEM
The ADN2850 is a dual-channel, nonvolatile memory1, digitally
controlled resistors2 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 EEMEM1
for user-defined information such as memory data for other
components, look-up table, or system identification
information.
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 package. The part is
guaranteed to operate over the extended industrial temperature
range of −40°C to +85°C.
1 The terms nonvolatile memory and EEMEM are used interchangeably.
2 The terms digital resistor and RDAC are used interchangeably.
Rev. E
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