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PDF ADN2850 Data sheet ( Hoja de datos )
| Número de pieza | ADN2850 | |
| Descripción | Nonvolatile Memory/ Dual 1024 Position Programmable Resistors | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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PRELIMINARY TECHNICAL DATA
a
Nonvolatile Memory, Dual 1024
Position Programmable Resistors
Preliminary Technical Data
ADN2850
FEATURES
Dual, 1024 Position Resolution
25K, 250K Ohm Full Scale Resistance
Low Temperature Coefficient -- 35ppm/°C
Nonvolatile Memory1 Preset Maintains Wiper Settings
Wiper Settings Read Back
Linear Increment/Decrement
Log taper Increment/Decrement
SPI Compatible Serial Interface
+3V to +5V Single Supply or ±2.5V Dual Supply
26 bytes User Nonvolatile Memory for Constant Storage with
Current Monitoring Configurable Function
APPLICATIONS
SONET, SDH, ATM, Gigabit Ethernet, DWDM Laser Diode
Driver Optical Supervisory Systems
GENERAL DESCRIPTION
The ADN2850 provides dual channel, digitally controlled
programmable resistors2 with resolution of 1024 positions. These
devices perform the same electronic adjustment function as a
mechanical rheostat. The ADN2850’s versatile programming via a
standard serial interface allows sixteen mode of operations and
adjustment including scratch pad programming, memory storing
and retrieving, increment/decrement, log taper adjustment, wiper
setting readback, and extra user defined EEMEM.
In the scratch pad programming mode, a specific setting can be
programmed directly to the RDAC2 register, which sets the
resistance between terminals W-and-B. The RDAC register can
also be loaded with a value previously stored in the EEMEM1
register. The value in the EEMEM can be changed or protected.
When changes are made to the RDAC register, the value of the new
setting can be saved into the EEMEM. Thereafter, such value will
be transferred automatically to the RDAC register during system
power ON. It is enabled by the internal preset strobe. EEMEM can
also be retrieved through direct programming and external preset
pin control.
Other key mode of operations include linear step increment and
decrement commands such that the setting in the RDAC register
can be moved UP or DOWN, one step at a time. For logarithmic
changes in wiper setting, a left/right bit shift command adjusts the
level in ±6dB steps.
The ADN2850 is available in the 5mm x 5mm LFCSP-16 Lead
Frame Chip Scale and thin TSSOP-16 packages. All parts are
guaranteed to operate over the extended industrial temperature
range of -40°C to +85°C.
FUNCTIONAL BLOCK DIAGRAM
CS
CLK
SDI
SDO
ADDRE S S
DECO DE
SERIAL
INPUT
REG IS TE R
RD AC1
REGIST ER
EEMEM1
PR
PWR ON
PRESET
WP
R DY
EEMEM
CON TROL
VDD
VSS
GND
RD AC2
REGIST ER
EEMEM2
26 BYTES
USER EEMEM
RD AC1
W1
B1
RD AC1
W2
B2
I1
C URRENT
M ON IT OR
I2
V1
V2
100%
75%
50%
25%
0%
0
256 512 768
D - Co d e in De cim al
Figure 1. RWB(D) vs Decimal Code
1023
Notes:
1. The term nonvolatile memory and EEMEM are used interchangebly
2. The term programmable resistor and RDAC are used interchangebly
REV PrH, 13, AUG 2001
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: 617/329-4700
Fax:617/326-8703
1 page  
PRELIMINARY TECHNICAL DATA
Nonvolatile Memory Programmable Resistors
ADN2850
Absolute Maximum Rating1 (TA = +25°C, unless
otherwise noted)
VDD to GND............................................................-0.3V, +7V
VSS to GND ............................................................+0.3V, -7V
VDD to VSS .........................................................................+7V
VB, VW to GND..................................... VSS-0.3V, VDD+0.3V
BX – WX ....................................................................... ±20mA
Intermittent2 .................................................. ±20mA
Continuous................................................... ±1.3mA
Digital Inputs & Output Voltage to GND.....-0.3V, VDD+0.3V
Operating Temperature Range3........................ -40°C to +85°C
Maximum Junction Temperature (TJ MAX)...................+150°C
Storage Temperature...................................... -65°C to +150°C
Lead Temperature, Soldering4
Vapor Phase (60 sec) .......................................+215 °C
Infrared (15 sec)...............................................+220 °C
Thermal Resistance Junction-to-Ambient θJA,
LFCSP-16 ........................................................ 35°C/W
TSSOP-16 ..................................................... 150°C/W
Thermal Resistance Junction-to-Case θJC,
LFCSP-16............................................................. TBD
TSSOP-16 ....................................................... 28°C/W
Package Power Dissipation = (TJMAX - TA) / θJA
NOTES
1. Stresses above those listed under Absolute Maximum Ratings may
cause permanent damage to the device. This is a stress rating; 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. Maximum terminal current is bounded by the maximum current
handling of the switches, maximum power dissipation of the package,
and maximum applied voltage across any two of the B, and W terminals
at a given resistance.
3. Includes programming of Nonvolatile memory
4. Applicable to TSSOP-16 only. For LFCSP-16, please consult factory
for detail
Ordering Guide
Model
RWB
(k Ohm)
RDNL
(LSB)
RINL
(LSB)
Temp
Range
Package
Description
Package
Option
Top Mark*
ADN2850ACP25
25 ±2
±4
-40/+85°C LFCSP-16
CP-16
ACP25
ADN2850ACP25-RL7 25 ±2
±4
-40/+85°C LFCSP-16
CP-16
ACP25
1500 Pieces
7” Reel
ADN2850ACP250
250 ±2
±4
-40/+85°C LFCSP-16
CP-16
ACP250
ADN2850ACP250-RL7
250
±2
±4
-40/+85°C LFCSP-16
CP-16
ACP250
1500 Pieces
7” Reel
ADN2850ARU25
25 ±2
±4
-40/+85°C TSSOP-16
RU-16
ARU25
ADN2850ARU25-REEL7
25
±2
±4
-40/+85°C TSSOP-16
RU-16
ARU25
1000 Pieces
7” Reel
* Line 1 contains ADI logo symbol and date code YYWW, line 2 contains product number ADN2850, line 3 branding containing differentiating detail by part type, line
4 contains lot number.
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
ADN2850 features 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.
REV PrH, 13, AUG 2001
5
5 Page 
PRELIMINARY TECHNICAL DATA
Nonvolatile Memory Programmable Resistors
ADN2850
RDAC STRUCTURE
The RDAC contains a string of equal resistor segments, with an
array of analog switches, that act as the wiper connection. The
number of positions is the resolution of the device. The
ADN2850 has 1024 connection points allowing it to provide
better than 0.1% set-ability resolution. Figure 8 shows an
equivalent structure of the connections between the two
terminals that make up one channel of the RDAC. The SWB will
always be ON, while one of the switches SW(0) to SW(2N-1)
will be ON one at a time depending on the resistance position
decoded from the Data Bits. Since the switch is not ideal, there
is a 50Ω wiper resistance, RW. Wiper resistance is a function of
supply voltage and temperature. The lower the supply voltage,
the higher the wiper resistance. Similarly, the higher the
temperature, the higher the wiper resistance. RW is the sum of
the resistance of SW(D) + SWB from Wiper-to-B terminals
Users should be aware of the contribution of the wiper
resistance when accurate prediction of the output resistance is
needed.
The 10-bit data word in the RDAC latch is decoded to select one
of the 1024 possible settings. The following discussion
describes the calculation of resistance RWB(D) at different codes
of a 25KΩ part. The wiper first connection starts at the B
terminal for data 000H. RWB is 50Ω because of the wiper
resistance and it is independent to the full-scale resistance. The
second connection is the first tap point where RWB(1) becomes
24.4Ω+50=74.4Ω for data 01H. The third connection is the next
tap point representing RWB(2)=48.8+50=98.8Ω for data 02H and
so on. Each LSB data value increase moves the wiper up the
resistor ladder until the last tap point is reached at
RWB(1023)=25026Ω. See Figure 9 for a simplified diagram of
the equivalent RDAC circuit.
25
RWB_FS = 25KΩ
20
15
RDAC
WIPER
REGISTER
&
DECODER
RS
RS
SW(2 N-1)
W
SW(2 N-2)
SW(1 )
RS
RS=RWB_FS/2N
SW(0 )
DIGITAL
CIRCUITRY
OMITTED FOR
CLARITY
SWB
B
Figure 9. Equivalent RDAC structure
Table 5. Nominal individual segment resistor values
Device
Resolution
25 KΩ
Version
250 KΩ
Version
10-Bit
24.4 Ω
244 Ω
10
5
0
0 256 512 768 1023
D - Co d e in De cim al
Figure 10. RWB(D) vs Code
The general equation, which determines the programmed output
resistance between Wx and Bx, is:
RWB (D) =
D
2N
⋅ RWB _ FS
+ RW
(1)
Where D is the decimal equivalent of the data contained in the
RDAC register, 2N is the number of steps, RWB_FS is the full
scale resistance between terminals W-and-B, and RW is the wiper
resistance.
For example, the following output resistance values will be set
for the following RDAC latch codes (applies to RWB_FS=25KΩ
programmable resistors):
CALCULATIING THE PROGRAMMABLE
RESISTANCE
The nominal full scale resistance of the RDAC between
terminals W-and-B, R ,WB_FS are available with 25KΩ and 250KΩ
with 1024 positions (10-bit resolution). The final digits of the
part number determine the nominal resistance value, e.g., 25KΩ
= 25; 250KΩ = 250.
D RWB(D) Output State
(DEC) (Ω)
1023
512
1
0
25026
12550
74.4
50
Full-Scale
Mid-Scale
1 LSB
Zero-Scale (Wiper contact resistance)
REV PrH, 13, AUG 2001
11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet ADN2850.PDF ] | |
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