DS1847-050 Просмотр технического описания (PDF) - Dallas Semiconductor -> Maxim Integrated
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DS1847-050 Datasheet PDF : 17 Pages
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DS1847
PROGRAMMING THE LOOK-UP TABLE (LUT)
The following equation can be used to determine which resistor position setting, 00h – FFh, should be
written in the LUT to achieve a given resistance at a specific temperature.
[ [ ] ] pos(a,
R, C )
=
R - u · 1 + v · (C - 25) + w · (C - 25)2
(x) · 1 + y · (C - 25) + z · (C - 25)2
-a
DS1847-050
a = 3.78964 for the 50kW resistor
a = 19.74866 for the 10kW resistor
DS1847-010
a = 8.394533 for both 10kW resistors
R = resistance desired at the output terminal
C = temperature in degrees Celsius
u, v, w, x, y, and z are calibration constants programmed into each of the corresponding look-up tables.
Their addresses and LSB values are given in Table 1. Resistor 1 variables are found in Look-Up Table 1
of the EEPROM, and Resistor 2 variables are found in Look-Up Table 2. After these values are read, they
should be overwritten with the appropriate temperature-specific resistance settings.
LOOK-UP VARIABLE ADDRESSES Table 1
Address in Variable LSB
LUT (HEX)
28 – 29
u
2-8
2A – 2B
v
10-6
2C – 2D
w
10-9
2E – 2F
x
2-8
30 – 31
y
10-7
32 – 33
z
10-10
When shipped from the factory, all other memory locations in the LUTs are programmed to FFh (except
bytes 00h-07h of Table 1 and 2 which may be factory programmed to values other than FFh).
Note: Memory locations 44h – 47h, which cover the temperature range (+96ºC to +102ºC), are outside
of the specified operating temperature range (-40ºC to +95ºC). However, the values stored in these
locations will act as valid resistance settings if the temperature exceeds +95ºC. Therefore, Dallas
Semiconductor recommends that the user programs a resistance value into all LUT locations. Failure to
do so will result in the part being set to the default value.
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