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參數(shù)資料
| 型號： | DS1856E-025R |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Dual, Temperature-Controlled Resistors with Internally Calibrated Monitors and Password Protection |
| 中文描述： | 雙路，溫度與內(nèi)部校準(zhǔn)監(jiān)視器和控制電阻器，密碼保護 |
| 文件頁數(shù)： | 25/31頁 |
| 文件大?。?/td> | 484K |
| 代理商： | DS1856E-025R |
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D
Dual, Temperature-Controlled Resistors with Inter-
nally Calibrated Monitors and Password Protection
____________________________________________________________________
25
Programming the Look-up Table (LUT)
The following equation can be used to determine which
resistor position setting, 00h to FFh, should be written in
the LUT to achieve a given resistance at a specific tem-
perature.
R = the resistance desired at the output terminal
C = temperature in degrees Celsius
u, v, w, x1, x0, y, z, and
α
are calculated values found in
the corresponding look-up tables. The variable x from the
equation above is separated into x1(the MSB of x) and x0
(the LSB of x). Their addresses and LSB values are given
below. The variable y is assigned a value. All other vari-
ables are unsigned. Resistor 0 variables are found in
Table 04, and Resistor 1 variables are found in Table 05.
When shipped from the factory, all other memory loca-
tions in the LUTs are programmed to FFh.
Table 8. Calibration Constants
Internal Calibration
The DS1856 has two methods for scaling an analog
input to a digital result. The two methods are gain and
offset. Each of the inputs (V
CC
, MON1, MON2, and
MON3) has a unique register for the gain and the offset
found in Table 03h, 92h to 99h, and A2h to A9h.
To scale the gain and offset of the converter for a spe-
cific input, you must first know the relationship between
the analog input and the expected digital result. The
input that would produce a digital result of all zeros is
the null value (normally this input is GND). The input
that would produce a digital result of all ones is the full-
scale (FS) value. The FS value is also found by multiply-
ing an all-ones digital answer by the weighted LSB
(e.g., since the digital reading is a 16-bit register, let us
assume that the LSB of the lowest weighted bit is
50μV, then the FS value is 65,535 x 50μV = 3.27675V).
A binary search is used to scale the gain of the con-
verter. This requires forcing two known voltages to the
input pin. It is preferred that one of the forced voltages
is the null input and the other is 90% of FS. Since the
LSB of the least significant bit in the digital reading reg-
ister is known, the expected digital results are also
known for both inputs (null/LSB = CNT1 and 90%FS/
LSB = CNT2).
The user might not directly force a voltage on the input.
Instead they have a circuit that transforms light, fre-
quency, power, or current to a voltage that is the input
to the DS1856. In this situation, the user does not need
to know the relationship of voltage to expected digital
result but instead knows the relationship of light, fre-
quency, power, or current to the expected digital result.
An explanation of the binary search used to scale the
gain is best served with the following example pseudo-
code:
/* Assume that the null input is 0.5V. */
/* In addition, the requirement for LSB is 50μV. */
FS = 65535 x 50E-6;
CNT1 = 0.5 / 50E-6;
CNT2 = 0.90 x FS / 50E-6;
/* Thus the null input 0.5V and the 90% of FS input is
2.949075V. */
Set the trim-offset-register to zero;
Set Right-Shift register to zero (typically zero.
See the
Right-Shifting
section);
gain_result = 0h;
Clamp = FFF8h/2^(Right_Shift_Register);
For n = 15 down to 0
begin
/* 3.27675 */
/* 10000 */
/* 58981.5 */
pos
R C
R
u x
v x C
w x C
x
x
y x C
z x C
α,
,
(
)
=
+
)
+
)
( )
+
)
+
)
1
25
25
1
25
25
2
2
ADDRESS
F8h
F9h
FAh
FBh
FCh
VARIABLE
u
v
w
x
1
x
0
LSB
2
0
20E-6
100E-9
2
1
2
-7
2E-6 (signed)
FDh
y
8E-6 (signed) for 2.5k resistor
10E-9
2
-2
FEh
FFh
z
α
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| DS1856E-025T | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:Dual, Temperature-Controlled Resistors with Internally Calibrated Monitors and Password Protection |
| DS1856E-030 | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:Dual, Temperature-Controlled Resistors with Internally Calibrated Monitors and Password Protection |
| DS1856E-030/R | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:Dual, Temperature-Controlled Resistors with Internally Calibrated Monitors and Password Protection |
| DS1856E-030/T | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:Dual, Temperature-Controlled Resistors with Internally Calibrated Monitors and Password Protection |
| DS1856E-030+ | 功能描述:數(shù)字電位計 IC Dual Temp-Controlled Resistors RoHS:否 制造商:Maxim Integrated 電阻:200 Ohms 溫度系數(shù):35 PPM / C 容差:25 % POT 數(shù)量:Dual 每 POT 分接頭:256 弧刷存儲器:Volatile 緩沖刷: 數(shù)字接口:Serial (3-Wire, SPI) 描述/功能:Dual Volatile Low Voltage Linear Taper Digital Potentiometer 工作電源電壓:1.7 V to 5.5 V 電源電流:27 uA 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFN-16 封裝:Reel |
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