DS1854 Ver la hoja de datos (PDF) - Maxim Integrated
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DS1854 Datasheet PDF : 22 Pages
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Dual Temperature-Controlled Resistors with
Two Monitors
Table 1. Scales for Monitor Channels
SIGNAL
+FS
SIGNAL
Temperature
VCC
MON1
127.996°C
6.55V
2.5V
MON2
2.5V
+FS
7FFF
FFFF
FFFF
FFFF
-FS
SIGNAL
-128°C
0V
0V
0V
-FS
8000
0000
0000
0000
Table 2. Signal Comparison
SIGNAL
VCC
MON1
MON2
Temperature
FORMAT
Unsigned
Unsigned
Unsigned
Two’s complement
Monitored Signals
Each signal (VCC, MON1, MON2, and temperature) is
available as a 16-bit value with 12-bit accuracy (left-jus-
tified) over the serial bus. See Table 1 for signal scales
and Table 2 for signal format. The four LSBs should be
masked when calculating the value.
The signals are updated every frame rate (tframe) in a
round-robin fashion.
The comparison of all four signals with the high and low
user-defined values are done automatically. The corre-
sponding flags are set to 1 within a specified time of
the occurrence of an out-of-limit condition.
Calculating Signal Values
The LSB = 100µV for VCC, and the LSB = 38.147µV for
the MON signals.
Monitor/VCC Bit Weights
MSB 215 214 213 212 211 210 29 28
LSB 27 26 25 24 23 22 21 20
Table 3. Look-up Table Address for
Corresponding Temperature Values
TEMPERATURE
<-40°C
-40°C
-38°C
-36°C
-34°C
—
+98°C
+100°C
+102°C
>+102°C
CORRESPONDING LOOK-UP
TABLE ADDRESS
80h
80h
81h
82h
83h
—
C5h
C6h
C7h
C7h
To calculate the value of the temperature, treat the
two’s complement value binary number as an unsigned
binary number then convert to decimal and divide by
256. If the result is greater than or equal to 128, then
subtract 256 from the result.
Temperature: high byte: -128°C to +127°C signed; low
byte: 1/256°C.
Monitor Conversion Example
MSB (BIN)
11000000
10000000
LSB (BIN)
00000000
10000000
VOLTAGE (V)
1.875
1.255
Temperature Bit Weights
S
26
25
24
23
22
21
20
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
VCC Conversion Example
MSB (BIN)
LSB (BIN)
10000000
10000000
11000000
11111000
VOLTAGE (V)
3.29
4.94
To calculate the value of VCC, convert the unsigned 16-
bit value to decimal and multiply by 100µV.
To calculate the value of MON1 or MON2, convert the
unsigned 16-bit value to decimal and multiply by
38.147µV.
Temperature Conversion Example
MSB (BIN)
01000000
01000000
01011111
11110110
11011000
LSB (BIN)
00000000
00001111
00000000
00000000
00000000
TEMPERATURE (°C)
64
64.059
95
-10
-40
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