MAX1617 データシートの表示（PDF） - Maxim Integrated
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MAX1617 Datasheet PDF : 20 Pages
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MAX1617
Remote/Local Temperature Sensor
with SMBus Serial Interface
Table 2. Data Format (Twos-Complement)
TEMP.
(°C)
+130.00
+127.00
+126.50
+126.00
+25.25
+0.50
+0.25
+0.00
-0.25
-0.50
-0.75
-1.00
-25.00
-25.50
-54.75
-55.00
-65.00
-70.00
ROUNDED
TEMP.
(°C)
+127
+127
+127
+126
+25
+1
+0
+0
+0
+0
-1
-1
-25
-25
-55
-55
-65
-65
DIGITAL OUTPUT
DATA BITS
SIGN
MSB
LSB
0
111
1111
0
111
1111
0
111
1111
0
111
1110
0
001
1001
0
000
0001
0
000
0000
0
000
0000
0
000
0000
0
000
0000
1
111
1111
1
111
1111
1
110
0111
1
110
0110
1
100
1001
1
100
1001
1
011
1111
1
011
1111
Alarm Threshold Registers
Four registers store alarm threshold data, with hightem-
perature (THIGH) and low-temperature (TLOW) registers
for each A/D channel. If either measured temperature
equals or exceeds the corresponding alarm threshold
value, an ALERT interrupt is asserted.
The power-on-reset (POR) state of both THIGH registers
is full scale (0111 1111, or +127°C). The POR state of both
TLOW registers is 1100 1001 or -55°C.
Diode Fault Alarm
There is a continuity fault detector at DXP that detects
whether the remote diode has an open-circuit condition.
At the beginning of each conversion, the diode fault is
checked, and the status byte is updated. This fault detec-
tor is a simple voltage detector; if DXP rises above VCC
- 1V (typical) due to the diode current source, a fault is
detected. Note that the diode fault isn’t checked until a
conversion is initiated, so immediately after power-on
reset the status byte indicates no fault is present, even if
the diode path is broken.
If the remote channel is shorted (DXP to DXN or DXP
to GND), the ADC reads 0000 0000 so as not to trip
Table 3. Read Format for Alert Response
Address (0001100)
BIT
7
(MSB)
6
5
4
3
2
1
0
(LSB)
NAME
FUNCTION
ADD7
ADD6
ADD5
ADD4
ADD3
ADD2
ADD1
Provide the current MAX1617
slave address that was latched at
POR (Table 8)
1
Logic 1
either the THIGH or TLOW alarms at their POR settings.
In applications that are never subjected to 0°C in normal
operation, a 0000 0000 result can be checked to indicate
a fault condition in which DXP is accidentally short cir-
cuited. Similarly, if DXP is short circuited to VCC, the ADC
reads +127°C for both remote and local channels, and the
device alarms.
ALERT Interrupts
The ALERT interrupt output signal is latched and can
only be cleared by reading the Alert Response address.
Interrupts are generated in response to THIGH and TLOW
comparisons and when the remote diode is disconnected
(for continuity fault detection). The interrupt does not halt
automatic conversions; new temperature data continues
to be available over the SMBus interface after ALERT is
asserted. The interrupt output pin is open-drain so that
devices can share a common interrupt line. The interrupt
rate can never exceed the conversion rate.
The interface responds to the SMBus Alert Response
address, an interrupt pointer return-address feature (see
Alert Response Address section). Prior to taking correc-
tive action, always check to ensure that an interrupt is
valid by reading the current temperature.
Alert Response Address
The SMBus Alert Response interrupt pointer provides
quick fault identification for simple slave devices that lack
the complex, expensive logic needed to be a bus mas-
ter. Upon receiving an ALERT interrupt signal, the host
master can broadcast a Receive Byte transmission to the
Alert Response slave address (0001 100). Then any slave
device that generated an interrupt attempts to identify
itself by putting its own address on the bus (Table 3).
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