N34TS04
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10
Temperature Sensor Operation
The TS component in the N34TS04 combines a
Proportional to Absolute Temperature (PTAT) sensor with
a S−D modulator, yielding a 12 bit plus sign digital
temperature representation.
The TS runs on an internal clock, and starts a new
conversion cycle at least every 100 ms. The result of the
most recent conversion is stored in the Temperature Data
Register (TDR), and remains there following a TS
Shut−Down. Reading from the TDR does not interfere with
the conversion cycle.
The value stored in the TDR is compared against limits
stored in the High Limit Register (HLR), the Low Limit
Register (LLR) and/or Critical Temperature Register
(CTR). If the measured value is outside the alarm limits or
above the critical limit, then the EVENT
pin may be
asserted. The EVENT
output function is programmable, via
the Configuration Register for interrupt mode, comparator
mode and polarity.
The temperature limit registers can be Read or Written by
the host, via the serial interface. At power−on, all the
(writable) internal registers default to 0x0000, and should
therefore be initialized by the host to the desired values. The
EVENT
output starts out disabled (corresponding to
polarity active low); thus preventing irrelevant event bus
activity before the limit registers are initialized. While the
TS is enabled (not shut−down), event conditions are
normally generated by a change in measured temperature as
recorded in the TDR, but limit changes can also trigger
events as soon as the new limit creates an event condition,
i.e. asynchronously with the temperature sampling activity.
In order to minimize the thermal resistance between
sensor and PCB, it is recommended that the exposed
backside die attach pad (DAP) be soldered to the PCB
ground plane.
Registers
The N34TS04 contains eight 16−bit wide registers
allocated to TS functions, as shown in Table 10. Upon
power−up, the internal address counter points to the
capability register.
Capability Register (User Read Only)
This register lists the capabilities of the TS, as detailed in
the corresponding bit map.
Configuration Register (Read/Write)
This register controls the various operating modes of the
TS, as detailed in the corresponding bit map.
Temperature Trip Point Registers (Read/Write)
The N34TS04 features 3 temperature limit registers, the
HLR, LLR and CLR mentioned earlier. The temperature
value recorded in the TDR is compared to the various limit
values, and the result is used to activate the EVENT
pin. To
avoid undesirable EVENT
pin activity, this pin is
automatically disabled at power−up to allow the host to
initialize the limit registers and the converter to complete the
first conversion cycle under nominal supply conditions.
Data format is two’s complement with the LSB representing
0.25°C, as detailed in the corresponding bit maps.
Temperature Data Register (User Read Only)
This register stores the measured temperature, as well as
trip status information. B15, B14, and B13 are the trip status
bits, representing the relationship between measured
temperature and the 3 limit values; these bits are not affected
by EVENT status or by Configuration register settings
regarding EVENT
pin. Measured temperature is
represented by bits B12 to B0. Data format is two’s
complement, where B12 represents the sign, B11 represents
128°C, etc. and B0 represents 0.0625°C.
Manufacturer ID Register (Read Only)
The manufacturer ID assigned by the PCI−SIG trade
organization to the N34TS04 device is fixed at 0x1B09.
Device ID and Revision Register (Read Only)
This register contains manufacturer specific device ID
and device revision information.
