CAT6095
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8
Temperature Sensor Operation
The  CAT6095  temperature  sensor  (TS)  combines  a
Proportional to Absolute Temperature (PTAT) sensor with
a  SD  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
ShutDown. 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  poweron,  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  shutdown),  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  CAT6095  contains  eight  16bit  wide  registers
allocated  to  TS  functions,  as  shown  in  Table  6.  Upon
powerup,  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 CAT6095 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 powerup 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 twos complement with the LSB representing
0.25癈, 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.
Measured temperature is represented by bits B12 to B0. Data
format is twos complement, where B12 represents the sign,
B11 represents 128癈, etc. and B0 represents 0.0625癈.
Manufacturer ID Register (Read Only)
The  manufacturer  ID  assigned  by the PCISIG trade
organization to the CAT6095 device is 0x1B09.
Device ID and Revision Register (Read Only)
This register contains manufacturer specific device ID
and device revision information.