CAT34TS02
http://onsemi.com
13
Temperature Sensor Operation
The  TS  component  in  the  CAT34TS02  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  CAT34TS02 contains eight 16bit wide registers
allocated  to  TS  functions,  as  shown  in  Table  9.  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 CAT34TS02 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
regarding   EVENT
   pin.   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 CAT34TS02 device is fixed at 0x1B09.
Device ID and Revision Register (Read Only)
This register contains manufacturer specific device ID
and device revision information.
Table 9. THE TS REGISTERS
Register Address
Register Name
PowerOn Default
Read/Write
0x00
Capability Register
0x007F
Read
0x01
Configuration Register
0x0000
Read/Write
0x02
High Limit Register
0x0000
Read/Write
0x03
Low Limit Register
0x0000
Read/Write
0x04
Critical Limit Register
0x0000
Read/Write
0x05
Temperature Data Register
Undefined
Read
0x06
Manufacturer ID Register
0x1B09
Read
0x07
Device ID/Revision Register
Rev. B
0x0813
Read
Rev. C
0x0A00