Datasheet

Functional description STLM75
18/40 Doc ID 13296 Rev 12
3.1.3 Temperature register
The temperature register is a two-byte (16-bit) “Read only” register (see Table 7 on
page 18). Digital temperatures from the T-to-D converter are stored in the temperature
register in two’s complement format, and the contents of this register are updated each time
the T-to-D conversion is finished.
The user can read data from the temperature register at any time. When a T-to-D
conversion is completed, the new data is loaded into a comparator buffer to evaluate fault
conditions and will update the temperature register if a read cycle is not ongoing. If a READ
is ongoing, the previous temperature will be read. Accessing the STLM75 continuously
without waiting at least one conversion time between communications will prevent the
device from updating the temperature register with a new temperature conversion result.
Consequently, the STLM75 should not be accessed continuously with a wait time of less
than t
CONV
(max).
All unused bits following the digital temperature will be zero. The MSB position of the
temperature register always contains the sign bit for the digital temperature, and Bit14
contains the temperature MSB. All bits in the temperature register default to zero at power-
up.
Note: These are comparable formats to the LM75.
3.1.4 Overlimit temperature register (T
OS
)
The T
OS
register is a two-byte (16-bit) READ/WRITE register that stores the user-
programmable upper trip-point temperature for the thermal alarm in two’s complement
format (see Table 8 on page 19). This register defaults to 80 °C at power-up (i.e., 0101 0000
0000 0000).
The format of the T
OS
register is identical to that of the temperature register. The MSB
position contains the sign bit for the digital temperature and Bit14 contains the temperature
MSB.
For 9-bit conversions, the trip-point temperature is defined by the 9 MSBs of the T
OS
register, and all remaining bits are “Don’t cares”.
Table 7. Temperature register format
Bytes HS byte LS byte
Bits
MSB TMSB TLSB LSB
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
STLM75
TD8
(Sign)
TD7
(TMSB)
TD
6
TD
5
TD
4
TD
3
TD
2
TD
1
TD0
(TLSB)
000000 0
Keys: SB = two’s complement sign bit
TMSB = temperature MSB
TLSB = temperature LSB
TDx = temperature data bits