cat6095 ON Semiconductor, cat6095 Datasheet - Page 10

• Manufacturer Part Number: cat6095
• Description: Digital Output Temperature Sensor
• Manufacturer: ON Semiconductor

CAT6095
TEMPERATURE SENSOR OPERATION
The TS component in the CAT6095 combines a
Proportional to Absolute Temperature (PTAT) sensor
with a ∑-Δ modulator, yielding a 12 bit (13 bit including
sign) digital temperature representation.
The TS is free running on an internal clock, and starts
a conversion cycle at least every 100ms. The result of
the conversion is stored in the Temperature Value
(TV) Register. While a conversion is in progress,
attempts at reading the TV register will yield
temperature values corresponding to the previous
conversion. TV register contents are retained during
Shut-down periods.
At the end of the conversion cycle, the value stored in
the TV register is compared against limit values stored
in the Alarm Temperature Upper Boundary Trip, the
Alarm Temperature Lower Boundary Trip and
Critical Temperature Trip registers. If the measured
value is outside the boundary limits or above the
critical limit, then the EVENT
The EVENT
Configuration
comparator mode and polarity.
The temperature limit registers can be Read or
Written by the host, via the serial interface. At power-
on, these registers are initialized to default values,
and should be updated by the host to the desired
values.
REGISTERS
The CAT6095 contains eight 16-bit wide registers
allocated to TS functions, as shown in Table 1. 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 CAT6095 features 3 temperature limit registers.
They are the Alarm Temperature Upper Boundary Trip
register, the Alarm Temperature Lower Boundary Trip
register, and the Critical Temperature Trip register.
The TV register contents are compared to the various
Doc. No. MD-1124 Rev. B
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Register
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for
interrupt
mode,
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limit values, and the resulting event may be used to
activate the EVENT
pin activity, this pin can be disabled while updating the
limit registers. The pin may be re-enabled, as soon as
a valid comparison can be expected. The format of
the limit registers is detailed in the corresponding bit
maps. Data format is two’s complement with the LSB
representing 0.25°C.
Testing Temperature Trip Point Operation
A common technique for verifying temperature trip
points and operation of the upper, lower and critical
temperature threshold limits is to maintain a fixed
temperature and ‘sweep’ the trigger limits.
This completely digital technique is faster when
compared to raising and/or lowering the device
temperature itself (as would happen during normal
operation). In the present implementation of the
CAT6095, this method may yield false results, since
the various flag bits representing the relation between
actual temperature and limit values, are updated only
at the end of a conversion cycle, rather than all the
time. Therefore, the flag bits may take on the correct
value as late as perhaps 100 ms after the limit
registers have been reset and an attempt at reading
the TV register is made. Automated programs used in
testing temperature sensors would need to take this
delay into account in order to produce meaningful
results.
Temperature Value Register (User Read Only)
This register stores the trip status and the temperature
measured by the TS, as detailed in the corresponding
bit map. The temperature is stored in a 13-bit, two’s
complement format, with the MSB (D12) representing
the sign. The next bit (D11) represents 128°C, and the
LSB (D0) represents 0.0625°C. D15, D14 and D13
are the trip status bits, representing the internal
temperature trip detection and are not affected by the
status of the event or configuration bits. When both
the ‘above’ (D14) and the ‘below’ (D13) bits are ‘0’,
the current temperature reading is within alarm
window boundaries, as defined in the configuration
register.
Device ID and Revision Register (Read Only)
The manufacturer assigns the device ID and device
revision. The device revision starts at 0 and is
incremented by 1 whenever the manufacturer issues
an update to the device. The format of this register is
detailed in the corresponding bit map.
¯¯¯¯¯¯ pin. To avoid superfluous EVENT
Characteristics subject to change without notice
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