Datasheet

LM95172
www.ti.com SNOSB33B –DECEMBER 2009–REVISED MARCH 2013
Power-Up Sequence
WARNING
In all cases listed below the V
DD ANALOG
waveform must not lag the V
DD
IO
waveform
Linear Power-up In the case where the V
DD ANALOG
and V
DD IO
voltage-vs.-time function is linear, the specified
minimum operating voltage must be reached in 5 ms or less.
Resistor-Capacitor (R-C) Charging Exponential Power-up In the case where the V
DD ANALOG
and V
DD IO
voltage-vs.-time function is as a typical R-C Charging exponential function the time constant must be less
than or equal to 1.25 ms.
Other Power-up Functions In the case where the V
DD ANALOG
and V
DD IO
voltage-vs.-time characteristic follows
another function the following requirements must be met:
1. The specified minimum operating voltage values for V
DD ANALOG
and V
DD IO
must be reached in 5 ms or less.
2. The slope of the V
DD ANALOG
and V
DD IO
power-up curves must be greater than or equal to 0.7 V/ms at any
time before the specified minimum operating voltage is reached.
3. The slope of the V
DD ANALOG
and V
DD IO
power-up curves must not allow ringing such that the voltage is
allowed to drop below the specified minimum operating voltage at any time after the specified minimum
operating voltage is reached.
Power On Reset (POR)
After the requirements of Software Reset Sequence and Power-Up Sequence are met each register will then
contain its defined POR default value. Any of the following actions may cause register values to change from
their POR value:
1. The master writes different data to any Read/Write (R/W) bits, or
2. The LM95172EWG is powered down.
The specific POR Value of each register is listed in INTERNAL REGISTER STRUCTURE.
ONE SHOT CONVERSION
The LM95172EWG features a one-shot conversion bit, which is used to initiate a singe conversion and
comparison cycle when the LM95172EWG is in shutdown mode. While the LM95172EWG is in shutdown mode,
writing a "1" to the One-Shot bit in the Control/Status Register will cause the LM95172EWG to perform a single
temperature conversion and update the Temperature Register and the affected status bits. Operating the
LM95172EWG in this one-shot mode allows for extremely low average-power comsumption, making it ideal for
low-power applications.
When the One-shot bit is set, the LM95172EWG initiates a temperature conversion. After this initiation, but
before the completion of the conversion, and resultant register updates, the LM95172EWG is in a "one-shot"
state. During this state, the Data Available (DAV) flag in the Control/Status Register is "0" and the Temperature
Register contains the value 8000h (-256°C). All other registers contain the data that was present before initiating
the one-shot conversion. After the temperature measurement is complete, the DAV flag will be set to "1" and the
temperature register will contain the resultant measured temperature.
OVERTEMP OUTPUT
The Over-temperature (OVERTEMP) output is a temperature switch signal that indicates when the measured
temperature exceeds the T
HIGH
programmed limit. The programmable T
HIGH
register sets the high temperature
limit and the T
LOW
register is used to set the hysteresis. The T
LOW
register also sets the temperature below which
the OVERTEMP output resets. The OVERTEMP output of the LM95172EWG behaves as a temperature
comparator. The following explains the operation of OVERTEMP. Figure 10 illustrates the OVERTEMP output
behavior.
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