lm95172qa2 National Semiconductor Corporation, lm95172qa2 Datasheet - Page 11

• Manufacturer Part Number: lm95172qa2
• Description: 13-bit To 16-bit Digital Temperature Sensor With 3-wire Interface
• Manufacturer: National Semiconductor Corporation

1.1 INITIAL SOFTWARE RESET AND POWER-UP
SEQUENCES AND POWER ON RESET (POR)
1.1.1 Software Reset Sequence
A software reset sequence must be followed, after the initial
V
minimum operating voltages, in order to ensure proper oper-
ation of the LM95172QA2 MDA.
The software reset sequence is as follows:
1. Allow V
mum operating voltages, as specified in the Operating Rat-
ings section, and in a manner as specified in section 1.1.2
below.
2. Write a “1” to the Shutdown bit, Bit 15 of the Control/Status
Register, and hold it high for at least the specified maximum
conversion time for the initial default of 13-bits resolution, in
order to ensure that a complete reset operation has occurred.
(See the Temperature Conversion Time specifications within
the Temperature-to-Digital Characteristics section.)
3. Write a “0” to the Shutdown bit to restore the LM95172QA2
MDA to normal mode.
4. Wait for at least the specified maximum conversion time for
the initial default of 13-bits resolution in order to ensure that
accurate data appears in the Temperature Register.
1.1.2 Power-Up Sequence
A. Linear Power-up
In the case where the V
function is linear, the specified minimum operating voltage
must be reached in 5 ms or less.
DD ANALOG
DD ANALOG
and V
DD IO
and V
supply voltages reach their specified
DD ANALOG
DD IO
to reach their specified mini-
and V
DD IO
voltage-vs.-time
11
B. Resistor-Capacitor (R-C) Charging Exponential Power-up
In the case where the V
function is as a typical R-C Charging exponential function the
time constant must be less than or equal to 1.25 ms.
C. Other Power-up Functions
In the case where the V
characteristic follows another function the following require-
ments must be met:
(1) The specified minimum operating voltage values for V
ANALOG
(2) The slope of the V
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
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.
1.1.3 Power On Reset (POR)
After the requirements of section 1.1.1 and 1.1.2 above 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 LM95172QA2 MDA is powered down.
The specific POR Value of each register is listed in Section
1.7 under Internal Register Structure.
and V
DD IO
must be reached in 5 ms or less.
DD ANALOG
DD ANALOG
DD ANALOG
DD ANALOG
and V
and V
and V
and V
DD IO
DD IO
DD IO
DD IO
power-up curves
power-up curves
voltage-vs.-time
voltage-vs.-time
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DD