LM70CIMM-3 National Semiconductor, LM70CIMM-3 Datasheet - Page 9

• Manufacturer Part Number: LM70CIMM-3
• Description: Temperature Sensor IC
• Manufacturer: National Semiconductor

Specifications of LM70CIMM-3

• Peak Reflow Compatible (260 C): No
• Ic Function: Temperature Sensor IC
• Supply Voltage Max: 5.5V
• Leaded Process Compatible: No
• Mounting Type: Surface Mount
• Operating Temperature Range: -40°C To +85°C
• Temperature Sensor Function: Temp Sensor
• Output Type: Digital
• Resolution: 10+SignBit
• Package Type: MSOP
• Operating Temperature (min): -55
• Operating Temperature (max): 150C
• Operating Temperature Classification: Military
• Operating Supply Voltage (typ): 3.3/5V
• Operating Supply Voltage (max): 5.5V
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

1.0 Functional Description
The LM70 temperature sensor incorporates a band-gap type
temperature sensor and 10-bit plus sign ΔΣ ADC (Delta-Sig-
ma Analog-to-Digital Converter). Compatibility of the LM70's
three wire serial interface with SPI and MICROWIRE allows
simple communications with common microcontrollers and
processors. Shutdown mode can be used to optimize current
drain for different applications. A manufacture's ID register
identifies the LM70 as National Semiconductor product.
1.1 POWER UP AND POWER DOWN
The LM70 always powers up in a known state. The power up
default condition is continuous conversion mode. Immediatly
after power up the LM70 will output an erroneous code until
the first temperature conversion has completed.
When the supply voltage is less than about 1.6V (typical), the
LM70 is considered powered down. As the supply voltage
rises above the nominal 1.6V power up threshold, the internal
registers are reset to the power up default state described
above.
1.2 SERIAL BUS INTERFACE
The LM70 operates as a slave and is compatible with SPI or
MICROWIRE bus specifications. Data is clocked out on the
falling edge of the serial clock (SC), while data is clocked in
on the rising edge of SC. A complete transmit/receive com-
munication will consist of 32 serial clocks. The first 16 clocks
comprise the transmit phase of communication, while the
second 16 clocks are the receive phase.
When CS is high SI/O will be in TRISTATE
should be initiated by taking chip select (CS) low. This should
not be done when SC is changing from a low to high state.
Once CS is low the serial I/O pin (SI/O) will transmit the first
bit of data. The master can then read this bit with the rising
edge of SC. The remainder of the data will be clocked out by
the falling edge of SC. Once the 14 bits of data (one sign bit,
ten temperature bits and 3 high bits) are transmitted the SI/O
line will go into TRI-STATE. CS can be taken high at any time
during the transmit phase. If CS is brought low in the middle
of a conversion the LM70 will complete the conversion and
the output shift register will be updated after CS is brought
back high.
The receive phase of a communication starts after 16 SC pe-
riods. CS can remain low for 32 SC cycles. The LM70 will read
the data available on the SI/O line on the rising edge of the
serial clock. Input data is to an 8-bit shift register. The part will
detect the last eight bits shifted into the register. The receive
phase can last up to 16 SC periods. All ones must be shifted
in order to place the part into shutdown. A zero in any location
will take the LM70 out of shutdown. The following codes only
should be transmitted to the LM70:
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•
•
•
•
•
00 hex (normal operation)
01 hex (normal operation)
03 hex (normal operation)
07 hex (normal operation)
0F hex (normal operation)
1F hex (normal operation)
®
. Communication
9
•
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•
.
any others may place the part into a Test Mode. Test Modes
are used by National Semiconductor to thoroughly test the
function of the LM70 during production testing. Only eight bits
have been defined above since only the last eight transmitted,
before CS is taken HIGH, are detected by the LM70
The following communication can be used to determine the
Manufacturer's/Device ID and then immediately place the part
into continuous conversion mode. With CS continuously low:
•
•
•
•
•
Note that 210 ms will have to pass for a conversion to com-
plete before the LM70 actually transmits temperature data.
1.3 TEMPERATURE DATA FORMAT
Temperature data is represented by a 11-bit, two's comple-
ment word with an LSB (Least Significant Bit) equal to 0.25°
C:
Note: The last two bits are TRI-STATE and depicted as one
in the table.
The first data byte is the most significant byte with most sig-
nificant bit first, permitting only as much data as necessary to
be read to determine temperature condition. For instance, if
the first four bits of the temperature data indicate an overtem-
perature condition, the host processor could immediately take
action to remedy the excessive temperatures.
1.4 SHUTDOWN MODE/MANUFACTURER'S ID
Shutdown mode is enabled by writing XX FF to the LM70 as
shown in
bus is still active when the LM70 is in shutdown. Current draw
drops to less than 10 µA between serial communications.
When in shutdown mode the LM70 always will output 1000
0001 0000 00XX. This is the manufacturer's ID/Device ID in-
formation. The first 5-bits of the field (1000 0XXX) are re-
served for manufacturer's ID.
Temperature
3F hex(normal operation)
7F hex(normal operation)
FF hex (Shutdown, transmit manufacturer's ID)
Read 16 bits of temperature data
Write 16 bits of data commanding shutdown
Read 16 bits of Manufacture's/Device ID data
Write 8 to 16 bits of data commanding Conversion Mode
Take CS HIGH.
+0.25°C
−0.25°C
+150°C
+125°C
+25°C
−25°C
−55°C
0°C
Figure
7c and discussed in Section 1.2. The serial
0100 1011 0001 1111
0011 1110 1001 1111
0000 1100 1001 1111
0000 0000 0011 1111
0000 0000 0001 1111
1111 1111 1111 1111
1111 0011 1001 1111
1110 0100 1001 1111
Binary
Digital Output
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4B 1Fh
3E 9Fh
0B 9Fh
FF FFh
E4 9Fh
00 3Fh
00 1Fh
F3 9Fh
Hex