LM75CIM-5 National Semiconductor, LM75CIM-5 Datasheet - Page 9

• Manufacturer Part Number: LM75CIM-5
• Description: Temperature Sensor IC
• Manufacturer: National Semiconductor

Specifications of LM75CIM-5

• Mounting Type: Surface Mount
• Supply Voltage Min: 3V
• Operating Temperature Max: 125°C
• Peak Reflow Compatible (260 C): No
• Ic Function: Temperature Sensor IC
• Supply Voltage Max: 5.5V
• Leaded Process Compatible: No
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

1.0 Functional Description
1.10 INTERNAL REGISTER STRUCTURE
There are four data registers in the LM75, selected by the
Pointer register. At power-up the Pointer is set to “00”; the lo-
cation for the Temperature Register. The Pointer register
latches whatever the last location it was set to. In Interrupt
Mode, a read from the LM75, or placing the device in shut-
down mode, resets the O.S. output. All registers are read
and write, except the Temperature register which is read
only.
A write to the LM75 will always include the address byte and
the Pointer byte. A write to the Configuration register re-
quires one data byte, and the T
quire two data bytes.
Reading the LM75 can take place either of two ways: If the
location latched in the Pointer is correct (most of the time it is
expected that the Pointer will point to the Temperature regis-
ter because it will be the data most frequently read from the
LM75), then the read can simply consist of an address byte,
followed by retrieving the corresponding number of data
bytes. If the Pointer needs to be set, then an address byte,
pointer byte, repeat start, and another address byte will ac-
complish a read.
FIGURE 5. Inadvertent 8-Bit Read from 16-Bit Register where D7 is Zero (“0”)
OS
and T
HYST
(Continued)
registers re-
9
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 indicates an over-
temperature condition, the host processor could immediately
take action to remedy the excessive temperatures. At the
end of a read, the LM75 can accept either Acknowledge or
No Acknowledge from the Master (No Acknowledge is typi-
cally used as a signal for the slave that the Master has read
its last byte).
An inadvertent 8-bit read from a 16-bit register, with the D7
bit low, can cause the LM75 to stop in a state where the SDA
line is held low as shown in Figure 5 . This can prevent any
further bus communication until at least 9 additional clock
cycles have occurred. Alternatively, the master can issue
clock cycles until SDA goes high, at which time issuing a
“Stop” condition will reset the LM75.
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