Datasheet

APPLICATION INFORMATION
COMMUNICATING WITH THE TMP122
TMP122-EP
www.ti.com .......................................................................................................................................................................................... SBOS454 – NOVEMBER 2008
The TMP122 digital temperature sensor is optimal for thermal management and thermal protection applications.
The TMP122 is SPI interface-compatible and specified for a temperature range of -55 ° C to 125 ° C.
The TMP122 requires minimal external components for operation, needing only a pullup resistor on the ALERT
pin and a bypass capacitor on the supply. Bypass capacitors of 0.1 µ F is recommended. Figure 1 shows typical
connections for the TMP122.
Figure 1. Typical Connections
To maintain accuracy in applications requiring air or surface temperature measurement, care should be taken to
isolate the package and leads from ambient air temperature.
Figure 2. Multiple Command Sequence
The TMP122 converts continuously. If CS is brought low during a conversion the conversion process continues,
but the last completed conversion is available at the output register. Communication with the TMP122 is initiated
by pulling CS low. The first 16 clocks of data transfer will return temperature data from the temperature sensors.
The 16-bit data word is clocked out sign bit first, followed by the MSB. Any portion of the 16-bit word may be
read before raising CS. If the user wishes to continue with CS low, the following 16 clocks transfer in a READ or
WRITE command. READ and WRITE commands are described in Table 1 and Table 2 .
The READ command contains an embedded address in bits D4 and D3 to identify which register to read. Bits D4
and D3 are internally registered and will hold their value following a READ command until an entire 16-bit read is
completed by the user. The completion of the 16-bit READ acknowledges that the READ command has been
completed. If the user issues a READ command and then raises CS with less than 16 subsequent clocks, the
data from that register will be available at the next fall of CS. Teh registered READ address will remain in effect
until a full 16 clocks have been received. After the compleation of a 16-bit READ from the part, the READ
address is reset to return data from the Temperature Register. A WRITE command to a register will not change
the READ address registered. For further discussion on the READ address register, see the Read Address
Register section.
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Product Folder Link(s): TMP122-EP