TX

RX

GND

V+

C

F

0.1 F

³

m

Supply Voltage

6

TMP104

SBOS564B – NOVEMBER 2011 – REVISED DECEMBER 2018

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7 Detailed Description

7.1 Overview

The TMP104 is a digital output temperature sensor in a wafer chip-scale package (WCSP) that is optimal for

thermal management and thermal profiling. The TMP104 includes a SMAART wire interface that is capable of

communicating in a daisy-chain with up to 16 devices on a single bus. The interface requires two pins from the

host; the first device in the daisy-chain receives data from the host and the last device in the daisy-chain returns

data to the host. In addition, the TMP104 has the capability of executing multiple device access (MDA)

commands that allow multiple TMP104s to respond to a single global bus command. MDA commands reduce

communication time and power in a bus that contains multiple TMP104 devices. The TMP104 is specified over a

temperature range of –40ºC to +125ºC.

The TMP104 also has the capability of configuring the bus in a transparent mode, where the input from the host

is sent directly to the next device in the chain without delay. Additionally, the TMP104 can disconnect the chain

and create a serial communication controlled by each TMP104 on the bus, thereby allowing each device to have

configurable addressing and interrupt capabilities. The input pin, RX, is a high-impedance node. The output pin,

TX, has an internal push-pull output stage that can drive the host to GND or V+.

After an initialization sequence, each device on the bus is programmed with its own interface address that allows

it to respond to its own address and also respond to general commands that permit the user to read or write to all

of the devices on the bus without having to send its individual address and command to each individual device.

The temperature sensor in the TMP104 is the chip itself. Thermal paths run through the package bumps as well

as the package. The lower thermal resistance of metal causes the bumps to provide the primary thermal path. To

maintain accuracy in applications that require air or surface temperature measurement, take care to isolate the

package from ambient air temperature. A thermally-conductive adhesive can help to achieve accurate surface

temperature measurement.

7.2 Feature Description

7.2.1 Timeout Function

A timeout mechanism is implemented on the TMP104 to allow for re-synchronization of the SMAART wire

interface if synchronization between the host and the TMP104 is lost for 28 ms (typical). If the timeout period

expires between the calibration byte and the command byte, or between the command byte and any data byte,

or between any data bytes, the TMP104 resets the SMAART wire interface circuitry so that it expects the baud

rate calibration command to restart. Every time a byte is transmitted on the SMAART wire interface, this timeout

period restarts.

7.2.2 Noise

The TMP104 is a very low-power device and generates very low noise on the supply bus. Applying a bypass

capacitor to the V+ pin of the TMP104 can further reduce any noise the TMP104 might propagate to other

components. CF in Figure 5 should be greater than 0.1 μF.

Figure 5. Noise Reduction