7 Detailed Description

7.1 Overview

The TMP144 is a digital output temperature sensor in a wafer chip-scale package (WCSP) that is designed for

communicate in a daisy-chain loop 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, closing the loop. In addition, the TMP144 can do multiple device access (MDA)

commands that allow multiple TMP144 devices to respond to a single global bus command. MDA commands

reduce communication time and power in a bus that contains multiple TMP144 devices. The operation of

TMP144, is specified over a temperature range of –40 °C to 125 °C.

The TMP144 can also configure 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 TMP144 can disconnect the chain and create a serial

communication controlled by each TMP144 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 unique interface address

based upon its position in the chain, that allows it to respond to its own address. The devices can also respond

to general commands that permit the user to read or write to all devices on the bus without the need to send

individual addresses and commands to each device.

The temperature sensor in the TMP144 is the chip itself. Thermal paths run through the package bumps as well

as the package. The lower thermal resistance of metal and the low height of the devices, causes the bumps and

the topside to provide the dominant thermal paths to the sensing element on the device. To maintain accuracy in

applications that require air or surface temperature measurement, care should be taken to isolate the package

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

temperature measurement.

7.2 Functional Block Diagram

ADC

Register

Bank

Serial

Interface

Control

Logic

Rx

Tx

GND

V+

Temperature

Sensor

Circuitry

Internal

Thermal

BJT

Oscillator

Reset

SW

TMP144

SBOS891A – OCTOBER 2018 – REVISED FEBRUARY 2021

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