TMP108

SBOS663 – APRIL 2013

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CONFIGURATION REGISTER

The configuration register is a 16-bit read and write register used to store bits that control the operational modes

of the temperature sensor. Read and write operations are performed MSB first. The format and power-up (reset)

default value of the configuration register is shown in Table 6, followed by an explanation of the register bits.

Other options for the default values are available by request.

Table 6. Configuration and Power-Up/Reset Format

BYTE

D7

D6

D5

D4

D3

D2

D1

D0

ID

CR1

CR0

FH

FL

TM

M1

M0

1

0

0

1

0

0

1

1

0

POL

0

HYS1

HYS0

0

0

0

0

2

0

0

0

1

0

0

0

0

Hysteresis Control (HYS1 and HYS0)

When operating in comparator mode, the hysteresis control bits (HYS1 and HYS0) configure the hysteresis for

the limit comparison of the TMP108 to 0°C, 1°C, 2°C, or 4°C. The default hysteresis is 1°C. Table 7 shows the

settings for HYS1 and HYS0.

Table 7. Hysteresis Settings

HYS1

HYS0

HYSTERESIS

0

0

0°C

0

1

1°C (default)

1

0

2°C

1

1

4°C

Polarity (POL)

The polarity of the ALERT pin can be programmed using the POL bit. If POL = '0' (default), the ALERT is active

low. For POL = '1', the ALERT pin is active high, and the state of the ALERT pin is inverted.

Mode Bits (M1 and M0)

The mode bits, M1 and M0, can be set to three different modes: shutdown, one-shot, or continuous conversion.

Shutdown Mode (M1 = '0', M0 = '0')

Shutdown mode saves power by shutting down all device circuitry other than the serial interface, thus reducing

current consumption to typically less than 0.5

μA. Shutdown mode is enabled when M1 and M0 = '00'. The

device shuts down when current conversion is completed.

One-Shot Mode (M1 = '0', M0 = '1')

The TMP108 features a one-shot temperature measurement mode. When the device is in shutdown mode,

writing a ‘01’ to the M1 and M0 bits starts a single temperature conversion. During the conversion, the M1 and

M0 bits reads '01'. The device returns to the shutdown state at the completion of the single conversion. After the

conversion, the M1 and M0 bits read '00'. This feature is useful for reducing the power consumption of the

TMP108 when continuous temperature monitoring is not required.

As a result of the short conversion time, the TMP108 can achieve a higher conversion rate. A single conversion

typically takes 27 ms and a read can take place in less than 20

μs. However, when using one-shot mode, 30 or

more conversions per second are possible.

Continuous Conversion Mode (M1 = '1')

When the TMP108 is in continuous conversion mode (M1 = '1'), a single conversion is performed at a rate

determined by the conversion rate bits (CR1 and CR0 in the configuration register). The TMP108 performs a

single conversion, and then goes in standby and waits for the appropriate delay set by the CR1 and CR0 bits.

See Table 8 for CR1 and CR0 settings.

8

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