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η-FACTOR CORRECTION REGISTER

hkT

BE2

BE1

()

(1)

SOFTWARE RESET

1.008

300

ADJUST

heff =

(2)

IDENTIFICATION REGISTERS

300

1.008

heff

ADJUST

=300 -

(3)

1.000

300

ADJUST

heff =

(4)

300

1.000

heff

ADJUST

=300 -

(5)

TMP441

TMP442

www.ti.com .............................................................................................................................................. SBOS425A – DECEMBER 2008 – REVISED MARCH 2009

Table 9.

η-Factor Range

NADJUST

The TMP441/42 allow for a different

η-factor value to

η-FACTOR

BINARY

HEX

DECIMAL

= 1.008

= 1.000

used

for

converting

remote

channel

0111 1111

127

1.747977

1.734104

measurements to temperature. The remote channel

uses

sequential

current

excitation

extract

0000 1010

1.042759

1.034482

differential VBE voltage measurement to determine

0000 1000

1.035616

1.027397

the temperature of the remote transistor. Equation 1

0000 0110

1.028571

1.020408

relates this voltage and temperature.

0000 0100

1.021622

1.013513

0000 0010

1.014765

1.006711

0000 0001

1.011371

1.003344

0000 0000

1.008

1.000

The value

η in Equation 1 is a characteristic of the

1111 1111

–1

1.004651

0.996677

particular transistor used for the remote channel.

1111 1110

–2

1.001325

0.993377

When the beta compensation configuration is set to

1111 1100

–4

0.994737

0.986842

'0111' (beta compensation disabled) or the sensor is

1111 1010

–6

0.988235

0.980392

diode-connected (base shorted to collector), the

1111 1000

–8

0.981818

0.974025

η-factor used by the TMP441/42 is 1.008. When the

1111 0110

–10

0.975484

0.967741

beta compensation configuration is set to '1000' (beta

1000 0000

–128

0.706542

0.700934

compensation enabled) and the sensor is GND

collector-connected (PNP collector to ground), the

η-factor used by the TMP441/42 is 1.000. If the

η-factor used for the temperature conversion does

The TMP441/42 may be reset by writing any value to

not match the characteristic of the sensor, then

the Software Reset Register (pointer address FCh).

temperature offset is observed. The value in the

This action restores the power-on reset state to all of

η-Factor Correction Register may be used to adjust

the TMP441/42 registers as well as aborts any

the effective

η-factor according to Equation 2 and

conversion in process. The TMP441/42 also support

Equation 3 for disabled beta compensation or a

reset via the Two-Wire general call address (0000

diode-connected sensor. Equation 4 and Equation 5

0000). The TMP441/42 acknowledge the general call

may be used for enabled beta compensation and a

address and respond to the second byte. If the

GND collector-connected sensor.

second byte is 0000 0110, the TMP441/42 execute a

software reset. The TMP441/42 do not respond to

other values in the second byte.

The TMP441/42 allow for the Two-Wire bus controller

to query the device for manufacturer and device IDs

to enable software identification of the device at the

particular Two-Wire bus address. The manufacturer

ID is obtained by reading from pointer address FEh.

The device ID is obtained by reading from pointer

The

η-correction value must be stored in twos

address FFh. The TMP441/42 both return 55h for the

complement format, yielding an effective data range

manufacturer code. The TMP441 returns 41h for the

from –128 to +127. Table 9 shows the

η-factor range

device ID and the TMP442 returns 42h for the device

for both 1.008 and 1.000. The

η-correction value may

ID. These registers are read-only.

be written to and read from pointer address 21h. (The

η-correction value for the second remote channel is

read to/written from pointer address 22h.) The

effect unless the register is written to.

space

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