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ONE-SHOT CONVERSION

V

BE2

nkT

q

ln

I

2

I

1

(1)

n

eff

+

1.008

300

(2)

N

ADJUST

+ 300 *

300

1.008

n

eff

(3)

n-FACTOR CORRECTION REGISTER

TMP421

TMP422

TMP423

SBOS398B – JULY 2007 – REVISED MARCH 2008

Table 7. Conversion Rate Register

CONVERSION RATE REGISTER (Read/Write = 0Bh, POR = 07h)

R7

R6

R5

R4

R3

R2

R1

R0

CONVERSIONS/SEC

0

0

0

0

0

0

0

0

0.0625

11

32

0

0

0

0

0

0

0

1

0.125

17

38

0

0

0

0

0

0

1

0

0.25

28

49

0

0

0

0

0

0

1

1

0.5

47

69

0

0

0

0

0

1

0

0

1

80

103

0

0

0

0

0

1

0

1

2

128

155

0

0

0

0

0

1

1

0

190

220

0

0

0

0

0

1

1

1

373

413

(1)

Conversion rate shown is for only one or two enabled measurement channels. When three channels are enabled, the conversion rate is

2 and 2/3 conversions-per-second. When four channels are enabled, the conversion rate is 2 per second.

(2)

Conversion rate shown is for only one enabled measurement channel. When two channels are enabled, the conversion rate is 4

conversions-per-second. When three channels are enabled, the conversion rate is 2 and 2/3 conversions-per-second. When four

channels are enabled, the conversion rate is 2 conversions-per-second.

When the TMP421/22/23 are in shutdown mode

The value n in Equation 1 is a characteristic of the

(SD = 1 in the Configuration Register 1), a single

particular transistor used for the remote channel. The

conversion is started on all enabled channels by

power-on reset value for the TMP421/22/23 is n =

writing any value to the One-Shot Start Register,

1.008. The value in the n-Factor Correction Register

pointer address 0Fh. This write operation starts one

may be used to adjust the effective n-factor according

conversion; the TMP421/22/23 return to shutdown

to Equation 2 and Equation 3.

mode when that conversion completes. The value of

the data sent in the write command is irrelevant and

is not stored by the TMP421/22/23. When the

TMP421/22/23 are in shutdown mode, the conversion

sequence currently in process must be completed

before a one-shot command can be issued. One-shot

commands issued during a conversion are ignored.

The

n-correction

value

must

be

stored

in

two's-complement format, yielding an effective data

range from –128 to +127. The n-correction value may

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

The TMP421/22/23 allow for a different n-factor value

n-correction value for the second remote channel

to

be

used

for

converting

remote

channel

(TMP422 and TMP423) may be written and read from

measurements to temperature. The remote channel

pointer address 22h. The n-correction value for the

uses

sequential

current

excitation

to

extract

a

third remote channel (TMP423 only) may be written

to and read from pointer address 23h. The register

the temperature of the remote transistor. Equation 1

power-on reset value is 00h, thus having no effect

describes this voltage and temperature.

unless the register is written to.

Copyright © 2007–2008, Texas Instruments Incorporated

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