TMP512 datasheet(21/62 Pages) TI2

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ERR =

1.004

1.008

(

273.15+100 C

)

=1.48 C

ERR

ERR =

1.008

(

273.15+T( C)

TMP512

TMP513

www.ti.com

SBOS491A

– JUNE 2010 – REVISED MAY 2011

between 100pF and 1nF. Some applications attain

Where:

better

overall

accuracy

with

additional

series

n = ideality factor of remote temperature sensor.

resistance; however, this increased accuracy is

°C) = actual temperature.

application-specific. When series resistance is added,

TERR = error in TMP512/13 because n ≠ 1.008.

the total value should not be greater than 3k

Ω. If

Degree delta is the same for

°C and K.

filtering is needed, suggested component values are

100pF and 50

Ω on each input; exact values are

For n = 1.004 and T(

°C) = 100°C:

application-specific.

GENERAL CALL RESET

The TMP512/13 support reset via the two-wire

General

Call

address

00h

(0000

0000b).

The

(5)

TMP512/13 acknowledge the General Call address

If a discrete transistor is used as the remote

and respond to the second byte. If the second byte is

temperature sensor with the TMP512/13, the best

06h

(0000

0110b),

the

TMP512/13

execute

accuracy can be achieved by selecting the transistor

software reset state to all TMP512/13 registers, and

according to the following criteria:

abort any conversion in progress. The TMP512/13

1. Base-emitter voltage

> 0.25V at 6μA, at the

take no action in response to other values in the

highest sensed temperature.

second byte.

2. Base-emitter voltage

< 0.95V at 120μA, at the

REMOTE SENSING

lowest sensed temperature.

3. Base resistance

< 100Ω.

The TMP512/13 are designed to be used with either

discrete transistors or substrate transistors built into

4. Tight control of VBE characteristics indicated by

processor chips and ASICs. Either NPN or PNP

small variations in hFE (that is, 50 to 150).

transistors can be used, as long as the base-emitter

Based

these

criteria,

two

recommended

junction is used as the remote temperature sense.

small-signal transistors are the 2N3904 (NPN) or

NPN transistors must be diode-connected. PNP

2N3906 (PNP).

transistors

can

either

transistor-

diode-connected, as Figure 19 and Figure 21 show.

BASIC ADC FUNCTIONS

Errors in remote temperature sensor readings are

The two analog inputs to the TMP512/13, VIN+ and

typically the consequence of the ideality factor and

VIN–, connect to a shunt resistor in the bus of interest.

current excitation used by the TMP512/13 versus the

The

TMP512/13

are

powered

internal

manufacturer-specified operating current for a given

subregulator, which has a typical output of 3.3V. The

transistor. Some manufacturers specify a high-level

bus being sensed can vary from 0V to 26V. There are

and low-level current for the temperature-sensing

special

considerations

for

power-supply

substrate transistors. The TMP512/13 use 6

μA for

sequencing (for example, a bus voltage can be

ILOW and 120μA for IHIGH.

present with the supply voltage off, and vice-versa).

The ideality factor (n) is a measured characteristic of

The TMP512/13 sense the small drop across the

a remote temperature sensor diode as compared to

shunt for shunt voltage, and sense the voltage with

an ideal diode. The TMP512/13 allow for different

respect to ground from VIN– for the bus voltage. See

n-factor values; see the n-Factor Correction Register

Figure 29 for an illustration of this operation.

section.

When the TMP512/13 are in the normal operating

The ideality factor for the TMP512/13 is trimmed to

mode (that is, MODE bits of Configuration Register 1

be 1.008. For transistors that have an ideality factor

are set to '111'), the devices continuously convert the

that does not match the TMP512/13, Equation 4 can

shunt voltage up to the number set in the shunt

be used to calculate the temperature error. Note that

voltage averaging function (Configuration Register 1,

for

the

equation

used

correctly,

actual

SADC bits). The devices then convert the bus voltage

temperature (

°C) must be converted to kelvins (K).

up to the number set in the bus voltage averaging

(Configuration Register 1, BADC bits). The Mode

control in Configuration Register 1 also permits

(4)

selecting modes to convert only voltage or current,

either continuously or in response to a two-wire

space

command.

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