TMP512 datasheet(21/52 Pages) TI

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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

SBOS491 – JUNE 2010

coupled signals. The value of this capacitor should be

Where:

between 100pF and 1nF. Some applications attain

n = ideality factor of remote temperature sensor.

better

overall

accuracy

with

additional

series

T(°C) = actual temperature.

resistance; however, this increased accuracy is

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

application-specific. When series resistance is added,

Degree delta is the same for °C and K.

the total value should not be greater than 3k

Ω. If

filtering is needed, suggested component values are

For n = 1.004 and T(°C) = 100°C:

100pF and 50

Ω on each input; exact values are

application-specific.

GENERAL CALL RESET

The TMP512/13 support reset via the two-wire

(5)

General

Call

address

00h

(0000

0000b).

The

If a discrete transistor is used as the remote

TMP512/13 acknowledge the General Call address

temperature sensor with the TMP512/13, the best

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

accuracy can be achieved by selecting the transistor

06h

(0000

0110b),

the

TMP512/13

execute

according to the following criteria:

software reset state to all TMP512/13 registers, and

1. Base-emitter voltage > 0.25V at 6mA, at the

abort any conversion in progress. The TMP512/13

highest sensed temperature.

take no action in response to other values in the

second byte.

2. Base-emitter voltage < 0.95V at 120mA, at the

lowest sensed temperature.

REMOTE SENSING

3. Base resistance < 100

Ω.

The TMP512/13 are designed to be used with either

4. Tight control of VBE characteristics indicated by

discrete transistors or substrate transistors built into

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

processor chips and ASICs. Either NPN or PNP

Based

these

criteria,

two

recommended

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

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

junction is used as the remote temperature sense.

2N3906 (PNP).

NPN transistors must be diode-connected. PNP

transistors

can

either

transistor-

BASIC ADC FUNCTIONS

diode-connected, as Figure 18 and Figure 19 show.

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

Errors in remote temperature sensor readings are

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

typically the consequence of the ideality factor and

The

TMP512/13

are

powered

internal

current excitation used by the TMP512/13 versus the

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

manufacturer-specified operating current for a given

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

transistor. Some manufacturers specify a high-level

special

considerations

for

power-supply

and low-level current for the temperature-sensing

sequencing (for example, a bus voltage can be

substrate transistors. The TMP512/13 use 6mA for

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

ILOW and 120mA for IHIGH.

The TMP512/13 sense the small drop across the

The ideality factor (n) is a measured characteristic of

shunt for shunt voltage, and sense the voltage with

a remote temperature sensor diode as compared to

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

an ideal diode. The TMP512/13 allow for different

Figure 27 for an illustration of this operation.

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

When the TMP512/13 are in the normal operating

section.

mode (that is, MODE bits of Configuration Register 1

The ideality factor for the TMP512/13 is trimmed to

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

be 1.008. For transistors that have an ideality factor

shunt voltage up to the number set in the shunt

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

voltage averaging function (Configuration Register 1,

be used to calculate the temperature error. Note that

SADC bits). The devices then convert the bus voltage

for

the

equation

used

correctly,

actual

up to the number set in the bus voltage averaging

temperature (°C) must be converted to kelvins (K).

(Configuration Register 1, BADC bits). The Mode

control in Configuration Register 1 also permits

selecting modes to convert only voltage or current,

(4)

either continuously or in response to a two-wire

command.

space

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