Rainbow-electronics MAX6642 Manual do Utilizador descarregar pdf (Página 12)

MAX6642

tracks the actual temperature within a conversion cycle.

When measuring temperature with discrete remote sen-

sors, smaller packages, such as SOT23s, yield the best

thermal response times. Take care to account for ther-

mal gradients between the heat source and the sensor,

and ensure that stray air currents across the sensor

package do not interfere with measurement accuracy.

Self-heating does not significantly affect measurement

accuracy. Remote-sensor self-heating due to the diode

current source is negligible. For the local diode, the

worst-case error occurs when autoconverting at the

fastest rate and simultaneously sinking maximum cur-

rent at the ALERT output. For example, with V

+5.0V, at an 8Hz conversion rate and with ALERT sink-

ing 1mA, the typical power dissipation is:

5.0V x 450µA + 0.4V x 1mA = 2.65mW

J-A

for the 6-pin TDFN package is about +41°C/W, so

assuming no copper PC board heat sinking, the result-

ing temperature rise is:

∆T = 2.65mW x 41°C/W = +0.11°C

Even under nearly worst-case conditions, it is difficult to

introduce a significant self-heating error.

Chip Information

TRANSISTOR COUNT: 7744

PROCESS: BiCMOS

±1°C, SMBus-Compatible Remote/Local

Temperature Sensor with Overtemperature Alarm

12 ______________________________________________________________________________________

Functional Diagram

MAX6642

MUX

REMOTE

LOCAL

ADC

CONTROL

LOGIC

SMBus

READ

WRITE

ADDRESS

DECODER

DXP

SCLK

SDA

COMMAND BYTE

REMOTE TEMPERATURE

LOCAL TEMPERATURE

ALERT THRESHOLD

ALERT RESPONSE

ADDRESS

ALERT

DIODE

FAULT

TOP VIEW

(BUMPS ON BOTTOM)

GND

4DXP

SDA

SCLK

TDFN

ALERT

MAX6642

Pin Configuration

1 2 ... 7 8 9 10 11 12 13

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