Rainbow-electronics MAX6635 Instrukcja Użytkownika Pobierz pdf (Strona 10)

MAX6633/MAX6634/MAX6635

bit. Registers T

HIGH

and T

LOW

are 16 bits, read/write,

and contain values that trigger ALERT and OVERT.

HYST

is 16 bits, read/write, and contains the

values by which the temperature must rise or fall

beyond T

HIGH

, T

LOW

, or T

MAX

, before ALERT or

OVERT deassert.

Temperature Conversion

An on-chip bandgap reference produces a signal pro-

portional to absolute temperature (PTAT), as well as the

temperature-stable reference voltage necessary for the

analog-to-digital conversion. The PTAT signal is digi-

tized by the on-board ADC to a resolution of 0.0625°C.

The resulting digital value is placed in the Temperature

and asynchronously from the serial interface at a rate of

500ms per conversion. When the Temperature register

is read, the conversion in progress is aborted. The bus

transaction is completed by a stop condition.

Fault Queue (MAX6634/MAX6635)

A programmable fault queue on the MAX6634/

MAX6635 eliminates spurious alarm activity in noisy

environments. The queue sets the number of consecu-

tive out-of-tolerance temperature readings that must

occur before the ALERT or OVERT alarm outputs are

toggled. An out-of-tolerance reading is above T

HIGH

MAX

or below T

LOW

. The fault queue depth defaults to

1 at power-up and may be programmed—through the

Configuration register—to four consecutive conver-

sions. Any time the conversion result is in tolerance,

and the particular alarm output is not asserted, the

queue is cleared, even if it contains some out-of-toler-

ance counts. Additionally, the fault queue automatically

clears at power-up and in shutdown. Whenever the

fault queue is cleared, the alarm outputs are deassert-

ed. Figure 9 is the alarm output and reset diagram.

12-Bit Plus Sign Temperature Sensors with

SMBus/I

C-Compatible Serial Interface

10 ______________________________________________________________________________________

*IN INTERRUPT MODE, READING THE DEVICE CLEARS ALERT.

OTHERWISE, IT WOULD REMAIN LOW INDEFINITELY UNTIL CLEARED.

MAX

- T

HYST

HIGH

- T

HYST

LOW

+ T

HYST

ALERT

COMPARATOR MODE

ALERT

INTERRUPT MODE

OVERT

COMPARATOR MODE

ONLY

Figure 9. Alarm Output and Reset Diagram

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 16

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