Rainbow-electronics MAX7502 Manual de usuario descargar pdf (Pagina 9)

temperature rises above the T

value. OS is deassert-

ed when the temperature drops below the T

HYST

value.

See Figure 4. Set bit D1 to 1 to run the over-tempera-

ture shutdown block in interrupt mode. OS is asserted

in interrupt mode when the temperature rises above the

value or falls below the T

HYST

value. OS is

deasserted only after performing a read operation.

Set bit D0, the shutdown bit, to zero for normal opera-

tion. Set bit D0 to 1 to shut down the MAX7500/

MAX7501/MAX7502 internal blocks, dropping the sup-

ply current to 3µA. The I

C interface remains active as

long as the shutdown bit is set. The T

, T

HYST

, and

configuration registers can still be written to and read

from while in shutdown.

and T

HYST

Registers

In comparator mode, the OS output behaves like a ther-

mostat. The output asserts when the temperature rises

above the limit set in the T

deasserts when the temperature falls below the limit set

in the T

HYST

can be used to turn on a cooling fan, initiate an emer-

gency shutdown signal, or reduce system clock speed.

In interrupt mode, exceeding T

also asserts OS. OS

remains asserted until a read operation is performed on

any of the registers. Once OS has asserted due to

crossing above T

and is then reset, it is asserted

again only when the temperature drops below T

HYST

The output remains asserted until it is reset by a read.

Putting the MAX7500/MAX7501/MAX7502 into shut-

down mode also resets OS.

The T

and T

HYST

registers are accessed with 2

bytes, with bits D15–D7 containing the data. Bits

D6–D0 are don’t cares when writing to these two regis-

ters and read-back zeros when reading from these reg-

isters. The LSB represents 0.5°C while the MSB

represents 64°C. See Table 7.

MAX7500/MAX7501/MAX7502

Digital Temperature Sensors and Thermal

Watchdog with Bus Lockup Protection

_______________________________________________________________________________________ 9

D7 D6 D5 D4 D3 D2 D1 D0

000

Fault queue Fault queue

OS polarity

Comparator/

interrupt

Shutdown

Table 5. Configuration Register Definition

D4 D3 NO. OF FAULTS

00 1 (POR state)

01 2

10 4

11 6

Table 6. Configuration Register Fault

Queue Bits

HYST

OS OUTPUT

(COMPARATOR MODE)

OS SET ACTIVE LOW

OS OUTPUT

(INTERRUPT MODE)

OS SET ACTIVE LOW

READ

OPERATION

READ

OPERATION

READ

OPERATION

TEMPERATURE

Figure 4. OS Timing Diagram

UPPER BYTE LOWER BYTE

COMMAND

D15

D14 D13 D12 D11 D10 D9 D8

D6 D5 D4 D3 D2 D1

Write

Sign bit

1 = negative

0 = positive

MSB

64°C

32°C16°C8°C4°C2°C1°C

LSB

0.5°C

x xxx x x

Read

Sign bit

1 = negative

0 = positive

MSB

64°C

32°C16°C8°C4°C2°C1°C

LSB

0.5°C

0 000 0 0

Table 7. T

and T

HYST

X = Don’t care.

1 2 3 4 5 6 7 8 9 10 11 12 13

MAX7500/MAX7501/MAX7502 1

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