less than or equal to it’s corresponding HIGH setpoint, as

shown in

Figure 4. Figure 5shows a simplified logic diagram

for the INT output and related circuitry.

The INT output can be disabled by setting the INT mask bit,

D7, of the configuration register. INT can be programmed to

be active high or low by the state of the INT inversion bit, D1,

in the configuration register. A “0” would program INT to be

active low. INT is an open-drain output.

1.3 T_CRIT_A OUTPUT and T_CRIT LIMIT

T_CRIT_A is activated when any temperature reading is

greater than the limit preset in the critical temperature set-

point register (T_CRIT), as shown in

Figure 6. The Status

Registers can be read to determine which event caused the

alarm. A bit in the Status Registers is set high to indicate

which temperature reading exceeded the T_CRIT setpoint

temperature and caused the alarm, see

Section 2.3.

Local and remote temperature diodes are sampled in se-

quence by the A/D converter. The T_CRIT_A output and the

Status Register flags are updated at the completion of a con-

version. T_CRIT_A and the Status Register flags are reset

only after the Status Register is read and if a temperature

conversion is below the T_CRIT setpoint, as shown in

Figure

6. Figure 7 shows a simplified logic diagram of the

T_CRIT_A and related circuitry.

Located in the Configuration Register are the mask bits for

each temperature reading, see

Section 2.5. When a mask bit

is set, its corresponding status flag will not propagate to the

T_CRIT_A output, but will still be set in the Status Registers.

Configuration register bits D5 and D3, labled “Remote

T_CRIT_A mask” must be set high before the T_CRIT set-

point is lowered in order for the T_CRIT_A output to function

properly. Setting all four mask bits or programming the

T_CRIT setpoint to 127˚C will disable the T_CRIT_A output.

1.4 POWER ON RESET DEFAULT STATES

LM82 always powers up to these known default states:

1.

Command Register set to 00h

2.

Local Temperature set to 0˚C

3.

Remote Temperature set to 0˚C until the LM82 senses a

diode present between the D+ and D− input pins.

4.

Status Register set to 00h.

5.

Configuration Register set to 00h; INT enabled and all

T_CRIT setpoints enabled to activate T_CRIT_A.

DS101297-14

* Note: Status Register Bits are reset by a read of Status Register where

bit is located.

FIGURE 4. INT Temperature Response Diagram

DS101297-21

FIGURE 5. INT output related circuitry logic diagram

DS101297-6

* Note: Status Register Bits are reset by a read of Status Register where

bit is located.

FIGURE 6. T_CRIT_A Temperature Response Diagram

DS101297-20

FIGURE 7. T_CRIT_A output related circuitry logic

diagram

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