7-Channel Precision Temperature Monitor

with Beta Compensation

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13

tion exists, but the ALERT output reasserts at the end of

the next conversion. The bits indicating the fault for the

OVERT interrupt output clear only on reading the status 2

register even if the fault conditions still exist. Reading the

status 2 register does not clear the OVERT interrupt out-

put. To eliminate the fault condition, either the measured

temperature must drop below the temperature threshold

minus the hysteresis value (4°C), or the trip temperature

must be set at least 4°C above the current temperature.

Applications Information

Remote-Diode Selection

The MAX6693 directly measures the die temperature of

CPUs and other ICs that have on-chip temperature-

sensing diodes (see the

Typical Application Circuit) or

it can measure the temperature of a discrete diode-

connected transistor.

Effect of Ideality Factor

The accuracy of the remote temperature measure-

ments depends on the ideality factor (n) of the remote

“diode” (actually a transistor). The MAX6693 is opti-

mized for n = 1.006 (channel 1) and n = 1.008 (chan-

nels 2–6). A thermal diode on the substrate of an IC is

normally a pnp with the base and emitter brought out to

the collector (diode connection) grounded. DXP_ must

be connected to the anode (emitter) and DXN_ must be

connected to the cathode (base) of this pnp. If a sense

transistor with an ideality factor other than 1.006 or

1.008 is used, the output data is different from the data

obtained with the optimum ideality factor. Fortunately,

the difference is predictable. Assume a remote-diode

is used to measure the temperature of a diode with a

different ideality factor n1. The measured temperature

BIT

NAME

POR

STATE

FUNCTION

7 (MSB)

STOP

0

Standby-Mode Control Bit. If STOP is set to logic 1, the MAX6693 stops

converting and enters standby mode.

6

POR

0

Reset Bit. Set to logic 1 to put the device into its power-on state. This bit is self-

clearing.

5

TIMEOUT

0

Timeout Enable Bit. Set to logic 0 to enable SMBus timeout.

4

RESERVED

0

Reserved. Must set to 0.

3

Resistance

cancellation

1

Resistance Cancellation Bit. When set to logic 1, the MAX6693 cancels series

resistance in the channel 1 thermal diode.

2

Beta compensation

1

Beta Compensation Bit. When set to logic 1, the MAX6693 compensates for low

beta in the channel 1 thermal sensing transistor.

1

Reserved

0

—

0

Reserved

0

—

Table 4. Configuration 1 Register

Table 5. Configuration 2 Register

BIT

NAME

POR

STATE

FUNCTION

7 (MSB)

Reserved

0

—

6

Mask Local ALERT

0

Local Alert Mask. Set to logic 1 to mask local channel

ALERT.

5

Mask ALERT 6

0

Channel 6 Alert Mask. Set to logic 1 to mask channel 6

ALERT.

4

Mask ALERT 5

0

Channel 5 Alert Mask. Set to logic 1 to mask channel 5

ALERT.

3

Mask ALERT 4

0

Channel 4 Alert Mask. Set to logic 1 to mask channel 4

ALERT.

2

Mask ALERT 3

0

Channel 3 Alert Mask. Set to logic 1 to mask channel 3

ALERT.

1

Mask ALERT 2

0

Channel 2 Alert Mask. Set to logic 1 to mask channel 2

ALERT.

0

Mask ALERT 1

0

Channel 1 Alert Mask. Set to logic 1 to mask channel 1

ALERT.