Rainbow Electronics MAX6636 - Manual (Page 12)

MAX6636
cases, the alert is cleared even if the fault condition
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 MAX6636 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 MAX6636 is opti-
mized for n = 1.015. A thermal diode on the substrate
of an IC is normally a pnp with the base and emitter
brought out 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 1.015 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 sensor designed for a nominal ideality
7-Channel Precision Temperature Monitor
12 ______________________________________________________________________________________
BIT NAME
POR
STATE
FUNCTION
7 (MSB) STOP 0
Standby-Mode Control Bit. If STOP is set to logic 1, the MAX6636 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 Fast remote 1 0
Channel 1 Fast-Conversion Bit. Set to logic 1 to enable fast conversion of
channel 1.
3
Resistance
cancellation
0
Resistance Cancellation Bit. When set to logic 1, the MAX6636 cancels series
resistance in the channel 1 thermal diode.
2 Reserved 0 —
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 Interrupt 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 Interrupt 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.