MAX6626 Datasheet, PDF (11/13 Pages) Maxim Integrated Products – 9-Bit/12-Bit Temperature Sensors with I2C-Compatible Serial Interface in a SOT23

9-Bit/12-Bit Temperature Sensors with
I²C-Compatible Serial Interface in a SOT23
T_HIGH
DIE
TEMPERATURE
T_LOW
OT
(COMPARATOR MODE)
OT
(INTERRUPT MODE)
*
TEMPERATURE RESPONSE
SHOWN WITH OT SET FOR
ACTIVE LOW
TIME
Figure 6. OT Alarm Output and Reset Diagram
drain, and the MAX6625R/MAX6626R output includes
an internal 35kΩ (typ) pullup resistor. Figure 6 shows
the OT alarm operation and reset details.
Fault Queue
A programmable fault queue on the MAX6625/
MAX6626 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 OT alarm output is toggled. An out-of-
tolerance reading is above T_HIGH or below T_LOW. The
fault queue depth defaults to one at power-up and may
be programmed to one, two, four, or six consecutive
conversions. Any time the conversion result is in toler-
ance, and OT is not asserted, the queue is cleared,
even if it contains some out-of-tolerance counts.
Additionally, the fault queue automatically clears at
power-up, in shutdown, or if a master writes to any of
the T_HIGH, T_LOW, or configuration registers. Whenever
the fault queue is cleared, OT is deasserted.
For example, the fault queue is set to four, two consec-
utive out-of-tolerance readings have occurred, and the
master writes to the T_LOW register. The fault queue is
cleared and begins to look for four new consecutive
out-of-tolerance conversions.
Comparator Mode
In comparator mode, OT is asserted when the number
of consecutive conversions exceeding the value in the
T_HIGH register is equal to the depth of the fault queue.
*
*
*THIS ASSUMES DEASSERTION OF OT BY A
MASTER THROUGH THE SERIAL INTERFACE.
SEE INTERRUPT MODE SECTION.
OT deasserts when the number of consecutive conver-
sions less than the value in the T_LOW register is equal
to the depth of the fault queue. T_HIGH minus T_LOW is
the effective hysteresis of the OT output.
For example, if T_HIGH is set to +100°C, T_LOW is set to
+80°C, and the fault queue depth is set to four, OT will
not assert until four consecutive conversions exceed
+100°C. Then, OT will not deassert until four consecu-
tive conversions are less than +80°C.
Comparator mode allows autonomous clearing of an OT
fault without the intervention of a master and is ideal to
use for driving a cooling fan (Figure 7).
Interrupt Mode
In interrupt mode, the MAX6625/MAX6626 look for a
T_HIGH or a T_LOW fault based on previous fault activity.
The OT pin asserts an alarm for an undertemperature
fault, as well as for an overtemperature fault, depending
on certain conditions. If the fault queue is cleared at
power-up, the IC looks for a T_HIGH fault. After a T_HIGH
fault, the IC looks for a T_LOW fault. After a T_LOW fault,
the IC looks for a T_HIGH fault, and it will bounce back
and forth if properly deasserted each time. Once either
fault has occurred, it remains active indefinitely until
deasserted by a read of any register, and the device
then begins to look for a fault of the opposite type. Also,
if the fault queue is cleared, OT is deasserted and the
IC once again looks for a T_HIGH fault. The activation of
any fault is subject to the depth of the fault queue.
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