MIC184YM Micrel Inc, MIC184YM Datasheet - Page 11

• Manufacturer Part Number: MIC184YM
• Description: IC SUPERVISOR LOCAL/REMOTE 8SOIC
• Manufacturer: Micrel Inc

Specifications of MIC184YM

• Output Type: I²C™/SMBus™
• Lead Free Status: Lead free
• Function: Temp Monitoring System (Sensor)
• Topology: ADC (Sigma Delta), Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -55°C ~ 125°C, External Sensor
• Output Alarm: Yes
• Output Fan: No
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: -55°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Temperature Sensor Function: Temp Sensor
• Package Type: SOIC
• Operating Temperature (min): -55
• Operating Temperature (max): 125C
• Operating Temperature Classification: Military
• Operating Supply Voltage (min): 2.7V
• Operating Supply Voltage (typ): 3.3/5V
• Operating Supply Voltage (max): 5.5V
• Lead Free Status / RoHS Status: Compliant
• Other names: 576-1676-5; MIC184YM

MIC184’s power consumption drops to 1µA typical in shutdown
mode. All registers may be read from, or written to, while in
shutdown mode. Serial bus activity will slightly increase the
MIC184’s power consumption.
Entering shutdown mode will not affect the state of INT when
the device is in comparator mode (MODE = 0). However, If
the device is shut down while in interrupt mode, the INT pin
will be deasserted and the internal latch (STS) holding the
interrupt status will be cleared. Therefore, no interrupts will
be generated while the MIC184 is in shutdown mode, and
the interrupt status will not be retained. It is important to
note, however, that the cause of the last temperature event
will be retained in the MIC184. This is described further in
“Comparator and Interrupt Modes” below. The diode fault
detection mechanism (see “Diode Faults”) requires one or
more A/D conversion cycles to detect external sensor faults.
Hence, no diode faults will be detected while the device is
in shutdown.
Comparator and Interrupt Modes
Depending on the setting of the MODE bit in the configura-
tion register, the INT output will behave either as an interrupt
request signal or a thermostatic control signal. Thermostatic
operation is known as comparator mode. The INT output is
asserted whenever the measured temperature, as reported
in the TEMP register, exceeds the threshold programmed in
the T_SET register for the number of conversions specified by
Fault_Queue (described below). In comparator mode, INT will
remain asserted unless and until the measured temperature
falls below the value in the T_HYST register for Fault_Queue
conversions. No action on the part of the host is required for
operation in comparator mode. Note that entering shutdown
mode will not affect the state of INT when the device is in
comparator mode.
In interrupt mode, once a temperature event has caused STS
to be set, and the INT output to be asserted, they will not be
automatically deasserted when the measured temperature
falls below T_HYST. They can only be deasserted by reading
any of the MIC184's internal registers or by putting the device
into SHUTDOWN mode. If the most recent temperature event
was an overtemperature condition, STS will not be set again,
and INT cannot be reasserted, until the device has detected
that TEMP < T_HYST. Similarly, if the most recent temperature
event was an undertemperature condition, STS will in be set
again, and INT cannot be reasserted, until the device has
detected that TEMP > T_SET. This keeps the internal logic of
the MIC184 backward compatible with that of the LM75 and
similar devices. There is a software override for this: while
the MIC184 is operating in interrupt mode, the part can be
unconditionally set to monitor for an overtemperature condi-
May 2006
MIC184
Table 4. Fault_Queue Depth Settings
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11
tion, regardless of what caused the last temperature event.
This is done by clearing the MODE bit, and then immediately
resetting it to 1. Following this sequence the next temperature
event detected will be an overtemperature condition, regard-
less of whether the last temperature event was the result of
an overtemperature or undertemperature condition.
In both modes, the MIC184 will be responsive to overtem-
perature events upon power up.
Fault_Queue
A Fault_Queue (programmable digital filter) is provided in the
MIC184 to prevent false tripping due to thermal or electrical
noise. Two bits, CONFIG[4:3], set the depth of Fault_Queue.
Fault_Queue then determines the number of consecutive
temperature events (TEMP > T_SET or TEMP < T_HYST)
which must occur in order for the condition to be considered
valid. As an example, assume the MIC184 is in comparator
mode, and CONFIG[4:3] is programmed with 10
measured temperature would have to exceed T_SET for four
consecutive A/D conversions before INT would be asserted
or the status bit set. Similarly, TEMP would have to be less
than T_HYST for four consecutive conversions before INT
would be reset.
Like any filter, the Fault_Queue function also has the effect of
delaying the detection of temperature events. In this example,
it would take 4 × t
depth of Fault_Queue vs. D[4:3] of the configuration register
is shown in Table 4.
Handling Interrupts
The MIC184 may be either polled by the host, or request the
host’s attention via the INT pin. In the case of polled opera-
tion, the host periodically reads the contents of CONFIG to
check the state of the status bit. The act of reading CONFIG
clears the status bit, STS. If more than one event that sets
the status bit occurs before the host polls the MIC184, only
the fact that at least one such event has occurred will be
apparent to the host.
If TEMP < T_HYST or TEMP > T_SET for Fault_Queue con-
versions, the status bit STS will be set in the CONFIG register.
This action cannot be masked. However, a temperature
event will only generate an interrupt signal on INT if inter-
rupts from the MIC184 are enabled (IM = 0 and MODE = 1
in the configuration register). Reading any register following
an interrupt will cause INT to be deasserted, and will clear
STS. The host should read the contents of the configuration
register after receiving an interrupt to confirm that the MIC184
was the source of the interrupt. This is shown in Figure 7.
As noted above, putting the device into shutdown mode will
also deassert INT and clear STS. Therefore, this usually
should not be done before completing the appropriate inter-
rupt service routine(s).
Since temperature-to-digital conversions continue while INT
is asserted, it is possible that temperature could change be-
tween the MIC184’s assertion of its INT output and the host’s
response to the interrupt. It is good practice when servicing
interrupts for the host to read the current temperature to confirm
that the condition that caused the interrupt still exists.
CONV
to detect a temperature event. The
b
. Then the
MIC184
Micrel