MIC384-3BM Micrel Inc, MIC384-3BM Datasheet - Page 10

• Manufacturer Part Number: MIC384-3BM
• Description: IC SUPERVSR THERM LOC/REM 8SOIC
• Manufacturer: Micrel Inc

Specifications of MIC384-3BM

• Function: Temp Monitoring System (Sensor)
• Topology: ADC (Sigma Delta), Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -55°C ~ 125°C, External Sensor
• Output Type: I²C™/SMBus™
• 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)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

MIC384
Temperature Data Format
The LSB of each register represents one degree Centigrade.
The values are in a two’s complement format, wherein the
most significant bit (D7) represents the sign: zero for posi-
tive temperatures and one for negative temperatures. Table
3 shows examples of the data format used by the MIC384
for temperatures.
A/D Converter Timing
Whenever the MIC384 is not in its low power shutdown mode,
the internal A/D converter (ADC) attempts to make continuous
conversions unless interrupted by a bus transaction access-
ing the MIC384.
Upon powering up or coming out of shutdown mode, the ADC
will begin acquiring temperature data starting with the first
external zone, zone 1, then the second external zone, zone
2, and finally the internal zone, zone 0. Results for zone 1 will
be valid after t
another t
4 shows this behavior. The conversion time is twice as long
for external conversions as it is for internal conversions. This
allws the use of a filter capacitor on T1 and/or T2 without a
loss of accuracy due to the resulting longer settling times.
Upon powering up, coming out of shutdown mode, or resum-
ing operation following a serial bus transaction, the ADC will
begin aquiring temperature data with the first external zone
(zone 1), followed by the second external zone (zone 2), and
then the internal zone (zone 0). If the ADC in interrupted by a
serial bus transaction, it will restart the conversion that was
interrupted and then continue in the normal sequence. This
sequence will repeat indefinitely until the MIC384 is shut
down, powered off, or is interrupted by a serial bus transac-
tion as described above.
Power On
When power is initially applied, the MIC384’s internal registers
are set to their default states. Also at this time, the level on
the address input, A0, is read to establish the device’s slave
address. The MIC384’s power-up default state can be sum-
marized as follows:
MIC384
• Normal mode operation (i.e., part is not in shut-
• /INT function is set to comparator mode
• Fault queue depth = 1 (FQ=00)
• Interrupts are enabled (IM = 0)
• T_SET0 = 81°C; T_HYST0 = 76°C
• T_SET1 = 97°C; T_HYST1 = 92°C
• T_SET2 = 97°C; T_HYST2 = 92°C
• Initialized to recognize overtemperature faults
down)
CONV1
CONV1
, and for the local zone t
, results for zone two will be ready after
CONV0
later. Figure
10
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 when the measured temperature, as reported in any
of the TEMPx registers, exceeds the threshold programmed
into the corresponding T_SETx register for the number of
conversions specified by Fault_Queue (described below).
In comparator mode, /INT will remain asserted and the
status bit(s) will remain high unless and until the measured
temperature falls below the value in the T_HYSTx 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 a
status bit to be set and the /INT output to be asserted, they
will not be automatically de-asserted when the measured
temperature falls below T_HYSTx. They can only be de-as-
serted by reading any of the MIC384’s internal registers or
by putting the device into shutdown mode. If the most recent
temperature event was an overtemperature condition, Sx will
not be set again, and /INT cannot be reasserted, until the
device has detected that TEMPx < T_HYSTx. Similarly, if
the most recent temperature event was an undertemperature
condition, Sx will not be set again, and /INT cannot be reas-
serted, until the device has detected that TEMPx > T_SETx.
This keeps the internal logic of the MIC384 backward compat-
ible with that of the LM75 and similar devices. In both modes,
the MIC384 will be responsive to over-temperature events at
power-up. See "Interrupt Generation", below.
Shutdown Mode
Setting the SHDN bit in the configuration register halts the
otherwise continuous conversions by the A/D converter. The
MIC384’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
part’s power consumption.
Entering shutdown mode will not affect the state of /INT
when the device is in comparator mode (MODE = 0). It will
retain its state until after the device exits shutdown mode and
resumes A/D conversions.
However, if the device is shut down while in interrupt mode,
the /INT pin will be unconditionally de-asserted and the internal
latches holding the interrupt status will be cleared. There-
fore, no interrupts will be generated while the MIC384 is in
September 2005
Micrel