EMC1822 datasheet(29/103 Pages) MICROCHIP

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An out-of-limit condition (for example, HIGH, LOW, or FAULT) occurring on the same temperature

channel in consecutive measurements will increment the consecutive alert counter. The counters will also

be reset if no out-of-limit condition or Diode Fault condition occurs in a consecutive reading.

When the ALERT pin is configured as an interrupt and when the consecutive alert counter reaches its

programmed value, the following occurs: the Status bit(s) for that channel and the last error condition(s)

(for example, E1HIGH, or E2LOW and/or E2FAULT) are set to ‘1’, the ALERT pin is asserted, the

consecutive alert counter is cleared and measurements continue to be performed.

When the ALERT pin is configured as a comparator, the consecutive alert counter will ignore Diode Fault

and low limit errors and only increment if the measured temperature exceeds the high limit. Additionally,

once the consecutive alert counter reaches the programmed limit, the ALERT pin is asserted, but the

counter does not reset. It remains set until the temperature drops below the high limit minus the Therm

Hysteresis value.

Channels that are not enabled are not included in the consecutive alert checking. The signal logic chain

is: Limit → Counter → Status → Mask → Pin (THERM and ALERT).

For example, if the CALRT<2:0> bits are set for four consecutive alerts on an EMC1822/23/24/25/43

device, the high limits are set at +70°C and none of the channels are masked, then the ALERT pin is

asserted after the following five measurements:

•

Internal Diode reads +71°C and both the external diodes read +69°C. Consecutive alert counter for

INT is incremented to 1.

•

Both the Internal Diode and the External Diode 1 read +71°C and External Diode 2 reads +68°C.

Consecutive alert counter for INT is incremented to 2 and for EXT1 is set to 1.

•

The External Diode 1 reads +71°C and both Internal Diode and External Diode 2 read +69°C.

Consecutive alert counters for INT and EXT2 are cleared and EXT1 is incremented to 2.

•

The Internal Diode reads +71°C and both external diodes read +71°C. Consecutive alert counter for

INT is set to 1, EXT2 is set to 1 and EXT1 is incremented to 3.

•

The Internal Diode reads +71°C and both external diodes read +71°C. Consecutive alert counter for

INT is incremented to 2, EXT2 is set to 2 and EXT1 is incremented to 4. The appropriate Status bits

are set for EXT and the ALERT pin is asserted. EXT1 counter is reset to 0 and all other counters

hold the last value until the next temperature measurement.

All temperature channels use this value to set the respective counters. The consecutive Therm counter is

incremented whenever any measurement exceeds the corresponding Therm limit.

If the temperature drops below the Therm limit, the counter is reset. If a number of consecutive

measurements above the Therm limit occurs, the THERM pin is asserted low.

Once the THERM pin has been asserted, the consecutive Therm counter will not reset until the

corresponding temperature drops below the Therm limit minus the Therm Hysteresis value.

The bits are decoded as shown in the table below. The default setting is four consecutive out-of-limit

conversions.

All temperature channels use this value to set the respective counters. The bits are decoded as shown in

the table below. The default setting is 1 consecutive out-of-limit conversion.

When the ALERT pin is in Comparator mode, the low limit and Diode Fault will bypass the consecutive

alert counter and set the appropriate Status bits, but will NOT assert the ALERT pin.

When a value is written to 8.11.23 CONSEC ALERT (Address 22h) that is not defined below, the

command is ignored and the last valid value is maintained.

Multi-Channel Low Voltage Temp Sens...

System Block Diagram

Datasheet

DS20006048A-page 29

EMC1822 Datasheet(PDF) 29 Page - Microchip Technology

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