EMC1812 datasheet(27/102 Pages) MICROCHIP

27 / 102 page

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 6.10.21 CONSEC ALERT (Address 22h) that is not defined below, the

command is ignored and the last valid value is maintained.

Table 5-9. Consecutive ALERT/ THERM Settings

Number of consecutive Out-of-Limit measurements

(default for CALRT<2:0>)

(default for CTHRM<2:0>)

5.18

“Hottest Of” Comparison

At the end of every measurement cycle, the EMC1812/13/14/15/33 devices compare all of the user-

selectable internal and external diode channels to determine which of these channels is reporting the

hottest temperature. The hottest temperature is stored in the Hottest Temperature registers and the

appropriate Status bit is set in the Hottest Status register. If multiple temperature channels measure the

same temperature and are equal to the hottest temperature, the hottest status will be displayed for all

selected temperature channels with the hottest temperature measurement.

As an optional feature, the EMC1812/13/14/15/33 devices can also flag an event if the hottest

temperature channel changes by enabling the REMHOT (Remember Hottest) bit (see 6.10.43 HOTTEST

CONFIG). For example, suppose that external diode channels 1, 3 and 4 are programmed to be

compared in the “Hottest Of” Comparison. If the External Diode 1 channel reports the hottest temperature

of the three, its temperature is copied into the Hottest Temperature registers (in addition to the External

Diode 1 Temperature registers) and it is flagged in the Hottest Status bit. If, on the next measurement, the

External Diode 3 channel temperature has increased such that it is now the hottest temperature, the

EMC1812/13/14/15/33 devices can flag this event as an interrupt condition and assert the ALERT pin.

5.19

Rate of Change

The Rate of Change (ROC) function approximates the derivative of the temperature using a difference

equation. The equation below is the basis for calculation.

The ROC can be enabled for the first two standard diode connections. If Diode 2 is an anti-parallel

connected diode, the ROC feature is applied to diode 3. For the EMC1833 the ROC only applies to

External Diode 1.

Multi-Channel Low-Voltage Remote Di...

System Block Diagram

Datasheet

DS20005751A-page 27

EMC1812 Datasheet(PDF) 27 Page - Microchip Technology