EMC1187 datasheet(36/47 Pages) MICROCHIP

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Triple Channel 1°C Temperature Sensor with Hardware Thermal Shutdown and 1.8V SMBus Communications

Datasheet

Revision 1.0 (07-11-13)

SMSC EMC1187

DATASHEET

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 will be

asserted, but the counter will not be reset. It will remain set until the temperature drops below the High

Limit minus the Therm Hysteresis value.

For example, if the CALRT[2:0] bits are set for 4 consecutive alerts on an EMC1187 device, the high

limits are set at 70°C, and none of the channels are masked, the ALERT pin will be asserted after the

following four measurements:

1. Internal Diode reads 71°C and external diodes read 69°C. Consecutive alert counter for INT is

incremented to 1.

2. Both the Internal Diode and External Diode1 read 71°C and External Diode 2 reads 68°C.

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

3. The External Diode1 reads 71°C and both the Internal Diode and External Diode 2 read 69°C.

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

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

is set to 1EXT2 is set to 1, and EXT is incremented to 3.

5. The Internal Diode reads 71°C and both the external diode read 71°C. Consecutive alert counter

for INT is incremented to 2EXT2 is set to 2, and EXT is incremented to 4. The appropriate status

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

hold the last value until the next temperature measurement.

Bit 7 - TIMEOUT - Determines whether the SMBus Timeout function is enabled.



‘0’ (default) - The SMBus Timeout feature is disabled. The SMCLK line can be held low indefinitely

without the device resetting its SMBus protocol.



‘1’ - The SMBus Timeout feature is enabled. If the SMCLK line is held low for more than tTIMEOUT,

the device will reset the SMBus protocol.

Bits 6-4 CTHRM[2:0] - Determines the number of consecutive measurements that must exceed the

corresponding Therm Limit and Hardware Thermal Shutdown Limit before the SYS_SHDN pin is

asserted. All temperature channels use this value to set the respective counters. The consecutive

THERM counter is incremented whenever any of the measurements exceed the corresponding Therm

Limit or if the External Diode 1 measurement exceeds the Hardware Thermal Shutdown Limit.

If the temperature drops below the Therm Limit or Hardware Thermal Shutdown Limit, the counter is

reset. If the programmed number of consecutive measurements exceed the Therm Limit or Hardware

Thermal Shutdown Limit, and the appropriate channel is linked to the SYS_SHDN pin, the SYS_SHDN

pin will be asserted low.

Once the SYS_SHDN pin is asserted, the consecutive Therm counter will not reset until the

corresponding temperature drops below the appropriate limit minus the corresponding hysteresis.

The bits are decoded as shown in Table 6.15. The default setting is 4 consecutive out of limit

conversions.

Bits 3-1 - CALRT[2:0] - Determine the number of consecutive measurements that must have an out of

limit condition or diode fault before the ALERT pin is asserted. temperature channels use this value

to set the respective counters. The bits are decoded as shown in Table 6.15. The default setting is 1

consecutive out of limit conversion.

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