MAX78615-LMU View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

MAX78615-LMU

Isolated Energy Measurement Processor

Maxim Integrated 

MAX78615+LMU Data Sheet

Alarm Monitoring

Low-rate alarm conditions are determined every accumulation interval. If results for Die Temperature, AC

Frequency, or RMS Voltage exceeds or drops below user configurable thresholds, then a respective alarm bit in the

STATUS register is set. For RMS Current and Watts results, maximum thresholds are provided for detecting

overcurrent or overpower conditions with the load.

Register

T_MAX

T_MIN

F_MAX

F_MIN

VRMS_MAX

VRMS_MIN

IRMS_MAX

WATT_MAX

Description

Threshold value which Temperature must exceed to trigger alarm.

Threshold value which Temperature must drop below to trigger alarm.

Threshold value which Frequency must exceed to trigger alarm.

Threshold value which Frequency must drop below to trigger alarm.

Threshold value which RMS Voltage must exceed to trigger alarm.

Threshold value which RMS Voltage must drop below to trigger alarm.

Threshold value which RMS current must exceed to trigger alarm.

Threshold value which active power must exceed to trigger alarm.

Voltage Sag and Surge Detection

The MAX78615+LMU implements a voltage sag and surge detection function on both VA and VB. The sag/surge

detection function can generate an alarm when the line voltage drops below or exceeds the relevant

programmable thresholds. The firmware calculates on a sample-by-sample basis the trailing mean square of the

input voltage based on ½ line cycle interval according to the following equation:

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At each sample interval the VMS value is compared to a programmable threshold contained in the VSAG and

VSURGE registers. If VMS falls below or raises above the relevant thresholds, the firmware sets the relevant bits in

the Alarms register.

The sample count for sag detection is automatically adjusted by the firmware to maintain coverage over half of the

AC line cycle. Sag and surge detection is disabled by default and can be enabled by writing a nonzero value to the

VSAG/VSURGE registers. If the VSAG/VSURGE registers are set to 0, the sag/surge feature is disabled.

The sag detection can be used to monitor or record the quality of the power line or utilize the sag a pin to notify

external devices (for example a host microprocessor) of a pending power-down. The external device can then

enter a power-down mode (for example saving data or recording the event) before a power outage. Figure 21

shows a typical sag event.

Rev 0

34

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