78M6610+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 over current or over power conditions with the load.
Register
T_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.
T_MIN
F_MAX
F_MIN
VRMS_MAX
VRMS_MIN
IRMS_MAX
WATT_MAX
Voltage Sag and Surge Detection
The 78M6610+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:
0
푓
ꢂꢃꢄꢅ
2
푉푀ꢁ =
×
�
푣ꢄ
2 × 푓
ꢆꢇꢈꢉꢂꢅ
ꢋ
2×ꢋ
ꢌꢍꢎꢏꢐꢑ
ꢄ= −ꢃꢄꢊ(
)
ꢐꢒꢓꢑ
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 rises 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. The following figure shows a typical sag event.
37
Rev 0
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
