Datasheet

71M6515H
Energy Meter IC
DATA SHEET
JULY 2011
Page: 47 of 60 © 2005−2011 Teridian Semiconductor Corporation 1.6
A Maxim Integrated Products Brand
Bits 31-16: These bits (SAGTHR) hold the voltage threshold that is to be applied for sag detection. The peak voltage must
exceed SAGTHR once each SAG_CNT samples in order to prevent a SAG warning. One LSB is defined as:
VMAXLSB
916
1028798.7
−
⋅⋅=
Example: A meter operating at 50Hz and 240V (RMS) is supposed to apply a sag threshold of 180V (RMS)
for at least four periods before a sag warning is issued. VMAX is 600V. Which values are to be selected for
SAG?
Four periods translate to T = 4 * 20ms = 80ms. This means that
SAG_CNT = T/397µs = 202.
180V (RMS) translate to 255V (peak), so SAGTHR is determined by
823
6001028798.7
255255
916
=
⋅⋅
==
−
LSB
SAGTHR
START_THRESHLD (0x40)
This register holds the voltage and current thresholds that apply to the calculation of frequency, zero crossings, voltage
phase and energy values. If the current is below the value stored in I_START, calculation of RMS current, and energy (Wh,
VARh and VAh) is suppressed.
Bits 15-0: These bits (I_START) hold the threshold to be applied for under-current. If ISQSUM< I_START, all post-
processed values are set to zero for that phase. This includes reported values for Wh, VARh, VAh, IRMS, VPHASE,
IPHASE, PULSER, PULSEW, PULSE3 and PULSE4. This applies only if CREEP_THRSLD is not set to zero. One LSB is
defined as:
hA
In
IMAX
LSB
213
2
104045.9
8_
−
⋅⋅=
Elements with ISQSUM< I_START will set the creep bits in the STATUS register.
Bits 31-16: These bits (V_START). hold the threshold to be applied for under-voltage. If VRMS<V_START, the values for
frequency (register FREQ_DELTA_T), zero crossings (register MAIN_EDGE_CNT), and voltage phase (register
V_PHASE_ABC) are set to zero. Additionally, if VRMS< V_START, the reported value of VRMS is set to zero. One LSB is
defined as:
hVVMAXLSB
213162
104045.92
−
⋅⋅⋅=
Elements with VRMS< V_START will not set the creep bits in the STATUS register.
VI_PTHRESHOLD (0x17)
This register holds the threshold for over-voltage and over-current alarms.
Bits 15-0: These bits (I_PTHRESHOLD) hold the threshold to applied for over-current alarm. The threshold comparison is
applied to the upper 16 bits of the values in IRMS: One LSB is defined as:
rmsA
CYCLESSUMIn
IMAX
LSB
_8_
1076.450
6−
⋅
=
Bits 31-16: These bits (V_PTHRESHOLD). hold the threshold to applied for over-voltage alarm. The threshold comparison
is applied to the upper 16 bits of the values in VRMS One LSB is defined as: