Si3210/Si3211
Rev. 1.61
33
Not
Recommended
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2.1.5. Power Monitoring and Line Fault Detection
In addition to reporting voltages and currents, the ProSLIC continuously monitors the power dissipated in each
external bipolar transistor. Real-time output power of any one of the six linefeed transistors can be read by setting
the Power Monitor Pointer (direct Register 76) to point to the desired transistor and then reading the Line Power
Output Monitor (direct Register 77).
The real-time power measurements are low-pass filtered and compared to a maximum power threshold. Maximum
power thresholds and filter time constants are software-programmable and should be set for each transistor pair
based on the characteristics of the transistors used.
Table 25 describes the registers associated with this function.
If the power in any external transistor exceeds the programmed threshold, a power alarm event is triggered. The
ProSLIC sets the Power Alarm register bit, generates an interrupt (if enabled), and automatically enters the Open
state (if AOPN = 1). This feature protects the external transistors from fault conditions and, combined with the loop
voltage and current monitors, allows diagnosis of the type of fault condition present on the line.
The value of each thermal low-pass filter pole is set according to the equation:
where
is the thermal time constant of the transistor package, 4096 is the full range of the 12-bit register, and 800
is the sample rate in hertz. Generally
= 3 seconds for SOT223 packages and = 0.16 seconds for SOT23, but
check with the manufacturer for the package thermal constant of a specific device. For example, the power alarm
threshold and low-pass filter values for Q5 and Q6 using a SOT223 package transistor are computed as follows:
Thus, indirect Register 34 should be set to 150Dh.
Table 24. Measured Real-Time Linefeed Interface Characteristics
Parameter
Measurement
Range
Resolution
Register
Bits
Location*
Loop Voltage Sense (VTIP – VRING)
–94.5 to +94.5 V
1.5 V
LVSP,
LVS[6:0]
Direct Register 78
Loop Current Sense
–78.75 to +78.5 mA
1.25 mA
LCSP,
LCS[5:0]
Direct Register 79
TIP Voltage Sense
0 to –95.88 V
0.376 V
VTIP[7:0]
Direct Register 80
RING Voltage Sense
0 to –95.88 V
0.376 V
VRING[7:0]
Direct Register 81
Battery Voltage Sense 1 (VBAT)
0 to –95.88 V
0.376 V
VBATS1[7:0]
Direct Register 82
Battery Voltage Sense 2 (VBAT)
0 to –95.88 V
0.376 V
VBATS2[7:0]
Direct Register 83
Transistor 1 Current Sense
0 to 81.35 mA
0.319 mA
IQ1[7:0]
Direct Register 84
Transistor 2 Current Sense
0 to 81.35 mA
0.319 mA
IQ2[7:0]
Direct Register 85
Transistor 3 Current Sense
0 to 9.59 mA
37.6 A
IQ3[7:0]
Direct Register 86
Transistor 4 Current Sense
0 to 9.59 mA
37.6 A
IQ4[7:0]
Direct Register 87
Transistor 5 Current Sense
0 to 80.58 mA
0.316 mA
IQ5[7:0]
Direct Register 88
Transistor 6 Current Sense
0 to 80.58 mA
0.316 mA
IQ6[7:0]
Direct Register 89
*Note: The ProSLIC uses registers that are both directly and indirectly mapped.
A “direct” register is one that is mapped directly.
Thermal LPF register
4096
800
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2
3
=