SI3201-X-FS SILABS [Silicon Laboratories], SI3201-X-FS Datasheet - Page 21

• Manufacturer Part Number: SI3201-X-FS
• Manufacturer: SILABS [Silicon Laboratories]

2.2.5. Power Monitoring and Line Fault Detection
In addition to reporting voltages and currents, the
ProSLIC continuously monitors the power dissipated in
each linefeed transistor. Realtime 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 realtime 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 22 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).
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.
Power Alarm Threshold, Q1 & Q2
Power Alarm Threshold, Q3 & Q4
Power Alarm Threshold, Q5 & Q6
Power Alarm Interrupt Pending
Thermal LPF Pole, Q1 & Q2
Thermal LPF Pole, Q3 & Q4
Thermal LPF Pole, Q5 & Q6
Line Power Monitor Output
Power Monitor Pointer
Parameter
This
Table 22. Associated Power Monitoring and Power Fault Registers
feature
protects
spond to Q1 to Q6,
to Q6, respectively
0 to 5 points to Q1
0 to 7.8 W for Q1,
0 to 0.9 W for Q3,
Bits 2 to 7 corre-
Description/
respectively
the
Q2, Q5, Q6
0 to 7.8 W
0 to 0.9 W
0 to 7.8 W
Range
see equation above
see equation above
see equation above
Q4
Preliminary Rev. 0.5
external
The value of each thermal low-pass filter pole is set
according to the equation:
where τ 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 τ = 3 seconds
for SOT223 packages and τ = 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,
2Ah x 2
Note: The power monitor resolution for Q3 and Q4 is different
Resolution
30.4 mW
3.62 mW
30.4 mW
3.62 mW
30.4 mW
PT56[7:0]
N/A
N/A
from that of Q1, Q2, Q5, and Q6.
7
indirect
= 1500h.
Thermal LPF Pole [12:0]
=
where n = 1 to 6
------------------------------ -
Resolution
PWRMP[2:0]
PWROM[7:0]
Register 21
QnAP[n+1],
NQ12[12:0]
NQ34[12:0]
NQ56[12:0]
PPT12[7:0]
PPT34[7:0]
PPT56[7:0]
P
Register
MAX
Bits
=
----------------- -
0.0304
1.28
should
=
Indirect Register 19
Indirect Register 20
Indirect Register 21
Indirect Register 24
Indirect Register 25
Indirect Register 26
Direct Register 76
Direct Register 77
Direct Register 19
------------------
800 τ
4096
=
Si3233
Location*
42
×
be
=
2Ah
set
21
to