Si3220/Si3225
Table 21. Register and RAM Locations Used for Power Monitoring and Power Fault Detection
Register/
RAM
Register/RAM
Bits
Measurement
Range
Resolution
Parameter
Mnemonic
Si3200 Total Power Output Monitor
Si3200 Power Alarm Interrupt Pending
Si3200 Power Alarm Interrupt Enable
PSUM
IRQVEC3
IRQEN3
PTH12
PSUM[15:0]
PQ1S
0 to 34.72 W
N/A
1059.6 µW
N/A
PQ1E
N/A
N/A
Q1/Q2 Power Alarm Threshold (discrete)
Q1/Q2 Power Alarm Threshold (Si3200)
PTH12[15:0]
0 to 16.319 W
0 to 34.72 W
498 µW
1059.6 µW
Q3/Q4 Power Alarm Threshold
Q5/Q6 Power Alarm Threshold
Q1/Q2 Thermal LPF Pole
PTH34
PTH56
PTH34[15:0]
PTH56[15:0]
PLPF12[15:3]
PLPF34[15:3]
PLPF56[15:3]
PQ1S–PQ6S
PQ1E–PQ6E
0 to 1.03 W
31.4 µW
498 µW
0 to 16.319 W
PLPF12
PLPF34
PLPF56
IRQVEC3
IRQEN3
See “Power Filter and Alarms”
See “Power Filter and Alarms”
See “Power Filter and Alarms”
Q3/Q4 Thermal LPF Pole
Q5/Q6 Thermal LPF Pole
Q1–Q6 Power Alarm Interrupt Pending
Q1–Q6 Power Alarm Interrupt Enable
N/A
N/A
N/A
N/A
Power Dissipation Considerations
state, the on-hook loop feed is generated from the
ringing battery supply, generally –70 V or more. Once
the SLIC transitions to the off-hook state, a lower off-
hook battery supply (typically –24 V) supplies the
required current to power the loop if the loop length is
sufficiently short to accommodate the lower battery
supply. This battery switching method allows the SLIC
chipset to dissipate less power than when operating
from a –70 V battery supply. See “Automatic Dual
Battery Switching” for more details.
The Dual ProSLIC devices rely on the Si3200 to power
the line from the battery supply. The PCB layout and
enclosure conditions should be designed to allow
sufficient thermal dissipation out of the Si3200, and a
programmable power alarm threshold ensures product
safety under all operating conditions. See "Power
Monitoring and Power Fault Detection" on page 35 for
more details on power alarm considerations.
The Si3200’s thermally-enhanced SOIC-16 package
offers an exposed pad that improves thermal dissipation
out of the package when soldered to a topside PCB pad
connected to inner power planes. Using appropriate
layout practices, the Si3200 can provide thermal
performance of 55 °C/W. The exposed path should be
connected to a low-impedance ground plane via a
topside PCB pad directly under the part. See package
outlines for PCB pad dimensions. In addition, an
opposite-side PCB pad with multiple vias connecting it
to the topside pad directly under the exposed pad will
further improve the overall thermal performance of the
system. Refer to “AN55: Dual ProSLIC User Guide” for
optimal thermal dissipation layout guidelines.
In long loop applications, there is generally a single
battery supply (e.g., –48 V) available for powering the
loop in the off-hook state. When sourcing loop lengths
similar to the maximum specified service distance (e.g.,
18 kft.), most of the power is dissipated in the
impedance of the line. SLICs used in long-loop
applications must also be able to provide phone service
to customers who are located much closer to the line
card than the maximum loop length specified for the
system. This situation may cause substantial power to
be dissipated inside the SLIC chipset, often resulting in
thermal shutdown or destruction of the device due to
thermal runaway. A special power offload circuit is
recommended
for
single-battery
extended-loop
The Dual ProSLIC chipset is designed with the ability to
source long loop lengths in excess of 18 kft but can also
accommodate short loop configurations. For example,
the Si3220 can operate from one of two battery supplies
depending on the operating state. When in the on-hook
applications. Refer to “AN91: Si3200 Power Off-load
Circuit” for power offload circuit usage guidelines.
Rev. 1.0
39
SILICONIMAGE [ Silicon image ]
