SI3232-BQ Silicon Laboratories Inc, SI3232-BQ Datasheet - Page 32

• Manufacturer Part Number: SI3232-BQ
• Description: IC SLIC PROG DUAL-CH 64TQFP
• Manufacturer: Silicon Laboratories Inc

Specifications of SI3232-BQ

• Package / Case: *
• Function: Subscriber Line Interface Concept (SLIC)
• Interface: ISDN
• Number Of Circuits: 2
• Voltage - Supply: 3.13 V ~ 3.47 V
• Current - Supply: 28mA
• Power (watts): 280mW
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Product: SLIC
• Supply Voltage (min): 3.13 V
• Supply Current: 28 mA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Number Of Channels: 2
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Si3232
Loop Closure Detection
Loop closure detection is required to accurately signal a
terminal device going off-hook during the Active or On-
Hook Transmission linefeed states (forward or reverse
polarity). The functional blocks required to implement a
loop closure detector are shown in Figure 14, and the
register set for detecting a loop closure event is
provided in Table 19. The primary input to the system is
the Loop Current Sense value provided by the voltage/
current/power monitoring circuitry and reported in the
ILOOP RAM address. The ILOOP value is processed in
the input signal processor (ISP) provided the LFS bits in
the Linefeed register indicate the device is in an Active
or On-Hook Transmission state. The output of the Input
Signal Processor is the input to a programmable digital
low-pass filter, which can be used to remove unwanted
ac signal components before threshold detection.
The low-pass filter coefficient is calculated using the
following equation and is entered into the LCRLPF RAM
location.
LCRLPF = [(2
32
ILOOP
π
f x 4096)/800] x 2
Processor
Signal
Input
LFS
Component
R101
R102
R103
D1
Q1
Q2
Figure 14. Loop Closure Detection Circuitry
Table 18. 3-Battery Switching Components
3
LCRLPF
Digital
LPF
LCROFFHK
402 kΩ, 1/10 W, ±1%
10 kΩ, 1/10 W, ±5%
Loop Closure
Threshold
200 V, 200 mA
1/10 W, ±5%
100 V NPN
100 V PNP
Preliminary Rev. 0.95
Value
LCRONHK
+
–
Where f is the desired cutoff frequency of the filter.
The programmable range of the filter is from 0h (blocks
all signals) to 4000h (unfiltered). A typical value of 10
(0A10h) is sufficient to filter out any unwanted ac
artifacts while allowing the dc information to pass
through the filter.
The output of the low-pass filter is compared to a
programmable threshold, LCROFFHK. Hysteresis is
enabled
LCRONHK, to detect the loop going to an OPEN or on-
hook state. The threshold comparator output feeds a
programmable debounce filter. The output of the
debounce filter remains in its present state unless the
input remains in the opposite state for the entire period
of time programmed by the loop-closure debounce
interval, LCRDBI. There is also a loop-closure mask
interval, LCRMASK, that is used to mask transitions
caused when an internal ringing burst (no dc offset)
ends in the presence of a high REN load. If the
debounce interval has been satisfied, the LCR bit will be
set to indicate that a valid loop closure has occurred.
LCRMASK
Closure
Mask
Loop
2.4 kΩ for V
by
3.9 kΩ for V
CXT5401 or similar
CXT5551 or similar
IN4003 or similar
Debounce
LCRDBI
programming
Comments
Filter
DD
DD
= 3.3 V
= 5 V
LCR
Interrupt
LOOPE
Logic
a
second
LOOPS
threshold,