ia3211 integration, ia3211 Datasheet - Page 5

• Manufacturer Part Number: ia3211
• Description: Optical Silicon Daa Modem/lineside Chipset
• Manufacturer: integration

zener adapters will typically increase the answering machine
off-hook voltage to above 14 volts.
A solution to the voltage ambiguity problem is to design
firmware, which looks for a change in line voltage, or keeps a
history of line voltage to determine normal idle voltage. Then a
trip point can then be set about 30% below that idle level.
If the V/F function is not needed, the components connected to
pin 19 of the IA3211 and IA3212 can be left out. Note that the
V/F does not function when off-hook, or in SNOOP mode.
On-hook LIU Detection
The IA3211 provides a voltage to frequency converter allowing
the host processor to dynamically monitor the phone line
voltage. This function is specifically designed to provide a
reliable mean to detect line-in-use states (verification of the
status of the phone line prior to placing a call in order to
prevent line interruptions) and parallel pick-ups, also known as
line intrusion or 911 detection (attempt by a user or a device to
place a call on the same phone line). Upon detection of this
condition, most automated equipment would delay the call
attempt.
Off-hook Operation
The DAA is commanded to go off-hook by asserting either the
OFFHK, or the OFFHKL on the IA3211 This is transmitted to the
IA3212 via the TX analog opto-isolator.
The IA3212 immediately switches on the hook switch circuit.
The DAA will have an initial off -hook voltage about 2.2 volts
less than the steady state value for about 200ms. This low
voltage turn-on was designed to satisfy telephone regulations
in certain countries. It also is useful in forcing another
telephone device, such as an answering machine on the same
line, to release the line.
The AGC capacitor C2 sets this turn-on delay. The value can be
increased to get a longer turn on delay, but the settling time of
the DAA will also increase. C1 must also increase to maintain a
TIP
RING
F1250T
F1
HZ 0805 B 601R
HZ 0805 B 601R
L2
L1
-
D2
CBRHG-06
+
MMBT6520
SOT23
10
11
12
1
2
3
4
5
6
7
8
9
U1
HLDR
LEDCT
HLDCAP
HKP
HKN
N.C.1
HLFWV
LR1
LR2
N.C.2
N.C.3
C1A
Q1
IA3212
ONHKMCAP
C4
27nF
SRVCT
SRVAN
VFCAP
N.C.5
N.C.4
TXAN
TXCT
C1B
Vdd
Vss
C2
TN2540
SOT89
R4
56K
24
23
22
21
20
19
18
17
16
15
14
13
Q2
R9
3.9
C11
68nF
R11
20M
constant C1/C2 ratio (refer to the AGC description above). The
hook switch is a high voltage, low resistance DMOS transistor.
The gate voltage must be switched between the extreme
negative terminal of the diode bridge, and Vdd of the IA3212.
When off-hook, there may be a high voltage across the DMOS
transistor. The IA3212 cannot control such high voltages, so it
utilizes an external high voltage PNP transistor to switch the
gate. Both the DMOS and the PNP devices should be rated
above 250 volts.
The turn-on and turn-off transitions of the hook switch are
controlled by the RC network between the gate and source of
the FET The particular values of 27nF, and 56kΩ is a
compromise which can pass most telephone regulations for
"rotary" pulse dialing.
Pulse dialing and/or flash command is also achieved by
toggling the OFFHK (or OFFHKL) input.
Off-hook PPU Detection (911)
The IA3211 and IA3212 provide a built-in line voltage drop
detector that outputs a single positive pulse on the LSTAT pin
upon detection of a minimum of a 1V line voltage drop. This
voltage drop typically occurs when parallel equipment seizes
the line in order to attempt a call. Upon detection of this
condition, most automated equipment would release the line in
order to allow for possible emergency calls (911). The built-in
detector operates over the typical range of line conditions
(short and long) from 18mA to 100mA and effectively detects
any equipment presenting a DC load below 1kΩ under all those
line conditions. Most telecommunication equipments have a
DC load below 500Ω. This feature is combined with the off-
hook line polarity reversal detection and the controlling system
must discriminate between the two types of events.
Ring Detection
A 4ms wide positive pulse is generated on the RNG output of
the IA3211. Depending on the configuration of the HLFWV pin
of the IA3212 (line side device of the chipset), the pulse is
generated either once or twice for every incoming ring cycle.
TIP
RING
F1250T
F1
HZ 0805 B 601R
HZ 0805 B 601R
L2
L1
-
D2
CBRHG-06
+
MMBT6520
SOT23
10
11
12
1
2
3
4
5
6
7
8
9
U1
HLDR
LEDCT
HLDCAP
HKP
HKN
N.C.1
HLFWV
LR1
LR2
N.C.2
N.C.3
C1A
Q1
IA3211 & IA3212
IA3212
ONHKMCAP
C4
27nF
SRVAN
SRVCT
VFCAP
N.C.5
N.C.4
TXAN
TXCT
C1B
Vdd
Vss
C2
TN2540
SOT89
R4
56K
24
23
22
21
20
19
18
17
16
15
14
13
Q2
R9
3.9
5