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| 型號： | SI3232DCX-EVB |
| 廠商： | Silicon Laboratories Inc |
| 文件頁數(shù)： | 57/128頁 |
| 文件大?。?/td> | 0K |
| 描述： | DAUGHTER CARD W/DISCRETE INTRFC |
| 標準包裝： | 1 |
| 系列： | ProSLIC® |
| 主要目的： | 接口，模擬前端（AFE） |
| 已用 IC / 零件： | Si3232 |
| 已供物品： | 板，CD |
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Si3232
34
Preliminary Rev. 0.96
Not
Recommended
fo
r N
ew
D
esi
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4.5.2. Ground Key Detection
Ground key detection detects an alerting signal from the
terminal equipment during the tip open or ring open
linefeed states. The functional blocks required to
implement a ground key detector are shown in
Figure 15, and the register set for detecting a ground
key event is provided in Table 22 on page 36. The
primary input to the system is the longitudinal current
sense value provided by the voltage/current/power
monitoring circuitry and reported in the ILONG RAM
address. The ILONG value is produced in the ISP
provided the LFS bits in the linefeed register indicate
the device is in the tip open or ring open state.
The longitudinal current (ILONG) is computed as shown
in the following equation. Refer to Figure 11 on page 26
for the transistor references used in the equation (Q1,
Q2,
Q5
and
Q6
–
note
that
the
Si3200
has
corresponding MOS transistors). The same ILONG
equation applies to the discrete bipolar linefeed as well
as the Si3200 linefeed device.
The output of the ISP (ILONG) is the input to a
programmable, digital low-pass filter, which removes
unwanted ac signal components before threshold
detection.
The low-pass filter coefficient is calculated using the
following equation and is entered into the LONGLPF
RAM location:
Where f = 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 the
programmable threshold, LONGHITH. Hysteresis is
enabled
by
programming
a
second
threshold,
LONGLOTH, to detect when the ground key is released.
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, LONGDBI. If the debounce
interval is satisfied, the LONGHI bit is set to indicate
that a valid ground key event has occurred.
When the Si3220/25 detects a ground key event, the
linefeed automatically transitions from the TIP-OPEN
(or RING-OPEN) state to the FORWARD-ACTIVE (or
REVERSE-ACTIVE) state. However, this automatic
state transition is triggered by the LCR bit becoming
active (i.e., =1), and not by the LONGHI bit.
While ILONG is used to generate the LONGHI status bit,
a transition from TIP-OPEN to the FORWARD-ACTIVE
state (or from the RING-OPEN to the REVERSE-
ACTIVE state) occurs when the RING terminal (or TIP
terminal) is grounded and is based on the LCR bit and
implicitly on exceeding the LCROFFHK threshold.
As an example of ground key detection, suppose that
the Si3220/25 has been programmed with the current
values shown in Table 20.
ILONG, LCR, LONGHI, and CMHIGH is as shown in
Table 21. The entries under “Loop State” indicate the
condition of the loop, as determined by the equipment
terminating the loop. The entries under “LINEFEED
Setting” indicate the state initially selected by the host
CPU (e.g., TIP-OPEN) and the automatic transition to
the FORWARD-ACTIVE state due to a ground key
event (when RING is connected to GND). The transition
from state #2 to state #3 in Table 21 is the automatic
transition from TIP-OPEN to FWD-ACTIVE in response
to LCR = 1.
I
LONG
I
Q1
I
Q6
–
I
Q5
–
I
Q2
+
2
----------------------------------------------------
=
LONGLPF
2
f 4096
800
---------------------------------
2
3
=
Table 20. Settings for Ground Key Example
ILIM
21 mA
LCROFFHK
14 mA
LCRONHK
10 mA
LONGHITH
7 mA
LONGLOTH
5 mA
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| SI3232-FQ | 功能描述:電信線路管理 IC DUAL CH SLIC RoHS:否 制造商:STMicroelectronics 產(chǎn)品:PHY 接口類型:UART 電源電壓-最大:18 V 電源電壓-最小:8 V 電源電流:30 mA 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 安裝風格:SMD/SMT 封裝 / 箱體:VFQFPN-48 封裝:Tray |
| SI3232-FQR | 制造商:Silicon Laboratories Inc 功能描述: |
| SI3232-G-FQ | 功能描述:電信線路管理 IC Dual-Channel SLIC RoHS:否 制造商:STMicroelectronics 產(chǎn)品:PHY 接口類型:UART 電源電壓-最大:18 V 電源電壓-最小:8 V 電源電流:30 mA 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 安裝風格:SMD/SMT 封裝 / 箱體:VFQFPN-48 封裝:Tray |
| SI3232-G-FQR | 功能描述:電信線路管理 IC Dual-CH SLIC only Internal 65 Vrms RoHS:否 制造商:STMicroelectronics 產(chǎn)品:PHY 接口類型:UART 電源電壓-最大:18 V 電源電壓-最小:8 V 電源電流:30 mA 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 安裝風格:SMD/SMT 封裝 / 箱體:VFQFPN-48 封裝:Tray |
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