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参数资料
| 型号： | ISL5571AIBZ |
| 厂商： | INTERSIL CORP |
| 元件分类： | 通信及网络 |
| 英文描述： | Access High Voltage Switch |
| 中文描述： | SPECIALTY TELECOM CIRCUIT, PDSO16 |
| 封装： | LEAD FREE, PLASTIC, MS-013AA, SOIC-16 |
| 文件页数： | 10/12页 |
| 文件大小： | 190K |
| 代理商： | ISL5571AIBZ |
10
The DC current limiting response has a negative
temperature coefficient. As the temperature of the device
increases the DC current limit of the switch will decrease.
This is illustrated in Figure 4.
Figure 4 shows the V-I curves of a switch at two different die
temperatures, T1 and T2. In this illustration T2 is greater in
temperature than T1. This shows that when a switch is
driven into current limit and held there, the current limit will
decrease over time as the switch temperature increases. If
the power through the switch is great enough, the
temperature of the switch will continue to increase until the
switch goes into thermal shutdown (Thermal Shutdown is
described below).
Dynamic Current Limiting Response
The DC current limit response described above pertains to
DC and AC voltage sources applied across the switches.
The dynamic response is the response of the current limit
circuit to a fast or high dv/dt pulse. The dynamic response
would be seen, for example, during a lightning surge
Figure 5 shows the dynamic response that is observed when
SW1, SW2 or SW3 is surged with a 1000V at 10/1000
μ
s
telecom surge pulse. (Note: This surge test is done with the
switch in the on state and with the appropriate external
secondary protection in place.) The dynamic current limit of
SW1, SW2 or SW3 will limit the current through the switch to
less than 2.0A for 0.5
μ
s as shown in Figure 5. Once the
switch has turned off, the voltage at the T
Line
and R
Line
terminals will increase to a point where the external
secondary protection device will trigger and crowbar the
voltage at T
Line
and R
Line
to a low voltage, protecting the
ISL5571A against damage.
Since the Line Break switches (SW1, SW2) have this
dynamic current limit feature, the internal over-voltage
protection clamping circuit of the ISL5571A device will need
to only protect the SLIC against a 2.0A
≤
0.5
μ
s pulse during a
lightning surge.
Thermal Shutdown (TSD)
The ISL5571A has a built in thermal shutdown protection
circuit. The thermal shutdown protection mechanism is
invoked if a fault condition causes the junction temperature
of the die to exceed about 150°C
.
Once the thermal limit is
exceeded the thermal shutdown circuitry will force the
switches into an All OFF state, regardless of the logic inputs.
While in thermal shutdown the TSD logic pin (pin 11) will be
driven low by the thermal shutdown circuit. (Note: During
normal operation the TSD pin is high.) The thermal
shutdown mechanism was designed to have a thermal
hysteresis of about 12°C.
Once in thermal shutdown the
device will begin to cool down, because all the switches are
off and no current flows. When the temperature of the die
cools to about 138°C
the ISL5571A will cycle out of thermal
shutdown and the switches will close again. If the fault
condition is still present, the temperature of the die will again
increase and this cycle will be repeated.
Over Voltage Protection Clamping Circuit
The ISL5571A contains an over-voltage clamping circuit on
the SLIC side of the Line Break switches, see Figure 1. This
clamping circuit consists of a diode bridge and SCR. During
lightning surges and power-cross fault conditions this circuit
will clamp the voltage at the T
BAT
and R
BAT
terminals of the
SLIC to a safe level and will shunt harmful currents to
ground away from the SLIC.
The clamping circuit is externally connected to ground
through the F
GND
pin (pin 1) of the device. The battery
voltage of the SLIC is connected to the clamping circuit
through the V
BAT
pin (pin 16) of the device. The operation of
diode bridge and the SCR circuit is described below.
DIODE BRIDGE WITH SCR (ISL5571A)
During a positive lightning surge or during the positive cycle
of a power-cross / induction fault, the voltage at the T
BAT
and R
BAT
terminals of the SLIC will be clamped to a diode
drop above ground. The fault current will flow harmlessly
through diodes D1 and D2 of the diode bridge to ground (see
Figure 1).
During a negative lightning surge or during the negative
cycle of a power-cross / induction fault when the voltage at
the T
BAT
and R
BAT
terminals reach 2V to 4V more negative
than the V
BAT
voltage, the protection SCR will trigger and
turn on. When the SCR turns on and latches, it will crowbar
the voltage at the T
BAT
and R
BAT
lines to a low-voltage
state, approximately 3 diode drops below ground. This low-
voltage on state will cause the current resulting from the over
voltage to be safely direct to ground through diodes D3 and
D4 of the diode bridge and the SCR (see Figure 1). Once the
fault current decrease below the protection SCR holding
current (110mA) the SCR will turn off and the SLIC will be
able to return to normal operation.
V
BAT
Fault Circuit Protection - Loss of Battery
Voltage
The ISL5571A device contains a V
BAT
fault circuit which
monitors the SLIC battery voltage (V
BAT
). When this circuit
detects that the V
BAT
voltage has risen above -10V, it will
cause the ISL5571A to enter the All OFF state. All the
switches will remain off (open) until the circuit detects that
the SLIC battery voltage has dropped below -15V.
Design Considerations
External Protection
Subscriber line card circuits using the ISL5571A require the
use of an external protection circuit on the loop side or
phone side of the device, see Figure 1. This protection is
required to minimize the power stress on the ISL5571A
during overvoltage and overcurrent conditions. When the
proper external protection circuitry is used in conjunction
ISL5571A
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相关代理商/技术参数 |
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| ISL5571AIBZS2693 | 制造商:Intersil Corporation 功能描述:PB-FREE SUBSCRIBER LINE ACCESS SWITCH - Rail/Tube |
| ISL5571AIBZ-T | 功能描述:模拟开关 IC Pb-Free SUBSCRIBER LINE ACCESS SWITCH IN TAPE & REEL RoHS:否 制造商:Texas Instruments 开关数量:2 开关配置:SPDT 开启电阻（最大值）:0.1 Ohms 切换电压（最大）: 开启时间（最大值）: 关闭时间（最大值）: 工作电源电压:2.7 V to 4.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:DSBGA-16 |
| ISL5571AIBZ-TS2693 | 制造商:Intersil Corporation 功能描述:PB-FREE SUBSCRIBER LINE ACCESS SWITCH IN TAPE & REEL - Tape and Reel |
| ISL5585 | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:3.3V Ringing SLIC Family for Voice Over Broadband VOB |
| ISL5585_04 | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:3.3V Ringing SLIC Family for Voice Over Broadband (VOB) |
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