September 2005
14
M9999-083005
MIC2588/MIC2594
Micrel
Applications Information
Optional External Circuits for Added Protection/Perfor-
mance
In many telecom applications, it is very common for circuit
boards to encounter large-scale supply-voltage transients
in backplane environments. Because backplanes present a
complex impedance environment, these transients can be
as high as 2.5 times steady-state levels, or 120V in worst-
case situations. In addition, a sudden load dump anywhere
on the circuit card can generate a very high voltage spike
at the drain of the output MOSFET which, in turn, will ap-
pear at the DRAIN pin of the MIC2588/MIC2594. In both
cases, it is good engineering practice to include protective
measures to avoid damaging sensitive ICs or the hot swap
controller from these large-scale transients. Two typical
scenarios in which large-scale transients occur are de-
scribed below:
1. An output current load dump with no bypass (charge
bucket or bulk) capacitance to V
EE
. For example,
if L
LOAD
= 5礖, V
IN
= 56V and t
OFF
= 0.7祍, the
resulting peak short-circuit current prior to the
MOSFET turning off would reach:
56V 0.7 s
5 H
7.8A
?nbsp m
(
)
m
=
If there is no other path for this current to take
when the MOSFET turns off, it will avalanche the
drain-source junction of the MOSFET. Since the
total energy represented is small relative to the
sturdiness of modern power MOSFETs, its unlikely
that this will damage the transistor. However, the
actual avalanche voltage is unknown; all that can
be guaranteed is that it will be greater than the
V
BD(D-S)
of the MOSFET. The drain of the transistor
is connected to the DRAIN pin of the MIC2588/
MIC2594, and the resulting transient does have
enough voltage and energy to damage this, or any,
high-voltage hot swap controller.
2. If the loads bypass capacitance (for example,
the input lter capacitors for DC-DC converter
module(s)) are on a board from which the board
with the MIC2588/MIC2594 and the MOSFET can
be unplugged, the same type of inductive transient
damage can occur to the MIC2588/MIC2594.
For many applications, the use of additional circuit compo-
nents can be implemented for optimum system performance
and/or protection. The circuit, shown in Figure 6, includes
several components to address some the following system
(dynamic) responses and/or functions: 1) suppression of
transient voltage spikes, 2) elimination of false tripping of the
circuit breaker due to undervoltage and overcurrent glitches,
and 3) the implementation of an external reset circuit.
It is not mandatory that these techniques be utilized, how-
ever, the application environment will dictate suitability. For
protection against sudden on-card load dumps at the DRAIN
pin of the MIC2588/MIC2594 controller, a 68V, 1W, 5% Zener
diode clamp (D2) connected from the DRAIN to the VEE of
the controller can be implemented, as shown. To protect
the controller from large-scale transients at the card input,
a 100V clamp diode (D1, SMAT70A or equivalent) can be
used. In either case, very short lead lengths and compact
layout design is strongly recommended to prevent unwanted
transients in the protection circuitry. Power buss inductance
often produces localized (plug-in card) high-voltage transients
during a turn-off event. Managing these repeated voltage
stresses with sufcient input bulk capacitance and/or tran-
sient suppressing diode clamps is highly recommended for
maximizing the life of the hot swap controller(s).
/PWRGD
DRAIN
UV
OV
VDD
SENSE
GATE
VEE
1
8
7
6
5
4
3
2
R1
698k&
1%
R3
12.4k&
1%
R2
11.8k&
1%
C1
0.47礔
*C6
0.47uF
*R5
47k&
*D1
100V
M1
SUM110N10-09
C3
0.33uF
R4
10&
-48V
OUT
-48V RTN
C5
47uF
C4
0.1uF
-48V
IN
-48V RTN
C2
0.22uF
MIC2588-2BM
*R6
2.7k&
System
Reset
R
SENSE
0.01&
5%
*M2
RFDBK
10k&
C
FDBK
10nF
100V
*R7
10k&
* Optional components (See Applications Information for more details)
An SOT-363 is recommended for M2.
D2 is a 68V, 1W Zener diode.
D2 is
*D2
68V
Figure 6 Optional Components for Added Performance/Protection
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相关代理商/技术参数
MIC2594-2YM
功能描述:热插拔功率分布 Negative Voltage Hot-Swap Controller - Lead Free
RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube
MIC2594-2YM TR
功能描述:热插拔功率分布 Negative Voltage Hot-Swap Controller - Lead Free
RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube
MIC2594-2YM-TR
功能描述:Hot Swap Controller 1 Channel -48V 8-SOIC 制造商:microchip technology 系列:- 包装:剪切带（CT） 零件状态:停产 类型:热交换控制器 通道数:1 内部开关:无 应用:-48V 特性:故障超时，闭锁故障 可编程特性:限流，压摆率，UVLO 电压 - 电源:-80 V ~ -19 V 电流 - 输出（最大值）:- 工作温度:-40°C ~ 85°C 电流 - 电源:3mA 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 供应商器件封装:8-SOIC 功能引脚:DRAIN，OFF，ON，/PWRGD 标准包装:1
MIC2595-1BM
功能描述:IC CTRLR HOT SWAP NEG HV 14-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Obsolescence Mitigation Program 标准包装:100 系列:- 类型:热插拔开关 应用:通用 内部开关:是 电流限制:可调 电源电压:9 V ~ 13.2 V 工作温度:-40°C ~ 150°C 安装类型:表面贴装 封装/外壳:10-WFDFN 裸露焊盘 供应商设备封装:10-TDFN-EP（3x3） 包装:管件
MIC2595-1BM TR
功能描述:IC CTRLR HOT SWAP NEG HV 14-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Obsolescence Mitigation Program 标准包装:100 系列:- 类型:热插拔开关 应用:通用 内部开关:是 电流限制:可调 电源电压:9 V ~ 13.2 V 工作温度:-40°C ~ 150°C 安装类型:表面贴装 封装/外壳:10-WFDFN 裸露焊盘 供应商设备封装:10-TDFN-EP（3x3） 包装:管件
MIC2595-1YM
功能描述:热插拔功率分布 Negative Voltage Hot-Swap Controller - Lead Free
RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube
MIC2595-1YM TR
功能描述:热插拔功率分布 Negative Voltage Hot-Swap Controller - Lead Free
RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube
MIC2595-1YM-TR
功能描述:Hot Swap Controller, Sequencer 1 Channel -48V 14-SOIC 制造商:microchip technology 系列:- 包装:剪切带（CT） 零件状态:停产 类型:热交换控制器，序列发生器 通道数:1 内部开关:无 应用:-48V 特性:闭锁故障 可编程特性:限流，故障超时，UVLO 电压 - 电源:-80 V ~ -19 V 电流 - 输出（最大值）:- 工作温度:-40°C ~ 85°C 电流 - 电源:4mA 安装类型:表面贴装 封装/外壳:14-SOIC（0.154"，3.90mm 宽） 供应商器件封装:14-SOIC 功能引脚:CFILTER，CNLD，DRAIN，PGTIMER，OFF，ON，PWRGD1，PWRGD2，PWRGD3 标准包装:1