参数资料
型号: MIC4451BM TR
厂商: Micrel Inc
文件页数: 8/13页
文件大小: 0K
描述: IC DRIVER MOSFET 12A HS 8-SOIC
标准包装: 2,500
配置: 低端
输入类型: 反相
延迟时间: 15ns
电流 - 峰: 12A
配置数: 1
输出数: 1
电源电压: 4.5 V ~ 18 V
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 8-SOIC(0.154",3.90mm 宽)
供应商设备封装: 8-SOIC
包装: 带卷 (TR)
其它名称: MIC4451BMTR
MIC4451BMTR-ND
(such as AVX RAM GUARD ), provides adequate
Micrel Inc.
Applications Information
Supply Bypassing
Charging and discharging large capacitive loads quickly
requires large currents. For example, changing a
10,000pF load to 18V in 50ns requires 3.6A.
The MIC4451/4452 has double bonding on the supply
pins, the ground pins and output pins. This reduces
parasitic lead inductance. Low inductance enables large
currents to be switched rapidly. It also reduces internal
ringing that can cause voltage breakdown when the
driver is operated at or near the maximum rated voltage.
Internal ringing can also cause output oscillation due to
feedback. This feedback is added to the input signal
since it is referenced to the same ground.
To guarantee low supply impedance over a wide
frequency range, a parallel capacitor combination is
recommended for supply bypassing. Low inductance
ceramic disk capacitors with short lead lengths (< 0.5
inch) should be used. A 1μF low ESR film capacitor in
parallel with two 0.1μF low ESR ceramic capacitors,
?
bypassing. Connect one ceramic capacitor directly
between pins 1 and 4. Connect the second ceramic
capacitor directly between pins 8 and 5.
Grounding
The high current capability of the MIC4451/4452
demands careful PC board layout for best performance.
Since the MIC4451 is an inverting driver, any ground
lead impedance will appear as negative feedback which
can degrade switching speed. Feedback is especially
noticeable with slow-rise time inputs. The MIC4451 input
structure includes 200mV of hysteresis to ensure clean
transitions and freedom from oscillation, but attention to
layout is still recommended.
Figure 4 shows the feedback effect in detail. As the
MIC4451 input begins to go positive, the output goes
negative and several amperes of current flow in the
ground lead. As little as 0.05 ? of PC trace resistance
can produce hundreds of millivolts at the MIC4451
ground pins. If the driving logic is referenced to power
ground, the effective logic input level is reduced and
oscillation may result.
To insure optimum performance, separate ground traces
should be provided for the logic and power connections.
Connecting the logic ground directly to the MIC4451
GND pins will ensure full logic drive to the input and
ensure fast output switching. Both of the MIC4451 GND
pins should, however, still be connected to power
ground.
MIC4451/4452
Input Stage
The input voltage level of the MIC4451 changes the
quiescent supply current. The N channel MOSFET input
stage transistor drives a 320μA current source load. With
a logic “1” input, the maximum quiescent supply current
is 400μA. Logic “0” input level signals reduce quiescent
current to 80μA typical.
The MIC4451/4452 input is designed to provide 200mV
of hysteresis. This provides clean transitions, reduces
noise sensitivity, and minimizes output stage current
spiking when changing states. Input voltage threshold
level is approximately 1.5V, making the device TTL
compatible over the full temperature and operating
supply voltage ranges. Input current is less than ±10μA.
The MIC4451 can be directly driven by the TL494,
SG1526/1527, SG1524, TSC170, MIC38C42, and
similar switch mode power supply integrated circuits. By
offloading the power-driving duties to the MIC4451/4452,
the power supply controller can operate at lower
dissipation. This can improve performance and reliability.
The input can be greater than the V S supply, however,
current will flow into the input lead. The input currents
can be as high as 30mA p-p (6.4mA RMS ) with the input.
No damage will occur to MIC4451/4452 however, and it
will not latch.
The input appears as a 7pF capacitance and does not
change even if the input is driven from an AC source.
While the device will operate and no damage will occur
up to 25V below the negative rail, input current will
increase up to 1mA/V due to the clamping action of the
input, ESD diode, and 1k ? resistor.
Power Dissipation
CMOS circuits usually permit the user to ignore power
dissipation. Logic families such as 4000 and 74C have
outputs which can only supply a few milliamperes of
current, and even shorting outputs to ground will not
force enough current to destroy the device. The
MIC4451/4452 on the other hand, can source or sink
several amperes and drive large capacitive loads at high
frequency. The package power dissipation limit can
easily be exceeded. Therefore, some attention should be
given to power dissipation when driving low impedance
loads and/or operating at high frequency.
October 2011
8
M9999-103111-B
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