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參數(shù)資料
| 型號(hào)： | LM9061M |
| 英文描述： | SINGLE MOSFET DRIVER|BIPOLAR|SOP|8PIN|PLASTIC |
| 中文描述： | 單MOSFET驅(qū)動(dòng)器|雙極|?？苵 8引腳|塑料 |
| 文件頁(yè)數(shù)： | 7/15頁(yè) |
| 文件大?。?/td> | 336K |
| 代理商： | LM9061M |
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Application Hints
(Continued)
When commanded ON by a logic “1” input to pin 7 the gate
drive output, pin 4, rises quickly to the V
supply potential
at pin 5. Once the gate voltage exceeds the gate-source
threshold voltage of the MOSFET, V
, (the source is
connected to ground through the load) the MOSFET turns
ON and connects the supply voltage to the load. With the
source at near the supply potential, the charge pump con-
tinues to provide a gate voltage greater than the supply to
keep the MOSFET turned ON. To protect the gate of the
MOSFET, the output voltage of the LM9061 is clamped to
limit the maximum V
GS
to 15V.
It is important to remember that during the Turn-ON of the
MOSFET the output current to the Gate is drawn from the
V
CC
supply pin. The V
CC
pin should be bypassed with a
capacitor with a value of at least ten times the Gate capaci-
tance, and no less than 0.1 μF. The output current into the
Gate will typically be 30 mA with V
CC
at 14V and the Gate at
0V. As the Gate voltage rises to V
, the output current will
decrease. When the Gate voltage reaches V
CC
, the output
current will typically be 1 mA with V
CC
at 14V.
A logic “0” on pin 7 turns the MOSFET OFF. When com-
manded OFF a 110 μA current sink is connected to the
output pin. This current discharges the gate capacitances of
the MOSFET linearly. When the gate voltage equals the
source voltage (which is near the supply voltage) plus the
V
threshold of the MOSFET, the source voltage starts
following the gate voltage and ramps toward ground. Even-
tually the source voltage equals 0V and the gate continues to
ramp to zero thus turning OFF the power device. This
gradual Turn-OFF characteristic, instead of an abrupt re-
moval of the gate drive, can, in some applications, minimize
the power dissipation in the MOSFET or reduce the duration
of negative transients, as is the case when driving inductive
loads. In the event of an overstress condition on the power
device, the turn OFF characteristic is even more gradual as
the output sinking current is only 10 μA (see Protection
Circuitry Section).
TURN ON AND TURN OFF CHARACTERISTICS
The actual rate of change of the voltage applied to the gate
of the power device is directly dependent on the input ca-
pacitances of the MOSFET used. These times are important
to know if the power to the load is to be applied repetitively
as is the case with pulse width modulation drive. Of concern
are the capacitances from gate to drain, C
, and from gate
to source, C
. Figure 2 details the turn ON and turn OFF
intervals in a typical application. An inductive load is as-
sumed to illustrate the output transient voltage to be ex-
pected. At time t1, the ON/OFF input goes high. The output,
which drives the gate of the MOSFET, immediately pulls the
gate voltage towards the V
supply of the LM9061. The
source current from pin 4 is typically 30 mA which quickly
charges C
and C
. As soon as the gate reaches the
V
threshold of the MOSFET, the switch turns ON and
the source voltage starts rising towards V
. V
remains
equal to the threshold voltage until the source reaches V
.
While V
is constant only C
is charging. When the
source voltage reaches V
, at time t2, the charge pump
takes over the drive of the gate to ensure that the MOSFET
remains ON.
The charge pump is basically a small internal capacitor that
acquires and transfers charge to the output pin. The clock
rate is set internally at typically 300 kHz. In effect the charge
pump acts as a switched capacitor resistor (approximately
67k) connected to a voltage that is clamped at 13V above
the Sense input pin of the LM9061 which is equal to the V
CC
supply in typical applications. The gate voltage rises above
V
in an exponential fashion with a time constant depen-
dent upon the sum of C
and C
. At this time however the
load is fully energized. At time t3, the charge pump reaches
its maximum potential and the switch remains ON.
At time t4, the ON/OFF input goes low to turn OFF the
MOSFET and remove power from the load. At this time the
charge pump is disconnected and an internal 110 μA current
sink begins to discharge the gate input capacitances to
ground. The discharge rate (
V/
T) is equal to 110 μA/ (C
GD
+ C
GS
).
The load is still fully energized until time t5 when the gate
voltage has reached a potential of the source voltage (V
)
plus the V
threshold voltage of the MOSFET. Between
time t5 and t6, the V
voltage remains constant and the
source voltage follows the gate voltage. With the voltage on
C
held constant the discharge rate now becomes
110 μA/C
GD
.
At time t6 the source voltage reaches 0V. As the gate moves
below the V
threshold the MOSFET tries to turn OFF.
With an inductive load, if the current in the load has not
collapsed to zero by time t6, the action of the MOSFET
turning OFF will create a negative voltage transient (flyback)
across the load. The negative transient will be clamped to
V
GS(ON)
because the MOSFET must turn itself back ON to
continue conducting the load current until the energy in the
inductance has been dissipated (at time t7).
MOSFET PROTECTION CIRCUITRY
A unique feature of the LM9061 is the ability to sense exces-
sive power dissipation in the MOSFET and latch it OFF to
prevent permanent failure. Instead of sensing the actual
current flowing through the MOSFET to the load, which
typically requires a small valued power resistor in series with
01231708
FIGURE 1. Basic Application Circuit
L
www.national.com
7
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| LM9061M/NOPB | 功能描述:功率驅(qū)動(dòng)器IC High-Side Pwr Mosfet Driver RoHS:否 制造商:Micrel 產(chǎn)品:MOSFET Gate Drivers 類型:Low Cost High or Low Side MOSFET Driver 上升時(shí)間: 下降時(shí)間: 電源電壓-最大:30 V 電源電壓-最小:2.75 V 電源電流: 最大功率耗散: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
| LM9061M/NOPB | 制造商:Texas Instruments 功能描述:IC, MOSFET DRIVER, SOIC-8 |
| LM9061MX | 功能描述:功率驅(qū)動(dòng)器IC RoHS:否 制造商:Micrel 產(chǎn)品:MOSFET Gate Drivers 類型:Low Cost High or Low Side MOSFET Driver 上升時(shí)間: 下降時(shí)間: 電源電壓-最大:30 V 電源電壓-最小:2.75 V 電源電流: 最大功率耗散: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
| LM9061MX/NOPB | 功能描述:功率驅(qū)動(dòng)器IC RoHS:否 制造商:Micrel 產(chǎn)品:MOSFET Gate Drivers 類型:Low Cost High or Low Side MOSFET Driver 上升時(shí)間: 下降時(shí)間: 電源電壓-最大:30 V 電源電壓-最小:2.75 V 電源電流: 最大功率耗散: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Tube |
| LM9061N | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Power MOSFET Driver with Lossless Protection |
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