LM9061N National Semiconductor, LM9061N Datasheet - Page 6

• Manufacturer Part Number: LM9061N
• Description: Power MOSFET Driver with Lossless Protection
• Manufacturer: National Semiconductor

Figure 1 shows the basic application of the LM9061
Typical Electrical Characteristics
Application Hints
BASIC OPERATION
The LM9061 contains a charge pump circuit that generates
a voltage in excess of the applied supply voltage to provide
gate drive voltage to power MOSFET transistors Any size
of N-channel power MOSFET including multiple parallel
connected MOSFETs for very high current applications can
be used to apply power to a ground referenced load circuit
in what is referred to as ‘‘high side drive’’ applications
FIGURE 1 Basic Application Circuit
TL H 12317–8
Timing Definitions
(Continued)
6
When commanded ON by a logic ‘‘1’’ input to pin 7 the gate
drive output pin 4 rises quickly to the V
at pin 5 Once the gate voltage exceeds the gate-source
threshold voltage of the MOSFET V
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 contin-
ues 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
It is important to remember that during the Turn-ON of the
MOSFET the output current to the Gate is drawn from the
V
capacitor with a value of at least ten times the Gate capaci-
tance and no less than 0 1 F The output current into the
Gate will typically be 30 mA with V
0V As the Gate voltage rises to V
decrease When the Gate voltage reaches V
current will typically be 1 mA with V
A logic ‘‘0’’ on pin 7 turns the MOSFET OFF When com-
manded OFF a 110
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
starts following the gate voltage and ramps toward ground
Eventually the source voltage equals 0V and the gate con-
tinues to ramp to zero thus turning OFF the power device
This gradual Turn-OFF characteristic instead of an abrupt
removal of the gate drive can in some applications mini-
mize 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
Protection Circuitry Section)
CC
GS(ON)
supply pin The V
threshold of the MOSFET the source voltage
GS
A current sink is connected to the
CC
to 15V
pin should be bypassed with a
CC
CC
CC
TL H 12317 – 07
at 14V and the Gate at
GS(ON)
the output current will
at 14V
CC
supply potential
CC
(the source is
the output
A (see