LM9061N National Semiconductor, LM9061N Datasheet - Page 10

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

Application Hints
To prevent this situation a delay capacitor is required at pin
8 The selection of a minimum capacitor value to ensure
proper start-up depends primarily on the load characteristics
and how much time is required for the MOSFET to raise the
load voltage to the point where the Sense input is more
positive than the Threshold input (T
mentation is required if a specific minimum delay time char-
acteristic is desired Therefore
In the absence of a specific delay time requirement a value
for C
OVER VOLTAGE PROTECTION
The LM9061 will remain operational with up to
V
LM9061 will turn off the MOSFET to protect the load from
excessive voltage When V
operating range the device will return to normal operation
without requiring toggling the ON OFF input This feature
will allow MOSFET operation to continue in applications that
are subject to periodic voltage transients such as automo-
tive applications
For circuits where the load is sensitive to high voltages the
circuit shown in Figure 5 can be used The addition of a
zener on the Sense input (pin 1) will provide a maximum
voltage reference for the Protection Comparator The Sense
resistor is required in this application to limit the zener cur-
rent When the device is ON and the load supply attempts
to rise higher than (V
comparator will trip and the Delay Timer will start If the high
supply voltage condition lasts long enough for the Delay
Timer to time out the MOSFET will be latched off The ON
OFF input will need to be toggled to restart the MOSFET
CC
DELAY
If V
FIGURE 5 Adding Over-Voltage Protection
CC
of 0 1 F is recommended
C
increases to more than typically
DELAY
ZENER
e
(I
DELAY c
a
CC
(Continued)
V
V
has returned to the normal
THRESHOLD
TIMER
START-UP
T
START-UP
) the Protection
) Some experi-
)
TL H 12317– 13
a
a
30V the
26V on
10
Figure 6 shows the LM9061 used as an electronic circuit
REVERSE BATTERY
The LM9061 is not protected against reverse polarity supply
connections If the V
with respect to ground the current from the V
be limited to 20 mA The addition of a diode in series with
the V
subtract significantly from the charge pump gate overdrive
output voltage
LOW BATTERY
As an additional protection feature the LM9061 incorporates
an Undervoltage Shut-OFF function If the V
package drops below 7V where it may not be assured that
the MOSFET is actually ON when it should be circuitry will
automatically turn OFF the power MOSFET
breaker This circuit provides low voltage shutdown over-
voltage latch OFF and overcurrent latch OFF In the event
of a latch OFF shutdown the circuit can be reset by shutting
the main supply off then back on An optional reset switch
on the ON OFF pin will allow a ‘‘push-button reset’’ of the
circuit after latching OFF
Scaling of the external resistor value from V
OFF input pin with the internal 30k resistor can be used to
increase the startup voltage The circuit operation then be-
comes dependent on the resistor ratio and V
ON OFF pin voltage being above the ON threshold rather
than the LM9061 low V
DRIVING MOSFET ARRAYS
The LM9061 is an ideal driver for any application that re-
quires multiple parallel MOSFETs to provide the necessary
load current Only a few ‘‘common sense’’ precautions need
to be observed All MOSFETs in the array must have identi-
cal electrical and thermal characteristics This can be
solved by using the same part number from the same
CC
input is recommended This diode drop does not
FIGURE 6 Electronic Circuit Breaker
CC
CC
supply should be taken negative
shutdown feature
CC
CC
CC
CC
supply to the
providing an
TL H 12317 – 14
to the ON
pin should