Timing Definitions

TLH12317 – 07

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 shows the basic application of the LM9061

TLH12317 – 8

FIGURE 1 Basic Application Circuit

When commanded ON by a logic ‘‘1’’ input to pin 7 the gate

at pin 5 Once the gate voltage exceeds the gate-source

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

It is important to remember that during the Turn-ON of the

MOSFET the output current to the Gate is drawn from the

capacitor with a value of at least ten times the Gate capaci-

tance and no less than 01 mF The output current into the

A logic ‘‘0’’ on pin 7 turns the MOSFET OFF When com-

manded OFF a 110 mA 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

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 mA (see

Protection Circuitry Section)

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