LM5100 National Semiconductor, LM5100 Datasheet - Page 10

• Manufacturer Part Number: LM5100
• Description: High Voltage High Side and Low Side Gate Driver
• Manufacturer: National Semiconductor

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Power Dissipation Considerations
The bootstrap diode power loss is the sum of the forward
bias power loss that occurs while charging the bootstrap
capacitor and the reverse bias power loss that occurs during
reverse recovery. Since each of these events happens once
per cycle, the diode power loss is proportional to frequency.
Larger capacitive loads require more current to recharge the
bootstrap capacitor resulting in more losses. Higher input
voltages (V
recovery losses. The following plot was generated based on
calculations and lab measurements of the diode recovery
time and current under several operating conditions. This
can be useful for approximating the diode power dissipation.
(Continued)
Diode Power Dissipation V
IN
) to the half bridge result in higher reverse
FIGURE 4. LM5101 Driving MOSFETs Connected in Half-Bridge Configuration
IN
= 80V
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The total IC power dissipation can be estimated from the
previous plots by summing the gate drive losses with the
bootstrap diode losses for the intended application. Because
the diode losses can be significant, an external diode placed
in parallel (refer to Figure 4) with the internal bootstrap diode
can be helpful in removing power from the IC. For this to be
effective, the external diode must be placed close to the IC to
minimize series inductance and have a significantly lower
forward voltage drop than the internal diode.
Diode Power Dissipation V
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IN
= 40V
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