LMG1205 Datasheet, PDF (15/24 Pages) Texas Instruments – 100-V, 1.2-A, 5-A, Half-Bridge Gate Driver for Enhancement Mode GaN FETs

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LMG1205
SNOSD37 – MARCH 2017
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. Because each of these
events happens once per cycle, the diode power loss is proportional to the operating frequency. Larger
capacitive loads require more energy to recharge the bootstrap capacitor resulting in more losses. Higher input
voltages (V_IN) to the half bridge also result in higher reverse recovery losses.
Figure 18 and Figure 19the forward bias power loss and the reverse bias power loss of the bootstrap diode
respectively. The plots are generated based on calculations and lab measurements of the diode reverse time and
current under several operating conditions. Figure 18 and Figure 19 can be used to predict the bootstrap diode
power loss under different operating conditions.
The load of high-side driver is a GaN FET with total gate charge of
10 nC.
Figure 18. Forward Bias Power Loss of
Bootstrap Diode V_IN = 50 V
The load of high-side driver is a GaN FET with total gate charge of
10 nC.
Figure 19. Reverse Recovery Power Loss of
Bootstrap Diode V_IN = 50 V
The sum of the driver loss and the bootstrap diode loss is the total power loss of the IC. For a given ambient
temperature, the maximum allowable power loss of the IC can be defined as Equation 5.
(T_J - T_A)
P = _TJA
(5)
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