SNOSDH4 Data sheet

SNOSDH4 June 2024 TPS7H6005-SEP , TPS7H6015-SEP , TPS7H6025-SEP

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9.2.2.6 Gate Driver Losses

Gate drive devices such as the TPS7H6005 have several different components that comprise the power losses. The quiescent power losses P_QCcan be determined using Equation 21 :

Equation 21.

P_{Q C} = (V I N \times I_{Q L S}) + (V_{B O O T} \times I_{Q H S}) = (12 V \times 5 m A) + (10 V \times 4 m A) = 100 m W

where:

I_QLS is the low-side quiescent current (selected for PWM mode in this design)
I_QHS is the high-side quiescent current (selected for PWM mode in this design)
V_BOOT is the voltage at BOOT with respect to ASW

Leakage current power losses P_BG can be calculated using Equation 22:

Equation 22.

P_{B G} = V_{B G} \times I_{Q B G} \times D_{M A X} = 110 V \times 20 μ A \times 0.35 = 0.77 m W

where:

V_BG is the voltage between BOOT and AGND
I_QBG is the BOOT to AGND leakage current

There are losses that occur within the driver due to the charging and discharging of the GaN FET gate charge. To determine these, first calculate P_GATE as:

Equation 23.

P_{G A T E} = V_{B P 5 x} \times Q_{G} \times f_{S W} = 5 V \times 10.6 n C \times 500 k H z = 26.5 m W

This loss is actually distributed amongst the resistances in the gate driver loop, which includes the driver, the gate resistances and the GaN FET. The power dissipated within the TPS7H6005 for both turn-on and turn-off can be calculated:

Equation 24.

P_{D R V_O N_H S} = \frac{1}{2} \times \frac{R_{H O H} \times P_{G A T E}}{R_{H O H} + R_{G A T E} + R_{G F E T (i n t)}}

Equation 25.

P_{D R V_O F F_H S} = \frac{1}{2} \times \frac{R_{H O L} \times P_{G A T E}}{R_{H O L} + R_{G A T E} + R_{G F E T (i n t)}}

Equation 26.

P_{D R V_O N_L S} = \frac{1}{2} \times \frac{R_{L O H} \times P_{G A T E}}{R_{L O H} + R_{G A T E} + R_{G F E T (i n t)}}

Equation 27.

P_{D R V_O F F_L S} = \frac{1}{2} \times \frac{R_{L O L} \times P_{G A T E}}{R_{L O L} + R_{G A T E} + R_{G F E T (i n t)}}

In this instance, the high-side and low-side losses are the same:

Equation 28.

P_{D R V_O N_H S} = P_{D R V_O N_L S} = \frac{1}{2} \times \frac{R_{x O H} \times P_{G A T E}}{R_{x O H} + R_{G A T E} + R_{G F E T (i n t)}} = \frac{1}{2} \times \frac{1.3 Ω \times 26.5 m W}{1.3 Ω + 2 Ω + 0.4 Ω} = 4.7 m W

Equation 29.

P_{D R V_O F F_H S} = P_{D R V_O F F_L S} = \frac{1}{2} \times \frac{R_{x O L} \times P_{G A T E}}{R_{x O L} + R_{G A T E} + R_{G F E T (i n t)}} = \frac{1}{2} \times \frac{0.07 Ω \times 26.5 m W}{0.07 Ω + 2 Ω + 0.4 Ω} = 0.8 m W

Finally, the P_GATE losses within the driver can be found:

Equation 30.

P_{D R V_H S} = P_{D R V_O N_H S} + P_{D R V_O F F_H S} = 4.7 m W + 0.8 m W = 5.5 m W

Equation 31.

P_{D R V_L S} = P_{D R V_O N_L S} + P_{D R V_O F F_L S} = 4.7 m W + 0.8 m W = 5.5 m W

Equation 32.

P_{D R V} = P_{D R V_H S} + P_{D R V_L S} = 5.5 m W + 5.5 m W = 11 m W

There is also a component of power consumption associated with the operating current of the driver, which is specified at no-load and frequency dependent. These can be approximated using the operating current parameters in the Specifications section:

Equation 33.

P_{O P_P W M} = (V I N \times I_{O P_P W M_L S}) + (V_{B O O T} \times I_{O P_P W M_H S}) = (12 V \times 6 m A) + (10 V \times 5 m A) = 122 m W

where:

I_{OP_PWM_LS} is the low-side operating current (selected for PWM mode at 500kHz)
I_{OP_PWM_HS} is the high-side operating current (selected for PWM mode at 500kHz)