0.1

1.0

10.0

100.0

1000.0

SWITCHING FREQUENCY (kHz)

0.001

0.010

0.100

1.000

CL = 4400 pF

CL = 2200 pF

CL = 0 pF

CL = 470 pF

CL = 1000 pF

TEMPERATURE (

oC)

75

85

95

105

115

125

135

145

-50

-25

0

25

50

75

100 125 150

TDH

tP

TDH = tP + tRT1

tP

TDL

TDL = tP + tRT2

LI

HI

LO

HO

LM5102

www.ti.com

SNVS268B – MAY 2004 – REVISED DECEMBER 2014

8.2.3 Application Curves

Figure 17. Application Timing Waveforms

Figure 18. Turn On Delay vs Temperature

(RT = 10 k)

9 Power Supply Recommendations

9.1 Power Dissipation Considerations

The total IC power dissipation is the sum of the gate driver losses and the bootstrap diode losses. The gate

driver losses are related to the switching frequency (f), output load capacitance on LO and HO (CL), and supply

voltage (VDD) and can be roughly calculated as shown in Equation 12.

PDGATES = 2 × f × CL × VDD

2

(12)

There are some additional losses in the gate drivers due to the internal CMOS stages used to buffer the LO and

HO outputs. The following plot shows the measured gate driver power dissipation versus frequency and load

capacitance. At higher frequencies and load capacitance values, the power dissipation is dominated by the

power losses driving the output loads and agrees well with the above equation. This plot can be used to

approximate the power losses due to the gate drivers.

Figure 19. Gate Driver Power Dissipation (LO + HO)

VCC = 12 V, Neglecting Diode Losses

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 frequency. Larger capacitive loads

require more current to recharge the bootstrap capacitor resulting in more losses. Higher input voltages (VIN) to

the half bridge result in higher reverse recovery losses. Figure 20 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.

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