TLE6281G datasheet(10/15 Pages) INFINEON

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Data Sheet TLE 6281G

Data Sheet

Rev 2.3 2007-01-11

tors. This means, that the bootstrap capacitor needs a minimum charging time of about 1µs,

if the highside switch is operated in PWM mode (e.g. with 20kHz a maximum duty cycle of

96% can be reached). The exact value for the upper limit is given by the RC time formed by

the impedance of the internal bootstrap diode and the capacitor formed by the external Mos-

fet (CMosfet=QGate / VGS). The size of the bootstrap capacitor has to be adapted to the external

MOSFET the driver IC has to drive. Usually the bootstrap capacitor is about 10-20 times big-

ger than CMosfet. External components at the Vs Pin have to be considered, too.

The charge pump is active when the highside switch is “ON” and the voltage level at the SHx

is higher than 4V. Only under these conditions the bootstrap capacitor is charged by the

charge pump.

Estimation of power loss within the Driver IC

The power loss within the Driver IC is strongly dependent on the use of the driver and the

external components. Nevertheless a rough estimation of the worst case power loss is pos-

sible.

Worst case calculation is:

PLoss = (Qgate*n*const* fPWM + IVS(open))* VVs - PRGate

With:

PLoss = Power loss within the Driver IC

fPWM = Switching freqency

Qgate = Total gate charge of used MOSFETs at 10V VGS

= Number of switched MOSFETs

const = Constant considering some leakage current in the driver (about 1.2)

IVS(open) = Current consumption of driver without connected Mosfets during switching

VVS

= Voltage at Vs

PRGate = Power dissipation in the external gate resistors

This value can be reduced dramatically by usage of external gate resistors.

Conditions :

Junction temperature Tj = 25

Number of switched MOSFET n = 2

Power dissipation in the external gate resistors PRGate = 0,2*PLoss

Estimated Power Loss PLOSS within the Driver IC

for different supply voltages Vs

at QG = 100nC @ VGS = 10V

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

203040

5060

PWM Frequency (kHz)

Vs = 8V

Vs = 14V

Vs = 18V

Estimated Power Loss PLOSS within the Driver IC

for different gate charges QG

at supply voltage Vs = 14V

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

102030

4050

PWM Frequency (kHz)

QG = 50nC

QG = 100nC

QG = 200nC

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