As a general rule, the local VGVDD bypass capacitor must be 10 times greater than the value of CBOOT, as shown

in Equation 6.

CGVDD = 1 µF

(6)

The bootstrap and bias capacitors must be ceramic types with X7R dielectric. The voltage rating must be twice

that of the maximum VGVDD considering capacitance tolerances once the devices have a DC bias voltage across

them and to ensure long-term reliability.

8.2.2.2 Select External Gate Driver Resistor

The external gate driver resistor, RGATE, is sized to reduce ringing caused by parasitic inductances and

capacitances and also to limit the current coming out of the gate driver.

The peak GH pullup current is calculated in Equation 7.

IGHH= VGVDD−VDH

RGHH+RGATE+RGFET_INT

(7)

where

• IGHH = GH Peak pullup current

• VDH = Bootstrap diode forward voltage drop

• RGHH = Gate driver internal GH pullup resistance, estimated from the testing conditions, that is RGHH =

VGH_H / IGH

• RGATE = External gate drive resistance

• RGFET_INT = MOSFET internal gate resistance, provided by transistor data sheet

Similarly, the peak GH pulldown current is shown in Equation 8.

IGHL= VGVDD−VDH

RGHL+RGATE+RGFET_INT

(8)

where

• RGHL is the GH pulldown resistance

The peak GL pullup current is shown in Equation 9.

IGLH= VGVDD

RGLH+RGATE+RGFET_INT

(9)

where

• RGLH is the GL pullup resistance

The peak GL pulldown current is shown in Equation 10.

IGLL= VGVDD

RGLL+RGATE+RGFET_INT

(10)

where

• RGLL is the GL pulldown resistance

For some scenarios, if the applications require fast turnoff, an anti-paralleled diode on RGate could be used to

bypass the external gate drive resistor and speed up turnoff transition.

8.2.2.3 Estimate the Driver Power Loss

The total driver IC power dissipation can be estimated through the following components.

1. Static power losses, PQC, due to quiescent currents IGVDD and IBST is shown in Equation 11.

LM2104

SNVSCH8A – SEPTEMBER 2023 – REVISED OCTOBER 2023

www.ti.com

16

Submit Document Feedback

Copyright © 2023 Texas Instruments Incorporated

Product Folder Links: LM2104