Description
6
SNVU637 – October 2018
Copyright © 2018, Texas Instruments Incorporated
Using the LMG3411EVM-029 Half-Bridge and LMG34XX-BB-EVM Breakout
Board EVM
2.1.3
Bootstrap Mode
The LMG3411EVM-029 card can be modified to operate in bootstrap mode, where the 12V bias voltage is
used to power both LMG3411R070 devices. This can be achieved by removing U4, U5 and R1, and
placing a 20
Ω
resistor on R2, a 0
Ω
resistor on R7 and a 600V SOD-123 diode on D1, such as Micro
Commercial Components UFM15PL-TP. Do NOT power up the LMG3411EVM-029 when R1, R2, R7, D1,
U4 and U5 are all populated.
2.1.4
Heat Sink
Heat sink is installed to help with heat dissipation of the LMG3411R070. Exposed copper pads that are
attached to the die attach pad (DAP) of both the high and low side devices are provided for a low thermal
impedance point to a heat sink. The two copper pads have high voltage potential difference between them
so an electrically isolative thermal interface material (TIM) is required. Bergquist BP100-0.005-00-1112
double sided adhesive tape TIM and Cool Innovations 3-101004U heat sink are recommended.
Figure 2. Front and Back Side Photos of LMG3411EVM-029
2.2
LMG34XX-BB-EVM
To allow for quick operation the LMG34XX-BB-EVM is available to interface with the LMG3411EVM-029.
This mother board is designed to operate the LMG3411R070 as a synchronous open loop buck converter.
Easy probe locations are provided for measurement of logic and power stage voltages.
2.2.1
Bias Supply
The motherboard requires one 12V bias supply. A linear drop off regulator steps the voltage down to a
tightly regulated 5V for logic and auxiliary power of the LMG3411R070 when the LMG3410-HB-EVM is
configured in isolated power mode. When the LMG3411EVM-029 is configured in bootstrap mode the 12V
input is used to power the two LMG3411R070 devices.
2.2.2
Logic PWM Input
The LMG34XX-BB-EVM supports a single PWM, with complimentary signal and corresponding dead time
generated on board. A 0 V to 5 V magnitude input square wave is required. The complementary PWM
generation circuit creates 50 ns of dead time between both transitions of the PWM signals.
