MA5302MS datasheet(49/60 Pages) INFINEON

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Datasheet

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V 2.1

11/2/2023

Integrated Class D Amplifier

MA5302MS

13.2.2

Choosing Bootstrap Diode

Use a bootstrap charging diode with voltage rating of 1.5 x the maximum bus voltage. In order to charge the

bootstrap capacitor in a very short low-side ON period with a high PWM modulation ratio, a fast recovery diode

type with trr of <50ns and Ct of <10pF at 0V is recommended.

13.2.3

Charging VBS Prior to Start

For proper start-up, pre-charging the bootstrap supply VBS prior to PWM start-up is necessary for self-oscillating

PWM modulator topologies. A charging resistor, RCHARGE, inserted between the positive supply bus and VB, charges

CBS prior to switching start as shown in Figure 46. The minimum resistance of RCHARGE is limited by the maximum

PWM modulation index of the system. When the high-side MOSFET is on, RCHARGE drains the bootstrap power supply

together with the quiescent current, IQBS, so it reduces the holding time, resulting in maximum continuous high-side

on time.

The maximum resistance of RCHARGE is limited by the current charge capability of the resistor during startup.

Pre-charging current flows into the speaker load. In order to startup without the load connected, a dummy load

Rdummy in parallel with the speaker output provides a pre-charging current path.

Figure 46 Bootstrap Supply Pre-Charging

MA5302MS 데이터시트(PDF) 49 Page - Infineon Technologies AG