Bootstrap capacitor (Cbs) Precharging


Bootstrap capacitor (Cbs) Precharging

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Contributor V

Hi all,

I am referring MC9S12ZVM-Family RM.(Rev 2.13)

In the chapter Bootstrap Precharge

The below chunk of data : 


The bootstrap capacitors must be precharged before turning on the high-side drivers for the first time. This
can be done by using the PMF software output control mechanism:
PMFOUTC = 0x3F; // SW control on all outputs
PMFOUTB = 0x2A; // All high-sides off, all low-sides on
The PWM0 signals should be configured to start with turning on the low-side before the high-side drivers
in order to assure precharged bootstraps. Therefore invert the PWM0 signals:
PMFCINV = 0x3F; // Invert all channels to precharge


Query is whether the above advisory of pre-charging bootstrap and inverting PWM0 signals is applicable for all versions of GDU i.e. GDUV4, GDUV5, GDUV6 or for a specific version

Thanking in advance

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NXP TechSupport
NXP TechSupport

Hi Pratinha,

Yes, it applies to all the GDU versions.

Because the capacitor is charged only when the corresponding LS driver is active.