JAJSU28 March 2023 DRV8329-Q1
PRODUCTION DATA
External components in the power stage are not required by design but are helpful in suppressing transients, managing inductor coil energy, mitigating supply pumping, dampening phase ringing, or providing strong gate-to-source pulldown paths. These components are used for system tuning and debuggability so the BLDC motor system is robust while avoiding damage to the DRV8329-Q1 device or external MOSFETs.
Figure 8-5 shows examples of power stage components that can be optimally placed in the design.
Some examples of issues and external components that can resolve those issues are found in Table 8-2:
Issue | Resolution | Component(s) |
---|---|---|
Gate drive current required is too large, resulting in very fast MOSFET VDS slew rate | Series resistors required for gate drive current adjustability | 0-100 Ω series resistors (RGATE/RSOURCE) at gate driver outputs (GHx/GLx), optional sink resistor (RSINK) and diode in parallel with gate resistor for adjustable sink current |
Ringing at phase’s switch node (SHx) resulting in high EMI emissions | RC snubbers placed in parallel to each HS/LS MOSFET to dampen oscillations | Resistor (RSNUB) and Capacitor (CSNUB) placed parallel to the MOSFET, calculate RC values based on ringing frequency using Proper RC Snubber Design for Motor Drivers |
Negative transients at low-side source (LSS) below minimum specification | HS drain to LS source capacitor to suppress negative bouncing | 0.01uF-1uF, VM-rated capacitor from PVDD-LSS (CHSD_LSS) placed near LS MOSFET’s source |
Negative transient at low-side gate (GLx) below minimum specification | Gate-to-ground Zener diode to clamp negative voltage | GVDD voltage rated Zener diode (DGS) with anode connected to GND and cathode connected to GLx |
Extra protection required to ensure MOSFET is turned off if gate drive signals are Hi-Z | External gate-to-source pulldown resistors (after series gate resistors) | 10 kΩ to 100 kΩ resistor (RPD) connected from gate to source for each MOSFET |