Can H-bridge drivers TLD5190QV, TLD5190QU, TLD5542-1QV and TLD5542-1QU be operated with less than four MOSFETs in pure buck control mode?
In order to save BOM cost it is possible to use these H-Bridge drivers with 2 MOSFETs only.
TLD5190QV, TLD5190QU, TLD5542-1QV and TLD5542-1QU will turn on the low side gate drivers in error conditions. Then the following fault behaviors have to be considered:
- Short-to-battery: battery is getting discharged via the low side MOSFET M2 without current limitation (destructive for the discharge path)
- Overvoltage or open load: Output capacitor is getting discharged via lows side MOSFET M2 without current limitation
In order to avoid such discharge currents without current limitation the highside MOSFET M4 of the H-bridge may also be replaced by a power diode instead of a short-circuit.
When using the diode please consider the voltage drop for the duty cycle calculation (D = (Vout+Vdiode)/Vin).
Please also connect BST2 to IVCC and SWN2 to GND in order to avoid triggering undervoltage on BST2.
During input transients the device could go in buck-boost or boost mode and behave similar to normal buck controllers stopping to regulate at the maximum duty cycle.