SPRACN0F October 2021 – March 2023 F29H850TU , F29H859TU-Q1 , TMS320F280021 , TMS320F280021-Q1 , TMS320F280023 , TMS320F280023-Q1 , TMS320F280023C , TMS320F280025 , TMS320F280025-Q1 , TMS320F280025C , TMS320F280025C-Q1 , TMS320F280033 , TMS320F280034 , TMS320F280034-Q1 , TMS320F280036-Q1 , TMS320F280036C-Q1 , TMS320F280037 , TMS320F280037-Q1 , TMS320F280037C , TMS320F280037C-Q1 , TMS320F280038-Q1 , TMS320F280038C-Q1 , TMS320F280039 , TMS320F280039-Q1 , TMS320F280039C , TMS320F280039C-Q1 , TMS320F280040-Q1 , TMS320F280040C-Q1 , TMS320F280041 , TMS320F280041-Q1 , TMS320F280041C , TMS320F280041C-Q1 , TMS320F280045 , TMS320F280048-Q1 , TMS320F280048C-Q1 , TMS320F280049 , TMS320F280049-Q1 , TMS320F280049C , TMS320F280049C-Q1 , TMS320F28374D , TMS320F28374S , TMS320F28375D , TMS320F28375S , TMS320F28375S-Q1 , TMS320F28376D , TMS320F28376S , TMS320F28377S , TMS320F28377S-Q1 , TMS320F28378D , TMS320F28378S , TMS320F28379D , TMS320F28379D-Q1 , TMS320F28379S , TMS320F28384D , TMS320F28384S , TMS320F28386D , TMS320F28386S , TMS320F28388D , TMS320F28388S , TMS320F28P650DH , TMS320F28P650DK , TMS320F28P650SH , TMS320F28P650SK , TMS320F28P659DH-Q1 , TMS320F28P659DK-Q1 , TMS320F28P659SH-Q1
For better power efficiency, many DC-DC systems implement a synchronous boost controller, where the secondary switch replaces the feed forward diode that exists in a regular boost controller (#T5843526-100). Peak Current Mode Control is one of the more common methods used to control this topology and the C2000 MCU has some unique features that allow it to implement this type of control very efficiently.
The addition of the second FET demands precise control of the ON/OFF time of the primary and secondary switch relative to one another. If the switches are in the “ON” state at the same time, there is a direct path to ground for the active current to flow, which is not only in-efficient but also potentially harmful to the lifetime of the FET switches.
An accurate way to implement this type of system is to have the comparator monitor the inductor current and actuate the FETs when the current exceeds a predefined threshold. Ideally, when one FET is switched ON, the other FET can be switched OFF at the same time. However, due to switch mismatch and board propagation delays, simultaneous switching from the controller likely will not result in simultaneous switching at the FETs, which creates the shoot through mentioned earlier. While techniques in software can help hold off the switching of the secondary switch to avoid this condition, these can be challenging to implement with the various hardware interdependencies coupled with the time constraints of the control loop.
The C2000 MCU has implemented programmable deadband control, derived from the comparator output itself, to prevent this condition while keeping the C28x CPU unloaded (#T5843526-101). This allows a complete PCMC solution to be realized outside of the CPU domain once initialized. This logic exists on all PWM modules on a given device, allowing multiple stages to have different deadbands, such as a Phase Shifted Full Bridge, where there are multiple switching pairs.