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LM5170-Q1: About the breaker circuit used in TIDA-01168

Jeff_Liu
Prodigy 150 points
Part Number: LM5170-Q1
Other Parts Discussed in Thread: TIDA-01168, LM5170

Hi,

In TI Designs of TIDA-01168,it use LM5170-Q1 to be a bidirectional DC-DC Converter Reference Design for 12-V/48-V automotive systems.

In the design there are two breakers design  used to disconnect the 12V and 48V  battery.

And I want to know why we must use the breaker circuit to disconnect ?

when I want to stop the converter, I set the Iset=0, and the buck-boost power stage cirduit is disable ,the "HO" and "LO"signal is low, the 12V and 48V is disconnected. Why we must use the breaker circuit?

  • 0
    TI__Guru* 75865 points

    Hi,

    Thank you for posting.  I thought I already answered the question at the meeting yesterday.  If you want to completely break off the source from the circuit, you need back-to-back FETs.  The referenced TIDA design intends to be able to break both the 12V and 48V batteries from the LM5170 circuit to mitigate some failure mode effects, so it includes two breakers. Yes you can set ISETA=0 to stop the current, but the circuit is still electrically connected and not broken off from the source.  

    You may need to contact your OEM customer to find if breaking off from the battery is a required feature, then decide whether or not you can copy the TIDA scheme. 

    Thanks,

    Youhao Xi, Applications Engineering

  • 0 in reply to Youhao Xi
    Prodigy 150 points

    Hi xi,

    Thank you for your help.

    Because I still can't  understand the answer yesterday.

    In the circuit HV_port is 48V battery and LV_port is 12V battery, and I think the voltage of HV_PORT is higher than the LV_port, so a back-to-back  FETs design may be unnecessary?

    And the bias supplies we may supply from an extra signal port of KL30f from ECM, so I think  if  the voltage of  HV_PORT always higher than the LV_port, we may not need use an back to back FETS design.