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TPS51222 split rail operation

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5 Posts
Texas Instruments Employee
Keith Keller posted on 13 Aug 2009 2:37 PM

Hello,

I'm wondering if the TPS51222 dual controller can be run from split rails.  It would be designed into a dual redundant battery pack. 

My thought is to have diodes off each battery pack connected to Vin pin.  Then connect one battery to top-side of FETs for output1 and the other battery to top-side of FETs for output2. 

It's possible that the battery protection FETs could interrupt power to either one these phases. 

My question is if this connection scheme will work.  If power is lost to one of the phase, will the other phase continue to operate properly for the required redundancy?

Thanks for your help.

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12 Posts
Texas Instruments Employee

Keith,

The TPS51222's protection features, specifically UVP, are going to cause a problem with this configuration.

As described on Page 25 of the TPS51222 datasheet (http://focus.ti.com/lit/ds/symlink/tps51222.pdf) the UVP feature turns off both channels.  As a result, 1ms after the power from one of the battery packs was lost, both channels would shut-down.

It may be possible to avoid this fault condition.  The UVP function has a 1ms delay, if the affected channel is disabled before that delay finishes, the fault condition would be avoided and the other channel could remain operational.

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