TPS7H4013-SEP: Efficiceny and Temeparture Graphs for TPS7H4013-SP

Hi Mohamed,

The TPS7H4013 can be used as a buck converter, or an inverting buck-boost converter but not as a regular buck-boost converter (non-inverting).

Figures 7-23, 7-24, and 7-25 in the datasheet do show the efficiency of the TPS7H4013. The other efficiency plots that show data for the TPS7H4012 should also be valid for the TPS7H4013 up to 3A on the x-axis, as that is the maximum DC current of the TPS7H4013.

Thanks,

Andy

Hi Andy, 

thanks for that info,

1) all the plots are for TPS7H4012 44-pin HTSSOP (DDW) package, will the 20-Pin CFP HLC have the same response ? 

2) to give you some numbers of what we want to do, and you can advise on the feasibility of that:

we are supposed to generate 3 voltages, 2positive and 1 negative, the voltages nominal and accepted limits under steady state and transients are:

VP1 [6.69,6.9,7.11] with OVP EOL worst case limit 7.82  
I_VP1 [0.45,2.4]

VN2 [-6.69,-6.9,-7.11] with OVP EOL worst case limit -7.82 
I_VN2 [0.15,0.8]

VP3 [5.67,5.9,6.03] with OVP EOL worst case limit 6.63
I_VP3 [0.7,4.4]
 

fsw = 249 KHz

the most optimum case is to generate from our 28V Primary side only one positives secondary voltage of  ( up to us to choose with estimated +-(1-3)% ), and feed it to TPS7H4012 or TPS7H4013 and get the voltages & currents above.
the question here is if based on 9.3.3.2 ( maximum output voltage ) this solution would be feasible and at the same time do not exceed the recommended operation point of 14V ( for the inverting buck boost ) 

I used 306 ns as the minimum offtime based on datasheet value with 2A Isw with different values of Vin(+-3%), is this the correct approach ?

Voutmax = vin*(1-toffmin*fsw)

Do you think that one SEC voltage can do the job or 2 SEC voltage would be needed to stay within 14V during nominal and transient conditions for the inverting buckboost ?

Thanks!
Mohamed

the OVP limit can be lower, this is just the red line that we shouldn't cross.

Hi Mohamed,

Efficiency between HTSSOP and CFP packages does not have the same response. When CFP versions of the TPS7H4012 and TPS7H4013 are available they will be added to the datasheet. In the meantime, the TPS7H4011-SP datasheet contains efficiency plots showing both HTSSOP and CFP packages if you want to get an idea of the package's impact on efficiency.

If all three converters use the same VIN then it will not be possible to make the IBB without violating the maximum voltage stress (14V) while allowing enough VIN for the VP1 converter to operate.

One option to consider is the possibility to operate the IBB off the the 5.9V rail that is being generated "VP3". In both rail's normal ranges, the maximum voltage stress on the IBB would be ~13.14V which is in-range for the TPS7H4012 or 4013. If both rails go over their nominal maximums then there is potential to go above 14V on the IBB unless the "worst case OVP" limits are tightened.

Thanks,

Andy

Hi Andy, 
Thanks for the suggestion, yeah that should work will go over our requirements to confirm that!
I have a follow-up question would it be an overkill to use TPS7H4013-SEP as inverting buck boost for a voltage rail that is around -6.1V (+-3%) with
30mA to 150mA ? 
would a negative LDO or Inverting charge pump a better solution ?

Thanks! 
Mohamed

Hi Andy, 
unfortunately this solution won't work because this low current is on a different lane than the previously disused, on this lane only 2 voltages are needed +-6.1V. +6.1V with max current 2.6A & -6.1V with max current 130mA.

in that case I think it would be essential to have +ve and -ve voltage generated by a flyback with SR where negative voltage is fed to -ve LDO and since the current is really low, this should not be affected by the poor regulation. 

Thanks! 
Mohamed

Hi Mohamed,

If that is the case, I would consider simply generating +6.1V from the flyback, and use an IBB and Buck to convert to the other voltages you need. This should simply the flyback design.

Thanks,

Andy

Hi Andy, 
I thought we agreed that 130mA max current is a light load of TPS7H4013, and a negative LDO would be more advisable , correct ?
I would love to generate only one positive voltage from flyback but in that case we would need to generate +- Voltage and then feed them to buck for +6.1 and to negative LDO for -6.1V &130mA max current. did I get you right ?

Thanks! 
Mohamed

one other point for the TPS7H4013 as IBB, EN/SYNC/PWRGD must not exceed 7V according to the datasheet ( with respect to GND as 0V).
when IBB used with Vout=-7V, this means that these signal won't be able to be used, is this correct ?

Hi Mohamed,

Yes, since the GND of an IBB is referenced to the negative rail, signals such as EN, SYNC, and PWRGD may need to be level-shifted to accommodate this.

Is it okay if I reach out to you at the email associated with your E2E account? I believe this thread along with your other active thread may be getting outside of the scope of the original E2E posts.

Thanks,

Andy

Hi Andy, 
yeah sure! that would be great! sorry for the drift. 

BR,
Mohamed

Hi Mohamed,

Thanks, we will reach out via email soon.

Thanks,

Andy