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TPS65381 VDD1sense output current

user4658708
Prodigy 90 points
Other Parts Discussed in Thread: TMS570LS3137, TPS65381-Q1, TPS62160

Hi，

I am using a TPS65381 for TMS570LS3137, we used VDD1sense as tms570LS3137 VCC core supplier which the input voltage is 1.2V.

from TPS65381 datasheet, i can find the maximum output VDD1sense current is 600mA, but from TMS570LS3137 data sheet, TI No. SPNS162, TMS570LS3137 PBIST mode consumes 700mA current.

so my question is：

1, the output of VDD1sense is from 0.8V---3.3V, whether the output is always 600mA, or the output current is a variable based on output voltage;

2,could we used tps65381 as tms570ls3137 power supplier?

thanks!

  • 0
    TI__Mastermind 20590 points

    The TPS65381 can and is widely used with the TMS570 MCU family, however the newer TMS570 devices do have load currents that have to be carefully considered.   

    The VDD1_sense pin is not sensing the current at all.  It is sensing the voltage at the resistor divider from VDD1 for two purposes:

    1) regulation, this is the feedback or sense pin for the regulation loop

    2) VMON voltage monitoring blocks which will provide the UV/OV detection when enabled for VDD1.

    As noted in the datasheet VDD1 since the FET is external doesn't have a current limit, but is limited up stream by the VDD6 switching pre-regulator.  There are at least a few points to consider when using VDD1 at 700mA.  

    • Total load current on VDD6.  It is rated for up to 1.3A total for all downstream regulators.  So when PBIST is run the application must make sure the total loading on VDD6 will be below 1.3A.
    • FET current and Thermal:  the external FET will be dropping the voltage from ~6V to ~1.2V so the heat and current is in this FET.  Assuming a FET is chosen that can handle the current and the system design manages the thermal loading it should be fine.  Since the 700mA is only for PBIST which is a short duration the elevated current and thermal load should be time

    As an alternative, if the application will exceed VDD6 current or the thermal will be too high, alternatively a DCDC converter may be used instead of the VDD1 LDO controller.  This will gain the efficiency benefits thus lowering the load current on VDD6 and also reducing the thermal loading in the system.  The TPS65381 VDD6 would supply the input voltage to the DCDC converter, such as the TPS62260-90-Q1 and the output voltage could be scaled with a 2nd resistor divider to put the target sense voltage (0.8V) on VDD1_SENSE and the VMON from TPS65381-Q1 can be used. 

    Best Regards,

    Scott

  • 0 in reply to Scott Monroe
    Prodigy 100 points

    Are there any other recommended switching regulators for generating the core voltage?
    I have seen one application example using the TPS62260-90-Q1 and one using the TPS57112.

    I was thinking of using the TPS62160 (or equivalent in SOP package) instead, is there anything against using that one?

    Thanks in advance!

  • 0 in reply to Niels_D
    TI__Mastermind 20590 points

    Any DCDC that has acceptable input voltage range if cascading from VDD6 or VBAT (supply) directly and appropriate output voltage range will work.  VDD1_SENSE will monitor the output voltage.  We have used TPS6226x and TPS57112 devices because they are automotive qualified and many of our applications are in automotive.  They also have a tighter output regulation specification than the TPS62160.  It appears TPS62160 is a +/-3% regulator, the VDD1_UV threshold is 94 to 98% nominal, and the VDD1_OV is 103% to 106%.  So with the TPS62160 there is a possibility if it is regulating low by 3% and the threshold for VDD1_UV detection is at the maximum (98%) on TPS65381 it would detect the UV and cause RESET.  The other DCDC regulator families we have listed are 1.5% or better in regulation to ensure there is no overlap in their possible regulation with respect to the UV or OV detection from TPS65381.

    Scott

  • 0 in reply to Scott Monroe
    Prodigy 100 points
    Okay, thanks.

    I noticed that even by using a separate switcher for VDD1, the efficiency of the TPS65381-Q1 is not good enough to meet my requirements.
    As I am not very familiar with SIL yet, I posted another question regarding this issue:
    e2e.ti.com/.../530248