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LM5170-Q1: Ramp pin connection and current report accuracy question

John Chou62
Intellectual 2070 points
Part Number: LM5170-Q1

hi Team,

my customer testing on the LM5170-Q1 EVM.

1. in the DS the RAMP1 pin is connected to the HV-Port. as DS "the RAMP pin voltages are sawtooth signals with a slope proportional to the HV-Port voltage. in this way the RAMP signals convey the line voltage info." the customer application is opposite of this application, they will mainly use as a boost converter, so the LV-port  as input will have voltage change, while the HV-Port as output (voltage stable). so should we connect the RAMP to the LV-port ?

2. the EVM stating the performance of current accuracy to be 1%. however using the EVM in the following test condition. the error seems to be > than 1% (1.79%)

can you help comment on the setup, tweaks?

operate in Buck mode (Vin = 48V, Vout = 14.4V, load current 28A (real))

the Iout1_V = 0.874V, Iout2_V = 0.876V

  • 0
    TI__Guru* 78100 points

    Hi John,

    Thank you for post.  

    1. You can and this would have faster response to the boost input variations.  

    2. You need to take into account your resistor tolerance:  both the IOUT resistor and current sense resistor.  The datasheet specified accuracy is just the IC error which does not include your external component errors.

    Hope this clarified.

    Thanks,

    Youhao