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TPS92512: ISENSE Pin peak current vs DC current.

Traver Gumaer1
Intellectual 320 points
Part Number: TPS92512

I am working on a prototype of a new design using the TPS92512. I was assuming the the ISENSE pin worked as a normal peak current comparator input and expected the voltage to reach a peak 0.300V and shut off the buck switch. What I see is the ISENSE voltage reaching approximately 0.430V. Looking a little closer at the datasheet, the ISENSE resistor setting should be 0.300V at the DC current you require, not the PEAK current.

Since the ISENSE pin is a sawtooth waveform, what part of the waveform is the IC is tracking? Is it 1/2 the peak-peak ISENSE voltage? Does Vin influence the set point? This is just a curiosity question more than a problem.

  • 0
    TI__Mastermind 25500 points

    Hello Traver,

    We have multiple control topologies that each offer benefits. We do have hysteretic peak/valley detect types and they are great for fast PWM dimming and transient response. The TPS92512 is a current mode control type device that uses a transconductance amplifier so it will regulate ISENSE to an average voltage of 300mV (or whatever you set using IADJ). It cannot PWM nearly as fast as a hysteretic type, but it has great line and load regulation while also having a constant switching frequency. So setting LED current is as simple as V=IR for this device.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Intellectual 320 points
    Average was the key I was looking for. When I did the initial design calculations, I was assuming 300mV peak like a standard current mode controller, but it works great using 300mV average.

    Thanks!

    Traver