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TPS92518-Q1: TPS92518-q1 PWM modulation accuracy.

Meng Liu
Intellectual 1765 points
Part Number: TPS92518-Q1
Other Parts Discussed in Thread: TPS92518

Hi Expert

my customer want to use this device in 7A output current application.

I want to confirm this device PWM modulation accuracy.

my customer requirement that is in the case of small current, can the PWM width remain stable at 0.8us?

  • 0
    TI__Mastermind 28655 points

    Hello Meng,

    This depends on a few things.  What is your PWM frequency?  What is your inductor value?  What is your off-time setting?  What is your input voltage?

    Best Regards,

  • 0 in reply to Irwin Nederbragt
    TI__Intellectual 1765 points

    Hi Irwin

    thank for you suggest.

    In fact: I haven't set up tps92518EVM because this device GUI can't run in my PC, Shanley is helping me resolve GUI issue.

    but My customer need conclusion of PWM modulation accuracy, they require TPS92518 have stable output current in the below condition:

    PWM: 8us pulse wave( PWM frequency is flexible)

    input voltage:8.5V~16.5V

    output voltage: 4.5V~12V

    output current: minimum 100mA peak 

    they just very care about small output current can stable output. 

    so could you please help to check TPS92518 whether can cover this application scenarios?

    could you please help me to verify it in our EVM because I need to provide 100mA current wave to customer as soon as possible.

  • 0 in reply to Meng Liu
    TI__Mastermind 28655 points

    Hello Meng,

    is the on-time pulse width 0.8 us or 8 us?

    Again, the switching frequency (or off-time setting) is needed to calculate this as well as the inductor value.  Current ramps up in the inductor by V = L * (di/dt), dt is very short, V will vary if Vin and/or Vled varies.  0.8 us is too short for this to reach 7A, 8 us it could work.  You may have to look into shunt FET dimming.  The next issue will be current ripple.  At 0.8 us there won't be several switch cycles of the TPS92518 MOSFET which can cause the current to vary pulse to pulse.  Keeping the ripple current low will improve this.  Non shunt FET dimming will not have this issue however the current will vary based on Vin and Vled values and if they change during operation the current will change.

    Best Regards,