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TPS61085: ripple is too high

Part Number: TPS61085
Other Parts Discussed in Thread: DRV8833,

Dear :

 tps61085 boost 9Vout to DRV8833 VM as schematic,now the output ripple is high , could you help me optimize the output ripple,  the bad time is 1.5V around when motor is running;

try to find reason, B5819WS is removed(customer need this diode to protect ), the out ripple is more than 500mV ,but still higher , need your help to optimize;

 yuntai2103sch.pdf

  • dear ,

    The motor rotates every 40 degrees at an interval of 3 seconds,   during motor stops, the tps61085 ripple has 7.68Vp-p pulse as below, how to deal with it ?

  • Hello Copper,

    I would like to confirm with you that how did you measure the output ripple? Please follow the below method to measure TPS61085 output ripple:

    To achieve the most-accurate, noise-free measurement, remove the hat from the probe tip and wrap a wire around the probe barrel for the ground connection. This minimizes the inductance by reducing the length of the ground return loop.

    And did you follow tps61085 layout suggestions when doing the layout?

    For the 7.68Vp-p pulse, I think it is because of the reverse current of motor when it is stopped. The reverse current will charger the output capacitors C90, C91. To reduce this, you can add output capacitance OR add a diode between TPS61085 and motor driver to prevent the reverse current.