Hello,
Regarding to VFB (feedback) on TPS56528, my customer is asking a question.
(Question)
Why is VFB threshold voltage at eco mode large comparing with continuous mode?
Certainly, the output ripple is become large at eco mode. But they couldn’t make clear why VFB threshold at eco mode not same as continuous mode.
Could you please tell us this reason?
Regards,
Tao2199
Hello Tao,
TPS56528 uses the DCAP2 control mode that compare VFB voltage and internal REF voltage. when VFB voltage is less than REF voltage, IC turns high side on. please refer below picture.
In light mode, due to smaller loading, ripple is bigger than heavy loading, FB average voltage is above REF by half ripple. So, FB voltage is higher with light mode, and lower with heavy load.
best regards.
edwin zang.
Hello edwin,
Thank you for reply.
I have informed information from you to my customer and have an additional question.
(Question)
My customer understand that VREF is meaning VFB threshold voltage (following diagram).
If so, VREF level will becomes different depending on switching mode(DCM/CCM).
Their understanding is correct?
Certainly, FB average is changed by ripple at switching mode.
But they couldn’t make clear why VREF level (VFB threshold voltage) is changed by switching mode.
Could you please tell us this reason?
Regards,
Tao2199
