Hi,
Can you please tell me what is the threshold current for light load condition or how to calculate the threshold value for light load in LM25141?
Regards,
Soumya
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Hi,
Can you please tell me what is the threshold current for light load condition or how to calculate the threshold value for light load in LM25141?
Regards,
Soumya
Soumya,
Section 7.3.14 of the datasheet explains when LM25141 enters standby mode. First the LM25141 starts skipping pulses, then it enters low-power standby mode when >= 16 pulses in a row are skipped.
This state has a high-side switch time of tsw=70ns (typical), the minimum controllable on-time (7.3.8.1). You can calculate the power delivered to the output with 70ns pulses at your given frequency, VIN, VOUT, L, load... and find when it starts to skip pulses as well as when it will skip 16 in a row.
-Sam
Hi Sam,
Thank you so much.
Eventually I want to calculate output voltage tolerance at light load (1mA in my case). Can you please tell me how to calculate the same.
Regards,
Soumya
Soumya,
See Figure 4 in the EVM User's Guide. Also see section 8.2.1 of the datasheet showing the design considerations of output voltage regulation +/- 1%.
-Sam
Hi Sam,
Thank you very much for the document. But the output voltage which I am looking is 3.3V, hence Figure 4 in the EVM User's Guide is not useful for me.
LM25141-Q1 is synchronous converter right, how can it operate in discontinuous mode.
Regards,
Soumya
Soumya,
Figure 4 shows the kind of variation you can expect. You can expect a very similar value variation for 3.3V.
LM25141-Q1 shuts off the low-side FET when the inductor current reaches 0A. This effectively emulates a diode like in a non-synchronous buck but with the added efficiency of a synchronous buck.
-Sam