TPS560430: Do you have any application curves in PFM mode like 9.2.3 section on page 20 of TPS560430 datasheet(SLVSE22B)?

Hi

Q1: no problem for 1mA-50mA

Q2: 12Vin 3.3Vo 60mA, Vin_ac, Vo_ac, SW and IL

Q3: both wenbech value or datasheet is value are OK to use. prefer datasheet value in table 1

 Hi Daniel,

 Thank you very much for your reply and the waveform.

 Could I ask you an additional question as the follow?

 Q. The customer wants to select inductor part for their power supply condition (Vin=24V, Vo=12V, Io=0.05A(50mA)).

       According to table 1, the inductor value is 33uH because they use Vo=12V and 1.1MHz PFM version.

       While the inductor current is not large because their maimum load current is only 50mA.

       I think a inductor which have 200mA peak current can be used for their case.

       But in the output short condition, 1.4A current which limitted by HS current limitter would be flowed

       into the inductor. Then the inductor will be saturated because 1.4A is much larger than 200mA peak current

       and the inductor current is increased rapidly. In the saturation case, I think HS current limitter response time 

       would not be enough to protect over current.

       My question is,

       Do they need to select inductor part which has 1.5A saturation current as 9.2.2.4 Inductor Selection section

      regardless their output current?

 Could you please give me your reply?

 Thank you again and best regards,

 Kazuya.         

Hi

for the inductor selection, if the output have the short condition, the safe way is choosing saturation higher than 1.1A . typical value will be fine.

alternative way is the saturation current higher than  0.8A, and at 1.1A the inductance not drop lower than 50% of original value, the converter will  protect the device well cause it have the valley current protection with peak current protection together.

when customer use second way, pls let them take care of the temperature raising of the inductor in short condition.

Thanks

 Hi Daniel,

 Thank you very much for your reply and I'm sorry to be late my response.

 Could I ask you a few additional questions?

 As I said, the maximum current of their load is 50mA only. Also they don't care about output short

situation because they take a way to avoid the short.

 In that case, how we calculate the inductor peak current?

 If their output load current is steady at 50mA, it is enough that the inductor peak current is 200mA.

 But if the load current is changed from 0mA to 50mA or from 10mA to 50mA, rapidly 

then switching mode would be will be changed from DCM mode to CCM mode and the inductor current

will be exceeded 200mA.

 My questons are the follows.

 Q1. Do you have any way to calculate the inductor peak current at the transient condition?

 Q2. Do they need to use a inductor which have 1.1A or more satuation current as you said in the previous thread

       though their maimum load current is 50mA only? (They want to use small size inductor because Io=50mA only.)

 Q3. If these is no way to calculate the peak current, is it better to check the inductor current using TPS560430 EVM?  

 Could you please give me your reply?

 Thank you again and best regards,

 Kazuya.

 Hello Daniel,

 Could you please  give me your reply?

 Thank you and best regards,

 Kazuya.

Hi 

1. You can sim the result to see peak current by TI-Pspice, the peak current is related the output and inductor value in transient 

2. if no short condition will happend, it is fine to 200mA rated current, cause current level is RSM value. 

3. EVM inductor is 1.5A rating