Hello guys,
One of my customers is going to evaluate TPS54308 for their next products.
Their conditions are the follows.
Vin=16V +/- 10%, Vo=12V, Io=0.8A,
L value equation is described as the equation (8) on page 16 in the device datasheet
TPS54308 datasheet
http://www.ti.com/lit/ds/symlink/tps54308.pdf
I can understand the equation. The inductor ripple current should be = Io (average of the maximum output current) * K coefficient.
Also I think 0.3 will be used for the K coefficient at design starting in general.
L value calculated by the equation with the customer conditions, Vin(Max)=17.6V, Vo=12V, Io=0.8A and K=0.3, fSW=350kHz is 45.5uH.
But L value calculated by WEBENCH is 13uH as the attached.
I have a few questions as the follows. could you give me your replies?
Q1. Which calculated L value is better? 13uH or 45uH?
Q2. If 13uH calculated by WEBENCH, what parameter is considered for L value calculation in WEBENCH? In the result, ILp-p is about 1A and K coefficient is almost 1.
Q3. In case of TPS54308, the phase compensation is fixed internally. Is the L value range limitted by the fixed compensation?
Your reply would be much appreciated.
Best regards,
Kazuya.
