The start-up behavior of this controller is critical in our application. I have three questions that are not addressed by the datasheet:
1) The capacitor on the SS (soft-start) pin is charged from approximately 300mV to at least 4.3V with a 9uA (typical) current source. This source is specified as possibly having a 3 to 20uA range. Is distribution or histogram information available for this current source?
2) This almost 7-to-1 range in current is troublesome. Is this current source more consistent within a common batch, or date code, of parts? For example, can we expect all parts within a batch to fall within a 3.0 to 6.0uA, 4.5 to 9.0uA, 6.8 to 13.5uA or 10 to 20uA range?
3) The voltage on the SS (soft-start) pin limits the output voltage of the error amp (COMP pin) thereby limiting the phase shift between OUTA and OUTB. Is this relationship characterized? For example, what I'm looking for would be: with SS<2.0V phase shift is zero, with SS=3.0V maximum phase shift is 90° and with SS>4.0V maximum phase shift is 180°.
This information will help us determine worst case conditions and the necessary adjustments to obtain desired results.