On Friday 01 April 2016 02:09 AM, Mark Brown wrote:
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On Fri, Apr 01, 2016 at 01:18:23AM +0530, Laxman Dewangan wrote:
On Friday 01 April 2016 12:52 AM, Mark Brown wrote:
So as per above, it will be adjusted to 13.75mV/us (nearest higher side) for
device configuration but this device need to configure for 27.5mV/us.
You're saying that the device is so bad at regulating the ramp rate that
it's not only failing to keep up with the desired ramp rate and capping
at whatever rate but it's also doing even worse if configured for a
slower rate? That's not great, it sounds like it's doing the ramp
control via some sort of dead reckoning thing rather than by actually
ramping the voltage it's trying to regulate like it was asked to.
Is the error in the observed values a function of the capacitance that
we can calcuate here?
As per datasheet, There is no direct equation for ramp time deviation
when regulator output current cross the regulator current limit.
From data sheet:
/**
During a DVS transition, the regulators output current will increase by
COUT*dV/dt. In the event that the load current plus the additional
current imposed by the DVS transition, reach the regulator’s current
limit, the current limit will be enforced. When the current limit is
enforced, the advertised DVS transition rate (dV/dt) will not occur.
And there is calculation of Iinrush based on Cout and configured dv/dt.
Iinrush=min(Ilim & Cout*dV/dt).
IINRUSH calculation for Cout = 100uF
IINRUSH=min(ILIMP & COUT*dV/dt).
SD0 is a two phase regulator with a typical PMOS current limit (ILIMPP0)
of 3.75A per phase. For ILIMP in the above equation we will use
2x3.75A=7.5A.
SD0 has a typical soft-start rate (dV/dt_SS_SD0) of 25mV/us. For dv/dt
in the above equation we will use 25mV/us.
IINRUSH=min(7.5A & 100uF*25mV/us).
IINRUSH=min(7.5A & 2.5A).
IINRUSH=2.5A
**/
So providing configured and observed value direct will help much here.
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