Hi,
i'm currently working on a Mainline Linux driver for the linear regulators of the i.MX28.
I've found out that the driver in the FSL BSP 2.6.35 uses the bit 9 (DC_OK) in HW_POWER_STS register to detect the voltage stabilization of dc control loop. But according to reference manual (page 935) this is only correct for voltage increase not for decrease.
Now i want to know, how to "make it the right way". First i thought of the HW_POWER_CTRL register with DC_OK_IRQ. But i want to be sure, that the interrupt comes for voltage increase AND decrease.
Additionally i need a timeout in milliseconds or microseconds, which defines the maximum time for voltage stabilization with enabled voltage steping. I didn't find any information about that in the datasheet.
Thanks in advance
Stefan
Solved! Go to Solution.
Hi Stefan,
You should not worry about the voltage stabilization in the decrease path. Only the increase path is critical. For example: you need a minimum voltage level for a certain peripheral to operate. The 'decrease' path is not critical because usually an increased voltage means that you will only consume more power, but the device still operates correctly.
thanks a lot
Stefan
Hi Stefan
you are right, RM (page 935) describes this is as correct for voltage increase not for decrease,
but only for LDO case. For DC-DC it is correct in both directions, below part of MCIMX28RM p.935 :
"High when switching DC-DC converter control loop has stabilized after a voltage target change. When linear
regulators are active, this bit goes high when the actual voltage is above the target voltage. Therefore,
DC_OK will go high when changing a linear regulator output to a lower value before the actual voltage
decreases to the new target value."
Regarding timeout for voltage stabilization - this depends on loads (number of capacitors, load current),
that is depends on particular design.
Best regards
igor
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Hi igor,
thanks. Regarding timeout it would be necessary to define the value outside in the devicetree.
So DC_OK_IRQ have the same limitation according to LDO like DC_OK in HW_POWER_STS?
Stefan
Hi Stefan
yes limitation the same.
Best regards
igor