How to detect ramp-up/down for internal analog LDO?

[takayuki_ishii]

Hello community,

To ramp-up/down internal LDO of i.mx6,

Digital LDO(ARM, SOC, PU) can detect by control voltage raum-up time.

So it can calculate a wait time in function set_ldo_voltage() of uboot-imx/tree/arch/arm/mach-imx/mx6/soc.c

But for analog LDO(1p1, 3p0, 2p5) it have no method to control ramp-up/down time.

I think that status bits, OK_VDDxxx and BO_VDDxxx, in each regulator register(PMU_REG_xxx)

can use to detect ramp-up/down timing.

Can it use to detect ramp-up/down for each analog LDO?

If so, I hope some sample code to control voltage of analog LDO.

Best regards,

Ishii.

[takayuki_ishii]

Hello Igor,

Thank you for your quick response.

But REGn_STEP_TIME bit can control digital LDO (LDO_ARM, LDO_PU, LDO_SOC) I think.

We hoep to control analog LDO(LDO_1P1, LDO_2P5, LDO_3P0).

Does it have some control register of ramp-up time?

I think that it has only ENABLE_ILIMIT bit to save ramp-up time by current-limit circuit.

Best regards,

Ishii.

[igorpadykov]

Hi Ishii

>Does it have some control register of ramp-up time? (analog LDO(LDO_1P1, LDO_2P5, LDO_3P0))

sorry there is no way to control it.

>I think that it has only ENABLE_ILIMIT bit to save ramp-up time by current-limit circuit.

you can try it. However this option is designed only for hardware testing, not for practical usage.

NXP software does not use it.

Best regards
igor

[takayuki_ishii]

Hello Igor,

Thank you for your quick response.

> you can try it. However this option is designed only for hardware testing, not for practical usage.

> NXP software does not use it.

How about OK_VDDxxx bit in PMU_REG_xxx register?

Is this feature not for practical usage too?

We hope to detect a timing to finish transition of LDO output voltage to wait ramp-up to target voltage.

But customer plan to implement this function in boot sequence.
So they hope some guaranteed method.

If it is not practical, we must think another one.

Best regards,

Ishii.

[igorpadykov · Accepted solution]

Hi

>How about OK_VDDxxx bit in PMU_REG_xxx register?

>Is this feature not for practical usage too?

yes this option also is designed only for hardware testing, not for practical usage.

Sorry there is no tested guaranteed method for ramp  transition of LDO output to target voltage.

Best regards
igor

[takayuki_ishii]

Hello Igor,

Thank you for your quick response.

I understand this registers status.

My idea is that measure ramp-up time with the target device and wait enough time.

Don't you know some other method?

If you have any solution, please let me know.

Best regards,

Ishii.

[igorpadykov]

Hi Ishii

ramp times can be configured with CCM_ANALOG_MISC2n register (like REG2_STEP_
TIME), described in sect.18.7.20 Miscellaneous Register 2 (CCM_ANALOG_MISC2n)

i.MX6Q Reference Manual.

Best regards
igor
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[takayuki_ishii]

Hello community,

We hope to change LDO_2P5 output voltage from 2.5V to 2.65V.

In this time, we need to wait a transition time.

In digital LDO, it can control ramp-up time by register value.

But analog LDO have not it. So to detect ramp-up timing we plan to use

PMU_REG_2P5[OK_VDD2P5] status bit.

If PMU_REG_2P5[BO_OFFSET] = 010b = 50mV, and PMU_REG_2P5[OUTPUT_TRG] = 10110b = 2.65V

PMU_REG_2P5[OK_VDD2P5] will be set if LDO_2P5 output voltage > 2.60V

Can this bit be used for detect ramp-up?

Best regards,

Ishii.