MIMXRT1064 Power On

[joelbrown]

We want the MIMXRT1064 to automatically power on when +3.3V is applied to the DCDC_IN pins.

We don't want to use a button on the ONOFF or WAKEUP pins. Is this possible?

We have a Lithium coin cell connected to VDD_SNVS-IN pin so we can use the RTC.

I assume it will automatically go into SNVS mode when +3.3V power is removed. Is this correct?

[joelbrown]

We have decided not use the RTC inside the MIMXRT1064 and use an external RTC.

This means we will connect VDD_SNVS_IN to 3.3V which will go to zero when power is removed from system.

In this case MIMXRT1064 will power on by itself without using ONOFF signal, is this correct?

Also external RTC uses much less power so coin cell will last much longer.

[joelbrown]

The state diagram does not show what happens when DCDC_IN is removed. Does it go to SRTC state?

To go from SRTC to On when power is applied can we have a simple circuit that generates a pulse to the ONOFF pin?

[EdwinHz]

Hi @joelbrown,

When using an external supply, you would set the internal DCDC converter to bypass mode. From the Hardware Design User Guide, "If you want to bypass internal DC/DC, you still need to power DCDC_IN. DCDC_PSWITCH should be grounded to disable the DC/DC, and DCDC_LP should be left floating."

And yes, you could apply a pulse to the ONOFF pin to transition to ON.

BR,
Edwin.

[joelbrown]

I am not sure what is meant by external PMIC? Another microcontroller, some logic or something else?

Do you have any examples?

[EdwinHz]

Hi @joelbrown,

Of course, for more information about PMICs please follow this link: https://www.nxp.com/products/power-management/pmics-and-sbcs:POWR_MAN_USER_INTERFACE

Instead of following Figure 21-1. "Chip reset scheme under PMU control" from the RM:

You would follow Figure 21-2. Chip reset scheme under external PMIC control:

This in order to have the external PMIC handle the power and cause the resets to cycle the board between ON and OFF states. Also take a look at "Table 21-2. Power mode transitions" on section "21.3.3 Power mode transitions"

BR,
Edwin.

[EdwinHz]

Hi @joelbrown,

The RT1064 undergoes its booting process as soon as it received an adequate power-up sequence (which includes but is not limited to the 3.3V supply on DCDC_IN). Figure 21-3. "Chip on/off state flow diagram" of the Reference Manual shows the On/Off state transitions. As you can see, from a completely OFF state, when there a SNVS supply present (like a coin cell battery), and later the 3.3V chip power becomes present, the chip will transition to power ON:

In this scenario, the MCU "automatically" transitions from OFF to ON solely with the presence of the relevant power supplies. However, as you can see on this diagram, this is the only scenario where this is possible. From there, removing the 3.3V chip supply will not automatically transition the RT device to the OFF state, which in turn cannot reset the flow to a SNVS Power ON Reset followed by a Chip Power ON Reset.

I believe what you are looking for is an automatic transition between power modes with only supply connections/disconnections. That, I'm afraid, is not possible natively on our RT devices. Perhaps with the use of an external PMIC you could handle the power-up and power-down sequences adequately, while also generating the POR_B signal accordingly in order to transition from OFF to ON and back to OFF again with just supply connection/disconnection.

BR,
Edwin.