i.MX Processors中的主题 PF1550 power input question?

PF1550 power input question?

sparkyee — Tue, 20 Aug 2019 13:28:06 GMT

Hi,

I am looking to use the PF1550 PMIC with an iMX6UUL micro and wondering

about the power path capabilities of this part. The datasheet lists

VBUSIN to VSYS resistance as 100 250 550 mΩ. I am trying to understand if

the only current limitation is maximum case temperature? The reason I am questioning

this is that I see only 1 VBUSIN pin and there are 2 VSYS pins to drive the power

input of the part's regulators. I want to use the PF1550 PMIC with and without lithium ion

battery pack in multiple applications.

Thanks!

Larry

Re: PF1550 power input question?

reyes — Tue, 20 Aug 2019 18:18:53 GMT

Hi Larry,

PF1550 part number MC32PF1550A6EP is programmed to work with an i.MX6ULL with DDR3L.

We have a schematic that you can use as a HW reference design, see the below PF1550 + i.MX 6ULL reference design, and enclosed schematic in PDF format.

KIT6ULL-1550EVM (PF1550 + i.MX6ULL).

SCH-29464,1.35V LvDDR3

In this schematic, on page 10 you can find a note with the required modification when used with (Battery Operation mode) and without battery (in DC mode).

Jose

NXP Semiconductors

Re: PF1550 power input question?

sparkyee — Tue, 20 Aug 2019 20:50:51 GMT

Hi Jose,

I have seen the schematics you have sent . I am looking at

the example schematic on page 134 of the PF1550 datasheet where

the PF1550 derives its powers through a USB port via signal VBUSIN

pin 34. I am trying to determine the maximum current that can be driven

into that pin 34? This will allow me to power VSYS by either the battery

or the VBUSIN pin via the power path FETs. USB charging ports are capable

of supplying almost 2 amps and I need to know if the power path FETs will

be reliable at that current level? The diagram of the power path on page 42

eludes to this capability, unless I am not understanding it?

Thanks for helping!

Larry

Re: PF1550 power input question?

reyes — Wed, 21 Aug 2019 15:54:08 GMT

Hi Larry,

I’m a little confused, you are asking for the maximum current that can be driven into pin 34 (VBATT2), but talking about the VBUSIN (pin 37).

For your description, I’m guessing that you are referring to VBUSIN pin (pin 37) current capabilities, right? Assuming this is correct, then, you can find the charger input current limit on this pin on table 6 (pages 12 and 13 of the datasheet). For the VBUSIN pin, the max ILIM is 1500mA.

The default settings of the VBUSIN and CHG_OPER control bits are such that when a charge source is applied to VBUSIN, the PF1550 turns on its linear regulator in LINEARON or CHARGE-ON (via OTP), and limits the charge current to 100 mA (via OTP).

The input current limit works by monitoring the current being drawn from the input and comparing it to the programmed current limit. The current limit should be set based on the current-handling capability of the input adapter. Generally, this limit is chosen to optimally fulfill the system-power requirements while achieving a satisfactory charging time for the batteries. If the adapter current exceeds its output capability, the charger responds by reducing the charger current, thus keeping the current drawn from the adapter within its capability.

To set the ILIM to 1500mA, you need to program the VBUS_LIN_ILIM [4:0] bits to 10100 on VBUS INPUT CURRENT LIMIT REGISTER (0x94) as can be seen in table 57 and table 58 on page 56 of the datasheet.

Regards,

Jose

NXP Semiconductors