topic Re: PCA9450CHNY LOADSW_CTRL Register in Power Management

PCA9450CHNY LOADSW_CTRL Register

omar_wolfe-huss — Tue, 08 Feb 2022 13:48:40 GMT

I am seeing behaviour on the LOADSW_CTRL register (0x2A) of PCA9450CHNY that doesn't match the documentation. In table 64 of the datasheet is shows the reset state of the register is 0x85, which allows SW_EN to control the state of the load switch. We are seeing that devices actually power up with a default state of 0x84, which sets the load switch to "Always off". Is this expected?

Re: PCA9450CHNY LOADSW_CTRL Register

diazmarin09 — Wed, 09 Feb 2022 02:05:13 GMT

Hello Omar,

Indeed, the default value of the LOADSW_CTRL register should be 0x85.

In this case, I assume the device is detecting a short circuit current based on the SW_SC bit as follow:

As a test, could you please set this bit (SW_SC) to 1? If the device restarts in 100ms, indeed, the switch is detecting a short circuit.

Please let me know the results.

Regards,

David

Re: PCA9450CHNY LOADSW_CTRL Register

omar_wolfe-huss — Tue, 15 Feb 2022 16:39:35 GMT

Hi David,

Many thanks for your suggestion. When I change SW_SC to 1 I can see that the power is up after 100ms, confirming that a short circuit is being detected. This appears to be in-rush and so we will amend the design to prevent this from happening.