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Questions about Innoswitch-Pro Series(INN3376,INN3378)- uVCC Voltage and current problem

Posted by: jason brody on

Hello, I`m the student developer interested in Innoswitch -pro Series and trying to develop product with INN3376 and INN3378.

I used the UPD301 and hlk7628 for microcontrollers, and worried about Voltage and Current problems. So I searched the forums.

My big concern is this 3 thing.

1.In the datasheet and forum, the Voltage output in uVCC pin while device startup is 5V. (In HLK7628 datasheet, It must not exceed 3.1~3.5V in any occasion. Overvoltage in this part will cause electrical arc and will catch Fire, so I have to make sure.)Did I understand correctly?

2. UPD301 uses 60mA and HLK7628 uses over 800mA. In datasheet, internal LDO can only handle 45mA maximum. If uVCC pin draws more than 45mA, than external DC-DC converter will be used. Is that mean the Innoswitch USB port Power delivery performance will be effected as well? (Like 45WUSBPD power delivery capability->35.1W USBPD power capability while uVCC pin is drawing 3.3V and 3A )

3. If external DC-DC converter is used in uVCC pin, is uVCC pin voltage follows the VUSB voltage?

Comments

Submitted by PI-Radiant on 04/05/2022

Hi Jason, thank you for your interest in our product and your questions. 

1. uVcc pin voltage will be regulated to 3.6V only after Primary-Secondary handshake occurs. Until this happens, uVcc pin voltage will be equal to output voltage. 



2. uVcc can handle a max of 45mA for ~0.5sec. Considering this, do you plan to connect the DC-DC converter at the output? If you indeed plan to connect this to output, this DC-DC converter will serve a load apart from the actual load you are trying to power up.



3. Given that uVcc pin voltage and ~3.6V and max current capability is 45mA (for ~0.5s), can you please clarify how do you plan to load the uVcc pin by connecting an external DC-DC converter?

In case you you decide use an external DC-DC converter at the output terminal to supply 3.6V to the ICs you mentioned, can you please clarify why you plan to connect it to uVcc pin?



Regards

PI-Radiant

Submitted by jason brody on 04/05/2022

Thanks For the reply, but It raises me more questions...

1. Well, Than I do need to put DC-DC buck converter on the uVCC pin First. Thanks! 

2. I uploaded the rough schematics of my product. Well, in the circumstances like uVCC needs lots of current than expected(over45mA), do I have to make seperate AC/DC converter, disconnect the whole circuit connected to uVCC pin, and reconnect all of them  into seperated AC/DC converter?

3 I will use MP1470. I will plan to use LM2596 as well. If I have to use seperate AC/DC, I will simply put LED and 330ohm resistor to pull the current.  Normal MT7628 can bear 3.6V. However, HLK-7628 can bear 3.5V maximum. In my opinion, the DC-DC buck converter will be necessary. well, just to make sure.

Submitted by PI-Radiant on 04/05/2022

Hi Jason, thank you for sharing the schematic. We see that the Buck converter connected is expected to supply about 9W power.

Since the max power uVcc pin can supply is much less than this, its better to connect a LDO/Buck converter at Vbus instead of uVcc pin as shown in the modified schematic attached.

Please note that connecting it this way would imply max USB-PD load will be (45-9)=36W. 

In case 45W is required to be supplied to USB-PD load, then one might have to use a 60W design with 2 secondary windings. 1 for USB-PD load and another for HLK, UPD ICs. 

Regards

PI-Radiant

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