TPS55289: Level shift for I2C and enable pin

Mahboob Khan Mohammed

Part Number: TPS55289

Hello,

Does this interfaced works or does it require a level shifting? The I2C lines are going directly to a micro controller that is working at 3.3V and the TPS55289 is configured to use internal LDO. So I was wondering if I need to shift that voltage level for I2C pins and also for enable pin?

Regards,

Khan

over 2 years ago

0 Bryce Xun over 2 years ago

TI__Mastermind 28600 points

Hi Khan,

No, both I2C pins and EN pin don't need level shift, the current configuration is ok. Recommend to connect EN to AGND with a 100k pull-down resistor.

BRs,

Bryce

0 Mahboob Khan Mohammed over 2 years ago in reply to Bryce Xun

Intellectual 275 points

Hi Bryce,

Just to clarify. According to datasheet, when you connect the VCC(pin-18) to EXTVCC(pin-21) you will be using internal LDO for logic circuitry inside of TPS55289, correct? and the internal LDO's output is set at 5V volts isn't that mean when you interface the device to a lower voltage(3.3V) level would it it not need a level shifter?

Thanks!

Khan

+1 Bryce Xun over 2 years ago in reply to Mahboob Khan Mohammed

TI__Mastermind 28600 points

Hi Khan,

The EXTVCC is the just LDO selection pin which chooses internal or external LDO.

The I2C pins are both open-drain connection, so it doesn't matter if it connects to 3.3V or 5V.

BRs,

Bryce

0 Mahboob Khan Mohammed over 2 years ago in reply to Bryce Xun

Intellectual 275 points

Hi Bryce,

Could you have a look at the full schematics below and see if there is any gotchas? a quick review. Thanks!

0 Bryce Xun over 2 years ago in reply to Mahboob Khan Mohammed

TI__Mastermind 28600 points

Hi Khan,

May I know what their application is and any other project details e.g. volume, schedule etc?

What is the input voltage, output voltage and max output current for this device?

BRs,

Bryce

0 Mahboob Khan Mohammed over 2 years ago in reply to Bryce Xun

Intellectual 275 points

HI Bryce,

This application requires the Input voltage ranged 12V to 30V, the output voltage ranged 12V to 20V, and the current is 5A max.

Thanks!

Khan

0 Bryce Xun over 2 years ago in reply to Mahboob Khan Mohammed

TI__Mastermind 28600 points

Hi Khan,

Will this device output 20V/5A at 12Vin? This device can't support this and the thermal would be a large concern.

BRs,

Bryce

0 Mahboob Khan Mohammed over 2 years ago in reply to Bryce Xun

Intellectual 275 points

Hi Bryce,

The application we are using this device in, at 20V it wouldn't be consuming all 5A, it will be less than 3A at 20V. We expect a 5A of current only at 12V output.

-Khan

0 Bryce Xun over 2 years ago in reply to Mahboob Khan Mohammed

TI__Mastermind 28600 points

Hi Khan,

This device can fit your application. Here are my comments about the schematic:

1. MODE pin needs to set to high or low to choose I2C address, I don't see that in the schematic.

2. The saturation current of the inductor needs to be higher than 8A.

3. Please follow the layout guide.

TPS55289 Layout Guideline.pdf

BRs,

Bryce

0 Mahboob Khan Mohammed over 2 years ago in reply to Bryce Xun

Intellectual 275 points

Bryce,

1. MODE is connected to GND.

2. What do you think about this inductor, BOURNS, SRP7050WA-4R7M.

3. Thanks for the layout guide.

-Khan

0 Bryce Xun over 2 years ago in reply to Mahboob Khan Mohammed

TI__Mastermind 28600 points

Hi Khan,

The inductor looks good.

BRs,

Bryce

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TPS55289: Level shift for I2C and enable pin