PCA9306: pca9306 Schematic diagram check

xujunfeng

Part Number: PCA9306
Other Parts Discussed in Thread: TCA4307, TCA9800, TCA9509

The attachment is ltc4307cms8#pbf with PCA9036 to achieve 3.3V to 1.2V, 1 drive 4 function.

There are 2 ltc4307cms8#pbf+PCA9036, each drive 2 FPGas (it is required that the load is less than 3, please help to confirm that the 4307 can isolate the load.) .

The rate is 400KHz.

At present, I am mainly worried about ltc4307cms8#pbf and PCA9036 signal outgoing line oscillation or the rise and fall edge is not monotonous, please kindly take time to review, thank you8311.pca9306.pdf

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 316640 points

Both the TCA4307 and the PCA9306 will increase the V_OL; check the V_IL of the 1.2 V devices. All pull-up resistors act in parallel; if the other devices do not have enough drive strength, you might need to increase their values (and maybe reduce the speed).

0 xujunfeng over 1 year ago in reply to Clemens Ladisch

Prodigy 220 points

hi, now we are afraid that the VOL to slave side is too big, please ask if there are other suggestions or solutions

0 Clemens Ladisch over 1 year ago in reply to xujunfeng

Guru 316640 points

I guess you need the 4307 for hotplugging and the PCA9306 for level shifting? The only way to improve V_OL is with a buffer like the TCA9800. (Its A side should go to the 4307; there must not be pull-up resistors on the B side.)

0 Jack Guan over 1 year ago

TI__Mastermind 40046 points

Hello Xujunfeng,

The schematic on the PCA9306 looks OK. Similar to what Clemens' mentioned, this device is a switch so the VOL will be as a result of the VIL + the voltage drop across the internal pass FET. In order to achieve lower VOLs (for a valid VIL at the 1.2V input), a weaker pullup can be used, or by replacing the PCA9306 with an I2C redriver that can drive a lower and fixed VOL such as the TCA980x.

Here is an app note on pullup selection for the I2C bus: I2C Bus Pull-Up Resistor Calculation

Please let us know if you have any further questions.

Regards,

Jack

0 xujunfeng over 1 year ago in reply to Jack Guan

Prodigy 220 points

Hi，The 3.3V master end is fixed with a pull-up resistance and cannot be changed. The 1.2V end can be designed freely. We do not have a hot swap requirement, only a buffer is required to enhance the drive capability. So I don't think the 980x is a good fit

0 Clemens Ladisch over 1 year ago in reply to xujunfeng

Guru 316640 points

The TCA9509 allows low voltages on the A side, and star connections on the B side.

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PCA9306: pca9306 Schematic diagram check