PCA9306: PCA9306 frequency issue

Derek Zhong said:

Part Number: PCA9306

Dear TI, We are using PCA9306 to replace MAX14591, manage MDC/MDIO interface level conversion. 

1. Please help to confirm the frequency range of PCA9306 (the maximum circuit frequency of 1MHz I2C bus is recommended in the specification).

It depends on the driver architecture and system. In a uni-directional push pull topology with low capacitance, this device can be used to support up to 200MHz (see figure 3) without level translation. In an open drain architecture (like I2C) where capacitance is a huge limiter, we may not be able to support 1MHz....

2. Can PCA9306 be used as a management interface (MDC/MDIO) at 2.5MHz frequency?

[Bobby] It can be used for this application but depends on system factors. Figure 3 shows the bandwidth this device can support in an ideal system.

PCA9306   MDC_MLX and MDIO_MLX signal     many  steps

PCA9306 MDIO_MLX and 1V8 signal

MAX14591  MDC_MLX and MDIO_MLX signal

3. Please help confirm whether the schematic design and the values in the diagram are OK (R215 has been modified to 200K).

[Bobby] Looks like your LDO may be losing regulation, I suspect this is because the schematic is not set up properly. For level translation support with this device, you need to short Vref2 and the enable pin (I specifically wrote this into the datasheet, see figure 6). Your schematic is closer to figure 7 of the datasheet which I state is incorrect.

Thanks for your support.