PMIC PF1550 I2C communication problem

[Ramiro]

Hi everyone!

I'm using a PMIC MC32PF1550A1EP in my design. When I power the PF1550 via VUSB (5 volts) and pull POWER high, I get all the regulators working at the default voltage values. The problem is when I try to change their voltage values via I2C. I'm using a PIC24 (power externally) as a master, and whenever I try to set the voltage at SW1 (register 0x33, value 0x3F), nothing happens.

For information I've connected an external supply (3 volts) to VDDIO and I'm sending my I2C frames to the slave address 0x08 (as described in datasheet).

Here are my schematics:

Could anyone help me please? Thanks!

[guoweisun]

If you set 3V IIC in pF1550 side,does this value match your PIC side?

[Ramiro]

Hi Guoweisun. Thanks for replying! Yes, I checked voltage and I have 3,1 volts in both sides. Concerning the timing, I created a function following the timings in datasheet. Here's the function that I'm using to send my data frames to PF1550 :

void Write_PF1550(char RegAdress, char data)
{
i2c2_start();

i2c2_wr(PF1550_ADD); // 0x08
i2c2_wr(RegAdress); // 0x33 to set SW1
i2c2_wr(data); // 0b00111111 to set the max value for SW1

i2c2_stop();
}

I've been using this function to communicate with other PMIC from other brands, and they've worked. But whenever I try to set the voltage at SW1 setting the register 0x33 to 0x3F, nothing happens. I don't know if I'm missing some configurations to use the I2C communication.

Thanks.

[guoweisun]

Is possible for send us the test waveform of IIC signals about your sending command?

[Ramiro]

Sure. Here's the waveform when I send the frame 0x08 (address) 0x32 (SW1 volt) 0x00.

Thank you.

[guoweisun]

Sorry that could you please zoom in your waveform?

[guoweisun]

If you write this register 0x33 following datasheet page72-I2C sequence timing,does it success?