TPS65216: DCDC3 and DCDC4 Power-Up Default Selection

Hi Jim,

The RSEL values listed in Table 5-2 are the settings for the base TPS65218xx device, the TPS65218D0. The DCDC3 and DCDC4 values should indeed be 1.2V and 1.8V. If you connect these two RSELs to GND, the TPS65216 will still power up as the default voltage values (1.2 and 1.8V). However, you can also externally configure the DCDC3 and DCDC4 values with an external resistor divider or through I2C if necessary. The best reference for seeing what these regulator voltage outputs are programmed to is by going to the Register Maps, Section 5.5 of the datasheet. This is where you can find all the EEPROM settings for this device.

Best,
Emily

Hi Emily,

I thought I did externally configure DCDC3 and DCDC4 when I connected the 20K (RSEL) resistor to pin 17, DC34_SEL. Based on Table 5.2 what should I measure at DCDC3 and DCDC4? If the RSEL value does not set DCDC3 and DCDC4 correctly it appears the only alternative is to attempt I2C programming or the PMIC is bad. At least the part that compares and latches the voltage developed at pin 17 during startup.

The TPS65216 is in the default state that was received. Perhaps I'm not interpreting Table 5.2 correctly. Please advise.

Thanks,

Jim

Jim,

My apologies, I misunderstood your original message. Can you short DC34_SEL to GND with a 0-ohm resistor and confirm you read DCDC3 = 1.2Vout and DCDC4 = 3.3Vout?

Best,
Emily

Hi Emily,

With DC34_SEL shorted to GND, DCDC3 measures 1.2Vout and DCDC4 measures 1.8Vout. It seems DCDC4 output is not responding to the change in DC34_SEL impedance. Perhaps DCDC3 is not responding to the change in DC34_SEL either.

Thanks,

Jim

Hi Jim,

Are all other regulators working as expected and probing SW shows accurate regulation? If so, can you try reading the EEPROM via I2C and seeing if it is indeed programmed to 1.8V? 

Best,
Emily

Hi Emily,

The other regulators are as follows:

DCDC1   1.1V  ok

DCDC2   1.1V  ok

DCDC3   1.2V  should be 1.5V

DCDC4   1.79V should be 3.3V

LD01       1.8V  ok

LS           not used

I looked at the outputs with an oscilloscope and they seem to be regulating well. Not sure what you mean by probing SW? If that means probing the switch node before the inductors then I haven't looked at that signal but I can look at that today.

As I mentioned I have a small load (16.5 ohms) on all regulators because when I initially powered up the TPS65216 without any load the regulators were cycling on and off.

One thing I did notice in the datasheet was that the DCDC4 regulator should have a 47uF cap. Currently there is a 10uF cap installed that was used for all the other regulators. I will change the cap to 47uF but I don't expect that will have any impact on the DCDC4 output voltage. 

The test PBC doesn't have a uproc installed yet to use I2C but I do have a Total Phase Aardvark I2C/SPI Host Adapter that I can use to read the EEPROM. I'll report the findings as soon as I can.

Best,

Jim

Hi Emily,

I am still attempting to read the EEPROM using I2C but this will take a little longer to complete. I was reflecting on the DC34_SEL resistor change from zero ohms to 20K ohms with no change in DCDC3 and DCDC4 output voltages. I scoped the DC34_SEL pin during startup after Power Enable was set high and I didn't measure any voltage pulse at all. Given that DCDC3 and DCDC4 are constantly set to 1.2V and 1.8V respectively, it seems that the DC34_SEL pin maybe tied to INT_LDO which would correspond to the last line in Table 5-2 of the datasheet. The strange thing is that I should be able to measure the INT_LDO voltage level but that isn't the case as the voltage is zero. I can measure 20K ohms from DC34_SEL to GND right at the pin on the package. Is it possible that this chip has a faulty internal connection to DC34_SEL?

Best,

Jim

Jim,

That's odd indeed. Are you able to do an A-B-A swap for this device? Can you also provide your schematic? 

Best,
Emily

Hi Emily,

I'm just building a second (B) board and should be able to test this afternoon. I'll update when new information is available.

Best,

Jim

Hi Emily,

The second board has been built and the new TPS65216 chip works as expected. The DCDC3 and DCDC4 outputs are 3.27V @ 100mA and 1.50V @ 100mA respectively with RSEL = 20K ohms.

If I remove the first TPS65216 from the PCB, can TI analyze the chip to determine the root cause of failure? 

Best,

Jim

Correction, DCDC3 is 1.5V and DCDC4 is 3.27V.