AM3352 and Power On

Markus Olsson

Other Parts Discussed in Thread: AM3352, TPS65910A

Hi,

How should the AM3352 reset and power pins be configured to be able to power on the chip properly just by turning on the 5V for the TPS chip?

The PWRON pin is sampling the state (bouncing) and depending on the state it can turn on/off. In our application there is no such thing as a button, only 5V voltage that is enabled.

over 13 years ago

0 Biser Gatchev-XID over 13 years ago

TI__Guru**** 393215 points

Markus,

What PMIC have you selected?

Best Regards

Biser

0 Markus Olsson over 13 years ago in reply to Biser Gatchev-XID

Prodigy 180 points

Hi,

TPS65910Ax

BR
Markus

0 Biser Gatchev-XID over 13 years ago in reply to Markus Olsson

TI__Guru**** 393215 points

Applying input voltage is enough to start the PMIC. See Figure 4 in the TPS65910A datasheet. You can leave the PWRON pin NC - there is an internal pullup on this pin active by default.

Biser

0 Markus Olsson over 13 years ago in reply to Biser Gatchev-XID

Prodigy 180 points

The PWRON pin/signal is not even in figure 4. Are you sure?

I can see the PWRON signal present in figure 5 but not in figure 4.

0 Biser Gatchev-XID over 13 years ago in reply to Markus Olsson

TI__Guru**** 393215 points

Yes it's not necessary. You can check the ICE EVM schematics (3386.am335x_15x15_ice-rev_a2.pdf). It's done exactly this way there.

Biser

0 Markus Olsson over 13 years ago in reply to Biser Gatchev-XID

Prodigy 180 points

Hi,

I'm still a bit confused when looking at Turn On / Turn off Tables.

SWCU093B, Page 7 describes my connection. PWRON has a 10k pull-up with a button. Is the button used after 5V has been applied to the TPS65910A31 chip?

The PMIC_PWR_EN signal from AM3352, is that active when not using an external Buck for VRTC? How can it be used for POWERHOLD if the internal LDO for VRTC is used? Is that always on when applying 5V to the TPS chip?

BR
Markus

0 Biser Gatchev-XID over 13 years ago in reply to Markus Olsson

TI__Guru**** 393215 points

Hi Markus,

If you have a battery-powered device, the PMIC will start when you connect the battery. Then a long press on the power button will turn it off, a short press will turn it on. If you remove the battery obviously the PMIC will turn off. In your case you apply +5V - PMIC turns on, you cut +5V - PMIC turns off.

For the PWRHOLD signal, check Figure 4 in the PMIC datasheet (SWCS046Q), and the note below the timing diagrams. For the PMIC_POWER_EN functionality vs. VDDS_RTC supply please check note E below Figure 4-1 in the AM335X datasheet. Obviously you will need uninterrupted VDDS_RTC supply in order to use the PMIC_POWER_EN signal to keep the PMIC in on state.

Best Regards

Biser

0 Markus Olsson over 13 years ago in reply to Biser Gatchev-XID

Prodigy 180 points

Hi Biser,

Which of the TPS chips will keep VDDS_RTC alive (internal LDO) for the PWRHOLD pin to work as intended?

Or is all of this programmable in the built-in EEPROM?

BR
Markus

0 Biser Gatchev-XID over 13 years ago in reply to Markus Olsson

TI__Guru**** 393215 points

Hi Markus,

They all keep it alive, but the "A" and "A3" versions put it in low-power mode (0.1mA) during sleep. The "A31" version keeps in in full power all the time. The version you select is also dependent on the type of memory you intend to use - "A" is for DDR2 and "A3", "A31" for DDR3.

This bit is in the EEPROM (VRTC_REG, bit VRTC_OFFMASK).

Biser

0 Biser Gatchev-XID over 13 years ago in reply to Biser Gatchev-XID

TI__Guru**** 393215 points

Markus,

I want to correct myself. It's not 0.1mA during sleep, but in OFF state, so it shouldn't really concern you.

Biser

0 Markus Olsson over 13 years ago in reply to Biser Gatchev-XID

Prodigy 180 points

Can the A and A3 version be programmed not to go into 0.1mA while being in the "off" state? I mean can they be programmed to be at full power? If we need to choose A or A3 because of memory configuration I would still like it to be in full power. Is that possible or am I restricted to only use A31 version?

The main issue is that we don't want to add more components to the design (external buck).

0 Biser Gatchev-XID over 13 years ago in reply to Markus Olsson

TI__Guru**** 393215 points

Yes, like I wrote above bit VRTC_OFFMASK in the VRTC_REG is an EEPROM bit, and you can access this register via I2C.

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AM3352 and Power On