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JoLu_3455101
Level 4
Level 4
5 likes given 5 solutions authored 25 replies posted

Hi,

Typically when a depleted sink device is plugged into a USB PD charger, it has dead battery resistor (Rd-DB) to trigger the charger to provide power until its internal battery is charged enough, then it replaces Rd-DB with "regular" Rd to negotiate a PD contract.

For sink devices with no internal battery, I am concern that the delay that occurred during the switch from Rd-DB to Rd will cause the PD charger to stop providing power and cause a power cycle issue:

  1. Charger provides power to sink controller due to present of dead battery
  2. Sink controller sees power, removes/replaces dead battery resistor
  3. Charger doesn't see dead battery resistor, stop providing power
  4. Since there is no internal battery, sink controller loses power temporarily when switching from dead battery mode to normal mode
  5. Repeat steps 1-4

We've seen some DRP controllers that have this power cycling/oscillating effect.

Does CYPD3171 have this effect? Can the CYPD3171 be the sink controller for a device with no battery? Is there a delay during the switch from Rd-DB to Rd for CYPD3171 ?

Thanks,
Jonathan

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1 Solution
Abhilash_P
Moderator
Moderator
Moderator
50 likes received 500 replies posted 250 solutions authored

Hi,

 

   The port information in the EZ-PD Config utility has to reconfigured to make its default state as a sink. 

Please refer the following image for more information,

Abhilash_P_0-1628233456729.png

 

 

Regards,

Abhilash P

View solution in original post

5 Replies
Abhilash_P
Moderator
Moderator
Moderator
50 likes received 500 replies posted 250 solutions authored

Hi,

The battery monitoring flow in CCG3PA is as explained below,

  1. Power up. If in self-powered condition (battery is powering the system), continue. If in dead battery condition, go to Step 6.a.
  2. Enable TYPE-A port with default configuration and TYPE-C port as DRP.
  3. Disable internal VBUS regulator because external VDDD is present.
  4. Start VBATT monitoring.
  5. From this point, TYPE-C port can stay unattached or get attached as sink or source. TYPE-A port is always source.
    a) If TYPE-C port gets connected as sink, do a PR SWAP if port partner is DRP and not externally powered. This ensures that power bank is charging the DRP device. Otherwise, stay in sink mode and charge the
    battery.
    b) If TYPE-C port gets connected as source, stay as source.
  6.  Look for VBATT < Cut off voltage. If VBATT falls below Cut off voltage:
    a) If TYPE-C port is connected as sink, stay as sink. If we came here from dead battery condition, wait for VBATT to rise above Restart voltage and then disable internal VBUS regulator as external VDDD is now available to power CCG3PA.
    b) If TYPE-C port is not connected to anything, configure it as sink only device.
    c) If TYPE-C port is connected as source, remove VBUS and wait for disconnect. On disconnect, configure it as sink only device.
    d) Disable TYPE-A port. Idea here is to stop discharging of battery and wait for user to connect a
    power adapter on TYPE-C port.

 

VBATT voltage: VBATT cut-off voltage is the limit below which battery discharging is stopped. User is expected to program this to a value which ensures battery is not completely drained. If VBATT falls below Cut off voltage, CCG3PA stops sourcing power on TYPE-A and TYPE-C ports.

Please refer the below image from the CCG3PA datasheet,

Abhilash_P_0-1627911786990.png

The dead battery resistors are connected on to the CC lines as explained above. The physical interpretation is as below,

Abhilash_P_1-1627911846083.pngAbhilash_P_2-1627911889471.png

 

Please let me know if this explanation has answered your query. 

 

Regards,

Abhilash P

 

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Thanks Abhilash for the reply. It helps me understand the CCG3PA system flow better. However, I am still a little puzzled about whether a sink device without a battery can use the CYPD3171 as its controller. From the monitoring flow, the dead battery resistors (which the sink device needs) will bring us to step 6a. Since we don't have a battery (i.e. USB-C monitor with no internal battery), what's next?

While the CYPD3171 can power up from the dead battery resistors by getting the default 5V from a power adaptor, can it negotiate a power contract (i.e. 9V) while in the dead battery state? If yes, then I think CYPD3171 can be used in this application. However, if the dead battery resistors get switched to Rp or Rd (regular, not dead battery) and there is a delay during the switch, then the power cycling issue that I mentioned would occur and hence would make the CYPD3171 not a candidate for this application.

I understand that there are other CCG families which are better suitable for this application, but due to the current semiconductor shortage, we are trying to make use of what we have.

Best regards,
Jonathan

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Abhilash_P
Moderator
Moderator
Moderator
50 likes received 500 replies posted 250 solutions authored

Hi, 

 

   From your below statement, 

"However, I am still a little puzzled about whether a sink device without a battery can use the CYPD3171 as its controller. From the monitoring flow, the dead battery resistors (which the sink device needs) will bring us to step 6a. Since we don't have a battery (i.e. USB-C monitor with no internal battery), what's next?",

     When you say that there is no battery at all on the sink side, then it doesn't come under power bank solution. Its just a sink device negotiating for power from the source. During this state, the sink has only Rd termination on its CC pins. As soon as a source is connected to this device, it sees the Rd termination resistor and starts providing 5V on the VBUS path. This voltage is used by the sink to power up its internal chip and circuitry and start its power negotiation with the source.

Please let me know if this explanation has helped you in understanding your doubt.

 

Regards,

Abhilash P

 

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Hi Abhilash,

You are correct that this is not a power bank application. I have witnessed a PD charger provide 5V power when dead battery resistors are present.

 

However, when CYPD3171 is the UFP controller (the one presenting the Rd-DB), I have witnessed a power cycle issue. It appears that once the CYPD3171 gets the 5V "dead battery" power from the charger, it boots up and removes Rd-DB (to switch to a provider mode). In turn, the PD charger stops providing power, and the result is a power cycle/loop issue.

My guess is that the configuration/firmware of CYPD3171 in default state is not correct. If this is the case, can you tell me how to configure the CYPD3171 to sink-only mode in default state so it won't remove Rd-DB once it powers up?

Thanks,

Jonathan

 

0 Likes
Abhilash_P
Moderator
Moderator
Moderator
50 likes received 500 replies posted 250 solutions authored

Hi,

 

   The port information in the EZ-PD Config utility has to reconfigured to make its default state as a sink. 

Please refer the following image for more information,

Abhilash_P_0-1628233456729.png

 

 

Regards,

Abhilash P