TPS25751: BQ25731

Hi Jing,

Jing-Ming Zhang said:

I want use TPS25751 to replace TPS25750, can it be directly replaced according to the reference design in the datasheet without additional changes to the circuit design?

Assuming no issues with the current implementation, there should not need to be any additional changes to the circuit design.

Jing-Ming Zhang said:

If I use TPS25751, I only need to connect two components in the circuit to directly control the Charger IC BQ25731?

Not sure what you mean here, what two components are being connected and how? What is directly controlling the Charger IC? The PD, and MCU, something else?

Jing-Ming Zhang said:

If I use TPS25751 for source, should I use a charger IC for power management?If I use a charger with a PD controller, will the voltage output to the tablet be based on the PD protocol or be based on the charger voltage (1S~5S)?

It depends on what voltage contracts you want to support and how you want to support them. For any sourcing, we do require a 5V rail to PP5V. If you only need 5-V sourcing, we can configure the part to provide source contracts from the PP5V rail. For higher voltages, the TPS25751 uses the PPHV power path and some device will need to regulate the voltage once a PD protocol contract is negotiated. Yes, the BQ25731 can regulate the PD voltage from the battery voltage using it's buck-boost functionality.

Jing-Ming Zhang said:

My system requires one-to-three charging. The input voltage is 20V, and one of the outputs is 5V. Do I need a Buck circuit in this output path to reduce the voltage to 5V? Or can the voltage reduction be completed through the charger IC on the device side?

Could you share a block diagram of what you are thinking? I don't completely understand what you are looking for, one input, three outputs? What are the inputs and what are the outputs?

Thanks and Regards,

Chris

Hi Chris

Christopher Lim1 said:

Could you share a block diagram of what you are thinking? I don't completely understand what you are looking for, one input, three outputs? What are the inputs and what are the outputs?

The fallowing is my simple block diagram for your reference.

My input is a 20V type-c adapter,After passing through the first TPS25750 in the system, it needs to be divided into three different paths.

The first line needs to step down to 5V to charge device1. Do I need a Buck to step down or can I control the charging voltage through the charger IC in device1?

The third path is to charge the tablet through the PD protocol. The tablet has a Charger IC. Do I need to use the Charger IC BQ25731 in my system?

Christopher Lim1 said:

Not sure what you mean here, what two components are being connected and how? What is directly controlling the Charger IC? The PD, and MCU, something else?

I use PD to control Charger IC.

With the above block diagram, if I replace TPS25750 with TPS25751, can I directly control the BQ25731 without using an additional I2C interface?

What is the biggest difference between TPS25750 and TPS25751? Can you give a brief introduction?

Thanks a lot.

Hi Jing-Ming,

Is there a battery in the system? I'm a little confused about what the BQ25731 is used for.

How are you regulating system power? Is the type-c adapter always guaranteed to provide a certain power level? How are you making sure that the power draw from the three ports does not exceed what has been negotiated at the TPS25750 sink port?

Is the type-C adapter guaranteed to source 20-V? Understand that for typical type-C PD, we can and will negotiate lower voltage contracts if that is all that is available. Also, every type-c contract will start with a 5-V contract. your implementation of the 20-V rail to device 2 may be of concern.

Jing-Ming Zhang said:

The first line needs to step down to 5V to charge device1. Do I need a Buck to step down or can I control the charging voltage through the charger IC in device1?

You probably need a dedicated 5-V buck for device1. I'm not sure how the charger IC (Bq25731) would regulate the 5-V for Device1. I mainly support the PD controllers so may be missing something here.

Jing-Ming Zhang said:

With the above block diagram, if I replace TPS25750 with TPS25751, can I directly control the BQ25731 without using an additional I2C interface?

It can control it for basic PD and configuration. We do not support custom I2C writes and it is primarily for general setting configuration and programming voltages and currents based off of active PD contracts. If you need additional features, and I2C host (mcu/ec) may be required.

Jing-Ming Zhang said:

What is the biggest difference between TPS25750 and TPS25751? Can you give a brief introduction?

PD 3.2 compliance and future support. The TPS25751 is a direct successor so should support all the same features and is p2p. We will not be able to support the TPS25750 for new designs.

Depending on your answer to the guaranteed power from the sink port, you may need to address power management concerns in this system. I don't see how you will limit power draw to not exceed the sink port.

Thanks and Regards,

Chris

Hi Christopher,

Christopher Lim1 said:

Is there a battery in the system? I'm a little confused about what the BQ25731 is used for.

There is no battery in my system.Because one of FAE told me If TPS25750 is used in source, it needs to be used with Charger IC,when the sink side is not needed.

Christopher Lim1 said:

How are you regulating system power? Is the type-c adapter always guaranteed to provide a certain power level? How are you making sure that the power draw from the three ports does not exceed what has been negotiated at the TPS25750 sink port?

Is the type-C adapter guaranteed to source 20-V? Understand that for typical type-C PD, we can and will negotiate lower voltage contracts if that is all that is available. Also, every type-c contract will start with a 5-V contract. your implementation of the 20-V rail to device 2 may be of concern.

This is a charging device whose input is type-C with a maximum of 20V (100W) and the TPS25750 also sets the source & sink to a maximum of 20V (100W). The battery used by device1 is a maximum of 4.35V, and the battery used by device2 is a maximum of 4X4.35V=17.6V. Device3 is connected to the tablet through BQ25731 and PD controller. I think the Type-C adapter I chose can charge these three devices.If you have any questions, please let me know. There may be some parts that I have less thought about.

Christopher Lim1 said:

You probably need a dedicated 5-V buck for device1. I'm not sure how the charger IC (Bq25731) would regulate the 5-V for Device1. I mainly support the PD controllers so may be missing something here.

Sorry, maybe I didn't draw it clearly in the block diagram, BQ25731 is not connected to device1.According to your suggestion, I will add a buck (TPS51397A) to the device1 line to step down the 20V input from the PD to 5V and then output it to my device.

Christopher Lim1 said:

It can control it for basic PD and configuration. We do not support custom I2C writes and it is primarily for general setting configuration and programming voltages and currents based off of active PD contracts. If you need additional features, and I2C host (mcu/ec) may be required.

OK thanks,I am understand.

With the PD controller and Charger IC, I only need to be able to output the basic PD protocol voltage and no additional functions are required. If you think TPS25750 does not need to be added to the Charger IC when used as a source, I can delete the BQ25731 in the device3 line.

Christopher Lim1 said:

PD 3.2 compliance and future support. The TPS25751 is a direct successor so should support all the same features and is p2p. We will not be able to support the TPS25750 for new designs.

Depending on your answer to the guaranteed power from the sink port, you may need to address power management concerns in this system. I don't see how you will limit power draw to not exceed the sink port.

Thank you,I will replace TPS25750 to TPS25751.

This is a charging stand circuit. I think the maximum input is 20V (100W) type-C PD can meet the needs of the system. If there is any lack of consideration, please let me know. Thank you.

Thanks a lot,

Johnny

Johnny,

Jing-Ming Zhang said:

There is no battery in my system.Because one of FAE told me If TPS25750 is used in source, it needs to be used with Charger IC,when the sink side is not needed.

Ok, where is system power coming from? Is it just coming from the 100-W port? 

Jing-Ming Zhang said:

This is a charging device whose input is type-C with a maximum of 20V (100W) and the TPS25750 also sets the source & sink to a maximum of 20V (100W).

If this port is system power, it should be configured as Sink only. As mentioned before, unless you can guarantee that the Adapter connected to this port will always provide 100-W, you need to account for cases where the PD controller may negotiate a lower power level and limit device power draw accordingly. The TPS25751 does have a feature to disable the sink path if the contract negotiated is not above a certain power level, but this will mean your system will not power up at any lower power level.

For Device 3/tablet, is the port source only? What voltages do you need to support? For the TPS25751, we only support source only configurations if it is 5-V source only. If you are doing 5-V source only from port3, you would not need a BQ device either, just a 5-V rail connected to the PP5V pin.

Thanks and Regards,

Chris

Hi Christopher,

Christopher Lim1 said:

Ok, where is system power coming from? Is it just coming from the 100-W port?

Yes, the power jest coming from the type-C adapter.

Christopher Lim1 said:

If this port is system power, it should be configured as Sink only. As mentioned before, unless you can guarantee that the Adapter connected to this port will always provide 100-W, you need to account for cases where the PD controller may negotiate a lower power level and limit device power draw accordingly.

Can't I set it to Source & Sink? I'm not sure the type-C adapter can maintain 100W all the time, but I only need to output 20V, and the current size is not considered at the moment.Because device2 battery is 4S1P (17.6V), if PD controller output lower power level, can charger IC in device2 boost to high voltage?

Christopher Lim1 said:

For Device 3/tablet, is the port source only? What voltages do you need to support? For the TPS25751, we only support source only configurations if it is 5-V source only. If you are doing 5-V source only from port3, you would not need a BQ device either, just a 5-V rail connected to the PP5V pin.

Device3 is a type-C tablet device that supports the PD protocol. When charging, CC1/2 may receive a PD voltage higher than 5V, so I want to use a Charger IC (BQ25731) with a PD controller. Is this combination feasible?

Thanks a lot,

Johnny

Hi Jonny,

If you want the 100-W port to source, to be USB-IF compliant, it needs to support fixed source contracts of 5-V, 9-V, 15-V and 20-V, as well as SPR AVS. This would require a dedicated bidirectional buck-boost power path, and because we currently only support the BQ charger ICs, the TPS25751 may not work in this application.

Jing-Ming Zhang said:

if PD controller output lower power level, can charger IC in device2 boost to high voltage?

Maybe, but I don't know how you would communicate to the charger IC to increase the voltage. It looks like you have a 20-V rail connecting Device2 to the system.

Jing-Ming Zhang said:

Device3 is a type-C tablet device that supports the PD protocol. When charging, CC1/2 may receive a PD voltage higher than 5V, so I want to use a Charger IC (BQ25731) with a PD controller. Is this combination feasible?

Are you just looking for higher fixed voltages or are you looking for proprietary charging schemes?

Thanks and Regards,

Chris

Hi Christopher,

Christopher Lim1 said:

If you want the 100-W port to source, to be USB-IF compliant, it needs to support fixed source contracts of 5-V, 9-V, 15-V and 20-V, as well as SPR AVS. This would require a dedicated bidirectional buck-boost power path, and because we currently only support the BQ charger ICs, the TPS25751 may not work in this application.

The type-C adapter I currently choose has 5-V, ​​9-V, 15-V, and 20-V that support the PD protocol. The power part does not have to output 20-V all the time, as long as it can make the entire charging stand system work. I want to determine whether the step-up and step-down part can be controlled by the Charger IC on the device side.

Christopher Lim1 said:

Maybe, but I don't know how you would communicate to the charger IC to increase the voltage. It looks like you have a 20-V rail connecting Device2 to the system.

Yes, the Charger IC is designed inside device2, and the charging dock only provides a set of PoGo pins to connect to device2. Or do I need to add an extra Charger IC to the circuit of device2 and connect it to device2 via the PoGo pin?

Christopher Lim1 said:

Are you just looking for higher fixed voltages or are you looking for proprietary charging schemes?

As you said, the output of 5-V only needs to be connected to the PP5V Pin of the PD controller, but I want to confirm whether this design method is feasible when type-C hand shaking is higher than 5-V. If there is anything missing that has not been considered, please let me know, thank you.

Thanks a lot,

Johnny

Hi Johnny,

Jing-Ming Zhang said:

The type-C adapter I currently choose has 5-V, ​​9-V, 15-V, and 20-V that support the PD protocol. The power part does not have to output 20-V all the time, as long as it can make the entire charging stand system work. I want to determine whether the step-up and step-down part can be controlled by the Charger IC on the device side.

Jing-Ming Zhang said:

Can't I set it to Source & Sink?

The original question you had was regarding the 100-W port being able to Sink and Source voltage. Am I misunderstanding something here? If you want it to do both, you need a bidirectional DC-DC, which we might not be able to support. If the port is sink only, that is fine. You do need to make sure that the system never draws more power than the port has negotiated as a sink. The TPS25751 does not have built in OCP for sinking, so overcurrent needs to be managed by the system.

Jing-Ming Zhang said:

Yes, the Charger IC is designed inside device2, and the charging dock only provides a set of PoGo pins to connect to device2. Or do I need to add an extra Charger IC to the circuit of device2 and connect it to device2 via the PoGo pin?

Yes, this is what I'm trying to say. As you mentioned, a type-C adapter can offer a variety of voltages (5,9, 15,20). If you can't guarantee that the adapter will always provide 20-V (for example always pair your system with a specific adapter that does 20-V), the "20V" system rail will not necessarily be 20-V, it could be 5,9, or 15. If Device 2 is expecting 20-V at the connection, you need to convert the system "20V" rail to 20-V.

Jing-Ming Zhang said:

As you said, the output of 5-V only needs to be connected to the PP5V Pin of the PD controller, but I want to confirm whether this design method is feasible when type-C hand shaking is higher than 5-V. If there is anything missing that has not been considered, please let me know, thank you.

Yes, this configuration should support Type-C PD contracts greater than 5-V.

Thanks and Regards,

Chris

Hi Christopher,

Christopher Lim1 said:

The original question you had was regarding the 100-W port being able to Sink and Source voltage. Am I misunderstanding something here? If you want it to do both, you need a bidirectional DC-DC, which we might not be able to support. If the port is sink only, that is fine. You do need to make sure that the system never draws more power than the port has negotiated as a sink. The TPS25751 does not have built in OCP for sinking, so overcurrent needs to be managed by the system.

Sorry, maybe I expressed it incorrectly. The current idea is that device1 & device2 are sinks, device3 is the source that supplies power to the tablet, and the first PD controller always sink.The picture below is a schematic diagram.

Christopher Lim1 said:

Yes, this is what I'm trying to say. As you mentioned, a type-C adapter can offer a variety of voltages (5,9, 15,20). If you can't guarantee that the adapter will always provide 20-V (for example always pair your system with a specific adapter that does 20-V), the "20V" system rail will not necessarily be 20-V, it could be 5,9, or 15. If Device 2 is expecting 20-V at the connection, you need to convert the system "20V" rail to 20-V.

OK, thanks Chris, I will discuss with my supervisor how to add a buck-boost circuit to the circuit of device2 such as adding a Charger IC (BQ25731).

Christopher Lim1 said:

Yes, this configuration should support Type-C PD contracts greater than 5-V.

OK,thanks Chris,I will keep the configuration of device3.

Thanks a lot, 

Johnny

Hi Johnny,

If I understand correctly, power flow should look like this? I labeled the ports 0,1,2, and 3 just to make referring to them a little easier.

A buck boost between the output of p0 and p2 is only necessary if you can't guarantee 20-V from the Type-C adapter. Is p0 meant to work with any adapter, or is there a specific pairing you are expecting.

Thanks and Regards,

Chris

Hi Christopher,

Christopher Lim1 said:

If I understand correctly, power flow should look like this? I labeled the ports 0,1,2, and 3 just to make referring to them a little easier.

Yes,that's right,What you drew is the same as what I expected.Is there something I haven't considered with this approach?

Christopher Lim1 said:

A buck boost between the output of p0 and p2 is only necessary if you can't guarantee 20-V from the Type-C adapter. Is p0 meant to work with any adapter, or is there a specific pairing you are expecting.

I have pre-selected a type-C adapter that supports the PD protocol. According to the design, I think any type-C adapter that supports the PD protocol can support my charging dock.

As shown in the figure below, I would like to ask, PD controller No. 1 is activated by connecting to type-C to obtain V-in 3.3V. Do I need to pull another line to output 3.3V to PD controller No. 2 to activate this PD? Or can the Charger IC provide a set of power to activate PD controller No. 2?

Thanks a lot,

Johnny

Hi Christopher,

Sorry, I miss a question.Can the output of TPS25751 be set to 20V through the GUI? Or what other settings can I use to achieve this?

Thanks,

Johnny

Hi Christopher,

Christopher Lim1 said:

Not all Type-C PD adapters support 20-V. Some will do 9-V or 15-V max. If this is the case, how do you expect to generate the 20-V rail?

There are also a range of power levels, from 15-W max to 100-W max. How will your system handle different power levels?

When selecting an adapter, I will determine the output voltage and maximum power (e.g. 20-V, 100-W).If there is the 9-V or 15-V condition mentioned above, I will place a charger IC on the P2 path to adjust the voltage according to your suggestion.

Christopher Lim1 said:

I would recommend generating a 3.3-V rail off of the system voltage rail. It may need to be wide input (5-V - 20-V) depending on how you handle the input PD contract from port 0(100-W max sink). You should not use the LDO3V3 output of the TPS25751 PD controller 1 to power VIN3V3 of other IC's. The LDO3V3 pin is primarily meant for the PD controllers EEPROM and for I2C pullups.

I'm not familiar with the Charger IC, but it would need to provide a 3.3V rail to VIN3V3 to power PD controller 2.

If the Charger IC can provide Vin 3V3 to PD controller 2, then do I not need to pull another 3V3 power supply from the system to PD controller 2?

Christopher Lim1 said:

You can use the GUI to configure the TPS25751 to negotiate a 20-V contract. The TPS25751 acts like a switch. The voltage is generated by the Type-C Adaptor and will be passed through to the system side when a valid contract is negotiated. So yes, the TPS25751 can be set to accept and negotiate 20-V contracts, but the adaptor must first offer 20-V for the contract to be negotiated. If 20-V is not available, the PD controller will try to negotiate the next available highest power contract, which could be 5, 9, or 15-V depending on the adaptor.

If my adapter is a 20-V 100-W maximum, I can set the voltage to be fixed at 20-V through the TPS25751 GUI and output it to my subsequent system.Is there any mistake in my understanding?

Thanks,

Johnny

Hi Johnny, 

Chris is currently out of office. Please allow some delay in responses. 

Best Regards, 

Aya Khedr 

Hi Aya

It's okay.I will look forward to your reply.

Thanks Aya and Chris

Best Regards, 

Johnny

Hi Christopher,

Christopher Lim1 said:

Yes this is correct. The TPS25751 will negotiate a 20-V contract with the adapter and close it's power path, allowing the adapter power to flow to the system side.

Christopher Lim1 said:

For the P2 path, if it a single direct 20-V, you may be able to get away with a boost/buck-boost.

I sorted out the above two points. The following is my understanding. Please help me check whether it is correct.

If the adapter I use is a 20-V 100-W maximum and the output is set to 20-V through the TPS25751GUI, then the P2 path does not need to be buck-boosted. If the adapter is a 5-V, ​​9-V, or 15-V adapter, then a buck-boost needs to be added to the P2 path.

Best Regards,

Johnny

Hi Johnny, 

Chris is currently out of office. Please allow some delay in responses. 

Best Regards, 

Aya Khedr 

Hi Aya

It's okay.I will look forward to your reply.

Thanks Aya and Chris

Best Regards, 

Johnny

TI is closed today, sorry about delay in response.