TPS25751: TPS25751 Design issue

Hi Herbert, 

Please see my responses below: 

Herbert Wang said:

I have a few questions about the application of TPS25751D+TPD2S300YFFR. Our application scenario is that the Bluetooth speaker requires input 9V3A/5V3A, and the output requires 5V3A. Help to answer it, thank you. Which feet are used to burn the program, and whether the Bluetooth end can upgrade the chip TPS25751D online through I2C.

TPS25751 configuration (generated through the USBCPD Application Customization Tool) can be loaded through I2C using the Patch Burst Mode (PBMx) sequence, details are documented in TRM here: https://www.ti.com/lit/ug/slvucr8a/slvucr8a.pdf#page=79 

Herbert Wang said:

2. According to the schematic diagram of the EVM board, there is an external EEPROM. Is this EEPROM necessary? What are the specifications and the minimum Kb required?

The EEPROM is used to store the PD configuration (generated through the USBCPD Application Customization Tool). Upon boot-up (either through VIN_3V3 or VBUS), TPS25751 will attempt to load from an EEPROM (if available). If the EEPROM is not present, TPS25751 will remain in PTCH (patch mode, refer to TRM register 0x03) until a configuration is loaded through I2C from an external controller (MCU). TPS25751 will not operate properly until a configuration is loaded either from an EEPROM or MCU and MODE (register 0x03) returns 'APP'.

Herbert Wang said:

3. If the TYPE-C terminal does not support BC1.2, does the DP/DN network need not connect to GPIO4/GPIO5 of the TPS25751D?

If the BT speaker system does not require BC1.2 support, you do not need to connect DP/DM from the USB Type-C connector to TPS25751 GPIO4/5. 

Herbert Wang said:

4.TPS25751 with TPD2S300 circuit, with 4 MOS tube, are there any specifications for MOS tube, such as current (D-S), or Ciss requirements?

Here are the recommendations for the MOS, refer to the two parts linked as reference: 

PFET: https://www.ti.com/product/CSD25480F3 

NFET: https://www.ti.com/product/CSD15380F3 

Herbert Wang said:

5.VIN 3V3 pin, external LDO power supply, this need to be always powered? Do you need to supply power when the USB is not inserted in battery mode? If the battery is out of power, where does this voltage come from?

TPS25751 can be powered from either VIN_3V3 (normal power supply) or VBUS. If TPS25751 is powered on through VIN_3V3, the dead battery flag will not be set. If TPS25751 is first powered through VBUS then the dead battery flag will be raised and TPS25751 will not be able to source until the dead battery flag is cleared. Refer to section 8.3.2 of the datasheet shown below: 

Herbert Wang said:

6. The two groups of I2C on the EVM board are connected to the main control chip. Do we need two groups of I2C to connect to the main Bluetooth chip in our design? What are the two groups of I2C used for respectively?

I2Cc (controller, legacy terminology is refer to as master) is used for TPS25751 acting as the I2C controller for peripheral devices such as supported BQ devices and EEPROM. I2Ct (target, legacy terminology is refer to as slave) is used for TPS25751 acting as the I2C target for controller/host. An MCU/EC can be connected to TPS25751 I2Ct lines to read the PD register, send commands, and load PD configuration via PBMx flow if desired. 

Refer to the circled part below for reference: 

Herbert Wang said:

7. For the battery is double battery 8.4V, the input needs to support 9V/3A,5V/3A, the external output supports 5V3A requirements, how to connect the ADCIN1,ADCIN2 circuit

ADCIN1 and ADCIN2 are resistor divider settings to configure TPS25751 I2C target/device address (0x20, 0x21, 0x22 or 0x23) as well as its dead battery configuration (how the PD behaves when it's first powered through VBUS and a config hasn't been loaded yet). See screenshot from the datasheet below showing how the resistor divider value is decoded:

Herbert Wang said:

8. The 15th, 30th and 40th feet of TPS25751D need to be suspended. I think the EVM board is suspended.

The DRAIN pins (15, 30, and 40) are intended to be connected to a copper pad for thermal dissipation. 

Herbert Wang said:

10. Can the GPIO port of TPS25751D be used as an ordinary IO port to configure input and output?

TPS25751 GPIO pins can be configured through the Application Customization Tool to pre-set events that will toggled automatically (if configured). If the GPIO pins are not needed they can be tied to ground. 

Herbert Wang said:

11. How is TPS25751D reset?

If TPS25751 loses power (no power on VBUS or VIN_3V3), TPS25751 will re-boot upon next power cycle and will need to reload the PD configuration. An EC/MCU can also send commands to TPS25751 to perform either a hard reset (re-boot from TPS25751 ROM, no configuration loaded) or a soft reset (re-boot from the PD configuration). These 4CC commands (GAID for hard reset, Gaid for soft reset) are documented in TPS25751 TRM. 

Herbert Wang said:

12. GPIO NF and GPIO PF on the EVM board must the two networks be pulled up R63 and R64(connected to 3.83K)

R63 and R64 are not used in any ways for GPIO6/7 liquid detection FET control. Those were intended for internal testing purposes only, the schematic also shows R66 and R72 as DNP. 

Herbert Wang said:

13. Since the voltage rise and fall path of the charging chip is the same power network (9V3A/5V/3A input, 5V/3A output), should PP5V and PPHV be short-circuited together? Or is the PP5V suspended and only connected to the PPHV?

PPHV and PP5V should not be shorted together. PP5V is a 5V source only power path which should be connected to a 5V/3A supply and PPHV is a bi-direction power path that can support up to 100W (20V/5A) for both sourcing and sinking. For this design, are you pairing TPS25751D with one of the supported BQ device (BQ25756, BQ25792/8, BQ25731, or BQ25713)? 

Herbert Wang said:

6. Where does the VIN 3V3 pin of TPS25751 need to take power from, what state has to supply power, is it in the charging state (input 9V/3A,5V/3A) or external charging (5V/3A), if the battery is not powered, where does the VIN 3V3 pin voltage take power from.

VIN_3V3 should come from the system 3.3V rail for powering on ICs. If battery is not present (either the system is off or battery is dead), TPS25751 can power on from VBUS instead, refer to my response for question 5.

Herbert Wang said:

7.TPS25751 charging state (input 9V/3A,5V/3A), external charging (5V/3A), then how to configure ADCIN1,ADCIN2 this, how to set the external resistance?

Refer to my previous response for question 7. The dead battery configuration is dependent on the behavior desired for TPS25751 when booting up in dead battery mode and if the PD configuration is loaded from EEPROM or MCU. 

Let us know if you have any further questions or concerns! 

Thanks and Regards,
Raymond Lin