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TPS65218: TPS65218

Madhusoodana Bairy6
Intellectual 680 points
Part Number: TPS65218
Other Parts Discussed in Thread: , TPS65910, , IPG-UI

Hi Team,

We are using TI's TPS65218B1 PMIC in one of our design. As per my understanding, PMIC's L5 and L6 (outputs of DCDC5 and DCDC6) should be always on if we are supplying CC pin with RTC battery. But I am not seeing any voltage on these pins when AC-DC adapter is powered off (RTC was giving 2.76V at this time). Please suggest.

Regards,
Madhusoodana Bairy

  • 0
    TI__Mastermind 30280 points
    You need to set the FSEAL bit == 1 to keep DCDC5 and DCDC6 enabled when AC-DC adapter is removed. When FSEAL bit == 1, DCDC5 and DCDC6 will remain on until the Coin Cell backup battery supply is removed.

    This is highlighted in Figure 5-34 Modes of Operation Diagram in the TPS65218D0 datasheet: SUSPEND, RECOVERY, PRE-OFF, and OFF states all show "DCDC5..6 = FSEAL dependent"

    The procedure for setting the FSEAL bit is in section 5.5.2 Freshness Seal (FSEAL) Bit, which consists of consecutive I2C Writes of [0xB1, 0xFE, 0xAE] to the Password Register (Reg. 0x10) without any other I2C Reads/Writes in between.

    After this 3-byte sequence is sent, you can Read the value of STATUS register (0x05) bit 7 to confirm that FSEAL=1b.
  • 0 in reply to Brian Berner
    TI__Mastermind 30280 points
    Note that the TPS65218D0 is a functional equivalent to the TPS65218 (-B1 version) and will eventually replace the -B1 version which is now set to NRND status.

    The -D0 version only resolves issues highlighted in the Revision History of the TPS65218 datasheet and does not add or remove any features.

    Although the TPS65218 -B1 version is acceptable in most cases where an AC-DC adapter is used as the primary power supply (VSYS = 5V), it is advisable to switch to the -D0 version at your earliest convenience. The -B1 version would be less appropriate in battery-powered applications (VSYS = VBAT) when the battery voltage is low, because the buck-boost (DCDC4) can trigger a system re-boot due to the voltage being outside the tight voltage monitoring range. As mentioned before, all limitations of the -B1 device are listed in the datasheet in Revision History and the Electrical Characteristics.
  • 0 in reply to Brian Berner
    Intellectual 680 points

    Hi Brian,

    Thanks for your response and sorry for the delay.

    Can we know the supply current required for this CC pin when it is not used to supply L5/L6 and when it is
    supplying L5/L6 (2 cases) ? We are using 3V coin cell battery.

    Regards,
    Madhusoodana Bairy

  • 0 in reply to Madhusoodana Bairy6
    TI__Mastermind 30280 points

    Madhusoodana Bairy,

    There are 2 specs in the datasheet that may be helpful you:

    IOFF = 5 uA typical (OFF state current, total current into IN_BIAS, IN_DCDCx, IN_LDO1, IN_LSx, IN_BU - VIN = 3.6 V; All rails disabled. TJ = 0°C to 85°C)

    This is for when VIN is available in addition to CC coin-cell, and AC_DET and PB_IN pins must be pulled up to VIN to achieve this target. I have measured 1uA on a small sample size of devices. VIN can be from 5V bus or line power, or VIN can be a large Li-Ion battery pack.

    IQ, DCDC5/6 =  350 nA typical (Average current into CC pin; RECOVERY or OFF state; VIN_BU = 0 V; VCC = 2.4 V; DCDC5 and DCDC6 enabled, no load TJ = 25°C), datasheet page 13

    This is for when VIN is removed and CC is the only available supply, with FSEAL = 1b

    Madhusoodana Bairy6 said:
    CC pin when it is not used to supply L5/L6 and when it is supplying L5/L6 (2 cases) ?

    The Quiescent current, IQ, is only specified for when DCDC5/6 are enabled at no load. When a load is applied, the current of the load needs to be added to IQ to determine the current into the CC pin. You can estimate the efficiency of DCDC5 = 77%, DCDC6 = 87% (datasheet page 96, Figure 6-8).

  • 0 in reply to Brian Berner
    Intellectual 680 points

    Hi Brian,

    Thanks for your response and sorry for the delay.

    Just a clarification. Whether this TPS65218 has RTC inside it (like how CPUs will be having) ?

    Regards,
    Madhusoodana Bairy

  • 0 in reply to Madhusoodana Bairy6
    TI__Mastermind 30280 points

    Madhusoodana Bairy,

    The TPS65218 (or TPS65218D0) does not have an RTC inside it. The TPS65218 only provides a voltage for the RTC of the processor.

    The TPS65910 is the only PMIC that has a built in RTC. It is not common to include the Oscillator and RTC-counting digital block inside a PMIC.

    Thanks,

    Brian

  • 0 in reply to Brian Berner
    Intellectual 680 points

    Hi Brian,

    Thanks for your response.

    We are trying to measure current drawn by the PMIC from the coin cell, by enabling FSEAL bit to 1. We saw that LS3ILIM[1:0] bits are used to set current limit for LS3 of the PMIC (by the way we are using LS3's output for charging coin cell). But whether this is input current for LS3 or output current from LS3 ? There is no info. in datasheet on this.

    Please find the attached circuit section for any reference.

    Regards,
    Madhusoodana Bairy

  • 0 in reply to Madhusoodana Bairy6
    TI__Mastermind 30280 points

    Madhusoodana Bairy,

    LS3 is a simple load switch: input current and output current are equal, ILS3,IN = ILS3,OUT


    When you are charging the coin cell, the PMIC must be in the ACTIVE or SUSPEND state with the main power supply available because I2C communication needs to be active (see Figure 5-34. Modes of Operation Diagram in the TPS65218D0 datasheet on page 47 for details). The quiescent current of the load switch is not specified, but it is negligible when the main power supply is available.

    Best Regards,,

    Brian

  • 0 in reply to Brian Berner
    Intellectual 680 points

    Hi Brian,

    Thanks for your response.

    OK. Since it is a battery, whatever current we set battery will try to consume the same. So, minimum current is 100mA but the coin cell charging current is max 3mA (we are using ML2020). Am I missing something here ??

    Regards,
    Madhusoodana Bairy

  • 0 in reply to Madhusoodana Bairy6
    TI__Mastermind 30280 points
    Madhusoodana Bairy,

    The current limit setting is a maximum value. These numbers only apply to when the load switch would shut itself off due to over-current. If you set LS3ILIM[1:0] = 00b this means the the maximum current that will flow through the load switch is ideally 100mA, and the min/max values are tolerances of this value.

    A single device could possibly shut off LS3 at 98mA, or 2mA to early, but most of the devices will shut off LS3 around the center-point of a normally distributed curve, (98+126)/2 = 112 mA.

    A battery, like most real-word loads, will only consume the amount of current needed. I cannot comment on the behavior of ML2020 battery, but if the max current is 3mA then the load switch will never detect an over-current condition and it will not shut off (open the switch).

    The best suggestion I can make is that you can test your system to understand if/how it will work, and the best way to test the PMIC portion of the system is with a TPS65218EVM-100.

    The EVM ships with TPS65218 (-B1 silicon) currently, and if you want to test TPS65218D0 you will need to order free samples and replace the IC on the PCB.

    For testing LS3 with 100mA current limit, the -B1 silicon will work correctly.
  • 0 in reply to Brian Berner
    Intellectual 680 points

    Hi Brian,

    Thanks for your response.

    One more query on DCDC2 settings:
    We are trying to set 1.1V on L2 output through DCDC2 register (0x17). For this, we are writing 19h (corresponding value for 1.1V) in bits 0-5 of the register, but when we read it is not 19h but varying (and voltage too). What could be the possible reason ?
    Also, 1. whether we need to set PFM mode (bit 7) ?
          2. whether we need to use SLEW, GODSBL & GO fields in SLEW register (0x1A) ?

    Best Regards,
    Madhusoodana Bairy

  • 0 in reply to Madhusoodana Bairy6
    TI__Mastermind 30280 points

    Madhusoodana Bairy,

    I am confused, because the default value of DCDC2 output voltage is already 1.1V and the 8-bit value in Reg. 0x17 is 0x99 when I turn on the TPS65218 device.

    The MSB is 1b for Auto-PFM Enabled, and the 6 least significant bits are 01 1001b (0x19) which translates to 1.1V

    If I wanted to change DCDC2 from 1.1V to 1.2V, for example, then I need to do one of the two following procedures:

    Procedure A

    1. Write 0x6B to PASSWORD register (0x10), where 0x6A = 0x17 XOR'd with 0x7D
    2. Write 0xA3 to DCDC2 Register (0x17) to keep Auto-PFM enabled, or 0x23 to force PWM
    3. Write 0x67 to PASSWORD register (0x10), where 0x6A = 0x1A XOR'd with 0x7D
    4. Write 0x86 to SLEW Register (0x1A) to set the GO bit to 1b
    5. Read back Reg. 0x1A and it will contain data 0x06, because the GO bit it auto-cleared 

    Here, the voltage of DCDC2 changes after step 4 and the entire process must be repeated any time DCDC1 or DCDC2 voltage is modified.

    OR

    Procedure B

    1. Write 0x67 to PASSWORD register (0x10), where 0x6A = 0x1A XOR'd with 0x7D
    2. Write 0x46 to SLEW Register (0x1A) to set the GODSBL bit to 1b
    3. Read back Reg. 0x1A and it will contain data 0x46, because the GODSBL bit does not clear 
    4. Write 0x6B to PASSWORD register (0x10), where 0x6A = 0x17 XOR'd with 0x7D
    5. Write 0xA3 to DCDC2 Register (0x17) to keep Auto-PFM enabled, or 0x23 to force PWM

    Here, the voltage of DCDC2 changes after step 5 but steps 1-3 can be skipped to modify the voltage DCDC2 again. DCDC1 and DCDC2 voltage can be changed repeatedly without writing to register 0x1A again. The GODSBL bit will not clear until the PMIC loses power and the Register Map values are reset.

  • 0 in reply to Brian Berner
    Intellectual 680 points

    Hi Brian,

    Thanks for your response.

    We have tried both the above procedures and it is not working in both the cases.

    Issue is that, GO bit is not auto-clearing (& not clearing too if we try to clear forcefully). So, as in datasheet, it is varying from 0.93V to 1.24V (state for 1h). Please suggest.

    Best Regards,
    Madhusoodana Bairy

  • 0 in reply to Madhusoodana Bairy6
    TI__Mastermind 30280 points
    Madhusoodana Bairy,

    The procedure I have described above is the correct procedure for changing the voltage on DCDC1 and DCDC2 because I typed it while testing on an EVM. You should also be able to reproduce this test on the TPS65218EVM-100 using the IPG-UI, which will automatically send the Password for you.

    Then, you can compare the results on the EVM to the results on your PCB and continue to debug the issue.


    Unless you provide Scope Shots showing the issue occurring and a data log of I2C transactions (showing the commands being sent and a Register Dump of the TPS65218 register map after the commands are completed), I cannot provide any further assistance.
  • 0 in reply to Brian Berner
    Intellectual 680 points

    Hi Brian,

    I am struck with some other issues & were not able to test again. Hopefully I can check this in coming week and update on the same.

    Best Regards,

    Madhusoodana Bairy

  • 0 in reply to Madhusoodana Bairy6
    TI__Mastermind 30280 points
    Madhusoodana Bairy,


    This thread already covers a couple different topics and it appears you will be working on a couple other items before working on this again. It would be very helpful if you can mark one of the replies as a Verified Answer to your original question.

    You can continue your follow-up questions by posting new threads and they will be assigned to me. You can even say you want to "Ask a Related Question" and it will link to here.

    I will mark this Thread as Closed.

    Thanks,
    Brian
  • 0 in reply to Brian Berner
    Intellectual 680 points

    Hi Brian,

    I could not see the the option 'Verified Answer'. However, I have selected 'This resolved my issue' while replying to this.

    I hope this is ok.

    Best Regards,
    Madhusoodana Bairy