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BQ24160: USB chargers can repeatedly start and stop charging and IC getting in locked state

Raphael Cherney
Prodigy 50 points
Part Number: BQ24160
Other Parts Discussed in Thread: TUSB320

We are seeing strange behavior with the BQ24160 from certain off-the-shelf USB and USB-C chargers (the product uses a USB-C Configuration Channel controller similar to the TUSB320). The BQ24160 will detect that there is 5V on the USB input and begin charging. However, after 60-80 ms it will suddenly stop charging and then start again. The Status/Control Register alternates indefinitely between "USB Ready" and "Charging from USB" at a rate of 7 times per second or more (each "charge" lasts 60-80ms). With some chargers we do not see this behavior and the charge proceeds normally. We have tried nearly every register configuration to try and fix the issue as well as adding additional capacitance to the USB input and SYS output for stability. In some cases, reducing the charge current can fix the issue -- though we have to reduce the charge current to levels too low for our design.
Importantly, we have also seen many cases where the BQ24160 seems to get into a locked state where it stops reacting to power inputs (DRV output stays low and Status/Control Register shows no valid source). We are still able to communicate with the chip, but it doesn't sense the charging input or begin charging. Toggling the RESET bit or CD line are unable to recover the BQ24160. The only way to make the system responsive again is to remove and reconnect the battery (as the chip is powered directly from the battery). This is particularly problematic as our product does not have a removable battery. What could cause the internal state machine get stuck like this? Are there ways to recover?
  • 0
    TI__Guru**** 167286 points
    Hi Raphael,

    Can you send scope plots (one zoomed out showing at least 2 pulses and one zoomed in showing detail) of the pulse charge behavior described above including V(USB), V(BAT), V(SYS) and I(inductor)? If not I(inductor) then V(SW)? How are the D+/D- lines configured? Can you send the I2C register values during the pulsed charge behavior and the locked state?
  • 0 in reply to Jeff F
    Prodigy 50 points

    Hi Jeff,

    I’ve attached some oscilloscope screenshots for the nets that you mentioned (signal on channel 1). In all of them, channel 2 (in blue) is showing the INT output (which pulls low during charging). The D+/D- lines are connected to the USB-C connector which in turn goes to the charger (they are also connected to MCU pins configured as high-impedance inputs). The I2C register values are as follows:

    Locked fault state with our charge parameters:

    [0] 0b00001110

    [1] 0b11110001

    [2] 0b11001100

    [3] 0b10000000

    [4] 0b01000101

    [5] 0b00000010

    [6] 0b00111111

    [7] 0b01011000

    Locked fault state after reset command:

    [0] 0b00000110

    [1] 0b11110000

    [2] 0b11001100

    [3] 0b00010100

    [4] 0b01000101

    [5] 0b00110010

    [6] 0b00000000

    [7] 0b00011000

    V(BAT):

    V(USB):

    V(SYS):

    V(SW):

  • 0 in reply to Raphael Cherney
    TI__Guru**** 167286 points
    Raphael,

    I have a few questions. Why is EN_NOBATOP bit (REG01B0) high? If a battery is attached, this bit is typically low. How is V(SW) close to 8V? When operating normally, the buck converter high side switch connects USB to SW so V(SW) should never be higher than V(USB), excluding ringing.
  • 0 in reply to Jeff F
    Prodigy 50 points

    EN_NOBATOP was set high from trying to test various configuration settings. I have confirmed that the behavior is the same with EN_NOBATOP set low (which it should normally be). I also checked V(SW) again and I think the issue you noted was more around bad grounding during the measurement. Here you can see V(SW) in yellow and V(USB) in blue.

  • 0 in reply to Raphael Cherney
    TI__Guru**** 167286 points

    Can you send your schematic, along with inductor part number? 

  • 0 in reply to Jeff F
    Prodigy 50 points
    I shared the requested information through a private message.
  • 0 in reply to Raphael Cherney
    TI__Guru**** 167286 points
    I got it, thanks. I don't seen any issues with the schematic, other then only 10uF on SYS. I assume there is additional capacitance on that rail somewhere else on the schematic?

    Can you disconnect from the USB-C circuits and power the charger directly from a known power supply or maybe from the IN power supply?
  • 0 in reply to Jeff F
    Prodigy 50 points
    I disconnected the USB-C circuits (with no effect) and saw very similar unstable behavior when charging with the IN supply. However, upon further review, it appears that we are missing the 1uF capacitor on the DRV output. Adding this component seems to have stabilized things, but can you confirm that this would explain the behavior we were seeing?
  • 0 in reply to Raphael Cherney
    TI__Guru**** 167286 points

    Yes.  The DRV output is the output of a linear regulator that needs the 1uF for stability.  If you remove that cap and look at the voltage on oscilloscope, you will see it oscillating.