BQ25155: Want to know watchdog chars and behaviors

Hi Koki-san, 

Below the answers to your questions: 

• Q.1: The min and typical values are not stated as they don't really matter. You need to perform a communication in 14s or less after VIN plug-in, in order for the 14s-watchdog timer to be met. Any values less than 14s is okay. This is a typo and should be 14s and not 15s. 
• Q.2.1: The time of the hardware reset will depend on the AUTOWAKE configuration of the charger. This could be set on the ICCTRL0 Register (0x35). 
• Q2.2.: Yes, if there is a hardware reset, all registers will reset to default. 
• Q3.1: If the HWRESET_14S_WD is set to 1. (default is zero) Then, the device will do a HW reset if not I2C transaction is done within 14 s after VIN is present. This setting has not effect while VIN is not present.  
• Q3.2: There is only a WATCHDOG_14S_ENABLE = 1, the 15 is a typo on the datasheet. This could be enable on ICCTRL2 Register (0x37). 
• Q4: The 50-s software watchdog will work without VIN and could be disable on CHARGERCTRL0 Register (0x17). 
• Q5: For the HW watchdog, this is only for the first 14s after a valid VIN is plugged in. It'll be valid for eternity (or until disable), but check once after VIN is valid. In the case of a hardware reset all registers will set to default, which will restore the WATCHDOG_14S_WD to zero and it'll need to get re-enabled. The SW-watchdog on the other hand if enable, will require a communication every 50-s for as long as active. 
• Q6: If there is not I2C within 14-s after VIN plug in, the part will perform a hardware reset, which include a PMIC power cycle. On a HW-watchdog flag on FLAG3 Register (0x06) will be clear. The FLAG3 Watchdog Fault Flag will be active only when a SW-watchdog is expired. There is not need to do anything, as the reset will restore the device to it's default state after the HW reset. 

A few more things: the customer could disable both the 50-s SW Watchdog and the 14-S HW Watchdog timer, if not needed as part of the operation. Both watchdog are there to make sure the MCU host controller is still responsive and have not stopped operating, if the watchdog timer is not met the charger perform either a SW or HW reset in order to re-initialized a stopped system. Let us know if you have any further questions. 

Best regards, 

Arelis G. Guerrero 

Hi Arelis-san,

Thank you for your kind.

I want to ask about following things. Could you confirm the text which is written in purple?

All - There are no words for WATCHDOG_15S_ENABLE or WATCHDOG_14S_ENABLE.

Was this meaning for HWRESET_14S_WD? If so, this may be typo, therefore, please fix as "HWRESET_14S_WD" and 15s to 14s.

I understood that 15s is typo and 14s is correct.

• Q.1: The min and typical values are not stated as they don't really matter. You need to perform a communication in 14s or less after VIN plug-in, in order for the 14s-watchdog timer to be met. Any values less than 14s is okay. This is a typo and should be 14s and not 15s. 
• -I understood that 15s is typo and 14s is correct.
• 
• Which is correct for A, B or C?
• -If C is correct, what will be occur when  HW reset watchdog timer was occurred between A and just before C?
• What I wanted to ask you was 14.000000000000000....s was just sharply? Are there any error rate?
• Q.2.1: I wanted to ask you for this time.
• 
• Q2.2.: For the Q2.1 cases, will it be default, too?
• Q3.1: Solved 
• Q3.2: Solved if that is HWRESET_14S_WD.
• Q4: Solved
• Q5:For the HW watchdog, this is only for the first 14s after a valid VIN is plugged in. It'll be valid for eternity (or until disable← What is the meaning of disable?), but check once after VIN is valid. In the case of a hardware reset all registers will set to default, which will restore the HWRESET_14S_WD to zero (I think the reset is 1b0) and it'll need to get re-enabled. The SW-watchdog on the other hand if enable, will require a communication every 50-s for as long as active. 
• Q6: If there is not I2C within 14-s after VIN plug in, the part will perform a hardware reset, which include a PMIC power cycle. On a HW-watchdog flag on FLAG3 Register (0x06) will be clear. The FLAG3 Watchdog Fault Flag will be active only when a SW-watchdog is expired. There is not need to do anything, as the reset will restore the device to it's default state after the HW reset. -Is it possible to refer to PMID although it is under HW reset or system down? 

I am so sorry to rush you, but could you answer those questions soon?

Hi Koki-san, 

Koki Tsushima said:

There are no words for WATCHDOG_15S_ENABLE or WATCHDOG_14S_ENABLE.

Was this meaning for HWRESET_14S_WD? If so, this may be typo, therefore, please fix as "HWRESET_14S_WD" and 15s to 14s.

Yes, the HWRESET_14S_WD is the same as WATCHDOG_14S_ENABLE. And also the 15s is 14s. I apologize for the D/S typos, we will fix them on the next release of the datasheet. 

Koki Tsushima said:

• Which is correct for A, B or C?
• -If C is correct, what will be occur when  HW reset watchdog timer was occurred between A and just before C?

I am not 100% sure I am following the diagram. As long as there is an I2C communication in less than 14s the part will not perform the HW Reset. There is some variations on the time. I understand you are looking for an accuracy answer, but for the customer application, does it makes a difference if is 14.000001 or 13.99999s? I will suggest if the function is active to do it before the threshold (let say 13.5s or less). Keep in mind this function is disable by default. 

Koki Tsushima said:

• Q.2.1: I wanted to ask you for this time.

Yes, that'll be the AUTOWAKE time. The time it takes to reset after a hardware reset. You can configure that as mentioned on first reply. Default is 1.2s. 

Koki Tsushima said:

Q2.2.: For the Q2.1 cases, will it be default, too?

Yes, every hardware or software reset will restore the registers to default values. 

Koki Tsushima said:

Q5:For the HW watchdog, this is only for the first 14s after a valid VIN is plugged in. It'll be valid for eternity (or until disable← What is the meaning of disable?), but check once after VIN is valid. In the case of a hardware reset all registers will set to default, which will restore the HWRESET_14S_WD to zero (I think the reset is 1b0) and it'll need to get re-enabled. The SW-watchdog on the other hand if enable, will require a communication every 50-s for as long as active. 

By disable I mean the HWRESET_14S_WD = 0 (default value). This function is disable by default, if the customer wants to enable it they need to set the HWRESET_14S_WD = 1 (enable). 

Koki Tsushima said:

Q6: If there is not I2C within 14-s after VIN plug in, the part will perform a hardware reset, which include a PMIC power cycle. On a HW-watchdog flag on FLAG3 Register (0x06) will be clear. The FLAG3 Watchdog Fault Flag will be active only when a SW-watchdog is expired. There is not need to do anything, as the reset will restore the device to it's default state after the HW reset. -Is it possible to refer to PMID although it is under HW reset or system down? 

Can you expand more on this question: what do you mean by refer to PMID? 

Best regards, 

Arelis G. Guerrero 

Hi Guerrero-san,

Thank you for your reply.

Q.1 Yes, I want to ask about the accuracy.

      I am so sorry but I am not familiar with use case, but he wants to know the accuracy.

      I want to confirm again but is this max 14s, not for 15s?

      Is it OK to think the min is 13.5s? 

Q.2.1&.Q2.2 Is this meaning that they should be default when PMID was powered-off, therefore that time should be for 1.2s (because this is default).

Is this understanding correct?

Q.5 I think the default of WATCHDOG_14S_WD is "1b0", not 0. Is this correct?

Q.6 I want to ask you the meaning of PMIC. There are no words on the datasheet. Was it not Power Management IC, right?

Thank you a lot.

Koki

Hi Koki-san, 

Koki Tsushima said:

  Is it OK to think the min is 13.5s? 

Let me clarify. The maximum is 14s, you can say the maximum is 13.5s instead if you want to make sure you are on a safe area of the threshold. The minimum is any value less than 14s. In other words, if the I2C happens at 1s that would abort the HW reset. Also if it happens at 500ms, or 5s or 13.5s. The customer have 14s or less to perform an I2C transaction after power good. 

Koki Tsushima said:

Q.2.1&.Q2.2 Is this meaning that they should be default when PMID was powered-off, therefore that time should be for 1.2s (because this is default).

Is this understanding correct?

If the AUTOWAKE field on register ICCTRL0 (0x35), is not changed by the MCU controller. Then yes, the time will be 1.2s for reset. The user can configure this timer, so it could vary based on how is configured. 

Koki Tsushima said:

Q.6 I want to ask you the meaning of PMIC. There are no words on the datasheet. Was it not Power Management IC, right?

The word should be PMID. This is the mid-point of the high-side FET of the power path devices, such as the BQ25155. This is normally where the customer will connect their system. You can refer to Section 8.2 of the D/S for the functional block diagram. 

Best regards, 

Arelis G. Guerrero 

Hi Guerrero-san,

Thank you for your reply.

Q.1 I understood that max is 14s and 15s typo which fill be fixed for datasheet. 

      Therefore, if the I2C happens at 14.0000001s that would not abort the HW reset because the max is 14s, is this right?     

      And I understood the The minimum is any value less than 14s. So the min should be 0s, is this right?

      Was 13.5s is just idea, but not calc. by you as a safe range, is this right?

      I am sorry for troublesome questions.

Q.2 I got it.

What is the meaning of MCU?

Did you mean the case when customer changed the ICCTRL0 (0x35) by external MCU (this is Host) to other address?

If so, I think ICCTRL0 (0x35) should be default when PMID was powered-off, therefore, it does not matter. Is this not true?

Thank you for your kind.

Koki