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BQ27750: Some times lost control of external FETs

Spider
Intellectual 350 points

Part Number: BQ27750

Hello!

I has build LiPo batteris packs controlled by BQ27750. It was a big mistake to use the 27750, but it’s too late to change anything.
Device work, but some times disconnect batteris from charge or from load OR from both charge and load. When I connect BQ studio to batterie pack BQ27750 says that all fine and FETs are switched on. But if I try measure resistence of external FETs - them are "closed" (switched off) and on GATE pin of FETs is around 2-3 volts. Nothing indicates this condition in BQ Studio. To make device back to life I sending Reset device command to BQ27750 from BQ Studio. And after this action all work fine again.... some time....

I have more than 2000 pcs devices with this problem. Problem became SOMETIMES. I can't find conditios of this.

What I do wrong? And how to resolve this problem?

  • 0
    TI__Genius 10370 points

    Spider,

    The bq27750 can disable the FETS for numerous reasons. If after a reset the FETS are enabled then switch to disabled this leads me to believe you are triggering a time based protection event. 

    If you want to investigate yourself, please make sure you are refreshing the registers screen in bqStudio so you can see updates as they happen. Pay specical attention to the "Protection Status" registers. 

    Please provide a log file from bqStudio and a GG file from the data memory. 

    Thanks,

    Eric Vos

  • 0 in reply to Vos
    Intellectual 350 points

    Ok. I'll make log when it happen again.

    Why voltage at Gate pins is around 2-3 volts? When FETs is off- this value is ZERO, when is on - around 12V. Why sometimes is 3v?

  • 0 in reply to Spider
    TI__Mastermind 24870 points

    Hello Spider,

    Can you provide a scope shot and also where you are measuring?

    Gate pins should be zero with respect from the gate to source (in this case pack+), can you measure that voltage? I believe if the protection FETs are off, that voltage should be zero.

  • 0 in reply to Vos
    Intellectual 350 points

    Before Reset but with Closed FETs:

    After reset and with Opened FETs (see to Log panel):

    Fullscreen xxxxx.log Download 
    Thu Apr 23 14:37:14 YEKT 2020

Device Version Info = 1750_0_04
BQZ Device Name = bq27750
BQZ Firmware Version = 0_04


Sample,DateTime,ElapsedTime,ManufAccess,@Rate(@),@TimeEmpty,Temperature,Voltage,Current,AvgCurr,AvgPow,RSOC,RemCap,FullChgCap,RunTimeEmty,AvgTimeFull,MaxLoadCurrent,MaxLoadTimeEmty,ChgCurr,ChgVolt,MaxCurr,BattStat,CycleCnt,SoH,OpStatA,OpStatB,TempRange,ChgStat,GaugeStat,ITStat,MfgStat,SafetyAlertAB,SafetyStatAB,SafetyAlertCD,SafetyStatCD,PFAlertAB,PFStatAB,PFAlertCD,PFStatCD,CellVolt1,vBAT,vPACK,CellCurr1,CellPower1,Power,IntTemp,TS1Temp,CellTemp,Cell1RawV,FltRemQ,FltRemE,FltFullChgQ,FltFullChgE,TrueRemQ,TrueRemE,InitialQ,InitialE,TrueFullChgQ,TrueFullChgE,T_sim,T_ambient,RaScale1,CompRes1,PackGrid,LStatus,CellGrid1,StateTime,DOD0_1,DOD0 Passed Q,DOD0 Passed E,DOD0 Time,DODEOC_1,QMax1,QMaxDOD0_1,QMaxPassedQ,QMaxTime,Tk,Ta,RawDOD_1,SOH_FC_Q,SOH_FC_E,LogRowTime(ms),LogStatus
1,2020-04-23 14:37:18,4.002,0x0054,0,65535,27.2,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0600,0x10,0x0002,0x45,0x1818,0x0018,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5617,0,0,0,26.9,27.2,27.2,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,27.2,1000,0,1,5,0,992,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,921,SUCCESS
2,2020-04-23 14:37:22,8.001,0x0054,0,65535,27.2,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0200,0x10,0x0002,0x45,0x1818,0x0018,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5617,0,0,0,26.9,27.0,27.2,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,27.2,1000,0,1,5,0,996,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,904,SUCCESS
3,2020-04-23 14:37:26,12.002,0x0054,0,65535,27.1,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0200,0x10,0x0002,0x45,0x1818,0x0018,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5619,0,0,0,26.9,27.0,27.1,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,27.1,1000,0,1,5,0,1000,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,881,SUCCESS
4,2020-04-23 14:37:30,16.002,0x0054,0,65535,26.9,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0200,0x10,0x0002,0x45,0x1818,0x0018,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5618,0,0,0,26.8,26.9,26.9,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.9,1000,0,1,5,0,1004,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,889,SUCCESS
5,2020-04-23 14:37:34,20.002,0x0054,0,65535,26.8,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0200,0x10,0x0002,0x45,0x1818,0x0018,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5618,0,0,0,26.7,26.8,26.8,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.8,1000,0,1,5,0,1008,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,871,SUCCESS
6,2020-04-23 14:37:38,24.003,0x0054,0,65535,26.7,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0600,0x10,0x0002,0x45,0x1818,0x0018,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5619,0,0,0,26.6,26.7,26.7,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.7,1000,0,1,5,0,1012,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,838,SUCCESS
7,2020-04-23 14:37:42,28.004,0x0054,0,65535,26.7,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0200,0x10,0x0002,0x45,0x1818,0x0018,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5619,0,0,0,26.6,26.7,26.7,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.7,1000,0,1,5,0,1016,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,887,SUCCESS
8,2020-04-23 14:37:46,32.004,0x0054,0,65535,26.7,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0200,0x10,0x0002,0x45,0x1818,0x0018,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5617,0,0,0,26.6,26.7,26.7,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.7,1000,0,1,5,0,1020,16191,-4,-1,5,824,1281,0,0,1020,0.0,16191,65532,1281,0,865,SUCCESS
9,2020-04-23 14:37:50,36.005,0x0054,0,65535,26.6,3097,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0200,0x10,0x0002,0x45,0x1818,0x0008,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3097,3097,5620,0,0,0,26.6,26.6,26.6,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.6,1000,0,1,5,0,1024,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,871,SUCCESS
10,2020-04-23 14:37:54,40.005,0x0054,0,65535,26.6,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0200,0x10,0x0002,0x45,0x1818,0x0008,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5619,0,0,0,26.5,26.6,26.6,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.6,1000,0,1,5,0,1028,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,885,SUCCESS
11,2020-04-23 14:37:58,44.005,0x0054,0,65535,26.5,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0600,0x10,0x0002,0x45,0x1818,0x000E,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5616,0,0,0,26.5,26.5,26.5,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.5,1000,0,1,5,0,1032,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,916,SUCCESS
12,2020-04-23 14:38:02,48.006,0x0054,0,65535,26.5,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0200,0x10,0x0002,0x45,0x1818,0x000E,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5616,0,0,0,26.5,26.5,26.5,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.5,1000,0,1,5,0,1036,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,865,SUCCESS
13,2020-04-23 14:38:06,52.007,0x0054,0,65535,26.5,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0200,0x10,0x0002,0x45,0x1818,0x000E,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5618,0,0,0,26.5,26.5,26.5,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.5,1000,0,1,5,0,1039,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,883,SUCCESS
14,2020-04-23 14:38:10,56.007,0x0054,0,65535,26.5,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0200,0x10,0x0002,0x45,0x1818,0x000E,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5618,0,0,0,26.4,26.5,26.5,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.5,1000,0,1,5,0,1043,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,885,SUCCESS
15,2020-04-23 14:38:14,60.008,,0,65535,26.5,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0200,0x10,0x0002,0x45,0x1818,0x0018,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5618,0,0,0,26.4,26.5,26.5,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.5,1000,0,1,5,0,1048,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,961,ERROR : Please check C:\TMP\xxxxx.log.err
16,2020-04-23 14:38:18,64.008,0x0054,0,65535,26.4,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0600,0x10,0x0002,0x45,0x1818,0x0018,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5618,0,0,0,26.4,26.4,26.4,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.5,1000,0,1,5,0,1051,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,914,SUCCESS
17,2020-04-23 14:38:22,68.008,0x0054,0,65535,26.4,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0200,0x10,0x0002,0x45,0x1818,0x0018,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5618,0,0,0,26.4,26.4,26.4,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.4,1000,0,1,5,0,1055,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,881,SUCCESS
18,2020-04-23 14:38:26,72.009,0x0054,0,65535,26.4,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0200,0x10,0x0002,0x45,0x1818,0x0018,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5617,0,0,0,26.4,26.4,26.4,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.4,1000,0,1,5,0,1059,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,880,SUCCESS
19,2020-04-23 14:38:30,76.009,0x0054,0,65535,26.4,3098,0,0,0,0,0,8218,65535,65535,-800,0,0,0,0,0x00D0,3,100,0xE900,0x0200,0x10,0x0002,0x45,0x1818,0x0018,0x0000,0x0005,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3098,3098,5618,0,0,0,26.3,26.4,26.4,3098,-344,-193,8218,3097,-344,-193,8418,3247,8218,3097,28.9,26.4,1000,0,1,5,0,1063,16191,-4,-1,5,824,9133,16191,-4,5,2.0,1000,16188,8390,3215,895,SUCCESS
20,2020-04-23 14:38:34,80.009,0x0054,0,65535,26.5,3175,1846,630,199,0,0,8221,65535,852,-800,0,900,4350,0,0x4090,3,100,0x0106,0x0000,0x10,0x0002,0x05,0x0814,0x0018,0x0004,0x0000,0x0000,0x0000,0x0000,0x0000,0x0000,0x0000,3177,3177,3192,1847,587,586,26.5,26.7,26.6,3177,-339,-192,8221,3099,-339,-192,8420,3249,8219,3099,26.3,26.3,1000,0,0,5,0,3,16181,-2,0,0,824,9133,0,-2,0,2.0,1000,16181,8390,3215,957,SUCCESS
21,2020-04-23 14:38:38,84.010,0x0054,0,65535,27.5,3183,1846,922,292,0,0,8221,65535,615,-800,0,900,4350,0,0x4090,3,100,0x4902,0x0000,0x10,0x0002,0x05,0x0814,0x0018,0x0000,0x0004,0x0000,0x0000,0x0000,0x0000,0x0000,0x0000,3141,3141,3201,463,145,440,27.1,27.7,27.7,3121,-337,-191,8221,3099,-337,-191,8420,3249,8219,3099,26.3,26.3,1000,0,0,5,0,7,16181,-4,-1,0,824,9133,0,-4,0,2.0,1000,16181,8390,3215,798,SUCCESS
22,2020-04-23 14:38:42,88.010,0x0054,0,65535,28.3,3112,0,801,254,0,0,8219,65535,616,-800,0,0,0,0,0x0090,3,100,0x4902,0x0000,0x10,0x0002,0x05,0x0814,0x0018,0x0000,0x0004,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3112,3112,5617,0,0,0,27.5,28.3,28.3,3112,-337,-191,8219,3099,-337,-191,8420,3249,8219,3099,26.3,26.3,1000,0,0,5,0,9,16181,-4,-1,0,824,9133,0,-4,0,2.0,1000,16181,8390,3215,877,SUCCESS
23,2020-04-23 14:38:46,92.011,0x0054,0,65535,28.4,3110,0,609,193,0,0,8219,65535,616,-800,0,0,0,0,0x0090,3,100,0x4902,0x0000,0x10,0x0002,0x05,0x0814,0x0018,0x0000,0x0004,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3110,3110,5618,0,0,0,27.8,28.4,28.4,3110,-337,-191,8219,3099,-337,-191,8420,3249,8219,3099,26.3,26.3,1000,0,0,5,0,9,16181,-4,-1,0,824,9133,0,-4,0,2.0,1000,16181,8390,3215,875,SUCCESS
24,2020-04-23 14:38:50,96.012,0x0054,0,65535,28.3,3109,0,462,147,0,0,8219,65535,616,-800,0,0,0,0,0x0090,3,100,0x4902,0x0000,0x10,0x0002,0x05,0x0814,0x0018,0x0000,0x0004,0x0020,0x0000,0x0000,0x0000,0x0000,0x0000,3109,3109,5617,0,0,0,27.8,28.3,28.3,3109,-337,-191,8219,3099,-337,-191,8420,3249,8219,3099,26.3,26.3,1000,0,0,5,0,9,16181,-4,-1,0,824,9133,0,-4,0,2.0,1000,16181,8390,3215,859,SUCCESS

  • 0 in reply to Spider
    TI__Genius 10370 points

    Spider,

    In the above bqStudio image you have CUV tripeed which would cause the discharge FET to turn off. in the 2nd plot it is not set, I believe you are tripping the protection which is killing the FETS.

    Thanks,

    Eric Vos

  • 0 in reply to Vos
    Intellectual 350 points

    I understand this. But how charge device when both FETs are closed?
    Be careful! At above bqStudio images Charge FET are opened, BUT in real it is Closed. You can see that on photos.
    That is my problem! :facepalm:

  • 0 in reply to Spider
    TI__Genius 10370 points

    Spider,

    this is an issue with your configuration if you are triggering a CTO and CUV. You should change CUV to recover when a charger is detected thus the CUV event will release when charging starts.

    I suspect the CTO timeout is way too low. this should be in 1000's of seconds. 

    Thanks,

    Eric Vos

  • 0 in reply to Vos
    Intellectual 350 points

    Manual control of FETs from bqStudio not work too. In GUI I see that FET is ON but in real it is closed. It is normal?

  • 0 in reply to Spider
    TI__Genius 10370 points

    Spider,

    You should not be manually controlling the FETS, but instead let the gauge do the control. You writing to manually control would not work with protection activated. 

    Thanks,

    Eric Vos

  • 0 in reply to Vos
    Intellectual 350 points

    Where you see that protection is activated? I see that Charge FET is ON on first screenshot of bqStudio. But really FET is OFF.

  • 0 in reply to Vos
    Intellectual 350 points

    Can you mark where I can see that protection is activated?

  • 0 in reply to Spider
    TI__Genius 10370 points

    Spider,

    There are registers called "Safety Status" and "PF Status" which give flags to indicate when event occured. In your plot you have OCC (over current in charge) and CUV (cell under voltage)

    Thanks,

    Eric Vos

  • 0 in reply to Vos
    Intellectual 350 points

    Any way. Why OCC flag is set even device was never charged?
    This situation occurs during discharge by load.

  • 0 in reply to Spider
    TI__Genius 10370 points

    Spider,

    There are many reasons it could be tripping. In summary the protection trips when the gauge registers current bigger than the OCC threshold current. so options i could see are

    1) Your threshold is corrupted and is a negative value (thus 0 would trip)

    2) Your calibration is very off so even at rest you are detecting current 

    3) There is a noisy signal 

    Thanks,

    Eric Vos