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BQ25638: Strange behaviour at high charge rates

Steve Carkner
Prodigy 80 points
Part Number: BQ25638
Other Parts Discussed in Thread: BQSTUDIO

Tool/software:

I am trying to recharge a battery at the maximum 5A charge rate using a 15V input, but I found the battery current reading was zero when I tried setting charge current above about 4 amps. I modified my software to gradually ramp up the current and found at at around 4A (varies, from 3950 to 4050 ish) the battery current register will suddenly read ZERO, even though an external meter attached to the battery confirms that about 2.7 amps is flowing into the battery.

So current is definitely taking a step down right around that 4 amp mark. There is enough variation (a few bits) even from run to run and product to product (I have three samples) that I think it is more hardware than software (but the fact that the chip suddenly reports 00000000 in the ADC register for battery current (which other registers still function) leads me to think that maybe I have a register set wrong.

Wtih 9V input I can get about 4250mA before it does this weird drop thing.

Here is an example run, followed by a complete register dump.

I have disabled ICO, IINPDM and ILIM.

I have added a snubber circuit (22 ohm + 3nF and also tried 10nF).

I have increased capacitance on Vmid, Vbat and Vsys

I have tried with both 9V and 15V input using USB and an extnernal power supply

Any guidance or ideas on what to try next would be greatly appreciated. I will continue experiments and post updates.

0 : 30 avg_vbat: 3604 vbat: 3622 vbus: 15050 avg_ibat: 2493 mA ibat: 2770 mA ibus: 812 mA SOC: 23 % TDIE: 48.5 C VSYS: 3686.25 mV Chg_req: 2880 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 30 avg_vbat: 3605 vbat: 3626 vbus: 15050 avg_ibat: 2514 mA ibat: 2810 mA ibus: 827 mA SOC: 23 % TDIE: 48.5 C VSYS: 3690.0 mV Chg_req: 2900 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 30 avg_vbat: 3607 vbat: 3627 vbus: 15050 avg_ibat: 2534 mA ibat: 2830 mA ibus: 832 mA SOC: 23 % TDIE: 49.0 C VSYS: 3692.5 mV Chg_req: 2920 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 30 avg_vbat: 3608 vbat: 3627 vbus: 15050 avg_ibat: 2554 mA ibat: 2840 mA ibus: 835 mA SOC: 23 % TDIE: 49.0 C VSYS: 3695.0 mV Chg_req: 2940 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 31 avg_vbat: 3609 vbat: 3628 vbus: 15050 avg_ibat: 2573 mA ibat: 2845 mA ibus: 837 mA SOC: 23 % TDIE: 49.0 C VSYS: 3695.0 mV Chg_req: 2960 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 31 avg_vbat: 3611 vbat: 3632 vbus: 15050 avg_ibat: 2593 mA ibat: 2890 mA ibus: 850 mA SOC: 23 % TDIE: 49.5 C VSYS: 3698.75 mV Chg_req: 2980 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 31 avg_vbat: 3612 vbat: 3633 vbus: 15050 avg_ibat: 2614 mA ibat: 2910 mA ibus: 857 mA SOC: 23 % TDIE: 50.0 C VSYS: 3700.0 mV Chg_req: 3000 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 31 avg_vbat: 3614 vbat: 3635 vbus: 15050 avg_ibat: 2633 mA ibat: 2920 mA ibus: 860 mA SOC: 23 % TDIE: 50.0 C VSYS: 3701.25 mV Chg_req: 3020 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 32 avg_vbat: 3615 vbat: 3635 vbus: 15050 avg_ibat: 2652 mA ibat: 2925 mA ibus: 860 mA SOC: 24 % TDIE: 50.0 C VSYS: 3701.25 mV Chg_req: 3040 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 32 avg_vbat: 3616 vbat: 3637 vbus: 15050 avg_ibat: 2672 mA ibat: 2970 mA ibus: 872 mA SOC: 24 % TDIE: 50.5 C VSYS: 3705.0 mV Chg_req: 3060 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 32 avg_vbat: 3618 vbat: 3638 vbus: 15050 avg_ibat: 2693 mA ibat: 2990 mA ibus: 880 mA SOC: 24 % TDIE: 51.0 C VSYS: 3707.5 mV Chg_req: 3080 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 32 avg_vbat: 3619 vbat: 3638 vbus: 15050 avg_ibat: 2712 mA ibat: 3005 mA ibus: 882 mA SOC: 24 % TDIE: 51.0 C VSYS: 3708.75 mV Chg_req: 3100 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 33 avg_vbat: 3621 vbat: 3640 vbus: 15050 avg_ibat: 2731 mA ibat: 3010 mA ibus: 885 mA SOC: 24 % TDIE: 51.0 C VSYS: 3708.75 mV Chg_req: 3120 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 33 avg_vbat: 3622 vbat: 3642 vbus: 15045 avg_ibat: 2752 mA ibat: 3050 mA ibus: 897 mA SOC: 24 % TDIE: 51.5 C VSYS: 3712.5 mV Chg_req: 3140 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 33 avg_vbat: 3623 vbat: 3645 vbus: 15045 avg_ibat: 2772 mA ibat: 3070 mA ibus: 902 mA SOC: 24 % TDIE: 51.5 C VSYS: 3713.75 mV Chg_req: 3160 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 33 avg_vbat: 3625 vbat: 3646 vbus: 15045 avg_ibat: 2792 mA ibat: 3080 mA ibus: 905 mA SOC: 24 % TDIE: 52.0 C VSYS: 3715.0 mV Chg_req: 3180 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 34 avg_vbat: 3626 vbat: 3646 vbus: 15045 avg_ibat: 2811 mA ibat: 3085 mA ibus: 907 mA SOC: 24 % TDIE: 52.0 C VSYS: 3715.0 mV Chg_req: 3200 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 34 avg_vbat: 3628 vbat: 3648 vbus: 15045 avg_ibat: 2831 mA ibat: 3130 mA ibus: 922 mA SOC: 24 % TDIE: 52.5 C VSYS: 3720.0 mV Chg_req: 3220 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 34 avg_vbat: 3629 vbat: 3650 vbus: 15045 avg_ibat: 2852 mA ibat: 3150 mA ibus: 927 mA SOC: 24 % TDIE: 53.0 C VSYS: 3722.5 mV Chg_req: 3240 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 34 avg_vbat: 3630 vbat: 3650 vbus: 15045 avg_ibat: 2872 mA ibat: 3160 mA ibus: 932 mA SOC: 24 % TDIE: 53.0 C VSYS: 3723.75 mV Chg_req: 3260 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 35 avg_vbat: 3632 vbat: 3650 vbus: 15040 avg_ibat: 2891 mA ibat: 3165 mA ibus: 932 mA SOC: 24 % TDIE: 53.0 C VSYS: 3723.75 mV Chg_req: 3280 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 35 avg_vbat: 3633 vbat: 3652 vbus: 15040 avg_ibat: 2911 mA ibat: 3215 mA ibus: 945 mA SOC: 24 % TDIE: 53.5 C VSYS: 3726.25 mV Chg_req: 3300 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 35 avg_vbat: 3634 vbat: 3653 vbus: 15035 avg_ibat: 2932 mA ibat: 3235 mA ibus: 952 mA SOC: 24 % TDIE: 53.5 C VSYS: 3728.75 mV Chg_req: 3320 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 35 avg_vbat: 3636 vbat: 3655 vbus: 15035 avg_ibat: 2952 mA ibat: 3240 mA ibus: 955 mA SOC: 24 % TDIE: 54.0 C VSYS: 3728.75 mV Chg_req: 3340 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 36 avg_vbat: 3637 vbat: 3655 vbus: 15035 avg_ibat: 2971 mA ibat: 3245 mA ibus: 957 mA SOC: 24 % TDIE: 54.0 C VSYS: 3730.0 mV Chg_req: 3360 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 36 avg_vbat: 3638 vbat: 3657 vbus: 15030 avg_ibat: 2991 mA ibat: 3285 mA ibus: 970 mA SOC: 24 % TDIE: 54.5 C VSYS: 3732.5 mV Chg_req: 3380 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 36 avg_vbat: 3640 vbat: 3658 vbus: 15030 avg_ibat: 3012 mA ibat: 3305 mA ibus: 975 mA SOC: 24 % TDIE: 55.0 C VSYS: 3733.75 mV Chg_req: 3400 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 36 avg_vbat: 3641 vbat: 3658 vbus: 15030 avg_ibat: 3031 mA ibat: 3315 mA ibus: 977 mA SOC: 24 % TDIE: 55.0 C VSYS: 3735.0 mV Chg_req: 3420 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 37 avg_vbat: 3642 vbat: 3658 vbus: 15030 avg_ibat: 3050 mA ibat: 3320 mA ibus: 980 mA SOC: 25 % TDIE: 55.5 C VSYS: 3735.0 mV Chg_req: 3440 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 37 avg_vbat: 3643 vbat: 3661 vbus: 15025 avg_ibat: 3071 mA ibat: 3365 mA ibus: 995 mA SOC: 25 % TDIE: 56.0 C VSYS: 3738.75 mV Chg_req: 3460 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 37 avg_vbat: 3645 vbat: 3662 vbus: 15025 avg_ibat: 3091 mA ibat: 3385 mA ibus: 1000 mA SOC: 25 % TDIE: 56.0 C VSYS: 3741.25 mV Chg_req: 3480 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 37 avg_vbat: 3646 vbat: 3662 vbus: 15020 avg_ibat: 3111 mA ibat: 3395 mA ibus: 1002 mA SOC: 25 % TDIE: 56.5 C VSYS: 3742.5 mV Chg_req: 3500 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 38 avg_vbat: 3647 vbat: 3663 vbus: 15020 avg_ibat: 3130 mA ibat: 3405 mA ibus: 1002 mA SOC: 25 % TDIE: 56.5 C VSYS: 3742.5 mV Chg_req: 3520 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 38 avg_vbat: 3648 vbat: 3666 vbus: 15020 avg_ibat: 3150 mA ibat: 3445 mA ibus: 1017 mA SOC: 25 % TDIE: 57.0 C VSYS: 3746.25 mV Chg_req: 3540 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 38 avg_vbat: 3650 vbat: 3667 vbus: 15020 avg_ibat: 3171 mA ibat: 3465 mA ibus: 1025 mA SOC: 25 % TDIE: 57.0 C VSYS: 3747.5 mV Chg_req: 3560 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 38 avg_vbat: 3651 vbat: 3667 vbus: 15020 avg_ibat: 3190 mA ibat: 3475 mA ibus: 1027 mA SOC: 25 % TDIE: 57.5 C VSYS: 3748.75 mV Chg_req: 3580 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 39 avg_vbat: 3652 vbat: 3667 vbus: 15015 avg_ibat: 3209 mA ibat: 3480 mA ibus: 1030 mA SOC: 25 % TDIE: 57.5 C VSYS: 3748.75 mV Chg_req: 3600 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 39 avg_vbat: 3653 vbat: 3670 vbus: 15010 avg_ibat: 3229 mA ibat: 3525 mA ibus: 1042 mA SOC: 25 % TDIE: 58.0 C VSYS: 3752.5 mV Chg_req: 3620 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 39 avg_vbat: 3654 vbat: 3671 vbus: 15010 avg_ibat: 3250 mA ibat: 3545 mA ibus: 1047 mA SOC: 25 % TDIE: 58.5 C VSYS: 3753.75 mV Chg_req: 3640 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 39 avg_vbat: 3655 vbat: 3671 vbus: 15010 avg_ibat: 3269 mA ibat: 3555 mA ibus: 1050 mA SOC: 25 % TDIE: 58.5 C VSYS: 3753.75 mV Chg_req: 3660 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 40 avg_vbat: 3657 vbat: 3671 vbus: 15010 avg_ibat: 3288 mA ibat: 3560 mA ibus: 1052 mA SOC: 25 % TDIE: 58.5 C VSYS: 3755.0 mV Chg_req: 3680 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 40 avg_vbat: 3658 vbat: 3675 vbus: 15005 avg_ibat: 3308 mA ibat: 3605 mA ibus: 1065 mA SOC: 25 % TDIE: 59.0 C VSYS: 3758.75 mV Chg_req: 3700 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 40 avg_vbat: 3659 vbat: 3676 vbus: 15005 avg_ibat: 3329 mA ibat: 3635 mA ibus: 1072 mA SOC: 25 % TDIE: 59.5 C VSYS: 3760.0 mV Chg_req: 3720 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 40 avg_vbat: 3660 vbat: 3676 vbus: 15005 avg_ibat: 3349 mA ibat: 3640 mA ibus: 1075 mA SOC: 25 % TDIE: 59.5 C VSYS: 3761.25 mV Chg_req: 3740 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 41 avg_vbat: 3661 vbat: 3677 vbus: 15005 avg_ibat: 3368 mA ibat: 3645 mA ibus: 1077 mA SOC: 25 % TDIE: 60.0 C VSYS: 3761.25 mV Chg_req: 3760 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 41 avg_vbat: 3662 vbat: 3680 vbus: 15005 avg_ibat: 3388 mA ibat: 3685 mA ibus: 1092 mA SOC: 25 % TDIE: 60.5 C VSYS: 3765.0 mV Chg_req: 3780 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 41 avg_vbat: 3663 vbat: 3681 vbus: 15005 avg_ibat: 3409 mA ibat: 3705 mA ibus: 1097 mA SOC: 25 % TDIE: 60.5 C VSYS: 3766.25 mV Chg_req: 3800 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 41 avg_vbat: 3665 vbat: 3682 vbus: 15005 avg_ibat: 3428 mA ibat: 3715 mA ibus: 1100 mA SOC: 25 % TDIE: 61.0 C VSYS: 3767.5 mV Chg_req: 3820 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 42 avg_vbat: 3666 vbat: 3682 vbus: 15005 avg_ibat: 3447 mA ibat: 3720 mA ibus: 1102 mA SOC: 26 % TDIE: 61.5 C VSYS: 3767.5 mV Chg_req: 3840 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 42 avg_vbat: 3667 vbat: 3685 vbus: 15005 avg_ibat: 3467 mA ibat: 3760 mA ibus: 1117 mA SOC: 26 % TDIE: 61.5 C VSYS: 3771.25 mV Chg_req: 3860 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 42 avg_vbat: 3668 vbat: 3686 vbus: 15000 avg_ibat: 3488 mA ibat: 3780 mA ibus: 1127 mA SOC: 26 % TDIE: 62.0 C VSYS: 3772.5 mV Chg_req: 3880 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 42 avg_vbat: 3669 vbat: 3686 vbus: 14995 avg_ibat: 3507 mA ibat: 3790 mA ibus: 1127 mA SOC: 26 % TDIE: 62.0 C VSYS: 3773.75 mV Chg_req: 3900 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 43 avg_vbat: 3670 vbat: 3686 vbus: 14995 avg_ibat: 3526 mA ibat: 3795 mA ibus: 1130 mA SOC: 26 % TDIE: 62.0 C VSYS: 3773.75 mV Chg_req: 3920 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 43 avg_vbat: 3671 vbat: 3688 vbus: 14990 avg_ibat: 3546 mA ibat: 3840 mA ibus: 1142 mA SOC: 26 % TDIE: 62.5 C VSYS: 3777.5 mV Chg_req: 3940 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 43 avg_vbat: 3673 vbat: 3690 vbus: 14990 avg_ibat: 3566 mA ibat: 3860 mA ibus: 1147 mA SOC: 26 % TDIE: 63.0 C VSYS: 3780.0 mV Chg_req: 3960 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 43 avg_vbat: 3674 vbat: 3691 vbus: 14990 avg_ibat: 3586 mA ibat: 3870 mA ibus: 1150 mA SOC: 26 % TDIE: 63.0 C VSYS: 3782.5 mV Chg_req: 3980 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 44 avg_vbat: 3675 vbat: 3691 vbus: 14990 avg_ibat: 3605 mA ibat: 3875 mA ibus: 1152 mA SOC: 26 % TDIE: 63.5 C VSYS: 3762.5 mV Chg_req: 4000 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 44 avg_vbat: 3675 vbat: 3653 vbus: 15005 avg_ibat: 3494 mA ibat: 0 mA ibus: 952 mA SOC: 26 % TDIE: 63.5 C VSYS: 3728.75 mV Chg_req: 4020 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 44 avg_vbat: 3674 vbat: 3645 vbus: 15010 avg_ibat: 3384 mA ibat: 0 mA ibus: 917 mA SOC: 26 % TDIE: 62.5 C VSYS: 3720.0 mV Chg_req: 4040 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 44 avg_vbat: 3673 vbat: 3641 vbus: 15015 avg_ibat: 3271 mA ibat: 0 mA ibus: 875 mA SOC: 26 % TDIE: 62.5 C VSYS: 3710.0 mV Chg_req: 4060 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 45 avg_vbat: 3673 vbat: 3638 vbus: 15015 avg_ibat: 3159 mA ibat: 0 mA ibus: 867 mA SOC: 26 % TDIE: 62.5 C VSYS: 3701.25 mV Chg_req: 4080 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 45 avg_vbat: 3671 vbat: 3620 vbus: 15020 avg_ibat: 3045 mA ibat: 0 mA ibus: 787 mA SOC: 26 % TDIE: 62.0 C VSYS: 3678.75 mV Chg_req: 4100 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 45 avg_vbat: 3669 vbat: 3611 vbus: 15025 avg_ibat: 2932 mA ibat: 0 mA ibus: 752 mA SOC: 26 % TDIE: 61.5 C VSYS: 3666.25 mV Chg_req: 4120 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 45 avg_vbat: 3667 vbat: 3606 vbus: 15025 avg_ibat: 2817 mA ibat: 0 mA ibus: 730 mA SOC: 26 % TDIE: 61.0 C VSYS: 3661.25 mV Chg_req: 4140 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560
0 : 46 avg_vbat: 3665 vbat: 3602 vbus: 15025 avg_ibat: 2702 mA ibat: 0 mA ibus: 717 mA SOC: 27 % TDIE: 61.0 C VSYS: 3660.0 mV Chg_req: 4160 mA STAT: 32796 Fault: 0 ICO_LIMIT: 2560

Registers (displayed in bytes by memory location).
0 , 255
1 , 255
2 , 0
3 , 13
4 , 32
5 , 13
6 , 0
7 , 10
8 , 192
9 , 13
10 , 176
11 , 4
12 , 0
13 , 16
14 , 64
15 , 10
16 , 160
17 , 0
18 , 160
19 , 0
20 , 1
21 , 60
22 , 161
23 , 79
24 , 0
25 , 128
26 , 0
27 , 0
28 , 15
29 , 133
30 , 127
31 , 223
32 , 128
33 , 28
34 , 0
35 , 129
36 , 9
37 , 0
38 , 0
39 , 0
40 , 0
41 , 0
42 , 10
43 , 137
44 , 0
45 , 62
46 , 2
47 , 0
48 , 0
49 , 244
50 , 46
51 , 228
52 , 46
53 , 132
54 , 22
55 , 220
56 , 22
57 , 94
58 , 2
59 , 122
60 , 0
61 , 0
62 , 0
63 , 4
128, 1
129, 128

  • 0
    TI__Guru 57481 points

    Hi,

    Did you notice any faults from the register readings?

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Prodigy 80 points

    No, as shown in the print out, the STATUS and FAULT registers show no change.

    Even if I increase and decrease the requested current (so the A/D readings go from current readings, to zeros and then back to current readings) the status and fault registers don't change at all. 

  • 0 in reply to Steve Carkner
    TI__Guru 57481 points

    Hi,

    We will check and get back to you soon.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    TI__Guru 57481 points

    Hello,

    For "Wtih 9V input I can get about 4250mA before it does this weird drop thing." Could you please provide the following when charging at 4250mA and when the charge current drops to 0A respectively?

    1. The charger operating conditions such as VBUS (voltage at VBUS pin), IVBUS, VBAT (voltage at BAT pin), IBAT, VSYS, ISYS.
    2. All the register readings. 

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Prodigy 80 points

    The following shows the charge working and then dropping out 250mS later to zero. 

    vbat: 4061mV vbus: 10130mV ibat: 4135 mA ibus: 1812 mA TDIE: 47.0 C VSYS: 4112.5 mV STAT: 32796 Fault: 0 ICO_LIMIT: 2560
    0 , 255
    1 , 255
    2 , 128
    3 , 13
    4 , 32
    5 , 13
    6 , 0
    7 , 10
    8 , 192
    9 , 13
    10 , 176
    11 , 4
    12 , 0
    13 , 16
    14 , 64
    15 , 10
    16 , 160
    17 , 0
    18 , 160
    19 , 0
    20 , 1
    21 , 60
    22 , 161
    23 , 79
    24 , 0
    25 , 132
    26 , 0
    27 , 0
    28 , 15
    29 , 133
    30 , 127
    31 , 223
    32 , 128
    33 , 28
    34 , 0
    35 , 0
    36 , 0
    37 , 0
    38 , 0
    39 , 0
    40 , 0
    41 , 0
    42 , 10
    43 , 137
    44 , 0
    45 , 170
    46 , 5
    47 , 16
    48 , 26
    49 , 168
    50 , 31
    51 , 148
    52 , 31
    53 , 20
    54 , 25
    55 , 92
    56 , 25
    57 , 74
    58 , 2
    59 , 94
    60 , 0
    61 , 179
    62 , 0
    63 , 4
    128, 17
    129, 128


    vbat: 3997mV vbus: 10190mV ibat: 0 mA ibus: 1510 mA TDIE: 46.5 C VSYS: 4041.25 mV STAT: 32796 Fault: 0 ICO_LIMIT: 2560
    0 , 255
    1 , 255
    2 , 192
    3 , 13
    4 , 32
    5 , 13
    6 , 0
    7 , 10
    8 , 192
    9 , 13
    10 , 176
    11 , 4
    12 , 0
    13 , 16
    14 , 64
    15 , 10
    16 , 160
    17 , 0
    18 , 160
    19 , 0
    20 , 1
    21 , 60
    22 , 161
    23 , 79
    24 , 0
    25 , 132
    26 , 0
    27 , 0
    28 , 15
    29 , 133
    30 , 127
    31 , 223
    32 , 128
    33 , 28
    34 , 0
    35 , 0
    36 , 0
    37 , 0
    38 , 0
    39 , 0
    40 , 0
    41 , 0
    42 , 10
    43 , 137
    44 , 0
    45 , 184
    46 , 4
    47 , 0
    48 , 0
    49 , 216
    50 , 31
    51 , 212
    52 , 31
    53 , 252
    54 , 24
    55 , 66
    56 , 25
    57 , 74
    58 , 2
    59 , 92
    60 , 0
    61 , 179
    62 , 0
    63 , 4
    128, 17
    129, 128

  • 0 in reply to Steve Carkner
    Prodigy 80 points

    Differences are:

    Requested Current (of course)

    Comparision - The requested charge current is different (of course) and the ADC readings are different (with iBAT = 0).

    Location           Before        After          Loc(Hex)    Comparison     Function

    0 255 255 00 OK
    1 255 255 01 OK
    2 128 192 02 DIFF Current
    3 13 13 03 OK
    4 32 32 04 OK
    5 13 13 05 OK
    6 0 0 06 OK
    7 10 10 07 OK
    8 192 192 08 OK
    9 13 13 09 OK
    10 176 176 0A OK
    11 4 4 0B OK
    12 0 0 0C OK
    13 16 16 0D OK
    14 64 64 0E OK
    15 10 10 0F OK
    16 160 160 10 OK
    17 0 0 11 OK
    18 160 160 12 OK
    19 0 0 13 OK
    20 1 1 14 OK
    21 60 60 15 OK
    22 161 161 16 OK
    23 79 79 17 OK
    24 0 0 18 OK
    25 132 132 19 OK
    26 0 0 1A OK
    27 0 0 1B OK
    28 15 15 1C OK
    29 133 133 1D OK
    30 127 127 1E OK
    31 223 223 1F OK
    32 128 128 20 OK
    33 28 28 21 OK
    34 0 0 22 OK
    35 0 0 23 OK
    36 0 0 24 OK
    37 0 0 25 OK
    38 0 0 26 OK
    39 0 0 27 OK
    40 0 0 28 OK
    41 0 0 29 OK
    42 10 10 2A OK
    43 137 137 2B OK
    44 0 0 2C OK
    45 170 184 2D DIFF ADC
    46 5 4 2E DIFF
    47 16 0 2F DIFF ADC
    48 26 0 30 DIFF
    49 168 216 31 DIFF ADC
    50 31 31 32 OK
    51 148 212 33 DIFF ADC
    52 31 31 34 OK
    53 20 252 35 DIFF ADC
    54 25 24 36 DIFF
    55 92 66 37 DIFF ADC
    56 25 25 38 OK
    57 74 74 39 OK ADC
    58 2 2 3A OK
    59 94 92 3B DIFF ADC
    60 0 0 3C OK
    61 179 179 3D OK ADC
    62 0 0 3E OK
    63 4 4 3F OK
    128 17 17 80 OK
    129 128 128 81 OK
  • 0 in reply to Steve Carkner
    TI__Guru 57481 points

    Hi,

    Could you please provide all the register numbers as wells as corresponding readings in hexadecimal (i.e. the same format as shown on the d/s)? The easiest way to debug is to plug in the register readings into BQ25638 GUI at BQStudio (downloadable at https://www.ti.com/tool/BQSTUDIO) and check if there’s any abnormal status or fault condition.

    BTW, was VIINDPM (REGx20[2]) or IINDPM (REGx20[3]) set to 1?

    Thanks,

    Ning

  • 0 in reply to Ning T
    Prodigy 80 points

    "was VIINDPM (REGx20[2]) or IINDPM (REGx20[3]) set to 1" - No.

    Here are the registers in the revised format, I was able to load these into BQStudio (I can provide text file if preferred).

    Charging normally, iBAT reading is accurate. Everything is good.

    REG02 0D40
    REG04 0D20
    REG06 0A00
    REG08 0DC0
    REG0A 04B0
    REG0C 1000
    REG0E 0A40
    REG10 00A0
    REG12 00A0
    REG14 01
    REG15 3C
    REG16 A1
    REG17 4F
    REG18 00
    REG19 84
    REG1A 00
    REG1B 00
    REG1C 0F
    REG1D 85
    REG1E 7F
    REG1F DF
    REG20 80
    REG21 1C
    REG22 00
    REG23 00
    REG24 00
    REG25 00
    REG26 00
    REG27 00
    REG28 00
    REG29 0A00
    REG2B 89
    REG2C 00
    REG2D 059C
    REG2F 1968
    REG31 1FB4
    REG33 1F98
    REG35 195C
    REG37 19AC
    REG39 024A
    REG3B 005D
    REG3D 00B3
    REG3F 04
    REG80 11
    REG81 80

    Charge abnormally, iBAT reading is Zero (even though some current flowing into battery) but no errors/status changes.

    REG02 0DC0
    REG04 0D20
    REG06 0A00
    REG08 0DC0
    REG0A 04B0
    REG0C 1000
    REG0E 0A40
    REG10 00A0
    REG12 00A0
    REG14 01
    REG15 3C
    REG16 A1
    REG17 4F
    REG18 00
    REG19 84
    REG1A 00
    REG1B 00
    REG1C 0F
    REG1D 85
    REG1E 7F
    REG1F DF
    REG20 80
    REG21 1C
    REG22 00
    REG23 00
    REG24 00
    REG25 00
    REG26 00
    REG27 00
    REG28 00
    REG29 0A00
    REG2B 89
    REG2C 00
    REG2D 04B8
    REG2F 0000
    REG31 1FD8
    REG33 1FD4
    REG35 18FC
    REG37 1942
    REG39 024A
    REG3B 005C
    REG3D 00B3
    REG3F 04
    REG80 11
    REG81 80

  • 0 in reply to Steve Carkner
    Prodigy 80 points

    Additoinal minor update - I tried replacing the inductor on the board. I went from a 1uH inductor rated at 6A (Bourns SRP5015TA-1R0M) to a much beefier 2.2uH 10A (Bourns SRP5030CA). I made the change because at high input voltage the system is fairly high to 38-40% current ripple. increasing inductance to 2.2uH reduces ripple to 20%.

    It made absolutely no difference to the operation of the device with respect to how it cuts off. I still got the exact same issue. So this helps to rule out possibility of ripple or peak switch current being an issue.

    Thx.

  • 0 in reply to Steve Carkner
    TI__Guru 57481 points

    Hi,

    We will check and get back to you.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    TI__Guru 57481 points

    Hi,

    1. Did you measured the actual charge current? Is it actual 0A?

    2. When IBAT_ADC=4065mA (REG2F=1968), IBUS_ADC=1436mA (REG2D=059C), When IBAT_ADC=0mA (REG2F=0000), IBUS_ADC=1208mA (REG2D=04B8), where does the input power go? 

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Prodigy 80 points

    I mentioned at the top of the thread " even though an external meter attached to the battery confirms that about 2.7 amps is flowing into the battery.". So there is current flowing into the battery even when iBat reads 0.00, but it is significantly less than the amount being requested in the current limit register.

    The efficiency is still quite good if you calculate power in versus power out. Switching signals also look OK on the scope.

    I am considering doing a software work around that detects when iBAT is giving false readings and will then reduce charge current requested until the ADC starts to read normally (and current to the battery goes up... even though I am reducing the amount requested). But I normally don't like to do work-arounds like this in a production product without understanding what exactly it is that I am working around :-)

    It also makes it hard for me to specify our products battery recharge rate since I have no idea how much it will vary from product to product.

    I have noticed that the point where the reading suddenly goes to zero does appear to change with die temperature a bit, for example it might be 4000mA when I have air blowing on the board, but will be 3800mA when I don't have air blowing on the board (and Tdie is perhaps 15 degrees higher). Tdie is still very acceptable in this design though, it is well away from any cut-offs.

  • 0 in reply to Steve Carkner
    TI__Guru 57481 points

    Hi,

    1. Sometimes the IBAT_ADC does not match the actual charge current going into the battery, right?

    2. Referring to the EVM user's guide at https://www.ti.com/lit/ug/sluucr0a/sluucr0a.pdf, please use sense resistors to measure the current precisely.

    3.2.5 Helpful Tips

    For precise measurements of input and output current, especially near termination, the current meter in series with the battery or battery simulator must not be set to auto-range and needs to be removed entirely. An alternate method for measuring charge current is to either use an oscilloscope with hall effect current probe or by a differential voltage measurement across the relevant sensing resistors populated on the BQ25638xEVM.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Prodigy 80 points

    The IBAT_ADC is always accurate OR it reads Zero (completely wrong). There is no "in-between".

    The EVM User's Guide refers to using a sense resistor to measure currents near termination (in other words, to measure LOW currents) because using a meter causes a voltage drop/rise that will cause the battery charging to falsely terminate. This isn't related to meauring HIGH current. However, I did put a 10mR sense resistor on my board to allow non-invasive battery current measurement and have confirmed that when IBAT reads Zero, there is still 2.7A approx of current flow into the battery. I have also tested the system with the sense resistor removed, it makes no difference to the operation of the circuit.

    I am not really sure what to do next except abandon this design.

  • 0 in reply to Steve Carkner
    TI__Guru 57481 points

    Hi,

    When the IBAT_ADC reads 0A, is the current flowing from the charger to the battery (i.e. SYS to BAT) or the battery to the charger (i.e. BAT to SYS)?

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Prodigy 80 points

    Current is flowing from the System to the Battery (ie. the battery is still charging, but at a reduced rate than what is being requested). 

  • 0 in reply to Steve Carkner
    TI__Guru 57481 points

    Hi,

    When the IBAT_ADC reads 0A, could you please help to measure manually VBUS (voltage at VBUS pin), IVBUS, VBAT (voltage at BAT pin), IBAT VSYS, ISYS? Please use sensing resistors to get the actual current. We would like to see if the device is under DPM (7.3.4.2 Dynamic Power Management) or not. 

    Thanks a lot,

    Ning.

  • 0 in reply to Ning T
    Prodigy 80 points

    The following values are in the format: REPORTED , MEASURED (externally)

    Vbus: 15060mV, 14980mV

    IVbus: 607mA, 620mA

    VBat: 3902mV, 3888mV

    Ibat: 0.00mA, 2316mA

    Vsys: 3845mV, 3916mV

    Isys: N/A, 28mA

  • 0 in reply to Steve Carkner
    TI__Guru 57481 points

    Hi,

    We are checking and will get back to you.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    TI__Guru 57481 points

    Hi,

    We are unable to duplicate your observation on the EVM. The thread is considered closed at this time. If more information is found in the future, we will let you know.

    Thanks,

    Ning.