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bq77908a Short circuit charge test

vivek kumar
Prodigy 50 points
Other Parts Discussed in Thread: BQ77908A

Hi TI Experts,

Per Table 3 in the datasheet, when the conditions for SCC (Short circuit charge) are met, then both the charge and discharge FETS will be turned off.  We tested it and find that the charging current alone goes to zero when the short circuit current goes beyond the defined threshold.  However the TI tool is still able to communicate with the battery pack fuel gauge circuitry meaning that the battery pack didn't disable both the charge and discharge FETS. We use a series FET configuration. SCC trip delay set is 960usecs and trip current is 6A.

Does both the FETS disable after SCC?Is the datasheet accurate? Please find attached log file and provide your comments.

short circuit test.log 
bq EVSW Version: 0.9.90 	
Dev: Read Error
10/28/2015 4:08:10 PM	
           
Sample	Stamp	~Elapsed(s)	Control	CtrlStatus	StateofCharge	RemCap	FullChgCap	Voltage	AveCur	Temperature	Flags	@Rate(@)	@TimeEmpty	NomAvailCap	FullAvailCap	AvgTimeEmpty	AvgTimeFull	StandbyCurr	StandTTE	MaxLoadCurrent	MaxTTE	AvailEnergy	AvailPower	TTEConstPwr	IntTemp	CycleCnt	StateofHealth	Charge Voltage	Charge Current	Passed Charge	DOD0	SelfDischargeCurrent	PackConfig	Current
1	4:08:13 PM	0	600D	600D	55	1333	2457	22914	454	28.5	0180	0	65535	1610	2734	65535	167	0	65535	-500	160	4805	2696	65535	30.2	3	100	24720	2500	-3	7072	0	0971	706
2	4:08:16 PM	3	600D	600D	55	1334	2457	22914	527	28.5	0180	0	65535	1612	2734	65535	148	0	65535	-500	160	4808	3228	65535	30.1	3	100	24720	2500	-4	7072	0	0971	1198
3	4:08:19 PM	6	600D	600D	55	1334	2457	22914	527	28.5	0180	0	65535	1612	2734	65535	148	0	65535	-500	160	4808	3228	65535	30.1	3	100	24720	2500	-4	7072	0	0971	1198
4	4:08:22 PM	9	600D	600D	55	1336	2457	22968	743	28.5	0180	0	65535	1613	2734	65535	121	0	65535	-500	160	4816	4685	65535	30.1	3	100	24720	2500	-6	7072	0	0971	1491
5	4:08:25 PM	12	600D	600D	55	1339	2457	23058	1088	28.5	0180	0	65535	1616	2734	65535	112	0	65535	-500	161	4823	8020	65535	30.0	3	100	24720	2500	-9	7072	0	0971	2086
6	4:08:28 PM	15	600D	600D	55	1339	2457	23058	1088	28.5	0180	0	65535	1616	2734	65535	112	0	65535	-500	161	4823	8020	65535	30.0	3	100	24720	2500	-9	7072	0	0971	2086
7	4:08:31 PM	18	600D	600D	55	1342	2457	23070	1378	28.5	0180	0	65535	1620	2734	65535	100	0	65535	-500	161	4838	8025	65535	30.0	3	100	24720	2500	-12	7072	0	0971	2340
8	4:08:35 PM	22	600D	600D	55	1342	2457	23070	1378	28.5	0180	0	65535	1620	2734	65535	100	0	65535	-500	161	4838	8025	65535	30.0	3	100	24720	2500	-12	7072	0	0971	2340
9	4:08:38 PM	25	600D	600D	55	1347	2457	23172	1852	28.4	0180	0	65535	1624	2734	65535	81	0	65535	-500	162	4856	12064	65535	30.0	3	100	24720	2500	-17	7072	0	0971	3123
10	4:08:41 PM	28	600D	600D	55	1347	2457	23172	1852	28.4	0180	0	65535	1624	2734	65535	81	0	65535	-500	162	4856	12064	65535	30.0	3	100	24720	2500	-17	7072	0	0971	3123
11	4:08:44 PM	31	600D	600D	55	1351	2457	23190	2221	28.4	0180	0	65535	1629	2734	65535	65	0	65535	-500	162	4871	12074	65535	30.0	3	100	24720	2500	-22	7072	0	0971	3124
12	4:08:47 PM	34	600D	600D	55	1351	2457	23190	2221	28.4	0180	0	65535	1629	2734	65535	65	0	65535	-500	162	4871	12074	65535	30.0	3	100	24720	2500	-22	7072	0	0971	3124
13	4:08:50 PM	37	600D	600D	56	1356	2457	23202	2526	28.4	0180	0	65535	1633	2734	65535	58	0	65535	-500	163	4890	12084	65535	30.0	3	100	24720	2500	-26	7072	0	0971	3124
14	4:08:53 PM	40	600D	600D	56	1356	2457	23202	2526	28.4	0180	0	65535	1633	2734	65535	58	0	65535	-500	163	4890	12084	65535	30.0	3	100	24720	2500	-26	7072	0	0971	3124
15	4:08:56 PM	43	600D	600D	56	1361	2457	23286	2824	28.4	0180	0	65535	1639	2734	65535	52	0	65535	-500	163	4908	15478	65535	30.0	3	100	24720	2500	-32	7072	0	0971	3987
16	4:08:59 PM	46	600D	600D	56	1367	2457	23304	3162	28.4	0180	0	65535	1645	2734	65535	46	0	65535	-500	164	4930	15486	65535	30.0	3	100	24720	2500	-39	7072	0	0971	3987
17	4:09:02 PM	49	600D	600D	56	1367	2457	23304	3162	28.4	0180	0	65535	1645	2734	65535	46	0	65535	-500	164	4930	15486	65535	30.0	3	100	24720	2500	-39	7072	0	0971	3987
18	4:09:05 PM	52	600D	600D	56	1374	2457	23316	3441	28.4	0180	0	65535	1651	2734	65535	42	0	65535	-500	165	4956	15493	65535	30.1	3	100	24720	2500	-44	7072	0	0971	3987
19	4:09:08 PM	55	600D	600D	56	1374	2457	23316	3441	28.4	0180	0	65535	1651	2734	65535	42	0	65535	-500	165	4956	15493	65535	30.1	3	100	24720	2500	-44	7072	0	0971	3987
20	4:09:11 PM	58	600D	600D	57	1380	2457	23322	3600	28.4	0180	0	65535	1658	2734	65535	40	0	65535	-500	166	4978	15501	65535	30.1	3	100	24720	2500	-51	7072	0	0971	3987
21	4:09:14 PM	61	600D	600D	57	1380	2457	23322	3600	28.4	0180	0	65535	1658	2734	65535	40	0	65535	-500	166	4978	15501	65535	30.1	3	100	24720	2500	-51	7072	0	0971	3987
22	4:09:17 PM	64	600D	600D	57	1386	2457	23334	3731	28.5	0180	0	65535	1663	2734	65535	38	0	65535	-500	166	5001	15817	65535	30.2	3	100	24720	2500	-56	7072	0	0971	4300
23	4:09:20 PM	67	600D	600D	57	1386	2457	23334	3731	28.5	0180	0	65535	1663	2734	65535	38	0	65535	-500	166	5001	15817	65535	30.2	3	100	24720	2500	-56	7072	0	0971	4300
24	4:09:23 PM	70	600D	600D	57	1394	2457	23394	3961	28.5	0180	0	65535	1671	2734	65535	36	0	65535	-500	167	5030	17565	65535	30.2	3	100	24720	2500	-64	7072	0	0971	4505
25	4:09:26 PM	73	600D	600D	57	1394	2457	23394	3961	28.5	0180	0	65535	1671	2734	65535	36	0	65535	-500	167	5030	17565	65535	30.2	3	100	24720	2500	-64	7072	0	0971	4505
26	4:09:29 PM	76	600D	600D	57	1400	2457	23400	4119	28.5	0180	0	65535	1678	2734	65535	34	0	65535	-500	168	5052	17573	65535	30.3	3	100	24720	2500	-71	7072	0	0971	4506
27	4:09:32 PM	79	600D	600D	57	1400	2457	23400	4119	28.5	0180	0	65535	1678	2734	65535	34	0	65535	-500	168	5052	17573	65535	30.3	3	100	24720	2500	-71	7072	0	0971	4506
28	4:09:35 PM	82	600D	600D	58	1407	2457	23412	4250	28.5	0180	0	65535	1684	2734	65535	33	0	65535	-500	169	5082	17583	65535	30.4	3	100	24720	2500	-78	7072	0	0971	4506
29	4:09:38 PM	85	600D	600D	58	1414	2457	23418	4370	28.5	0180	0	65535	1692	2734	65535	32	0	65535	-500	170	5104	18963	65535	30.5	3	100	24720	2500	-85	7072	0	0971	4852
30	4:09:42 PM	89	600D	600D	58	1414	2457	23418	4370	28.5	0180	0	65535	1692	2734	65535	32	0	65535	-500	170	5104	18963	65535	30.5	3	100	24720	2500	-85	7072	0	0971	4852
31	4:09:45 PM	92	600D	600D	58	1422	2457	23466	4510	28.6	0180	0	65535	1699	2734	65535	31	0	65535	-500	171	5134	18977	65535	30.5	3	100	24720	2500	-92	7072	0	0971	4851
32	4:09:48 PM	95	600D	600D	58	1422	2457	23466	4510	28.6	0180	0	65535	1699	2734	65535	31	0	65535	-500	171	5134	18977	65535	30.5	3	100	24720	2500	-92	7072	0	0971	4851
33	4:09:51 PM	98	600D	600D	59	1430	2457	23496	4659	28.6	0180	0	65535	1707	2734	65535	30	0	65535	-500	172	5163	19674	65535	30.7	3	100	24720	2500	-100	7072	0	0971	5024
34	4:09:54 PM	101	600D	600D	59	1430	2457	23496	4659	28.6	0180	0	65535	1707	2734	65535	30	0	65535	-500	172	5163	19674	65535	30.7	3	100	24720	2500	-100	7072	0	0971	5024
35	4:09:57 PM	104	600D	600D	59	1437	2457	23508	4765	28.6	0180	0	65535	1715	2734	65535	29	0	65535	-500	173	5189	19684	65535	30.7	3	100	24720	2500	-109	7072	0	0971	5024
36	4:10:00 PM	107	600D	600D	59	1437	2457	23508	4765	28.6	0180	0	65535	1715	2734	65535	29	0	65535	-500	173	5189	19684	65535	30.7	3	100	24720	2500	-109	7072	0	0971	5024
37	4:10:03 PM	110	600D	600D	59	1445	2457	23532	4865	28.6	0180	0	65535	1722	2734	65535	28	0	65535	-500	174	5222	20388	65535	30.9	3	100	24720	2500	-116	7072	0	0971	5198
38	4:10:06 PM	113	600D	600D	59	1445	2457	23532	4865	28.6	0180	0	65535	1722	2734	65535	28	0	65535	-500	174	5222	20388	65535	30.9	3	100	24720	2500	-116	7072	0	0971	5198
39	4:10:09 PM	116	600D	600D	60	1453	2457	23544	4977	28.7	0180	0	65535	1731	2734	65535	27	0	65535	-500	174	5248	20393	65535	30.9	3	100	24720	2500	-124	7072	0	0971	5197
40	4:10:12 PM	119	600D	600D	60	1461	2457	23556	5041	28.7	0180	0	65535	1738	2734	65535	27	0	65535	-500	176	5282	20403	65535	31.1	3	100	24720	2500	-132	7072	0	0971	5197
41	4:10:15 PM	122	600D	600D	60	1461	2457	23556	5041	28.7	0180	0	65535	1738	2734	65535	27	0	65535	-500	176	5282	20403	65535	31.1	3	100	24720	2500	-132	7072	0	0971	5197
42	4:10:18 PM	125	600D	600D	60	1470	2457	23568	5094	28.8	0180	0	65535	1747	2734	65535	26	0	65535	-500	176	5311	20418	65535	31.2	3	100	24720	2500	-140	7072	0	0971	5198
43	4:10:21 PM	128	600D	600D	60	1470	2457	23568	5094	28.8	0180	0	65535	1747	2734	65535	26	0	65535	-500	176	5311	20418	65535	31.2	3	100	24720	2500	-140	7072	0	0971	5198
44	4:10:24 PM	131	600D	600D	61	1477	2457	23574	5126	28.8	0180	0	65535	1756	2734	65535	26	0	65535	-500	177	5341	21119	65535	31.3	3	100	24720	2500	-149	7072	0	0971	5370
45	4:10:27 PM	134	600D	600D	61	1477	2457	23574	5126	28.8	0180	0	65535	1756	2734	65535	26	0	65535	-500	177	5341	21119	65535	31.3	3	100	24720	2500	-149	7072	0	0971	5370
46	4:10:30 PM	137	600D	600D	61	1486	2457	23604	5209	28.9	0180	0	65535	1763	2734	65535	25	0	65535	-500	179	5374	21131	65535	31.4	3	100	24720	2500	-157	7072	0	0971	5518
47	4:10:33 PM	140	600D	600D	61	1486	2457	23604	5209	28.9	0180	0	65535	1763	2734	65535	25	0	65535	-500	179	5374	21131	65535	31.4	3	100	24720	2500	-157	7072	0	0971	5518
48	4:10:36 PM	143	600D	600D	61	1494	2457	23634	5312	28.9	0180	0	65535	1772	2734	65535	24	0	65535	-500	179	5400	21834	65535	31.5	3	100	24720	2500	-166	7072	0	0971	5543
49	4:10:39 PM	146	600D	600D	61	1494	2457	23634	5312	28.9	0180	0	65535	1772	2734	65535	24	0	65535	-500	179	5400	21834	65535	31.5	3	100	24720	2500	-166	7072	0	0971	5543
50	4:10:42 PM	149	600D	600D	62	1503	2457	23646	5381	29.0	0180	0	65535	1780	2734	65535	24	0	65535	-500	181	5437	22544	65535	31.7	3	100	24720	2500	-174	7072	0	0971	5716
51	4:10:45 PM	152	600D	600D	62	1503	2457	23646	5381	29.0	0180	0	65535	1780	2734	65535	24	0	65535	-500	181	5437	22544	65535	31.7	3	100	24720	2500	-174	7072	0	0971	5716
52	4:10:48 PM	155	600D	600D	62	1512	2457	23682	5494	29.0	0180	0	65535	1789	2734	65535	23	0	65535	-500	181	5470	22561	65535	31.8	3	100	24720	2500	-183	7072	0	0971	5716
53	4:10:51 PM	158	600D	600D	62	1520	2457	23688	5559	29.1	0180	0	65535	1799	2734	65535	23	0	65535	-500	183	5500	22567	65535	32.0	3	100	24720	2500	-193	7072	0	0971	5716
54	4:10:55 PM	162	600D	600D	62	1520	2457	23688	5559	29.1	0180	0	65535	1799	2734	65535	23	0	65535	-500	183	5500	22567	65535	32.0	3	100	24720	2500	-193	7072	0	0971	5716
55	4:10:58 PM	165	600D	600D	63	1530	2457	23700	5612	29.1	0180	0	65535	1807	2734	65535	22	0	65535	-500	184	5537	22582	65535	32.1	3	100	24720	2500	-201	7072	0	0971	5716
56	4:11:01 PM	168	600D	600D	63	1530	2457	23700	5612	29.1	0180	0	65535	1807	2734	65535	22	0	65535	-500	184	5537	22582	65535	32.1	3	100	24720	2500	-201	7072	0	0971	5716
57	4:11:04 PM	171	601D	601D	63	1535	2457	24942	4603	29.2	0180	0	65535	1812	2734	65535	27	0	65535	-500	184	5548	0	65535	32.2	3	100	24720	2500	-204	7072	0	0971	0
58	4:11:07 PM	174	601D	601D	63	1535	2457	24942	4603	29.2	0180	0	65535	1812	2734	65535	27	0	65535	-500	184	5548	0	65535	32.2	3	100	24720	2500	-204	7072	0	0971	0
59	4:11:10 PM	177	601D	601D	63	1535	2457	24942	3264	29.2	0180	0	65535	1812	2734	65535	41	0	65535	-500	184	5548	0	65535	32.2	3	100	24720	2500	-204	7072	0	0971	0
60	4:11:13 PM	180	601D	601D	63	1535	2457	24942	3264	29.2	0180	0	65535	1812	2734	65535	41	0	65535	-500	184	5548	0	65535	32.2	3	100	24720	2500	-204	7072	0	0971	0
61	4:11:16 PM	183	601D	601D	63	1535	2457	24942	2162	29.2	0180	0	65535	1812	2734	65535	58	0	65535	-500	184	5548	0	65535	32.2	3	100	24720	2500	-204	7072	0	0971	0
62	4:11:19 PM	186	601D	601D	63	1535	2457	24942	2162	29.2	0180	0	65535	1812	2734	65535	58	0	65535	-500	184	5548	0	65535	32.2	3	100	24720	2500	-204	7072	0	0971	0
63	4:11:22 PM	189	601D	601D	63	1535	2457	24942	1431	29.2	0180	0	65535	1812	2734	65535	82	0	65535	-500	184	5548	0	65535	32.2	3	100	24720	2500	-204	7072	0	0971	0
64	4:11:25 PM	192	601D	601D	63	1535	2457	24942	1015	29.3	0180	0	65535	1812	2734	65535	101	0	65535	-500	184	5548	0	65535	32.3	3	100	24720	2500	-204	7072	0	0971	0
65	4:11:28 PM	195	601D	601D	63	1535	2457	24942	1015	29.3	0180	0	65535	1812	2734	65535	101	0	65535	-500	184	5548	0	65535	32.3	3	100	24720	2500	-204	7072	0	0971	0
66	4:11:31 PM	198	601D	601D	63	1535	2457	24942	672	29.3	0180	0	65535	1812	2734	65535	110	0	65535	-500	184	5548	0	65535	32.3	3	100	24720	2500	-204	7072	0	0971	0
67	4:11:34 PM	201	601D	601D	63	1535	2457	24942	672	29.3	0180	0	65535	1812	2734	65535	110	0	65535	-500	184	5548	0	65535	32.3	3	100	24720	2500	-204	7072	0	0971	0
68	4:11:37 PM	204	6008	6008	0	0	2500	2934	24	29.3	0186	0	65535	0	2491	65535	6228	0	65535	-500	0	8864	2053	65535	32.0	3	100	24720	2500	0	16384	0	0971	533
69	4:11:40 PM	207	6008	6008	0	0	2500	2934	24	29.3	0186	0	65535	0	2491	65535	6228	0	65535	-500	0	8864	2053	65535	32.0	3	100	24720	2500	0	16384	0	0971	533
70	4:11:43 PM	210	600D	600D	0	0	2491	23106	172	29.3	0186	0	65535	0	2491	65535	764	0	65535	-500	0	8864	2053	65535	31.9	3	100	24720	2500	-1	16384	0	0971	532
71	4:11:46 PM	213	600D	600D	0	0	2491	23106	172	29.3	0186	0	65535	0	2491	65535	764	0	65535	-500	0	8864	2053	65535	31.9	3	100	24720	2500	-1	16384	0	0971	532
72	4:11:49 PM	216	600D	600D	0	0	2491	23106	294	29.2	0186	0	65535	0	2491	65535	488	0	65535	-500	0	8863	2053	65535	31.8	3	100	24720	2500	-1	16384	0	0971	533
73	4:11:52 PM	219	600D	600D	0	0	2491	23106	294	29.2	0186	0	65535	0	2491	65535	488	0	65535	-500	0	8863	2053	65535	31.8	3	100	24720	2500	-1	16384	0	0971	533
74	4:11:55 PM	222	600D	600D	0	0	2491	23106	375	29.2	0186	0	65535	0	2491	65535	414	0	65535	-500	0	8861	2053	65535	31.7	3	100	24720	2500	-2	16384	0	0971	533
75	4:11:59 PM	226	600D	600D	0	0	2491	23106	375	29.2	0186	0	65535	0	2491	65535	414	0	65535	-500	0	8861	2053	65535	31.7	3	100	24720	2500	-2	16384	0	0971	533
76	4:12:02 PM	229	600D	600D	0	0	2491	23106	421	29.2	0186	0	65535	0	2491	65535	366	0	65535	-500	0	8860	2053	65535	31.6	3	100	24720	2500	-3	16384	0	0971	533
77	4:12:05 PM	232	600D	600D	0	0	2491	23112	459	29.1	0186	0	65535	0	2491	65535	343	0	65535	-500	0	8858	2049	65535	31.6	3	100	24720	2500	-4	16384	0	0971	533
78	4:12:08 PM	235	600D	600D	0	0	2491	23112	459	29.1	0186	0	65535	0	2491	65535	343	0	65535	-500	0	8858	2049	65535	31.6	3	100	24720	2500	-4	16384	0	0971	533
79	4:12:11 PM	238	600D	600D	0	0	2491	23112	483	29.1	0186	0	65535	0	2491	65535	328	0	65535	-500	0	8857	2049	65535	31.5	3	100	24720	2500	-5	16384	0	0971	533
80	4:12:14 PM	241	600D	600D	0	0	2491	23112	483	29.1	0186	0	65535	0	2491	65535	328	0	65535	-500	0	8857	2049	65535	31.5	3	100	24720	2500	-5	16384	0	0971	533

-Vivek

  • 0
    TI__Guru 54715 points

    Both FETs should turn off.  Note in table 3 the recovery condition is removal of the charger which to the bq77908A is CHGST low.  If CHGST is low it may recovery quite quickly compared to a log interval.  If the charger has not reacted yet I would expect it to cycle when the FETs come on again.

    I'm not sure the gauging device you are using or the connections.  If the voltages remain the same before and after protection communication may continue from the same potential even though the direct reference is lost although noise and errors may be high.  Normally there will be a collapse in a voltage with FETs open and as you indicate communication loss might be expected. You will likely have to check your system behavior with an oscilloscope to see what is happening.