PF1550 Battery Charging with iMX6ULZ

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PF1550 Battery Charging with iMX6ULZ

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Contributor II

Hi

I have a design using the PF1550 and the iMX6ULZ. This uses the part with the programming option 6 for the iMX6ULL with DDR3L. I'm currently having problems getting the battery charging working.

The board works fine when powered from VBUS (5V) or the battery (3.7 LiPro) but doesn't charge the battery when VBUS is connected.

One thing I have noticed on the A6 variant, CHG_OPER default is 1 (Charger off). First question, why is this? For other variants this is set to 2 (Charger On) by default.

The I2C communication to the device is working fine. Below is a dump of the registers with VBUS and battery connected. Battery is sitting around 3.54V.

0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef
00: 7c 06 11 00 00 00 83 00 00 00 00 00 00 00 01 03 |??...?.......??
10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
20: 00 00 00 00 00 3f 00 00 0c 1f 04 00 00 00 00 00 .....?..???.....
30: 00 00 2e 36 36 13 03 00 02 02 02 13 03 00 0f 0f ...66??.?????.??
40: 0f 03 03 00 00 00 00 00 00 00 03 00 10 03 00 0f ???.......?.??.?
50: 03 00 1f 03 00 00 00 00 01 80 02 00 00 00 00 03 ?.??....???....?
60: 03 03 03 02 03 03 00 0c 00 00 00 00 00 00 00 15 ??????.?.......?
70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
80: e5 00 51 00 25 00 20 4c 04 01 00 00 00 40 00 2b ?.Q.%. L??...@.+
90: 00 00 04 00 a0 00 05 00 01 00 00 01 00 00 04 50 ..?.?.?.?..?..?P
a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
c0: 00 00 00 00 1f fe 00 3f 28 04 00 2b 00 3b 00 00 ....??.?(?.+.;..
d0: 00 00 00 10 00 00 00 00 00 00 00 00 00 00 00 ab ...?...........?
e0: 00 00 0a 20 00 00 00 00 00 00 00 00 00 00 00 00 ..? ............
f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................

You can see register 0x89 that CHG_OPER set to 1.

I changed CHG_OPER to 2 to enable the charger but I still don't see the charger working. In the register dump below you can see that CHG_SNS stays at 12 which is charger block in linear mode, not charging.

0 1 2 3 4 5 6 7 8 9 a b c d e f 0123456789abcdef
00: 7c 06 11 00 00 00 83 00 00 00 00 00 00 00 01 03 |??...?.......??
10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
20: 00 00 00 00 00 3f 00 00 04 1f 04 00 00 00 00 00 .....?..???.....
30: 00 00 2e 36 36 13 03 00 02 02 02 13 03 00 0f 0f ...66??.?????.??
40: 0f 03 03 00 00 00 00 00 00 00 03 00 10 03 00 0f ???.......?.??.?
50: 03 00 1f 03 00 00 00 00 01 80 02 00 00 00 00 03 ?.??....???....?
60: 03 03 03 02 03 03 00 0c 00 00 00 00 00 00 00 15 ??????.?.......?
70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
80: e5 00 51 00 24 00 20 4c 04 02 00 00 00 40 00 ab ?.Q.$. L??...@.?
90: 00 00 04 00 a0 00 05 00 01 00 00 01 00 00 04 50 ..?.?.?.?..?..?P
a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
c0: 00 00 00 00 1f fe 00 3f 28 04 00 2b 00 3b 00 00 ....??.?(?.+.;..
d0: 00 00 00 10 00 00 00 00 00 00 00 00 00 00 00 ab ...?...........?
e0: 00 00 0a 20 00 00 00 00 00 00 00 00 00 00 00 00 ..? ............
f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................

Is there anything I am missing here to get the charging working.

 

Just for completeness here is the charger section from my schematic.

ian3_0-1600433708380.png

 

Thanks

Ian

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NXP TechSupport
NXP TechSupport

Hi,

 

Correct, on version A6 the charger is OFF by default by customer demand. The A6 version was initially made for a customer who will not be using the charger, reason of why it is disabled for this variant of the PMIC.

 

Check figure 14 of the datasheet

 

There are some condition for the ‘CHG_OPER = 2’ (charger = on, linear = on) to work.

When there is a valid input, the battery is charging as long as VSYS is the larger of VSYSMIN and VBATT + IBAT * RBATFET.

 

According to your configuration, VSYSMIN after configuring, is 4.3V (Bits 7 and 6 on register 8F), but what is the actual VSYS voltage level in your system? In order to enable the charger should be higher than 4.3V

 

Regards,
Jose

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Contributor II

Hi

I have tried VSYSMIN at 3.5V,3.7V and 4.3V. I can see the VSYS output change to the value I set but the charger always stays off.

Currently VBUSIN is 4.9V and my battery is sitting at 3.2V. VSYS is whatever I set it to above.

CHG_SNS always goes to 12 (charger block is in linear only mode, not charging). If I remove VBUSIN CHG_SNS goes to 8. This is with CHG_OPER changed to 2.

I've ordered some samples of the A3 variant where the OTP is programmed with the charger on. I'll see if that makes a difference.

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NXP TechSupport
NXP TechSupport

Hi,

 

Since the THM_CNFG[1:0] bits are set to 0x00, this means that the thermistor functionality is not needed, however, I’m curious about the reading on THM_SNS bit on register 0x87 this bit is ‘1’ which means that “Thermistor temperature is < Cool, or > Warm threshold”, which according to Figure 23 of the datasheet, this would cause the charger to be inhibited.

 

Lets check how does the A3 version behaves in your system.

 

Regards,

Jose

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