Battery Temperature Monitoring in Charger Disabled Condition

Suresh Samynathan

Other Parts Discussed in Thread: TPS65950, DM3725

Our application requires the battery temperature needs to be monitored continuously even without charging also. By default, if the charger is disabled, the current source goes to off state. I tried to enable the current source by writing the TBATOR1EN bit to 1 in AC charger disabled condition ( BCIAUTOAC=0) and observed the following

1. The current source provides 10uA current for the thermistor in AC charger plugged in condition. The BCICH0_LSB and BCICH0_MSB read values are correct

2. When the charger is plugged out, the current source output reduces to 5uA. The BCICH0_LSB and BCICH0_MSB read values are not matching with the ADC input voltage for the 5uA current value.

Can you please clarify why the current reduces to 5uA and the ADC read value is not correct in the charger disabled condition.

Is it possible to monitor the battery temperature in charger disabled condition.

over 16 years ago

0 Rohit Bhan over 16 years ago

Prodigy 150 points

Hi,

Have you also enabled the ITHEN bit? This bit is the enable for the 10ua current source and by enabling it you should be able see the correct current source value.

0 Suresh Samynathan over 16 years ago in reply to Rohit Bhan

Intellectual 360 points

Hi,

Yes, the ITHEN bit also enabled

0 Rohit Bhan over 16 years ago in reply to Suresh Samynathan

Prodigy 150 points

Ok Thanks,

Can you provide me your complete programming sequence.

0 Suresh Samynathan over 16 years ago in reply to Rohit Bhan

Intellectual 360 points

The sequence is as below

1. Charger is enabled (normal operation)

2. Charger is disabled by writing 0x30 value into BOOT_BCI register

3. Current reference is enabled by setting ITHEN=1 in BCICTL1

4. TBATOR1EN=1 in BCIMFEN2 is Set

5. Battery Temperature Monitoring ADC1 BCICH0_LSB and BCICH0_MSB is read.

0 Rohit Bhan over 16 years ago

Prodigy 150 points

Hi,

After detailed analysis we confirm that the battery temperature monitoring cannot be be done without Charger being plugged.The reason being the ADIN1 source current is working on Charger supply domain and if Charger is not present then the source current is not correct which explains the behaviour you are seeing.

Thanks,

0 Raviraj Somnache1 over 8 years ago in reply to Rohit Bhan

Intellectual 430 points

Hi,

We are also facing same issue with DM3725 and TPS65950.

Is this issue because of TPS65950 HW limitation? But in TPS errata this limitation not mentioned.

Is there any SW workaround to fix this.

Regards,

Raviraj

0 Richard Solarski over 8 years ago in reply to Raviraj Somnache1

TI__Genius 10885 points

Hi Raviraj,

The Technical Reference Manual for this device states that ADCIN1 can't be used a GP input as it is dedicated to the BCI.

0 Raviraj Somnache1 over 8 years ago in reply to Richard Solarski

Intellectual 430 points

Thanks for your comments.
As per TPS65950 TRM ADCIN1 can be used for BCI:Battery temperature(BTEMP) and we are also using for same purpose.
The issue is we are able to read proper battery temperature only when USB cable is connected to device otherwise reading is not proper.
The reason behind this
1. The current source is 10uA when USB cable connected to device and
2. When the USB cable plugged out, the current source output reduces to 5uA. The BCICH0_LSB and BCICH0_MSB read values are not matching with the ADC input voltage for the 5uA current value.
The same information is added in starting of this post.

Please let us know your comments on this, Are we missing any register setting or Is there limitation from TPS.

Thanks,
Raviraj

0 Kevin LaRosa over 8 years ago in reply to Raviraj Somnache1

TI__Genius 17380 points

Hi Raviraj,

You are correct, TPS65950 ADCIN1 can be used for battery temperature measurement only while battery charger interface (BCI) is powered (section 7.5.9). The BCI is powered by the charger to ensure that there is no extra drain on the battery (since charger isn't necessary when 5V isn't present). Temperature measurement of the battery is typically critical during charging and not as critical during normal operation so the block is not usable when charger isn't powered.

0 Raviraj Somnache1 over 8 years ago in reply to Kevin LaRosa

Intellectual 430 points

Thanks Kevin for inputs.

This will help us to modify our design and implementation and find alternate solution in HW to read battery temperature in not charging mode.

Thanks,
Raviraj

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Battery Temperature Monitoring in Charger Disabled Condition