Getting battery charging current from TPS6507x internal ADC

Vsevolod Anisimov

Other Parts Discussed in Thread: TPS65070

Greetings,

I`m using TPS65070 for a long time and now i want to get a battery charging current from it`s internal ADC. I have a stable routine to get a voltage from SYS pin, the data i have is correct. But when i try to get a current at BAT pin during battery charging it isn`t even close. For example my battery is charging by 130 mA and TPS65070 ADC give fully broken data - from 550 mA to 2200 mA. My routine to get current is:

1) write D5 to <ADCONFIG>;

2) wait until bit 5 of <ADCONFIG> isn`t 1 (till the conversion ends);

3) read <ADRESULT1> then <ADRESULT2> registers, make a full 10 bit data.

4) multiply data with 2250 (scale from <ADCONFIG> table), then divide result on 1024 - for 10 bit`s ADC.

What am i doing wrong?

Best regards,

Vsevolod

over 14 years ago

0 Daniel Acevedo over 14 years ago

TI__Genius 17240 points

Are the contents of register TSCMODE 6 or 7 (hex)?

0 Vsevolod Anisimov over 14 years ago in reply to Daniel Acevedo

Prodigy 240 points

The TSCMODE register is in default state (7). But how it depends?

0 Daniel Acevedo over 14 years ago in reply to Vsevolod Anisimov

TI__Genius 17240 points

The battery charge current is (ADRESULT2,1) / 1024 * ICHG.

Where ICHG = Kiset/Riset.

With your method, I believe you were calculating the voltage on the ISET pin and not the charge current.

I asked about TSCMODE because it needs to be 6 or 7 b (hex) to measure charge current.

0 Vsevolod Anisimov over 14 years ago in reply to Daniel Acevedo

Prodigy 240 points

I made a few tests with your (ADRESULT2,1) / 1024 * ICHG formula. A little remark. It is correct only when ICHG > 1, otherwise the result will always be 0. So the problem is solved, thanks!

0 uMin over 14 years ago in reply to Daniel Acevedo

Intellectual 860 points

Hi Daniel,

In the datasheet, on page 36 under A/D Converter, it states "Battery charge current (voltage at pin Iset; Icharge = UISET/Rset × KISET)".

What is Uiset ? Is it a typo and should have been Viset, the voltage at the pin Iset ?

Thanks.

0 Daniel Acevedo over 14 years ago in reply to uMin

TI__Genius 17240 points

The equation for charge current is correct but Uiset not defined in the datasheet.

Uiset is the voltage at the Iset pin divided by the full range voltage of 2.25V.

In the terms I used in my previous post, Uiset = ADRESULT2,1 / 1024.

Power management

Power management forum

Getting battery charging current from TPS6507x internal ADC