BQ24650EVM-639: Strange Behavior

Jens Stegmann

Prodigy 50 points

Part Number: BQ24650EVM-639

For the Setup: I change R13 to 100kOhm, so that I have an output voltage of 4.2V.

I follow the measurement protocol as described in 2.7.1.

-as expected I measured V_sys=21V, V_ref= 3.3V, V_regn=0V, but V_Out=1.6V and not 0V.

-When I switch off the voltage source, a capacitive discharge curve is shown.

In the next step followed the measurement protocol as described in 2.7.2.

-All the voltages behaved as expected. V_REF=3.3V,V_regn=6V,V_out=4.1V (I changed R13), but D4 (State1) turned on.

Based on this Behavior and on the fact, that the IC didn't charge the Battery. I measure all components and found a short connection between the Gate and the Source of Q1.A.

I hope you can help me. I didn't changes no other components expect R13.

over 6 years ago

0 Kedar Manishankar over 6 years ago

TI__Mastermind 24075 points

Hi Jens,
When you follow 2.7.2 are you connecting a battery at VOUT? I recreated this test setup and I observe the results shown in the user guide.

0 Jens Stegmann over 6 years ago in reply to Kedar Manishankar

Prodigy 50 points

No, I didn't. And the STATE 1 LED is on. This is the reason why I'm so confused. Is it common in step 2.7.1, that V_out >>0V?

I think D1 or Q1A is the reason. As mentioned I'm also measuring a short between Gate and Drain of Q1A.

0 Kedar Manishankar over 6 years ago in reply to Jens Stegmann

TI__Mastermind 24075 points

Hi Jens,
Yes I believe Vout = 0V is possibly a typo, however just replacing one of the Vfb resistors without a battery should not give you the results you observe in the other test. Just to confirm, you are using the EVM in your test? Please take a scope capture of Vfb, Ichg, VCC, and VSRN when you observe this behavior.

0 Jens Stegmann over 6 years ago in reply to Kedar Manishankar

Prodigy 50 points

Hi Kedar,

I'm using the EVM Board. Because of your question, I repeated the experiment. This time works like expected, except the charging current where only 0.768A (it should be 2A). At Start, the remaining Voltage of the Lithium ions Battery was 3.3V. I also measured all Testpoints with an Ozilloskop. During Charing was the Voltage of STATE 2 V_state2=21V, like the V_CC. I'm thinking this way to high.

If you like I can send you the EVM Board.

best regards,

Jens

0 Kedar Manishankar over 6 years ago in reply to Jens Stegmann

TI__Mastermind 24075 points

Hi Jens,
Can you clarify what you mean by STATE 2V_state2? What voltage do you measure at Vfb and VCC at testpoints on board? I am currently testing your settings on the EVM board and can observe battery charging at 2A at 3.3V.

0 Kedar Manishankar over 6 years ago in reply to Kedar Manishankar

TI__Mastermind 24075 points

Hi Jens,
We have not heard from you in a while, and assume your issue has been resolved. If not, you can comment below or open a new thread.

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BQ24650EVM-639: Strange Behavior