BQ2947: about OV

Kaji@PAN

Part Number: BQ2947

Hi,

I am using bq 294702.
Please tell me about the following contents.

1. About detection of OV. If the cell voltage exceeds VOH even once, is the overvoltage detection counter cleared when it falls below VOH (4.30 V)? Or is it when it falls below VOH - VHYS (= 4.0 V)? I think that it is 4.0V.

2. After exceeding VOH, charging of the capacitor connected to the CD terminal starts.
However, there is a delay like red in the figure below. How many seconds will the capacitor start charging after exceeding VOH?

Best Regards,

over 8 years ago

0 Vish Nadarajah over 8 years ago

TI__Expert 6085 points

(1) The OV condition should exist for Tcd delay, for the OUT to trigger as a true OV condition, Fig 8 gives a true illustration of the OV timer delay behavior.

Tcd delay can be 1-2 depending on the value of the CD cap.

(2) The d/s is not clear to me either. Think it should be <170mS(max). Will come back with definite answer.

0 Kaji@PAN over 8 years ago in reply to Vish Nadarajah

Mastermind 7805 points

Thank you for answering.

The first question is what I thought from Figure 1.
It appears to be cleared if it goes below Vov-Vhys. Is that correct in this way of thinking?

The next question is simply what is the internal logic delay.
I think that it is about several μs, but how is it?

Best Regards,

0 Vish Nadarajah over 8 years ago in reply to Kaji@PAN

TI__Expert 6085 points

The small charge up delay time will depend on the externally selected capacitance, but relative to 120ms, it will be smaller than 1ms.

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BQ2947: about OV