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[BQ34Z100] Heating problem

paik nam woong
Prodigy 120 points
Other Parts Discussed in Thread: BQ34Z100

Part : BQ34Z100

Schematic : Similar Figure 7 @ datasheet

Problem : BQ34Z100 Self Heating & REG25(Regulator output) voltage = 3.3V

Item Count : Total=16EA , Self Heating=6EA       =>  6/16=37%

C1, C2, C8 is shortest path to BQ34Z100.

same problem at below link.

http://e2e.ti.com/support/power_management/battery_management/f/180/t/329819.aspx?pi300607=2

normally it operate good...(No Heating & REG25=2.5v)

but after long time aging.... REG25 output voltage=3.3V & heating..  and not recover..

remove battery and reconnecting... it is only way to recover.

---------------------------------------------------------------------------------------

is there overvoltage protection at internal regulator output???

(I guess internal overvoltage protection part  make heating)

internal regulator only operate for external Thermister(RT1) and VEN??

(can i use BQ34Z100 without internal Regulator(Broken Pin number 6, 7) and external LDO 2.5v))

adding resistor between BAT+ to REGIN.  it can solve problem??

i want to know internal block Diagram of BQ34Z100.....

  • 0
    TI__Guru 73830 points

    The issue in the previous case was that voltage exceeded the 5.5V absolute max rating for the device. This can cause the SCR in the ESD protection circuit to fire and hold. You may need to add an external zener clamp to prevent over voltage conditions or transients from reaching the device. Also, you should not connect REG25 to VEN. You should use a switch to apply voltage to VEN when you want to activate the LEDs.

  • 0 in reply to ThomasCosby
    Prodigy 30 points

    1. Just one cell Li-polymer is connected(soldered), so never exceed 5.5V.

    2. We have to turn on the LED always and If i look at the pin description of datasheet, swaitch is optional that means VEN can be enable always, right? and VEN is input,but it is output on datasheet

  • 0 in reply to dongseok huh
    TI__Guru 73830 points

    Something in the design must be getting the device into a latch-up condition. The over voltage condition is the only case that we have found so far. VEN Is used as a output and input pin and you should leave it open, if the LEDON LED display option is selected.