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Part Number: TPS65185
Happy holidays !
Some of us need to work during Christmas and having issues with the TPS65185...
Setup is a new board, proved design and basic typical application schematics implemented. while powering up the WAKEUP and POWERUP signals by order, the device is alive and I2C operates. But, power rails are down and VCOMF is reported via INT2 register (value is 0x04).
The issue is that VCOM_CTRL is kept LOW and while measuring VCOM it shows ~0v. VCOM1 & VCOM2 registers reflects their default value. Even setting VCOM to 0x0 does not show any change.
Also, using the I2C to POWERUP - writing 0x80 to ENABLE (0x01) register behaves the same .
VN signal is attached. VB is constantly on 5v (=VIN) .
Any idea what might cause this?
thanks a lot for your help in advance!
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In reply to Richard Solarski:
Hi Rick, happy new year!
Thank you for your help here.
Double checked the thermal pad, it is connected to VN & VEE_IN (not connected to GND ). In the last post the both images where for VN .
I would expect VN_UV fault but I never saw it, only the VCOMF for some reason.
Please see attached new screenshots at 20msec/div. Blue = VN , YELLOW = 5v VIN:
appretiate your help!
In reply to G M:
All of the devices tested (4) till now have this issue, even tried to manually replace the device on 2 boards, got the same result.
in another test, I see difference in behavior in case the VCOM1 is set to 0x7D (reset value) or 0x10 (see below). Seems that the VN is not generated so the VCOM generates positive voltage and hence VCON fault, make sense?
In addition, please examine the schematics . pls note these small fixes already implemented : R45 is removed, VB connected to VDDH_IN, added 10uF cap from VN to gnd.
appretiate your support!
looking forward for any ideas.
Pls see below the scope shots , VN_SW in Blue, VCOM in Yellow.
This is another device with closer caps.
After placing additional cap on A1 of U17, as you've suggested, I see improvement of the VN signal, and now it drops to -8v and VN_UV is generated.
VN is in yellow.
What might cause VN not to be able to reach its -16v?
Thanks for your help so far!
No, the VCOM_F does not occur anymore. Now the VN_UV is constantly occurring.
You can see below the signals of VN_SW and VN:
I've tried to increase the cap of C78 to 10uF and reduce it, no change.
The VIN is extremely stable, injected from external power supply @ 5v with practically no current limit.
Any idea how to proceed ?
Can you confirm the current rating of your rectifying diode? From the schematic it looks like it could be 150mA, but the switching current limit of VN is typically 1.5A. Our EVMs implement 1A average rated diodes capable of 5A peak
I do not see a clear low side in the switching cycle, and if the diodes cannot handle the switching currents it could explain this behavior.
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