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Tool/software:
Dear TI
I have realized a board with TPS55289 but I am not able to have a VOUT out of it. The VIN is 4V and the Enable pin is HIGH with a digital MCU at 3.3V. The output is 3.58V
These are the reading of registers
0x00 register 164 bin= 10100100
0x01 register 1 bin= 00000001
VOUT_FS register 3 bin= 00000011
STATUS register 2 bin= 00000010
IOUT register 0 bin= 00000000
MODE register 160 bin= 10100000
VOUT_SR register 1 bin= 00000001
CDC register 224 bin= 11100000
I attach the schematics. Thanks for your help
Hi Riccardo,
Thanks for reaching out.
1. What is the output current when you don't see Vout on that?
2. From the register values, I think the device was switching. Can you share the layout and waveforms of VCC, SW1, SW2, Vout at one screen?
3. Do you mean there is 3.58V on the output side?
BR,
Bryce
Thanks Bryce
The VOUT pin is not connected to load so I=0
Yes there is 3.52V at the VOUT side (it does not change with changing register values for output)
Thanks for you time
Ric
Hi Riccardo,
Thanks for feedback, have you tried to move the device on another board to see if anything changes?
From the screenshot of layout, the layout is very poor especially for power paths and VCC routing, we have seen many abnormal phenomena because of poor layout, please strictly follow the attached layout guideline when doing layout.
4667.TPS55289 Layout Guide line.pdf
BRs,
Bryce
thanks Bryce
I will try a new layout following the guidelines. Btw Is the schematics ok? thanks
Hi Riccardo,
To proceed the sch review, I need below information to check:
1. Can you share the input voltage range, output voltage range and max output current with us?
2. What is the part number of C7-C11, the ESR value and effective capacitance are needed to check COMP parameters.
BRs,
Bryce
Hi Bryce thanks for your reply. I indeed replaced the TPS55289 with the TPS55287 and the system work. I mean I can regulate Vout by I2C smoothly. However when apply a load with the following parameters VIN=3.5V VOUT=7V with a resistive load of 11ohm (typically then 0.7 A) although the input current reading from power source is about 2 A@3.5V. I have the following inductor TMPV 1054SV-4R7MN-D, should be in specification. C7 is 100 uF 35V 36mohm C11 4.7uF X5R and C17 (Vin) 68uF 36mohm. Thanks for your comments Ric
Sorry I forgot to say that when apply the load as described before the Vout drop off. I can sustain the Vout only if I increase VIN to 3.8-3.9 then it handle the Vout. Thanks Ric
Hi Riccardo,
If TPS55287 can work, I doubt if this is also related to soldering reliability.
The poor layout would introduce much parasitic parameters into the power loop, and resulting in large Vin/Vout ripple and SW1/SW2 voltage spike, which would cause abnormal operation. It is still recommended to redesign the layout from my side.
BRs,
Bryce
Thanks Bryce I do agree. Now I am designing a new layout with the TI recommendations.