Part Number:TPS63000
Tool/software: Webench
Hello,
my customer choose TPS63000 as buck-boost for 2 power rails with same schematics.
Characteristics of scheme:
Vin range - 2.4 to 5.2 V.
Schematic is typical (see figure 2 on page 10 in datasheet).
Cin = 22 uF, Cout=66..110 uF, L = 2.2 uHn.
There are 2 Vout's:
- 3.3V (40-300 mA load)
- working fine on all Vin
- 5V (0-120 mA load)
- Vin <3.4V - all's working good,
- 3.4V < Vin < 4.4 V - there are appears some short-term dips not reaching 0V at output and noise level is increased. The case of TPS63000 heats up also,
- 4.4V < Vin < 4.7 V - Vout swings until TPS63000 turns off due internal protections,
- 4.7V < Vin - TPS63000 can't start. Periodically TPS63000 has starts after all but for not more that 1 second.
Customer tried to change L from 1 to 3.3 uHn but this has no result. They tried to replace ICs between 3.3 and 5 V power rails, but result the same - 3.3V working fine, 5V working as described above.
Customer is temporally solved the issue by adding 2 diodes at Vin = 5 V, (5 - 2*0.7=3.4). But it's not good solution.
I checked schematics by datasheet and webench, but I can't found the cause because all's looking correct and should working fine as I understand.
What may going wrong and how to fix it?