As title, for help ~ ~ ~
Has been playing board and modified three times!!!!! The problem remains.
According to TPS5430 data book design and layout, type 12 v, 5 v output, chip maximum load 3 a,
Phenomenon:
1: when the light (bright two LED work lights, only not connect other components), DCDC 4.96 V output, output "3.3 V, normal
2: hang two STM32F4, A display, load about 1.2 A, after connect, DCDC output was down to about 4.5 V,
3: they are down to 2.8 V, on the board a lot of 3.3 V parts can't work normally, such as single chip microcomputer, crystals...

The screening process:
1: the element, is jia made a single, can eliminate components.
2: the output capacitance of the DCDC size, replacing the 10 uf, 220 uf, 330 uf, 1000 uf aluminum capacitors, tantalum capacitors, solid capacitors
3: DCDC input capacitance size, should not influence, but also changed the model, the same as
4: power inductors, uh, in a number of
5: "chip, replacing the LM and AMS,
6: "input and output capacitance, replacing the

CodePudding user response:

reference 1st floor weixin_39573414 response:

the building Lord, problem solving,

No, you also have this problem?
Cleared again last night, in the thought that the question may not be out in DCDC section, the output voltage will be load after lower?

CodePudding user response:

L3 inductance is too big or small for impedance?
Try four inductance (two) and two series of increasing the inductance at the same time reduce the dc resistance

CodePudding user response:

The

reference 3 floor zgl7903 response:

L3 inductance is too big or small for impedance?
Try four inductance (two) and two series of increasing the inductance at the same time reduce the dc resistance

Received, I try,,,,,,,

CodePudding user response:

Level before power is enough?

CodePudding user response:

Check after the loading of the input voltage will there be a subsidiary

CodePudding user response:

In addition, must consider the inductance of the power capacity, power capacity is not enough makes inductance into saturated state

CodePudding user response:

15 uh is a bit big, the output to 3 a, saturation current at least 4 a, inductance volume is too big, and slow response, considering the switching frequency of 500 KHZ, 10 uh how impedance is enough, to choose a high temperature saturated current of 5 a very reliable

CodePudding user response:

Just watch the datasheet, 5430 principle figure do not have what problem, 15 uh inductance also no problem, inside the datasheet reference circuit is 15 uh, I think problem is likely to be out on the PCB, floor problem can contact me, I have been use TPS5450, have never been on a problem,

CodePudding user response:

references a ray of sunshine, 9/f, best response:

just looked at under 5430 datasheet, schematic diagram do not have what problem, 15 uh inductance also no problem, inside the datasheet reference circuit is 15, uh, I think the problem is likely to be out on the PCB, floor problem can contact me, I have been use TPS5450, never had problems,

Well, thank you first,
Already find direction, should be the problem of constant current, load a display screen, LED to constant current,