DCDC no output

290627303

DCDC no output [Copy link]

 

PVDD33 has 3V3; AVDD33 has 3V3; DCDC_EN has 3V3; DCDC_IREF has 0.5V; DCDC_SW has no output; I have changed the IC, but it still doesn’t work; I have no idea.

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qwqwqw2088

What is U7? The question is, what is the use of crying?

philipchiu

The model of the core parts is not marked, how can anyone help you?

philipchiu

The model of the core parts is not marked, how can anyone help you?

_xiaomi

Did you solve this problem? This CX20921-21Z is a voice chip. . . Do you have a manual? Please post it for us to see. . .

gmchen

Mark the device model!

ienglgge

There should be an application circuit in the manual. Compare it. In principle. What is the difference between this diagram and the official recommendation? Check each pin to see if there is any error. Analyze the signal flow carefully.

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qwqwqw2088 posted on 2018-2-6 20:50 What is U7? The question is what is the use of crying?

U7 is a voice processing chip SOC

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philipchiu posted on 2018-2-7 00:37 The core parts model is not marked, how can I help you?

Sorry, the model is CX20921-21Z

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_xiaomi posted on 2018-2-7 09:24 Did you solve this problem? This CX20921-21Z is a voice chip. . . Do you have a manual? Post it here for us to see. . .

The manual is very simple, and only briefly describes an application scenario for this device. The electrical part is very sketchy.

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ienglgge posted on 2018-2-7 12:37 There should be an application circuit in the manual. Compare. In principle. What is the difference between this diagram and the official recommendation. Check each pin to see if there is any error...

I did it according to the recommendation, no difference. The output of the crystal oscillator and DCDC are both gone. Now I am not sure which one worked first, the IC or the crystal oscillator, the manual does not say

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ienglgge posted on 2018-2-7 12:37 There should be an application circuit in the manual. Compare. In principle. What is the difference between this diagram and the official recommendation? Check each pin to see if there is any error...

The device manual is consistent.

qwqwqw2088

290627303 Posted on 2018-2-7 15:07 I did it according to the recommendation, no difference. The output of the crystal oscillator and DCDC are both gone. Now I am not sure which one worked first, the IC or the crystal oscillator. The manual does not mention it.

I have not read the manual of this chip. It seems that the problem is that the power supply is abnormal. If the 24M crystal does not oscillate, it means that the chip is not working. The crystal oscillator starts to work, but it is not necessarily working normally. You need to check the welding and assembly, and check the circuit design and component parameters according to the manual.

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qwqwqw2088 posted on 2018-2-7 16:03 I haven't read the manual of this chip, it seems that the problem is that the power supply is abnormal. The 24M crystal does not oscillate, which means the chip is not working. The crystal oscillator starts to work, but it does not...

The resistance value of Iref is incorrect, resulting in incorrect reference current; DCDC reference is incorrect, 1V is not output, causing the crystal oscillator and IC core to not work. Changing the resistor will fix it.

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_xiaomi posted on 2018-2-7 09:24 Did you solve the problem? This CX20921-21Z is a voice chip. . . Do you have a manual? Post it for us to see. . .

Solved.

_xiaomi

Hmm... I've learned something...