In hand development base station circuit board testing, after get the test environment problems (may be due to the ambient temperature is higher, and the base station is made of black metal shell, exposure under high temperature) now measuring found no output voltage, DC - DC chip are theoretically should be able to do 12 v to 3.3 v, help you a great god specific how to examine the issue in the case of no change chip reasons, whether DC chip damage, or simple capacitor, resistor and inductor is damaged, (the chip is a little small, I welding technology can not reach, otherwise will try again in a chip),

CodePudding user response:

Over here is the circuit diagram I have no voltage measurement of FB pins, but there are other pin voltage, I am wondering if there is something wrong with the chip are no voltage

CodePudding user response:

If there is a voltage LX pins, voltage and FB pin not only two reasons: 1 chip is broken, cause FB signal is short circuit, as well as R1303 open, cause no output sampling circuit,
Not ah, you not is say the feet have voltage, voltage that LX pin is the output voltage, how can not output? Chip bad possibility is very large

CodePudding user response:

First drawings has written a lot of measurement condition, DC - DC is a few key points:
1, VIN (input) whether normal
2, FB reference voltage is normal (wrote this 0.9 V, the average 1% difference)
3, EN open whether high level

In addition you said have voltage, voltage is how much is the key

VOUT output (i.e., LX pin) actually? (drawing design is 3.9 V output) 0.9 * (100/30 + 1)=3.97 V, the standard resistance partial pressure circuit

If the output voltage on the low side, check and R1302 FB foot, R1303 (need to disassemble to measure resistance)

LX pin multimeter can only measure about, actual test need oscillograph, this is PWM square wave, but you can measure inductance (L1301) behind the LX voltage is 3.9 V to know

This is difficult to chip in, blower gun in two minutes