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MAX660: MAX660MX/NOPB

Allison Ma
Prodigy 230 points
Part Number: MAX660

Hi ,

The customer in the process of using a fault, the situation is as follows, please help find the cause, judge whether the product has a problem, thank you.

1、 Fault phenomenon

MAX660MX starts and works normally when the ambient temperature is higher than 20 ℃; when the ambient temperature is between 0 ℃ and 20 ℃, there will be power on delay start, and it works normally after start, with delay time of about 3 ~ 15 seconds; when the ambient temperature is lower than - 15 ℃ ~ 0 ℃, the power on delay time becomes longer, about 20% of the power on will not start; when the ambient temperature is lower than - 15 ℃, all the power on will not start. The input voltage of MAX660MX is DC5V. When the chip does not start or the input voltage drops to DC1.7V during the delayed start, the instrument cannot start normally.

2、 Circuit design

The circuit unit is to provide + 5V and - 5V DC power supply for instrument control panel CPU and detection circuit.

VCC12V maximum supply current: 800mA

VCC5V maximum supply current: 200mA

VCC5V working current: 30mA ~ 40mA when the instrument works normally

3、 Circuit test results

MAX660MX chip is used to disconnect the power supply circuit (e.g. x), connect the ammeter and fuse in series, and the fuse specification (200mA) will blow when the delay start occurs. If C44 and C49 are replaced with 1uF / 16V tantalum capacitors, and C45 and C50 are replaced with 10uF / 16V capacitors, MAX660MX can start normally when the temperature is higher than - 20 ℃, and delay start and no start will appear when the temperature is lower than - 20 ℃.

According to the original circuit design, the capacitor will not be changed. If the MAX660ESA is replaced, it can start normally at - 40 ℃ without fusing the 200mA fuse.

Disconnect at the red arrow in the figure and connect the ammeter and fuse.

4、 MAX660MX batch specification

5、 The test results show that the chip has quality defects in low temperature environment and needs to be returned. If there are other reasons or no evidence of quality problems, please reply as soon as possible. Thank you.

  • 0
    TI__Guru 61535 points

    Hello Allison,

    I am confused by the last sentence: According to the original circuit design, the capacitor will not be changed. If the MAX660ESA is replaced, it can start normally at - 40 ℃ without fusing the 200mA fuse. What is MAX660ESA?

    What happens if you are using 10uF/16V ceramic capacitors for C43, C44, C46, C48, C49 and C50?

    If this does not help, please remove L5 and check if U10 starts then at all temperatures with the 10uF ceramic caps on VIN, VOUT and CFLY.

  • 0 in reply to Brigitte
    TI__Guru 61535 points

    Hello Allison,

    As I do not hear back from you, I expect that you solved the issue and will close the thread now. If this is not the case, please post below or if this thread is already locked, please create a new one.