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MAX660: About MAX660MX power-on startup issue

人在江湖
Intellectual 705 points
Part Number: MAX660

First, fault phenomenon

MAX660MX starts and works perfectly when the ambient temperature is greater than 20℃;When the ambient temperature is between 0 and 20℃, there will be a power-on delay start, which works normally after starting, and the delay time is about 3~15 seconds.When the ambient temperature is lower than 0℃, the delay time of power-on starts becomes longer, and about 20% of power-on does not start.The input voltage of MAX660MX is DC5V. The input voltage drops to DC1.7V when the chip is not started or the input voltage drops to DC1.7V in the process of delayed start, which results in the meter cannot be started normally.

Second, circuit design

The circuit unit is to provide +5V and -5V DC power to the instrument control board CPU and the detection circuit.

Third, Circuit test results

Disconnect the power supply loop and connect the ammeter and fuse in series. The fuse specification (200mA) will be blown when there is a delay start.The replacement of MAX660ESA can start normally at low temperature -40℃, and will not blow the 200mA specification fuse.

Fourth. The MAX660MX batch specifications

  • 0
    TI__Guru 59605 points

    Hello 人在江湖,

    Would you please check the following: Replace the 0.1uF ceramic capacitor on the input with a 10uF capacitor and remove the 10uF tantalum capacitor on the output or replace with a 1uF tantalum capacitor.

    Ceramic capacitors have DC bias and temperature dependent capacitance values and it is possible that the output capacitor is discharged too fast by the tantalum capacitor at different temperatures.