MAX3227 can't work on Low temperature with 0.1uF

[heroxue]

Hello everyone,I have just used MAX3227 for RS-232 communication at 3.3V. However, I observed that the chip doesn't function properly with C1-C4 (0.1uF 2X1 Ceramic Multilayer Capacitor) in the temperature range of -30 to -10℃. Surprisingly, it works at -40℃. I tried increasing the capacitance of C1-C4 to 0.2uF, and occasionally, it starts working properly (at -30 to -10℃), and it still works fine at -40℃. When I increased the capacitance of C1-C4 to 1uF, the chip works flawlessly across the entire temperature range. Could you please help me understand the underlying issue?

Kun.

[David Hess]

What dielectric are the ceramic capacitors using?  The higher class dielectrics lose capacitance outside of their temperature range.

[wraper]

There are several things in question here. Is MAX3227 genuine? Is it variant that is rated to operate at negative temperature or just 0°C to +70°C (although they still most likely would work the same). What ceramic type? Is it X7R, Y5V or what?

[heroxue]

What dielectric are the ceramic capacitors using?  The higher class dielectrics lose capacitance outside of their temperature range.

type 2 dielectric (X7R)

[heroxue]

There are several things in question here. Is MAX3227 genuine? Is it variant that is rated to operate at negative temperature or just 0°C to +70°C (although they still most likely would work the same). What ceramic type? Is it X7R, Y5V or what?

The chip is a genuine chip, rated at -40 ° C to+85 ° C, and approximately 10% of the chips (out of a total of 100 chips) cannot operate at negative temperatures. The capacitor material is X7R，It seems that the change in capacitance value is not the true reason why the chip cannot work, and the temperature range of X7R capacitance value reduce in the entire temperature range shown in the figure is inconsistent with the temperature range at which the fault occurred,It cannot explain why the chip can work at -40 ℃.