Description: IC MCU 8BIT ROMLESS 68PLCC
Product Packaging marking:
MCU functions properly at rated temperature except for when power is cycled. When power cycling at temperatures greater than 110°F MCU appears to malfunction indicated by LEDs used to monitor MCU.
We are using a processor supervisor (ADM698) which on power up holds the reset line low for 140ms after Vcc rises above the reset threshold (4.65V). Note the reset time increases with a rise in temperature.
Looking at the E-Clock output (Fig.1) before reset looks normal up to the rated temperature of 185°F. When power is cycled at temperature above 130°F the E-clock output looks abnormal (Fig.2). It worth mentioning that the reset pin remains high at 5V when the processor locks up.
Please be aware that the MCHC11F1CFNE4 Product Information|NXP is not recommended for new design.
All the boards are failing? can you check that when you perform the power cycle you meet the power up-spec
Please check the following application note
I hope this will help you