MX25L5121EMC keeps getting erased , question about capacitors - Page 1
Forum section: electronics / repair

author: stojke
author_rank: Regular Contributor
timestamp: March 05, 2018, 09:47:18 pm
content: I have an sony VPCSE1E1E lap who keeps erasing its own USB 3.0 Firmware from time to time. I guess it has something to do with its power supply.Is it possible to disable write into this chip? Can this be done by removing connection to WP# signal line?And I have an question about capacitors I have been wondering about. Does a capacitor impact the circuit it is in? For example, i have an 3.3V source and I place a big large capacitor for example 10uF instead of 0.1uF specified. Does this capacitors capacity "Pull out" the voltage and make it drop below 3.3V on that rail for a short period of time? Can some one explain that relation of it inside of a circuit please? Thanks.

author: tonyh88
author_rank: Regular Contributor
timestamp: March 06, 2018, 03:03:53 am
content: This is a bit of a hard to answer one because it really depends on the circuit. Putting a larger capacitor will cause a larger current to flow when initally powering up the device. Too big of a value may upset some circuit but it might be fine as well if it is just for filtering a PSU.

author: stojke
author_rank: Regular Contributor
timestamp: March 06, 2018, 12:48:45 pm
content: It is an supply voltage for the USB 3.0 controller chip and its eeprom. Laptop had problems of shutting down just as it displays the bios image, and it was turned on and shutdown at least 20 times like that. I am thinking if this ever occurs again, random shut downs again now that it is repaired, to protect the chip from erasing it self some how by adding to it an larger capacitor. But upon further inspection it doesnt seem like it will help much as there are many more caps on this like, which brings me back to my first question:Is there a way to prevent this chip from self/on purpose erasing?

author: wraper
author_rank: Unknown
timestamp: March 06, 2018, 01:35:29 pm
content: Hardware write protection is enabled by setting WP pin low. However it protects only bits which set software write protection. Therefore software write protection must be set and WP pulled low for complete write protection. WP pin by itself won't affect data write if it is enabled in config bits.

author: Armadillo
author_rank: Super Contributor
timestamp: March 06, 2018, 02:39:20 pm
content: Quote from: stojke on March 05, 2018, 09:47:18 pmNo, WP# must be permanent pulled low and HPM [hardware protection mode] must have been activated to enable memory protection. Removing the WP# connection may release the HPM if it was enabled.The chip is driven by 3.3v power supply which also drives other critical circuits hence 3.3v problem is unlikely. The 0.1uF capacitor is placed there to reduce signal glitches and not for DC filtering. Placing a large capacitor on the circuit may place undue loads onto the switching power supply and may affect the starting up timing condition. This is definitely not advise.Can you explain how did you come to the conclusion that the firmware was erased.?If you have the ability, the easiest I would think of is to replace the CMOS flash memory with a new chip. It is not all that unlikely for a failed flash memory chip.Of course, there may be other causes for example internal software driver upgrade process initiated by the computer itself etc..

author: stojke
author_rank: Regular Contributor
timestamp: June 18, 2018, 12:17:54 pm
content: Problem was identified to bad chip. Months later still working.