TI E2E Community
Signal Switches Forum
TS5A3159A switching issue
We have an issue with the TS5A3159AYZPR where it is basically used as a tri-state buffer. Normally Open (NO) is tied to a CPLD signal this is used a Chip Select for a battery backed SRAM. NC is left floating, and IN is tied to a voltage level detect circuit that monitors if main power is present, or if the system should switch to the backup battery. V+ is tied to a 3.3V rail produced by main power. The thought was that as main power is lost, IN would go low, switching NC to COM, turning it into a high-Z line. The CS_N (COM) is pulled high through a 10k to Vbackup battery (3V).
Instead, the COM seems to follow V+ and NO slowly down until power is almost completely gone. This is causing the CS_N to fall briefly and corrupting the first byte of the memory. We've tried holding IN low while V+ is still fully powered, and then removing power. COM falls a little faster, but still isn't high impedence until V+ is really low.
Is there something internal to the part that would prevent an open NC pin from looking like a high-Z line when connected to COM? or anything else that could explain this performance?
The part will not function without V+. The reason it looks like it kind of works is because when V+ gets low enough the switch just goes open. NO and NC will both be open with no power.
Why does the COM pin fall low when V+ is falling instead of just being open?
The part should be open when Vcc is between approximately .8V and 0V. The .8V can vary by technology and is not a guarranteed number or anything just and observation.
Then between .8V and 1.65V anything could happen since this is and invalid Vcc.
From 1.65V to 5.5V the parts should function properly.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.