Part Number: LMP91200
want to test pH sensor amplification part before it incorporating to complete design __kindly verify and advice on below details
Q1) Can we use simple any 2 pin Connector for connecting pH Sensor to PCB, with using Coaxial cable and proper Guard and ground connection mentioned in attached design.
Q2) Can we we short Pin 10 to Pin 15,16 because we are using same supply for Tl431_2.5Vdc and LMP91200
Q3) what will be my output voltage range with +2.5v as Vref and +5V as a VDD (ph Sensor Range -414mV to +414mV)
Hi Rahul, Please find my comments below: 1. As you can read on section 10 (Layout) of the data sheet the recommended connector is a triaxial connector. Your PCB and schematics don't look like like a coax connector, it looks like the one on section 10. 2- Yes. You should short Pin 10 to pins 13-15-16 since all of the are ground, as shown in your schematics and page 3 of the LMP91200 data sheet - www.ti.com/.../lmp91200.pdf 3- The Ph Amp is a Unity Gain buffer so it will track the swing from your sensor output and will be referred to the VCM Voltage. Regards, Jose
In reply to Jose Arteaga4:
1) i have taken exactly same tracks and same PCB layout pattern for pH sensor, can you re-verify. kindly Ignore schematic symbol for triaxial connector just taken for SCH reference and taken care in PCB layout.
2) Ground point is clear..Thanks
3)- The Ph Amp is a Unity Gain buffer so it will track the swing from your sensor output and will be referred to the VCM Voltage.
__Sorry unable to understood above point it means what.
my pH ouput is -414mV to +414mV
Vref will be at +2.5V
All Vcc/VDD is at +5V
Need Vout range available for ADC = ? _______(with respect to mentioned voltages)
it will help me whether we need to amplify signal with proper gain and another opamp IC or will get amplified version at vout of IC LMP91200 (pin num 12 )
In reply to Rahul Joshi10:
1) Your PCB layout look exactly the same as the recommend example provided in section 10 of the LMP91200 data sheet. This is for a Triax cable. Can you explain to me what are the differences?
3) Unity gain buffer means that output amplitude is the same as input. (-414mV to +414mV)+VCM
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.