Hello!
We are using the LMP90100 in our precision pressure measuring instrument. Three pressure sensors are connected on three differential channels of the LMP90100 respectivly.
At some of the devices, there is a great disturbance (about 10uV) on the readings of some of the three differential channels, but not at all differential channels. The replacement of the pressure sensors through resistor networks which simulate the wheatstone bridge of the pressure sensors brought no improvement. The use of an external excitation current source instead of the internal brought also no improvement.
At some devices the disturbance on the readings on some channels (e.g. VIN0, VIN1) are about 2-3 uV, that's OK. At other LMP90100 devices on the readings of the same channels (e.g. VIN0, VIN1) is a great disturbance of about 10uV. The software, the electrical circuit, the layout of the pcb and the electronic assembly for the LMP90100 are always the same.
The electronic assembly with the LMP90100 is produced through an external supplier. He uses a vapor phase soldering process. The pcb is a multiplayer pcb with 6 layers with devices on both sides. Our external supplier bought the LMP90100 devices at a distributor like Mouser.
At the moment, we suppose that this LMP90100 devices were damaged at our supplier. This damage could be stem from a omitted backing or omitted tempering before the vapor phase soldering process or trough overheating in the vapor phase soldering process itself.
We have also noticed that the pads for the LMP90100 (HTSSOP package) have not the right pitch. The pitch of the HTSSOP package is 0.65mm, our pitch of the pads for the LMP90100 is 0.025 inch (0.635 mm). For that reason the outer pins of the LMP90100 on the pcb are bent.
We suppose that through this bented pins or through overheating in the vapor phase soldering process there could be micro cracks in the molded plastic package of the LMP90100 which leads to a partial damage (only some but not all inputs) of the device.
How do You think about this issues?
Thank You for Your help in advance!
Best regards,
Joachim
