LMT84: output oscillation

Allan Fan

Other Parts Discussed in Thread: LMT84, ADS1015

Team,

Here is customer's schematic of LMT84 following with ADS1015. They've done some tests from 25C to 75C but always seen +-50mV sine wave at output of LMT84. Is it possibly resulted from wrong Cload and Rs combination? If so, may I know how does the table value come from datasheet page12 and how to get appropriate RC value if choosing different type of ADC?

Vcc=5V, C1=680pF, R1=33ohm, C2=0.1uF

Regards,

Allan

over 7 years ago

0 Michael Wong over 7 years ago

TI__Expert 7220 points

Hi Allan,

The output of the LMT84 will oscillate if it sees a large capacitive load at its output. The value of C2 is considered large in this system, I'm assuming this is used as a bulk capacitor for the input of the ADC. If so, C2 does not need to be so large, maybe a 1nF or a 0.1nF should be fine. The values of C and R's on the datasheet are from experimentation on the bench. Let me know if this solves the problem.

-Michael Wong

0 Allan Fan over 7 years ago in reply to Michael Wong

TI__Expert 5740 points

Hi Michael,

Customer remove C1 and change R1 to 1.5Kohm. The issue is resolved. Thanks.

Allan

Sensors

Sensors forum

LMT84: output oscillation