Other Parts Discussed in Thread: LM2991, TPS7A3001-EP
We use the above circuit for generating -2.7V from -5V input which is used as the reference voltage for the ADC AD9012. When we have tested this with 274ohms load individually (10mA load current) performance was normal (pure DC). When it is connected to ADC ref pin (w/o load resistor), we are observing ouput oscillations. Plot is attached. The actual load current for the ADC ref is in microamperes. Kindly provide a detailed explanation for the follwing. Your datasheet doesn’t provide a reference schematic for the above application.
1. We used this capacitor to avoid any external noise pickup to the adj pin based on earlier practise. Earlier we used LM137WG.·
2. Implication of using 0.1uF capacitor or any capacitor at the adjust pin. Whether it will lead to oscillations in the output voltage.
- 3. C3 is a ceramic capacitor. If we use R2 of value 10 ohms or above will it lead to oscillations at the output. What is the max series resistance and capacitance that can be used at the output?
- 4. Below -3V, slope is different from above -3V. Why is it so?
- 5. Device says op voltage of –2V to -25V. Can we generate -2.7V?
- 6. Earlier, we have observed oscillations at -5V input when series resistance of R2 is not used. Why so? Oscillating pattern was sawtooth.