| ??? 07/17/06 03:41 Read: times |
#120350 - LDOs are prone to oscillate! Responding to: ???'s previous message |
Dileep said:
5V LDO (Micrel make) – 10 uF tantalum and 0.1 uf mlc at output - Vout LDOs don't like certain caps at output! If the equivalent series resistance is too low, most LDOs become unstable and tend to oscillate. Maybe you should omit the 100nF? Tell us the exact part number of LDO. Dileep said:
Vout is given to analog Vcc of ADC through a ferrite bead and a 0.1uF mlc to GND- Va Put a 10µF tantal in parallel to the 100nF cap. Use ceramics X7R for the 100nF cap, not mylar. Put a resistance of 1...2R2 in series to the ferrite to suppress ringing of this LC filter and to isolate its complex impedance from the LDO(see above!). Dileep said:
Initially they were all ok but 25% of them failed within a day. How does this failing look like? Maybe it's a damage due to ESD at inputs? What is connected to the inputs of ADC? Kai |
| Topic | Author | Date |
| AD7798 with 89S52 - ADC failure | 01/01/70 00:00 | |
| Draw it | 01/01/70 00:00 | |
| Input Protection. | 01/01/70 00:00 | |
| LDOs are prone to oscillate! | 01/01/70 00:00 | |
| ADC failure | 01/01/70 00:00 | |
| what do you have on the ports | 01/01/70 00:00 | |
| Nature of the failure? | 01/01/70 00:00 | |
Nature of failure | 01/01/70 00:00 |