| ??? 02/28/11 12:37 Read: times |
#181332 - Sometimes driven chip starts to operate from ghost power Responding to: ???'s previous message |
Michael Karas said:
Edit: Let me add - If an "off" device's high side input protection diode tries to clamp the signal line voltage to the ~1.2 volt level that I mentioned it is possible that the clamp level voltage may rise higher as the "off" device tries to power itself up internally. Due to this behavior it is possible to see the clamping voltage level which may rise to even over 2 volts and becomes dependent on source impedance of the signal line coming from the MCU. Karas Yes, I have accidentally managed to power modem chips so they start running their crystal oscillator by just forgetting to tristate the SPI slave-select line when the modem was turned off. Lots of "funny" things can happen when a powerful microcontrollers drives an output high, and that output goes to an unpowered chip. |
| Topic | Author | Date |
| Devices in Parallel in Board | 01/01/70 00:00 | |
| Not generally a good idea! | 01/01/70 00:00 | |
| Any solution | 01/01/70 00:00 | |
| Solution for what? | 01/01/70 00:00 | |
| Or sometimes resistors | 01/01/70 00:00 | |
The real question is... | 01/01/70 00:00 | |
| Devices Connected To Same Pins | 01/01/70 00:00 | |
| Sometimes driven chip starts to operate from ghost power | 01/01/70 00:00 | |
| the thrack sound | 01/01/70 00:00 |