| ??? 07/01/09 21:07 Read: times |
#166634 - which SiLabs part? Responding to: ???'s previous message |
Raj Nambiar said:
We have been in contact with Silabs Europe. They have cautioned me against using the inbuilt POR. In built POR has no supervisor while the chip starts up, we were informed. (Even though the manual says the reet pin will be held low till VDD reaches VRST ie 2.7V, in the block diagram, they have separated VDD monitor and POR. We need to refer to the block diagram and not the confusing text below that). The VDD rise time required for Silabs is 1ms, and if the rise time is more than that ... Which SiLabs part are you talking about? I'm looking at the data sheet for the '005 and it absolutely does have a power-supply monitor. In fact, its /RST signal is an open-drain OUTPUT, which can be overriden by an external reset if required by the application. And from the data sheet, "The external /RST pin provides a means for external circuitry to force the MCU into a reset state. Asserting an active-low signal on the /RST pin will cause the MCU to enter the reset state. Although there is a weak internal pullup, it may be desirable to provide an external pull-up and/or decoupling of the /RST pin to avoid erroneous noise-induced resets." So for many applications, you provide the pull-up to ensure that you don't get spurious resets, but never a capacitor on /RST! The eval board does have a capacitor between /RST and GND, but that's to debounce the pushbutton reset switch. -a |
