As the title states, I'm curious to identify a failed, unmarked 6 pin MCU in a SOT23-6 package. It's on the controller board for a magnifying glass LED lamp. I've posted some information and the schematic in a separate post here:
https://www.eevblog.com/forum/projects/why-different-pulldown-resisors-for-otherwise-identical-led-drivers/The requirements are:
- Capable of operation at 5V
- Vdd (5V) on pin 5
- Vss (GND) on pin 2
- Pins 1 and 6 can be set as inputs with the capability to enable both an internal weak pullup or weak pulldown (one at a time).
- The minimum to maximum range of the pulldowns are such that a resistor divider formed from a 10K upper and pulldown lower will produce a voltage at 5V that will be read as a HIGH on these inputs. (Note 1)
- The min. to max. range of the pullups and pulldowns are such that a resistor divider formed from one of each will produce a voltage at 5V that will be read as a HIGH on these inputs. (Note 1)
- Pins 3 and 4 can be set as outputs with PWM capability. (Note 2)
Note 1: If the resistor dividers don't produce a voltage read as HIGH but pins 1 and 6 can be read with an internal ADC, that would be acceptable.
Note 2: If pins 3 or 4 aren't PWM capable, the PWM could be produced on them using software bitbanging. (In this case, having at least one timer peripheral would be helpful.)
Taking into account notes 1 and 2, there are likely a number of parts that fit the bill, with the input pulldown capability being a fairly limiting factor. However, I'm curious if there are any MCUs that fit all these requirements without needing to use the notes. I've done some searching and haven't found anything that wouldn't require at least bitbanged PWM.
Note that this is really just for my curiosity. I plan to try to fix the lamp but not using a compatible MCU even if I discover one. I'm planning to use an ATtiny13A SOP-8 mounted on the original board "dead bug" style with wires from the pins to the board. This way, I won't need a specific pinout. Having the additional 2 MCU pins, I'll cut some traces to isolate the buttons so there can be a single button per pin, thus only needing internal pullups, not pulldowns.