Page Contents
Power Supply
Requirements
| Description | Total | |
|---|---|---|
| 1 | MCU (STM32G0B1) 3.3V 10mA, at max settings | 10mA |
| 2 | BassStation I/O 5V 8uA; each ch, drawn from bass station connector | 8uA |
| 3 | RGB LED Driver IC (TLC5955) 5V 2 x 1.5A (500mA per colour group) | 3A |
| 4 | Keyscan IC (ADP5587) 3.3V 200uA per key pressed 50uA per GPI Low (Pull-Up Enabled) | 250uA – 1.3mA |
| 5 | Crosspoint SW IC(ADG2188) 5V 1.7mA interface active (full speed I2C) | 1.7mA |
| 6 | 2.42″ OLED, 3.3V | 250 – 500mA |
Choosing chips
We need at least two voltage rails: 3.3v and 5v. That’s easy enough to achieve with LDO regulators stepping 5v down to 3.3v.
But we also need to provide a significant amount of current for the 5v supply to the TLC5955 LED driver. There are several options:
- Isolated DC/DC converter modules. These are COTS modules that are simple and compact but costly at this power consumption level. Regulated modules are most useful, but again this just adds to the cost.
- Buck converter with integrated mosfet. These are small (SOT-23) and therefore very cheap, but require a number of passive components which increases BOM and layout size. They are also limited to about 3A but that should be “good” match for this design (I’m not planning on running these LEDs at full brightness). Did I say they were cheap. The TPS563200 is only 36p each in 1000 quantity…not that you can find any stock at the moment.
- Buck controller with external mosfet. These can achieve much higher current output and would be the best choice if I needed more than 3A.
In case you hadn’t already guessed I picked option 2.
Final Design
Here is a quick block diagram for the design:
The 12V input goes into a PMOS-based polarity protection circuit. That is then regulated down to 5V by two TPS563200 buck regulators: One is dedicated for the LED driver and the other is for everything else. Everything else is split between two LDOs: One that provides about 100mA for the MCU, the ADP5587 and ADP5587 chips; and one that provides 250-500mA for the OLED display.