Micro-Foundry-XC6194A-Discrete-Logic-RGB-Expansion-PCB

Information about the XC6194A Expansion PCB based on discrete logic to drive 3 LEDs and provide voltage translation

Why?

I utilize the TOREX XC6194A in various projects and some have the extra IO to drive the RGB LEDs. So I rolled up the design into an accessory to complement the XC6194 breakout, including a few additional features.

Description

The Micro Foundry XC6194A Discrete Logic RGB Expansion PCB provides the ability to drive a RGB LED illuminated Momentary switch or up to 3 individual LED indicators (with common anode) in addition to offering voltage translation where the XC6194A switched VCC differs from MCU VCC.

Please NOTE: Color representation is totally dependent on the LEDs utilized. Therefore, there are no guarantees this LED driver will have the ability to produce the accurate color representation possible with 3x LEDs.

Features

3 Channels of LED switching with 32mA at 5v (24mA at 3.3v) sink capability per channel utilizing Open Drain Inverters
An additional "Power State" channel to provide a sink to LED channel 1 when XC6194 is in Off State. (more details below)
Voltage translation on SW (Switch) output -> MCU input with Schmitt-Trigger input/inverted output
Anode series resistor to provide global LED current control (more details below)
On-board micro switch for additional XC6194A control
Mount holes will accept Wurth Electronics SMT Standoffs

Pinouts

Switch

Pin	Function	Description	Voltage Potential
1	SW	Momentary Switch Input (Active LOW)	XC6194A VIn
2	GND	Ground
3	ANN	Common LED Anode	XC6194A VIn
4	LED1	LED 1 Cathode
5	LED2	LED 2 Cathode
6	LED3	LED 3 Cathode

IO (to MCU)

Pin	Function	Description	MCU IO	Voltage Potential
1	GND	Ground		GND
2	VCC	Voltage In		MCU VCC
3	SW	Switch Pressed	Input (Active HIGH)	MCU VCC
4	SHDN	Shutdown	Output (Active HIGH)	MCU VCC
5	PG	Power Good	Output (Active HIGH) See NOTE-1	XC6194A VIn
6	LED1	LED 1 Driver	Output (Active HIGH)	MCU VCC
7	LED2	LED 2 Driver	Output (Active HIGH)	MCU VCC
8	LED3	LED 3 Driver	Output (Active HIGH)	MCU VCC

NOTE-1: The Power Good output is traditionally utilized to enable a downstream power supply, therefore the output operates at XC6194A VIn Potential. Please verify voltage compatibility before connecting.

Expansion

Pin	Function	Description	XC6194A IO	Voltage Potential
1	VIn	XC6194A Switched Voltage In		XC6194A VIn
2	GND	Ground		GND
3	VOut	XC6194A Switched Voltage Out		XC6194A VOut
4	SW	XC6194A Momentary Switch	Input (Active LOW)	XC6194A VIn
5	PG	XC6194A Power Good	Output (Active HIGH)	XC6194A VIn
6	SHDN	XC6194A Shutdown	Input (Active HIGH) See NOTE-2	GND

NOTE-2: Circuit is pulled to GND via pull-down resistor. XC6149A datasheet specifies a voltage level above 1.1v will trigger shutdown. Some MCUs may exhibit an output glitch on the SHDN during power-up and the XC6194 may immediately shutdown. If this is experienced, a user implemented RC filter could possibly eliminate the issue.

Power State Channel

Channel 1 LED has a secondary open-drain buffer with its input referenced to VOut. When the XC6194A is in its off-state, the logic will illuminate the Channel 1 LED. This can be useful to provide a vsual indicator that the power is off. When the XC6194A is in its on-state, the secondary open-drain output is in a high-z state and the primary Channel 1 LED open-drain inverter is free to drive the LED. If there is no desire to have the Channel 1 LED illuminated when the power is off, this feature can be disabled by removing the resistor as indicated in the following image:

TODO: Add image to indicate R2 removal...

Anode Series Resistor

The resistor noted in the following image offers global current control via the common anode pin. The default value as manufactured is 0 Ohms (Zero) and can be replaced if necessary.

TODO: Add image to indicate R3 location...

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