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GPIO Expander

It’s difficult to foresee the needs of your project from the start. Choosing an MCU with the exact right amount of IO at the beginning of a project, may not be sufficient as requirements creep in and unforeseen engineering challenges occur during development. Adding differentiation to your project can be challenging as well, since most MCUs available are available to everyone. So, how can you easily add new features when you’ve used all the IO available already? How can we expand the number of IO? With the new I2C block, GreenPAK™ 5 makes an ideal GPIO expander allowing you to add new features, logic, timing, and sensing to already highly integrated designs.

gpio 1

GreenPAK™ Benefits as GPIO Expander:

System Stability

  • GreenPAK is 100% hardware - Implementing features in hardware ensures stability
  • GreenPAK can integrate many components ensuring fewer points of failure

Power Consumption

  • GreenPAK is low-power

Configurable Pinout

  • GreenPAK GPIO routing is flexible – Ensuring the least complexity in PCB routing


  • GreenPAK is as small as 1.2 mm² - In mobile and wearable electronics, every mm counts

Configurable GPIO

  • GreenPAK signal routing is flexible – PCB layout and routing
  • GreenPAK I/O are configurable – Pull-up/down resistors, Push-Pull, Open drain, etc.
  • GreenPAK logic is configurable – Active-low/high

Expanding GPIO

Using GreenPAK’s I2C block allows for easy expansion of both input and output. With simple I2C commands the matrix input of each component on the chip, including the GPIO, can be read, expanding input. With simple I2C write commands, I2C virtual inputs can push digital signals into the device or directly to GPIO.

I2C Virtual Inputs

Key Design Considerations

  • IO Configuration – Configurable pull-up / pull-down resistors on GreenPAK’s GPIO make communicating with any IC a snap.
  • Initial values – Using GreenPAKs OTP NVM, it is easy to set initial output values
  • Latching during Write – GreenPAK can be set to latch IO during write or update values as soon as a bit is written
  • I2C Speed – GreenPAK I2C is 400 kHz
  • I2C Address – GreenPAK I2C can have up to 16 unique addresses
  • Timing Adjustment and Additional Glue Logic – GreenPAK has integrated LUTs, Inverters, DFFs, Counters

I2C Readable Matrix Inputs

Resource Utilization

GreenPAK can often implement multiple functions in one small device. This isn’t limited to GPIO expansion applications. Just one GreenPAK device can implement glue logic, timing adjustment, reset, power sequencing, LED control, and more depending on design requirements and resource configuration.

All of GreenPAK 5 devices contain the needed I2C block for GPIO expansion and are only limited by the number of pins. Below is a chart of the maximum number of direct inputs or outputs achievable for each member of the family.

GreenPAK Output Expansion Input Expansion
SLG46531V 8 16
SLG46532V 8 15
SLG46533V 8 16

View the full list of the GreenPAK videos in our Training Video Library.