Related Resources

REFERENCE DESIGN
  • AN-1104 I2C Level Shifter
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Level Shift

Bridging Independent Voltage Domains

Full-featured, power efficient systems often contain subsystems with different voltage requirements. For example, a wearable may normally operate at 1.8 V, but when charging, portions of the design will operate at the USB standard 5 V. Similarly, the display may operate at a different voltage than the sensors. Often, a number of discrete passive or fixed-function level shift devices are needed to make these voltage domains work together. With GreenPAK™, getting these different voltage domains working together, efficiently and with the flexibility of programmable mixed-signal, is a snap with any of our Dual Supply part numbers.

GreenPAK is capable of a variety of level shift methods:

  • Uni-directional
  • Bi-directional with Dedicated Ports
  • Bi-directional with External Direction Indicator
  • Bi-directional, Auto-sensing


GreenPAK™ Benefits for Level Shift:

  • Dual Supply
    • Dual Supply GreenPAK enables high efficiency level-shift without the need for external pull-up resistors
    • Dual Supply GreenPAK can support 1.8 V to 5.0 V for VDD and 1.8 V to VDD for VDD2
  • System Stability
    • GreenPAK is zero code – Implementing features in hardware ensures stability
    • GreenPAK can integrate many components ensuring fewer points of failure
  • Power Consumption
    • GreenPAK is low-power – Can operate continuously without ruining power budget
  • Size
    • GreenPAK is as small as 1.2 mm²
  • Flexibility
    • GreenPAK GPIO are configurable – Pull-up/pull-down resistors, Push-Pull, Open drain, etc.
    • GreenPAK GPIO routing is flexible – Ensuring the least complexity in PCB routing
    • GreenPAK integrates many common components – Generating custom timing and logic to further eliminate external components while bridging voltage domains and signal requirements


Uni-directional


The simplest form of level-shift is uni-directional. Shifting a single direction, up or down, is easy in GreenPAK since all GPIO can be configured as inputs or outputs


Key Design Considerations
  • Number of Signals – GreenPAK can support up to 9 inputs/8 outputs on a single voltage domain
  • IO Configuration – Configurable pull-up / pull-down resistors on GreenPAK’s GPIO make communicating with any IC a snap
Example 1. Timing Diagram Example 1. Uni-directional level-shift implemented in GreenPAK


Bi-directional with Dedicated Ports


Similar to uni-directional, using GreenPAK’s configurable GPIO to dedicate specific pins or groups of pins as input or output is easy. Each pin tied to a specific voltage domain can be configured independently allowing information to flow from lower to higher VDD or higher to lower VDD


Key Design Considerations
  • Number of Signals – GreenPAK can support up to 9 inputs/8 outputs on a single voltage domain
  • IO Configuration – Configurable pull-up / pull-down resistors on GreenPAK’s GPIO make communicating with any IC a snap
Example 2. Timing Diagram Example 2. Bi-directional level-shift with dedicated ports implemented in GreenPAK


Bi-directional with External Direction Indicator


With GreenPAK it is also possible to dual-purpose certain GPIO as digital input AND output using the output enable pin to control the direction.


Key Design Considerations
  • Direction Signal Polarity – Using GreenPAK’s integrated LUTs configured as an inverter can accommodate any signal polarity
  • Direction Signal Origin – With GreenPAK, the direction signal input can be from either voltage domain
Example 3. Timing Diagram Example 3. Bi-directional level-shift with external direction signal implemented in GreenPAK


Bi-directional, Auto-sensing


Using GreenPAK’s configurable digital and timing resources, it is even possible to implement an auto-sensing, bi-directional, level-shift solution such as the I2C Level-shift shown in AN-1104.


Key Design Considerations
  • Response Time – GreenPAK is capable of up to 400 kHz standard I2C


Example 4. AN-1104 - I2C Level Shift in SLG46620V Example 4. Auto-sensing bi-directional I2C level-shift


Dual Supply GreenPAK

GreenPAK can often implement multiple functions in one small device. This isn’t limited to level-shift 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.

Below is a list of our Dual Supply GreenPAK devices and the number of GPIO dedicated to each voltage domain.


Part Number VDD IO VDD2 IO
SLG46121V 5 4
SLG46535V 7 4
SLG46538V 9 8
SLG46621V 9 8

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