The system master can reset the PCA9539 in the event of a time-out or other improper operation by asserting a low in the RESET input. The power-on reset puts the registers in their default state and initializes the I2C/SMBus state machine. Asserting RESET causes the same reset/initialization to occur without de-powering the part.
The PCA9539 open-drain interrupt ( INT) output is activated when any input state differs from its corresponding Input Port register state and is used to indicate to the system master that an input state has changed.
INT can be connected to the interrupt input of a microcontroller. By sending an interrupt signal on this line, the remote I/O can inform the microcontroller if there is incoming data on its ports without having to communicate via the I2C bus. Thus, the PCA9539 can remain a simple slave device.
The device outputs (latched) have high-current drive capability for directly driving LEDs. The device has low current consumption.
The PCA9539 is identical to the PCA9555, except for the removal of the internal I/O pullup resistor, which greatly reduces power consumption when the I/Os are held low, replacement of A2 with RESET, and a different address range.
Two hardware pins (A0 and A1) are used to program and vary the fixed I2C address and allow up to four devices to share the same I2C bus or SMBus.
| Top documentation | Type | Title | Format options | Date |
|---|---|---|---|---|
| * | Data sheet | PCA9539 Remote 16-Bit I2C and SMBus Low-Power I/O Expander With Interrupt Output, Reset, and Configuration Registers datasheet (Rev. H) | PDF | HTML | Mar 10, 2021 |
| Application note | Understanding Transient Drive Strength vs. DC Drive Strength in Level-Shifters (Rev. A) | PDF | HTML | Jul 3, 2024 | |
| Application note | I2C Dynamic Addressing | Apr 25, 2019 | ||
| Application note | Choosing the Correct I2C Device for New Designs | PDF | HTML | Sep 7, 2016 | |
| Application note | Understanding the I2C Bus | PDF | HTML | Jun 30, 2015 | |
| Application note | Maximum Clock Frequency of I2C Bus Using Repeaters | May 15, 2015 | ||
| Application note | I2C Bus Pull-Up Resistor Calculation | PDF | HTML | Feb 13, 2015 |
For additional terms or required resources, click any title below to view the detail page where available.
| Package | Pins | CAD symbols, footprints & 3D models |
|---|---|---|
| SSOP (DB) | 24 | Ultra Librarian |
| VQFN (RGE) | 24 | Ultra Librarian |
| TVSOP (DGV) | 24 | Ultra Librarian |
| SSOP (DBQ) | 24 | Ultra Librarian |
| SOIC (DW) | 24 | Ultra Librarian |
| TSSOP (PW) | 24 | Ultra Librarian |
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