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This 8-bit I/O expander for the two-line bidirectional bus (I2C) is designed for 2.3-V to 5.5-V VCC operation. The device provides general-purpose remote I/O expansion for most microcontroller families via the I2C interface [serial clock (SCL) and serial data (SDA)].
The PCA9557 consists of one 8-bit configuration (input or output selection), input port, output port, and polarity inversion (active-high) registers. At power on, the I/Os are configured as inputs. However, the system master can enable the I/Os as either inputs or outputs by writing to the I/O configuration bits. The data for each input or output is kept in the corresponding input or output register. The polarity of the input port register can be inverted with the polarity inversion register. All registers can be read by the system master.
The device outputs (latched) have high-current drive capability for directly driving LEDs. The device has low current consumption.
The system master can reset the PCA9557 in the event of a timeout or other improper operation by asserting a low in the active-low reset (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 depowering the part.
Three hardware pins (A0, A1, and A2) are used to program and vary the fixed I2C address, allowing up to eight devices to share the same I2C bus or SMBus.
| Type | Title | Date | ||
|---|---|---|---|---|
| * | Data sheet | PCA9557 Remote 8-Bit I2C and SMBus Low-Power I/O Expander datasheet (Rev. J) | 12 Jun 2014 | |
| Application note | Understanding Transient Drive Strength vs. DC Drive Strength in Level-Shifters (Rev. A) | PDF | HTML | 03 Jul 2024 | |
| Application note | I2C Dynamic Addressing | 25 Apr 2019 | ||
| Selection guide | Logic Guide (Rev. AB) | 12 Jun 2017 | ||
| Application note | Choosing the Correct I2C Device for New Designs | PDF | HTML | 07 Sep 2016 | |
| Application note | Understanding and Interpreting Standard-Logic Data Sheets (Rev. C) | 02 Dec 2015 | ||
| Application note | Understanding the I2C Bus | PDF | HTML | 30 Jun 2015 | |
| Application note | Maximum Clock Frequency of I2C Bus Using Repeaters | 15 May 2015 | ||
| Application note | I2C Bus Pull-Up Resistor Calculation | PDF | HTML | 13 Feb 2015 | |
| Application note | Programming Fun Lights With TI's TCA6507 | 30 Nov 2007 | ||
| Application note | Semiconductor Packing Material Electrostatic Discharge (ESD) Protection | 08 Jul 2004 |
For additional terms or required resources, click any title below to view the detail page where available.
| Package | Pins | CAD symbols, footprints & 3D models |
|---|---|---|
| SOIC (D) | 16 | Ultra Librarian |
| SSOP (DB) | 16 | Ultra Librarian |
| TSSOP (PW) | 16 | Ultra Librarian |
| TVSOP (DGV) | 16 | Ultra Librarian |
| VQFN (RGV) | 16 | Ultra Librarian |
| VQFN (RGY) | 16 | Ultra Librarian |
Recommended products may have parameters, evaluation modules or reference designs related to this TI product.
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