PCA9508D,118

Signal Buffers, Repeaters, Splitters Overview

The PCA9508D,118 is a CMOS integrated circuit designed as a hot-swappable level translating I2C-bus repeater. It provides bidirectional buffering for data (SDA) and clock (SCL) lines, enabling voltage translation between a low-voltage side (VCC(A): 0.9 V to 5.5 V) and a high-voltage side (VCC(B): 2.7 V to 5.5 V). The device supports Standard-mode and Fast-mode I2C-bus devices up to 400 kHz. It features offset-free hot-swap capability with IDLE/STOP detect circuitry, allowing insertion into live backplanes without bus contention. The SO8 package includes an active HIGH enable pin and open-drain inputs/outputs.

Signal Buffers, Repeaters, Splitters Feature Summary

• Supports zero-offset hot-swap operations using IDLE/STOP detect circuitry to prevent bus corruption during card insertion.
• Provides bidirectional buffering and voltage level translation between adjustable low voltage (down to 0.9 V) and higher voltage (2.7 V to 5.5 V) domains.
• Enables isolation of two bus halves for both voltage and capacitance, supporting up to 400 pF on either side of the device.
• Features lock-up free operation with powered-off high-impedance I/O pins and 5 V tolerant inputs.

Signal Buffers, Repeaters, Splitters Applications

• Connecting I/O cards to live backplanes in server platforms requiring hot-swap capability.
• Translating signals between low-voltage slave devices (e.g., 1.2 V or 1.8 V) and standard 3.3 V or 5 V I2C masters.
• Extending I2C bus length by buffering SDA and SCL lines while maintaining arbitration and clock stretching support.

Signal Buffers, Repeaters, Splitters Procurement Notes

Verify that the specific ordering suffix matches the required package type, as the D suffix denotes the SO8 plastic small outline package. Confirm supply voltage requirements align with the device's dual-supply architecture, ensuring VCC(A) and VCC(B) ranges are within specified limits for the target application environment.

Signal Buffers, Repeaters, Splitters Selection Notes

Select this component when system design requires isolating voltage domains below 2.7 V from standard 3.3 V or 5 V buses without signal degradation. Ensure the application benefits from the zero static offset on the A side, which allows series connection of multiple repeaters. Verify that the B side static offset does not conflict with connected rise time accelerators or other buffers with similar characteristics.

Signal Buffers, Repeaters, Splitters Part Context

The PCA9508 serves as a functional replacement for legacy NXP devices such as the PCA9515, PCA9515A, PCA9517, and PCA9517A. It addresses limitations in previous repeaters by offering adjustable voltage translation down to 0.9 V on port A while maintaining compatibility with SMBus standards. The device is part of the broader interface IC portfolio used for bus expansion and protection in complex digital systems.

Signal Buffers, Repeaters, Splitters Replacement Considerations

The PCA9517A is documented as a high ESD drop-in replacement for the PCA9517. Designers should verify pinout and electrical parameter compatibility before substituting older models. Ensure that any replacement maintains the required hot-swap functionality and voltage translation ranges specified for the original design.

Signal Buffers, Repeaters, Splitters FAQ

Can the PCA9508 be used to translate voltages lower than 2.7 V?

Yes, the A side operating supply voltage range extends down to 0.9 V, allowing translation from very low voltage buses to the 2.7 V to 5.5 V range on the B side.

What happens to the I/O pins if one of the supply voltages is unpowered?

When any supply pin is unpowered, the 5 V tolerant I/O pins enter a high-impedance state, preventing current leakage or bus interference.

Is it possible to connect multiple PCA9508 devices in series?

Yes, multiple PCA9508s can be connected in series (A side to B side) without build-up in offset voltage, though total delay must be considered for maximum bus speed.