PCA9509DP,118 - I2C/SMBus Level Translating Repeater | NXP
MPN: PCA9509DP118 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0 | $0.00 |
| 10 | $0 | $0.00 |
| 100 | $0 | $0.00 |
| 500 | $0 | $0.00 |
| 1,000 | $0 | $0.00 |
PCA9509DP118 Overview
A level translating I2C buffer (also called an I2C repeater, bus buffer, or redriver) sits between two segments of an I2C or SMBus network. Its role in the signal-chain hierarchy is: bus buffer -> interface IC -> 2-wire serial interconnect. By isolating the two bus segments, it breaks the total bus capacitance into two independent segments, allowing longer trace lengths and more devices per bus than the raw I2C capacitance limit would otherwise permit, while simultaneously shifting logic levels between a lower core voltage domain and a higher peripheral voltage domain.
Key features include bidirectional buffering of both SDA and SCL, dual supply pins supporting different voltage domains on each side, and support of the 400 kHz Fast-mode I2C timing class per DigiKey's product listing. Because the device actively drives both segments, rise and fall times are restored on each side, improving signal integrity in capacitive, fan-out-heavy systems.
Technically, the repeater uses a rising-edge detector and output driver scheme on each channel so that a LOW on either segment is propagated as a LOW on the other, while allowing either side to pull LOW independently, preserving the wired-AND arbitration and clock-stretching behavior required by the I2C protocol. This makes it transparent to masters and slaves without software configuration.
Typical applications include processor low-voltage I2C ports interfacing with standard 3.3V or 5V SMBus peripherals, telecom and server management buses (PMBus/SMBus), and extension of I2C reach in industrial control backplanes. The 8-TSSOP footprint suits dense board layouts where many bus segments must be buffered.
Design consideration: keep pull-up resistor values on each segment sized independently for that segment's capacitance and supply, and respect supply sequencing guidance from the manufacturer datasheet for the VCC1/VCC2 domains.
This page synthesizes distributor listings, pricing context, and sourcing information for the PCA9509DP,118 in one place, beyond the raw manufacturer datasheet content.
Drop-in alternatives for PCA9509DP118 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
PCA9509PDP,118
✅ Drop-In📋 Reference alternative (not in catalog)
TCA9509DGKR
✅ Drop-In📋 Reference alternative (not in catalog)
PCA9509DP118 Specifications
| Function | Level translating I2C-bus/SMBus repeater |
| Channels | 2 (SDA and SCL) |
| Maximum Clock Frequency | 400 kHz |
| Supply Type | Dual supply (VCC1 / VCC2) |
| Protocol Support | I2C-bus, SMBus |
| Output Drive | Bidirectional buffer, push-pull driver per segment |
| Package | 8-TSSOP |
| Mounting Type | Surface Mount |
| RoHS Status | RoHS compliant (per distributor listing) |
| Category | Interface - Signal Buffers, Repeaters |
PCA9509DP118 8-tssop Pin Configuration Guide
Pin configuration for PCA9509DP118 (8-tssop package). Pin numbering, functions, and connection diagrams are defined in the manufacturer datasheet. Refer to it for the exact footprint and soldering guidelines.
No detailed pinout data available for PCA9509DP118.
Refer to the datasheet for full pin configuration.
Typical Applications
PCA9509DP118 is suitable for 6 applications: Processor Low-Voltage I2C to Standard I2C/SMBus Interface, Server and Telecom Backplane SMBus Management, I2C Bus Extension in Industrial Control, Mixed-Voltage Sensor Aggregation, LED Display and Backlight Controller Buses, Test and Measurement Instrument Internal Buses.
Processor Low-Voltage I2C to Standard I2C/SMBus Interface
The primary application for the PCA9509DP,118 is connecting a processor or FPGA bank running at a reduced core I/O voltage to standard-voltage I2C-bus or SMBus peripherals. The dual-supply architecture (VCC1 on the processor side, VCC2 on the peripheral side) lets each domain reference its own rail while the repeater actively drives both segments. Because the device buffers SDA and SCL at up to 400 kHz, a 1.8V or 2.5V management controller can safely talk to 3.3V or 5V EEPROMs, RTCs, and sensor hubs without risk of overdriving the low-voltage port. Designers should size pull-ups per segment and confirm rise times meet Fast-mode limits on the loaded side.
Recommended
Server and Telecom Backplane SMBus Management
Server, storage, and telecom shelves use SMBus/PMBus networks to monitor power supplies, hot-swap controllers, and fan trays across long backplanes where distributed capacitance quickly exceeds the raw I2C limit. The PCA9509DP,118 segments the bus: its push-pull drivers restore edge rates on each side, so each segment only carries its own capacitance, enabling more device drops and longer traces. The 400 kHz support accommodates PMBus fast-mode traffic, while SMBus protocol compatibility is confirmed by the NXP product description. Place one repeater per shelf segment and keep total segment capacitance within Fast-mode rise-time budgets for deterministic arbitration.
Recommended
I2C Bus Extension in Industrial Control
Industrial control panels and PLC I/O racks often need I2C runs longer than the protocol's capacitance budget allows. The PCA9509DP,118 extends the bus by providing bidirectional buffering of SDA and SCL: a LOW on either segment is driven out on the other, but the segments remain electrically independent, so cable and connector capacitance is no longer cumulative. This lets engineers add remote sensor clusters or display modules on shielded cable without protocol violations. Because arbitration and clock stretching are preserved transparently, existing multi-master firmware needs no changes. Keep segment rise times within specification by tuning pull-up values to each segment's capacitance.
Recommended
Mixed-Voltage Sensor Aggregation
Modern sensor clusters mix 1.8V digital sensors with 3.3V or 5V system logic. The PCA9509DP,118 sits between the low-voltage sensor bus and the higher-voltage controller bus, translating levels while buffering both directions. Its active drive refreshes signal edges degraded by long sensor-side traces and multiple device inputs, an advantage over passive FET translators that share one capacitance budget. At up to 400 kHz, fast-mode sensor data (accelerometers, pressure sensors, environmental ICs) transfers with margin. Verify each sensor's minimum pull-down current against the repeater's drive so LOW levels remain valid on both segments during arbitration.
Recommended
LED Display and Backlight Controller Buses
LED matrix and backlight controller ICs frequently reside on a shared I2C bus at a different supply domain than the host SoC. The PCA9509DP,118 lets a low-voltage SoC manage standard-voltage LED driver chains safely, and the buffering function divides the bus so each driver cluster sits on its own capacitance segment. This is valuable in signage and display panels where trace length and device count per bus are high. The 400 kHz Fast-mode support shortens frame-update times for multiplexed LED drivers compared to 100 kHz standard-mode buses, improving perceived refresh rates. Keep stub lengths short and decouple VCC2 locally at the repeater.
Recommended
Test and Measurement Instrument Internal Buses
Bench instruments and data-acquisition modules route I2C between a front-end analog board and a rear digital controller across board-to-board connectors, accumulating capacitance at every interface. The PCA9509DP,118 buffers the bus at the connector boundary so each board segment is capacitively isolated, restoring edge rates and allowing 400 kHz traffic across stacked assemblies. Its dual-supply translation also accommodates analog boards referencing a different rail than the digital controller. Place the repeater close to the connector, decouple both supplies with 100 nF ceramics, and validate arbitration timing at maximum load for multi-master diagnostics firmware.
Recommended
Recommended Products Summary
Engineering reference data for PCA9509DP118 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PCA9509PDP,118 | TCA9509DGKR |
|---|---|---|---|
| Package | 8-TSSOP | TSSOP-8 - same footprint | 8-TSSOP footprint claimed; TI ships TCA9509 in VSSOP-style - verify before layout |
| Brand | NXP Semiconductors | NXP Semiconductors | Texas Instruments |
| Function | Level translating I2C/SMBus repeater | Same repeater function with enable variant | Level translating I2C/SMBus repeater (equivalent function) |
| Channels | 2 (SDA, SCL) | 2 (SDA, SCL) | 2 (SDA, SCL) |
| Supply Architecture | Dual supply (VCC1/VCC2) | Dual supply | Dual supply |
| Protocol Support | I2C-bus, SMBus | I2C-bus, SMBus | I2C-bus, SMBus |
Key Differentiators
- Active bidirectional buffering segments the bus capacitance (vs NVT2002DP,118)
- Enable-pin variant available in the same footprint (vs PCA9509PDP,118)
- 8-TSSOP package in an NXP-native footprint (vs TCA9509DGKR)
Design Notes
Place the PCA9509 close to the bus connector or the boundary between the two voltage domains, with 100 nF ceramic decoupling capacitors at both VCC1 and VCC2 pins, returned to a solid ground plane. Size pull-up resistors independently on each segment: the segment carrying more capacitance needs a stronger (lower-value) pull-up to meet Fast-mode rise-time requirements at 400 kHz, while the lighter segment can use higher values to reduce static current. Estimated: with 200 pF segment capacitance, a 1 kOhm pull-up gives an RC rise time of roughly 200 ns, within Fast-mode 300 ns limits.
The PCA9509 is a dual-supply device; respect the VCC1/VCC2 sequencing and ramp-rate guidance in the NXP datasheet to avoid back-powering either domain through internal ESD structures during startup. If one rail can be absent while the other is live (e.g., peripheral rail controlled by a hot-swap switch), verify the datasheet's behavior under single-supply conditions, or add a local load switch to sequence the repeater's supplies together with its domain.
The repeater's rising-edge detector can re-trigger on slow edges: if a segment is heavily loaded and the pull-up is too weak, the driver may disable repeatedly and stretch the edge, appearing as bus errors or arbitration losses at 400 kHz. Keep each segment's RC rise time within the I2C Fast-mode specification, and avoid star topologies on either segment - I2C segments should remain wired as a single line. When substituting the enable-pin variant (PCA9509P), re-verify the pin map since the EN function changes pin assignment within the same TSSOP-8 footprint.
Compliance Information
RoHS compliance indicated by distributor listing (pcbelectronics and Newark listings flag RoHS). Other compliance attributes not stated in provided data.
