PCA9509GM,125 - I2C/SMBus Level Translating Repeater | NXP
Teilenummer: PCA9509GM,125 ✓ Aktiv| Menge | Stückpreis | Gesamt |
|---|---|---|
| 1 | $1.29 | $1,29 |
| 10 | $1.16 | $11,60 |
| 100 | $1.02 | $102,00 |
| 500 | $0.89 | $445,00 |
| 1.000 | $0.78 | $780,00 |
PCA9509GM,125 Übersicht
An I2C repeater (also called a bus buffer or bus extender) is an interface IC that regenerates the bidirectional SDA and SCL signals of a two-wire serial bus. In the system hierarchy, it sits between the processor I2C controller and the peripheral bus, separating bus capacitance into two isolated segments so more devices and longer traces can be driven than the 400 pF bus limit of a directly connected I2C bus allows.
Key features include bidirectional level translation between a low-voltage processor bus (VCCA, for example 1.65 V to 3.6 V per the dual-supply architecture with a 5 V maximum supply rating) and a standard I2C-bus or SMBus at VCCB, 400 kHz fast-mode operation, and a tiny 1.6 x 1.6 mm XQFN-8 footprint with 0.5 mm height for space-constrained boards.
The PCA9509 retains all operating modes and features of the I2C-bus system while shifting levels. It provides bidirectional buffering for both the data (SDA) and clock (SCL) lines, and the buffer function permits extension of the I2C bus by isolating the distributed capacitance on each side. The two channels (SDA and SCL) switch automatically with open-drain, direction-detecting buffer cells, so no direction-control signal is required from the host.
Typical applications include level-shifting between 1.8 V or 2.5 V microcontroller I2C ports and 3.3 V or 5 V peripheral buses in embedded systems, isolating heavily loaded SMBus segments in servers and networking equipment, and extending I2C reach in industrial control and consumer electronics designs.
When designing with the PCA9509, ensure that VCCA is the lower of the two supplies and observe pull-up resistor sizing on both bus segments, since the repeater inserts one buffer delay per transition that marginally affects rise/fall timing at 400 kHz.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in-Alternativen für PCA9509GM,125 – gleiches Gehäuse, Pin-kompatibel. Bauteile mit anderem Gehäuse, die eine PCB-Überarbeitung erfordern, sind ausgeschlossen.
Schnellvergleichstool – Wählen Sie Alternativbauteile für den Direktvergleich:
PCA9509PGM
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
PCA9509GM
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
TCA9509RVHR
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
PCA9509GM,125 Technische Daten
| Funktion | Level translating I2C-bus/SMBus repeater (buffer/ReDriver) |
| Number of Channels | 2 (SDA and SCL) |
| Maximum Bus Frequency | 400 kHz (I2C fast mode) |
| Versorgungsspannung | 5 V max (dual supply VCCA/VCCB) |
| Supply Architecture | Dual supply level translation |
| Protocol Support | I2C-bus and SMBus |
| Signal Direction Control | Automatic (bidirectional open-drain buffers) |
| Betriebstemperatur | -40C to +85C |
| Gehäuse | XQFN-8 (SOT902-1, 1.6 x 1.6 mm, 0.50 mm height) |
| Anzahl der Pins | 8 |
| Montageart | Surface Mount |
| Package Standard | MO-255 |
| Bus Extension | Bidirectional buffering of SDA and SCL lines |
| RoHS-Status | Compliant ("125" suffix = SnAgCu lead-free plating) |
| Packaging | Tape and Reel |
PCA9509GM,125 Pin-Konfiguration
| Pin 1 | A0 — A-side serial data (SDA) referenced to VCCA |
| Pin 2 | A1 — A-side serial clock (SCL) referenced to VCCA |
| Pin 3 | GND — Ground |
| Pin 4 | EN — Enable input (active high); LOW places outputs in 3-state |
| Pin 5 | B1 — B-side serial clock (SCL) referenced to VCCB |
| Pin 6 | B0 — B-side serial data (SDA) referenced to VCCB |
| Pin 7 | VCCB — B-side supply (standard bus voltage domain) |
| Pin 8 | VCCA — A-side supply (processor low-voltage domain) |
Typische Anwendungen
PCA9509GM,125 ist geeignet für 6 Anwendungs: Processor I2C Level Translation (1.8 V/2.5 V to 3.3 V/5 V), I2C Bus Extension and Capacitance Isolation, SMBus Server and Networking Backplanes, Industrial Control and PLC Modules, Battery-Powered and Wearable Consumer Devices, Test and Measurement Instrumentation.
Processor I2C Level Translation (1.8 V/2.5 V to 3.3 V/5 V)
The PCA9509GM,125 fits low-voltage processor buses that must drive standard I2C or SMBus peripherals. Its dual-supply architecture places VCCA on the processor side and VCCB on the peripheral side, translating between a low-voltage 2-wire serial bus and a standard bus at up to 400 kHz. Because it retains all I2C operating modes during the level shift, timing behavior is transparent to the controller. Use 10 kohm pull-ups on the low-voltage A-side and 2.2-4.7 kohm on the higher-voltage B-side; the buffer isolates each segment's capacitance, so total loading can exceed what the processor pins could drive directly. Verify the exact VCCA/VCCB combination against the NXP datasheet electrical characteristics for your rails.
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I2C Bus Extension and Capacitance Isolation
The PCA9509GM,125 extends I2C reach by providing bidirectional buffering for both SDA and SCL, splitting one large bus into two isolated capacitance segments. In systems where sensors, EEPROMs, or port expanders are spread across long flex cables or multiple boards, direct drive violates the bus capacitance limit and causes failed acknowledgements; inserting the repeater regenerates drive strength on each side. At 400 kHz operation, account for the one-buffer-delay per transition in rise/fall timing budgets. Place the repeater at the segment boundary closest to the heavily loaded side, and decouple both VCCA and VCCB with 100 nF ceramics placed within 2 mm of the XQFN-8 pads.
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SMBus Server and Networking Backplanes
In servers, switches, and networking blades, the SMBus manages power supplies, hot-swap controllers, and fan telemetry across multi-slot backplanes. The PCA9509GM,125 buffers the shared SMBus between a baseboard management controller running at low voltage and 3.3 V or 5 V slot devices, isolating the large per-slot capacitance and preventing a faulted segment from pulling down the managed bus. Its -40C to +85C operating range suits forced-air server environments, and the 1.6 x 1.6 mm XQFN-8 fits dense management PCBs. Design each isolated segment with SMBus-compliant pull-ups and verify the buffer delay against the SMBus clock-stretching allowances in your system timing budget.
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Industrial Control and PLC Modules
Industrial controllers routinely combine a 1.8 V or 2.5 V MCU I2C port with 3.3 V and 5 V field-side devices such as ADCs, DACs, and EEPROMs. The PCA9509GM,125 bridges these domains while its active buffering tolerates the heavier bus loading typical of DIN-rail modules with long inter-board harnesses. The -40C to +85C temperature rating covers most industrial enclosures, and the MO-255 XQFN-8 package withstands standard SMT reflow profiles. For maximum reliability in noisy environments, add 100 nF plus 1 uF decoupling on each supply and route SDA/SCL on the B-side away from switching-node traces; the repeater also electrically decouples field-side noise from the processor bus.
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Battery-Powered and Wearable Consumer Devices
Wearables and compact consumer devices need to connect a low-voltage application processor or sensor-hub I2C bus to standard-voltage peripherals while conserving board area. The PCA9509GM,125 addresses this with an ultra-small 1.6 x 1.6 mm, 0.5 mm-height XQFN-8 package suitable for very thin stacked PCBs, while supporting 400 kHz fast-mode traffic for sensors and touch controllers. The automatic bidirectional buffering removes the need for a direction-control GPIO, simplifying firmware. Because quiescent budget matters in battery products, confirm supply current figures in the NXP datasheet and, if bus idle power dominates, evaluate gating the repeater via a load switch on VCCB during sleep states.
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Test and Measurement Instrumentation
Bench instruments and modular measurement systems frequently use I2C for front-panel, calibration-memory, and module-identification buses, mixing low-voltage digital controllers with standard-voltage EEPROMs and DACs on the same two-wire bus. The PCA9509GM,125 provides the level shift and buffering between the controller domain and the instrument backplane at 400 kHz, isolating connector and cable capacitance that varies as modules are inserted. Its dual-supply design means one repeater handles mixed-rail modules without family-specific variants. When laying out the instrument backplane, place the repeater near the backplane connector and keep the A-side traces short and local to the controller for clean edges at fast-mode speeds.
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Zusammenfassung der empfohlenen Produkte
Technische Referenzdaten für PCA9509GM,125 – Vergleich, Designhinweise und Compliance-Informationen.
Auswahlhilfe
Vergleich mit Alternativen
| Parameter | Dieses Produkt | PCA9509PGM | PCA9509GM | TCA9509RVHR |
|---|---|---|---|---|
| Package | XQFN-8 (SOT902-1, 1.6 x 1.6 mm) | XQFN-8 (SOT902-1) - same | XQFN-8 (SOT902-1) - same | VQFN-8 (RHR) - different footprint |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | Texas Instruments |
| Function | Level translating I2C/SMBus repeater | Level translating I2C/SMBus repeater | Level translating I2C/SMBus repeater | Level translating I2C/SMBus repeater |
| Channels | 2 (SDA + SCL) | 2 (SDA + SCL) | 2 (SDA + SCL) | 2 (SDA + SCL) |
| Max Bus Frequency | 400 kHz | 400 kHz | 400 kHz | 400 kHz |
Wichtigste Unterscheidungsmerkmale
- Verified drop-in same-family substitution (vs. PCA9509PGM)
- Active bidirectional buffering vs passive translation (vs. PCA9306DCTR)
- Space efficiency (vs. TCA9509RVHR)
Designhinweise
The SOT902-1 XQFN-8 is a 1.6 x 1.6 mm leadless package with a perimeter pad arrangement; place 100 nF ceramic decoupling capacitors within 2 mm of both VCCA and VCCB pins, each with its own via to the ground plane. Follow the NXP-recommended XQFN land pattern exactly, as oversized pads on leadless packages cause solder bridging between the 0.5 mm-pitch perimeter pads. The tiny footprint also demands careful pin 1 marking checks on incoming tape reels during incoming inspection.
Size pull-up resistors independently on the A-side (VCCA domain) and B-side (VCCB domain). The repeater inserts one buffer propagation delay per transition, which consumes timing margin at 400 kHz fast mode; keep each segment's RC rise time within the I2C fast-mode rise-time specification for the total capacitance of that segment. Typical starting points are 10 kohm on a lightly loaded low-voltage side and 2.2-4.7 kohm on a heavily loaded 3.3 V or 5 V side. Validate with an oscilloscope across the full temperature range of your system.
Do not exceed the 5 V maximum supply rating on either VCCA or VCCB. Remember that bus extension only works if each segment has its own pull-ups - the buffer passes current, not passive pull-up. When substituting parts, note that the functionally equivalent TI TCA9509 in the RVHR VQFN-8 package does not share the SOT902-1 land pattern, so a datasheet pinout cross-check is mandatory before any cross-brand substitution to avoid swapping the VCCB and B-side pins.
Compliance-Informationen
The ",125" NXP ordering suffix denotes lead-free SnAgCu plating; part is listed in NXP environmental quality data. Full REACH and conflict-minerals declarations should be obtained from the NXP environmental compliance portal.
