PCA9517A - Level-Translating I2C-Bus Repeater | NXP Semiconductors
Teilenummer: PCA9517A ✓ Aktiv| Menge | Stückpreis | Gesamt |
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| 1 | $0 | $0,00 |
| 10 | $0 | $0,00 |
| 100 | $0 | $0,00 |
| 500 | $0 | $0,00 |
| 1.000 | $0 | $0,00 |
PCA9517A Übersicht
A level-translating I2C-bus repeater is an interface IC that sits between two segments of an I2C or SMBus network, allowing devices operating from different supply rails - for example a 1.8 V microcontroller and a 3.3 V or 5 V peripheral - to communicate on the same bus. As a member of the I2C buffer/repeater/extender family within NXP's interface portfolio, it solves both voltage-domain mismatch and bus-capacitance limits in a single surface-mount device.
Key features include voltage-level translation from 0.9 V up to 5.5 V, open-drain I2C-compatible I/O configuration, an active-high repeater-enable (EN) input for bus segmentation and power sequencing, and drivers that stay disabled until both VCC(A) (above 0.8 V) and VCC(B) (above 2.5 V) are present, preventing bus lock-up during power-up. SMBus compatibility extends its use into system-management designs.
Technically, the A-side I/O and logic are powered by VCC(A) while the B-side is powered by VCC(B); the internal driver applies a static offset on the B-side, which means port B must not be connected to another device with rise-time accelerators (such as PCA9510/9511/9512/9513/9514/9515A/9516A or PCA9518). Pull-up resistors on both segments provide the logic-high levels, as with any standard open-drain I2C bus.
Typical applications include interfacing 1.2 V to 1.8 V low-voltage SoCs with 3.3 V or 5 V sensor and EEPROM buses, extending I2C reach in telecom and networking backplanes, and managing multi-rail power supplies in industrial systems.
Designers should keep EN changes limited to bus-idle states to avoid corrupting in-progress transfers, and verify that chained buffer topologies follow the NXP datasheet restrictions.
This page synthesizes verified datasheet facts, cross-brand drop-in options such as TI's TCA9517, and practical design notes not found in the manufacturer datasheet alone.
Drop-in-Alternativen für PCA9517A – gleiches Gehäuse, Pin-kompatibel. Bauteile mit anderem Gehäuse, die eine PCB-Überarbeitung erfordern, sind ausgeschlossen.
Varianten dieser Serie
Modelle derselben Serie, die drop-in-kompatibel sind mit PCA9517A (gleiche Bauform und Footprint) – abweichend in Function, Package, Number of Channels, Powered-Off High Impedance, RoHS Status.
Schnellvergleichstool – Wählen Sie Alternativbauteile für den Direktvergleich:
TCA9517DR
✅ Drop-In✓ Auf Lager
$0.53 / Stück
Datenblatt ansehen →TCA9517DGKR
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$0.65 / Stück
Datenblatt ansehen →TCA9517DGKRQ1
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$0.46 / Stück
Datenblatt ansehen →PCA9517D
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
PCA9517A
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Preis auf Anfrage
Datenblatt ansehen →PCA9517A Technische Daten
| Funktion | Level-translating I2C-bus repeater (2-channel bidirectional buffer) |
| A-Side Supply Voltage (VCC(A)) | 0.9 V (min operating) to 5.5 V |
| B-Side Supply Voltage (VCC(B)) | 2.7 V to 5.5 V |
| Level Translation Range | 0.9 V to 5.5 V (A-side) to 2.7 V to 5.5 V (B-side) |
| Bus Interface | I2C-bus and SMBus compatible |
| Number of Channels | 2 (SDA, SCL) |
| Enable Input | EN, active-high repeater-enable |
| Power-Up Driver Enable Thresholds | Drivers enabled only when VCC(A) > 0.8 V and VCC(B) > 2.5 V |
| I/O Configuration | Open-drain (standard I2C) |
| Process Technology | CMOS |
| Gehäuse | SOIC-8 (SOP) |
| Montageart | Surface Mount |
| Maximum Data Rate | 400 kHz (per PCA9517 family specification) |
| A-Side B Condition | B-side port must not connect to rise-time-accelerator devices (PCA9510-9516A, PCA9518) |
PCA9517A Pin-Konfiguration
| Pin 1 | A1 (SDA_A) — A-side serial data I/O, open-drain, powered from VCC(A) |
| Pin 2 | A0 (SCL_A) — A-side serial clock I/O, open-drain, powered from VCC(A) |
| Pin 3 | GND — Ground reference |
| Pin 4 | EN — Active-high repeater enable input; change state only when bus is idle |
| Pin 5 | VCC(B) — B-side supply, 2.7 V to 5.5 V |
| Pin 6 | B1 (SDA_B) — B-side serial data I/O, open-drain with static offset, powered from VCC(B) |
| Pin 7 | B0 (SCL_B) — B-side serial clock I/O, open-drain with static offset, powered from VCC(B) |
| Pin 8 | VCC(A) — A-side supply, down to 0.9 V (up to 5.5 V) |
Typische Anwendungen
PCA9517A ist geeignet für 6 Anwendungs: Low-Voltage MCU to 3.3 V / 5 V Peripheral Bus, I2C Bus Extension and Capacitance Segmentation, Server and Telecom System Management (SMBus), Industrial Multi-Rail Power Management, Automotive Body and Gateway ECU I2C Domains, Consumer Electronics Display and Touch Buses.
Low-Voltage MCU to 3.3 V / 5 V Peripheral Bus
The PCA9517A is designed specifically to connect low-voltage processors operating at 1.2 V to 1.8 V with legacy 3.3 V or 5 V I2C peripherals such as EEPROMs, RTCs, and sensors. Its 0.9 V minimum A-side supply supports modern deep-submicron SoC I/O rails, while the B-side accepts 2.7 V to 5.5 V. Placed between the MCU's SDA/SCL pins and the higher-voltage bus with appropriate pull-ups on each segment, the repeater actively drives both sides, so the MCU does not see the capacitance or the higher voltage of the peripheral bus. This active drive also restores degraded edge rates over long traces, and the power-up gating (VCC(A) above 0.8 V, VCC(B) above 2.5 V) prevents bus contention while rails are ramping.
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I2C Bus Extension and Capacitance Segmentation
Standard I2C is limited by total bus capacitance (typically 400 pF), which restricts trace length and device count. The PCA9517A overcomes this by isolating the two bus segments with active open-drain drivers: each side sees only its own pull-up network and local load, effectively multiplying the allowable bus length. In telecom shelves, networking backplanes, and industrial chassis where I2C must span tens of centimeters to multiple boards, placing a PCA9517A at the segment boundary restores signal edges and prevents stuck-bus propagation between domains. Because it retains all I2C operating modes including clock stretching and multi-master arbitration, the buffered topology behaves transparently to software. Keep EN toggling to bus-idle periods, and follow the NXP datasheet restrictions when cascading with rise-time-accelerator devices.
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Server and Telecom System Management (SMBus)
In server, storage, and telecom platforms, the SMBus management plane frequently mixes a low-voltage BMC (1.8 V or 3.3 V) with 5 V hot-swap controllers, power-supply supervisors, and DIMM temperature sensors. The PCA9517A is SMBus compatible, so it level-shifts and buffers this management bus while preserving SMBus protocol behavior including timeout-independent operation of the physical layer. The active-high EN pin lets the BMC disconnect a segment during chassis bring-up or fault isolation, improving robustness of multi-rail systems. Because the B-side tolerates 5.5 V, legacy 5 V management components connect without extra translation stages, reducing BOM count. Designers should size SMBus pull-ups per segment (2.2 kOhm to 10 kOhm typical) and respect the rise-time-accelerator chaining restrictions from the NXP datasheet.
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Industrial Multi-Rail Power Management
Industrial control boards commonly carry several supply domains (1.8 V logic, 3.3 V interfaces, 5 V field-side devices), and I2C is the de facto bus for PMBus-style power supervisors and monitoring DACs/ADCs spanning those domains. The PCA9517A bridges these rails directly: its 0.9 V minimum A-side supports the newest controller logic, and the B-side handles 2.7 V to 5.5 V field rails. The built-in driver gating means the repeater never asserts undefined states while a domain is unpowered - for example a card removed from a backplane - because both VCC(A) above 0.8 V and VCC(B) above 2.5 V are required before drivers enable. This makes partial-power operation safer than with passive translation. Combine with hot-swap e-fuses and I2C GPIO expanders for complete rail supervision.
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Automotive Body and Gateway ECU I2C Domains
Automotive gateway and body-control modules often mix a low-voltage safety MCU domain with 3.3 V or 5 V sensor and I/O-expander rails, and must tolerate crank and load-dump rail variation. The TI TCA9517 family - including the AEC-Q100-qualified TCA9517DGKRQ1 - provides the same 0.9 V to 5.5 V translation function with automotive qualification, and is pin- and function-compatible with the NXP PCA9517A in compatible footprints. Using a level-translating repeater rather than a passive switch isolates the heavily loaded body bus (door modules, lighting drivers, sensor clusters) from the MCU's local bus, restoring edges over several meters of harness and preventing a faulted slave from dragging down the master segment. Choose the Q1 variant where AEC-Q100 compliance is mandatory.
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Consumer Electronics Display and Touch Buses
In consumer devices - TVs, monitors, and smart appliances - an EDID/Display Data Channel (DDC) or touch-controller I2C bus frequently runs between a 1.8 V SoC and 3.3 V or 5 V external connectors. The PCA9517A buffers and level-shifts these links so hot-plugged external devices cannot overdrive the SoC's low-voltage I/O, and the active buffering tolerates the cable capacitance of external DDC lines that would violate the raw I2C capacitance limit. The EN pin enables disabling the segment during standby to meet low-power requirements, cutting the repeater drivers completely when the system sleeps. Because the part retains standard I2C open-drain behavior, EDID reads and display handshakes proceed transparently. Place the repeater near the connector with local pull-ups sized for the cable load.
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Zusammenfassung der empfohlenen Produkte
Technische Referenzdaten für PCA9517A – Vergleich, Designhinweise und Compliance-Informationen.
Auswahlhilfe
Vergleich mit Alternativen
| Parameter | Dieses Produkt | TCA9517DR | TCA9517DGKR | PCA9517D | PCA9517A (onsemi) |
|---|---|---|---|---|---|
| Package | SOIC-8 | SOIC-8 - same | VSSOP-8 (2x3 mm) - different body | SOIC-8 - same | SOIC-8 - same |
| Brand | NXP Semiconductors | Texas Instruments | Texas Instruments | NXP Semiconductors | onsemi |
| B-Side Supply Range | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 2.7 V to 5.5 V |
| Enable Pin | Yes, active-high EN | Yes, active-high EN | Yes, active-high EN | Yes, active-high EN | Yes, active-high EN |
| Bus Interface | I2C-bus and SMBus | I2C and SMBus, 400 kHz | I2C and SMBus, 400 kHz | I2C-bus and SMBus | I2C-bus and SMBus |
Wichtigste Unterscheidungsmerkmale
- 0.9 V minimum A-side supply (vs. PCA9517D)
- Power-up driver gating (vs. PCA9517D)
- Multi-source availability (vs. TCA9517DR)
Designhinweise
Never connect the B-side port of the PCA9517A to another device that includes rise time accelerators. Per the NXP datasheet, the static offset design of the port B I/O drivers prevents connection to the PCA9510, PCA9511, PCA9512, PCA9513, PCA9514, PCA9515A, PCA9516A, another PCA9517A port B, or PCA9518. Violating this causes the offset voltages to stack and the bus to latch low. Chaining must follow the permitted topologies in the datasheet application section.
Size separate pull-up resistors for each bus segment rather than sharing one network across the repeater. The A-side pull-up pulls to VCC(A) (as low as 0.9 V) and the B-side pulls to VCC(B) (2.7 V to 5.5 V); typical values range from about 1 kOhm for fast, heavily loaded 5 V segments to 10 kOhm for light 1.8 V segments. Per the datasheet, the PCA9517A has a standard open-drain configuration, so logic-high levels depend entirely on these pull-ups.
Use the EN pin for bus isolation, but only toggle it when the bus is idle - the NXP datasheet explicitly cautions that changing EN state during an active transfer can corrupt data. A practical scheme is to gate EN from a supervisor or GPIO that monitors rail-valid flags, since the device already self-gates drivers until VCC(A) exceeds 0.8 V and VCC(B) exceeds 2.5 V. In multi-card systems, EN also enables hot-swap of the far segment.
Compliance-Informationen
Compliance data was not present in the provided web data; verify RoHS/REACH status on the NXP product page for the specific ordering suffix.
