TCA9517DR - Level-Shifting I2C Bus Repeater | Texas Instruments
料号： TCA9517DR ✓ 量产中| 数量 | 单价 | 小计 |
|---|---|---|
| 1 | $1.2 | $1.20 |
| 10 | $1.08 | $10.80 |
| 100 | $0.9 | $90.00 |
| 500 | $0.72 | $360.00 |
| 1,000 | $0.53 | $530.00 |
TCA9517DR 概述
An I2C bus buffer (also called a bus repeater or level translator) is an interface IC that sits between two segments of an I2C or SMBus serial bus. Its role in the interface IC hierarchy is to electrically isolate the two segments while translating signal levels between devices powered at different voltages, allowing low-voltage microcontrollers to communicate safely with higher-voltage peripherals. A buffer also isolates bus capacitance, so each side can drive longer traces or more devices than a single unbuffered bus would allow.
Key features include fully bidirectional level translation with no direction-control pin, a low-level input on the A-side set at 0.3 x VCCA that accommodates smaller voltage swings of lower-voltage logic, and a powered-off high-impedance state on all pins so the part never loads the bus when unpowered. According to the TCA9517 datasheet, the A-side drivers operate from 0.9 V to 5.5 V, drive more current than B-side drivers, and do not require a buffered low or static offset voltage, producing a nearly 0 V hard low on the A-side.
Architecturally, the TCA9517 uses open-drain drivers with rise-time support rather than a static 0.5 V low offset on the A-side, distinguishing it from the older PCA9517 generation. The 230 ns maximum propagation delay preserves I2C Fast Mode timing margins at 400 kHz, and the two channels translate both SDA and SCA lines simultaneously.
Typical applications include connecting 1.8 V or 3.3 V MCU I2C ports to 5 V EEPROMs, sensors, and RTCs in industrial and telecom equipment, isolating bus capacitance in long backplane runs, and buffering densely loaded SMBus segments.
Design consideration: keep the A-side connected to the lower-voltage, higher-capacitance segment; the B-side static 0.5 V offset requires pairing buffers B-side to A-side in cascaded topologies.
This page synthesizes distributor pricing, verified drop-in alternatives, pinout, and practical design notes not found in the manufacturer datasheet.
直接替换替代料： TCA9517DR ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
本系列中的变体
可与以下型号直接替换的同系列型号： TCA9517DR （相同外形与封装尺寸） ——差异在于 Function, Package, Number of Channels, Direction Control, MSL Level.
快速对比工具——选择替代料号进行并排对比：
TCA9517DRQ1
✅ 直接替换 ⚠️ 规格未核验📋 参考替代料（不在目录中）
TCA9517AD
✅ 直接替换📋 参考替代料（不在目录中）
TCA9517D
✅ 直接替换📋 参考替代料（不在目录中）
PCA9517D
✅ 直接替换📋 参考替代料（不在目录中）
PCA9600D,118
✅ 直接替换 ⚠️ 规格未核验✓ 有现货
$1.02 / 个
查看数据手册 →TCA9517DR 规格参数
| 功能 | Level-translating I2C/SMBus bus buffer (repeater) |
| Number of Channels | 2 (SDA and SCL) |
| VCCA Supply Range (A-side) | 0.9 V to 5.5 V |
| VCCB Supply Range (B-side) | 3.0 V to 5.5 V |
| Maximum Data Rate | 400 kHz (I2C Fast Mode) |
| Propagation Delay | 230 ns (max) |
| A-side Input Low Level | 0.3 x VCCA |
| Powered-Off High Impedance | Yes, on all pins |
| Direction Control | Not required (fully bidirectional) |
| 封装 | SOIC-8 (D), 3.90 mm width |
| 安装类型 | Surface Mount |
| 工作温度 | -40C to +85C |
| MSL 等级 | MSL 1 (260C unlimited) |
| RoHS 状态 | Compliant (Green, no Sb/Br) |
TCA9517DR 引脚配置
| 引脚 1 | A1 — A-side serial data 1 (connect to low-voltage bus segment) |
| 引脚 2 | A2 — A-side serial clock 2 (connect to low-voltage bus segment) |
| 引脚 3 | GND — Ground reference |
| 引脚 4 | NC — Not connected; leave floating or tie to GND |
| 引脚 5 | B2 — B-side serial clock (connect to higher-voltage bus segment) |
| 引脚 6 | B1 — B-side serial data (connect to higher-voltage bus segment) |
| 引脚 7 | VCCB — B-side supply, 3.0 V to 5.5 V |
| 引脚 8 | VCCA — A-side supply, 0.9 V to 5.5 V |
典型应用
TCA9517DR 适用于 6 应用s: 1.8 V MCU to 5 V Peripheral I2C Translation, Industrial Backplane Bus Capacitance Isolation, Server and Telecom Hot-Plug SMBus, Automotive Body and Infotainment I2C Links, Mixed-Voltage Sensor Aggregation, Cascaded Multi-Rail I2C Trees.
1.8 V MCU to 5 V Peripheral I2C Translation
The TCA9517DR directly bridges a 1.8 V microcontroller I2C port to 5 V EEPROMs, RTCs, and sensors because VCCA supports 0.9 V to 5.5 V and the A-side input-low threshold of 0.3 x VCCA correctly reads narrow 1.8 V logic swings, while the B-side drives a clean full-swing 5 V open-drain bus. Place the MCU segment on A1/A2 with VCCA = 1.8 V and the peripheral segment on B1/B2 with VCCB = 5 V, each side with its own pull-up resistors (typically 2.2 kOhm to 4.7 kOhm). The 230 ns propagation delay leaves ample margin in the 400 kHz Fast Mode clock period, so low-voltage MCUs can drive legacy 5 V peripherals without any discrete transistor level-shifter circuits.
推荐
Industrial Backplane Bus Capacitance Isolation
Industrial backplanes frequently exceed the 400 pF I2C capacitance limit because of long traces, connectors, and many slave devices. The TCA9517DR splits the bus into isolated segments: the A-side actively drives a hard low (nearly 0 V output low per the datasheet), so each segment sees only its own capacitance and pull-up strength rather than the whole network. In a PLC rack, a buffer per card slot isolates each card's loading, letting the SMBus or I2C backbone run reliably at 400 kHz across the full shelf. Its powered-off high-impedance state also means a removed or unpowered card never drags the shared bus down, preserving communication for the remaining cards in the system.
推荐
Server and Telecom Hot-Plug SMBus
In server shelves and telecom line cards, the SMBus management bus stays live while cards are inserted and removed. The TCA9517DR is designed for this: all pins go high-impedance when VCCA or VCCB is removed, so an extracted card cannot corrupt or load the live management bus. The 400 kHz support with 230 ns maximum delay keeps PMBus-style polling within timing budgets, and the hard-low A-side drive tolerates the residual bus loading of connectors and long midplane traces. Placing one TCA9517DR per line card, A-side facing the card electronics and B-side facing the midplane, gives clean hot-plug behavior without extra FET isolation circuits.
推荐
Automotive Body and Infotainment I2C Links
For automotive designs, the pin-compatible TCA9517DRQ1 variant brings the same 0.9 V-to-5.5 V A-side and 3.0 V-to-5.5 V B-side translation to 12 V vehicles, where sensors and displays often run different rails than the low-voltage MCU domain. The -40C to +85C operating range and powered-off high-impedance behavior suit modules that sleep on a switched rail: when the module unpowers, the buffer disconnects from the shared body-domain I2C instead of leaking current or clamping the bus. Using the SOIC-8 footprint across Q1 and standard parts lets one PCB layout serve both automotive and industrial builds, simplifying platform reuse in mixed product families.
推荐
Mixed-Voltage Sensor Aggregation
Sensor nodes commonly mix 3.3 V digital sensors with 1.8 V logic or 5 V analog front-end domains. The TCA9517DR serves as the single translation point between a 3.3 V sensor segment and a 1.8 V MCU segment: with VCCA = 1.8 V on the A-side and VCCB = 3.3 V on the B-side, both domains see full-margin signal levels. Because the buffer actively drives its outputs rather than passing the weak pull-up low through a FET, RC delay from long sensor cables does not distort the 400 kHz waveform on the far side. Two channels translate SDA and SCL simultaneously with matched 230 ns delays, keeping the pair symmetrical for repeated-start I2C sequences.
推荐
Cascaded Multi-Rail I2C Trees
Systems spanning three voltage domains (for example 1.8 V, 3.3 V, and 5 V) can chain TCA9517 buffers, connecting each device B-side to A-side as the TI datasheet topology recommends. The TCA9517's A-side hard low (nearly 0 V, no static offset required) is the enabler: unlike older PCA9517-style parts, the relayed low does not accumulate offset through the chain, so a low level from a 5 V device arrives at a 1.8 V MCU as a valid low. A 1.8 V domain to 3.3 V domain to 5 V domain cascade thus works with the same SOIC-8 part at each stage, keeping BOM consolidation simple while each segment keeps its own capacitance isolation and pull-ups.
推荐
推荐产品汇总
工程参考数据： TCA9517DR ——对比、设计指导和合规信息。
选型指南
与替代料对比
| 参数 | 本产品 | TCA9517DRQ1 | TCA9517AD | PCA9517D | PCA9600D |
|---|---|---|---|---|---|
| Package | SOIC-8 (D), 3.90 mm | SOIC-8 (D) - same | SOIC-8 (D) - same | SOIC-8 (D) - same | SOIC-8 (D) - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | NXP Semiconductors | NXP Semiconductors |
| B-side Supply (VCCB) | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 3.0 V to 5.5 V | 3.0 V to 5.5 V |
| Powered-Off High Impedance | Yes | Yes | Yes | Yes | Yes |
关键差异点
- A-side hard low with no static offset voltage （对比 PCA9517D)
- Pin-compatible automotive variant available （对比 TCA9517DRQ1)
- Powered-off high impedance on all pins （对比 PCA9600D)
设计说明
Decouple VCCA (pin 8) and VCCB (pin 7) each with a 0.1 uF ceramic capacitor placed within 3 mm of the pin, per the TCA9517 datasheet typical application. Keep the SOIC-8 breakout short so A-side and B-side traces do not cross-couple; route SDA/SCL pairs on each side together. Remember the buffer does not replace pull-up resistors - provide separate pull-ups (1 kOhm to 4.7 kOhm typical) on each segment to that segment's own supply, sized so the combined sink current stays within device drive limits.
Two cascading rules prevent field failures. First, connect buffers B-side to A-side, never B-side to B-side, because the B-side low has a static offset that accumulates and violates the receiving threshold; the TCA9517 A-side hard low relays cleanly. Second, the A-side must always be the lower-voltage (or equal) segment - VCCA can be 0.9 V to 5.5 V but VCCB must be 3.0 V to 5.5 V, so a design needing 5 V-to-1.8 V only must orient the part with the 5 V side on B. Verify all four threshold points in system bring-up.
At 400 kHz the 230 ns maximum propagation delay consumes only about 9% of the 2.5 us clock period, leaving timing margin for cascaded buffers, but each additional buffer in a chain adds delay to the SDA turnaround time. Estimate: a three-buffer cascade adds roughly 690 ns worst case, which must be subtracted from the I2C bus-free time (tBUF) budget when checking Fast Mode compliance on an oscilloscope during bring-up. If margins are tight, reduce the segment capacitance or drop the slowest segment to 100 kHz Standard Mode.
合规信息
PartGenie lists the TCA9517DR as Green (RoHS compliant, no Sb/Br) with MSL Level-1-260C-UNLIM. REACH and conflict-minerals status not stated in provided data.
