PCA9545APW - 4-Channel I2C Switch with Interrupt | NXP
MPN: PCA9545APW ✓ Hoạt độngPCA9545APW Tóm tắt
An I2C bus switch (also called an I2C multiplexer or bus router) is a level-transparent pass gate that expands one physical I2C bus into several independent downstream buses. Within the component hierarchy it sits below the system bus controller, above the individual I2C target devices, and belongs to the wider family of interface ICs that manage serial bus arbitration, addressing and clock and data distribution.
Key features of the PCA9545A include four independent downstream channel pairs (SC0/SD0 through SC3/SD3), four interrupt inputs INT0 to INT3 with one input per downstream pair, an active-LOW RESET input, and an internal power-on reset function. Any individual channel, or any combination of channels, may be selected. Channel selection and the interrupt and reset behaviour are controlled entirely from the upstream side of the bus.
Architecturally the device uses bidirectional translating pass gates between the upstream bus and each downstream channel, so data can flow in either direction on SCL and SDA without level shifting of the logic thresholds themselves. The interrupt inputs allow a host microcontroller to be notified when a downstream target pulls its data line LOW, and the active-LOW reset input lets the system recover a downstream bus that has been held LOW by a stalled or disconnected target.
Typical applications include sensor node fan-out where several identical I2C sensors share one host port, interrupt-driven industrial acquisition systems, battery management systems with per-cell current monitors, server and storage module EEPROM sharing, wearable medical monitoring accessories, and multi-channel programmable LED driver control.
When laying out the board, remember that each downstream channel is a separate bus segment and therefore needs its own pull-up resistor pair; do not assume the upstream pull-ups will serve all four channels. Tie RESET to a defined level with a pull-up or a host GPIO, and keep the unused channels tied to a defined state so that a floating downstream segment cannot be pulled into an unexpected state during power-up.
This page consolidates the NXP product documentation, distributor listings, cross-reference candidates, application patterns and practical layout guidance for the PCA9545APW into a single engineering reference.
Bộ thay thế dễ dàng lắp đặt cho PCA9545APW — cùng gói, chân-to-chân tương thích. Các bộ phận yêu cầu hàn PCB bị loại trừ.
PCA9545BPW
✅ Drop-In ⚠️ Thông số chưa được xác minh📋 Tham chiếu thay thế (không có trong danh mục)
PCA9545CPW
✅ Drop-In ⚠️ Thông số chưa được xác minh📋 Tham chiếu thay thế (không có trong danh mục)
PCA9545APW
✅ Drop-InLiên hệ để biết giá
Xem tài liệu →TCA9545APW
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
PCA9545APWR
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
PCA9545APW Tỷ lệ tối đa & tính chất điện
| Device Type | 4-channel I2C-bus switch with interrupt logic and reset |
| Number of Downstream Channels | 4 |
| Upstream Bus | 1 x SCL/SDA pair |
| Downstream Buses | 4 x SCL/SDA pairs (SC0/SD0 to SC3/SD3) |
| Interrupt Inputs | 4 (INT0 to INT3) |
| Reset Input | Active-LOW RESET with internal power-on reset |
| Channel Selection | Programmable via control register contents |
| Bidirectional Signal Passing | Bidirectional translation on SCL and SDA |
| Hộp | 20-pin TSSOP (PW) |
| Kiểu lắp đặt | Surface mount |
| Datasheet Document | PCA9545A/45B/45C data sheet (28 pages) |
| Trạng thái vòng đời | Active |
Hướng dẫn cấu hình chân PCA9545APW 20-pin tssop (pw)
Cấu hình chân cho PCA9545APW (20-pin tssop (pw) gói). Số thứ tự chân, chức năng và sơ đồ kết nối được xác định trong tài liệu thông số kỹ thuật của nhà sản xuất. Tham khảo nó để biết footprint và hướng dẫn hàn chính xác.
Không có dữ liệu chân cụ thể sẵn có cho PCA9545APW.
Tham khảo: tài liệu kỹ thuật cho cấu hình chân đầy đủ.
Ứng dụng tiêu biểu
PCA9545APW phù hợp cho 6 Áp dụngs: Multi-Sensor I2C Fan-Out in IoT Nodes, Interrupt-Driven Industrial Data Acquisition, Battery Management System Cell Monitoring, Server and Storage Module EEPROM Sharing, Wearable Medical Monitoring Accessories, Programmable Multi-Channel LED Driver Control.
Multi-Sensor I2C Fan-Out in IoT Nodes
The PCA9545APW fits IoT sensor nodes where several identical I2C sensors would otherwise collide on one address range. A single upstream SCL/SDA pair from the host microcontroller fans out to four downstream pairs, and each downstream segment can be enabled or deselected independently through the programmable control register, so only the selected sensor bank is powered and addressed during a conversion cycle. Because every downstream pair is a separate bus segment, each one needs its own pull-up resistors sized for the sensors on that segment. The advantage over a plain four-in-one sensor hub is the ability to isolate a misbehaving or noisy downstream sensor, and to hold unused channels deselected during power-up to avoid false interrupts.
Được đề xuất
Interrupt-Driven Industrial Data Acquisition
In industrial acquisition systems, many slow industrial sensors only speak when a measurement is ready, and polling them wastes bus time and CPU cycles. The PCA9545APW provides one interrupt input per downstream pair, INT0 through INT3, so a downstream device pulling SDA LOW can raise a dedicated interrupt line and the host controller knows exactly which sensor group requires attention. The active-LOW RESET input adds a recovery path: if one downstream bus is stuck LOW, the host can de-assert the whole mux and reinitialise the bus state machine instead of power-cycling the cabinet. With four independently selectable channels, a single I2C port can serve pressure, temperature and flow sensor groups while keeping each bus segment physically short and isolated from noise sources.
Được đề xuất
Battery Management System Cell Monitoring
Battery packs in electric vehicles and energy storage systems stack many identical monitor ICs on one bus, and each monitor exposes interrupt-style alert lines. The PCA9545APW lets four downstream cell-monitor groups share a single upstream connection to the pack controller, with one interrupt input per group so a faulted cell can be located without scanning the whole bus. Channel selection is software-controlled through the control register, which allows the controller to poll groups sequentially and keep bus loading low during long strings. The active-LOW reset is valuable here because a monitor that fails mid-discharge can hold the bus LOW; resetting the mux restores a known state on all four segments and lets the pack controller re-establish communication without shutting down the pack.
Được đề xuất
Server and Storage Module EEPROM Sharing
Server motherboards and storage backplanes often need to expose several identical EEPROMs or management controllers to one baseboard management controller. The PCA9545APW splits a single SMBus/I2C host port into four downstream segments, each with its own interrupt line so the manager is notified when a module EEPROM signals a change such as a firmware update request. Independent channel gating means a module that has failed mid-transaction can be isolated by deselecting only its channel while the other three segments continue to operate. The TSSOP-20 footprint keeps the solution compact enough for the tight routing channels typical of baseboards and mezzanine cards, and the small passive count means no external level shifter is needed when all devices share the same logic voltage domain.
Được đề xuất
Wearable Medical Monitoring Accessories
Wearables and portable medical accessories often need to attach several optional sensors, such as a temperature, motion and optical heart-rate module, over a single I2C port while keeping power low. The PCA9545APW allows the host to deselect downstream channels that are not in use, so idle sensors stay off the bus and do not hold the segment active. Per-channel interrupt inputs let the microcontroller sleep between measurements and wake on the specific sensor that has data ready, which directly reduces battery drain. The compact 20-pin TSSOP package fits the limited board area of a wristband or patch, and the active-LOW reset gives the firmware a clean way to recover a segment if an accessory is unplugged mid-transaction and leaves the bus held LOW.
Được đề xuất
Programmable Multi-Channel LED Driver Control
Addressable LED tiles and backlight modules frequently use several I2C LED drivers that must be updated in parallel but controlled independently. The PCA9545APW gives the controller four separately gated downstream bus segments, so LED banks on different zones can be refreshed in sequence and isolated from one another, reducing the risk that a stalled driver on one tile stalls the others. The interrupt inputs provide a fast health signal if a driver asserts its data line, and the active-LOW RESET re-initialises all four segments after a firmware fault or a power-sequencing event. Because the downstream buses are independent segments, each one can carry its own pull-up pair, which lets the designer tune rise time separately for long ribbon-cable runs versus short on-board drivers.
Được đề xuất
Tóm tắt các sản phẩm được đề xuất
Dữ liệu tham khảo kỹ thuật cho PCA9545APW — so sánh, hướng dẫn thiết kế và thông tin tuân thủ.
Hướng dẫn chọn lựa
If you need a second source on the same board, the Texas Instruments PCA9545A or TCA9545A in TSSOP-20 are pin-compatible drop-ins for the same footprint, which lets you qualify both vendors against one layout. The NXP PCA9545B and PCA9545C share the package but drop interrupt or reset functionality, so pick them only when those features are genuinely unused and you have verified the pin functions in the variant data sheet.
If you need fewer than four segments, or you do not use the interrupt and reset features at all, a two-channel or three-channel switch in a smaller package will be simpler and cheaper. Conversely, if your design needs eight segments, cascading two devices of this type is still possible, but a dedicated 8-channel multiplexer is usually the more elegant choice.
So sánh với các sản phẩm thay thế
| Tham số | Sản phẩm này | PCA9545BPW | PCA9545CPW | PCA9545APW | TCA9545APW | PCA9545APWR |
|---|---|---|---|---|---|---|
| Number of Downstream Channels | 4 | 4 | 4 | 4 | 4 | 4 |
| Package | 20-pin TSSOP (PW) | TSSOP-20 (PW) - same | TSSOP-20 (PW) - same | TSSOP-20 (PW) - same | TSSOP-20 (PW) - same | TSSOP-20 (PW) - same |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | Texas Instruments | Texas Instruments | Texas Instruments |
| Bus Type | I2C / SMBus bidirectional switch | I2C / SMBus | I2C / SMBus | Low-voltage I2C and SMBus switch | I2C / SMBus | Low-voltage I2C and SMBus switch |
| Channel Selection Method | Programmable control register | Programmable control register | Programmable control register | Programmable control register | Programmable control register | Programmable control register |
| Mounting Type | Surface mount | Surface mount | Surface mount | Surface mount | Surface mount | Surface mount |
Bảo phân biệt quan trọng
- Per-channel interrupt reporting plus bus recovery (vsPCA9543ADR)
- Full feature set in a 20-pin TSSOP footprint (vsPCA9545BPW)
- Second-source availability without a PCB change (vsPCA9545APW (Texas Instruments))
- Channel-level isolation of misbehaving targets (vsPCA9509PGM,125)
Ghi chú thiết kế
Treat the upstream bus and each of the four downstream channels as five separate I2C segments. Fit a dedicated pull-up resistor pair on SC0/SD0 through SC3/SD3, sized from the segment capacitance and target count, and do not rely on the upstream pull-ups to serve the downstream buses. Place the switch close to the host connector, keep each downstream pair routed as a short matched-length pair away from switching nodes, and keep the mux ground reference close to the return path of the bus it serves to limit ground bounce and false start conditions.
Do not leave a downstream channel floating. A channel with no connected target and no defined pull state can pull SDA LOW and look like a stuck bus to the host, which prevents the other channels from being used. Either populate the channel, hold it deselected through the control register, or provide defined pull-ups so the segment idles high. Also make sure RESET is never allowed to float: pull it high with a resistor or drive it from a host GPIO, because a floating reset input can deselect all channels at unpredictable moments during power-up sequencing.
Because the pass gates are bidirectional, the mux adds series resistance and a small propagation delay into both SCL and SDA of every enabled channel. Keep the enable state of a channel stable for the duration of a transaction and check rise-time margin against the bus capacitance of each segment rather than the whole board. For long cable or ribbon runs, place a bus extender such as the PCA9518 between the mux and the distant devices, and keep the interrupt lines short and away from the SCL/SDA routing to prevent crosstalk into the wake-up path.
A downstream target that is stuck in a LOW state can hold the whole mux input busy. Plan the reset and recovery sequence in firmware: on a bus timeout, de-assert RESET, wait for the internal power-on reset behaviour to deselect all channels, then re-select the required channel and retry the transaction. This sequence is far cheaper than a full system power cycle and is one of the main reasons to choose the PCA9545A variant over a simpler switch that has no reset or interrupt logic.
Thông tin tuân thủ
NXP lists the PCA9545APW as an active part. RoHS, REACH, lead-free and AEC-Q100 status for this specific ordering code are not stated in the product documentation pages and must be confirmed against the NXP material declaration for the exact part number before release.
