PCA9557DBR - 8-Bit I2C I/O Expander | Texas Instruments
料号： PCA9557DBR ✓ 量产中PCA9557DBR 概述
An I/O expander is an interface IC that extends the number of digital input or output lines available to a processor, microcontroller, or other bus master. Its place in the hardware hierarchy is I/O expander → interface controller → interface IC → semiconductor. The PCA9557DBR combines this bus interface with an 8-bit parallel port, making it useful for reducing package size, simplifying control wiring, and adding peripheral connections without requiring a larger host controller.
Key features include eight remotely controlled I/O lines, a two-wire I2C/SMBus-compatible interface with a stated bus speed of 400 kHz, and dedicated reset and configuration registers. According to the Texas Instruments product page, the device supports 2.3 V to 5.5 V VCC operation. These characteristics allow the same expander to be used in low-voltage embedded systems as well as conventional 5 V industrial, consumer, and communications equipment without changing the interface arrangement.
The device operates as a bus-addressed peripheral, with address and port behavior established through its configuration functions. Because its eight ports are controlled through a serial bus, software can read or change external logic levels without dedicating eight host GPIO pins. The reset function provides a defined initialization route for the expansion logic, while the configuration register supports controlled setup of the I/O behavior. Exact register addresses, polarity settings, and electrical limits should be confirmed in the manufacturer datasheet before firmware or PCB release.
Typical uses include low-pin-count embedded controllers, industrial control modules, sensor and actuator interfaces, LED or switch input expansion, and communication equipment needing additional discrete digital lines. The PCA9557DBR is particularly useful where a design must retain a compact host package while adding an eight-bit parallel interface. Because the peripheral communicates over I2C or SMBus, it also avoids the larger routing burden associated with another direct host-to-I/O connection.
When laying out a board, place the device close to the connector or controlled circuitry it serves, keep I2C routing short, and provide the required pull-up resistors on SCL and SDA. Account for the device address when multiple expanders share a bus, and use the reset input for a deterministic hardware startup path. Verify bus capacitance, pull-up resistance, voltage compatibility, and logic-level thresholds against the final system conditions.
This page consolidates the verified manufacturer description, distributor availability and pricing references, package details, and practical implementation guidance. It also distinguishes confirmed replacement information from parameters that still require datasheet-level verification, helping engineers evaluate the PCA9557DBR without confusing electrically similar devices with verified drop-in choices.
直接替换替代料： PCA9557DBR ——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： PCA9557DBR （相同外形与封装尺寸） ——差异在于 Interface.
PCA9557PWR
✅ 直接替换📋 参考替代料（不在目录中）
PCA9557D
✅ 直接替换联系询价
查看数据手册 →PCA9557DBRG4
✅ 直接替换📋 参考替代料（不在目录中）
PCA9557PWRG4
✅ 直接替换📋 参考替代料（不在目录中）
PCA9557DBR 规格参数
| Device Type | 8-bit I2C and SMBus low-power I/O expander |
| Number of I/O Ports | 8 bits |
| Supply Voltage Range | 2.3 V to 5.5 V |
| 接口 | I2C and SMBus |
| Bus Speed | 400 kHz |
| Number of I/O Lines | 8 |
| Reset Support | Yes |
| Configuration Register | Yes |
| Package Type | 16-pin SSOP |
| Package Width | 5.30 mm |
| Package Length | 0.209 inch |
| 安装类型 | Surface mount |
PCA9557DBR 引脚配置
| 引脚 1 | INT — Interrupt output |
| 引脚 2 | P0 — Port 0 input/output |
| 引脚 3 | P1 — Port 1 input/output |
| 引脚 4 | P2 — Port 2 input/output |
| 引脚 5 | P3 — Port 3 input/output |
| 引脚 6 | P4 — Port 4 input/output |
| 引脚 7 | P5 — Port 5 input/output |
| 引脚 8 | P6 — Port 6 input/output |
| 引脚 9 | P7 — Port 7 input/output |
| 引脚 10 | GND — Ground |
| 引脚 11 | A0 — Address input |
| 引脚 12 | A1 — Address input |
| 引脚 13 | SCL — Serial clock input |
| 引脚 14 | SDA — Serial data input/output |
| 引脚 15 | RESET — Active-low reset input |
| 引脚 16 | VCC — Power supply |
典型应用
PCA9557DBR 适用于 6 应用s: Embedded Control GPIO Expansion, Industrial Sensor and Actuator Interface, Communications Equipment Port Expansion, LED and Discrete Control Interface, Battery-Powered Portable Device Interface, Reset and Deterministic System Control.
Embedded Control GPIO Expansion
The PCA9557DBR fits low-pin-count embedded controllers that need more digital lines than the host package provides. Its eight parallel I/O bits are reached through the I2C or SMBus interface, allowing the controller to retain its compact package while driving indicators, reading switches, or controlling discrete peripheral signals. The verified 2.3 V to 5.5 V operating range accommodates both lower-voltage embedded rails and conventional 5 V logic. The 400 kHz bus rate is suitable for routine control traffic rather than high-volume streaming. Software must assign the device address and configure the ports, while the hardware reset input offers a deterministic initialization path. This arrangement reduces direct GPIO routing and can simplify PCB layout without introducing a second parallel bus.
推荐
Industrial Sensor and Actuator Interface
PCA9557DBR is useful in industrial modules where a controller must connect several discrete sensors, switches, or actuator-enable signals. The eight I/O bits provide a compact parallel interface while the serial bus preserves controller pin availability. Its 2.3 V to 5.5 V supply range permits operation across common industrial logic levels, although the final system must confirm input thresholds and output-current limits against the manufacturer datasheet. The reset and configuration registers support controlled initialization of external hardware. In a deployed control module, the expander can sit near field-side wiring while the microcontroller communicates over a short, protected bus. Isolation, surge protection, and environmental qualification requirements remain system-level concerns and should not be inferred solely from the expander specification.
推荐
Communications Equipment Port Expansion
The PCA9557DBR can expand a communications module without dedicating eight host-controller pins to ancillary digital hardware. It provides an 8-bit remote port through an I2C or SMBus connection rated for 400 kHz, making it appropriate for status indicators, control lines, and low-speed peripheral interfacing. The 2.3 V to 5.5 V range supports both 3.3 V and 5 V system rails when logic compatibility is maintained. Positioning the expander near its connector can shorten routed control traces, while the host reaches the port through firmware. Designers should avoid using it as a high-speed data interface, account for the address when several bus devices share the channel, and verify reset behavior during power sequencing. PCB placement should keep the serial bus away from high-energy switching paths.
推荐
LED and Discrete Control Interface
PCA9557DBR is well suited to managing grouped LED states or other simple digital control outputs through a host processor. The eight I/O lines allow software to update multiple indicators using one I2C address, reducing the number of direct host pins and simplifying board routing. Its 400 kHz bus rate is adequate for ordinary status-control traffic, and the 2.3 V to 5.5 V supply range allows integration with common embedded voltage rails. The design must account for the actual output-current capability of each line and the aggregate device limits in the manufacturer datasheet; the supplied data does not establish those values. Series current limiting remains necessary where the load path requires it. Firmware should configure the port direction and output state before enabling attached circuitry, using the hardware reset input as part of a predictable startup sequence.
推荐
Battery-Powered Portable Device Interface
PCA9557DBR can reduce the pin count and board complexity of a battery-powered portable product that needs switches, indicators, or peripheral-control signals. The device supports operation down to 2.3 V, allowing it to share a suitable low-energy logic rail with an embedded controller, and its low-power designation reflects its role as a remote I/O expander. The verified data does not provide a numerical quiescent-current figure, so battery-budget calculations must use the latest manufacturer values. Eight controllable lines through I2C can save package area and simplify firmware compared with direct GPIO connections. During sleep states, software can configure unused pins to minimize current. Pull-up resistors should remain switched or otherwise managed only if the system power architecture permits it, because continuously powered pull-ups can undermine standby efficiency.
推荐
Reset and Deterministic System Control
PCA9557DBR can support deterministic expansion-port initialization in systems where external control lines must enter a known state during power-up. Its dedicated reset function and configuration register provide hardware and software mechanisms for organizing the eight I/O bits. The expander is connected to the same 2.3 V to 5.5 V-compatible control environment and communicates at a stated 400 kHz, allowing the host to reconfigure outputs after reset. In a multi-rail instrument, the reset line can be coordinated with the system supervisor so that loads remain disabled until the required initialization sequence completes. The host must still define valid states for every connected load and avoid controlling safety-critical outputs solely through a general-purpose expander. Review reset timing, power-on states, and bus fault behavior in the manufacturer datasheet.
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推荐产品汇总
工程参考数据： PCA9557DBR ——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 | PCA9557PWR | PCA9557D | PCA9557DBRG4 | PCA9557PWRG4 |
|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Package | 16-SSOP | 16-SSOP | 16-SSOP | 16-SSOP | 16-SSOP |
| Device Type | 8-bit I2C/SMBus I/O expander | 8-bit I2C/SMBus I/O expander | 8-bit I2C/SMBus I/O expander | 8-bit I2C/SMBus I/O expander | 8-bit I2C/SMBus I/O expander |
| Number of I/O Lines | 8 | 8 | 8 | 8 | 8 |
| Operating Voltage Range | 2.3 V to 5.5 V | 2.3 V to 5.5 V | 2.3 V to 5.5 V | 2.3 V to 5.5 V | 2.3 V to 5.5 V |
| Bus Interface | I2C and SMBus | I2C and SMBus | I2C and SMBus | I2C and SMBus | I2C and SMBus |
| Bus Speed | 400 kHz | 400 kHz | 400 kHz | 400 kHz | 400 kHz |
| Reset and Configuration Registers | Yes | Yes | Yes | Yes | Yes |
关键差异点
- Eight-port expansion with reset and configuration registers （对比 PCA9557PWR)
- Directly verified complete replacement （对比 PCA9557DBRG4)
- Broad logic-rail compatibility （对比 PCA9557PWRG4)
设计说明
Place PCA9557DBR close to the connector, switches, or output circuitry that it serves, while keeping the SCL and SDA route away from switching nodes and high-current paths. Route the serial bus as a short, continuous bus with minimal stubs. Place the required pull-up resistors at a suitable location in the bus topology, and check the complete network capacitance before using the stated 400 kHz maximum bus rate.
Operate the PCA9557DBR from a supply within its verified 2.3 V to 5.5 V range. The I2C pull-up voltage, host-controller levels, and attached logic must be compatible with that rail. Add local supply decoupling and avoid sharing high-current return paths with the expander. Exact output-current limits and logic thresholds are not present in the supplied verified data and must be checked in the manufacturer datasheet before driving loads.
Do not assume that any 8-bit I2C expander is a drop-in replacement. Check the pinout, address behavior, reset polarity, port-direction defaults, and register map against the PCA9557 datasheet. The PCA9557PWR and PCA9557DBRG4 comparison results report compatible packages and functions, but production substitution still requires confirmation of the exact ordering suffix and package drawing.
合规信息
The supplied verified data does not explicitly state RoHS, REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals status. No compliance claim has been inferred from the G4 ordering suffix.