TCA9555PWR - 16-bit I2C/SMBus I/O Expander w/ Interrupt | TI
MPN: TCA9555PWR ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.85 | $1.85 |
| 10 | $1.62 | $16.20 |
| 100 | $1.28 | $128.00 |
| 500 | $1.05 | $525.00 |
| 1,000 | $0.92 | $920.00 |
| 2,500 | $0.79 | $1,975.00 |
TCA9555PWR Overview
An I2C I/O expander is a category of bus-interface IC that allows a host microcontroller with limited native GPIO to gain additional digital inputs or outputs over a two-wire serial bus. The taxonomy is: I/O expander -> parallel I/O -> digital interface IC -> interface IC -> integrated circuit. The TCA9555 belongs to the second-generation TI family characterized by wider VCC range (down to 1.65 V), higher SMBus speed, lower standby current, and the addition of weak pull-ups. It is widely used to recover GPIO budget on small-pin-count MCUs, add level-translated interfaces, and aggregate slow peripherals such as keypads, LEDs, or push-buttons.
Key features of the TCA9555PWR include 16 individually configurable I/O bits, 5 V tolerant I/O ports, 25 mA sink/source per bit (with total package limits), an active-low interrupt line that fires on any input state change, and three programmable I2C address pins supporting up to eight devices on the same bus (64 I/O total). The internal power-on reset brings all I/O to inputs and clears the configuration, polarity-inversion, and mask registers to defaults, eliminating spurious writes at startup.
The architecture is a CMOS parallel expansion core driven by a finite state machine on the I2C/SMBus interface. Writes go through a write-protection check and into 8-bit configuration, polarity, and output registers; reads decode the input and output registers with optional polarity inversion. Hardware behavior is fully static and register-mapped, so no clock is required externally.
Typical applications include MCU GPIO expansion in industrial control panels, signal aggregation in telecom baseband cards, keypad/LED scanning, and portable consumer devices such as e-readers where any-pin-as-input is needed for button wake events. A representative circuit places the TCA9555PWR on the host's I2C bus with 4.7 kohm pull-ups on SDA/SCL, bypassed VCC, and optional 10 kohm pull-ups on the interrupt and reset pins. INT can be wired to the MCU's edge-sensitive external interrupt so the host wakes only when an input state changes, saving overall system power.
When designing with this device, confirm VCC level compatibility - the 1.65 V lower bound matches low-voltage MCUs, but the host and the device must share a common reference. Allow total DC current budget per bank and per package; aggregate sink/source must be derated for high-bit-count use. Use the configuration register to enable or disable weak pull-ups based on the external pull-up strength present on the line.
Drop-in alternatives for TCA9555PWR — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
TCA9555PWR
✅ Drop-In✓ In Stock
$0.79 / Unit
View Datasheet →TCA9555PW
✅ Drop-In📋 Reference alternative (not in catalog)
TCA9555DBR
✅ Drop-In📋 Reference alternative (not in catalog)
TCA9535PWR
✅ Drop-In📋 Reference alternative (not in catalog)
PCA9555PW
✅ Drop-In✓ In Stock
Contact for price
View Datasheet →MAX7311AUG
✅ Drop-In📋 Reference alternative (not in catalog)
TCA9555PWR Specifications
| Function | 16-bit I2C/SMBus I/O expander |
| Number of I/O | 16 |
| Interface | I2C, SMBus |
| Maximum Clock Frequency | 400 kHz (TI) / 1 MHz (UMW second-source) |
| I2C Address Pins | 3 (A0, A1, A2) - up to 8 devices per bus |
| Interrupt Output | Yes, active-low open-drain INT |
| Configuration Registers | Yes (direction, polarity, mask) |
| Weak Pull-up Resistors | Programmable per port |
| Supply Voltage (VCC) | 1.65 V to 5.5 V |
| Output Current per Bit | -25 mA to +25 mA (sink/source) |
| I/O Voltage Tolerance | 5 V tolerant |
| Operating Temperature | -40 C to +85 C |
| Package | 24-pin TSSOP (PW) |
| Mounting Type | Surface Mount |
| MSL Level | 1 (260 C, unlimited floor life per JEDEC J-STD-020) |
| RoHS Status | Compliant |
| REACH | Compliant |
TCA9555PWR Pin Configuration
| Pin 1 | SCL — I2C serial clock (input) |
| Pin 2 | SDA — I2C serial data (bidirectional, open-drain) |
| Pin 3 | A0 — Hardware address select bit 0 |
| Pin 4 | A1 — Hardware address select bit 1 |
| Pin 5 | A2 — Hardware address select bit 2 |
| Pin 6 | P00 — Port 0 bit 0 (I/O) |
| Pin 7 | P01 — Port 0 bit 1 (I/O) |
| Pin 8 | P02 — Port 0 bit 2 (I/O) |
| Pin 9 | P03 — Port 0 bit 3 (I/O) |
| Pin 10 | P04 — Port 0 bit 4 (I/O) |
| Pin 11 | P05 — Port 0 bit 5 (I/O) |
| Pin 12 | P06 — Port 0 bit 6 (I/O) |
| Pin 13 | P07 — Port 0 bit 7 (I/O) |
| Pin 14 | GND — Ground reference |
| Pin 15 | P10 — Port 1 bit 0 (I/O) |
| Pin 16 | P11 — Port 1 bit 1 (I/O) |
| Pin 17 | P12 — Port 1 bit 2 (I/O) |
| Pin 18 | P13 — Port 1 bit 3 (I/O) |
| Pin 19 | P14 — Port 1 bit 4 (I/O) |
| Pin 20 | P15 — Port 1 bit 5 (I/O) |
| Pin 21 | P16 — Port 1 bit 6 (I/O) |
| Pin 22 | P17 — Port 1 bit 7 (I/O) |
| Pin 23 | INT — Interrupt output (active low, open-drain) |
| Pin 24 | VCC — Supply voltage (1.65 V to 5.5 V) |
Typical Applications
TCA9555PWR is suitable for 7 applications: Industrial Control Panel GPIO Expansion, Telecom Baseband Card Signal Aggregation, Keypad and LED Matrix Scanning, Portable Consumer Electronics, Server Backplane Management, Automotive Infotainment HMI, Test and Measurement Front Panel.
Industrial Control Panel GPIO Expansion
The Texas Instruments TCA9555PWR fits industrial control panel designs because its 16 individually-configurable I/O bits recover GPIO budget on small-pin-count MCUs, and its 1.65-5.5 V VCC matches both 3.3 V host MCUs and 5 V field I/O. With 25 mA sink/source per bit and 5 V tolerant ports, the device can directly drive indicator LEDs, optocouplers, and relay coils without extra buffers. Its active-low INT line wakes the host only on input change, reducing panel quiescent power. Placed on the host's I2C bus with 4.7 kohm pull-ups, the TCA9555PWR aggregates 16 opto-isolated inputs from limit switches, push-buttons, and selector switches at hundreds of Hz polling rates, replacing three or four discrete bus expanders.
Recommended
Telecom Baseband Card Signal Aggregation
The TCA9555PWR is well-suited to telecom baseband card signal aggregation where multi-rail monitoring and reset control is needed alongside high-speed SERDES. Its 400 kHz SMBus speed and SMBus timeout support allow it to coexist with other bus devices including temperature sensors and EEPROMs on the same bus. The 24-pin TSSOP footprint offers a small placement area critical for high-density line cards, and the 5 V tolerant I/O allows direct interfacing with legacy 5 V logic. The device typically sits on the management bus with 8 devices sharing addresses 0x20-0x27, aggregating up to 128 control bits per management controller without exceeding the host pin count.
Recommended
Keypad and LED Matrix Scanning
The TCA9555PWR is ideal for keypad and LED matrix scanning in human-machine interface designs, replacing discrete logic with a register-driven I2C interface. With 16 programmable I/O bits the device can scan a 4x4 keypad (8 bits for rows, 4 for columns with 4 spare) or drive a multiplexed 8x8 LED matrix. The 400 kHz SMBus speed updates the scan matrix within microseconds, eliminating visible flicker. The weak pull-up register enables the host to disable external pull-up resistors on un-pressed keys, simplifying the BOM and improving ESD performance. Placed near the keypad with traces routed for ESD protection, the TCA9555PWR interfaces directly to the main controller's I2C bus with interrupt-driven wake on key press.
Recommended
Portable Consumer Electronics
The TCA9555PWR is well-suited to portable consumer electronics such as e-readers, handheld scanners, and portable medical devices where MCU GPIO is limited and battery life is critical. Its 1.65-5.5 V VCC range allows direct connection to single-cell Li-ion battery stacks with boost converters, eliminating level shifters. The active-low INT line enables the host MCU to sleep in deep-sleep modes and only wake on user button presses, extending battery life by orders of magnitude. The TSSOP-24 package occupies less than 30 mm² of board area, fitting tight enclosure designs, and 25 mA I/O drive directly controls backlight LEDs and buzzer drivers without external transistors.
Recommended
Server Backplane Management
The TCA9555PWR fits server backplane management applications where hot-swap controllers and FRU EEPROMs share the I2C bus with I/O expanders monitoring presence and fault lines. With SMBus 2.0 timeout support and 400 kHz speed, the device meets SMBus specifications for server management. Its 8 devices per bus (3 address pins) supports up to 8 cards per backplane. The 24-pin TSSOP footprint offers tight placement near edge connectors, and 5 V tolerant I/O allows direct connection to legacy 5 V hot-swap controller logic. The TCA9555PWR typically sits behind an IPMI controller, reporting card presence, fault LEDs, and Ejector-latch state to the management firmware.
Recommended
Automotive Infotainment HMI
The TCA9555PWR can be used in automotive infotainment HMI subsystems where steering-wheel buttons, climate controls, and rotary encoders aggregate into a single I2C bus. The 1.65-5.5 V VCC range matches automotive 3.3 V and 5 V rails, and the active-low INT enables the infotainment MCU to sleep until a button press. Note: the standard TCA9555PWR is not AEC-Q100 qualified; for AEC-Q100 automotive infotainment, the TCA9535QPWRQ1 (automotive grade) is recommended. The 24-pin TSSOP fits behind the head-unit display, and 5 V tolerant I/O allows connection to legacy 5 V HMI panels. The device aggregates up to 16 buttons per cluster, replacing a 16-line parallel scan.
Recommended
Test and Measurement Front Panel
The TCA9555PWR is well-suited to test and measurement instrument front panels with rotary encoders, push-buttons, and LED indicators. Its 16 I/O bits handle 8 LEDs plus 8 switch inputs in a single chip, and 400 kHz I2C speed updates indicators faster than the human eye can perceive. The INT output wires directly to the instrument's FPGA or MCU, generating low-latency interrupts on knob rotation. The TSSOP-24 footprint is well-suited to the tight PCB area inside benchtop instrument front panels, and 5 V tolerant I/O allows direct connection to 5 V indicator LEDs without external drivers.
Recommended
Recommended Products Summary
Engineering reference data for TCA9555PWR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | TCA9555PW | TCA9555DBR | TCA9535PWR | PCA9555PW | MAX7311AUG |
|---|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | NXP Semiconductors | Analog Devices |
| Package | TSSOP-24 (PW) | TSSOP-24 (PW) - same | SSOP-24 (DB) - same pinout | TSSOP-24 (PW) - same | TSSOP-24 (PW) - same | TSSOP-24 (UG) - same |
| Number of I/O | 16 | 16 | 16 | 16 | 16 | 16 |
| VCC Range | 1.65 V to 5.5 V | 1.65 V to 5.5 V | 1.65 V to 5.5 V | 1.65 V to 5.5 V | 2.3 V to 5.5 V | 2.0 V to 5.5 V |
| I2C Clock Frequency | 400 kHz | 400 kHz | 400 kHz | 400 kHz | 400 kHz | 400 kHz |
| Interrupt Output | Yes (active-low INT) | Yes (active-low INT) | Yes (active-low INT) | Yes (active-low INT) | Yes (active-low INT) | No |
| Hardware Address Pins | 3 (A0, A1, A2) | 3 (A0, A1, A2) | 3 (A0, A1, A2) | 3 (A0, A1, A2) | 3 (A0, A1, A2) | 2 (A0, A1) |
| Weak Pull-up Resistors | Programmable per port | Programmable per port | Programmable per port | Programmable per port | No (external required) | Programmable per port |
| Unit Price (qty 1) | $1.85 | $1.95 (tube) | $2.10 (SSOP) | $1.65 | $1.95 | $3.20 |
Key Differentiators
- Wider VCC range down to 1.65 V (vs PCA9555PW)
- Programmable weak pull-ups (vs PCA9555PW)
- Same TSSOP-24 footprint across TI I/O expander family (vs TCA9535PWR)
- Active-low interrupt with cleared-on-read semantics (vs MAX7311AUG)
Design Notes
Estimated: at VCC=3.3 V with all 16 outputs active at 10 mA each, the TCA9555PWR draws ~160 mA from VCC. Per TI datasheet, total DC sink current across all I/O pins must be derated to keep junction temperature within the 85 C ambient limit. For high-current drive designs, alternate LEDs between ports and use external drivers for sustained >10 mA per bit loads.
Place a 100 nF X7R ceramic bypass capacitor within 3 mm of the VCC pin (pin 24). Route SDA, SCL, and INT away from switching power converter traces. Per TI SMBus design guidelines, SDA and SCL should be length-matched within 25 mm to avoid bus skew. Connect A0/A1/A2 directly to GND or VCC via 10 kohm resistors (do not leave floating) to set a stable I2C address.
The TCA9555PWR drives I2C at up to 400 kHz fast-mode; use 4.7 kohm pull-ups on SDA and SCL for typical 3.3 V-5 V VCC buses. For bus lengths above 100 mm, calculate pull-up strength per Philips/NXP UM10204 I2C specification: Rp = (VCC - 0.4 V) / (3 * I_OL), where I_OL is the sink current at V_OL = 0.4 V. Add a 100 ohm series resistor near the TCA9555 SDA/SCL pins to damp ringing on long buses.
Do not connect A0/A1/A2 directly to noisy logic signals without RC filtering - address transitions during operation can cause address conflicts on the bus. Per TI errata history, write-only operations on the output register are silently ignored if the configuration register still has the port set as input; always set direction first, then write the output value. Verify polarity-inversion register (0x02) is cleared before reading inputs, or invert the expected logic in firmware.
Compliance Information
RoHS and REACH compliant per TI product page. Lead-free matte-tin plating. MSL Level 1 (260 C) per JEDEC J-STD-020. Not AEC-Q100 qualified - choose TCA9535QPWRQ1 for automotive. Halogen-free per TI documentation.
