PCA9535RGER - 16-Bit I2C/SMBus I/O Expander, 400kHz | TI
MPN: PCA9535RGER ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.42 | $1.42 |
| 10 | $1.21 | $12.10 |
| 100 | $0.95 | $95.00 |
| 500 | $0.79 | $395.00 |
| 1,000 | $0.68 | $680.00 |
| 3,000 | $0.58 | $1,740.00 |
PCA9535RGER Overview
An I/O expander is a category of interface IC designed to add GPIO lines to a microcontroller when its native pin count is exhausted. The PCA9535 belongs to the I/O expander family, which is itself a sub-category of interface ICs and ultimately of the broader digital semiconductor hierarchy. By using only two MCU pins (SCL and SDA), the PCA9535 adds 16 additional GPIOs that behave like native port pins, making it indispensable in space-constrained designs.
Key features include 5 V tolerant I/O, 25 mA typical sink capability per output (allowing direct LED drive), latched inputs that eliminate spurious interrupts, and a hardware address pin that supports up to eight devices on the same I2C bus (128 total I/Os). The interrupt is cleared by reading the input port register, simplifying firmware. An internal power-on reset initializes all registers to known states.
The architecture uses CMOS logic with low standby current consumption, supporting always-on applications. Internal pull-up resistors are not included on the I/O pins, so external resistors are typically required; SCL and SDA must be pulled high externally per I2C bus specification.
Typical applications include server backplane management, industrial PLCs and IO-Link modules, gaming consoles, HVAC control boards, and any embedded system requiring extra buttons, LEDs, or relay drivers. The wide voltage range supports both 3.3 V and 5 V MCUs.
When designing, ensure SCL/SDA pull-ups are sized correctly for bus capacitance. Multiple PCA9535 devices can share the bus by using different slave addresses (A0/A1/A2). Consider the INT pin behavior - it is active-low and requires a pull-up.
This page consolidates distributor pricing, drop-in cross-brand equivalents (NXP PCA9535, onsemi CAT9555), and practical PCB layout notes not always covered in the manufacturer datasheet.
Drop-in alternatives for PCA9535RGER — 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:
TCA9555RGER
✅ Drop-In📋 Reference alternative (not in catalog)
PCA9535RGERG4
✅ Drop-In📋 Reference alternative (not in catalog)
PCA9535BS,118
✅ Drop-In📋 Reference alternative (not in catalog)
CAT9555HVGI
✅ Drop-In📋 Reference alternative (not in catalog)
PCA9555RGER
✅ Drop-In📋 Reference alternative (not in catalog)
PCA9535RGER Specifications
| Number of I/O | 16 |
| Interface | I2C, SMBus |
| Clock Frequency (Max) | 400 kHz |
| Supply Voltage (VCC) | 2.3 V to 5.5 V |
| Output Drive Current | 25 mA sink/source (typical) |
| Interrupt Output | Yes (active-low INT) |
| Slave Address Configuration | 3 address pins (A0, A1, A2) - up to 8 devices per bus |
| I/O Tolerance | 5 V tolerant |
| Configuration Registers | Separate Input/Output direction registers |
| Package | VQFN-24 (RGE) 4x4 mm with exposed pad |
| Mounting Type | Surface Mount |
| Operating Temperature | -40 C to +85 C |
| RoHS Status | Compliant |
| Power-On Reset | Yes (registers default to defined state) |
PCA9535RGER Pin Configuration
| Pin 1 | P00 — I/O port 0 bit 0 (bidirectional) |
| Pin 2 | P01 — I/O port 0 bit 1 (bidirectional) |
| Pin 3 | P02 — I/O port 0 bit 2 (bidirectional) |
| Pin 4 | P03 — I/O port 0 bit 3 (bidirectional) |
| Pin 5 | P04 — I/O port 0 bit 4 (bidirectional) |
| Pin 6 | P05 — I/O port 0 bit 5 (bidirectional) |
| Pin 7 | P06 — I/O port 0 bit 6 (bidirectional) |
| Pin 8 | P07 — I/O port 0 bit 7 (bidirectional) |
| Pin 9 | VCC — Power supply (2.3 V to 5.5 V) |
| Pin 10 | GND — Ground |
| Pin 11 | P10 — I/O port 1 bit 0 (bidirectional) |
| Pin 12 | P11 — I/O port 1 bit 1 (bidirectional) |
| Pin 13 | P12 — I/O port 1 bit 2 (bidirectional) |
| Pin 14 | P13 — I/O port 1 bit 3 (bidirectional) |
| Pin 15 | P14 — I/O port 1 bit 4 (bidirectional) |
| Pin 16 | P15 — I/O port 1 bit 5 (bidirectional) |
| Pin 17 | P16 — I/O port 1 bit 6 (bidirectional) |
| Pin 18 | P17 — I/O port 1 bit 7 (bidirectional) |
| Pin 19 | INT — Interrupt output (active-low, open-drain) |
| Pin 20 | A0 — Slave address bit 0 (with pull-up) |
| Pin 21 | A1 — Slave address bit 1 (with pull-up) |
| Pin 22 | A2 — Slave address bit 2 (with pull-up) |
| Pin 23 | SCL — I2C serial clock line |
| Pin 24 | SDA — I2C serial data line |
Typical Applications
PCA9535RGER is suitable for 6 applications: Server Backplane Management, Industrial PLC Digital I/O Module, HVAC Control Board, Gaming Console Button Matrix, Smart Home IoT Gateway, Automotive Infotainment Auxiliary I/O.
Server Backplane Management
The PCA9535RGER's 16 GPIOs at 2.3-5.5V operation make it ideal for server backplane management where it monitors hot-swap presence signals, drives status LEDs, and reads fan tachometer inputs. Placed on the management controller's I2C bus, it extends the BMC's limited GPIO count by 16 lines per device (128 with eight units sharing A0-A2 address pins). Its 400 kHz Fast-Mode I2C keeps bus latency low even with multiple expanders, while the active-low INT pin alerts the BMC immediately to any state change without continuous polling. Per the TI datasheet, 25 mA sink capability drives backplane LEDs directly without extra transistor buffers.
Recommended
Industrial PLC Digital I/O Module
In industrial PLCs and distributed I/O modules, the PCA9535RGER provides optocoupler-isolated digital input buffering and 24V-tolerant output driving via external transistors. The 5V tolerant I/O pins accept 24V signals through external resistor dividers, allowing direct connection to industrial sensors. Its 2.3-5.5V VCC range accommodates 3.3V MCU hosts while the I2C bus runs reliably over cable lengths typical of industrial field wiring. Three address pins (A0-A1-A2) let one MCU control up to eight PCA9535RGER units, yielding 128 isolated I/O channels per controller. Hardware interrupt output simplifies deterministic response to critical field events.
Recommended
HVAC Control Board
The PCA9535RGER is well-suited to HVAC control boards where it scans multiple pushbuttons, drives relay coils via external transistors, and reads thermostat sensors. Its wide 2.3-5.5V operating range tolerates supply variations common in HVAC power environments, while the hardware interrupt pin wakes the host MCU only when a button press or sensor change occurs - reducing average power consumption. Sixteen GPIOs cover the typical HVAC I/O requirement (multiple zone valves, fan speeds, and mode switches) using a single MCU pin pair. Per TI datasheet, latch-up performance exceeds 100 mA per JESD78, ensuring robustness in electrically noisy HVAC environments.
Recommended
Gaming Console Button Matrix
In gaming consoles and arcade controllers, the PCA9535RGER scans key matrices for buttons and joystick positions, expanding a single MCU's I2C bus into 16 individually accessible inputs. Fast-Mode 400 kHz I2C keeps input latency below 5 ms even with multiple expanders, satisfying real-time game response requirements. The active-low INT pin triggers immediate interrupt-driven reading of the changed input register, minimizing CPU overhead compared to polled designs. Each input supports 5V tolerance for legacy button matrix wiring, and 25 mA sink/source drives small RGB status LEDs directly for player feedback indicators.
Recommended
Smart Home IoT Gateway
The PCA9535RGER adds low-cost, low-power GPIO expansion to IoT smart-home gateways where it interfaces with Zigbee/Z-Wave modules, controls relay outputs for lights and locks, and reads wall switch states. Its 2.3-5.5V VCC range supports both battery-powered sensor nodes (operating at 3.3V) and mains-powered gateway hubs (operating at 5V). Up to eight devices per bus give the gateway 128 GPIOs to handle whole-home automation. The INT output enables the host MCU to sleep between events, critical for battery-powered end nodes that must run for years on a single cell. Per TI datasheet, standby current is in the microamp range.
Recommended
Automotive Infotainment Auxiliary I/O
In automotive infotainment head units, the PCA9535RGER extends the head-unit MCU's GPIO count to drive multiple rotary encoder inputs, button backlights, and auxiliary relay outputs (HVAC blend doors, lighting controllers). Note: automotive designs typically require AEC-Q100 qualified parts - use TI's PCA9535RGER in non-critical body electronics only; for safety-critical paths select an AEC-Q100 variant. The wide VCC range handles 12V battery transients through external regulation, while the robust I2C interface tolerates noisy automotive electrical environments. Sixteen GPIOs handle typical head-unit I/O without consuming additional MCU pins needed for video and audio interfaces.
Recommended
Recommended Products Summary
Engineering reference data for PCA9535RGER — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | TCA9555RGER | PCA9535RGERG4 | PCA9535BS,118 | CAT9555HVGI | PCA9555RGER |
|---|---|---|---|---|---|---|
| Package | VQFN-24 (RGE) 4x4 mm | VQFN-24 (RGE) - same | VQFN-24 (RGE) - same | VQFN-24 - same | VQFN-24 - same | VQFN-24 (RGE) - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | NXP Semiconductors | onsemi | Texas Instruments |
| Number of I/O | 16 | 16 | 16 | 16 | 16 | 16 |
| Supply Voltage | 2.3 V to 5.5 V | 1.65 V to 5.5 V (wider) | 2.3 V to 5.5 V | 2.3 V to 5.5 V | 2.3 V to 5.5 V | 1.65 V to 5.5 V (wider) |
| Clock Frequency | 400 kHz | 400 kHz | 400 kHz | 400 kHz | 400 kHz | 400 kHz |
| Interface | I2C, SMBus | I2C, SMBus | I2C, SMBus | I2C, SMBus | I2C, SMBus | I2C, SMBus |
| Interrupt Output | Yes (active-low INT) | Yes (active-low INT) | Yes (active-low INT) | Yes (active-low INT) | Yes (active-low INT) | Yes (active-low INT) |
Key Differentiators
- Industry-standard 16-bit I2C GPIO register map (vs MCP23017-E/ML)
- 5V tolerant I/O with 2.3-5.5V VCC (vs PCA9555RGER)
- Up to 8 devices per bus (128 GPIOs) (vs TCA6408RGTR)
Design Notes
Estimated: keep I2C bus traces short (under 100 mm) and route SCL/SDA as a differential pair with ground underneath to minimize crosstalk. Place 4.7 kohm pull-up resistors on SCL and SDA close to the master MCU. The exposed thermal pad (EP) of the VQFN-24 must be soldered to a grounded copper pour of at least 10 mm x 10 mm to meet datasheet thermal ratings.
Do not forget external pull-ups on SCL, SDA, INT, and the A0/A1/A2 address pins. The PCA9535RGER's INT output is open-drain and requires a pull-up to VCC (typically 10 kohm). When cascading multiple PCA9535RGER devices on the same bus, ensure each has a unique A0/A1/A2 address combination - duplicate addresses cause bus contention. The I/O pins do not include internal pull-ups; add external resistors when reading mechanical switches.
The I2C bus is sensitive to capacitance - total bus capacitance including all device pins and trace capacitance must remain under 400 pF for Fast-Mode 400 kHz operation per the I2C specification. When using long cables (typical in industrial applications), add a bus extender like the LTC4316 or P82B96. Place 100 pF to 1 nF bypass capacitors on VCC near each PCA9535RGER device to suppress switching noise from the bus.
Estimated: the PCA9535RGER consumes approximately 1 mA during active I2C transactions and microamps in standby. For battery-powered applications, use the TCA9555RGER which has lower standby current per TI's datasheet. When driving LEDs directly from the I/O pins, calculate power dissipation: P = VCC x I_total; ensure it does not exceed the package's thermal limit (typically 200 mW for VQFN-24 at 25 C ambient with proper copper).
Compliance Information
RoHS and REACH compliant per TI product page. PCA9535RGER is not AEC-Q100 qualified; for automotive applications, select an AEC-Q100 qualified variant (e.g., TCA9535-Q1) or add external qualification testing.
