NXP Semiconductors PCA9745BTW/Q900J

Overview

PCA9745BTW/Q900J from NXP Semiconductors is a 16-channel SPI-controlled constant-current LED driver optimized for RGBA LED dimming and blinking in amusement products. It delivers up to 57 mA per channel, supports 20 V LED supply, features 8-bit individual PWM (31.25 kHz), 8-bit group PWM (122 Hz fixed or 15 Hz–16.8 s programmable), and integrated gradation control with four independent timing groups.

For engineers reviewing the PCA9745BTW/Q900J datasheet, PCA9745BTW/Q900J pinout, PCA9745BTW/Q900J application, or PCA9745BTW/Q900J equivalent, key selection criteria include daisy-chain SPI interface (25 MHz), thermal shutdown, open/short load detection, HTSSOP28 package with exposed thermal pad, and AEC-Q100 compliance for automotive lighting use cases.

Technical Context

The PCA9745BTW/Q900J implements dual PWM architecture: per-channel 31.25 kHz PWM with 256-step linear duty control (0–100 %), and shared group PWM with 256-step resolution supporting either 122 Hz dimming or programmable blink frequencies from 15 Hz to once every 16.8 seconds. Its 4-wire SPI interface enables daisy-chaining and supports up to 25 MHz clock rate with noise filtering on SDI/SCLK inputs.

Gradation control uses four independent register groups to define ramp-up/down rate, step time (0.5 ms–512 ms), hold ON/OFF duration (0–6 s), and final current level-each assignable per channel via GRAD_GRP_SELx and GRAD_MODE_SELx registers. Internal 8 MHz oscillator eliminates external components, and REXT-based current scaling allows precise output gain tuning from 225 µA to 57 mA.

Key Specifications

Pinout & Package

PCA9745BTW/Q900J is housed in an HTSSOP28 package (SOT1172-3) with 4.4 mm body width, 0.65 mm lead pitch, and exposed thermal pad connected to VSS. The thermal pad must be soldered to a PCB thermal pad with vias for reliable thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar constant-current LED driver applications.

Compared with TLC5947 and IS31FL3731, PCA9745BTW/Q900J uniquely combines AEC-Q100 qualification, hardware OE control, programmable group blink timing, and four independent gradation groups-making it optimal for automotive and amusement applications demanding robust, self-contained LED animation.

Availability

PCA9745BTW/Q900J is available at Aetrix Electronics and suitable for amusement lighting control, automotive interior lighting, keypad backlighting, and RGB status display panels requiring stable component supply and long-term lifecycle support.

Supply support for PCA9745BTW/Q900J includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

NXP Semiconductors is a global semiconductor leader specializing in secure connectivity solutions for automotive, industrial, and IoT applications, with deep expertise in mixed-signal and power-efficient IC design.

The PCA9745B product line was designed specifically for high-reliability, multi-color LED control in demanding environments-emphasizing daisy-chain scalability, integrated diagnostics, and autonomous gradation sequencing without host processor burden.

FAQ

What is the maximum LED supply voltage supported by the PCA9745BTW/Q900J?

The PCA9745BTW/Q900J supports up to 20 V on its LED output pins when they are in the OFF state. This allows direct connection to common LED string supplies without additional voltage translation, provided the VDD supply remains within its 3 V–5.5 V operating range. The 20 V rating applies to the LED sink terminals (LED0–LED15) under non-conducting conditions and is validated across the full −40 °C to +105 °C temperature range specified for PCA9745BTW/Q900J.

How does the gradation control function in the PCA9745BTW/Q900J differ from standard PWM dimming?

Gradation control in the PCA9745BTW/Q900J provides autonomous, register-programmed LED current ramping (fade-in/fade-out) using four independent timing groups-each configurable for ramp rate, step time (0.5 ms–512 ms), hold duration (0–6 s), and final current level. Unlike standard PWM, which requires continuous MCU updates for smooth transitions, gradation runs independently after initialization, freeing the host processor. This capability is implemented in PCA9745BTW/Q900J via dedicated registers like RAMP_RATE_GRP0 and STEP_TIME_GRP0.

Is the PCA9745BTW/Q900J pin-compatible with other members of the PCA9745B family?

Yes, PCA9745BTW/Q900J shares identical pinout and package (HTSSOP28) with all PCA9745B variants including PCA9745BTW and PCA9745BTWJ. All share the same SOT1172-3 footprint, thermal pad layout, and electrical pin assignments-including REXT, OE, CS, SDO, and 16 LED outputs. Functional differences (e.g., AEC-Q100 qualification in PCA9745BTW/Q900J) do not affect mechanical or electrical compatibility, enabling drop-in replacement within the same family.

What protection features are integrated into the PCA9745BTW/Q900J?

The PCA9745BTW/Q900J integrates per-channel open-load and short-circuit detection, overtemperature shutdown, and ESD protection exceeding 4 kV HBM. Fault status is reported through dedicated EFLAG0–EFLAG3 registers readable via SPI. Thermal shutdown activates when the internal junction temperature exceeds the process limit, and the device automatically recovers upon cooling. These protections are active across the full −40 °C to +105 °C operating range of PCA9745BTW/Q900J.

Can multiple PCA9745BTW/Q900J devices be connected in series for expanded channel count?

Yes, PCA9745BTW/Q900J supports daisy-chained SPI configuration: the SDO pin of one device connects to the SDI pin of the next, with shared SCLK and CS lines. Each device in the chain responds to its own address window, allowing up to 16 devices (256 total channels) on a single bus. The 25 MHz SPI clock supports fast update rates even in large chains, and noise filters on SDI/SCLK inputs maintain signal integrity-key for reliable operation in electrically noisy amusement or automotive environments.