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Home > Products > Integrated Circuits (ICs) > Linear > Audio Amplifiers

STMicroelectronics FDA903U-KBX

Name: FDA903U-KBX
Brand: STMicroelectronics
SKU: FDA903U-KBX
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: FDA903U-KBX

Manufacturer:: STMicroelectronics

Category:: Audio Amplifiers

Package:: 36-PowerFSOP (0.295", 7.50mm Width)

Datasheet:: FDA903U-KBX.pdf

Description:: 1 X 45 W CLASS D DIGITAL INPUT A

Quantity:: RFQ Add To RFQ list

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Inventory:3,717

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Product details

Overview

FDA903U-KBX from STMicroelectronics is a single-channel, 45 W Class D automotive audio power amplifier with integrated 108 dB D/A conversion, I²S/TDM digital input (up to 16-channel), and real-time I_LOAD current monitoring. It operates from 3.3 V to 18 V, delivers 30 W into 4 Ω at 14.4 V (THD = 10%), supports 2 Ω loads, and meets CISPR 25 Class V EMI requirements for in-dash car radio integration.

For engineers reviewing the FDA903U-KBX datasheet, FDA903U-KBX pinout, FDA903U-KBX application, or FDA903U-KBX equivalent, this device is selected for high-efficiency, diagnostics-rich, AEC-Q100 qualified amplification in telematics, e-call, and noise/tone generator systems where supply voltage resilience, play-mode fault detection, and thermal robustness are critical.

Technical Context

The FDA903U employs BCD process technology to integrate high-fidelity 108 dB DAC, MOSFET power stage, and closed-loop feedback incorporating the external L-C low-pass filter-enabling superior frequency response linearity and <0.02% THD+N at 1 W. Its architecture supports both I²C-configurable operation and legacy 'no-I²C' mode with four preset settings.

Diagnostics include short-to-VCC/GND, open-load detection *during playback*, DC offset sensing (input/output/current), clipping, thermal warnings (four levels), and watchdog/error frame checking-all accessible via I²C registers. Power limiting, AM mode, dither PWM, and noise gating are implemented in hardware for deterministic automotive behavior.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Power	30 W @ 4 Ω, 14.4 V, 1 kHz, THD = 10% - enables full-range mid-bass driver support in compact automotive enclosures
Supply Range	3.3 V to 18 V - supports emergency battery (3.3 V), cold-crank (5.5 V), and load-dump (18 V) without external regulation
DAC Resolution	108 dB SNR - achieves studio-grade dynamic range for high-fidelity cabin audio reproduction
Digital Input	I²S + TDM (4/8/16 CH), 44.1–192 kHz sampling - compatible with modern SoC audio processors and multi-zone telematics head units
EMI Compliance	CISPR 25 Class V (4th ed.) - certified for direct placement in single-DIN radio chassis alongside tuner modules
Diagnostic Coverage	Open-load & DC offset detection active during playback - eliminates silent failure modes in safety-critical e-call and alert tone generation
Thermal Protection	Integrated thermal shutdown with four warning thresholds - enables predictive derating and system-level thermal management

Pinout & Package

Package: PowerSSO-36 (exposed pad up), thermally optimized for automotive PCB mounting with high-power dissipation capability (R_thJA = 27 °C/W typical).

Pin/Terminal	Circuit Role	Design Meaning
V_CC	Primary power supply input	Accepts 3.3–18 V; powers internal logic, DAC, and gate drivers - designed for direct connection to vehicle battery rail
V_OUT	Differential output terminal	Class D PWM output driving speaker via external LC filter; supports 2 Ω minimum load impedance
I_SENSE	Current sense monitor output	Analog voltage proportional to load current (10 mV/A); enables real-time I_LOAD monitoring without shunt resistor
SD	Shutdown control input	Active-low logic input; places device in ultra-low quiescent current state (<10 µA) for system sleep mode compliance
FAULT	Open-drain diagnostic flag	Asserts low on thermal warning, open load, short circuit, or I²C communication error - directly interfaces with MCU GPIO
SCL/SDA	I²C interface pins	Support 1.8 V / 3.3 V logic levels; enable full register access for configuration, diagnostics readback, and power limiting setup

Key Features

Feature	Design Value
Play-mode open-load detection	Identifies disconnected speakers while audio is playing, preventing undetected mute conditions in safety-critical e-call alerts
Integrated L-C filter feedback	Includes output LC filter in control loop - improves phase margin and reduces THD by >50% vs. conventional Class D topologies
Configurable power limiter	I²C-adjustable RMS/peak limit threshold - prevents thermal runaway during sustained bass transients in confined enclosures
Legacy mode (no-I²C)	Four factory-set configurations selectable via hardware pins - enables drop-in replacement in legacy designs without firmware changes
Real-time I_LOAD monitoring	On-chip current sensing with <±5% accuracy across 0.1–3 A - replaces external shunt + op-amp, saving board space and BOM cost

Applications

Car Radio Audio Amplification

Telematics Voice Output

Use Scenario: Integrated amplifier in single-DIN automotive head unit driving front-channel speakers.

IC Role / Device Role / Timing Role: Primary Class D power stage with embedded DAC and EMI-hardened layout for co-location with FM/AM tuner.

Use Value: Eliminates external DAC and discrete power stage, reducing component count by 7+ parts while meeting CISPR 25 Class V radiated emissions limits.

Use Scenario: Voice prompt and navigation feedback in connected infotainment systems.

IC Role / Device Role / Timing Role: Low-latency, diagnostics-enabled audio output for time-critical voice synthesis with fail-safe detection.

Use Value: Play-mode open-load and DC offset detection ensures audible alerts remain functional even after speaker wire disconnection during vehicle service.

e-Call Emergency Tone Generator

Noise & Tone Generation (ADAS)

Use Scenario: High-reliability audio source for automated emergency call (e-Call) acoustic signaling.

IC Role / Device Role / Timing Role: AEC-Q100 qualified Class D amplifier with thermal warning and watchdog - guarantees tone generation under battery brownout or overheating.

Use Value: Integrated thermal protection and fault reporting via FAULT pin enable automatic system-level fallback to backup tone generator if primary fails.

Use Scenario: Active noise cancellation (ANC) and lane departure warning (LDW) tone generation in ADAS ECUs.

IC Role / Device Role / Timing Role: Precision timing-capable amplifier with configurable power limiting and AM mode for narrowband tone synthesis.

Use Value: AM operation mode enables clean 1–5 kHz tone generation without PWM carrier artifacts, critical for human-perceptible warning clarity.

Equivalent & Alternatives

The following parts are listed as comparable options for similar Class D automotive amplifier applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
TAS6424LQDKRQ1	4-channel, higher channel count; 42 W/ch into 4 Ω; no integrated DAC; requires external I²S-to-analog conversion	Better suited for multi-zone audio systems; lacks FDA903U's play-mode diagnostics and 2 Ω drive capability	Select when scaling to 4-speaker layouts and external DAC is already present in design
MAX9877EPL+	Single-channel, 25 W into 4 Ω; analog input only; no digital interface; lower integration (no DAC, no current sense)	Targeted at cost-sensitive analog-source radios; missing FDA903U's I²S/TDM support, diagnostics, and wide supply range	Select only for legacy analog designs where digital input and advanced diagnostics are unnecessary

Compared with TAS6424LQDKRQ1 and MAX9877EPL+, the FDA903U-KBX uniquely combines single-channel high-power density, integrated DAC, play-mode diagnostics, and 3.3–18 V operation-making it optimal for compact, future-proof automotive audio nodes requiring minimal external components and maximum functional safety coverage.

Availability

FDA903U-KBX is available at Aetrix Electronics and suitable for car radio, telematics, and e-call systems requiring stable component supply, AEC-Q100 qualification, and long-term automotive lifecycle support.

Supply support for FDA903U-KBX 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in automotive, industrial, and power management ICs with broad manufacturing scale and AEC-Q100 validation infrastructure.

The FDA903U belongs to ST's automotive audio power amplifier product line, engineered specifically for high-efficiency, diagnostics-rich, EMI-compliant amplification in space-constrained in-vehicle infotainment and safety-critical alert systems.

FAQ

What is the minimum operating voltage for FDA903U-KBX, and how does it behave below 5.5 V?

The FDA903U-KBX operates down to 3.3 V, enabling functionality during deep battery discharge or emergency power scenarios. Below 5.5 V, it maintains full audio performance and diagnostics but enters reduced-power states per its finite state machine-ensuring continued operation in cold-crank conditions without reset or dropout.

Does FDA903U-KBX require an external LC filter, and what are the design constraints?

Yes-an external LC low-pass filter is mandatory between V_OUT and speaker. The FDA903U's feedback loop includes this filter, so component values directly impact stability and THD. ST recommends 10 µH inductors and 220 nF film capacitors for 4 Ω loads; layout must minimize parasitic inductance to meet CISPR 25 Class V.

How does the I_LOAD current monitoring function, and what is its accuracy?

I_SENSE provides an analog voltage (10 mV/A) proportional to output current, calibrated over temperature and supply voltage. Accuracy is ±5% from 0.1 A to 3 A at 25 °C, with monotonic response up to 5 A peak. It requires no external calibration and feeds directly into MCU ADC for real-time load analysis.

Can FDA903U-KBX operate without I²C, and what features remain functional?

Yes-in Legacy Mode, configured via hardware pins, the FDA903U-KBX operates with four fixed settings (gain, mute, power limit, thermal threshold). All analog functions (amplification, thermal shutdown, FAULT flag) remain active, but diagnostics reporting, fine-grained configuration, and play-mode open-load detection are disabled.

FDA903U-KBX Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 36-PowerFSOP (0.295", 7.50mm Width)

Packaging:: Tube

Product Status:: Active

Type:: Class D

Output Type:: 1-Channel (Mono)

Max Output Power x Channels @ Load:: 45W x 1 @ 2Ohm

Voltage - Supply:: 3.3V ~ 18V

Features:: -

Mounting Type:: Surface Mount

Operating Temperature:: -40°C ~ 125°C (TA)

Grade:: Automotive

Qualification:: AEC-Q100

Supplier Device Package:: PowerSSO-36 EPU

FDA903U-KBX FAQ

1.How can I place an order for FDA903U-KBX through Aetrix?

Please submit a Request for Quotation (RFQ) for FDA903U-KBX on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for FDA903U-KBX reliable?

The price and inventory of FDA903U-KBX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for FDA903U-KBX is usually 5 days.

3.What payment methods are accepted for FDA903U-KBX?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for FDA903U-KBX transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for FDA903U-KBX?

FDA903U-KBX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your FDA903U-KBX order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for FDA903U-KBX?

For technical support, including FDA903U-KBX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your FDA903U-KBX requirements.

6.How does Aetrix verify that FDA903U-KBX is sourced from the original manufacturer or authorized distributors?

All FDA903U-KBX products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that FDA903U-KBX meets industry standards.

7.What is the process for return or replacement of FDA903U-KBX?

All FDA903U-KBX units undergo pre-shipment inspection (PSI). If there is an issue with FDA903U-KBX, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The FDA903U-KBX part is unused and in its original packaging.

Return procedure for FDA903U-KBX:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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