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

STMicroelectronics TS421IQT

Name: TS421IQT
Brand: STMicroelectronics
SKU: TS421IQT
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: TS421IQT

Manufacturer:: STMicroelectronics

Category:: Audio Amplifiers

Package:: 8-VFDFN Exposed Pad

Datasheet:: TS421IQT.pdf

Description:: IC AMP CLASS AB MONO 367MW 8DFN

Quantity:: RFQ Add To RFQ list

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Inventory:3,000

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Product details

Overview

TS421IQT from STMicroelectronics is a monaural Class-AB audio power amplifier in DFN8 package, operating from 2 V to 5.5 V supply, delivering up to 367 mW into 16 Ω at 10% THD+N (5 V), with standby current as low as 10 nA and SNR of 95 dB(A). It drives earpiece/receiver speakers in BTL mode-eliminating output coupling capacitors-and targets space-constrained portable voice interfaces.

For engineers reviewing the TS421IQT datasheet, TS421IQT pinout, TS421IQT application, or TS421IQT equivalent, this page delivers verified electrical specs, validated DFN8 pin mapping, real-world BTL earpiece drive capability, and direct alternatives for low-voltage mono audio amplification in mobile handsets and PDAs.

Technical Context

The TS421IQT implements a bridge-tied load (BTL) output stage with externally configurable gain via R_IN/R_FEED, enabling closed-loop gain adjustment (A_V = 2 × R_FEED/R_IN). Its standby control is active-low, distinguishing it from the TS419 (active-high), and integrates ON/OFF click suppression and short-circuit current limiting.

It operates across –40 °C to +85 °C with thermal resistance R_thJA = 41 °C/W on 4-layer PCBs, supports 16–64 Ω loads, and maintains stable phase margin (58°) and gain margin (18 dB) into 16 Ω with 400 pF capacitive load-ensuring robust audio bandwidth up to 125 kHz.

Key Specifications

Parameter	Value and Actual Design Meaning
Supply Voltage Range	2 V to 5.5 V - enables operation from single Li-ion cell (2.5–4.2 V) or regulated 3.3 V/5 V rails without LDO overhead.
Output Power (16 Ω)	295 mW @ 5 V, 1% THD+N - sufficient for loud, clear earpiece audio in mobile handsets with minimal distortion.
Standby Current	10 nA typ. - extends battery life in always-on voice interface modes (e.g., wake-word detection).
Signal-to-Noise Ratio	95 dB(A) @ 5 V - ensures high-fidelity audio reproduction with negligible background hiss in quiet environments.
PSRR	56 dB @ 1 kHz - rejects ripple from noisy DC-DC converters, critical in compact portable designs sharing power rails.
THD+N	0.2% max @ 220 mW, 16 Ω - meets stringent voice clarity requirements for telephony-grade earpiece output.
Gain Bandwidth Product	1.1 MHz - supports full audio bandwidth (20 Hz–20 kHz) with stable closed-loop response and low group delay.

Pinout & Package

TS421IQT uses a thermally enhanced 3×3 mm DFN8 package (0.5 mm pitch) with exposed thermal pad (EP) connected to GND for optimal heat dissipation in handheld devices.

Pin/Terminal	Circuit Role	Design Meaning
1 - Standby	Digital enable input	Active-low control: logic low (≤0.4 V) enters ultra-low-power standby (10 nA); logic high (≥1.5 V) enables operation.
2 - Bypass	Half-supply reference filter node	Connects to 1 µF capacitor to GND to stabilize internal virtual ground-critical for BTL offset control and click reduction.
3 - V+	Positive supply rail	Accepts 2–5.5 V; requires local 100 nF ceramic bypass capacitor to minimize supply impedance and PSRR degradation.
4 - IN	Inverting input	Configures closed-loop gain with R_FEED; forms high-pass filter with C_IN (f_CL = 1/(2π·R_IN·C_IN)).
5 - VIN−	Non-inverting input	Typically tied to bypass voltage (V_BYP) to set common-mode input level for BTL symmetry.
6 - VOUT2	Second BTL output	Drives one side of speaker load; complements VOUT1 to deliver differential swing without output capacitor.
7 - GND	Power and signal reference	Must be low-impedance connection; thermal pad (EP) is electrically and thermally tied to this pin.
8 - VOUT1	First BTL output	Drives opposite side of speaker load; 180° out-of-phase with VOUT2 to double effective voltage swing across load.

Key Features

Feature	Design Value
Bridge-Tied Load (BTL) Output	Eliminates bulky DC-blocking output capacitors-reducing PCB area and cost while enabling true 0-V DC bias across speaker.
Ultra-Low Standby Current	10 nA typical allows integration into battery-powered devices with multi-week standby without measurable drain.
Click-and-Pop Suppression	Integrated circuitry minimizes audible transients during power-up/down and standby transitions-critical for user-facing earpieces.
Wide Supply Range Support	Operates down to 2 V-enables direct use with partially discharged Li-ion cells (2.5–4.2 V) without voltage regulation.
Thermal Protection	Short-circuit current limiting and thermal shutdown prevent damage during fault conditions; R_thJA = 41 °C/W enables 1.79 W dissipation on 4-layer board.

Applications

Mobile Handset Earpiece

VoIP Desk Phone Receiver

Use Scenario: Driving 16 Ω ceramic earpiece in slim smartphone bezel with limited board space and no room for output caps.

IC Role / Device Role / Timing Role: Monaural BTL audio amplifier providing differential 3.5 V_PP swing into 16 Ω load at 5 V supply.

Use Value: Capacitor-free output saves >2 mm² PCB area and eliminates cap aging-related audio drift over product lifetime.

Use Scenario: Amplifying ring-tone or call audio in SIP-based desk phones powered by PoE-derived 3.3 V rail.

IC Role / Device Role / Timing Role: Low-noise mono amplifier delivering 113 mW @ 1% THD+N into 16 Ω at 3.3 V supply.

Use Value: 94 dB SNR and 56 dB PSRR ensure clean audio even when sharing noisy PoE power supply with Ethernet PHY.

PDA Audio Feedback

Industrial Handheld Terminal

Use Scenario: Providing audible keypad feedback and alert tones in legacy PDA with 2.5 V main rail and tight thermal budget.

IC Role / Device Role / Timing Role: Standby-enabled audio driver delivering 55 mW @ 1% THD+N into 16 Ω at 2.5 V.

Use Value: 10 nA standby current preserves battery charge during long idle periods between user interactions.

Use Scenario: Driving ruggedized 32 Ω receiver in warehouse handheld scanner operating at –20 °C to +70 °C ambient.

IC Role / Device Role / Timing Role: Wide-temp audio amplifier supporting 166 mW @ 1% THD+N into 32 Ω at 5 V across full industrial range.

Use Value: Guaranteed operation from –40 °C to +85 °C and short-circuit protection ensure reliability in harsh drop-test environments.

Equivalent & Alternatives

The following parts are listed as comparable options for similar mono BTL audio amplifier applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
MAX98357AETE+T	I²S digital input; fixed 12 dB gain; no analog input pins or external gain resistors.	Requires digital audio source (SoC I²S); unsuitable for analog line-in or microphone preamp outputs.	Select when system uses digital audio path and needs simplified layout-avoid if analog signal chain is required.
TAS5707PAG	Class-D architecture; higher efficiency (>85% at 1 W); requires external LC filter; larger QFN32 package.	Better suited for battery-powered speakers needing >500 mW; less ideal for earpiece due to EMI sensitivity and filter footprint.	Prefer for portable speakers or docking stations where efficiency > size; avoid for space-constrained earpiece PCBs.

Compared with MAX98357A and TAS5707, TS421IQT offers analog-input flexibility, capacitor-less BTL output, and smallest footprint (3×3 mm DFN8), making it optimal for ultra-compact voice interface modules where analog signal integrity and board area are primary constraints.

Availability

TS421IQT is available at Aetrix Electronics and suitable for mobile handset earpiece drivers, VoIP receiver modules, and industrial handheld terminals requiring stable component supply and guaranteed long-term manufacturability.

Supply support for TS421IQT 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, designing and manufacturing analog, MCU, power, and sensor solutions for automotive, industrial, and consumer markets.

The TS421 belongs to ST's low-voltage audio amplifier product line, engineered specifically for capacitor-free BTL earpiece drive in space- and power-constrained portable voice interfaces.

FAQ

What is the minimum recommended bypass capacitor value for the TS421IQT's VCC pin?

A 100 nF X7R ceramic capacitor placed as close as possible to the VCC pin (Pin 3) is mandatory for stable operation. This capacitor suppresses high-frequency supply noise and prevents oscillation under dynamic load conditions. Larger bulk capacitance (e.g., 1–10 µF) may be added in parallel for improved low-frequency PSRR, but the 100 nF local decoupling is non-negotiable per ST's layout guidelines.

Can the TS421IQT drive a 8 Ω speaker load?

No-TS421IQT is specified only for ≥16 Ω loads per datasheet Table 2. Driving 8 Ω risks excessive current draw, thermal overload, and violation of absolute maximum ratings (output short-circuit current limit applies). For 8 Ω applications, ST recommends TS420 or TS422 variants, which are rated for lower impedances and higher output current.

How does the standby wake-up time affect system responsiveness?

Wake-up time from standby to full audio output is ≥120 ms (with 1 µF bypass capacitor), as defined in Table 2. This delay occurs because the internal virtual ground must stabilize before output stage biasing completes. For applications requiring sub-50 ms voice activation (e.g., wake-word detection), the device must remain in active mode with ICC ≤ 2.5 mA at 3.3 V to avoid perceptible latency.

Is the thermal pad (EP) on the DFN8 package electrically connected?

Yes-the exposed thermal pad (EP) is internally connected to GND (Pin 7) and must be soldered to a dedicated GND copper pour on the PCB. This connection provides both thermal conduction (reducing R_thJA from 70 °C/W to 41 °C/W) and electrical grounding for noise immunity. Floating or unconnected EP degrades thermal performance and may cause instability or premature thermal shutdown.

TS421IQT Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 8-VFDFN Exposed Pad

Packaging:: Tape & Reel (TR)

Product Status:: Active

Type:: Class AB

Output Type:: 1-Channel (Mono)

Max Output Power x Channels @ Load:: 367mW x 1 @ 16Ohm

Voltage - Supply:: 2V ~ 5.5V

Features:: Differential Inputs, Short-Circuit Protection, Standby

Mounting Type:: Surface Mount

Operating Temperature:: -40°C ~ 85°C (TA)

Grade:: -

Qualification:: -

Supplier Device Package:: 8-DFN (3x3)

TS421IQT FAQ

1.How can I place an order for TS421IQT through Aetrix?

Please submit a Request for Quotation (RFQ) for TS421IQT 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 TS421IQT reliable?

The price and inventory of TS421IQT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for TS421IQT is usually 5 days.

3.What payment methods are accepted for TS421IQT?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for TS421IQT transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for TS421IQT?

TS421IQT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your TS421IQT 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 TS421IQT?

For technical support, including TS421IQT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your TS421IQT requirements.

6.How does Aetrix verify that TS421IQT is sourced from the original manufacturer or authorized distributors?

All TS421IQT 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 TS421IQT meets industry standards.

7.What is the process for return or replacement of TS421IQT?

All TS421IQT units undergo pre-shipment inspection (PSI). If there is an issue with TS421IQT, 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 TS421IQT part is unused and in its original packaging.

Return procedure for TS421IQT:

1.Submit a request within 90 days.

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

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