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Texas Instruments LM1971MX
- Part No.:
- LM1971MX
- Manufacturer:
- Texas Instruments
- Category:
- Audio Special Purpose
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM1971MX.pdf
- Description:
- IC VOLUME CONTROL 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,258
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Product details
Overview
LM1971MX from Texas Instruments is a digitally controlled single-channel audio attenuator IC with 3-wire serial interface, 62 dB attenuation range in 1 dB steps, mute function delivering 102 dB attenuation, and THD of 0.0008% - used for precision volume control in professional audio mixing and PC audio subsystems.
For engineers reviewing the LM1971MX datasheet, LM1971MX pinout, LM1971MX application, or LM1971MX equivalent, this page delivers verified circuit role (logarithmic voltage divider attenuator), package mapping (SOIC-8), pin-level design meaning, real-world application constraints (single-supply biasing at VREFIN), and two validated alternative parts for audio signal path redesign.
Technical Context
The LM1971MX implements a resistor ladder architecture with CMOS switch selection per attenuation step - not a tapped potentiometer - ensuring constant 40 kΩ input impedance but nonlinearly varying output impedance (25–35 kΩ). It operates exclusively from a unipolar 4.5–12 V supply with half-supply reference applied to VREFIN (Pin 1).
Control uses TTL/CMOS-compatible 3-wire serial interface (LOAD, CLOCK, DATA) with 16-bit frame: 8-bit address (fixed 00000000) + 8-bit attenuation/mute code. Mute is activated by any data ≥00111111 (96 dB), physically disconnecting IN from OUT and grounding OUT via ~2 kΩ.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Attenuation Range | 0 to −62 dB in 1 dB steps - enables precise digital volume control without analog trimming. |
| Mute Attenuation | 102 dB (typ) - full signal isolation achieved by internal switch disconnection and output grounding. |
| Total Harmonic Distortion | 0.0008% (typ) at 1 kHz - ensures transparent audio reproduction in high-fidelity signal chains. |
| Dynamic Range | 115 dB (typ) referenced to +6 Vpk - supports wide-swing audio signals with low noise floor. |
| Frequency Response | >200 kHz (−3 dB, typ) - preserves ultrasonic content and avoids phase distortion in mastering applications. |
| Supply Voltage Range | 4.5 V to 12 V - compatible with standard 5 V and 9 V audio system rails; requires external half-supply bias at VREFIN. |
| Input Impedance | 40 kΩ (nominal, constant) - stable loading on preceding stage regardless of attenuation setting. |
Pinout & Package
LM1971MX is housed in an 8-pin SOIC (D) package per JEDEC MS-012 variation AA, 1.75 mm max height, tape-and-reel format (2500 pcs/reel), RoHS-compliant with Sn lead finish and MSL Level-1 rating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VREFIN (1) | Analog reference input | Must be biased at VDD/2 (e.g., via resistor divider + 10 µF cap); sets DC operating point for AC-coupled audio path. |
| OUT (2) | Analog output | Attenuated signal output; requires high-Z buffer (JFET/CMOS op amp) to prevent linearity errors from output impedance variation (25–35 kΩ). |
| GND (3) | Digital/analog common ground | Single-reference node for all digital inputs (LOAD/DATA/CLOCK) and analog ground - mandates unipolar supply operation. |
| LOAD (4) | Serial data latch enable | Active-low; must go low ≥150 ns before first CLOCK rising edge and remain low during full 16-bit transfer. |
| DATA (5) | Serial data input | TTL/CMOS-compatible; accepts MSB-first 16-bit frame (8-bit address + 8-bit attenuation/mute code) on CLOCK rising edges. |
| CLOCK (6) | Serial clock input | Max 2 MHz; rising edge clocks each bit; falling edge must align with or precede LOAD falling edge (≤20 ns delay). |
| VDD (7) | Positive supply | 4.5–12 V unipolar rail; powers analog ladder and digital interface; thermal resistance θJA = 167°C/W (board mounted). |
| IN (8) | Analog input | AC-coupled audio input; constant 40 kΩ impedance; supports DC tracking when buffered appropriately. |
Key Features
| Feature | Design Value |
|---|---|
| Click- and pop-free attenuation | Guaranteed by resistor ladder architecture and synchronous digital control - eliminates audible artifacts during volume transitions. |
| Logarithmic attenuation curve | Matches human loudness perception; enables perceptually linear volume control using integer-step programming (0–62 dB). |
| Integrated mute function | Hardware-level signal kill (102 dB) via physical disconnection + output grounding - no reliance on external switches or relays. |
| Single-supply operation | Eliminates need for dual ±V rails; simplifies power design but requires precise VREFIN bias network for full dynamic range. |
| High dynamic range | 115 dB enables resolution of microvolt-level signals above noise floor - critical for studio-grade audio routing and automation. |
Applications
| Professional Audio Mixing Console | PC-Based Audio Interface |
|---|---|
|
Use Scenario: Digital control of channel faders and master bus attenuation in 24-bit/96 kHz recording systems. IC Role / Device Role / Timing Role: Logarithmic voltage divider attenuator with serial register interface - replaces mechanical potentiometers and analog switches. Use Value: Enables recallable, automated gain staging with <0.001% THD and >115 dB SNR across full 62 dB range. |
Use Scenario: Front-panel volume control and headphone output level adjustment in USB audio DACs. IC Role / Device Role / Timing Role: Digitally addressed audio attenuator interfaced to MCU via GPIO-driven 3-wire protocol. Use Value: Delivers click-free level changes and 102 dB mute isolation - meeting Windows HD Audio and Apple Core Audio compliance. |
| Cellular Handset Audio Path | Electronic Music Synthesizer |
|
Use Scenario: Ringer volume and earpiece loudness control in GSM/UMTS handsets with tight PCB space constraints. IC Role / Device Role / Timing Role: Low-power (1.8 mA typ), small-footprint (SOIC-8) attenuator with mute for call-state silencing. Use Value: Achieves >100 dB dynamic range within 4.5–5.5 V supply envelope - compatible with battery-powered RF-sensitive layouts. |
Use Scenario: CV-controlled amplitude modulation and patchable signal routing in MIDI-controllable analog synths. IC Role / Device Role / Timing Role: DC-tracking logarithmic attenuator accepting 0–5 V control voltages via microcontroller serial interface. Use Value: Supports accurate 1 dB step resolution and sub-microamp input leakage - preserving analog signal integrity in modular architectures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar digitally controlled audio attenuator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| PGA2310U | Stereo channel, I²C interface, ±15 V dual supply required, 90 dB dynamic range | Requires bipolar supply and external level-shifting for single-supply systems; higher channel count increases BOM cost | Choose PGA2310U only when stereo simultaneous control and higher headroom (>20 Vpp) are mandatory. |
| DS1669S+ | Non-volatile EEPROM storage, SPI interface, 100 kΩ pot wiper resistance, 0.1% wiper tolerance | Acts as mechanical pot replacement - lacks true mute, THD >0.01%, no guaranteed clickless operation | Use DS1669S+ only for non-critical analog trim or where power-loss retention outweighs audio fidelity requirements. |
Compared with PGA2310U and DS1669S+, the LM1971MX uniquely combines single-supply operation, guaranteed clickless 1 dB steps, 102 dB hardware mute, and 0.0008% THD - making it optimal for high-fidelity, space-constrained, unipolar audio control where signal purity and deterministic silence are design-critical.
Availability
LM1971MX is available at Aetrix Electronics and suitable for professional audio mixing consoles, PC-based USB audio interfaces, and cellular handset audio subsystems requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for LM1971MX 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
Texas Instruments is a global semiconductor company founded in 1930, specializing in analog, embedded processing, and high-performance silicon for industrial, automotive, and communications markets.
The LM1971MX belongs to TI's Overture™ audio attenuator series, engineered specifically for high-fidelity, digitally programmable gain control in professional and consumer audio equipment where low THD, wide dynamic range, and silent switching are essential.
FAQ
What is the correct biasing method for VREFIN on the LM1971MX?
VREFIN (Pin 1) must be held at exactly VDD/2 using a resistor divider (e.g., two matched 100 kΩ resistors) bypassed with a ≥10 µF capacitor to ground. Active buffering with a JFET op amp voltage follower is recommended for high-precision applications to reject supply ripple and maintain DC stability across temperature.
Does the LM1971MX support true 1 dB step resolution across its entire attenuation range?
Yes, the LM1971MX provides monotonic 1 dB steps from 0 dB to −62 dB, with absolute error ≤±0.2 dB across all settings per datasheet Electrical Characteristics table. Step size error is specified at ≤0.009 dB (typ), ensuring precise repeatability in automated audio calibration systems.
Can the LM1971MX be used with a 3.3 V microcontroller interface?
Yes - the LM1971MX digital inputs (LOAD, DATA, CLOCK) are TTL/CMOS-compatible with VIH ≥2.0 V and VIL ≤0.8 V, fully supporting direct connection to 3.3 V logic. No level-shifting is required, provided GND is shared between MCU and LM1971MX.
What is the maximum clock frequency supported by the LM1971MX serial interface?
The LM1971MX accepts CLOCK signals up to 2 MHz (max), with timing requirements specifying LOAD must go low ≥150 ns before the first rising edge and remain low throughout the 16-bit transfer. Clock duty cycle is not specified, but rising-edge sampling mandates clean signal edges.
How does the LM1971MX achieve click- and pop-free attenuation transitions?
The LM1971MX uses a resistor ladder architecture with only one CMOS switch closed per attenuation setting - eliminating charge injection and transient glitches. Combined with synchronous 16-bit serial load timing and internal zero-crossing detection logic, it guarantees artifact-free level changes even during active audio playback.
LM1971MX Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- Overture™
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Volume Control
- Applications:
- Communication Systems
- Number of Channels:
- 1
- Interface:
- SPI
- Voltage - Supply:
- 4.5V ~ 12V
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Specifications:
- 115dB
- Mounting Type:
- Surface Mount
- Grade:
- -
LM1971MX FAQ
1.How can I place an order for LM1971MX through Aetrix?
Please submit a Request for Quotation (RFQ) for LM1971MX 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 LM1971MX reliable?
The price and inventory of LM1971MX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM1971MX is usually 5 days.
3.What payment methods are accepted for LM1971MX?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM1971MX transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM1971MX?
LM1971MX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM1971MX 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 LM1971MX?
For technical support, including LM1971MX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM1971MX requirements.
6.How does Aetrix verify that LM1971MX is sourced from the original manufacturer or authorized distributors?
All LM1971MX 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 LM1971MX meets industry standards.
7.What is the process for return or replacement of LM1971MX?
All LM1971MX units undergo pre-shipment inspection (PSI). If there is an issue with LM1971MX, 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 LM1971MX part is unused and in its original packaging.
Return procedure for LM1971MX:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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