Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsLinear ICsLinear IC - Audio amplifier 2-channel (stereo) with stereo headphones Class AB HTSSOP 28

LM4938

www.ti.com

SNAS245B –FEBRUARY 2005–REVISED MAY 2013

LM4938 Boomer™ Audio Power Amplifier Series Stereo 2W Audio Power Amplifiers

with DC Volume Control and Selectable Gain

Check for Samples: LM4938

FEATURES

DESCRIPTION

The LM4938 is a monolithic integrated circuit that

• Improved Click and Pop Circuitry Virtually

provides DC volume control, and stereo bridged

Eliminates Noise During Turn On/Off

audio power amplifiers capable of producing 2W into

Transitions

4Ω with less than 1.0% THD or 2.2W into 3Ω with

• DC Volume Control Interface

less than 1.0% THD.

• System Beep Detect

Boomer audio integrated circuits were designed

• Stereo Switchable Bridged/Single-Ended

specifically to provide high quality audio while

Power Amplifiers

requiring a minimum amount of external components.

The LM4938 incorporates a DC volume control,

• Selectable Internal/External Gain and Bass

stereo bridged audio power amplifiers and a

Boost

selectable gain or bass boost, making it optimally

• Thermal Shutdown Protection Circuitry

suited for multimedia monitors, portable radios,

• Unity Gain Stable

desktop, and portable computer applications.

The LM4938 features an externally controlled, low-

APPLICATIONS

power consumption shutdown mode, and both a

power amplifier and headphone mute for maximum

• Flat Panel Displays

system flexibility and performance.

• Portable and Desktop Computers

Note 1: When properly mounted to the circuit board,

• Multimedia Monitors

LM4938MH will deliver 2W into 4Ω. See Application

• Portable Radios, PDAs, and Portable TVs

Information section HTSSOP PACKAGE PCB

MOUNTING CONSIDERATIONS for more

KEY SPECIFICATIONS

information.

• P

at 1% THD+N

Note 2: An LM4938MH that has been properly

– into 3Ω: 2.2W (typ)

mounted to the circuit board and forced-air cooled will

deliver 2.2W into 3Ω.

– into 4Ω: 2.0W (typ)

– into 8Ω: 1.3W (typ)

• Single-ended mode

– THD+N at 92mW into 32Ω: 1.0% (typ)

• Shutdown Current: 0.5µA (typ)

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2Boomer is a trademark of Texas Instruments.

3All other trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (32 pages)

PAGE 1
LM4938 www.ti.com SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 LM4938 Boomer™ Audio Power Amplifier Series Stereo 2W Audio Power Amplifiers with DC Volume Control and Selectable Gain Check for Samples: LM4938 FEATURES DESCRIPTION • The LM4938 is a monolithic integrated circuit that provides DC volume control, and stereo bridged audio power amplifiers capable of producing 2W into 4Ω with less than 1.0% THD or 2.2W into 3Ω with less than 1.0% THD.
PAGE 2
LM4938 SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 www.ti.com Block Diagram Figure 1. LM4938 Block Diagram Connection Diagram Figure 2.
PAGE 3
LM4938 www.ti.com SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings (1) (2) Supply Voltage 6.0V Storage Temperature -65°C to +150°C −0.3V to VDD +0.
PAGE 4
LM4938 SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 www.ti.com Electrical Characteristics for Entire IC (1) (2) The following specifications apply for VDD = 5V unless otherwise noted. Limits apply for TA = 25°C. Symbol VDD Parameter LM4938 Conditions Typical (3) Limit (4) Supply Voltage Units (Limits) 2.7 V (min) 5.5 V (max) mA (max) IDD Quiescent Power Supply Current VIN = 0V, IO = 0A 11 30 ISD Shutdown Current Vshutdown = VDD 0.5 2.
PAGE 5
LM4938 www.ti.com SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 Electrical Characteristics for Bridged Mode Operation (1) (2) The following specifications apply for VDD = 5V, unless otherwise noted. Limits apply for TA = 25°C. Symbol Parameter Conditions LM4938 Typical (3) Limit (4) Units (Limits) ±50 mV (max) VOS Output Offset Voltage VIN = 0V, No Load PO Output Power THD + N = 1.0%; f = 1kHz RL = 3Ω (5) 2.2 W THD + N = 1.0%; f = 1kHz RL = 4Ω (6) 2 W THD = 1% (max); f = 1kHz RL = 8Ω 1.
PAGE 6
LM4938 SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 www.ti.com Typical Application VDD VDD DC Volume Control 0.1 PF Left Gain 1 20 k: VDD RPU 100 k: To Control Pin on Headphone Jack HP Sense 100 k: 21 RS Mute 5 4 Mode CO Left Dock Audio In Left Internal gain select 3 7 19 RI Left Gain 2 20 k: RF 18 RBS 20 k: Mode Control 10 k: 10 k: CBS 0.068 PF 13 + 1 PF RIL 20 k: CV RFL 20 k: + 20 k: CIL 12 200 k: 0.33+ PF Rbeep 11 + 200 k: CIR 0.33 PF Rbeep 10 Audio + 20 k: In Right 0.
PAGE 7
LM4938 www.ti.
PAGE 8
LM4938 SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 www.ti.com Typical Performance Characteristics 8 THD+N vs Output Power VDD = 3V, RL = 4Ω, f = 1kHz THD+N vs Output Power VDD = 3V, RL = 8Ω, f = 1kHz Figure 4. Figure 5. THD+N vs Output Power VDD = 3V, RL = 32Ω, SE, f = 1kHz THD+N vs Output Power VDD = 5V, RL = 3Ω, f = 1kHz Figure 6. Figure 7. THD+N vs Output Power VDD = 5V, RL = 4Ω, f = 1kHz THD+N vs Output Power VDD = 5V, RL = 8Ω, BTL, f = 1kHz Figure 8. Figure 9.
PAGE 9
LM4938 www.ti.com SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 Typical Performance Characteristics (continued) THD+N vs Output Power VDD = 5V, RL = 32Ω, SE, f = 1kHz THD+N vs Frequency VDD = 5V, RL = 8Ω, PO = 1W, BTL Figure 10. Figure 11. THD+N vs Frequency VDD = 3V, RL = 4Ω, PO = 170mW THD+N vs Frequency VDD = 3V, RL = 8Ω, PO = 160mW Figure 12. Figure 13. THD+N vs Frequency VDD = 3V, RL = 32Ω, PO = 20mW, SE THD+N vs Frequency VDD = 5V, RL = 3Ω, PO = 600mW Figure 14. Figure 15.
PAGE 10
LM4938 SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 www.ti.com Typical Performance Characteristics (continued) 10 THD+N vs Frequency VDD = 5V, RL = 4Ω, PO = 600mW THD+N vs Frequency VDD = 5V, RL = 32Ω, PO = 70mW, SE Figure 16. Figure 17. Frequency Response VDD = 3V, RL = 4Ω, PO = 1.8W Frequency Response VDD = 3V, RL = 8Ω, PO = 570mW Figure 18. Figure 19. Frequency Response VDD = 3V, RL = 32Ω, PO = 30mW, SE Frequency Response VDD = 5V, RL = 3Ω, PO = 1.8W Figure 20. Figure 21.
PAGE 11
LM4938 www.ti.com SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 Typical Performance Characteristics (continued) Frequency Response VDD = 5V, RL = 4Ω, PO = 1.5W Frequency Response VDD = 5V, RL = 8Ω, PO = 1W Figure 22. Figure 23. Frequency Response VDD = 5V, RL = 32Ω, PO = 30mW, SE PSRR vs Frequency VDD = 3V, RL = 8Ω, Terminated 0.0 -10 -20 PSRR LEVEL (dB) -30 -40 -50 -60 -70 -80 -90 -100 20 100 1k 10k 20k FREQUENCY (Hz) Figure 24. PSRR vs Frequency VDD = 3V, RL = 8Ω, Unterminated 0.
PAGE 12
LM4938 SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 www.ti.com Typical Performance Characteristics (continued) PSRR vs Frequency VDD = 3V, RL = 32Ω, Unterminated PSRR vs Frequency VDD = 5V, RL = 8Ω, Terminated 0 -10 -10 -20 -20 -30 -30 PSRR LEVEL (dB) PSRR LEVEL (dB) 0.0 -40 -50 -60 -70 -40 -50 -60 -70 -80 -80 -90 -90 -100 20 100 1k -100 10k 20k 20 100 FREQUENCY (Hz) Figure 29. PSRR vs Frequency VDD = 5V, RL = 8Ω, Unterminated 0.
PAGE 13
LM4938 www.ti.com SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 Typical Performance Characteristics (continued) -10 -10 -20 -20 -30 -40 -50 -60 -70 -80 -30 -40 -50 -60 -70 -80 -90 -90 -100 -100 20 0.0 100 1k 10k 20k 20 100 1k 10k 20k FREQUENCY (Hz) FREQUENCY (Hz) Figure 34. Figure 35. Crosstalk vs Frequency VDD = 5V, RL = 32Ω, PO = 30mW, SE Volume Control Characteristics 10 0.
PAGE 14
LM4938 SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 www.ti.com Typical Performance Characteristics (continued) (1) 14 Power Derating Curve (1) Dropout Voltage Figure 38. Figure 39. Power Dissipation vs Output Power External Gain/ Bass Boost Characteristics Figure 40. Figure 41. Power Dissipation vs Output Power Power Dissipation vs Output Power Figure 42. Figure 43.
PAGE 15
LM4938 www.ti.com SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 Typical Performance Characteristics (continued) Output Power vs Supply Voltage Figure 44.
PAGE 16
LM4938 SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 www.ti.com APPLICATION INFORMATION HTSSOP PACKAGE PCB MOUNTING CONSIDERATIONS The LM4938's HTSSOP (die attach paddle) package (MH) provides a low thermal resistance between the die and the PCB to which the part is mounted and soldered. This allows rapid heat transfer from the die to the surrounding PCB copper traces, ground plane and, finally, surrounding air. The result is a low voltage audio power amplifier that produces 2.0W at ≤ 1% THD with a 4Ω load.
PAGE 17
LM4938 www.ti.com SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 Bridge mode amplifiers are different from single-ended amplifiers that drive loads connected between a single amplifier's output and ground. For a given supply voltage, bridge mode has a distinct advantage over the singleended configuration: its differential output doubles the voltage swing across the load. This produces four times the output power when compared to a single-ended amplifier under the same conditions.
PAGE 18
LM4938 SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 www.ti.com POWER SUPPLY BYPASSING As with any power amplifier, proper supply bypassing is critical for low noise performance and high power supply rejection. Applications that employ a 5V regulator typically use a 10 µF in parallel with a 0.1 µF filter capacitor to stabilize the regulator's output, reduce noise on the supply line, and improve the supply's transient response. However, their presence does not eliminate the need for a local 1.
PAGE 19
LM4938 www.ti.com SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 unity until the voltage on the BYPASS pin reaches 1/2 VDD . As soon as the voltage on the BYPASS pin is stable, the device becomes fully operational. Although the BYPASS pin current cannot be modified, changing the size of CB alters the device's turn-on time and the magnitude of “clicks and pops”. Increasing the value of CB reduces the magnitude of turn-on pops.
PAGE 20
LM4938 SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 www.ti.com There are a few ways to control the micro-power shutdown. These include using a single-pole, single-throw switch, a microprocessor, or a microcontroller. When using a switch, connect an external 10kΩ pull-up resistor between the SHUTDOWN pin and VDD. Connect the switch between the SHUTDOWN pin and ground. Select normal amplifier operation by closing the switch.
PAGE 21
LM4938 www.ti.com SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 The HP-IN threshold is set at 4V. While the LM4938 operates in bridged mode, the DC potential across the load is essentially 0V. Therefore, even in an ideal situation, the output swing cannot cause a false single-ended trigger. Connecting headphones to the headphone jack disconnects the headphone jack contact pin from R2 and allows R1 to pull the HP Sense pin up to VDD through R4.
PAGE 22
LM4938 SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 www.ti.com DC VOLUME CONTROL The LM4938 has an internal stereo volume control whose setting is a function of the DC voltage applied to the DC VOL CONTROL pin. The LM4938 volume control consists of 31 steps that are individually selected by a variable DC voltage level on the volume control pin. The range of the steps, controlled by the DC voltage, are from 0dB - 89dB.
PAGE 23
LM4938 www.ti.com SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 AUDIO POWER AMPLIFIER DESIGN Audio Amplifier Design: Driving 1W into an 8Ω Load The following are the desired operational parameters: Power Output: 1 WRMS Load Impedance: 8Ω Input Level: 1 VRMS Input Impedance: 20 kΩ Bandwidth: 100 Hz−20 kHz ± 0.25 dB The design begins by specifying the minimum supply voltage necessary to obtain the specified output power.
PAGE 24
LM4938 SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 www.ti.com Recommended Printed Circuit Board Layout The following figures show the recommended PC board layouts for the LM4938MH. This circuit is designed for use with an external 5V supply and 4Ω speakers. This circuit board is easy to use. Apply 5V and ground to the board's VDD and GND pads, respectively. Connect 4Ω speakers between the board's −OUTA and +OUTA and OUTB and +OUTB pads. Figure 47. Top Layer Silkscreen Figure 48.
PAGE 25
LM4938 www.ti.com SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 Figure 49. Inner Layer (2) Figure 50.
PAGE 26
LM4938 SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 www.ti.com Figure 51.
PAGE 27
LM4938 www.ti.com SNAS245B – FEBRUARY 2005 – REVISED MAY 2013 Analog Audio LM4938 TSSOP Eval Board Assembly Part Number: 980011373-100 Revision: A Bill of Material Item Part Number Part Description Qty 1 551011373-001 LM4938 Eval Board PCB etch 001 1 Ref Designator Remark 10 482911373-001 LM4938 TSSOP 1 20 151911368-001 Cer Cap 0.068µF 50V 10% 1206 2 CBS 25 152911368-001 Tant Cap 0.1µF 10V 10% Size = A 3216 3 CS, CS, CV 26 152911368-002 Tant Cap 0.
PAGE 28
PACKAGE OPTION ADDENDUM www.ti.
PAGE 29
PACKAGE MATERIALS INFORMATION www.ti.com 8-May-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device LM4938MHX/NOPB Package Package Pins Type Drawing SPQ HTSSOP 2500 PWP 28 Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 330.0 16.4 Pack Materials-Page 1 6.8 B0 (mm) K0 (mm) P1 (mm) 10.2 1.6 8.0 W Pin1 (mm) Quadrant 16.
PAGE 30
PACKAGE MATERIALS INFORMATION www.ti.com 8-May-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM4938MHX/NOPB HTSSOP PWP 28 2500 367.0 367.0 35.
PAGE 31
MECHANICAL DATA PWP0028A MXA28A (Rev D) www.ti.
PAGE 32
IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.