Texas Instruments LME49720NABD Manuale utente

User's Guide

SNAA052A–February 2008–Revised May 2013

AN-1768 LME49600 Headphone Amplifier

Evaluation Board

1 Quick Start Guide

1. Apply a ±2.5V to ±17V power supply’s voltage to the respective “V+”, “GND” and “V–” pins on JU19.

2. Apply a stereo audio signal to the RCA jacks J1 (Right) and J2 (Left) or jumpers JU1 (Right) and JU17

(Left), observing the signal input pin and the ground (GND) pin. Though not typically installed, a stereo

signal can also be applied to headphone jack HPJ1.

3. Connect a load to JU14 (Left) and another load to JU15 (Right), observing the signal output pin and

the ground (GND) pin. The stereo signal output is also available on the 1/8” stereo headphone jack

located in the board's “OUTPUT” section.

4. Use VR1 to control the output signal amplitude.

5. Apply power. Make measurements. Plug in a pair of headphones. Enjoy.

2 Introduction

To help the user investigate and evaluate the LME49600's performance and capabilities, a fully populated

demonstration board was created. Please click here for availability. This board is shown in Figure 1.

Connected to an external power supply (±2.5V to ±17V) and a signal source. The LME49600

demonstration board easily demonstrates the amplifier's features.

All trademarks are the property of their respective owners.

SNAA052A–February 2008–Revised May 2013 AN-1768 LME49600 Headphone Amplifier Evaluation Board

General Description

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Figure 1. LME49600/LME49720 Stereo Headphone Amplifier Demonstration Board

3 General Description

The LME49600 is a high performance, low distortion high fidelity 250mA audio buffer. Whereas there are

many uses for the LME49600, this application report describes a headphone amplifier circuit and

associated demonstration board. Designed for use inside an operational amplifier’s feedback loop, it

increases output current, improves capacitive load drive, and eliminates thermal feedback.

The LME49600 offers a pin-selectable bandwidth: a low current, 110MHz bandwidth mode that consumes

8mA and a wide 180MHz bandwidth mode that consumes 15mA. In both modes the LME49600 has a

nominal 2000V/μs slew rate. Bandwidth is easily adjusted by either leaving the BW pin unconnected,

connecting a resistor between the BW pin and the VEE pin or connecting the BW pin directly to the VEE pin.

The LME49600 is fully protected through internal current limit and thermal shutdown.

4 Operating Conditions

Temperature Range –40°C ≤TA≤85°C

Amplifier Power

Supply Voltage 2.5V ≤VS±17V

2AN-1768 LME49600 Headphone Amplifier Evaluation Board SNAA052A–February 2008–Revised May 2013

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+U4

LME49600

4.7 PF

C22

0.1 PF

V-

C10

4.7 PF

C21

0.1 PF

V+

+U2-A

1.0 PF

V-

1.0 PF

V+

-U2-B

1.0 PF

R11

R12

VR1-B

JU4

+U3

LME49600

C23

4.7 PF

C20

0.1 PF

V-

C24

4.7 PF

C19

0.1 PF

V+

+U1-A

See note

1.0 PF

V-

1.0 PF

V+

-U1-B

1.0 PF

R10

VR1-A

JU6

JU17

JU1

JU15

JU14 1

3HPJ2

HPJ1

1J2

1J1

2S1-A 1

5S1-B 4

V-

BAT2

BAT1

V+

C14

22 PF

C12

22 PF

V-

V+

JU19

See note

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Board Features

5 Board Features

The LME49600/LME49720 Stereo Headphone Amplifier demonstration board has all of the necessary

connections, using RCA jacks, 1/8” stereo headphone jack and 0.100” headers, to apply the power supply

voltage and the audio input signals. The amplified audio signal is available on both a stereo headphone

jack and auxiliary output connections.

Also present on the demonstration board is a potentiometer to control the stereo output signal magnitude.

6 Schematic

Figure 2 shows the LME49600/LME49720 Stereo Headphone Amplifier Demonstration Board schematic.

Table 1 is a list of the connections and their functions.

Figure 2. LME49600 Demonstration Board Schematic

Note: The LM4562, LME49720, or LME49860 can be used.

SNAA052A–February 2008–Revised May 2013 AN-1768 LME49600 Headphone Amplifier Evaluation Board

Connections

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7 Connections

Connecting to the world is accomplished through a combination of RCA jacks, 1/8” stereo headphone

jacks and 0.100” headers on the LME49600 demonstration board. The functions of the different headers,

1/8” headphone jacks and RCA jacks are detailed in Table 1.

Table 1. LME49600 Demonstration Board Connections

Designator Function or Use

JU17 This is the connection to the amplifier’s left channel input. Apply an external signal source’s positive

voltage to the JU17 pin labeled “LT IN” and the signal source’s ground signal to the pin labeled “GND.”

J2 This is an RCA connector that parallels the pins on JU17.

HPJ1 Stereo, 1/8” headphone jack. Used for stereo signal input. Left channel input is on the tip connector and

the right channel input is on the ring connector. Ground is on the sleeve connector.

J1 This is an RCA connector that parallels the pins on JU1.

JU1 This is the connection to the amplifier’s right channel input. Apply an external signal source’s positive

voltage to the JU1 pin labeled “RT IN” and the signal source’s ground signal to the pin labeled “GND.”

JU19 Power supply connection. Connect an external split power supply’s voltage source ±2.5V to ±17V to the

JU19 pin labeled (“V+” and “V-”)” and the supply’s ground source to the pin labeled “GND.”

JU14 This is the connection to the amplifier’s single-ended, ground-referenced left channel output. Connect

the JU14 pin labeled “LT OUT” and the pin labeled “GND” to the positive and ground inputs,

respectively, of an external signal measurement device. JU14’s pin labeled “LT OUT” corresponds to the

headphone jack’s “tip” connection. J5’s pin labeled “GND“ corresponds to the headphone jack’s “sleeve”

(or ground) connection.

HPJ2 Stereo, 1/8” headphone jack. Used for stereo signal output. Left channel output is on the tip connector

and the right channel output is on the ring connector. Ground is on the sleeve connector.

JU15 This is the connection to the amplifier’s ground-referenced right channel output. Connect the JU15 pin

labeled “RT OUT” and the pin labeled “GND” to the positive and ground inputs, respectively, of an

external signal measurement device. JU15’s pin labeled “RT OUT” corresponds to the headphone jack’s

“ring” connection. J4’s pin labeled “GND“ corresponds to the headphone jack’s “sleeve” (or ground)

connection.

JU4, JU6 These connections allow monitoring the left and right channel DC servo outputs, respectively.

8 PCB Layout Guidelines

This section provides general practical guidelines for PCB layouts that use various power and ground

traces. Designers should note that these are only "rule-of-thumb" recommendations and the actual results

are predicated on the final layout.

8.1 Power and Ground Circuits

Star trace routing techniques can have a major positive impact on low-level signal performance. Star trace

routing refers to using individual traces that radiate from a signal point to feed power and ground to each

circuit or even device.

4AN-1768 LME49600 Headphone Amplifier Evaluation Board SNAA052A–February 2008–Revised May 2013

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Bill of Materials

9 Bill of Materials

RefDes Part Description Value Tolerance Rating Package Manufacturer

Type and Part Number

9V Battery Terminal (male & KEYSTONE

BAT1– BAT2 female) [Not Installed] 593 (Female) & 594 (Male)

MULITYLAYER CERAMIC TDK

C1 – C8 1.0μF ±20% 25V 805

CAPACITOR C2012X5R1E105M

C9 C10, C23 – TANTALUM ELECTROLYTIC AVX

4.7μF ±10% 35V B CASE

C24 CAPACITOR TPSB475K035R0700

AVX

C12, C14 22μF ±20% 25V C CASE TPSD226M025#011

CERAMIC CAPACITOR 25V 603 TDK

C19 – C22 0.1μF ±10% C1608X7R1E104K

HPJ1– HPJ2 1/8” Stereo Headphone Jack

J1 – J2 RCA jack

JU1, JU4, JU6, 100mil pin pitch, two pin

JU14, JU15, JU17

JU19 100mil pin pitch, three pin

1/4W resistor 1kΩ±1% 1/4W YAGEO

R1 – R6 1/4W, Axial MFR-25FBF-1K00

1/4W resistor 1MΩ±1% 1/4W YAGEO

R9 – R12 1/4W, Axial MFR-25FBF-1M00

SWITCH SLIDE DPDT

S1 DPDT

[Not Installed] Texas Instruments

LME49720 (Can also use

U1, U2 LME49720

LM4562, LME49860) (LM4562 or LME49860)

Texas Instruments

U3, U4 LME49600 LME49600

PANASONIC

VR1 Dual gauged potentiometer 10kΩEVJ-Y00F30A14

10 Demonstration Board PCB Layout

Figure 3 through Figure 6 show the different layers used to create the LME49600 demonstration board.

Figure 3 is the silkscreen that shows parts location, Figure 4 is the top layer, Figure 5 is the bottom layer,

and Figure 6 is the bottom silkscreen layer.

SNAA052A–February 2008–Revised May 2013 AN-1768 LME49600 Headphone Amplifier Evaluation Board

Demonstration Board PCB Layout

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Figure 3. Top Silkscreen

Figure 4. Top Layer

6AN-1768 LME49600 Headphone Amplifier Evaluation Board SNAA052A–February 2008–Revised May 2013

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Demonstration Board PCB Layout

Figure 5. Bottom Layer

Figure 6. Bottom Silk Layer

SNAA052A–February 2008–Revised May 2013 AN-1768 LME49600 Headphone Amplifier Evaluation Board

0.0001

0.001

0.000001

0.00001

0.0001

0.001

0.01

0.1

OUTPUT POWER (W)

THD+N (%)

0.01

0.00001

0.0001

0.000001

0.00001

0.0001

0.001

0.01

0.1

OUTPUT POWER (W)

THD+N (%)

0.001

0.01

0.0001

0.001

0.000001

0.00001

0.0001

0.001

0.01

0.1

OUTPUT POWER (W)

THD+N (%)

0.01

0.00001

0.0001

0.000001

0.00001

0.0001

0.001

0.01

0.1

OUTPUT POWER (W)

THD+N (%)

0.001

0.01

Typical Performance

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11 Typical Performance

Figure 7. THD+N vs Output Power Figure 8. THD+N vs Output Power

LME49720/LME49600 headphone amplifier LME49720/LME49600 headphone amplifier

into (from top to bottom at 0.1mW): into (from top to bottom at 10mW):

16Ω, 32Ω, 64Ω, 300Ω16Ω, 32Ω, 64Ω, 300Ω

(VS= ±3V, f = 100Hz, 22Hz ≤BW ≤22kHz) (VS= ±9V, f = 100Hz, 22Hz ≤BW ≤22kHz)

Figure 9. THD+N vs Output Power Figure 10. THD+N vs Output Power

LME49720/LME49600 headphone amplifier LME49720/LME49600 headphone amplifier

into (from top to bottom at 10mW): into (from top to bottom at 0.1mW):

16Ω, 32Ω, 64Ω, 300Ω16Ω, 32Ω, 64Ω, 300Ω

(VS= ±15V, f = 100Hz, 22Hz ≤BW ≤22kHz) (VS= ±3V, f = 1kHz, 400Hz ≤BW ≤22kHz)

8AN-1768 LME49600 Headphone Amplifier Evaluation Board SNAA052A–February 2008–Revised May 2013

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0.00001

0.0001

0.000001

0.00001

0.0001

0.001

0.01

0.1

OUTPUT POWER (W)

THD+N (%)

0.001

0.01

0.0001

FREQUENCY (Hz)

THD+N (%)

0.001

10 100 1k 10k 100k

0.0001

0.001

0.000001

0.00001

0.0001

0.001

0.01

0.1

OUTPUT POWER (W)

THD+N (%)

0.01

0.00001

0.0001

0.000001

0.00001

0.0001

0.001

0.01

0.1

OUTPUT POWER (W)

THD+N (%)

0.001

0.01

0.00001

0.0001

0.000001

0.00001

0.0001

0.001

0.01

0.1

OUTPUT POWER (W)

THD+N (%)

0.001

0.01

0.00001

0.0001

0.000001

0.00001

0.0001

0.001

0.01

0.1

OUTPUT POWER (W)

THD+N (%)

0.001

0.01

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Typical Performance

Figure 11. THD+N vs Output Power Figure 12. THD+N vs Output Power

LME49720/LME49600 headphone amplifier LME49720/LME49600 headphone amplifier

into (from top to bottom at 10mW): into (from top to bottom at 10mW):

16Ω, 32Ω, 64Ω, 300Ω16Ω, 32Ω, 64Ω, 300Ω

(VS= ±9V, f = 1kHz, 400Hz ≤BW ≤22kHz) (VS= ±15V, f = 1kHz, 400Hz ≤BW ≤22kHz)

Figure 13. THD+N vs Output Power Figure 14. THD+N vs Output Power

LME49720/LME49600 headphone amplifier LME49720/LME49600 headphone amplifier

into (from top to bottom at 0.1mW): into (from top to bottom at 20mW):

16Ω, 32Ω, 64Ω, 300Ω16Ω, 32Ω, 64Ω, 300Ω

(VS= ±3V, f = 10kHz, 400Hz ≤BW ≤80kHz) (VS= ±9V, f = 10kHz, 400Hz ≤BW ≤80kHz)

Figure 15. THD+N vs Output Power Figure 16. THD+N vs Frequency

LME49720/LME49600 headphone amplifier LME49720/LME49600 headphone amplifier

into (from top to bottom at 20mW): into (from top to bottom at 5kHz): 16Ωat 3mW, 32Ωat

16Ω, 32Ω, 64Ω, 300Ω3mW, 300Ωat 0.3mW, and 64Ωat 1.5mW

(VS= ±15V, f = 10kHz, 400Hz ≤BW ≤80kHz) (VS= ±3V, < 10Hz ≤BW ≤80kHz)

SNAA052A–February 2008–Revised May 2013 AN-1768 LME49600 Headphone Amplifier Evaluation Board

0.00001

FREQUENCY (Hz)

THD+N (%)

0.01

10 100 1k 10k 100k

0.001

0.0001

0.00001

FREQUENCY (Hz)

THD+N (%)

0.01

10 100 1k 10k 100k

0.001

0.0001

Revision History

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Figure 17. THD+N vs Frequency Figure 18. THD+N vs Frequency

LME49720/LME49600 headphone amplifier LME49720/LME49600 headphone amplifier

into (from top to bottom at 5kHz): 16Ωat 100mW, 32Ωinto (from top to bottom at 5kHz): 16Ωat 100mW, 32Ω

at 100mW, 64Ωat 35mW, and 300Ωat 8mW at 100mW, 64Ωat 150mW, and 300Ωat 30mW

(VS= ±9V, < 10Hz ≤BW ≤80kHz) (VS= ±15V, < 10Hz ≤BW ≤80kHz)

12 Revision History

Rev Date Description

1.0 02/29/08 Initial release.

10 AN-1768 LME49600 Headphone Amplifier Evaluation Board SNAA052A–February 2008–Revised May 2013

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