lm4985tmx National Semiconductor Corporation, lm4985tmx Datasheet

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lm4985tmx

Manufacturer Part Number
lm4985tmx
Description
Stereo 135mw Low Noise Headphone Amplifier With Selectable Capacitively Coupled Or Output Capacitor-less Ocl Output And Digitally Controlled I2c V
Manufacturer
National Semiconductor Corporation
Datasheet
© 2006 National Semiconductor Corporation
LM4985
Stereo 135mW Low Noise Headphone Amplifier with
Selectable Capacitively Coupled or Output
Capacitor-less (OCL) Output and Digitally Controlled
(I
General Description
The LM4985 is a stereo audio power amplifier with internal
digitally controlled volume control. This amplifier is capable
of delivering 68mW
38mW
powered by a 3.6V power supply and operating in the OCL
mode.
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. To that end, the LM4985 features two
functions that optimize system cost and minimize PCB area:
an integrated, digitally controlled (I
and an operational mode that eliminates output signal cou-
pling capacitors (OCL mode). Since the LM4985 does not
require bootstrap capacitors, snubber networks, or output
coupling capacitors, it is optimally suited for low-power, bat-
tery powered portable systems. For added design flexibility,
the LM4985 can also be configured for single-ended capaci-
tively coupled outputs.
The LM4985 features a current shutdown mode for mi-
cropower dissipation and thermal shutdown protection.
Boomer
2
C) Volume Control
®
RMS
is a registered trademark of National Semiconductor Corporation.
per channel into a 32Ω load at 1% THD when
RMS
per channel into a 16Ω load or
2
C bus) volume control
DS201697
Key Specifications (V
Features
n OCL or capacitively coupled outputs (patent pending)
n I
n Available in space-saving 0.4mm lead-pitch micro SMD
n Volume control range: –76dB to +18dB
n Ultra low current shutdown mode
n 2.3V - 5.5V operation
n Ultra low noise
Applications
n Mobile Phones
n PDAs
n Portable electronics devices
n MP3 Players
j
j
j
j
package
(f
R
2
Output Capacitor-less (OCL)
Capacitor Coupled (C-CUPL)
PSRR: 217Hz and 1kHz
Output Power per channel
THD+N (f = 1kHz)
Shutdown Current
C Digitally Controlled Volume Control
IN
L
f
f
f
f
V
V
V
R
R
RIPPLE
RIPPLE
RIPPLE
RIPPLE
= 16Ω,OCL
= 1kHz, THD+N = 1%),
DD
DD
DD
LOAD
LOAD
= 2.5V
= 3.6V
= 5.0V
= 16Ω, OCL, P
= 32Ω, OCL, P
= 217Hz
= 1kHz
= 217Hz
= 1kHz
OUT
OUT
= 60mW
= 33mW
DD
= 3.6V)
135mW (typ)
www.national.com
31mW (typ)
68mW (typ)
0.1µA (typ)
77dB (typ)
76dB (typ)
63dB (typ)
62dB (typ)
May 2006
0.031
0.60

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lm4985tmx Summary of contents

Page 1

... LM4985 can also be configured for single-ended capaci- tively coupled outputs. The LM4985 features a current shutdown mode for mi- cropower dissipation and thermal shutdown protection. Boomer ® registered trademark of National Semiconductor Corporation. © 2006 National Semiconductor Corporation Key Specifications (V j PSRR: 217Hz and 1kHz Output Capacitor-less (OCL) ...

Page 2

Block Diagram www.national.com FIGURE 1. Block Diagram 2 201697E9 ...

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Typical Application FIGURE 2. Typical Capacitively Coupled Output Configuration Circuit FIGURE 3. Typical OCL Output Configuration Circuit 3 201697F0 201697F1 www.national.com ...

Page 4

Connection Diagrams micro SMD Package Top View Order Number LM4985TM See NS Package Number TMD12AAA Reference www.national.com 20169715 Pin Reference, Name, and Function Name ADR IN2 OUT2 SDA ...

Page 5

Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. 2 Supply Voltage ( Storage Temperature Input Voltage (IN1, IN2, OUT1, OUT2, BYPASS, ...

Page 6

Electrical Characteristics V The following specifications apply for R 25˚C. Symbol Parameter T Wake Up Time form Shutdown WU R Input Resistance IN A Minimum Gain VMIN A Maximum Gain VMAX ∆A Gain Accuracy per Step V V Output Offset ...

Page 7

Electrical Characteristics V The following specifications apply for R 25˚C. Symbol Parameter THD+N Total Harmonic Distortion + Noise V Output Noise Voltage ON PSRR Power Supply Rejection Ratio Xtalk Channel-to-Channel Crosstalk T Wake Up Time from Shutdown WU R Input ...

Page 8

Electrical Characteristics V The following specifications apply for R 25˚C. Symbol Parameter I Quiescent Power Supply Current DD I Shutdown Current SD V Logic Voltage Input High SDIH V Logic Voltage Input Low SDIL P Output Power O THD+N Total ...

Page 9

Electrical Characteristics V The following specifications apply for R 25˚C. Symbol Parameter A Maximum Gain VMAX ∆A Gain Accuracy per Step V V Output Offset Voltage OS Note 1: All voltages are measured with respect to the GND pin unless ...

Page 10

Typical Performance Characteristics T = 25˚ 0dB 1kHz unless otherwise stated THD+N vs Frequency V = 2.5V 20mW, C-CUPL OUT THD+N vs Frequency ...

Page 11

Typical Performance Characteristics THD+N vs Frequency V = 2.5V 16Ω 20mW, OCL OUT THD+N vs Frequency V = 5.0V 16Ω 50mW, OCL OUT THD+N vs Frequency V = ...

Page 12

Typical Performance Characteristics THD+N vs Output Power V = 2.5V C-CUPL THD+N vs Output Power V = 5.0V C-CUPL THD+N vs Output Power V = 3.6V C-CUPL www.national.com (Continued) = 16Ω ...

Page 13

Typical Performance Characteristics THD+N vs Output Power V = 2.5V 16Ω OCL THD+N vs Output Power V = 5.0V 16Ω OCL THD+N vs Output Power V = 3.6V 32Ω DD ...

Page 14

Typical Performance Characteristics PSRR vs Frequency V = 2.5V 200mVpp, OCL RIPPLE PSRR vs Frequency V = 5.0V 200mVpp, OCL RIPPLE PSRR vs Frequency V = 3.6V ...

Page 15

Typical Performance Characteristics PSRR vs Frequency V = 2.5V 16Ω 200mVpp, C-CUPL RIPPLE PSRR vs Frequency V = 5.0V 16Ω 200mVpp, C-CUPL RIPPLE PSRR vs Frequency V = ...

Page 16

Typical Performance Characteristics Crosstalk vs Frequency V = 2.5V 20mW. OCL OUT Crosstalk vs Frequency V = 5.0V 40mW, OCL OUT Crosstalk vs Frequency V = 3.6V ...

Page 17

Typical Performance Characteristics Crosstalk vs Frequency V = 2.5V 16Ω 20mW, C-CUPL OUT Crosstalk vs Frequency V = 5.0V 16Ω 50mW, C-CUPL OUT Crosstalk vs Frequency V = ...

Page 18

Typical Performance Characteristics Load Dissipation vs Amplifier Dissipation V = 2.5V, C-CUPL DD Load Dissipation vs Amplifier Dissipation V = 5.0V, C-CUPL DD Load Dissipation vs Amplifier Dissipation V = 3.6V, OCL DD www.national.com (Continued) Load Dissipation vs Amplifier Dissipation ...

Page 19

Typical Performance Characteristics Output Power vs Load Resistance V = 2.5V, C-CUPL DD Output Power vs Load Resistance V = 5.0V, C-CUPL DD Output Power vs Load Resistance V = 3.6V, OCL DD (Continued) Output Power vs Load Resistance V ...

Page 20

Typical Performance Characteristics Output Power vs Supply Voltage R = 16Ω, C-CUPL L Output Power vs Supply Voltage R = 16Ω, OCL L Supply Current vs Supply Voltage R = 16Ω, C-CUPL L www.national.com (Continued) Output Power vs Supply Voltage ...

Page 21

Typical Performance Characteristics Supply Current vs Supply Voltage R = 16Ω, OCL L Gain vs Volume Steps V = 2.5V 16Ω, OCL CC L Gain vs Volume Steps 16Ω, OCL CC L (Continued) ...

Page 22

Typical Performance Characteristics Gain vs Volume Steps V = 3.6V 16Ω, C-CUPL CC L Gain vs Volume Steps V = 2.5V 32Ω, OCL CC L Gain vs Volume Steps 32Ω, OCL ...

Page 23

Typical Performance Characteristics Gain vs Volume Steps V = 3.6V 32Ω, C-CUPL CC L (Continued) Gain vs Volume Steps V CC 201697G1 32Ω, C-CUPL L 201697G5 www.national.com ...

Page 24

Application Information AMPLIFIER CONFIGURATION EXPLANATION As shown in Figure 1, the LM4985 has three internal power amplifiers. Two of the amplifiers which amplify signals ap- plied to their inputs, have internally configurable gain. The remaining third amplifier provides both half-supply ...

Page 25

Application Information coupling capacitor requires more charge to reach its quies- cent DC voltage. This charge comes from the output via the feedback Thus, by minimizing the capacitor size based on necessary low frequency response, turn-on time can be minimized. ...

Page 26

I C Control Register Table 1 shows the actions that are implemented by manipulating the bits within the two internal I Table 1. LM4985 I LM4985 I2C Contorl Register Addressing and Data Chart A6 A5 I2C Address 1 1 ...

Page 27

Volume Control Settings Binary Values The minimum volume setting is set to –76dB when 00000 is loaded into the volume control register. Incrementing the volume control register in binary fashion increases the volume control setting, reaching full scale at 11111. ...

Page 28

Revision History Rev 1.0 www.national.com Date 05/17/06 Initial WEB release. 28 Description ...

Page 29

Physical Dimensions inches (millimeters) unless otherwise noted ± 1.215mm 0.03mm X 1 National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time ...

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