LM4985 - LM4985 Stereo 135mW Low Noise Headphone Amplifier with Selectable Capacitive Coupled or OCL Output and Digitally Controlled (I2C) Volume Control

	LM4985 - LM4985 Stereo 135mW Low Noise Headphone Amplifier with Selectable Capacitive Coupled or OCL Output and Digitally Controlled (I2C) Volume Control

Datasheet	Packaging	Samples & Pricing	Eval. Boards	Reliability	Design Tools	Knowledge Base

Features

•	OCL or capacitively coupled outputs (patent pending)
•	I²C Digitally Controlled Volume Control
•	Available in space-saving 0.4mm lead-pitch micro SMD package
•	Volume control range: -76dB to +18dB
•	Ultra low current shutdown mode
•	2.3V - 5.5V operation
•	Ultra low noise

Key Specification

PSRR: 217Hz and 1kHz
Output Capacitor-less (OCL)
f_RIPPLE = 217Hz	77dB (typ)
f_RIPPLE = 1kHz	76dB (typ)
Capacitor Coupled (C-CUPL)
f_RIPPLE = 217Hz	63dB (typ)
f_RIPPLE = 1kHz	62dB (typ)
Output Power per channel (f_IN = 1kHz, THD+N = 1%), R_L = 16,OCL
V_DD = 2.5V	31mW (typ)
V_DD = 3.6V	68mW (typ)
V_DD = 5.0V	135mW (typ)
THD+N (f = 1kHz)
R_LOAD = 16, OCL, P_OUT = 60mW	0.60
R_LOAD = 32, OCL, P_OUT = 33mW	0.031
Shutdown Current	0.1µA (typ)

General Description

The LM4985 is a stereo audio power amplifier with internal digitally controlled volume control. More...

Applications

•	Mobile Phones
•	PDAs
•	Portable electronics devices
•	MP3 Players

Typical Application

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Parametric Table expand

Parametric Table collapse

Power@ 8Ohms, 1% THD Undefined Watt

Power@ 16Ohms, 1% THD 0.135 Watt

Power@ 32Ohms, 1% THD 0.08 Watt

Power@ 8Ohms, 10% THD Undefined Watt

THD 0.08 %

PSRR 77 dB

Channels 2 Channels

THD Conditions Pout = 100mW, f = 1kHz, Rload = 16ohms

PSRR Conditions OCL mode, f = 217Hz, Rload = 16ohms

Power@ 8Ohms, 1% THD Undefined Watt

Power@ 16Ohms, 1% THD 0.135 Watt

Power@ 32Ohms, 1% THD 0.08 Watt

Power@ 8Ohms, 10% THD Undefined Watt

THD 0.08 %

PSRR 77 dB

Channels 2 Channels

THD Conditions Pout = 100mW, f = 1kHz, Rload = 16ohms

PSRR Conditions OCL mode, f = 217Hz, Rload = 16ohms

User Supply 5 Volt

Shutdown Type I2C

Supply Range +2.2 - +5.5 V

Volume Control 32 step I2C

Exposed DAP No

Capless Headphone Yes

Temperature Min -40 deg C

Temperature Max 85 deg C

Automotive Selection Guide Yes

View Using Catalog

Typical Performance

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Additional Resources

Design Tools (see below)

Block Diagram

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Datasheet

RoHS Compliance Information	Size in Kbytes	Date
LM4985 Boomer ® Audio Power Amplifier Series Stereo 135mW Low Noise Headphone Amplifier with Selectable Capacitively Coupled or Output Capacitor-less (OCL) Output and Digitally Controlled (I2C) V	1492 Kbytes	30-May-06	View Online Download

If you have trouble printing or viewing PDF file(s), see Printing Problems.

Package Availability, Models, Samples & Pricing

Part Number

Package

Factory Lead Time

Models

Samples &
Electronic
Orders

Budgetary Pricing

Std
Pack
Size

Package
Marking
Format

Type

Pins

Spec.

MSL
Rating

Peak
Reflow

RoHS
Report

CAD
Symbols

Weeks

Qty

$US each

LM4985TMEVAL

LM4985 Stereo 135mW Low Noise Headphone Amplifier with Selectable Capacitive Coupled or OCL Output and Digitally Controlled (I2C) Volume Control

Full production

N/A

$175.00

N/A

LM4985TM

MICRO SMD

NOPB

260

RoHS

Download

Full production

N/A

1K+

$1.46

reel
of
250

XVG
I H2

6 weeks

N/A

LM4985TMX

MICRO SMD

NOPB

260

RoHS

Download

Full production

N/A

1K+

$1.46

reel
of
3000

XVG
I H2

16 weeks

N/A

General Description

The LM4985 is a stereo audio power amplifier with internal digitally controlled volume control. This amplifier is capable of delivering 68mW_RMSper channel into a 16 load or 38mW_RMS per channel into a 32 load at 1% THD when 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 (I²C bus) volume control and an operational mode that eliminates output signal coupling capacitors (OCL mode). Since the LM4985 does not require bootstrap capacitors, snubber networks, or output coupling capacitors, it is optimally suited for low-power, battery powered portable systems. For added design flexibility, the LM4985 can also be configured for single-ended capacitively coupled outputs.

The LM4985 features a current shutdown mode for micropower dissipation and thermal shutdown protection.

Reliability Metrics

Part Number	Process	EFR Reject	EFR Sample Size	PPM *	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LM4985TM	CMOS7	0	13906	0	0	862500	5	244736730
LM4985TMX	CMOS7	0	13906	0	0	862500	5	244736730

Note: The Early Failure Rates were calculated as point estimates. The Long Term Failure Rates were calculated at 60% confidence using the Arrhenius equation at 0.7eV activation energy and derating the assumed stress temperature of 150°C to an application temperature of 55°C.

For more information on Reliability Metrics, please click here.

Design Tools

Title	Size in Kbytes	Date
Audio Amplifier Digital Control Interface Evaluation Board Software	16 Kbytes	27-Mar-2008	View

If you have trouble printing or viewing PDF file(s), see Printing Problems.

Application Notes

Title	Size in Kbytes	Date
AN-1452: Application Note 1452 LM4985 Evaluation Board User's Guide	1190 Kbytes	26-May-06	Download

If you have trouble printing or viewing PDF file(s), see Printing Problems.

[Information as of 13-Oct-2008]