LM4981
Ground-Referenced,80mW Stereo Headphone Amplifier with Digital Volume Control
General Description
The LM4981is a stereo,ground-referenced,output capacitor-less headphone amplifier capable of delivering 83mW of continuous average power into a 16Ωload with less than 1%THD+N while operating from a single 3V supply.
The LM4981features a new circuit technology that utilizes a charge pump to generate a negative reference voltage.This allows the outputs to be biad about ground,thereby elimi-nating output-coupling capacitors typically ud with normal single-ended loads.
The LM4981provides high quality audio reproduction with minimal external components.A ground referenced output eliminates the output coupling capacitors typically required to drive single-ended loads such as headphones.The ground reference architecture reduces components count,cost and board space consumption,making the LM4981ideal for handheld MP3players,mobile phones and other portable equipment where board space is at a premium.Eliminating the output capacitors also improves low fre-quency respon.
抛物线及其标准方程The LM4981operates from a single 2.0V –4.2V supply,and features a 2-wire,up/down volume control that ts the gain of the amplifier between -33dB to +12dB in 16discrete steps.Selectable (active high/low)low power shutdown mode provides flexible shutdown control.Superior click and pop suppression eliminates audible transients during start-up and shutdown.
The LM4981features an Automatic Standby Mode circuitry (patent pending).In the abnce of an input signal,after approximately 12conds,the LM4981goes into low cur-rent standby mode.The LM
4981recovers into full power operating mode immediately after a signal is applied to either the left or right input pins.This feature saves power supply current in battery operated applications.
Key Specifications
j Improved PSRR at 217Hz 67dB (typ)j THD+N at 1kHz,50mW
into 32ΩSE (3V)
1.0%(typ)j Single Supply Operation (V DD )
2.0to 4.2V j Power Output at VDD =3V,
RL =16Ω,THD ≤1%
83mW (typ)j Shutdown Current
0.01µA (typ)
Features
n Ground Referenced Outputs n No Output Coupling Capacitors n 16-Step Volume Control n Auto-Standby Mode n High PSRR
n Available in Space Saving LLP package n Low Power Shutdown Mode
n
Improved Click and Pop Suppression Eliminates Nois During Turn-on and Turn-off Transients n 2.0V to 4.2V Operation
n 83mW Per Channel Into 16Ω
n Selectable Shutdown Controls (Active High/Low)Applications
n Portable MP3Players n Mobile Phones n PDAs
ppt加页码Boomer ®is a registered trademark of National Semiconductor Corporation.
November 2005
LM4981Ground-Referenced,80mW Stereo Headphone Amplifier with Digital Volume Control
©2005National Semiconductor Corporation
Connection Diagrams
LLP Package
折服的近义词20147338
Top View
Order Number LM4981SQ
See NS Package Number SQA16A
LLP Marking
20147321
Top View U =Plant Code ZX =Date Code X =Die Traceability Bottom Line =Part Number
L M 4981
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Typical Application
Pin Name Function
1CP VDD Charge Pump Power Supply
2CCP+Positive Terminal-charge pump flying capacitor
3PGND Power Ground
4CCP-Negative Terminal-charge pump flying capacitor
5VCP_OUT Charge Pump Output
临时身份证要多久
6CLOCK Clock 7UP/DN Up /Down 8INR Right Input
9AV DD Positive Power Supply -Amplifier
10OUT R Right Output
比比窝窝
11AV SS Negative Power Supply -Amplifier
12OUT L Left Output 13IN L Left Input 14SGND Signal Ground 15SD Shutdown 16
SD MODE
Shutdown Mode Pin
20147337
FIGURE 1.Typical Audio Amplifier Application Circuit
LM4981
3
Absolute Maximum Ratings (Note 2)
理论学习心得If Military/Aerospace specified devices are required,plea contact the National Semiconductor Sales Office/Distributors for availability and specifications.Supply Voltage 4.5V
Storage Temperature −65˚C to +150˚C Input Voltage
−0.3V to V DD +0.3V Power Dissipation(Note 3)Internally Limited
ESD Susceptibility (Note 4)
2500V
ESD Susceptibility (Note 5)250V Junction Temperature
150˚C
Operating Ratings
Temperature Range T MIN ≤T A ≤T MAX −40˚C ≤T
A
≤85˚C
Supply Voltage (V DD )
2.0V ≤V CC ≤4.2V
Electrical Characteristics V DD =3V (Notes 1,2)
The following specifications apply for V DD =3V,AV =1V/V R L =32Ω,f =1kHz,unless otherwi specified.Limits apply to T A =25˚C.Symbol
Parameter
Conditions
LM4981Units (Limits)Typical (Note 6)
Limit (Note 7)I DD Quiescent Power Supply Current V IN =0V,R L =∞
710
mA I DD Standby Power Supply Current 2.3mA I SD Shutdown Current V SD =GND
0.1
3.5µA V IH Logic Input Voltage High SHDN,SDM,CLOCK,U/D 0.7V DD V V IL
Logic Input Voltage Low SHDN,SDM,CLOCK,U/D 0.3V DD V Digital Volume Input Referred Maximum Gain 12dB Input Referred Minimum Gain
–33dB Volume Step Size 3
dB Step Size Error
±0.3
dB Channel-to-Channel Volume Tracking Error
All gain ttings 0.15dB T WU Wake Up Time 300µs
V OS
Output Offt Voltage
R L =32Ω
15
mV P O
Output Power
THD+N =1%(max);f =1kHz,R L =16Ω,one channel 83mW THD+N =1%(max);f =1kHz,R L =32Ω,one channel
75mW
THD+N =1%(max);f =1kHz,R L =16Ω,(two channels in pha)4033mW (min)THD+N =1%(max);f =1kHz,R L =32Ω,(two channels in pha)4743
mW (min)
THD+N Total Harmonic Distortion P O =60mW,f =1kHz,R L =16Ωsingle channel
0.03%
P O =50mW,f =1kHz,R L =32Ωsingle channel
0.02
PSRR
Power Supply Rejection Ratio
V RIPPLE =200mV P-P Sine,
f RIPPLE =1kHz,Inputs AC GND,Cl =1µF
65dB
V RIPPLE =200mV P-P Sine,
f RIPPLE =10kHz,Inputs AC GND,Cl =1µF
50dB
V RIPPLE =200mV P-P Sine,f RIPPLE =217Hz
67dB ∈OS
Output Noi
A-Weighted Filter 11万壑争流
µV
L M 4981
4
LM4981 Electrical Characteristics V
=3V(Notes1,2)(Continued)
DD
Note1:All voltages are measured with respect to the GND pin unless other wi specified
Note2:Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.Operating Ratings indicate conditions for which the device is functional but do not guarantee specific performance limits.Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guarantee specific performance limits.This assumes that the device is within the Operating Ratings.Specifications are not guaranteed for parameters where no limit
is given,however,the typical value is a good indication of device performance.
Note3:The maximum power dissipation must be derated at elevated temperatures and is dictated by T JMAX,θJA,and the ambient temperature,T A.The maximum allowable power dissipation is P DMAX=(T JMAX–T A)/θJA or the number given in Absolute Maximum Ratings,whichever is lower.For the LM4917,e power
derating currents for more information.
Note4:Human body model,100pF discharged through a1.5kΩresistor.
Note5:Machine Model,220pF-240pF discharged through all pins.
Note6:Typical specifications are specified at+25˚C and reprent parametric norm.
Note7:Limits are guaranteed to National’s AOQL(Average Outgoing Quality Level).
5
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