HighPerformance Audio Amplifiers for Portable Applications

1
1
2
High-Performance Audio Amplifiers for Portable
Applications
Kevin Hoskins Alvin Fok
Audio Product Line Applications
2
3
Overview

• New Products
• New Technology
• Package Technology Overview
• Design Aids

4
New Products

• LM4854
• LM4838
• LM4867
• LM4868
• LM4894
• LM4910
• LM4911

5
New Technology

• Capacitorless Operation

6
Package Technology Overview

• Leaded Surface-Mount Packages
• SO / MSOP /
  TSSOP
• Leadless Leadframe Packages
• LD / LQ
• microSMD Packages
• IBP / ITL

7
Design Aids

• Datasheets
• Demoboards

8
LM4910 Boomer Description

• Output Capacitor-less Stereo 35mW headphone
  amplifier

9
LM4910 Boomer Schematic
10
LM4910 Boomer Specifications

• Stereo 35mW output (VDD 3.3V RL 32W)
• 65 dB PSRR _at_ f 217Hz
• 0.1uA Shutdown Current

11
LM4910 Boomer Advantages

• Eliminates output coupling capacitors
• Eliminates ½ VDD bypass capacitor
• Eliminates noises during device turn on/off

12
LM4910 Boomer Packaging Solutions

• Available in SO and MSOP packaging

13
Classical Stereo Headphone Amplifier Circuit

• Single-ended stereo headphones
• DC blocking output capacitors (Co) required

14
Why LM4910 Boomer?

• For audio frequencies Co is large
• Tradeoff between low frequency response and
  system cost (large and expensive Co)

Co ? 1 / (2pfRL)
15
Eliminating the Output Capacitor

• DC quiescent current through the headphone driver
  must be zero
• Addition of third amplifier as a buffered
  reference voltage
• 6dB PSRR

-
AMPA

VDD
-
AMPC


AMPB
-
16
Bandgap Reference Voltage

• A bandgap is used to create VREFERENCE
• VREFERENCE is independent of the LM4910s supply
  voltage
• 6dB PSRR problem eliminated (65dB PSRR _at_ 217Hz)

17
Limitation of the Bandgap Reference Voltage

• VREFERENCE 1.58V
• Ideal for a supply range of 3.0V ? VDD ? 3.3V
• Aimed at PDA and other portable electronic
  applications

Output Power _at_ VDD 3.3V (1 THDN)
EQUALS Output Power _at_ VDD 5.0V
(1 THDN)
18
Limitation of the Bandgap Reference Voltage (cont)
5V
3.16V
1.58V
Audio signal
0V
19
Limitation of the Bandgap Reference Voltage (cont)
20
Limitation of the Bandgap Reference Voltage (cont)

• High output noise (45?V) mostly generated from
  the bandgap reference
• No Bypass Cap to filter the reference voltage

21
Output Noise

• NoiseAMPA NoiseBANDGAP(1 RF/RI)
• NoiseAMPC NoiseBANDGAP

22
Output Noise (cont)

• NoiseSPEAKER NoiseAMPA - NoiseAMPC
• NoiseSPEAKER NoiseBANDGAP(RF / RI)

RF
-
NoiseAMPA
AMPA
RI
NoiseBANDGAP

-
AMPC
NoiseAMPC

BANDGAP
NoiseBANDGAP
23
Noise Reduction Resistor
24
Noise Reduction Resistor (cont)

• NoiseVA NoiseAMPA(RL / (RL RSERIES))
• NoiseAMPA NoiseBANDGAP(1 RF / RI)
• NoiseAMPC NoiseBANDGAP

25
Noise Reduction Resistor (cont)

• NoiseSPEAKER NoiseVA - NoiseAMPC
• NoiseSPEAKER NoiseBANDGAP(RF / RI)(RL / (RL
  RSERIES))

26
Noise Reduction Resistor (cont)

• Output noise across the speaker is reduced by the
  factor (RL / (RL RSERIES))

27
Noise Reduction Resistor (cont)
28
Noise Reduction Resistor (cont)

• RSERIES limits the output power delivered to the
  speaker
• Output power is decreased by the factor of (RL /
  (RL RSERIES)2)
• RSERIES is an alternative way to reduce gain

29
Noise Reduction Resistor (cont)
30
Headphone Application Hints

• 2mW of headphone output power at the ear is
  approaching the human threshold of pain
• Many headphone applications incorporate an output
  power limiting series resistor
• Most new portable electronic music devices have
  an output power rating

31
Physical Connection
FLOATING JACK DO NOT CONNECT SLEEVE TO GROUND IN
YOUR SYSTEM
Headphone Jack
VoC
VoB
VoA
C
LM4910
Headphone Plug
32
Physical Connection (cont)

• No problem connecting to external consumer audio
  equipment under common GND condition when
  using Headphone Jack as Line Out !!

33
Physical Connection (cont)

• Even in the case where the headphone jacks
  sleeve is grounded, the
• LM4910s short circuit protection is activated

34
LM4910 Boomer Short Circuit Protection

• Monitors the current of the amplifer (AMPC) that
  drives the headphone jacks sleeve
• If this current is greater than 500mA then AMPC
  will immediately turn off
• Protects the LM4910 as well as the external
  equipment

35
Output Capacitorless Power Dissipation

• Output Capacitor-less configuration has increased
  power dissipation due to VREFERENCE amplifier
  (AMPC)
• Four times the maximum power dissipation of a
  classical stereo headphone amplifier

36
Power Dissipation Comparison
37
LM4911 Boomer Description

• Stereo 25mW low noise amplifier with selectable
  Capacitive Coupled (C-CUPL) or Output
  Capacitor-less (OCL) output modes

38
LM4911 Boomer Schematic(OCL Mode)
39
LM4911 Boomer Schematic(C-CUPL Mode)
40
LM4911 Boomer Specifications

• Mute mode allows fast turn-on (10ms)
• Less than 1mV of output voltage change when
  toggling Mute Mode
• Low noise (10 ?V)
• Stereo 25mW output (VDD 3.3V RL 32W)

41
LM4911 Boomer Advantages

• Eliminates output coupling capacitors in OCL Mode
• Ultra low Click/Pop (1mV)

42
LM4911 Boomer C-CUPL Mode
VoA

• Output coupling capacitors connected to VoA, VoB
• VoC is grounded

VoC
VoB
43
LM4911 Boomer C-CUPL Mode (cont)
AMPC
VoC

• Grounding VoC deactivates AMPC

44
LM4911 Boomer C-CUPL Mode (cont)

• To maintain 1mV output voltage change while
  toggling SHUTDOWN mode, turn on time is 2S in
  C-CUPL mode

45
LM4911 Boomer OCL Mode

• VoA, VoB, VoC are at the same potential
• Headphones can be directly connected to amplifier
  outputs
• Similar to LM4910 operation

VoA
VoC
VoB
46
LM4911 Boomer Mute Mode

• Allows for fast turn-on time (10mS typ) in
  C-CUPL mode
• Outputs are left at bias level
• Higher power consumption than SHUTDOWN mode

47
LM4911 Boomer Mute Mode (cont)

• Switch closes during Mute Mode

VDD
VDD
-
AMPA

VDD
-
AMPC

48
LM4911 Boomer Mute Mode (cont)
N / A Not Allowed
49
LM4911 Boomer Packaging Solutions

• Available in MSOP packaging

50
LM4894 Boomer Description

• Fully Differential 1W mono BTL amplifier
• Selectable Shutdown Mode (Low or High)
• No Input Coupling Caps Needed
• Very low Click/Pop

51
LM4894 Boomer Schematic
52
LM4894 Boomer Specifications

• High PSRR Vdd5V, input terminated 10? to GND
• 80dB (typ)
• Po at Vdd5V, THDN ? 1, RL 8?, f1kHz
• 1W (typ)

53
LM4867 Description

• 2.1W per channel, 4W BTL
• Capless SE stereo headphone amp (165mW, 16W)
• Truly, actual Pop-free, click-free operation
• Turn-on, BTL-SE switching, return from shutdown

54
LM4867 Schematic
55
LM4867 Boomer Dual 2.1W Audio Power Amp
Stereo Headphone Mode

• LM4867 KEY FEATURES
• 2 input MUX with individual
• Gain Setting
• Pop-Click Elimination circuitry
• Minimal Externals -
• No Bootstraps, Snubbers
• No Output Coupling Caps
• for speaker or headphone use

56
LM4867 Boomer Dual 2.1W Audio Power Amp
Stereo Headphone Mode

• LM4867 OUTPUT POWER
• LM4867LQ
• 2.4W _at_1.0 THD (Vcc5V, RL3ohm)
• 2.1W _at_1.0 THD (Vcc5V, RL4ohm)
• LM4867MT/MTE
• 1.9W _at_1.0 THD (Vcc5V, RL4ohm)
• 1.1W _at_1.0 THD (Vcc5V, RL8ohm)
• Stereo Headphone Mode
• 75mW _at_ 0.5 THD (Vcc5V, RL32ohm)
• Low-Current Shutdown Mode
• (ISD0.7uA), SDHigh

57
LM4867 Boomer Physical Headphone Connection
FLOATING JACK DO NOT CONNECT SLEEVE TO GROUND IN
YOUR SYSTEM
OUT A OUT A - HP- IN OUT B - OUT B
T
R
SPEAKER HEADPHONE CONNECTIONS
LM4867

• No Output Coupling Capacitors Required for
  Headphone Mode !!
• System Cost Reduction

58
LM4867 Boomer Mute Threshold

• Virtually eliminates Pops and Clicks when
  toggling in and out of SHUTDOWN mode
• Uses audio input signal monitoring
• Maintains muted condition until there is
  sufficient audio input signal magnitude to mask
  any remaining transient that may occur
• Mute threshold 60mVRMS (typ)
• LM4868 is pin-for-pin compatible, its Mute
  threshold is 25mVRMS (typ)

59
LM4867 BoomerESD Protection Headphone Mode

• Out A drives the headphone jack sleeve during
  headphone mode
• Out A provides a VDD/2 reference point
• There is a direct connection from the IC pin to
  outside world
• The LM4867 provides the following protection
• 8kV Human body model
• 200V Machine Model

60
LM4867 Applications Hints

• ESD protection for pin connected to headphone
  jack sleeve is 8kV
• For maximum ESD protection (15kV) an ESDAxxxL
  dual transil
• VDD 3V, use the ESDA5V3L
• VDD 5V, use the ESDA6V3L
• A Resistor (100W) from headphone sleeve to
  ground
• Minimizes 60Hz noise when computer/notebook is
  shutdown and powered speakers are connected.

61
ESDRecommended protection
HP-Jack Sleeve

• Connect the array directly to the HP- jacks
  sleeve pin
• In Lab survived 8kV surface1 and 15kV air2
  discharge
• Note 1 10 hits - ckt unpowered, 10 hits - ckt
  powered
• Note 2 5 hits - ckt unpowered, 5 hits - ckt
  powered

-
AMP2A

VDD
62
EMISuppression for non-grounded HP-jack sleeve

• Use capacitors and ferrite beads between
  amplifier output and speaker and headphone jack
  terminals
• Provides suppression on the speaker terminals
• Provides suppression on the headphone jack
• For the LM4867, the capacitor and ferrite beads
  can be used on the headphone sleeve connection

63
LM4867 Advantages

• Advantages over traditional audio amplifier.
• Eliminates four capacitors
• Two 220mF coupling capacitors for headphones
• Two 1mF bypass capacitors
• Eliminates three resistors
• Two 220kW resistors that discharge the headphone
  coupling capacitors
• One 100kW pull-down resistor

64
LM4867 Advantages, Cont.

• Glitch-free operation
• Output remains muted until input signal exceeds
  60mVRMS magnitude 35mVRMS (min) to 85mVRMS
  (max)
• More efficient board area utilization
• Fewer external components
• Smaller TSSOP 20-pin vs. 24-pin
• Even smaller package 4mm x 5mm 24-pin LLP

65
LM4867 Packaging Solutions
0.8mm
6.4mm
4mm
6.4mm
5mm
6.5mm
7.8mm
TSSOP-20
LLP-24
TSSOP-24
0.65mm Pitch
0.5mm Pitch
0.65mm Pitch
Traditional Solution
LM4867 High Performance Solution
66
LM4867 Cost Analysis Vs. Traditional Amplifier
Solution

• Cost analysis.
• The LM4867 saves 0.70 per board

LM4867 Traditional Amp ESD
Protection (x1) 0.10 NA Pulldown Resistor
(x1) NA 0.01 HP Sleeve Resistor (x1)
0.01 NA SE Pulldown Resistors (x2)
NA 0.02 Output Coupling Caps (x2)
NA 0.60 Bypass Capacitor (x2)
NA 0.20 Total 0.11 0.83
67
LM4854 Boomer Mono BTL Stereo Headphone
Amplifier

• Features
• Fast 0.1ms (typ) and 1.0ms (max) turn-on and
  turn-off time
• Capacitorless headphone operation eliminates
  output coupling capacitors
• Advanced click and pop suppression circuitry
• Low-power standby current is only 27mA (typ)
• Ultra-low micropower shutdown current is only
  0.05mA (typ)
• 2.4V to 5.5V operation
• Space-saving micro SMD package, exposed-DAP LLP,
  and TSSOP
• Thermal shutdown protection circuitry

68
LM4854 Boomer Mono BTL Stereo Headphone
Amplifier

• Shutdown vs. Standby
• Shutdown disables the VDD/2 circuitry, all bias
  circuitry, and mutes the amplifiers outputs
• When power is first applied or shutdown is
  deactivated, turn-on time is typically 120ms
  tCBYPASS
• Standby simply mutes the amplifier outputs
• During standby, all bias and VDD/2 circuitry
  remain active
• Activating or deactivating standby typically
  takes 0.1ms
• The fast standby time is the LM4854s key feature
• Shutdown current 0.05mA (typ)
• Standby current 27mA (typ)

69
LM4854 Mono BTL Stereo Headphone Amplifier

• Key Specifications
• LLP BTL output power (RL 4W, THDN 1)
• VDD 3.0V 900mW (typ)
• VDD 5.0V 1.7W (typ)
• LLP BTL output power (RL 8W, THDN 1)
• VDD 3.0V 380mW (typ)
• VDD 5.0V 1.1W (typ)
• SE output power (RL 32W, THDN 1.0)
• VDD 3.0V 32mW (typ)
• VDD 5.0V 93mW (typ)

70
LM4854 Mono BTL Stereo Headphone Amplifier

• Key Specifications (cont.)
• Micropower shutdown supply current
• VDD 3.0V 0.005µA (typ)
• VDD 5.0V 0.05µA (typ)
• Standby supply current
• VDD 3.0V 16µA (typ)
• VDD 5.0V 27µA (typ)
• PSRR (f 1kHz, 3.0V VDD 5.0V)
• BTL 60dB (typ)
• SE 66dB (typ)

71
LM4854 Mono BTL Stereo Headphone Amplifier
72
LM4854 Mono BTL Stereo Headphone Amplifier

• Applications
• PDAs
• Notebook computers
• Cellular phones
• Handheld portable electronic devices

73
LM4838 Stereo BTL Headphone Amplifier

• Features
• Improved DC Volume Control
• Revised Volume Control curve, more natural
  response
• Click and pop suppression circuitry
• Stereo bridged or single-ended power amplifiers
• Selectable internal/external gain and bass boost
• Thermal shutdown protection circuitry
• System Beep Detect

74
LM4838 Stereo BTL Headphone Amplifier

• Key Specifications
• BTL POUT (1 THDN)
• RL 3W (LQ MTE) 2.2W (typ)
• RL 4W (LQ MTE) 2.0W (typ)
• RL 8W (MT, MTE, LQ) 1.1W (typ)
• Single-ended POUT (1 THDN)
• RL 3W 85mW (typ)
• Shutdown current 0.7µA (typ)

75
LM4838 Stereo BTL Headphone Amplifier
76
LM4838 Stereo BTL Headphone Amplifier

• Applications
• Portable and Desktop Computers
• Multimedia Monitors
• Portable Radios
• PDAs
• Portable TVs

77
NS Audio ProductSurface Mount Package Technology
6.4MM
4.9MM
10MM
9.7MM
3MM
10.1MM
TSSOP-28 MTE-1
MSOP-8 MM
SO16 M
0.65MM Pitch
0.65MM Pitch
1.27MM Pitch
6.4MM
5.8MM
4.9MM
6.5MM
4.8MM
3MM
SO8 M
MSOP-10 MM
TSSOP-20 MT,MTE
0.5MM Pitch
0.65MM Pitch
1.27MM Pitch
78
micro-SMD

• Micro-SMD
• LM4872 IBP
• LM4877 IBP
• LM4890 IBP

79
micro-SMD

• National leads in this package technology
• Highest audio quality and output power (1W) in
  the smallest package available today
• The Die is the Package

LM4872 IBP Actual Die Photo Total Area 2.58 mm2
1.97 mm
80
Footprint Comparison
1.31 mm
1.97 mm
LM4872IBP 2.6 mm2 LM4877IBP LM4890IBP 1 W Boomer
LM4864MM 250mW Boomer 14.7 mm2
LM4871M 1 W Boomer 29.4 mm2
81
PCB Layout Guidelines

• micro SMD
• Non-Solder Mask-Defined (NSMD) pads
• 11 size landing pad area vs micro SMD bump
  diameter

82
PCB Layout Guidelines

• micro SMD
• Solder paste stencil apertures must be laser-cut

83
PCB Layout Guidelines

• micro SMD
• Electroplated NiAu finish on board must be less
  than 0.5mm to avoid solder-joint embrittlement
• See AN1112 for more information
• Available for LM4890, LM4872, LM4877

84
PCB Layout Guidelines

• micro SMD
• LM4890 demo board layout

85
NS Advanced Package Technology Leadframe CSP (
LLP)
0.8MM
4MM
5MM
LLP-24 LQ
0.5MM Pitch
86
Lead-less Lead Frame (LLP)

• Higher Output Power
• Perfect for Audio Sub-system products
• Current Leadless Lead Frame (LQ and LD) Products
• LM4871 LD
• LM4863 LQ
• LM4873 LQ
• and more to come

87
LM4871LD 4871 in LLP

• Pout up to 3.0W
• Package Size Reduction MSOP8 vs. LLP8 is 39

Please not that all numbers are preliminary and
still subject to significant changes
88
PCB Layout Guidelines

• LLP (w/ exposed DAP)
• 11 size landing pad area vs LLP pin and DAP area
• Non-Solder Mask-Defined (NSMD) landing pads
• DAP area perforated with 12mil 13mil thermal
  transfer via array on a 1.27mm pitch

89
PCB Layout Guidelines

• LLP (w/ exposed DAP)
• Vias connect DAP to thermal mass/heatsink area
  (bottom side or inter-layer
• Thermal mass/heatsink area ?40x package area
• Even for the largest package (7mm x 7mm),
  heatsink area is 45mm x 45mm
• 0.05?m 0.127?m gold plating

90
PCB Layout Guidelines

• LLP (w/ exposed DAP)
• Solder Stencil
• DAP stencil dimensions are 0.95 package DAP
  dimensions
• Pin stencil dimensions are 1-to-1, offset 0.1mm
  away from DAP
• For DAPs with any side larger than 5mm, split
  stencil opening into two equal areas separated by
  0.5mm
• See AN1187 for more information

91
PCB Layout Guidelines

• LLP (w/ exposed DAP)
• LM4871 demo board layout

92
PCB Layout Guidelines

• General Guidelines
• Star grounding
• 90 crossing of traces between planes
• Separate digital and analog power and ground
• Locate high-speed digital lines far from analog
  components and traces

93
93