TI1 LM4985 Laudio power amplifier series stereo 135mw low noise headphone amplifier with selectable capacitively coupled Datasheet

LM4985, LM4985TMEVAL
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SNAS346B – MAY 2006 – REVISED MAY 2006
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) Volume Control
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FEATURES
DESCRIPTION
•
The LM4985 is a stereo audio power amplifier with
internal digitally controlled volume control. This
amplifier is capable of delivering 68mWRMS per
channel into a 16Ω load or 38mWRMS per channel
into a 32Ω load at 1% THD when powered by a 3.6V
power supply and operating in the OCL mode.
1
23
•
•
•
•
•
•
OCL or Capacitively Coupled Outputs (Patent
Pending)
I2C Digitally Controlled Volume Control
Available in Space-Saving 0.4mm Lead-Pitch
DSBGA Package
Volume Control Range: –76dB to +18dB
Ultra Low Current Shutdown Mode
2.3V - 5.5V Operation
Ultra Low Noise
APPLICATIONS
•
•
•
•
Mobile Phones
PDAs
Portable Electronics Devices
MP3 Players
KEY SPECIFICATIONS (VDD = 3.6V)
•
•
•
•
PSRR: 217Hz and 1kHzs
– Output Capacitor-Less (OCL)
– fRIPPLE = 217Hz, 77dB (Typ)
– fRIPPLE = 1kHz, 76dB (Typ)
– Capacitor Coupled (C-CUPL)
– fRIPPLE = 217Hz, 63dB (Typ)
– fRIPPLE = 1kHz, 62dB (Typ)
Output Power Per Channel
(fIN = 1kHz, THD+N = 1%),
RL = 16Ω, OCL
– VDD = 2.5V, 31mW (Typ)
– VDD = 3.6V, 68mW (Typ)
– VDD = 5.0V, 135mW (Typ)
THD+N (f = 1kHz)
– RLOAD = 16Ω, OCL, POUT = 60mW, 0.60
– RLOAD = 32Ω, OCL, POUT = 33mW, 0.031
Shutdown Current, 0.1µA (Typ)
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.
1
2
3
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
Boomer is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2006, Texas Instruments Incorporated
LM4985, LM4985TMEVAL
SNAS346B – MAY 2006 – REVISED MAY 2006
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Block Diagram
Mux
Volume
Control
IN1
CNTGND
+
-
Volume
Control
IN2
Mux
Output
Transient
Suppression
and
Mode-Control
Logic
2
SCL
I2CVDD
OUT2
+
I C Digitally
Controlled
Analog Volume
Control
Interface
SDA
OUT1
+
Bias
Generator
BYPASS
-
VDD
GND
ADR
Figure 1. Block Diagram
Typical Application
0.47 PF
IN1
Volume
Control
BYPASS
Mux
-
2
Digital
Control
System
I C Digitally
Controlled
Analog Volume
Control
Interface
100 PF
CNTGND
+
0.47 PF
Volume
Control
OUT1
+
Bias
Generator
IN2
-
Mux
OUT2
100 PF
+
Output
Transient
Suppression
and
Mode-Control
Logic
VDD
GND
Figure 2. Typical Capacitively Coupled Output Configuration Circuit
2
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0.47 PF
IN1
BYPASS
-
Mux
Volume
Control
+
-
Bias
Generator
-
Volume
Control
Mux
OUT2
+
Output
Transient
Suppression
and
ModeControl Logic
2
I C Digitally
Controlled
Analog Volume
Control
Interface
Digital
Control
System
CNTGND
+
0.47 PF
IN2
OUT1
VDD
GND
Figure 3. Typical OCL Output Configuration Circuit
Connection Diagram
3
2
1
A
B
C
D
Figure 4. DSBGA Package
Top View
See NS Package Number YFQ0012
PIN REFERENCE, NAME, AND FUNCTION
Reference
Name
Function
A1
ADR
I2C serial interface address input.
A2
IN2
Analog signal input two.
A3
OUT2
B1
SDA
Power amplifier two output.
I2C serial interface data input.
B2
BYPASS
The internal VDD/2 ac bypass node.
B3
CNTGND
In OCL mode, this is the ac ground return. It is biased to VDD/2. Leave unconnected for CCUPL mode.
C1
SCL
I2C serial interface clock input.
C2
GND
The LM4985’s power supply ground input.
C3
VDD
The LM4985’s power supply voltage input.
D1
2
I CVDD
D2
IN1
D3
OUT1
I2C serial interface power supply input. Can be connected to the same supply that is
connected to the VDD pin.
Analog signal input one.
Power amplifier one output.
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These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Absolute Maximum Ratings (1) (2)
Supply Voltage (VDD, I2CVDD)
6.0V
−65°C to +150°C
Storage Temperature
Input Voltage (IN1, IN2, OUT1, OUT2, BYPASS, CNTGND, GND
pins relative to the VDD pin)
-0.3V to VDD + 0.3V
Input Voltage (ADR, SDA, SCL pins, relative to the I2CVDD pin)
-0.3V to I2CVDD + 0.3V
Power Dissipation (3)
Internally Limited
(4)
2000V
ESD Susceptibility
ESD Susceptibility (5)
200V
Junction Temperature
150°C
θJA
Thermal Resistance
(1)
(2)
(3)
(4)
(5)
109°C/W
All voltages are measured with respect to the GND pin unless otherwise specified.
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 ensure specific performance limits. Electrical Characteristics state DC and AC electrical
specifications under particular test conditions which ensure specific performance limits. This assumes that the device is within the
Operating Ratings. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indication
of device performance.
The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, θJA, and the ambient temperature,
TA. The maximum allowable power dissipation is PDMAX = (TJMAX - TA)/ θJA or the number given in Absolute Maximum Ratings,
whichever is lower. For the LM4985, see power derating currents for more information.
Human Body Model: 100pF discharged through a 1.5kΩ resistor.
Machine Model: 200pF ≤ Cmm ≤ 220pF discharged through all pins.
Operating Ratings
TMIN ≤ TA ≤ TMAX
Temperature Range
−40°C ≤ T A ≤ 85°C
2.3V ≤ VCC ≤ 5.5V
VDD
Supply Voltage
2
1.7V ≤ I2CVDD ≤ 5.5V
I CVDD
Electrical Characteristics VDD = 5V (1) (2)
The following specifications apply for RL = 16Ω, f = 1kHz, and CB = 4.7µF unless otherwise specified. Limits apply to TA =
25°C.
Symbol
IDD
Parameter
Conditions
Quiescent Power Supply Current
LM4985
Typ (3)
Limit (4) (5)
VIN = 0V, IOUT = 0A
Single-Channel no load OCL
Single-Channel no load C-CUPL
Dual-Channel no load OCL
Dual-Channel no load C-CUPL
2
1.5
3
2.3
4.9
3.8
VSHUTDOWN = GND
0.1
Units
(Limits)
mA (max)
ISD
Shutdown Current
1.0
µA (max)
VSDIH
Logic Voltage Input High
3.5
V (min)
VSDIL
Logic Voltage Input Low
1.5
V (max)
(1)
(2)
(3)
(4)
(5)
4
All voltages are measured with respect to the GND pin unless otherwise specified.
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 ensure specific performance limits. Electrical Characteristics state DC and AC electrical
specifications under particular test conditions which ensure specific performance limits. This assumes that the device is within the
Operating Ratings. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indication
of device performance.
Typicals are measured at 25°C and represent the parametric norm.
Limits are specified to Texas Instruments' AOQL (Average Outgoing Quality Level).
Datasheet min/max specification limits are specified by design, test, or statistical analysis.
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Electrical Characteristics VDD = 5V(1)(2) (continued)
The following specifications apply for RL = 16Ω, f = 1kHz, and CB = 4.7µF unless otherwise specified. Limits apply to TA =
25°C.
Symbol
Parameter
Conditions
LM4985
Typ (3)
Limit (4) (5)
RLOAD = 16Ω OCL
135
115
RLOAD = 16Ω C-CUPL
135
RLOAD = 32Ω OCL
79
Units
(Limits)
THD ≤ 1%; fIN = 1kHz
PO
Output Power
RLOAD = 32Ω C-CUPL
80
THD+N
Total Harmonic Distortion + Noise
RLOAD = 16Ω
RLOAD = 16Ω
RLOAD = 32Ω
RLOAD = 32Ω
VON
Output Noise Voltage
VIN = AC GND, AV = 0dB, A-weighted
15
Power Supply Rejection Ratio
VRIPPLE = 200mVp-p (6)
fIN = 217Hz sinewave
OCL
C-CUPL
77
65
fIN = 1kHz sinewave
OCL
C-CUPL
77
65
Pout = 40mW. OCL
RLOAD = 16Ω
RLOAD= 32Ω
51
56
dB
Pout = 50mW. C-CUPL
RLOAD = 16Ω
RLOAD= 32Ω
58
68
dB
PSRR
Xtalk
Channel-to-channel Crosstalk
OCL, PO = 100mW
C-CUPL, PO = 100mW
OCL, PO = 60mW
C-CUPL, PO = 70mW
mW (min)
70
0.08
0.02
0.04
0.01
%
µV
57
dB (min)
60
CBYPASS= 4.7μF (7)
TWU
Wake Up Time form Shutdown
WT1 = 0, WT0 = 0
OCL
C-CUPL
75
285
WT1 = 0, WT0 = 1
OCL
C-CUPL
110
530
WT1 = 1, WT0 = 0
OCL
C-CUPL
180
1030
WT1 = 1, WT0 = 1
OCL
C-CUPL
320
2050
msec
RIN
Input Resistance
Stereo mode
Mono mode
20
10
kΩ
AVMIN
Minimum Gain
Code = 00000
–76
dB (min)
AVMAX
Maximum Gain
Code = 11111
18
dB (min)
ΔAV
Gain Accuracy per Step
18dB ≥ AV ≥ –44dB
–44dB ≥ AV > –76dB
±0.5
±1.0
dB
VOS
Output Offset Voltage
OCL
RLOAD = 32Ω
VIN = AC GND
2.0
(6)
(7)
20
mV (max)
10Ω terminated input.
The wake-up time (TWU) is calculated using the following formula; TWU = [CBYPASS (VDD) / 2 (IBYPASS)] + 40ms.
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Electrical Characteristics VDD = 3.6V (1) (2)
The following specifications apply for RL = 16Ω, f = 1kHz, and CB = 4.7µF unless otherwise specified. Limits apply to TA =
25°C.
Symbol
Parameter
Conditions
LM4985
Units
(Limits)
Typ (3)
Limit (4) (5)
Single-Channel no load OCL
1.8
3.1
Single-Channel no load C-CUPL
1.0
Dual-Channel no load OCL
2.1
Dual-Channel no load C-CUPL
2.3
3
VSHUTDOWN = GND
0.1
1.0
µA (max)
2.52
V (min)
1.08
V (max)
VIN = 0V, IOUT = 0A
IDD
Quiescent Power Supply Current
ISD
Shutdown Current
VSDIH
Logic Voltage Input High
VSDIL
Logic Voltage Input Low
4
mA (max)
THD+N < 1%, fIN = 1kHz
PO
Output Power
RLOAD = 16Ω OCL
68
RLOAD = 16Ω C-CUPL
70
RLOAD = 32Ω OCL
38
RLOAD = 32Ω C-CUPL
mW (min)
34
41
THD+N
Total Harmonic Distortion + Noise
RLOAD = 16Ω
RLOAD = 16Ω
RLOAD = 32Ω
RLOAD = 32Ω
VON
Output Noise Voltage
VIN = AC GND, AV = 0dB, A-weighted
15
Power Supply Rejection Ratio
VRIPPLE = 200mVp-p (6)
fIN = 217Hz sinewave
OCL
C-CUPL
77
63
fIN = 1kHz sinewave
OCL
C-CUPL
76
62
Pout = 40mW. OCL
RLOAD = 16Ω
RLOAD= 32Ω
51
56
dB
Pout = 50mW. C-CUPL
RLOAD = 16Ω
RLOAD= 32Ω
58
69
dB
PSRR
Xtalk
(1)
(2)
(3)
(4)
(5)
(6)
6
Channel-to-Channel Crosstalk
OCL, PO = 60mW
C-CUPL, PO = 60mW
OCL, PO = 33mW
C-CUPL, PO = 38mW
60
0.06
0.03
0.03
0.03
%
µV
55
dB (min)
57
All voltages are measured with respect to the GND pin unless otherwise specified.
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 ensure specific performance limits. Electrical Characteristics state DC and AC electrical
specifications under particular test conditions which ensure specific performance limits. This assumes that the device is within the
Operating Ratings. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indication
of device performance.
Typicals are measured at 25°C and represent the parametric norm.
Limits are specified to Texas Instruments' AOQL (Average Outgoing Quality Level).
Datasheet min/max specification limits are specified by design, test, or statistical analysis.
10Ω terminated input.
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Electrical Characteristics VDD = 3.6V(1)(2) (continued)
The following specifications apply for RL = 16Ω, f = 1kHz, and CB = 4.7µF unless otherwise specified. Limits apply to TA =
25°C.
Symbol
Parameter
Conditions
LM4985
Typ (3)
Limit (4) (5)
WT1 = 0, WT0 = 0
OCL
C-CUPL
66
222
93
WT1 = 0, WT0 = 1
OCL
C-CUPL
92
405
WT1 = 1, WT0 = 0
OCL
C-CUPL
143
774
WT1 = 1, WT0 =1
OCL
C-CUPL
246
1532
Units
(Limits)
CBYPASS= 4.7μF (7)
TWU
Wake Up Time from Shutdown
msec
RIN
Input Resistance
Stereo mode
Mono mode
20
10
AVMIN
Minimum Gain
Code = 00000
–76
–72
dB (max)
AVMAX
Maximum Gain
Code = 11111
18
17
dB (min)
ΔAV
Gain Accuracy per Step
18dB ≥ AV ≥–44dB
–44dB ≥ AV > –76dB
± 0.5
± 1.0
± 1.0
± 2.0
dB
VOS
Output Offset Voltage
OCL
RLOAD = 32Ω
VIN = AC GND
2.0
20
mV (max)
(7)
kΩ
The wake-up time (TWU) is calculated using the following formula; TWU = [CBYPASS (VDD) / 2 (IBYPASS)] + 40ms.
Electrical Characteristics VDD = 2.5V (1) (2)
The following specifications apply for RL = 16Ω, f = 1kHz, and CB = 4.7µF unless otherwise specified. Limits apply to TA =
25°C.
Symbol
Parameter
Conditions
LM4985
Typ (3)
Limit (4) (5)
Units
(Limits)
IDD
Quiescent Power Supply Current
VIN = 0V, IOUT = 0A
Single-Channel no load OCL
Single-Channel no load C-CUPL
Dual-Channel no load OCL
Dual-Channel no load C-CUPL
ISD
Shutdown Current
VSHUTDOWN = GND
VSDIH
Logic Voltage Input High
1.75
V (min)
VSDIL
Logic Voltage Input Low
0.75
V (max)
PO
(1)
(2)
(3)
(4)
(5)
Output Power
THD+N < 1%, fIN = 1kHz
RLOAD = 16Ω OCL
RLOAD = 16Ω C-CUPL
RLOAD = 32Ω OCL
RLOAD = 32Ω C-CUPL
1.6
1
2.1
1.6
0.1
mA
µA
31
33
19
19
mW
All voltages are measured with respect to the GND pin unless otherwise specified.
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 ensure specific performance limits. Electrical Characteristics state DC and AC electrical
specifications under particular test conditions which ensure specific performance limits. This assumes that the device is within the
Operating Ratings. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indication
of device performance.
Typicals are measured at 25°C and represent the parametric norm.
Limits are specified to Texas Instruments' AOQL (Average Outgoing Quality Level).
Datasheet min/max specification limits are specified by design, test, or statistical analysis.
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Electrical Characteristics VDD = 2.5V(1)(2) (continued)
The following specifications apply for RL = 16Ω, f = 1kHz, and CB = 4.7µF unless otherwise specified. Limits apply to TA =
25°C.
Symbol
Parameter
Conditions
LM4985
Typ (3)
THD+N
Total Harmonic Distortion + Noise
RLOAD = 16Ω
RLOAD = 16Ω
RLOAD = 32Ω
RLOAD = 32Ω
VON
Output Noise Voltage
Power Supply Rejection Ratio
PSRR
Xtalk
Channel-to-Channel Crosstalk
OCL, PO = 26mW
C-CUPL, PO = 20mW
OCL, PO = 16mW
C-CUPL, PO = 15mW
Limit (4) (5)
Units
(Limits)
0.07
0.05
0.06
0.04
%
VIN = AC GND, AV = 0dB, A-weighted
10
µV
VRIPPLE = 200mVp-p (6)
fIN = 217Hz sinewave
OCL
C-CUPL
75
59
dB
fIN = 1kHz sinewave
OCL
C-CUPL
75
59
Pout = 20mW, OCL
RLOAD = 16Ω
RLOAD= 32Ω
50
55
dB
Pout = 20mW. C-CUPL
RLOAD = 16Ω
RLOAD= 32Ω
58
67
dB
CBYPASS = 4.7µF (7)
TWU
Wake Up Time from Shutdown
WT1 = 0, WT0 = 0
OCL
C-CUPL
66
214
WT1 = 0, WT0 = 1
OCL
C-CUPL
92
544
WT1 = 1, WT0 = 0
OCL
C-CUPL
145
1053
WT1 = 1, WT0 = 1
OCL
C-CUPL
250
2098
msec
RIN
Input Resistance
Stereo mode
Mono mode
20
10
kΩ
AVMIN
Minimum Gain
Code = 00000
–76
dB
AVMAX
Maximum Gain
Code = 11111
ΔAV
Gain Accuracy per Step
18dB ≥ AV ≥ –44dB
–44dB ≥ AV > –76dB
VOS
Output Offset Voltage
OCL
RLOAD = 32Ω
VIN = AC GND
(6)
(7)
18
dB
± 0.5
± 1.0
dB
2.0
mV
10Ω terminated input.
The wake-up time (TWU) is calculated using the following formula; TWU = [CBYPASS (VDD) / 2 (IBYPASS)] + 40ms.
External Components Description
(See Figure 2)
Components
8
Functional Description
1.
CI
Input coupling capacitor which blocks the DC voltage at the amplifier's input terminals. Also creates a high-pass filter
with Ri at fc = 1/(2πRiCi). Refer to the section Proper Selection of External Components, for an explanation of how to
determine the value of Ci.
2.
CS
Supply bypass capacitor which provides power supply filtering. Refer to the POWER SUPPLY BYPASSING section for
information concerning proper placement and selection of the supply bypass capacitor.
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Components
Functional Description
3.
CB
Bypass pin capacitor which provides half-supply filtering. Refer to the section, POWER SUPPLY BYPASSING, for
information concerning proper placement and selection of CB
6.
Co
Output coupling capacitor which blocks the DC voltage at the amplifier's output. Forms a high pass filter with RL at fo =
1/(2πRLCo)
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Typical Performance Characteristics
TA = 25°C, AV = 0dB, fIN = 1kHz unless otherwise stated.
5
2
2
1
1
0.2
0.1
0.05
0.02
0.02
50 100 200 500 1k 2k
0.01
20
5k 10k 20k
Figure 5.
Figure 6.
THD+N vs Frequency
VDD = 5V, RL = 16Ω
POUT = 50mW, C-CUPL
THD+N vs Frequency
VDD = 2.5V, RL = 32Ω
POUT = 15mW, C-CUPL
10
2
2
1
1
0.5
0.2
0.5
0.2
0.1
0.1
0.05
0.05
0.02
0.02
50 100 200 500 1k 2k
0.01
20
5k 10k 20k
50 100 200 500 1k 2k
5k 10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 7.
Figure 8.
THD+N vs Frequency
VDD = 3.6V, RL = 32Ω
POUT = 35mW, C-CUPL
THD+N vs Frequency
VDD = 5.0V, RL = 32Ω
POUT = 60mW, C-CUPL
10
5
5
2
2
1
THD+N (%)
1
0.5
0.2
0.5
0.2
0.1
0.1
0.05
0.05
0.02
0.02
0.01
20
5k 10k 20k
FREQUENCY (Hz)
5
10
50 100 200 500 1k 2k
FREQUENCY (Hz)
5
0.01
20
THD+N (%)
0.2
0.1
10
10
0.5
0.05
0.01
20
THD+N (%)
THD+N (%)
5
0.5
THD+N vs Frequency
VDD = 3.6V, RL = 16Ω
POUT = 50mW, C-CUPL
10
THD+N (%)
THD+N (%)
10
THD+N vs Frequency
VDD = 2.5V, RL = 16Ω
POUT = 20mW, C-CUPL
50 100 200 500 1k 2k
5k 10k 20k
0.01
20
50 100 200 500 1k 2k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 9.
Figure 10.
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5k 10k 20k
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Typical Performance Characteristics (continued)
TA = 25°C, AV = 0dB, fIN = 1kHz unless otherwise stated.
10
THD+N vs Frequency
VDD = 2.5V, RL = 16Ω
POUT = 20mW, OCL
10
5
5
2
2
1
THD+N (%)
THD+N (%)
1
0.5
0.2
0.1
0.05
0.02
0.02
50 100 200 500 1k 2k
0.01
20
5k 10k 20k
Figure 11.
Figure 12.
THD+N vs Frequency
VDD = 5.0V, RL = 16Ω
POUT = 50mW, OCL
THD+N vs Frequency
VDD = 2.5V, RL = 32Ω
POUT = 15mW, OCL
10
5
2
2
THD+N (%)
1
0.5
0.2
0.5
0.2
0.1
0.1
0.05
0.05
0.02
0.02
10
50 100 200 500 1k 2k
0.01
20
5k 10k 20k
50 100 200 500 1k 2k
5k 10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 13.
Figure 14.
THD+N vs Frequency
VDD = 3.6V, RL = 32Ω
POUT = 35mW, OCL
THD+N vs Frequency
VDD = 5.0V, RL = 32Ω
POUT = 60mW, OCL
10
5
2
2
1
1
THD+N (%)
5
0.5
0.2
0.5
0.2
0.1
0.1
0.05
0.05
0.02
0.02
0.01
20
5k 10k 20k
FREQUENCY (Hz)
5
0.01
20
50 100 200 500 1k 2k
FREQUENCY (Hz)
1
THD+N (%)
0.2
0.1
10
THD+N (%)
0.5
0.05
0.01
20
THD+N vs Frequency
VDD = 3.6V, RL = 16Ω
POUT = 50mW, OCL
50 100 200 500 1k 2k
5k 10k 20k
0.01
20
50 100 200 500 1k 2k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 15.
Figure 16.
5k 10k 20k
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Typical Performance Characteristics (continued)
TA = 25°C, AV = 0dB, fIN = 1kHz unless otherwise stated.
THD+N vs Output Power
VDD = 2.5V, RL = 16Ω
C-CUPL
10
5
5
2
2
1
1
THD+N (%)
THD+N (%)
10
THD+N vs Output Power
VDD = 3.6V, RL = 16Ω
C-CUPL
0.5
0.2
0.5
0.2
0.1
0.1
0.05
0.05
0.02
0.02
0.01
10m
0.01
10m
20m
30m
50m
100m
20m
Figure 17.
Figure 18.
THD+N vs Output Power
VDD = 5.0V, RL = 16Ω
C-CUPL
THD+N vs Output Power
VDD = 2.5V, RL = 32Ω
C-CUPL
10
5
5
2
2
1
THD+N (%)
THD+N (%)
1
0.5
0.2
0.5
0.2
0.1
0.1
0.05
0.05
0.02
0.02
0.01
10m
0.01
30m 50m 70m
20m
40m 60m 100m
200m
6m 7m 8m 9m 10m
30m 40m
Figure 19.
Figure 20.
THD+N vs Output Power
VDD = 3.6V, RL = 32Ω
C-CUPL
THD+N vs Output Power
VDD = 5.0V, RL = 32Ω
C-CUPL
10
10
5
5
2
2
1
1
THD+N (%)
THD+N (%)
20m
OUTPUT POWER (W)
OUTPUT POWER (W)
0.5
0.2
0.1
0.5
0.2
0.1
0.05
0.05
0.02
0.02
0.01
10m
30m
20m
12
200m
OUTPUT POWER (W)
OUTPUT POWER (W)
10
30m 50m 70m
40m 60m 100m
40m
50m 70m 90m
60m 80m 100m
0.01
10m
20m 30m
50m
100m
OUTPUT POWER (W)
OUTPUT POWER (W)
Figure 21.
Figure 22.
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Typical Performance Characteristics (continued)
TA = 25°C, AV = 0dB, fIN = 1kHz unless otherwise stated.
THD+N vs Output Power
VDD = 2.5V, RL = 16Ω
OCL
THD+N vs Output Power
VDD = 3.6V, RL = 16Ω
OCL
10
10
5
5
2
2
THD+N (%)
0.2
0.2
0.1
0.05
0.05
0.02
0.02
2m
5m
10m 20m
0.01
1m
50m 100m
2m
5m
10m 20m
50m 100m
OUTPUT POWER (W)
OUTPUT POWER (W)
Figure 23.
Figure 24.
THD+N vs Output Power
VDD = 5.0V, RL = 16Ω
OCL
THD+N vs Output Power
VDD = 2.5V, RL = 32Ω
OCL
10
10
5
5
2
2
1
1
0.5
0.2
0.5
0.2
0.1
0.1
0.05
0.05
0.02
0.02
0.01
10m
20m
30m 50m 70m
40m 60m 100m
0.01
10m
200m
30m
20m
40m
50m 70m 100m
60m 80m
OUTPUT POWER (W)
OUTPUT POWER (W)
Figure 25.
Figure 26.
THD+N vs Output Power
VDD = 3.6V, RL = 32Ω
OCL
THD+N vs Output Power
VDD = 5.0V, RL = 32Ω
OCL
10
10
5
5
2
2
1
1
THD+N (%)
THD+N (%)
0.5
0.1
0.01
1m
THD+N (%)
1
THD+N (%)
THD+N (%)
1
0.5
0.5
0.2
0.5
0.2
0.1
0.1
0.05
0.05
0.02
0.02
0.01
10m
30m
20m
40m
50m 70m 100m
60m 80m
0.01
10m
20m
30m 50m 70m
40m 60m 100m
OUTPUT POWER (W)
OUTPUT POWER (W)
Figure 27.
Figure 28.
200m
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Typical Performance Characteristics (continued)
TA = 25°C, AV = 0dB, fIN = 1kHz unless otherwise stated.
-20
-20
-30
-30
-50
-60
-60
-80
-80
-90
-90
-100
20
-100
20
50 100 200 500 1k 2k
5k 10k 20k
5k 10k 20k
FREQUENCY (Hz)
Figure 29.
Figure 30.
PSRR vs Frequency
VDD = 5.0V, RL = 16Ω
VRIPPLE = 200mVpp, OCL
PSRR vs Frequency
VDD = 2.5V, RL = 32Ω
VRIPPLE = 200mVpp, OCL
+0
-10
-10
-20
-20
-30
-30
-40
-50
-60
-40
-50
-60
-70
-70
-80
-80
-90
-90
+0
50 100 200 500 1k 2k
FREQUENCY (Hz)
PSRR (dB)
PSRR (dB)
-50
-70
-100
20
PSRR (dB)
-40
-70
+0
14
PSRR (dB)
-10
-40
PSRR vs Frequency
VDD = 3.6V, RL = 16Ω
VRIPPLE = 200mVpp, OCL
+0
-10
50 100 200 500 1k 2k
-100
20
5k 10k 20k
50 100 200 500 1k 2k
5k 10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 31.
Figure 32.
PSRR vs Frequency
VDD = 3.6V, RL = 32Ω
VRIPPLE = 200mVpp, OCL
PSRR vs Frequency
VDD = 5.0V, RL = 32Ω
VRIPPLE = 200mVpp, OCL
+0
-10
-10
-20
-20
-30
-30
PSRR (dB)
PSRR (dB)
+0
PSRR vs Frequency
VDD = 2.5V, RL = 16Ω
VRIPPLE = 200mVpp, OCL
-40
-50
-60
-40
-50
-60
-70
-70
-80
-80
-90
-90
-100
20
-100
20
50 100 200 500 1k 2k
5k 10k 20k
50 100 200 500 1k 2k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 33.
Figure 34.
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SNAS346B – MAY 2006 – REVISED MAY 2006
Typical Performance Characteristics (continued)
TA = 25°C, AV = 0dB, fIN = 1kHz unless otherwise stated.
-20
-20
-30
-30
-40
-50
-60
-50
-60
-70
-80
-80
-90
-90
-100
20
-100
20
50 100 200 500 1k 2k
5k 10k 20k
50 100 200 500 1k 2k
5k 10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 35.
Figure 36.
PSRR vs Frequency
VDD = 5.0V, RL = 16Ω
VRIPPLE = 200mVpp, C-CUPL
PSRR vs Frequency
VDD = 2.5V, RL = 32Ω
VRIPPLE = 200mVpp, C-CUPL
+0
-10
-10
-20
-20
-30
-30
-40
-50
-60
-40
-50
-60
-70
-70
-80
-80
-90
-90
-100
20
-100
20
+0
PSRR vs Frequency
VDD = 3.6V, RL = 16Ω
VRIPPLE = 200mVpp, C-CUPL
-40
-70
PSRR (dB)
PSRR (dB)
PSRR (dB)
-10
+0
PSRR (dB)
+0
-10
50 100 200 500 1k 2k
5k 10k 20k
50 100 200 500 1k 2k
5k 10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 37.
Figure 38.
PSRR vs Frequency
VDD = 3.6V, RL = 32Ω
VRIPPLE = 200mVpp, C-CUPL
PSRR vs Frequency
VDD = 5.0V, RL = 32Ω
VRIPPLE = 200mVpp, C-CUPL
+0
-10
-10
-20
-20
-30
-30
PSRR (dB)
PSRR (dB)
+0
PSRR vs Frequency
VDD = 2.5V, RL = 16Ω
VRIPPLE = 200mVpp, C-CUPL
-40
-50
-60
-40
-50
-60
-70
-70
-80
-80
-90
-90
-100
20
-100
20
50 100 200 500 1k 2k
5k 10k 20k
50 100 200 500 1k 2k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 39.
Figure 40.
5k 10k 20k
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Typical Performance Characteristics (continued)
TA = 25°C, AV = 0dB, fIN = 1kHz unless otherwise stated.
+0
-5
-10
-15
-20
-25
-30
-35
-40
-45
-50
-55
-60
-65
-70
20
CROSSTALK (dB)
CROSSTALK (dB)
Crosstalk vs Frequency
VDD = 2.5V, RL = 16Ω
POUT = 20mW. OCL
50 100 200 500 1k 2k
5k 10k 20k
+0
-5
-10
-15
-20
-25
-30
-35
-40
-45
-50
-55
-60
-65
-70
20
Crosstalk vs Frequency
VDD = 3.6V, RL = 16Ω
POUT = 40mW, OCL
50 100 200 500 1k 2k
+0
-5
-10
-15
-20
-25
-30
-35
-40
-45
-50
-55
-60
-65
-70
20
Figure 42.
Crosstalk vs Frequency
VDD = 5.0V, RL = 16Ω
POUT = 40mW, OCL
Crosstalk vs Frequency
VDD = 2.5V, RL = 32Ω
POUT = 20mW, OCL
CROSSTALK (dB)
Figure 41.
50 100 200 500 1k 2k
5k 10k 20k
+0
-5
-10
-15
-20
-25
-30
-35
-40
-45
-50
-55
-60
-65
-70
20
50 100 200 500 1k 2k
5k 10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 43.
Figure 44.
Crosstalk vs Frequency
VDD = 3.6V, RL = 32Ω
POUT = 40mW, OCL
Crosstalk vs Frequency
VDD = 5.0V, RL = 32Ω
POUT = 50mW, OCL
CROSSTALK (dB)
CROSSTALK (dB)
CROSSTALK (dB)
16
+0
-5
-10
-15
-20
-25
-30
-35
-40
-45
-50
-55
-60
-65
-70
20
5k 10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
50 100 200 500 1k 2k
5k 10k 20k
+0
-5
-10
-15
-20
-25
-30
-35
-40
-45
-50
-55
-60
-65
-70
20
50 100 200 500 1k 2k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 45.
Figure 46.
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SNAS346B – MAY 2006 – REVISED MAY 2006
Typical Performance Characteristics (continued)
TA = 25°C, AV = 0dB, fIN = 1kHz unless otherwise stated.
-10
-20
-20
-30
-30
-40
-50
-60
-70
-80
-50
-60
-70
-80
-90
-100
20
-100
20
50 100 200 500 1k 2k
5k 10k 20k
5k 10k 20k
FREQUENCY (Hz)
Figure 47.
Figure 48.
Crosstalk vs Frequency
VDD = 5.0V, RL = 16Ω
POUT = 50mW, C-CUPL
Crosstalk vs Frequency
VDD = 2.5V, RL = 32Ω
POUT = 20mW, C-CUPL
+0
-10
-10
-20
-20
-30
-30
-40
-50
-60
-70
-80
-40
-50
-60
-70
-80
-90
-90
-100
20
-100
20
+0
50 100 200 500 1k 2k
FREQUENCY (Hz)
CROSSTALK (dB)
CROSSTALK (dB)
-40
-90
+0
50 100 200 500 1k 2k
5k 10k 20k
50 100 200 500 1k 2k
5k 10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 49.
Figure 50.
Crosstalk vs Frequency
VDD = 3.6V, RL = 32Ω
POUT = 50mW, C-CUPL
Crosstalk vs Frequency
VDD = 5.0V, RL = 32Ω
POUT = 50mW, C-CUPL
-40
-10
-44
-20
-48
CROSSTALK (dB)
CROSSTALK (dB)
Crosstalk vs Frequency
VDD = 3.6V, RL = 16Ω
POUT = 50mW, C-CUPL
+0
-10
CROSSTALK (dB)
CROSSTALK (dB)
+0
Crosstalk vs Frequency
VDD = 2.5V, RL = 16Ω
POUT = 20mW, C-CUPL
-30
-40
-50
-60
-70
-52
-56
-60
-64
-68
-72
-80
-90
-76
-100
20
-80
50 100 200 500 1k 2k
5k 10k 20k
30 50 100 200 500 1k 2k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 51.
Figure 52.
5k 10k 20k
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Typical Performance Characteristics (continued)
TA = 25°C, AV = 0dB, fIN = 1kHz unless otherwise stated.
Load Dissipation vs Amplifier Dissipation
VDD = 2.5V, C-CUPL
Load Dissipation vs Amplifier Dissipation
VDD = 3.6V, C-CUPL
0.5
0.25
RL = 16:
AMPLIFIER DISSIPATION (W)
AMPLIFIER DISSIPATION (W)
RL = 16:
0.20
1% THD+N
0.15
10% THD+N
0.10
RL = 32:
0.05
0.0
0.01
0.02
0.03
0.4
1% THD+N
0.3
0.2
RL = 32:
0.0
0.01
0.04
0.03
LOAD DISSIPATION (W)
Figure 54.
Load Dissipation vs Amplifier Dissipation
VDD = 5.0V, C-CUPL
Load Dissipation vs Amplifier Dissipation
VDD = 2.5V, OCL
0.7
1% THD+N
0.08
1% THD+N
0.06
0.04
RL = 32:
0.02
10% THD+N
0.0
0.01
AMPLIFIER DISSIPATION (W)
AMPLIFIER DISSIPATION (W)
0.09
LOAD DISSIPATION (W)
RL = 16:
0.6
RL = 16:
0.5
0.4
10% THD+N
0.3
RL = 32:
0.2
0.1
0.0
0.05
0.10
0.14
0.18
0.01
LOAD DISSIPATION (W)
0.02
0.04
Figure 56.
Load Dissipation vs Amplifier Dissipation
VDD = 3.6V, OCL
Load Dissipation vs Amplifier Dissipation
VDD = 5.0V, OCL
0.14
0.14
0.12 RL = 16:
0.12
1% THD+N
0.08
10% THD+N
0.06
RL = 32:
0.02
0.0
AMPLIFIER DISSIPATION (W)
1% THD+N
0.10
0.04
0.03
LOAD DISSIPATION (W)
Figure 55.
AMPLIFIER DISSIPATION (W)
0.07
0.05
Figure 53.
0.100
0.10
RL = 16:
0.08
10% THD+N
0.06
0.04
RL = 32:
0.02
0.0
0.01
0.03
0.05
0.07
0.01
LOAD DISSIPATION (W)
Figure 57.
18
10% THD+N
0.1
0.05
0.100
0.140
0.180
LOAD DISSIPATION (W)
Figure 58.
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Typical Performance Characteristics (continued)
TA = 25°C, AV = 0dB, fIN = 1kHz unless otherwise stated.
Output Power vs Load Resistance
VDD = 2.5V, C-CUPL
40
35
35
30
30
OUTPUT POWER (W)
OUTPUT POWER (W)
40
25
10% THD+N
20
15
1% THD+N
10
Output Power vs Load Resistance
VDD = 3.6V, C-CUPL
5
25
10% THD+N
20
15
1% THD+N
10
5
0
16
24
32
200
128
64
0
300
32
24
16
LOAD RESISTANCE (:)
300
Figure 59.
Figure 60.
Output Power vs Load Resistance
VDD = 5.0V, C-CUPL
Output Power vs Load Resistance
VDD = 2.5V, OCL
50
200
40
150
OUTPUT POWER (W)
OUTPUT POWER (W)
200
128
64
LOAD RESISTANCE (:)
10% THD+N
100
50
1% THD+N
30
10% THD+N
20
10
1% THD+N
0
16
24
32
64
200
128
0
16
300
24
32
Figure 61.
128
200
300
Figure 62.
Output Power vs Load Resistance
VDD = 3.6V, OCL
100
64
LOAD RESISTANCE (:)
LOAD RESISTANCE (:)
200
Output Power vs Load Resistance
VDD = 5.0V, OCL
OUTPUT POWER (W)
OUTPUT POWER (W)
80
60
10% THD+N
40
150
10% THD+N
100
50
20
1% THD+N
1% THD+N
0
16
24
32
64
128
200
300
0
16
24
32
64
128
200
LOAD RESISTANCE (:)
LOAD RESISTANCE (:)
Figure 63.
Figure 64.
300
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Typical Performance Characteristics (continued)
TA = 25°C, AV = 0dB, fIN = 1kHz unless otherwise stated.
200
200
OUTPUT POWER (mW)
OUTPUT POWER (mW)
250
Output Power vs Supply Voltage
RL = 16Ω, C-CUPL
150
10% THD+N
100
1% THD+N
50
Output Power vs Supply Voltage
RL = 32Ω, C-CUPL
150
10% THD+N
100
50
1% THD+N
0
0
2.3
2.5
3.0
3.5
4.0
4.5
5.0
5.5
2.3
2.5
VOLTAGE SUPPLY (V)
250
3.0
3.5
4.0
4.5
5.0
5.5
VOLTAGE SUPPLY (V)
Figure 65.
Figure 66.
Output Power vs Supply Voltage
RL = 16Ω, OCL
Output Power vs Supply Voltage
RL = 32Ω, OCL
100
90
OUTPUT POWER (mW)
OUTPUT POWER (mW)
200
150
10% THD+N
100
50
1% THD+N
80
70
10% THD+N
60
50
40
30
1% THD+N
20
10
0
0
2.3
2.5
3.0
3.5
4.0
4.5
5.0
5.5
2.3
2.5
VOLTAGE SUPPLY (V)
3.0
Figure 67.
3.5
Supply Current vs Supply Voltage
RL = 16Ω, C-CUPL
3.5
4.5
5.0
5.5
Supply Current vs Supply Voltage
RL = 32Ω, C-CUPL
3.0
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
4.0
Figure 68.
3.0
2.5
2.0
1.5
1.0
0.5
2.5
2.0
1.5
1.0
0.5
0.0
2.3
2.5
3.0
3.5
4.0
4.5
5.0
5.5
0.0
2.3
VOLTAGE SUPPLY (V)
Figure 69.
20
3.5
VOLTAGE SUPPLY (V)
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VOLTAGE SUPPLY (V)
Figure 70.
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Typical Performance Characteristics (continued)
TA = 25°C, AV = 0dB, fIN = 1kHz unless otherwise stated.
Supply Current vs Supply Voltage
RL = 32Ω, OCL
4.0
4.0
3.5
3.5
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
Supply Current vs Supply Voltage
RL = 16Ω, OCL
3.0
2.5
2.0
1.5
1.0
2.5
2.0
1.5
1.0
0.5
0.5
0.0
2.3
30
3.0
3.5
4.0
4.5
5.0
0.0
2.3
5.5
3.0
3.5
4.5
5.0
SUPPLY VOLTAGE (V)
Figure 71.
Figure 72.
Gain vs Volume Steps
VCC = 2.5V, RL = 16Ω, OCL
Gain vs Volume Steps
VCC = 3.6V, RL = 16Ω, OCL
30
20
20
10
10
0
0
-10
-10
-20
-30
5.5
-20
-30
-40
-40
-50
-50
-60
-60
-70
-70
-80
-80
0
3
6
0
9 12 15 18 21 24 27 30
3
6
VOLUME STEPS
30
9 12 15 18 21 24 27 30
VOLUME STEPS
Figure 73.
Figure 74.
Gain vs Volume Steps
VCC = 5V, RL = 16Ω, OCL
Gain vs Volume Steps
VCC = 2.5V, RL = 16Ω, C-CUPL
30
20
20
10
10
0
0
-10
-10
Av (dB)
Av (dB)
4.0
SUPPLY VOLTAGE (V)
Av (dB)
Av (dB)
3.0
-20
-30
-20
-30
-40
-40
-50
-50
-60
-60
-70
-70
-80
-80
0
3
6
9 12 15 18 21 24 27 30
0
3
VOLUME STEPS
Figure 75.
6
9 12 15 18 21 24 27 30
VOLUME STEPS
Figure 76.
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Typical Performance Characteristics (continued)
TA = 25°C, AV = 0dB, fIN = 1kHz unless otherwise stated.
Gain vs Volume Steps
VCC = 3.6V, RL = 16Ω, C-CUPL
40
20
20
0
0
Av (dB)
Av (dB)
40
-20
Gain vs Volume Steps
VCC = 5V, RL = 16Ω, C-CUPL
-20
-40
-40
-60
-60
-80
-80
0
3
6
9 12 15 18 21 24 27 30
0
3
6
VOLUME STEPS
VOLUME STEPS
Figure 77.
Figure 78.
Gain vs Volume Steps
VCC = 2.5V, RL = 32Ω, OCL
Gain vs Volume Steps
VCC = 3.6V, RL = 32Ω, OCL
30
20
20
10
10
0
0
-10
-10
Av (dB)
Av (dB)
30
9 12 15 18 21 24 27 30
-20
-30
-20
-30
-40
-40
-50
-50
-60
-60
-70
-70
-80
-80
0
3
6
0
9 12 15 18 21 24 27 30
3
6
VOLUME STEPS
VOLUME STEPS
Figure 79.
Figure 80.
Gain vs Volume Steps
VCC = 5V, RL = 32Ω, OCL
30
9 12 15 18 21 24 27 30
Gain vs Volume Steps
VCC = 2.5V, RL = 32Ω, C-CUPL
40
20
20
10
0
0
Av (dB)
Av (dB)
-10
-20
-30
-40
-20
-40
-60
-50
-80
-60
-70
-100
-80
0
3
6
9 12 15 18 21 24 27 30
0
3
VOLUME STEPS
Figure 81.
22
6
9 12 15 18 21 24 27 30
VOLUME STEPS
Figure 82.
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Typical Performance Characteristics (continued)
TA = 25°C, AV = 0dB, fIN = 1kHz unless otherwise stated.
Gain vs Volume Steps
VCC = 3.6V, RL = 32Ω, C-CUPL
40
20
20
0
0
Av (dB)
Av (dB)
40
-20
-20
-40
-40
-60
-60
-80
Gain vs Volume Steps
VCC = 5V, RL = 32Ω, C-CUPL
-80
0
3
6
9 12 15 18 21 24 27 30
0
3
VOLUME STEPS
Figure 83.
6
9 12 15 18 21 24 27 30
VOLUME STEPS
Figure 84.
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APPLICATION INFORMATION
AMPLIFIER CONFIGURATION EXPLANATION
As shown in Figure 1, the LM4985 has three internal power amplifiers. Two of the amplifiers which amplify
signals applied to their inputs, have internally configurable gain. The remaining third amplifier provides both halfsupply output bias and AC ground return.
Loads, such as a headphone speaker, are connected between OUT1 and CNTGND or OUT2 and CNTGND.
This configuration does not require an output coupling capacitor. The classical single-ended amplifier
configuration, where one side of the load is connected to ground, requires large, expensive output coupling
capacitors.
A configuration such as the one used in the LM4985 has a major advantage over single supply, single-ended
amplifiers. Since the outputs OUT1, OUT2, and CNTGND are all biased at 1/2 VDD, no net DC voltage exists
across each load. This eliminates the need for output coupling capacitors which are required in a single-supply,
single-ended amplifier configuration. Without output coupling capacitors in a typical single-supply, single-ended
amplifier, the bias voltage is placed across the load resulting in both increased internal IC power dissipation and
possible loudspeaker damage.
The LM4985 eliminates these output coupling capacitors when operating in Output Capacitor-less (OCL) mode.
Unless shorted to ground, VoC is internally configured to apply a 1/2 VDD bias voltage to a stereo headphone
jack's sleeve. This voltage matches the bias voltage present on VoA and VoB outputs that drive the headphones.
The headphones operate in a manner similar to a bridge-tied load (BTL). Because the same DC voltage is
applied to both headphone speaker terminals this results in no net DC current flow through the speaker. AC
current flows through a headphone speaker as an audio signal's output amplitude increases on the speaker's
terminal.
The headphone jack's sleeve is not connected to circuit ground when used in OCL mode. Using the headphone
output jack as a line-level output will place the LM4985's 1/2 VDD bias voltage on a plug's sleeve connection. This
presents no difficulty when the external equipment uses capacitively coupled inputs. For the very small minority
of equipment that is DC coupled, the LM4985 monitors the current supplied by the amplifier that drives the
headphone jack's sleeve. If this current exceeds 500mAPEAK, the amplifier is shutdown, protecting the LM4985
and the external equipment.
POWER DISSIPATION
Power dissipation is a major concern when using any power amplifier. When operating in capacitor-coupled
mode (C-CUPL), Equation 1 states the maximum power dissipation point for a single-ended amplifier operating
at a given supply voltage and driving a specified output load.
PDMAX = 2(VDD) 2 / (2π2RL)
(1)
When operating in the OCL mode, the LM4985's three operational amplifiers produce a maximum power
dissipation given in Equation 2:
PDMAX = [2(VDD) 2 / (2π2RL)] + [VDD2 / (4πRL)]
(2)
The maximum power dissipation point obtained from Equation 1 or Equation 2 must not be greater than the
power dissipation that results from Equation 3:
PDMAX = (TJMAX - TA) / θJA
(3)
For package YFQ0012, θJA = 190°C/W. TJMAX = 150°C for the LM4985. Depending on the ambient temperature,
TA, of the system surroundings, Equation 3 can be used to find the maximum internal power dissipation
supported by the IC packaging. If the result of Equation 2 is greater than that of Equation 3, then either the
supply voltage must be decreased, the load impedance increased or TA reduced.
For a typical application using a 3.6V power supply, with a 32Ω load, the maximum ambient temperature possible
without violating the maximum junction temperature is approximately 144°C provided that device operation is
around the maximum power dissipation point. Thus, for typical applications, power dissipation is not an issue.
Power dissipation is a function of output power and thus, if typical operation is not around the maximum power
dissipation point, the ambient temperature may be increased accordingly. Refer to the Typical Performance
Characteristics curves for power dissipation information for lower output powers.
24
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POWER SUPPLY BYPASSING
As with any amplifier, proper supply bypassing is important for low noise performance and high power supply
rejection. The capacitor location on the power supply pins should be as close to the device as possible.
Typical applications employ a regulator with 10µF tantalum or electrolytic capacitor and a ceramic bypass
capacitor which aid in supply stability. This does not eliminate the need for bypassing the supply nodes of the
LM4985. A bypass capacitor value in the range of 0.1µF to 1µF is recommended for CS.
MICRO POWER SHUTDOWN
The LM4985's micropower shutdown is activated or deactivated through its I2C digital interface . Please refer to
Table 1 for the I2C Address, Register Select, and Mode Control registers. Each amplifier within the LM4985 can
be shutdown individually.
Please observe the following protocol when placing an individual amplifier channel in shutdown while the other
channel remains active. The protocol requires activating both channels’ shutdown simultaneously, then
deactivating the shutdown of the channel whose output is desired (or leaving the desire channel in shutdown
mode). Also, when operating in the C-CUPL mode, a short delay time is required between activating one channel
after placing both channels in shutdown. If the user finds that both channels activate when only one was chosen,
increase the delay.
SELECTION OF INPUT CAPACITOR SIZE
Amplifying the lowest audio frequencies requires a high value input coupling capacitor, Ci. A high value capacitor
can be expensive and may compromise space efficiency in portable designs. In many cases, however, the
headphones used in portable systems have little ability to reproduce signals below 60Hz. Applications using
headphones with this limited frequency response reap little improvement by using a high value input capacitor.
In addition to system cost and size, turn on time is affected by the size of the input coupling capacitor Ci. A larger
input coupling capacitor requires more charge to reach its quiescent 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. A small value of Ci (in the range of 0.22µF to 0.68µF), is recommended.
MAXIMIZING OCL MODE CHANNEL-to-CHANNEL SEPARATION
The OCL mode AC ground return (CNT_GND pin) is shared by both amplifiers. As such, any resistance between
the CNT_GND pin and the load will create a voltage divider with respect to the load resistance. In a typical
circuit, the amount of CNT_GND resistance can be very small, but still significant. It is significant because of the
relatively low load impedances for which the LM4985 was designed to drive: 16Ω to 32Ω. The ratio of this
voltage divider will determine the magnitude of any residual signal present at the CNT_GND pin. It is this residual
signal that leads to channel-to-channel separation (crosstalk) degradation.
For example, for a 60dB channel-to-channel separation while driving a 16Ω load, the resistance between the
LM4985’s CNT_GND pin and the load must be less than 16mΩ. This is achieved by ensuring that the trace that
connects the CNT_GND pin to the headphone jack sleeve should be as short and massive as possible, given the
physical constraints of any specific printed circuit board layout and design.
DEMONSTRATION BOARD AND PCB LAYOUT
Information concerning PCB layout considerations and demonstration board use and performance is found in
Application Note AN-1452.
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I2C Control Register
Table 1 shows the actions that are implemented by manipulating the bits within the two internal I2C control
registers.
Table 1. LM4985 I2C Control Register Addressing and Data Format Chart
LM4985 I2C Contorl Register Addressing and Data Chart
A6
A5
A4
A3
A2
A1
A0
1
1
0
0
1
1
A0
D7
D6
D5
D4
D3
D2
RS1
RS0
0
0
0
0
0
0
0
0
Read and write the mode control
register
0
0
0
0
0
0
0
1
Read and write the volume
control register
I2C Address
Register
Select
D7
Mode
Control
Register
26
Function
D6
D5
D4
D3
D2
D1
D0
WT1
WT0
PHG
SDCH1
SDCH2
CHSEL1
CHSEL2
0
X
X
X
X
X
X
X
D7 must always be set to 0
–
0
0
X
X
X
X
X
Wake-up time: 80ms (OCL),
250ms (C-CUPL)
–
0
1
X
X
X
X
X
Wake-up time: 110ms (OCL),
450ms (C-CUPL)
–
1
0
X
X
X
X
X
Wake-up time: 170ms (OCL),
850ms (C-CUPL)
–
1
1
X
X
X
X
X
Wake-up time: 290ms (OCL),
1650ms (C-CUPL)
–
X
X
1
X
X
X
X
Output capacitor-less mode
active
–
X
X
0
X
X
X
X
Output capacitor-less mode
inactive
–
X
X
X
0
0
X
X
Amplifier's SHUTDOWN mode
active
–
X
X
X
0
1
X
X
Illegal mode
–
X
X
X
1
0
X
X
Illegal mode
–
X
X
X
1
1
X
X
Amplifier's SHUTDOWN mode
inactive
–
X
X
X
X
X
0
02
Amplifier's Chan. 1 is Input 1,
Chan 2. is Input 2
–
X
X
X
X
X
0
1
Amplifier's Chan. 1 is Input 1,
Chan 2. is Input 1
–
X
X
X
X
X
1
0
Amplifier's Chan. 1 is Input 2,
Chan 2. is Input 2
–
X
X
X
X
X
1
1
Amplifier's Chan. 1 is Input 2,
Chan 2. is Input 1
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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.
Table 2 shows the value of the gain for each of the 32 binary volume control settings.
Table 2. Binary Values for the Different Volume Control Gain Settings
Gain
B4
B3
B2
B1
B0
18
1
1
1
1
1
17
1
1
1
1
0
16
1
1
1
0
1
15
1
1
1
0
0
14
1
1
0
1
1
13
1
1
0
1
0
12
1
1
0
0
1
10
1
1
0
0
0
8
1
0
1
1
1
6
1
0
1
1
0
4
1
0
1
0
1
2
1
0
1
0
0
0
1
0
0
1
1
–2
1
0
0
1
0
–4
1
0
0
0
1
–6
1
0
0
0
0
–8
0
1
1
1
1
–10
0
1
1
1
0
–12
0
1
1
0
1
–14
0
1
1
0
0
–16
0
1
0
1
1
–18
0
1
0
1
0
–21
0
1
0
0
1
–24
0
1
0
0
0
–27
0
0
1
1
1
–30
0
0
1
1
0
–34
0
0
1
0
1
–38
0
0
1
0
0
–44
0
0
0
1
1
–52
0
0
0
1
0
–62
0
0
0
0
1
–76
0
0
0
0
0
Revision History
Rev
Date
Description
1.0
05/17/06
Initial WEB release.
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27
PACKAGE OPTION ADDENDUM
www.ti.com
24-Jan-2013
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package Qty
Drawing
Eco Plan
Lead/Ball Finish
(2)
MSL Peak Temp
Op Temp (°C)
Top-Side Markings
(3)
(4)
LM4985TM/NOPB
ACTIVE
DSBGA
YFQ
12
250
Green (RoHS
& no Sb/Br)
SNAGCU
Level-1-260C-UNLIM
-40 to 85
G
H2
LM4985TMX/NOPB
ACTIVE
DSBGA
YFQ
12
3000
Green (RoHS
& no Sb/Br)
SNAGCU
Level-1-260C-UNLIM
-40 to 85
G
H2
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
Only one of markings shown within the brackets will appear on the physical device.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 1
Samples
PACKAGE MATERIALS INFORMATION
www.ti.com
14-Mar-2013
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
LM4985TM/NOPB
DSBGA
YFQ
12
250
178.0
8.4
LM4985TMX/NOPB
DSBGA
YFQ
12
3000
178.0
8.4
Pack Materials-Page 1
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
1.35
1.75
0.76
4.0
8.0
Q1
1.35
1.75
0.76
4.0
8.0
Q1
PACKAGE MATERIALS INFORMATION
www.ti.com
14-Mar-2013
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
LM4985TM/NOPB
DSBGA
YFQ
LM4985TMX/NOPB
DSBGA
YFQ
12
250
210.0
185.0
35.0
12
3000
210.0
185.0
35.0
Pack Materials-Page 2
MECHANICAL DATA
YFQ0012xxx
D
0.600
±0.075
E
TMD12XXX (Rev B)
D: Max = 1.66 mm, Min = 1.56 mm
E: Max = 1.26 mm, Min = 1.16 mm
4215079/A
NOTES:
A. All linear dimensions are in millimeters. Dimensioning and tolerancing per ASME Y14.5M-1994.
B. This drawing is subject to change without notice.
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12/12
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