19-3134; Rev 2; 4/08
EVALUATION KIT
AVAILABLE
1.2W, Low-EMI, Filterless, Mono Class D Amplifier
with Stereo DirectDrive Headphone Amplifiers
General Description
The MAX9770 combines a mono, filterless, Class D
speaker amplifier and stereo DirectDrive
®
headphone
amplifier in a single device. The MAX9770 operates
from a single 2.5V to 5.5V supply and includes features
that reduce external component count, system cost,
board space, and offer improved audio reproduction.
The speaker amplifier makes use of Maxim’s Class D
architecture, providing Class AB performance with Class
D efficiency, conserving board space, and extending
battery life. The speaker amplifier delivers 1.2W into an
8Ω load while offering efficiencies above 85%. A spread-
spectrum modulation scheme reduces radiated emis-
sions caused by the modulation frequency. Furthermore,
the MAX9770 oscillator can be synchronized to an exter-
nal clock through the SYNC input, avoiding possible
problem frequencies inside a system. The speaker
amplifier features THD+N as low as 0.025%, high 70dB
PSRR, and SNR in excess of 90dB.
The headphone amplifiers feature Maxim’s DirectDrive
architecture that produces a ground-referenced output
from a single supply, eliminating the need for large DC-
blocking capacitors. The headphone amplifiers deliver up
to 80mW into a 16Ω load, feature low 0.015% THD+N,
high 85dB PSRR, and
±8kV
ESD-protected outputs. A
headphone sense input detects the presence of a head-
phone, and automatically configures the amplifiers for
either speaker or headphone mode.
The MAX9770 includes internally set, logic-selectable
gain, and a comprehensive input multiplexer/mixer, allow-
ing multiple audio sources to be selected and for true
mono reproduction of a stereo source in speaker mode.
Industry-leading click-and-pop suppression eliminates
audible transients during power and shutdown cycles. A
low-power shutdown mode decreases supply current
consumption to 0.1µA, further extending battery life.
The MAX9770 is offered in space-saving, thermally effi-
cient 28-pin TQFN (5mm x 5mm x 0.8mm) and 28-pin
TSSOP packages. The MAX9770 features thermal-over-
load and output short-circuit protection, and is speci-
fied over the extended -40°C to +85°C temperature
range.
Features
♦
1.2W Filterless Class D Amplifiers Pass FCC
Class B Radiated EMI Standards with 100mm
of Cable
♦
Spread-Spectrum Mode Offers 5dB EMI
Improvement over Conventional Methods
♦
80mW DirectDrive Headphone Amplifier
Eliminates Bulky DC-Blocking Capacitors
♦
High 85dB PSRR at 217Hz
♦
85% Efficiency
♦
Low 0.015% THD+N
♦
Industry-Leading Click-and-Pop Suppression
♦
Integrated 3-Way Input Mixer/Multiplexer
(MAX9770)
♦
Logic-Adjustable Gain
♦
Short-Circuit and Thermal Protection
♦
Available in Space-Saving, Thermally Efficient
Packages
MAX9770
Ordering Information
PART
MAX9770ETI+
PIN-PACKAGE
28 TQFN-EP*
SELECTABLE INPUTS
2 stereo, 1 mono
2 stereo, 1 mono
MAX9770EUI
28 TSSOP
Note:
All devices specified over the -40°C to +85°C operating
temperature range.
*EP
= Exposed pad.
+
Denotes a lead-free package.
Pin Configuration appears at end of data sheet.
Simplified Block Diagram
V
DD
DirectDrive
STEREO
HEADPHONE
IN1L
IN2L
MONO
IN1R
IN2R
GAIN SEL
INPUT SEL
MUTE
SHDN
HPS
CLASS
D
SPKR
(MONO)
Applications
Cellular Phones
Compact Notebooks
PDAs
MAX9770
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim's website at www.maxim-ic.com.
1.2W, Low-EMI, Filterless, Mono Class D Amplifier
with Stereo DirectDrive Headphone Amplifiers
MAX9770
ABSOLUTE MAXIMUM RATINGS
GND to PGND to CPGND......................................-0.3V to +0.3V
V
DD
to PV
DD
to CPV
DD
..........................................-0.3V to +0.3V
V
DD
to GND ...........................................................................+6V
PV
DD
to PGND .......................................................................+6V
CPV
DD
to CPGND..................................................................+6V
CPV
SS
to CPGND....................................................................-6V
SV
SS
to GND ...........................................................................-6V
C1N..........................................(PV
SS
- 0.3V) to (CPGND + 0.3V)
HPOUT_ to GND ....................................................................±3V
All Other Pins to GND.................................-0.3V to (V
DD
+ 0.3V)
Continuous Current Into/Out of:
PV
DD
, PGND, OUT_ ......................................................600mA
PV
SS
..............................................................................260mA
Duration of HPOUT_ Short Circuit to V
DD
, PV
DD
,
GND, PGND ...........................................................Continuous
Duration of Short Circuit Between
HPOUTL and HPOUTR ..........................................Continuous
Duration of OUT_ Short Circuit to V
DD
, PV
DD
, GND, PGND ..10s
Duration of Short Circuit Between OUT+ and OUT-...............10s
Continuous Power Dissipation (T
A
= +70°C)
28-Pin TQFN (derate 20.8mW/°C above +70°C) .......1667mW
28-Pin TSSOP (derate 12.8mW°C above +70°C) ......1026mW
Junction Temperature ......................................................+150°C
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
DD
= PV
DD
= CPV
DD
= 3.3V, GND = PGND = CPGND = 0V,
SHDN
= 3.3V, C1 = C2 = 1µF, C
BIAS
= 0.047µF, SYNC = GND, R
L
=
∞,
speaker load connected between OUT+ and OUT-, headphone load connected between HPOUT_ and GND, T
A
= T
MIN
to T
MAX
,
unless otherwise noted. Typical values are at T
A
= +25°C.) (Notes 1, 2)
PARAMETER
GENERAL
Supply Voltage Range
Quiescent Supply Current
Shutdown Supply Current
Shutdown to Full Operation
Input Impedance
Bias Voltage
Feedthrough
V
DD
I
DD
I
SHDN
t
ON
R
IN
V
BIAS
From any unselected input to any output,
f = 10kHz
V
OS
V
DD
= 2.5V to 5.5V,
T
A
= +25°C
Power-Supply Rejection Ratio
PSRR
(Note 4)
V
RIPPLE
= 200mV
P-P
, f = 217Hz
V
RIPPLE
= 200mV
P-P
, f = 1kHz
V
RIPPLE
= 200mV
P-P
, f = 20kHz
f = 1kHz,
THD+N = 1%,
GAIN1 = 1,
GAIN2 = 0
V
DD
= 3.3V
V
DD
= 5V
R
L
= 8Ω
R
L
= 4Ω
R
L
= 8Ω
50
(Note 3)
MONO
INL_, INR_
7
14
1.1
Inferred from PSRR test
No load
SHDN
= HPS = GND
Headphone mode
Speaker mode
2.5
5.5
5.2
0.1
50
10
20
1.25
70
1.4
5.5
10
7.5
10
V
mA
µA
ms
kΩ
V
dB
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SPEAKER AMPLIFIER (GAIN1 = GAIN2 = V
DD
, HPS = GND)
Output Offset Voltage
±15
70
70
68
50
550
900
1200
mW
dB
±70
mV
Output Power
P
OUT
2
_______________________________________________________________________________________
1.2W, Low-EMI, Filterless, Mono Class D Amplifier
with Stereo DirectDrive Headphone Amplifiers
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= PV
DD
= CPV
DD
= 3.3V, GND = PGND = CPGND = 0V,
SHDN
= 3.3V, C1 = C2 = 1µF, C
BIAS
= 0.047µF, SYNC = GND, R
L
=
∞,
speaker load connected between OUT+ and OUT-, headphone load connected between HPOUT_ and GND, T
A
= T
MIN
to T
MAX
,
unless otherwise noted. Typical values are at T
A
= +25°C.) (Notes 1, 2)
PARAMETER
Total Harmonic Distortion Plus
Noise
Signal-to-Noise Ratio
SYMBOL
CONDITIONS
R
L
= 8Ω, P
OUT
= 300mW, f = 1kHz
THD+N
R
L
= 4Ω, P
OUT
= 300mW, f = 1kHz
R
L
= 8Ω, P
OUT
= 500mW,
f = 1kHz
R
L
= 8Ω, V
OUT
= 2V
RMS
, A-weighted
SYNC = GND
Output Switching Frequency
f
S
SYNC = unconnected
SYNC = V
DD
SYNC Frequency Lock Range
Efficiency
η
P
O
= 1000mW, f = 1kHz
GAIN1 = 0, GAIN2 = 0
Gain (MAX9770)
A
V
GAIN1 = 0, GAIN2 = 1
GAIN1 = 1, GAIN2 = 0
GAIN1 = 1, GAIN2 = 1
Gain Accuracy
Speaker Path Off-Isolation
HPS = V
DD
, headphone amplifier active,
f = 1kHz
Peak voltage,
A-weighted, 32
samples per second
(Notes 4, 5)
Into shutdown
Out of shutdown
Into mute
Out of mute
102
-76
-55
-83
-69
±5
V
DD
= 2.5V to 5.5V, T
A
= +25°C
Power-Supply Rejection Ratio
PSRR
(Note 4)
V
RIPPLE
= 200mV
P-P
, f = 217Hz
V
RIPPLE
= 200mV
P-P
, f = 1kHz
V
RIPPLE
= 200mV
P-P
, f = 20kHz
T
A
= +25°C,
f = 1kHz,
THD+N = 1%
(Note 3)
V
DD
= 3.3V
V
DD
= 5V
R
L
= 32Ω
R
L
= 16Ω
R
L
= 32Ω
R
L
= 16Ω
40
65
76
75
82
56
55
40
60
80
0.015
0.03
%
mW
dB
±10
800
85
6
3
9
0
±5
%
dB
dB
980
1280
MIN
TYP
0.025
0.03
0.1
85.9
1100
1450
1220
±120kHz
2000
kHz
%
1220
1620
kHz
dB
%
MAX
UNITS
MAX9770
SNR
Click-and-Pop Level
K
CP
dB
HEADPHONE AMPLIFIER (GAIN1 = 1, GAIN2 = 0, HPS = V
DD
)
Output Offset Voltage
V
OS
mV
Output Power
P
OUT
Total Harmonic Distortion Plus
Noise
THD+N
R
L
= 32Ω, P
OUT
= 50mW, f = 1kHz
R
L
= 16Ω, P
OUT
= 35mW, f = 1kHz
_______________________________________________________________________________________
3
1.2W, Low-EMI, Filterless, Mono Class D Amplifier
with Stereo DirectDrive Headphone Amplifiers
MAX9770
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= PV
DD
= CPV
DD
= 3.3V, GND = PGND = CPGND = 0V,
SHDN
= 3.3V, C1 = C2 = 1µF, C
BIAS
= 0.047µF, SYNC = GND, R
L
=
∞,
speaker load connected between OUT+ and OUT-, headphone load connected between HPOUT_ and GND, T
A
= T
MIN
to T
MAX
,
unless otherwise noted. Typical values are at T
A
= +25°C.) (Notes 1, 2)
PARAMETER
Signal-to-Noise Ratio
Crosstalk
Headphone Off-Isolation
SYMBOL
SNR
CONDITIONS
R
L
= 32Ω, V
OUT
= 300mV
RMS
,
BW = 22Hz to 22kHz
Between channels, f = 1kHz,
V
IN
= 200mV
P-P
HPS = GND, speaker amplifier active,
f = 1kHz
Peak voltage, A-
weighted, 32
samples per second
(Notes 4, 5)
GAIN1 = 0, GAIN2 = 0
Gain
A
V
GAIN1 = 0, GAIN2 = 1
GAIN1 = 1, GAIN2 = 0
GAIN1 = 1, GAIN2 = 1
Gain Accuracy
ESD Protection
Input Voltage High
Input Voltage Low
Input Leakage Current (Note 6)
HPS Input Current
V
IH
V
IL
SYNC input
All other logic inputs
HPS = GND
HPOUTR, HPOUTL, IEC Air Discharge
2
0.8
±25
±1
-10
±8
DIGITAL INPUTS (SHDN, SYNC, HPS, GAIN_, SEL_)
V
V
µA
µA
Into shutdown
Out of shutdown
Into mute
Out of mute
MIN
TYP
101
80
96
-58
-53
-92
-73
1000
7
4
-2
1
±2.5
%
kV
dB
MAX
UNITS
dB
dB
dB
Click-and-Pop Level
K
CP
dBV
Capacitive-Load Drive
C
L
pF
Note 1:
All devices are 100% production tested at +25°C. All temperature limits are guaranteed by design.
Note 2:
Speaker amplifier testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For
R
L
= 4Ω, L = 47µH. For R
L
= 8Ω, L = 68µH.
Note 3:
Guaranteed by design, not production tested.
Note 4:
Inputs AC-coupled to GND.
Note 5:
Speaker mode testing performed with an 8Ω resistive load in series with a 68µH inductive load connected across BTL output.
Headphone mode testing performed with a 32Ω resistive load connected to GND. Mode transitions are controlled by
SHDN.
K
CP
level is calculated as: 20 x log [(peak voltage during mode transition, no input signal)/(peak voltage under normal operation at
rated power level)]. Units are expressed in dB. Measured with V
DD
= 5V.
Note 6:
SYNC has a 200kΩ resistor to V
REF
= 1.25V.
4
_______________________________________________________________________________________
1.2W, Low-EMI, Filterless, Mono Class D Amplifier
with Stereo DirectDrive Headphone Amplifiers
Typical Operating Characteristics
(V
DD
= 3.3V, BW = 22Hz to 22kHz, GAIN1 = 1, GAIN2 = 0, spread-spectrum mode, headphone outputs in phase, unless otherwise
noted.)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (SPEAKER MODE)
MAX9770 toc01
MAX9770
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (SPEAKER MODE)
MAX9770 toc02
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (SPEAKER MODE)
R
L
= 8Ω
MAX9770 toc03
10
V
DD
= +5V
R
L
= 4Ω
1
THD+N (%)
P
OUT
= 25mW
0.1
10
R
L
= 4Ω
10
1
THD+N (%)
THD+N (%)
P
OUT
= 100mW
0.1
1
P
OUT
= 40mW
0.1
0.01
P
OUT
= 1000mW
0.01
P
OUT
= 500mW
0.01
P
OUT
= 400mW
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (SPEAKER MODE)
MAX9770 toc04
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (SPEAKER MODE)
MAX9770 toc05
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (SPEAKER MODE)
R
L
= 4Ω
10
MAX9770 toc06
10
V
DD
= 5V
P
OUT
= 1W
R
L
= 8Ω
1
THD+N (%)
100
V
DD
= 5V
R
L
= 8Ω
10
100
THD+N (%)
THD+N (%)
1
f = 1kHz
0.1
f = 20Hz
1
f = 1kHz
f = 20Hz
0.1
0.1
SSM MODE
0.01
FFM MODE
0.01
0.001
f = 10kHz
0.01
0.001
0
200
f = 10kHz
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
0
400
800
1200
1600
OUTPUT POWER (mW)
800
600
400
OUTPUT POWER (mW)
1000
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (SPEAKER MODE)
MAX9770 toc07
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (SPEAKER MODE)
MAX9770 toc08
OUTPUT POWER
vs. LOAD RESISTANCE (SPEAKER MODE)
1.50
OUTPUT POWER (W)
1.25
1.00
0.75
0.50
0.25
0
THD+N = 1%
V
DD
= 5V
f = 1kHz
THD+N = 10%
MAX9770 toc09
100
R
L
= 8Ω
10
100
V
DD
= 5V
f = 1kHz
R
L
= 8Ω
1.75
10
THD+N (%)
1
f = 20Hz
THD+N (%)
f = 1kHz
1
SSM MODE
0.1
0.1
0.01
f = 10kHz
0.001
0
200
400
600
800
OUTPUT POWER (mW)
0.01
FFM MODE
0.001
0
400
800
1200
1600
OUTPUT POWER (mW)
1
10
LOAD RESISTANCE (Ω)
100
_______________________________________________________________________________________
5
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