19-1743; Rev 1; 2/01
Ultra-High PSRR Stereo Drivers +
Microphone Amp + 100mA Linear Regulator
The MAX4298 and MAX4299 are audio system ICs
designed for single +5V applications. The MAX4299
features a stereo headphone driver, a microphone
amplifier, and a +3.3V linear regulator; the MAX4298
features the stereo headphone driver only. The
MAX4298/ MAX4299 are designed specifically for harsh
digital environments where board space is at a premium and the digital power supply is noisy. The design
uses innovative design techniques to achieve ultra-high
power-supply rejection across the audio signal band
while, at the same time, delivering a high-current Railto-Rail® output drive capability. The chip is designed to
drive highly capacitive loads that may be encountered
when driving long cables to a remote load such as
desktop/notebook headphones or speakers. These
devices are fully compliant with PC99 standards.
The amplifiers exhibit 115dB of DC power-supply rejection and 80dB at 100kHz. The output amplifiers are
capable of driving a 1.5VRMS signal into a 10kΩ load
with 0.0008% THD+N. They can also drive 32Ω headphones to 1.2VRMS with 0.02% distortion. At +3.3V, the
linear regulator can output 100mA of current. The
MAX4298 is available in a tiny 10-pin µMAX while the
MAX4299 is available in the space-saving 16-pin
TSSOP package.
Features
♦ Audio System IC (MAX4299)
Ultra-High PSRR Stereo Headphone Driver
Ultra-High PSRR Microphone Amp
100mA, 3.3V Linear Regulator
♦ 93dB typ PSRR at 20kHz Operates Directly from
Noisy Digital Supplies
♦ Clickless/Popless Power-Up, Power-Down, Mute
and Unmute
♦ PC99-Compliant Output Drivers:
Better than 1VRMS Output into 16Ω Load and
1.5VRMS and 0.0008% THD+N into 10kΩ Load
♦ PC99-Compliant Microphone Amplifier:
0.005% THD+N into 10kΩ Load
♦ 22nF Capacitive Load Drive Capability
♦ 4.5V to 5.5V Single-Supply Operation
♦ Internally Generated Bias Voltage
♦ All Gains Externally Adjustable
♦ Available in Space-Saving Packages
10-Pin µMAX (MAX4298)
16-Pin TSSOP (MAX4299)
Ordering Information
________________________Applications
Notebook and Desktop Audio
Hands-Free Headsets
USB Audio Peripherals
IP Telephones
Wireless Internet Devices
MP3 Players/Recorders
PART
TEMP. RANGE
PIN-PACKAGE
MAX4298EUB
-40ºC to +85°C
10 µMAX
MAX4298ESD
-40ºC to +85°C
14 SO
MAX4299EWP
-40ºC to +85°C
20 SO
MAX4299EUE
-40ºC to +85°C
16 TSSOP
Typical Operating Circuit appears at end of data sheet.
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
PSRR vs. Frequency
MAX4298/9-13
-50
-60
-70
TOP VIEW
OUT1 1
-80
PSRR (dB)
Pin Configurations
-90
GND
10 VCC
2
-100
MAX4298
9
OUT2
IN1
3
8
IN2
-120
BIAS
4
7
CBYPASS
-130
SVCC
5
6
MUTE
-110
-140
-150
100
1k
10k
FREQUENCY (Hz)
100k
µMAX
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX4298/MAX4299
General Description
MAX4298/MAX4299
Ultra-High PSRR Stereo Drivers +
Microphone Amp + 100mA Linear Regulator
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC) to GND ...............................................+6V
Standby Supply Voltage (SVCC) to GND ...............................+6V
REG, FB, REGON to GND ..........................-0.3V to (VCC + 0.3V)
BIAS, CBYPASS, MUTE, IN_, MICIN to GND ..............-0.3V to the
Larger of (VCC +0.3V) or (SVCC +0.3V)
OUT_, MICOUT to GND ................................-0.3V to the Smaller
of +5.5V, or (VCC + 0.3V)
Duration of Output Short-Circuit to GND or VCC ................10min
Continuous Power Dissipation
10-Pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW
14-Pin SO (derate 8.3mW/°C above +70°C)................667mW
20-Pin SO (derate 10.0mW/°C above +70°C)..............800mW
16-Pin TSSOP (derate 9.4mW/°C above +70°C) .........755mW
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
(VCC = SVCC = +5V, RL = ∞ on all outputs, CBYPASS = 1µF, CBIAS = 1µF, CREG = 10µF (MAX4299), TA = TMIN to TMAX, unless otherwise noted. Load resistors (RL) are terminated to 2.25V. Typical values are at TA = +25°C. Specifications apply to both MAX4298 and
MAX4299, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
Supply Voltage Range
VCC
Quiescent Current
ICC
Mute Quiescent Current
SVCC Current (Note 2)
ISVCC
CONDITIONS
Inferred from PSRR test
MIN
TYP
4.5
MAX
UNITS
5.5
V
MAX4298
10.2
17.5
MAX4299
10.6
18.0
MAX4298
10.2
17.5
MAX4299
10.6
18.0
VBIAS = 1.125V, VCC = 0
300
500
VBIAS = 2.25V, VCC = 5.0V
7
mA
mA
µA
DRIVER AMPLIFIERS
Input Offset Voltage
VOS
Input Bias Current
IBIAS
Power-Supply Rejection
Ratio
PSRR
±1
0.2
DC, VCC = 4.5V to 5.5V
115
f = 20kHz
93
f = 100kHz
Output Drive
VOUT
1.45
1.59
RL = 32Ω
1.2
1.53
RL = 16Ω
1.0
1.48
0.02
AV = -1V/V, f = 1kHz, RL = 16Ω,
VOUT = 1.0VRMS
0.04
SNR
RL = 10kΩ,
VOUT = 1.06VRMS, AV = -1V/V
105
Open-Loop Voltage Gain
AVOL
RL = 32Ω, 0.55V ≤ VOUT ≤ VCC - 0.55V
Unity-Gain Bandwidth
GBW
Capacitive Drive
2
nA
dB
VRMS
0.0008
AV = -1V/V, f = 1kHz, RL = 32Ω,
VOUT = 1.2VRMS, (Notes 3, 4)
Full-Scale Signal-to-Noise Ratio
(Note 4)
mV
80
RL = 10kΩ
AV = -1V/V, f = 1kHz, RL = 10kΩ,
VOUT = 1.5VRMS
THD + Noise
±10
76
0.1
%
dB
22
nF
87
dB
1.3
MHz
_______________________________________________________________________________________
Ultra-High PSRR Stereo Drivers +
Microphone Amp + 100mA Linear Regulator
(VCC = SVCC = +5V, RL = ∞ on all outputs, CBYPASS = 1µF, CBIAS = 1µF, CREG = 10µF (MAX4299), TA = TMIN to TMAX, unless otherwise noted. Load resistors (RL) are terminated to 2.25V. Typical values are at TA = +25°C. Specifications apply to both MAX4298 and
MAX4299, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
2.13
2.25
2.37
UNITS
BIAS VOLTAGE OUTPUT
DC BIAS Voltage
VBIAS
IL = 0
Line Regulation
Load Regulation
IL = 0 to 1µA
V
120
dB
50
mV
DIGITAL INPUTS (MUTE for MAX4298/MAX4299, and REGON for MAX4299)
Input Voltage High
VINH
Input Voltage Low
VINL
Input Leakage Current
IIN
2.4
V
VIN = 0 or VCC
0.8
V
±1
µA
±10
mV
MICROPHONE AMPLIFIER (MAX4299 only)
Input Offset Voltage
VOS
±2
Input Bias Current
IBIAS
0.2
Power-Supply Rejection Ratio
PSRR
DC, VCC = 4.5V to 5.5V
115
f = 20kHz
93
f = 100kHz
80
Voltage Gain
AVOL
RL = 10kΩ, 0.13V ≤ VMICOUT ≤ VCC - 0.13V
80
Output Drive
VOUT
RL = 10kΩ
1.4
THD + Noise (Note 4)
Full-Scale Signal-to-Noise Ratio
(Note 4)
THD+N
SNR
All-Hostile Crosstalk
Unity Gain Bandwidth
f = 1kHz, RL = 10kΩ,
VMICOUT = 1.5VRMS
nA
dB
100
dB
1.58
VRMS
AV = -1V/V
0.005
AV = -10V/V
0.03
%
RL = 10kΩ, VMICOUT = 1.06VRMS, AV = -10V/V
80
dB
f = 10kHz (Note 5)
80
dB
1
MHz
GBW
REGULATOR (MAX4299 only)
Regulator Output Voltage
VREG
Line Regulation
Load Regulation
FB Voltage
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
VCC = 4.5V to 5.5V. IL = 0 to 100mA, using
internal feedback
3.3
3.45
V
VCC = 4.5V to 5.5V, IL = 50mA
0.2
mV
IL = 10mA to 100mA
30
mV
50
mV
1.233
V
IL = 0 to 100mA
VFB
3.15
Reference for regulator adjustment
All devices are 100% production tested at TA = +25°C. All temperature limits are guaranteed by design.
Current drawn from SVCC when VCC < 4V.
Guaranteed by design.
Measurement bandwidth is 20Hz to 22kHz.
Voltage at MICOUT with OUT1 = OUT2 = 1VRMS into 32Ω.
_______________________________________________________________________________________
3
MAX4298/MAX4299
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VCC = SVCC = +5V, typical operating circuit, TA = +25°C, unless otherwise noted.)
10.0
2.0
TA = +25°C
9.5
OUT
1.5
1.0
SPEAKER
0.5
OUT
3
OUTPUT VOLTAGE (V)
ICC (mA)
10.5
RL = 32Ω
OUTPUT VOLTAGE (V)
TA = +85°C
4
MAX4298/9-02
11.0
MUTE PERFORMANCE
POWER-UP/POWER-DOWN
2.5
MAX4298/99-01
11.5
MAX4298/9-03
MAX4298
SUPPLY CURRENT vs. SUPPLY VOLTAGE
2
1
0
TA = -40°C
9.0
0
-1
8.5
-0.5
-2
RL = 32Ω
CAC = 220µF
SPEAKER
4.2
4.4
4.6
4.8
5.0
5.2
5.4
5.6
1.0
0
2.0
1.0
1.5
TIME (s)
POWER-DOWN/POWER-UP with SCHOTTKY
DIODE AND RESERVOIR CAPACITOR
DRIVER OUT
THD+N vs. FREQUENCY
DRIVER OUT
THD+N vs. FREQUENCY
1
BW = 80kHz
BW = 22kHz
0.001
RL = 32Ω
CAC = 22OµF
-1
0
0.5
1.0
TIME (s)
1.5
0.0001
100
2.0
DRIVER OUT
THD+N vs. FREQUENCY
10
MAX4298/99-07
1
0.1
1k
10k
MAX4298/99-06
RL = 32Ω
AV = -1
VOUT = 1.2VRMS
0.0001
100
100k
RL = 16Ω
AV = -1
VOUT = 1VRMS
0.0001
DRIVER OUT
THD+N vs. AMPLITUDE
BW = 22kHz
0.1
0.01
0.001
10
BW = 22kHz
1
1k
10k
INPUT FREQUENCY (Hz)
100k
fIN = 1kHz
0.1
0.01
0.001
AV = -1
RL = 10kΩ
fIN = 1kHz
0.0001
100
100k
DRIVER OUT
THD+N vs. AMPLITUDE
THD+N (%)
THD+N (%)
0.001
10k
INPUT FREQUENCY (Hz)
BW = 22kHz
0.01
1k
INPUT FREQUENCY (Hz)
1
BW = 80kHz
BW = 22kHz
0.01
0.001
RL = 10kΩ
AV = -1
VOUT = 1.5VRMS
MAX4298/99toc08
0
BW = 80kHz
MAX4298/99toc09
VOUT
0.01
THD+N (%)
THD+N (%)
3
2
0.1
0.1
SVCC
2.0
1
MAX4298/99-05
1
MAX4298/99-04
VCC = 5V
VCC = 0
4
4
0.5
TIME (s)
5
VOLTAGE (V)
0
VCC (V)
6
THD+N (%)
MAX4298/MAX4299
Ultra-High PSRR Stereo Drivers +
Microphone Amp + 100mA Linear Regulator
RL = 32Ω
AV = -1
0.0001
0
0.5
1
1.5
OUTPUT VOLTAGE (VRMS)
2
0
0.5
1
1.5
OUTPUT VOLTAGE (VRMS)
_______________________________________________________________________________________
2
Ultra-High PSRR Stereo Drivers +
Microphone Amp + 100mA Linear Regulator
MAX4298/MAX4299
Typical Operating Characteristics (continued)
(VCC = SVCC = +5V, typical operating circuit, TA = +25°C, unless otherwise noted.)
DRIVER OUT
CHANNEL SEPARATION
vs. INPUT FREQUENCY
0.001
0
0.5
1
1.5
OUT1 TO OUT2
RL = 10kΩ
AV = -1
VOUT = 1VRMS
-120
100
2
1k
10k
-90
B
C
A
-95
-100
-105
RL = 16Ω
A = RI = 20kΩ, RF = 20kΩ
B = RI = 10kΩ, RF = 10kΩ
C = RI = 10kΩ, RF = 20kΩ
-110
-115
-120
100k
100
1k
10k
100k
OUTPUT VOLTAGE (VRMS)
INPUT FREQUENCY (Hz)
INPUT FREQUENCY (Hz)
DRIVER OUT
POWER-SUPPLY REJECTION
RATIO vs. FREQUENCY
DRIVER OUT
OPEN-LOOP FREQUENCY RESPONSE
DRIVER OUT
OPEN-LOOP FREQUENCY RESPONSE
MAX4298/9-14
MAX4298/9-15
80
180
80
180
70
160
70
160
-80
60
140
60
-90
50
120
50
MAX4298/9-13
-60
GAIN (dB)
-70
PHASE
GAIN (dB)
90
90
PHASE (deg)
200
-50
80
80
-120
20
60
20
-130
10
40
10
-140
0
20
0
1k
10k
32Ω || 15pF
-10
0.01
-150
100
GAIN
100k
0.1
1
10
100
60
GAIN
40
20
32Ω || 1.5nF
-10
0.01
0
1000 10,000
120
100
30
-110
140
PHASE
30
100
-100
0.1
1
10
100
0
1000 10,000
FREQUENCY (Hz)
INPUT FREQUENCY (kHz)
INPUT FREQUENCY (kHz)
DRIVER OUT
OPEN-LOOP FREQUENCY RESPONSE
DRIVER OUT
OPEN-LOOP FREQUENCY RESPONSE
DRIVER OUT
OPEN-LOOP FREQUENCY RESPONSE
MAX4298/9-16
180
70
MAX4298/9-18
200
90
80
180
80
180
160
70
160
70
160
60
140
60
140
60
140
50
120
50
120
50
PHASE
PHASE
GAIN (dB)
80
MAX4298/9-17
PHASE (deg)
90
90
PHASE (deg)
200
200
40
40
GAIN (dB)
PSRR (dB)
-100
-110
RL = 16Ω
AV = -1
0.0001
-90
-85
40
100
30
80
60
20
60
20
10
40
10
40
10
0
20
0
20
0
40
100
30
80
20
-10
0.01
GAIN
32kΩ || 22nF
0.1
1
10
100
INPUT FREQUENCY (kHz)
0
1000 10,000
-10
0.01
GAIN
10kΩ || 15pF
0.1
1
10
100
INPUT FREQUENCY (kHz)
0
1000 10,000
PHASE (deg)
0.01
-80
GAIN (dB)
THD+N (%)
0.1
OUT2 TO OUT1
200
120
PHASE
40
100
30
80
-10
0.01
60
GAIN
40
20
10kΩ || 1.5nF
0.1
1
10
100
0
1000 10,000
INPUT FREQUENCY (kHz)
_______________________________________________________________________________________
5
PHASE (deg)
-70
fIN = 1kHz
-80
MUTED OUTPUT ATTENUATION (dB)
1
CHANNEL SEPARATION (dB)
BW = 22kHz
MAX4298/9-11
-60
MAX4298/99toc10
10
DRIVER OUT
MUTED OUTPUT ATTENUATION
vs. INPUT FREQUENCY
MAX4298/9-12
DRIVER OUT
THD+N vs. AMPLITUDE
Typical Operating Characteristics (continued)
(VCC = SVCC = +5V, typical operating circuit, TA = +25°C, unless otherwise noted.)
60
140
120
PHASE
40
100
30
80
20
60
GAIN
10
40
0
20
10kΩ || 22nF
1
10
180
70
160
60
140
50
120
40
80
30
60
GAIN
0.1
1
10
20
0 10kΩ || 15pF
-10
0.01
0.1
1
100
40
10
100
0
1000 10,000
INPUT FREQUENCY (kHz)
INPUT FREQUENCY (kHz)
INPUT FREQUENCY (kHz)
MICOUT OPEN LOOP
FREQUENCY RESPONSE
MICOUT
THD+N vs. AMPLITUDE
REGOUT OUTPUT VOLTAGE
vs. LOAD CURRENT
10
200
180
80
70
160
60
140
120
50
40
PHASE
100
30
80
20
60
GAIN
10
0
10kΩ || 150pF
-10
0.01
0.1
1
10
100
1
0.1
0.01
40
0.001
20
0
1000 10,000
0.0001
3.5
RL = 10kΩ
AV = -1
fIN = 1kHz
BW = 22kHz
MAX4298/99 toc24
MAX4298/99 toc22
90
3.4
3.3
3.2
3.1
3.0
0
0.5
1.0
1.5
2.0
0
20
AMPLITUDE (VRMS)
INPUT FREQUENCY (kHz)
REGOUT TRANSIENT RESPONSE
40
REGOUT TRANSIENT RESPONSE
MAX4298/99 toc26
VOUT
30mV/div
200µs/div
60
LOAD CURRENT (mA)
MAX4298/99 toc25
6
100
PHASE
10
-120
0.01
200
80
20
-100
0
1000 10,000
100
-80
OUTPUT VOLTAGE (V)
0.1
-60
MAX4298/99 toc23
-10
0.01
-40
GAIN (dB)
160
AV = -100
MAX4298/99 toc21
90
MAX4298/99 toc20
70
ALL HOSTILE CROSSTALK (dB)
180
THD+N (%)
GAIN (dB)
80
50
-20
200
PHASE (deg)
MAX4298/99 toc19
90
MICOUT OPEN LOOP
FREQUENCY RESPONSE
MICOUT ALL HOSTILE CROSSTLAK
(INPUT REFERRED)
VOUT
30mV/div
100mA
IL
100mA
0
10mA
IL
200µs/div
_______________________________________________________________________________________
80
100
PHASE (deg)
DRIVER OUT
OPEN-LOOP FREQUENCY RESPONSE
GAIN (dB)
MAX4298/MAX4299
Ultra-High PSRR Stereo Drivers +
Microphone Amp + 100mA Linear Regulator
Ultra-High PSRR Stereo Drivers +
Microphone Amp + 100mA Linear Regulator
PIN
MAX4298
MAX4299
MAX4299
10-PIN
µMAX
14-PIN SO
16-PIN
TSSOP
20-PIN SO
—
—
16
1
MAX4298
NAME
REG
FUNCTION
Regulator Output. Bypass REG to GND with a 10µF
capacitor.
Regulator Feedback. Internal resistors from this point
to REG and GND define the regulator output value.
Adjustments can be made to the output value by
adding resistors in the same place externally.
—
—
1
2
FB
1
2
2
4
OUT1
Driver Amplifier Output
—
—
3
5
PGND
Power Ground for Driver Outputs
GND
2
3
4
6
3
4
5
7
IN1
4
5
6
8
BIAS
Bias Point for Amplifiers. Bypass BIAS to GND with a
1µF capacitor.
Standby Power Supply. Connect to a standby +5V
supply that is always on, or bypass with 220µF and
connect a Schottky diode from VCC to SVCC. Short to
VCC if clickless power-down is not essential.
Ground
Inverting Input for Driver Amplifier
5
6
7
9
SVCC
—
—
8
10
MICOUT
—
—
9
11
MICIN
Inverting Input for Microphone Amplifier
Mute Digital Input. Connect to GND for normal
operation. When MUTE is connected to VCC, OUT1
and OUT2 are muted, REG stays on, and MICOUT
stays on.
Microphone Amplifier Output
6
9
10
13
MUTE
7
10
11
14
CBYPASS
8
11
12
15
IN2
9
12
13
16
OUT2
10
13
14
17
VCC
Power Supply. Connect to +5V.
—
1, 7, 8, 14
—
3, 12, 18, 19
N.C.
No Connection. Not internally connected.
—
—
15
20
REGON
Detailed Description
The MAX4298/MAX4299 are audio system ICs designed for single +5V applications. The MAX4299 has a
stereo headphone driver, a microphone amplifier, and
a 100mA +3.3V linear regulator; the MAX4298 has the
stereo headphone driver only. The MAX4298/MAX4299
are designed specifically for harsh digital environments
where board space is at a premium and the digital
Bypass to GND with a 1µF Capacitor
Inverting Input for Driver Amplifier
Driver Amplifier Output
Regulator Control. Connect to VCC for normal
operation. Connect to GND to shut off the regulator.
power supply is noisy. The design uses innovative
design techniques to achieve ultra-high power-supply
rejection across the audio signal band while, at the
same time, delivering a high current rail-to-rail output
drive capability. These devices are designed to drive
highly capacitive loads that may be encountered when
driving long cables to a remote load such as
desktop/notebook headphones or speakers. They are
fully compliant to PC99 standards. Figure 1 is the
_______________________________________________________________________________________
7
MAX4298/MAX4299
Pin Description
MAX4298/MAX4299
Ultra-High PSRR Stereo Drivers +
Microphone Amp + 100mA Linear Regulator
VCC
VCC
SVCC
IN1
BIAS
_
SVCC
18.4kΩ
REGON
FB
OUT1
+
50kΩ
1.233V
+
_
REG
MAX4298
11kΩ
2.25V
MUTE
MAX4299
IN2
+
_
OUT2
IN1
CBYPASS
_
OUT1
+
GND
BIAS
2.25V
50kΩ
IN2
Figure 1. MAX4298 Block Diagram
+
_
OUT2
N.C.
MUTE
The amplifiers exhibit better than 115dB of DC powersupply rejection and 93dB at 20kHz. The output amplifiers are capable of driving a 1.5VRMS signal into 10kΩ
load with 0.0008% distortion. They can also drive 32Ω
headphones to 1.2V RMS with 0.02% distortion. At
+3.3V, the linear regulator can output 100mA of current.
MICOUT
+
_
MICIN
GND
CBYPASS
PGND
Figure 2. MAX4299 Block Diagram
BIAS
The common-mode bias point for the amplifiers is set to
2.25V by internal circuitry that has two functions. It provides a clickless/popless power-up/power-down waveform for the amplifiers. Also, it generates a groundreferenced bias voltage with ultra-high power-supply
rejection ratio (PSRR). BIAS should be bypassed with 1µF
to GND.The output impedance of the BIAS pin is 50kΩ.
Clickless/Popless Function
The MAX4298/MAX4299 are designed for high-fidelity
audio performance into AC-coupled loads. The design
techniques achieve a clickless/popless power-up
sequence, and the use of a low-current standby supply
(SVCC) or external Schottky diode/reservoir capacitor
combination allows clickless/popless power-down. A
clickless/popless mute function is also provided to maintain a low impedance output when the input signal is
switched off.
Mute Function
The MAX4298/MAX4299 have a MUTE pin that allows the
user to mute the outputs of the device. This feature disconnects the input signal from the power amplifiers when
a logic high is present at the MUTE pin. To ensure proper
functionality, the MUTE pin should always be tied to either
VCC or GND. MUTE only affects the headphone driver
outputs. REG, BIAS, and MICOUT are unaffected. OUT1
and OUT2 are muted, but remain in a low-impedance
state to ensure clickless/popless operation.
8
SVCC
The MAX4298/MAX4299 provide a fully clickless powerdown sequence. SVCC normally should be connected to
a low-current +5V power source, but alternatively can be
connected with a reservoir capacitor to ground and a
Schottky diode to VCC. A reservoir capacitor of 220µF or
higher provides enough charge for the clickless powerdown sequence when CBIAS = 1µF. For larger values of
CBIAS, increase the reservoir capacitor accordingly.
Short to VCC if clickless power-down is not needed.
Driver Amplifier
The headphone driver amplifier is a class AB amplifier
designed to drive 16Ω loads. The amplifiers have innovative architectures for both the input and output stages
to achieve ultra-high PSRR while maintaining rail-to-rail
output drive capability. The output stage can drive high
capacitive loads encountered when driving long cables
used for desktop speakers or headphones.
Microphone Preamplifier (MAX4299)
The MAX4299 provides a microphone preamplifier that
is a low-power version of the audio amplifier. It is intended to be used for low-level signal amplification. This
microphone preamplifier provides rail-to-rail output with
very high PSRR.
_______________________________________________________________________________________
Ultra-High PSRR Stereo Drivers +
Microphone Amp + 100mA Linear Regulator
Layout
Good layout improves performance by decreasing the
amount of stray capacitance and noise at the power
amplifier’s inputs and output. To decrease stray capacitance, minimize PC board trace lengths and resistor
leads, and place external components as close to the
pins as possible.
Applications Information
Capacitor Selection and
Regulator Stability
Normally, use a 10µF capacitor on REG (MAX4299 only)
and a 1µF capacitor on CBYPASS. Larger capacitor values and lower ESRs provide better supply-noise rejection and line-transient response. Reduce noise and
improve load-transient response, stability, and powersupply rejection by using larger capacitors. For stable
operation over the full temperature range and load currents up to 100mA, a minimum of 10µF (REG) and 1µF
(CBYPASS) is recommended.
Use a 1µF bypass capacitor on BIAS to ensure a fully
clickless/popless power-up sequence. Smaller capacitor
values may be used here to decrease the power-up
time, but may cause the power-up transient to become
audible. Larger bypass capacitors are not necessary to
reduce noise and/or improve AC power-supply rejection.
SVCC is the standby power supply. If using an external
diode for charging, a 220µF reservoir capacitor on
SVCC provides standby power for the clickless powerdown sequence. Smaller capacitors here may cause an
audible output transient on power-down; 220µF or higher provides enough energy when CBIAS = 1µF. For larger values of C BIAS, increase the reservoir capacitor
accordingly.
Mic Biasing (MAX4299)
Common microphone elements require resistive biasing
to power their internal circuitry. A 2kΩ resistor is typically used, and the microphone is AC-coupled to the
microphone amplifier. If the microphone element allows
low-voltage operation, biasing to the REG output provides excellent power-supply rejection.
Power Supply and Bypassing
The excellent PSRR of the MAX4298/MAX4299 allows
them to operate from noisy power supplies. In most
applications, a 0.1µF capacitor from VCC to GND is sufficient. This bypass capacitor should be placed close
to the VCC pin.
Power Dissipation
The first equation below indicates the maximum power
dissipation point for a package that has two power
amplifiers operating at identical known supply voltages
and loads with sine wave inputs:
PIC(DISS) = (VCC)2 / (π2RL) [W]
For example, with a 5V power supply and a load of 16Ω,
the maximum power dissipation of the amplifiers alone
is 317mW.
The additional power dissipation due to the 100mA regulator operating at maximum current is nominally
170mW, but will increase if the output is reduced externally from its nominal 3.3V. The regulator power consumption is given by:
PREG = (VCC - VREG) x 100mA [W]
To avoid thermal shutdown the sum of the regulator and
amplifier power dissipation must not exceed the absolute
maximum power-dissipation rating of the package.
Short-Circuit Protection and
Thermal Shutdown
The MAX4298/MAX4299 have short-circuit current protection on all outputs. They also have a thermal shutdown function designed to protect the chip from junction
temperatures in excess of +150°C that may arise from
temporary short circuits or operation beyond the power
dissipation limit of the package. The driver amplifier outputs limit at around ±220mA, the regulator at 150mA,
and the microphone amplifier at +1.5mA/-12mA.
USB Applications
Universal serial bus (USB) interfaces are an increasingly
popular method of interfacing medium-speed (up to
12Mbps) PC peripherals. One of the great benefits of
the USB interface is the inclusion of a +5V supply. While
this supply works well for a mouse or keyboard, its susceptibility for noise pickup can be unsuitable for highfidelity audio applications. The MAX4298/MAX4299s’
excellent PSRR make them ideal candidates for USB
applications due to their insensitivity to the supply noise.
Of particular interest is an Internet-Protocol (IP) phone.
This PC peripheral uses the local internet service
provider as a free long-distance phone. The MAX4299,
with its integral microphone amp, headphone driver,
and linear regulator, can be a key element in the implementation of an IP phone that interfaces to the PC
through the USB.
_______________________________________________________________________________________
9
MAX4298/MAX4299
Regulator (MAX4299)
The MAX4299 also has an additional 100mA lowdropout (LDO) regulator to provide clean analog power
for other sensitive analog circuitry on the PC board,
such as a typical PC99 audio codec or microphone
biasing. It is designed to provide good AC line regulation. The nominal output voltage of REG is 3.3V, and is
adjustable between 1.2V and 4.5V by connecting a
resistor-divider from REG to GND. Connect FB to the
junction of the resistor-divider. The input impedance at
FB is typically 7kΩ, which should be considered in output voltage calculations. REG should be bypassed to
GND with at least 10µF.
Ultra-High PSRR Stereo Drivers +
Microphone Amp + 100mA Linear Regulator
MAX4298/MAX4299
Typical Operating Circuits
RF
10kΩ
VCC
OPTIONAL
VCC
MAX4298
SVCC
220µF
RI
10kΩ
LEFT
_
+
IN1
OUT1
MUTE
BIAS
1µF
RI
10kΩ
VCC
CAC
220µF
2.25V
RIGHT
IN2
+
_
OUT2
1µF
CAC
220µF
GND
CBYPASS
RF
10kΩ
20kΩ
VCC
REGON
10µF
AVDD
3.3V
REG
FB
LDO
MAX4299
IN1
LEFT
AUDIO
CODEC
0.33µF 20kΩ
BIAS
_
+
VCC
OPTIONAL
SVCC
220µF
CAC
220µF
OUT
MUTE
VCC
2.25V
1µF
IN2
RIGHT
+
_
CAC
220µF
0.33µF 20kΩ
MIC
AVDD
OUT2
MICOUT
CBYPASS
+
_
MICIN
GND
1µF
20kΩ 0.33µF
RBIAS
ELECTRET
MIC
PGND
20kΩ
200kΩ
10
______________________________________________________________________________________
Ultra-High PSRR Stereo Drivers +
Microphone Amp + 100mA Linear Regulator
TOP VIEW
REG 1
20 REGON
16 REG
FB 1
FB 2
19 N.C.
OUT1 2
15 REGON
N.C. 3
18 N.C.
PGND 3
14 VCC
OUT1 4
17 VCC
GND 4
16 OUT2
IN1 5
PGND 5
MAX4299
GND 6
IN1 7
13 OUT2
12 IN2
15 IN2
BIAS 6
11 CBYPASS
14 CBYPASS
SVCC 7
10 MUTE
BIAS 8
13 MUTE
SVCC 9
12 N.C.
MICOUT 10
MAX4299
MICOUT 8
9
TSSOP
N.C. 1
14 N.C.
OUT1
2
13 VCC
GND
3
IN1 4
12 OUT2
MAX4298
BIAS 5
11 IN2
10 CBYPASS
SVCC 6
9
MUTE
N.C. 7
8
N.C.
MICIN
SO
11 MICIN
WIDE SO
Chip Information
MAX4298 TRANSISTOR COUNT: 760
MAX4299 TRANSISTOR COUNT: 905
PROCESS: BiCMOS
10LUMAX.EPS
Package Information
______________________________________________________________________________________
11
MAX4298/MAX4299
Pin Configurations (continued)
MAX4298/MAX4299
Ultra-High PSRR Stereo Drivers +
Microphone Amp + 100mA Linear Regulator
SOICW.EPS
Package Information (continued)
12
______________________________________________________________________________________
Ultra-High PSRR Stereo Drivers +
Microphone Amp + 100mA Linear Regulator
SOICN.EPS
______________________________________________________________________________________
13
MAX4298/MAX4299
Package Information (continued)
Ultra-High PSRR Stereo Drivers +
Microphone Amp + 100mA Linear Regulator
TSSOP,NO PADS.EPS
MAX4298/MAX4299
Package Information (continued)
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2001 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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