19-3700; Rev 0; 3/08
`
`16VP-P Class G Amplifier with
`Inverting Boost Converter
`
`MAX9738
`
`Features
`♦ Integrated Inverting Boost Converter
`♦ 2.7V to 5.5V Single-Supply Operation
`♦ 16VP-P Output Voltage Swing, Ideal for Driving a
`Ceramic Speaker
`♦ Maintains Output Voltage Swing as the Battery
`Decays
`♦ Clickless/Popless Operation
`♦ Small, Thermally Efficient 5x4 WLP Package
`(2.5mm x 2mm)
`
`Cellular Phones
`Smartphones
`MP3 Players
`Personal Media
`Players
`
`PART
`
`MAX9738EWP+TG45
`
`Applications
`Handheld Gaming
`Consoles
`Notebook Computers
`
`Ordering Information
`PIN-
`PACKAGE
`5x4 WLP
`
`-40°C to +85°C
`
`TEMP RANGE
`
`+Denotes a lead-free package.
`T = Tape and reel.
`G45 indicates protective die coating.
`
`Simplified Block Diagram
`
`General Description
`The MAX9738 features a mono Class G power amplifi-
`er with an integrated inverting boost converter. The
`Class G amplifier is specifically designed to drive the
`high capacitance of a ceramic/piezoelectric loud-
`speaker. The inverting boost converter can typically
`supply up to 400mA of peak output current, allowing
`for a constant output of 16VP-P over the 2.7V to 5.5V
`supply voltage range.
`The MAX9738 maximizes battery life by offering high-
`performance efficiency. Maxim’s proprietary output
`stage provides efficiency levels greater than Class AB
`devices without the EMI penalties commonly associat-
`ed with Class D amplifiers.
`The MAX9738 is ideally suited to deliver the high output
`voltage swing required to drive ceramic/piezoelectric
`speakers.
`The device utilizes fully differential inputs and outputs,
`comprehensive click-and-pop suppression, shutdown
`control, and soft-start circuitry. The MAX9738 is fully
`specified over the -40°C to +85°C extended tempera-
`ture range and is available in an ultra-small, lead-free
`5x4 WLP (2.5mm x 2mm) package.
`
`Typical Application Circuit/Functional Diagram and Pin
`Configuration appear at end of data sheet.
`
`VDD
`
`VDD
`
`VBAT
`
`VSS
`
`ISET
`BST
`
`LX
`
`OUT+
`
`OUT-
`
`INVERTING
`BOOST
`CONVERTER
`
`CLASS G
`OUTPUT
`STAGE
`
`GND
`
`MAX9738
`
`PIEZOELECTRIC
`SPEAKER
`
`FB+
`
`IN+
`
`IN-
`
`FB-
`
`+
`
`-
`
`________________________________________________________________ Maxim Integrated Products 1
`For pricing, delivery, and ordering information,please contact Maxim Directat 1-888-629-4642,
`or visit Maxim’s website at www.maxim-ic.com.
`
`INTEL 1015
`
`

`

`16VP-P Class G Amplifier with
`Inverting Boost Converter
`
`Continuous Current into/out of
`OUT+, OUT-, VBAT, VSS, VDD .......................................400mA
`Any Other Pin ..................................................................20mA
`Duration of OUT+, OUT- Short Circuit to
`VDD, GND, VSS (VSS > -6V).....................................Continuous
`RMS Current per Bump
`VBAT, LX .........................................................................800mA
`Continuous Power Dissipation (TA = +70°C)
`20-Bump UCSP (derate 10mW/°C above +70°C) ........800mW
`Operating Temperature Range .......................... -40°C to +85°C
`Junction Temperature......................................................+150°C
`Storage Temperature Range ............................ -65°C to +150°C
`Bump Temperature (soldering) Reflow............................+235°C
`
`ABSOLUTE MAXIMUM RATINGS
`(Voltages with respect to GND.)
`VDD, VBAT ............................................................... -0.3V to +6V
`VDD to VBAT ......................................................... -0.1V to +0.1V
`VSS ...................................................Capacitor Connection Only,
`(VBAT - 10V) to +0.3V
`OUT+, OUT- .................................................-6V to (VDD + 0.3V)
`(OUT+ to OUT-) ................................................... -8.7V to +8.7V
`IN+, IN-, FB+, FB-, ISET .............................-0.3V to (VDD + 0.3V)
`LX ..................................................(VDD - 11.5V) to (VDD + 0.3V)
`BST..........................................................(LX - 0.3V) to (LX + 6V)
`SHDN........................................................................-0.3V to +6V
`
`MAX9738
`
`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
`(VDD = VBAT = SHDN = 3.6V, GND = 0V, VDD - VSS = 9V, RISET = 100k(cid:60), RIN+ = RIN- = 10k(cid:60), RFB+ = RFB- = 10k(cid:60), CL = open, RL = (cid:104),
`C1 = 10μF, C2 = 10μF, C3 = 0.1μF, C4 = 0.1μF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
`
`PARAMETER
`GENERAL
`Supply Voltage Range
`Total Quiescent Current
`
`Maximum Total Quiescent
`Current
`Shutdown Supply Current
`
`Turn-On Time
`
`ISET Bias Voltage
`Thermal Shutdown Threshold
`Thermal Shutdown Hysteresis
`
`SYMBOL
`
`CONDITIONS
`
`MIN
`
`TYP
`
`MAX
`
`UNITS
`
`VDD
`IDD_TOT
`
`Inferred from PSRR test
`IVDD + IVBAT (boost converter disabled)
`
`2.7
`
`IDD_TOT_MAX Typical application circuit (Note 2)
`
`SHDN = GND
`Time from shutdown or power-on to full
`operation (CIN = 0.1μF)
`
`ISHDN
`
`tON
`
`VISET
`
`0.9
`
`5.5
`12.5
`
`2
`
`1.1
`
`7
`
`16.5
`
`0.6
`
`10
`
`1.0
`150
`15
`
`V
`mA
`
`mA
`
`μA
`
`ms
`
`V
`°C
`°C
`
`2
`
`_______________________________________________________________________________________
`
`

`

`MAX9738
`
`16VP-P Class G Amplifier with
`Inverting Boost Converter
`
`ELECTRICAL CHARACTERISTICS (continued)
`(VDD = VBAT = SHDN = 3.6V, GND = 0V, VDD - VSS = 9V, RISET = 100k(cid:60), RIN+ = RIN- = 10k(cid:60), RFB+ = RFB- = 10k(cid:60), CL = open, RL = (cid:104),
`C1 = 10μF, C2 = 10μF, C3 = 0.1μF, C4 = 0.1μF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
`
`SYMBOL
`
`CONDITIONS
`
`MIN
`
`TYP
`
`MAX
`
`UNITS
`
`PARAMETER
`SPEAKER AMPLIFIER
`
`Output Offset Voltage
`
`Input DC Bias Voltage
`
`Common-Mode Output Level
`
`Click-and-Pop Level
`
`Voltage Gain
`
`Continuous Output Power
`
`VOS
`
`VBIAS
`
`VCM
`
`KCP
`
`AV
`
`POUT
`
`VDD = 2.7V or 5.5V
`
`TA = +25°C
`TMIN ≤ TA ≤ TMAX
`
`(Note 3)
`VDD = 2.7V
`VDD = 5.5V
`Peak voltage into/out of shutdown,
`A-weighted, 32 samples per second
`(Note 4)
`
`VDD = 2.7V (Note 5)
`VBAT = VDD = 2.7V or 5.5V, RLOAD = 8Ω,
`THD+N = 1%
`
`1.0
`0.75
`2.40
`
`±15
`±30
`1.5
`1.60
`3.45
`
`±3.7
`
`1.23
`1.17
`3
`
`-60
`
`11.5
`
`12
`
`12.5
`
`0.25
`
`5.5
`
`5.0
`
`6.3
`
`6.0
`
`60
`
`60
`80
`70
`60
`
`5.65
`
`5.37
`
`54
`
`0.2
`
`0.5
`
`0.4
`
`355
`95
`110
`
`1.4
`
`-3
`
`0.4
`+3
`
`mV
`
`V
`
`V
`
`dBV
`
`dB
`
`W
`
`VRMS
`
`dB
`
`dB
`
`%
`
`mA
`dB
`dB
`
`V
`
`μA
`
`Output Voltage
`
`VOUT
`
`THD+N < 1%, CIN_ =
`0.1μF, CL = 1.6μF,
`RL = 20Ω, TA = +25°C
`(Note 6)
`
`VBAT = VDD =
`2.7V, f = 1kHz
`
`VBAT = VDD =
`2.7V, f = 10kHz
`
`VBAT = VDD =
`3.6V, f = 1kHz
`
`VBAT = VDD =
`3.6V, f = 10kHz
`
`Common-Mode Rejection
`Ratio
`
`CMRR
`
`fIN = 1kHz (Note 7)
`
`VDD = 2.7V to 5.5V
`f = 217Hz, 100mVP-P ripple
`f = 1kHz, 100mVP-P ripple
`f = 20kHz, 100mVP-P ripple
`f = 1kHz, VOUT = 16VP-P, CL = 1.6μF,
`RL = 20Ω
`f = 10kHz, VOUT = 15.2VP-P, CL = 1.6μF,
`RL = 20Ω
`
`VOUT = 5VRMS, A-weighted (Note 6)
`A-weighted (Note 8)
`
`Power-Supply Rejection Ratio
`
`PSRR
`
`Total Harmonic Distortion Plus
`Noise
`
`THD+N
`
`Peak Load Current
`Signal-to-Noise Ratio
`Dynamic Range
`
`SHDN Input Threshold
`
`SHDN Input Leakage Current
`
`SNR
`DR
`VIH
`VIL
`IIH, IIL
`
`_______________________________________________________________________________________ 3
`
`

`

`16VP-P Class G Amplifier with
`Inverting Boost Converter
`
`ELECTRICAL CHARACTERISTICS (continued)
`(VDD = VBAT = SHDN = 3.6V, GND = 0V, VDD - VSS = 9V, RISET = 100k(cid:60), RIN+ = RIN- = 10k(cid:60), RFB+ = RFB- = 10k(cid:60), CL = open, RL = (cid:104),
`C1 = 10μF, C2 = 10μF, C3 = 0.1μF, C4 = 0.1μF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
`PARAMETER
`SYMBOL
`CONDITIONS
`MIN
`TYP
`MAX
`UNITS
`INVERTING BOOST CONVERTER (VDD - VSS = -8.75V)
`Switching Frequency
`FET On-Time
`Minimum FET Off-Time
`
`1.5
`950
`350
`
`MHz
`ns
`ns
`
`tFON
`
`550
`100
`
`750
`220
`
`MAX9738
`
`Peak Output Current
`
`FET Current Limit (DC)
`
`FET Current Limit (Transient)
`
`FET On-Resistance
`Regulated Output Voltage
`
`Transient Load Regulation
`
`Maximum Output Ripple
`BST Shutdown Leakage
`
`VBAT Shutdown Current
`
`LX Shutdown Leakage
`
`RDSON
`
`VDD > 3V, typical application circuit
`(Note 9)
`TA = +25°C (Note 10)
`Typical application circuit, inductor ISAT
`rating > 1.7A
`ILX = 100mA, TA = +25°C
`VBAT - VSS
`0 to 400mA load step, typical application
`circuit
`ILOAD = 20mA, typical application circuit
`SHDN = 0V, LX = 0V, BST = 5V
`VBAT = VDD, SHDN = 0V, LX = 0V,
`BST = 5V
`LX = 0V, SHDN = 0V, BST = 5V
`
`0.77
`
`8.15
`
`400
`
`1.1
`
`1.6
`
`0.2
`8.9
`
`300
`
`200
`0.01
`
`0.01
`
`0.01
`
`mA
`
`A
`
`A
`
`Ω
`V
`
`mV
`
`mVP-P
`μA
`
`μA
`
`μA
`
`1.35
`
`0.26
`9.60
`
`1
`
`3
`
`3
`
`Note 3:
`
`Note 1: All devices are 100% production tested at TA = +25°C. Specifications over temperature limits are guaranteed by design.
`Total quiescent current depends on overall efficiency and varies with the LX inductor value and ESR, diode turn-on volt-
`Note 2:
`age, and the parasitic losses in all external components.
`Input DC bias voltage determines the maximum voltage swing of the input signal. An input signal with an amplitude
`greater than the input DC bias voltage results in clipping.
`Note 4: Amplifier inputs AC-coupled to GND.
`Note 5: Voltage gain is defined as [VOUT+ - VOUT-]/[VIN+ - VIN-].
`Note 6: VOUT is defined as [VOUT+ - VOUT-].
`Note 7: Matching of external AC-coupling input capacitors and gain resistors is critical to achieving good CMRR.
`Note 8: Dynamic range calculated by measuring the RMS voltage difference between a -60dBFS output signal and the noise floor,
`then adding 60dB. Full scale is defined as the output signal needed to achieve 1% THD+N.
`Note 9: Peak output current depends on external power-supply components and the signal frequency.
`Note 10: Boost converter current limit is tested with a DC sweep. Actual current-limit values under transient conditions may be high-
`er. At high input supply, VBAT, and low inductance, L, transient current limit might be higher than 1.7A.
`
`4
`
`_______________________________________________________________________________________
`
`

`

`16VP-P Class G Amplifier with
`Inverting Boost Converter
`
`MAX9738
`
`Typical Operating Characteristics
`(VDD = VBAT = SHDN =+3.6V, GND = 0V, RISET = 100k(cid:60), RIN+ = RIN- = 10k(cid:60), RFB+ = RFB- = 10k(cid:60), CL = 1.6μF, RL= 20(cid:60), C1 = 10μF,
`C2 = 10μF, C3 = 0.1μF, C4 = 0.1μF, TA = +25°C, Typical Application Circuit.)
`
`TOTAL HARMONIC DISTORTION PLUS
`NOISE vs. FREQUENCY
`
`TOTAL HARMONIC DISTORTION PLUS
`NOISE vs. FREQUENCY
`
`TOTAL HARMONIC DISTORTION PLUS
`NOISE vs. FREQUENCY
`
`MAX9738 toc03
`
`VDD = 4.2V
`
`VOUT = 5.5VRMS
`
`VOUT = 2.4VRMS
`
`100
`
`1k
`FREQUENCY (Hz)
`
`10k
`
`100k
`
`10
`
`1
`
`0.1
`
`0.01
`
`THD+N (%)
`
`MAX9738 toc02
`
`VOUT = 5.5VRMS
`
`VOUT = 2VRMS
`
`VDD = 3.6V
`
`10
`
`1
`
`0.1
`
`0.01
`
`THD+N (%)
`
`MAX9738 toc01
`
`VOUT = 3.5VRMS
`
`VOUT = 1.2VRMS
`
`VDD = 2.7V
`
`10
`
`1
`
`0.1
`
`0.01
`
`THD+N (%)
`
`0.001
`
`10
`
`100
`
`1k
`FREQUENCY (Hz)
`
`10k
`
`100k
`
`0.001
`
`10
`
`100
`
`1k
`FREQUENCY (Hz)
`
`10k
`
`100k
`
`0.001
`
`10
`
`TOTAL HARMONIC DISTORTION PLUS
`NOISE vs. OUTPUT VOLTAGE
`
`TOTAL HARMONIC DISTORTION PLUS
`NOISE vs. OUTPUT VOLTAGE
`
`TOTAL HARMONIC DISTORTION PLUS
`NOISE vs. OUTPUT VOLTAGE
`
`MAX9738 toc06
`
`VDD = 4.2V
`
`fIN = 5kHz
`
`fIN = 10kHz
`
`10
`
`1
`
`0.1
`
`MAX9738 toc05
`
`VDD = 3.6V
`
`fIN = 5kHz
`
`fIN = 10kHz
`
`10
`
`1
`
`MAX9738 toc04
`
`10
`
`1
`
`0.1
`
`VDD = 2.7V
`
`fIN = 5kHz
`
`fIN = 10kHz
`
`fIN = 1kHz
`
`0
`
`1
`
`4
`3
`2
`5
`OUTPUT VOLTAGE (VRMS)
`
`6
`
`7
`
`MAX9738 toc09
`
`POWER-SUPPLY REJECTION RATIO
`
`VRIPPLE = 100mVP-P
`
`10
`
`100
`
`1k
`FREQUENCY (Hz)
`
`10k
`
`100k
`
`0.01
`
`0.001
`
`THD+N (%)
`
`fIN = 1kHz
`
`2
`5
`4
`3
`OUTPUT VOLTAGE (VRMS)
`
`6
`
`7
`
`SHUTDOWN CURRENT
`vs. SUPPLY VOLTAGE
`
`0.1
`
`0.01
`
`THD+N (%)
`
`0.001
`
`0
`
`1
`
`0
`
`-10
`
`-20
`
`-30
`
`-40
`
`-50
`
`-60
`
`-70
`
`-80
`
`-90
`
`PSRR (dB)
`
`MAX9738 toc08
`
`2.0
`
`2.5
`
`3.0
`3.5
`4.0
`4.5
`SUPPLY VOLTAGE (V)
`
`5.0
`
`5.5
`
`6.0
`
`1.0
`0.9
`0.8
`0.7
`0.6
`0.5
`0.4
`0.3
`0.2
`0.1
`0
`
`SHUTDOWN CURRENT (μA)
`
`fIN = 1kHz
`
`0
`
`1
`
`3
`2
`5
`4
`OUTPUT VOLTAGE (VRMS)
`
`6
`
`7
`
`TOTAL QUIESCENT CURRENT
`vs. SUPPLY VOLTAGE
`
`MAX9738 toc07
`
`IQ = IVDD + IVBAT
`
`2
`
`3
`
`4
`SUPPLY VOLTAGE (V)
`
`5
`
`6
`
`0.01
`
`0.001
`
`THD+N (%)
`
`17
`
`15
`
`13
`
`11
`
`79
`
`5
`
`TOTAL QUIESCENT CURRENT (mA)
`
`_______________________________________________________________________________________ 5
`
`

`

`16VP-P Class G Amplifier with
`Inverting Boost Converter
`
`Typical Operating Characteristics (continued)
`(VDD = VBAT = SHDN =+3.6V, GND = 0V, RISET = 100k(cid:60), RIN+ = RIN- = 10k(cid:60), RFB+ = RFB- = 10k(cid:60), CL = 1.6μF, RL= 20(cid:60), C1 = 10μF,
`C2 = 10μF, C3 = 0.1μF, C4 = 0.1μF, TA = +25°C, Typical Application Circuit.)
`
`POWER DISSIPATION
`vs. OUTPUT VOLTAGE
`
`POWER DISSIPATION
`vs. OUTPUT VOLTAGE
`
`MAX9738
`
`POWER DISSIPATION (mW)
`
`6.6
`
`6.4
`
`6.2
`
`6.0
`
`5.8
`
`5.6
`
`5.4
`
`OUTPUT VOLTAGE (VRMS)
`
`POWER DISSIPATION
`vs. OUTPUT VOLTAGE
`
`MAX9738 toc12
`
`PACKAGE DISSIPATION LIMIT
`
`VDD = 4.2V, fIN = 1kHz
`
`0
`
`1
`
`3
`2
`4
`OUTPUT VOLTAGE (VRMS)
`
`5
`
`6
`
`1000
`900
`800
`700
`600
`500
`400
`300
`200
`100
`0
`
`POWER DISSIPATION (mW)
`
`MAX9738 toc11
`
`PACKAGE DISSIPATION LIMIT
`
`VDD = 3.6V, fIN = 1kHz
`
`0
`
`1
`
`2
`4
`3
`OUTPUT VOLTAGE (VRMS)
`
`5
`
`6
`
`STARTUP WAVEFORM
`
`MAX9738 toc14
`
`SHUTDOWN WAVEFORM
`
`MAX9738 toc15
`
`SHDN
`5V/div
`
`OUT+ - OUT-
`500mV/div
`
`SHDN
`5V/div
`
`OUT+ - OUT-
`500mV/div
`
`1000
`900
`800
`700
`600
`500
`400
`300
`200
`100
`0
`
`POWER DISSIPATION (mW)
`
`MAX9738 toc10
`
`PACKAGE DISSIPATION LIMIT
`
`VDD = 2.7V, fIN = 1kHz
`
`0
`
`1
`
`3
`2
`OUTPUT VOLTAGE (VRMS)
`
`4
`
`5
`
`MAXIMUM OUTPUT VOLTAGE
`vs. VBAT SUPPLY
`
`MAX9738 toc13
`
`1000
`900
`800
`700
`600
`500
`400
`300
`200
`100
`0
`
`2.5
`
`3.0
`
`4.0
`3.5
`4.5
`VBAT SUPPLY (V)
`
`1% THD+N
`
`5.0
`
`5.5
`
`10ms/div
`
`10ms/div
`
`MAX9738 toc18
`
`EFFICIENCY
`vs. VSS LOAD CURRENT
`
`VDD = 3.6V
`DC LOAD ON VSS ONLY
`INPUT AC-GROUNDED
`NO LOAD ON AMPLIFIER
`
`0
`
`50
`
`200
`100
`150
`300
`250
`VSS LOAD CURRENT (mA)
`
`350
`
`400
`
`90
`
`80
`
`70
`
`60
`
`50
`
`40
`
`30
`
`20
`
`10
`
`0
`
`CLASS G OUTPUT WAVEFORM
`
`MAX9738 toc16
`
`VSS RIPPLE WITH 1kHz OUTPUT WAVEFORM
`
`MAX9738 toc17
`
`EFFICIENCY (%)
`
`VSS
`500mV/div
`
`OUT+ - OUT-
`10V/div
`
`OUT+
`5V/div
`
`OUT-
`5V/div
`
`OUT+ - OUT-
`10V/div
`
`1% THD+N
`
`200μs/div
`
`1% THD+N
`
`200μs/div
`
`6
`
`_______________________________________________________________________________________
`
`

`

`MAX9738
`
`16VP-P Class G Amplifier with
`Inverting Boost Converter
`
`Typical Operating Characteristics (continued)
`(VDD = VBAT = SHDN =+3.6V, GND = 0V, RISET = 100k(cid:60), RIN+ = RIN- = 10k(cid:60), RFB+ = RFB- = 10k(cid:60), CL = 1.6μF, RL= 20(cid:60), C1 = 10μF,
`C2 = 10μF, C3 = 0.1μF, C4 = 0.1μF, TA = +25°C, Typical Application Circuit.)
`
`BOOST CONVERTER-INDUCTOR
`CURRENT SCOPE PHOTO (3.6V)
`
`MAX9738 toc19
`
`fIN = 10kHz
`
`BOOST CONVERTER-INDUCTOR
`CURRENT SCOPE PHOTO (3.6V)
`
`MAX9738 toc20
`
`fIN = 10kHz
`
`LX
`10V/div
`
`IINDUCTOR
`1A/div
`
`ILOAD
`500mV/div
`
`OUT+ - OUT-
`10V/div
`
`20μs/div
`
`4μs/div
`
`BOOST CONVERTER-INDUCTOR
`CURRENT SCOPE PHOTO (4.2V)
`
`MAX9738 toc21
`
`fIN = 10kHz
`
`BOOST CONVERTER-INDUCTOR
`CURRENT SCOPE PHOTO (4.2V)
`
`MAX9738 toc22
`
`fIN = 10kHz
`
`LX
`10V/div
`
`IINDUCTOR
`1A/div
`
`ILOAD
`500mV/div
`
`OUT+ - OUT-
`10V/div
`
`LX
`10V/div
`
`IINDUCTOR
`1A/div
`
`ILOAD
`500mV/div
`
`OUT+ - OUT-
`10V/div
`
`LX
`10V/div
`
`IINDUCTOR
`1A/div
`
`ILOAD
`500mV/div
`
`OUT+ - OUT-
`10V/div
`
`4μs/div
`
`FREQUENCY RESPONSE
`
`MAX9738 toc24
`
`VOUT = 2VRMS
`
`10
`
`100
`
`1k
`FREQUENCY (Hz)
`
`10k
`
`100k
`
`20
`
`18
`
`16
`14
`
`12
`10
`
`26 48
`
`0
`
`GAIN (dB)
`
`20μs/div
`
`OUTPUT AMPLITUDE
`vs. FREQUENCY
`
`MAX9738 toc23
`
`VDD = 4.2V
`
`VDD = 2.7V
`
`VDD = 3.6V
`
`10
`
`100
`
`1k
`FREQUENCY (Hz)
`
`1% THD+N
`
`10k
`
`100k
`
`12345678
`
`0
`
`OUTPUT AMPLITUDE (VRMS)
`
`_______________________________________________________________________________________ 7
`
`

`

`16VP-P Class G Amplifier with
`Inverting Boost Converter
`
`Pin Description
`
`PIN
`A1, A2
`A3
`A4
`A5
`B1, B2
`B4
`B5
`C1
`
`C2, C4
`
`C5
`D1, D5
`D2
`D3
`D4
`
`NAME
`VBAT
`SHDN
`
`FB-
`IN-
`LX
`FB+
`IN+
`BST
`
`VSS
`
`ISET
`VDD
`OUT-
`GND
`OUT+
`
`FUNCTION
`Battery Connection. Bypass to GND with a 10μF ceramic capacitor.
`Active-Low Shutdown. Connect to VDD for normal operation.
`Negative Polarity Amplifier Feedback
`Negative Polarity Amplifier Input
`Inverting-Boost Inductor Connection. Connect a 1.5μH to 2.2μH inductor between LX and GND.
`Positive Polarity Amplifier Feedback
`Positive Polarity Amplifier Input
`Boost Flying Capacitor Connection. Connect a 0.1μF capacitor between BST and LX.
`
`Class G Amplifier Negative Power-Supply Input. Connect to inverting boost converter output
`node. Bypass VBAT with a 10μF ceramic capacitor.
`Boost Current Set. Connect a 100kΩ resistor from ISET to GND.
`Power-Supply Input. Connect to VBAT.
`Negative Polarity Amplifier Output
`Ground
`Positive Polarity Amplifier Output
`
`MAX9738
`
`Detailed Description
`The MAX9738 Class G power amplifier with inverting
`boost converter is the latest in linear amplifier technolo-
`gy. The Class G output stage offers improved perfor-
`mance over a Class AB amplifier while increasing
`efficiency to extend battery life. The integrated inverting
`boost converter generates a negative supply capable
`of delivering up to 400mA. The negative supply is only
`used when the output signal requires a larger supply
`voltage differential. As the battery voltage drops, the
`boost converter output becomes more negative to
`maintain amplifier output swing all the way down to
`VBAT = 2.7V.
`The Class G output stage and the inverting boost con-
`verter allow the MAX9738 to deliver a 16VP-P voltage
`swing, up to four times greater than a Class AB amplifier.
`Class G Operation
`The MAX9738 Class G amplifier is a linear amplifier that
`operates within a low (VDD to GND) and high (VDD to
`VSS) supply range. Figure 1 illustrates the transition
`from the low to high supply range. For small signals,
`the device operates within the lower (VDD to GND) sup-
`ply range. In this range, the operation of the device is
`identical to a traditional single-supply Class AB amplifi-
`er where:
`
`ILOAD = IN1
`
`As the output signal increases so a wider supply is
`needed, the device begins its transition to the higher
`supply range (VDD to VSS) for the large signals. To
`ensure a seamless transition between the low and high
`supply ranges, both of the lower transistors are on so
`that:
`
`ILOAD = IN1+IN2
`As the output signal continues to increase, the transi-
`tion to the high supply is complete. The device then
`operates from the higher supply range, where the oper-
`ation of the device is identical to a traditional dual-sup-
`ply Class AB amplifier where:
`ILOAD = IN2
`During operation, the output common-mode voltage of
`the MAX9738 adjusts dynamically as the device transi-
`tions between supply ranges.
`Utilizing a Class G output stage with an inverting boost
`converter allows the MAX9738 to realize a 17.5VP-P
`output swing with a 5V supply. A traditional Class AB
`amplifier would need to be powered with a ±5V supply
`to generate the same output swing at half the efficiency
`of the Class G.
`
`8
`
`_______________________________________________________________________________________
`
`

`

`16VP-P Class G Amplifier with
`Inverting Boost Converter
`
`MAX9738
`
`BTL CLASS G SUPPLY TRANSITION
`
`VDD
`
`ZL
`
`IP
`
`ON
`
`P
`
`VDD
`
`ZL
`
`IP
`
`ON
`
`P
`
`IN1
`
`N1
`
`ON
`
`N2
`
`OFF
`
`IN1
`
`IN2
`
`N1
`
`ON
`
`N1
`
`OFF
`
`N2
`
`ON
`
`IN2
`
`N2
`
`ON
`
`VSS
`
`SUPPLY TRANSITION
`IP = IN1 + IN2
`
`VSS
`
`HIGH SUPPLY RANGE OPERATION
`IP = IN2
`
`IP
`
`ON
`
`P
`
`VDD
`
`ZL
`
`VSS
`
`LOW SUPPLY RANGE OPERATION
`IP = IN1
`
`Figure 1. Class G Supply Transition
`
`Inverting Boost Converter
`The MAX9738 features an integrated inverting boost
`converter with an on-chip n-channel MOSFET to pro-
`vide an inverted supply rail that can supply up to
`400mA over the +2.7V to +5.5V positive supply range.
`The boost converter generates the negative supply rail
`(VSS) needed to create the higher supply range that
`allows the output of the device to operate over a
`greater dynamic range as the battery supply collapses
`over time. The converter uses a constant on-time,
`pulse-frequency modulation (PFM) architecture. The
`integrated MOSFET and the built-in soft-start function
`reduce the number of external components required
`while controlling inrush currents. The inverting boost
`regulator achieves soft-start by decreasing both peak
`inductor current limit and the constant on-time until VSS
`voltage reaches 90% of its regulation level.
`
`PFM Controller Block
`An error amplifier compares the output voltage to an
`internal target voltage. Once the output voltage is
`smaller than the regulation level, the controller sets a
`flip-flop, turning on the n-channel MOSFET and apply-
`ing the battery voltage across the inductor. The current
`through the inductor ramps up linearly, storing energy
`in its magnetic field. Once the on-time timer expires, or
`the inductor current reaches the current limit, the con-
`troller resets the flip-flop and turns off the MOSFET.
`Since the inductor current is continuous, a transverse
`potential develops across the inductor that turns on the
`diode (D1). This discharge condition forces the current
`through the inductor to ramp back down, transferring
`the energy stored in the magnetic field to the output
`capacitor and the load. The MOSFET remains off until
`the minimum off-time is expired or the output voltage is
`above the regulation level.
`
`_______________________________________________________________________________________ 9
`
`

`

`16VP-P Class G Amplifier with
`Inverting Boost Converter
`
`CIN+
`
`RIN+
`
`CIN-
`
`RIN-
`
`RFB+
`
`RFB-
`
`MAX9738
`
`+
`
`-
`
`CLASS G
`OUTPUT
`STAGE
`
`FB+
`
`IN+
`
`IN-
`
`FB-
`
`Figure 2. Gain Setting
`
`Driving a Ceramic Speaker
`Applications that require a thin profile, such as today’s
`mobile phones, demand that components have a small
`form factor. Dynamic loudspeakers that use a cone and
`voice coil typically cannot conform to the height
`requirements. The option for these applications is to
`use a ceramic/piezoelectric loudspeaker.
`Ceramic speakers are much more capacitive than a
`conventional loudspeaker. Typical capacitance values
`for such a speaker can be greater than 1μF. High peak-
`to-peak voltage drive is required to achieve acceptable
`sound pressure levels. The high output voltage require-
`ment coupled with the capacitive nature of the speaker
`demand that the amplifier supply much more current at
`high frequencies than at lower frequencies. Above 5kHz
`the typical speaker impedance can be less than 20(cid:60).
`The MAX9738 is ideal for driving a capacitive ceramic
`speaker. The high boost converter current limit allows
`for a flat frequency response out to 20kHz while main-
`taining high output voltage swings. Figure 3 shows a
`typical circuit for driving a ceramic speaker.
`A 20(cid:60) series resistance is required between the ampli-
`fier output and the ceramic speaker load to ensure the
`output of the amplifier sees some fixed resistance at
`high frequencies when the speaker is essentially an
`electrical short.
`
`Shutdown Mode
`The MAX9738 has a shutdown mode that reduces power
`consumption and extends battery life. Driving SHDN low
`places the MAX9738 in a low-power (0.6μA) shutdown
`mode. Connect SHDN to VDD for normal operation.
`Click-and-Pop Suppression
`The MAX9738 Class G amplifier features Maxim’s com-
`prehensive, industry-leading click-and-pop suppres-
`sion. During startup, the click-and-pop suppression
`circuitry eliminates any audible transient sources inter-
`nal to the device.
`Applications Information
`Differential Input Amplifier
`The MAX9738 features a differential input configuration,
`making the device compatible with many CODECs, and
`offering improved noise immunity over a single-ended
`input amplifier. In devices such as PCs, noisy digital
`signals can be picked up by the amplifier’s input
`traces. The signals appear at the amplifiers’ inputs as
`common-mode noise. A differential input amplifier
`amplifies the difference of the two inputs, and signals
`common to both inputs are canceled out. When config-
`ured for differential inputs, the voltage gain of the
`MAX9738 is set by:
`
`MAX9738
`
`(
`
`)]
`
`dB
`
`)
`
`R R
`
`FB_
`IN_
`
`=
`
`A
`
`V
`
`
`
`20log[4 (
`
`×
`
`
`where AV is the desired voltage gain in dB. RIN+ should
`be equal to RIN-, and RFB+ should be equal to RFB-.
`The Class G output stage has a fixed gain of 4V/V
`(12dB). Any gain or attenuation set by the external
`input stage resistors add to or subtract from this fixed
`gain. See Figure 2.
`In differential input configurations, the common-mode
`rejection ratio (CMRR) is primarily limited by the exter-
`nal resistor and capacitor matching. Ideally, to achieve
`the highest possible CMRR the following external com-
`ponents should be selected where:
`=
`FB+
`FB-
`IN+
`IN-
`
`R R
`
`R R
`
`and
`
`C
`IN+
`
`=
`
`C
`IN-
`
`10
`
`______________________________________________________________________________________
`
`

`

`MAX9738
`
`16VP-P Class G Amplifier with
`Inverting Boost Converter
`
`discharging of the output capacitance, and the voltage
`drop across the capacitor’s ESR caused by the current
`into and out of the capacitor. The worst-case voltage
`ripple is:
`
`+
`V
`VSS_RIPPLE(ESR)
`1
`L
`×
`
`
`
`and
`
`t
`FON
`×
`
`R
`ESR
`
`
`
`where
`
`MAX9738
`
`CLASS G
`OUTPUT
`STAGE
`
`RL
`
`OUT+
`
`OUT-
`
`V
`VSS_RIPPLE
`
`=
`
`V
`VSS_RIPPLE(C)
`
`I
`L_RIPPLE
`
`V
`VSS_RIPPLE(C)
`×
`I
`L_RIPPLE2
`=
`×
`×
`1
`2 C V
`SS
`=
`I
`L_RIPPLE(ESR)
`
`×
`
`t
`FON
`
`V
`VSS_RIPPLE(ESR)
`V
`=
`BAT
`L
`1
`where IL_RIPPLE is the inductor ripple current. For
`ceramic capacitors, the output voltage ripple is typically
`dominated by VVSS_RIPPLE(C). The voltage rating and
`temperature characteristics of the output capacitor must
`also be considered. Note that all ceramic capacitors
`typically have large temperature coefficients and bias
`voltage coefficients. The actual capacitor value in the
`circuit is typically significantly less than the stated value.
`
`Figure 3. Driving a Ceramic Speaker
`
`Component Selection
`Input Coupling Capacitors (CIN_)
`The AC-coupling capacitors (CIN_) and input resistors
`(RIN_) form highpass filters that remove any DC bias from
`an input signal (see the Typical Application Circuit/
`Functional Diagram). CIN_ blocks the input signal source
`from appearing at the amplifier outputs. The -3dB point of
`the highpass filter, assuming zero source impedance due
`to the input signal source, is given by:
`
`
`f dB3
`−
`
`=
`
`1
`R
`IN
`
`π
`
`×
`
`2
`
`×
`
`C
`IN
`
`(
`Hz
`
`)
`
`Ceramic speakers generally perform best at frequen-
`cies greater than 1kHz. To reduce low-frequency dis-
`tortion that may be added by the ceramic speakers
`low-frequency response, select a CIN such that the
`f-3dB closely matches the low-frequency response of
`the ceramic speaker. Use capacitors with low-voltage
`coefficient dielectrics. Aluminum electrolytic, tantalum,
`or film dielectric capacitors are good choices for AC-
`coupling capacitors. Capacitors with high-voltage coef-
`ficients, such as ceramics (non-C0G dielectrics), can
`result in increased distortion at low frequencies.
`
`Boost Converter Output Capacitor Selection (C1)
`The total output voltage ripple has two components: the
`capacitive ripple caused by the charging and
`
`Input Filter Capacitor (C2)
`The input capacitor reduces the current peaks drawn
`from the input supply and reduces noise injection into
`the IC. A 10μF ceramic capacitor is recommended for
`the Typical Applications Circuit/Functional Diagram
`because of the high-source impedance seen in typical
`lab setups. Actual applications usually have much
`lower source impedance since the step-up regulator
`often runs directly from a battery. Typically, the input
`capacitance can be reduced below 10μF.
`
`Boost Flying Capacitor (C3)
`A bootstrap circuit that uses an external flying capaci-
`tor between LX and BST provides the supply voltage
`for the internal n-channel MOSFET driver. A 0.1μF or
`larger ceramic capacitor provides sufficient current for
`the internal MOSFET driver supply.
`
`Inductor Selection
`The MAX9738 operates with a standard 2.2μH inductor
`for the entire range of supply voltages and load cur-
`rents. The inductor must have a saturation (incremen-
`tal) current (ISAT) rating greater than the peak switching
`current. Choose an inductor that has a higher ISAT rat-
`ing than the given FET Current Limit (Transient) specifi-
`cation in the Electrical Characteristics table.
`Temperature characteristics of the inductor’s saturation
`current must also be considered.
`
`______________________________________________________________________________________ 11
`
`

`

`16VP-P Class G Amplifier with
`Inverting Boost Converter
`
`IMPEDANCE vs. FREQUENCY
`
`MAX9738 fig04
`
`1μF CAPACITOR
`
`CERAMIC
`SPEAKER
`
`1M
`
`100k
`
`10k
`
`1k
`
`100
`
`IMPEDANCE (Ω)
`
`10
`0.001
`
`0.01
`
`0.1
`1
`FREQUENCY (Hz)
`
`10
`
`100
`
`Figure 4. Ceramic Speaker and Capacitor Impedance
`
`the value of RL burdens the amplifier output stage with
`more power dissipation. An RL of 20(cid:60) is a good com-
`promise between power dissipation and frequency
`response when coupled with a typical ceramic speaker.
`WLP Applications Information
`For the latest application details on WLP construction,
`dimensions, tape carrier information, PCB techniques,
`bump-pad layout, and recommended reflow tempera-
`ture profile, as well as the latest information on reliability
`testing results, go to the Maxim website at www.maxim-
`ic.com/ucsp for Application Note 1891: UCSP—A
`Wafer-Level Chip-Scale Package.
`
`Rectifier Diode Selection
`The MAX9738’s high-switching frequency demands a
`high-speed rectifier. Schottky diodes are recommend-
`ed for most applications because of their fast recovery
`time and low forward voltage. In general, a 1A to 2A
`Schottky diode complements the internal MOSFET.
`Ceramic Speaker Impedance
`Characteristics
`A 1μF capacitor is a good model for the ceramic
`speaker as it best approximates the impedance of a
`ceramic speaker over the audio band. When selecting
`a capacitor to simulate a ceramic speaker, the capaci-
`tor’s voltage rating must be equal to or higher than the
`expected amplifier output voltage swing.
`Series Load Resistor
`The capacitive nature of the ceramic speaker results in
`very low impedances at high frequencies. To prevent
`the ceramic speaker from shorting the amplifier output
`at high frequencies, a series load resistor must be
`used. The output load resistor and the ceramic speaker
`create a lowpass filter. To set the rolloff frequency of
`the output filter, the approximate capacitance of the
`speaker must be known. This information can be
`obtained from bench testing or from the ceramic
`speaker manufacturer. Set the lowpass filter cutoff fre-
`quency with the following equation:
`
`=
`
`fLP
`
`1
`×
`R C
`L
`
`π
`
`×
`
`2
`
`SPEAKER
`
`(
`Hz
`
`)
`
`Increasing the value of RL decreases the amount of
`high-frequency audio content sent to the speaker, but
`improves the MAX9738’s power dissipation. Lowering
`
`MAX9738
`
`12
`
`______________________________________________________________________________________
`
`

`

`MAX9738
`
`16VP-P Class G Amplifier with
`Inverting Boost Converter
`
`Typical Application Circuit/Functional Diagram
`
`VDD
`
`C2
`10μF
`
`VDD
`
`VDD
`
`VBAT
`
`VBAT
`
`ISET
`
`VREF
`
`BOOST
`REGULATOR
`CONTROL
`
`SHDN
`
`SHUTDOWN
`LOGIC
`
`C4
`0.1μF
`
`VDD
`
`RFB+
`10kΩ
`
`RFB-
`10kΩ
`
`RSET
`100kΩ
`
`AUDIO
`INPUT
`
`CIN
`0.47μF
`
`RIN+
`10kΩ
`
`CIN
`0.47μF
`
`RIN-
`10kΩ
`
`FB+
`
`IN+
`
`IN-
`
`FB-
`
`VBAT
`
`C1
`10μF
`
`C3
`0.1μF
`
`D1
`
`L2
`
`.2μH
`
`RL
`20Ω
`
`CL = CSPEAKER
`1.6μF
`
`VSS
`
`VSS
`
`BST
`
`LX
`
`LX
`
`OUT+
`
`OUT-
`
`CLASS G
`OUTPUT
`STAGE
`
`GND
`
`MAX9738
`
`PIEZOELECTRIC
`SPEAKER
`
`______________________________________________________________________________________ 13
`
`

`

`16VP-P Class G Amplifier with
`Inverting Boost Converter
`
`Pin Configuration
`
`Chip Information
`
`PROCESS: BiCMOS
`
`TOP VIEW
`(BUMP SIDE DOWN)
`
`A
`
`B
`
`C
`
`D
`
`1
`
`2
`
`MAX9738
`3
`
`4
`
`5
`
`VBAT
`
`VBAT
`
`SHDN
`
`FB-
`
`IN-
`
`LX
`
`LX
`
`FB+
`
`IN+
`
`BST
`
`VSS
`
`VSS
`
`ISET
`
`VDD
`
`OUT-
`
`GND
`
`OUT+
`
`VDD
`
`20-BUMP
`WLP
`
`Package Information
`For the latest package outline information, go to
`www.maxim-ic.com/packages.
`
`PACKAGE TYPE
`5x4 WLP
`
`PACKAGE CODE
`W202A2+1
`
`DOCUMENT NO.
`21-0059
`
`MAX9738
`
`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
`
`© 2008 Maxim Integrated Products
`
`is a registered trademark of Maxim Integrated Products, Inc.
`
`