LM4962
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SNAS300D – NOVEMBER 2005 – REVISED APRIL 2013
LM4962
Ceramic Speaker Driver
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FEATURES
DESCRIPTION
•
The LM4962 is an audio power amplifier primarily
designed for driving Ceramic Speaker for applications
in Cell Phones, Smart Phones, PDA's and other
portable applications. It is capable of driving 15Vpp
(typ) BTL with less than 1% THD+N from a 3.2VDC
power supply. The LM4962 features and low power
consumption shutdown mode, an internal thermal
shutdown protection mechanism, along with over
current protection (OCP) and over voltage protection
(OVP).
1
2
•
•
•
•
•
•
•
•
•
•
•
Click and Pop Circuitry Eliminates Noise
During Turn-On and Turn-Off Transitions
Low Current Shutdown Mode
Low Quiescent Current
Mono 15Vp-p BTL Output, RL = 2μF+9.4Ω,
f = 1kHz, 1% THD+N
Over-Current Protection
Over-Voltage Protection
Unity-Gain Stable
External Gain Configuration Capability
Including Band Switch Function
Leakage Cut Switch (SW-LEAK)
Soft-Start Function
Space-Saving DSBGA Package (2mm x 2.5mm)
APPLICATIONS
•
•
•
•
•
Smart Phones
Mobile Phones and Multimedia Terminals
PDA's, Internet Appliances, and Portable
Gaming
Portable DVD
Digital Still Cameras/Camcorders
Boomer audio power amplifiers were designed
specifically to provide high quality output power with a
minimal number of external components. The
LM4962 does not require bootstrap capacitors, or
snubber circuits.
The LM4962 also features a Band-Switch function
which allows the user to use one amplifier device for
both receiver (earpiece) mode and ringer/loudspeaker
mode.
The LM4962 contains advanced click and pop
circuitry that eliminates noises which would otherwise
occur during turn-on and turn-off transitions.
Additionally, the internal boost converter features a
soft-start function.
The LM4962 is unity-gain stable and can be
configured by external gain-setting resistors.
KEY SPECIFICATIONS
•
•
•
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Quiescent Power Supply Current
(Boost Converter + Amplifier): 9 mA (typ)
Voltage Swing in BTL at 1% THD,
f = 1kHz: 15 Vp-p (typ)
Shutdown Current: 0.1 μA (typ)
OVP: 8.5V < VAMP < 9.5 V
1
2
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.
All 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 © 2005–2013, Texas Instruments Incorporated
LM4962
SNAS300D – NOVEMBER 2005 – REVISED APRIL 2013
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Connection Diagram
Top View
1
2
3
4
A
SDAmp
SDBoost
GND
(SW)
SW
B
SoftStart
Flagout
VDD
BootStrap
C
Bypass
CCHG
VIN
OC/OV
Detect
GND
BW2
BW1
FB
VO1
VAMP
VO2
SWLeak
D
E
Figure 1. DSBGA Package
See Package Number YZR002011A
2
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Typical Application
L1
10 PH
D2
V1 = 1.2(1+R2/R5)
Vdd
R3
1.6k
Cs1
4.7 PF
Vdd
SW
R2
25k
C3
100p
C2
4.7 PF
FB
GND (sw)
R5
4.9k
Soft-Start
Css
10 nF
SW-LEAK
Bootstrap
Flagout
Flagout
OC/OV Detect
Rs
100m
Vamp
Cs2
4.7 PF
Shutdown 1
SD Boost
Shutdown 2
SD Amp
GND
To LM4951
for stereo
solution
Bypass
Cb1
1.0 PF
Ro1
4.7
Vo2
Rchg1
1k
Ceramic Speaker
2.0 PF
Cchg
Ro2
4.7
CinA
0.1 PF
Vo1
Vin
Load
RinA
20k
BW1
BW2
Rf1
200k
Rf2
20k
Cf1
82 pF
Figure 2. Typical Audio Amplifier Application Circuit
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Block Diagram
VDD
L1
D2
Cs1
C2
R3
R2
C3
SW
VDD
FB
Driver
+
R5
V BG
PWM
SW-LEAK
GND(SW)
GND
LM4962
Rs
Vamp
Cs2
CinA
RinA
VIN
Rchg1
BW1
Rf1
BW2
Rf2
Cchg
Cf1
Flagout
flagout
Cf2
-
Vo1
Soft-Start
Css
Bypass
BIAS, SHUTDOWN,
and
PROTECTION
CIRCUITRY
+
Ro1
Cb1
V IH
SD Amp
V IL
Shutdown
control
V IH
V IL
Shutdown
control
Ro2
+
Vo2
-
SD Boost
OC/OV Detect
GND
Figure 3. LM4962 Block Diagram
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.
4
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Absolute Maximum Ratings (1)
(2) (3)
Supply Voltage (VDD)
9.5V
Amplifier Supply Voltage (VAMP)
9.5V
−65°C to +150°C
Storage Temperature
−0.3V to VDD + 0.3V
Input Voltage
(4)
Internally limited
ESD Susceptibility (5)
2000V
ESD Susceptibility (6)
200V
Power Dissipation
Junction Temperature
Thermal Resistance
(1)
(2)
(3)
(4)
(5)
(6)
(7)
150°C
θJA (DSBGA) (7)
73°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.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
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 given in Absolute Maximum Ratings, whichever is
lower.
Human body model, 100pF discharged through a 1.5kΩ resistor.
Machine Model, 220pF–240pF discharged through all pins.
The value for a θJA is measured with the LM4962 mounted on a 3” x 1.5” 4 layer board. The copper thickness for all 4 layers is 0.5oz
(roughly 0.18mm).
Operating Ratings
Temperature Range (TMIN ≤ TA ≤ TMAX) (1)
−40°C ≤ TA ≤ +85°C
Supply Voltage (VDD)
3.0V < VDD < 5.0V
Amplifier Supply Voltage (V1) (2)
(1)
(2)
2.7V < VAMP < 9.0V
Temperature range is tentative, pending characterization.
An amplifier supply voltage of 9.0V can only be obtained when the over current and over voltage protection circuitry is disabled (OV/OC
Detect pin is disabled).
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Electrical Characteristics
The following specifications apply for VDD = 3.2V, AV-BTL = 26dB, ZL = 2µF+9.4Ω, Cb = 1.0μF, R2 = 25KΩ, R5 = 4.9KΩ unless
otherwise specified. Limits apply for TA = 25°C.
Parameter
LM4962
Test Conditions
Typ (1)
Limit (2) (3)
Units
(Limits)
IDD
Quiescent Power Supply Current
in Boosted Ringer Mode
VIN = 0V,
9
12
mA (max)
Iddrcv
Quiescent Power Supply Current
in Receiver Mode
SD Boost = GND
SD Amp = VDD
3
5
mA (max)
ISD
Shutdown Current (4)
SD Boost = SD Amp = GND
0.1
2.0
µA (max)
VLH
Logic High Threshold Voltage
For SD Boost, SD Amp
1.2
V (min)
VLL
Logic Low Threshold Voltage
For SD Boost, SD Amp
0.4
V (max)
RPULLDOWN
Pulldown Resistor
For SD Amp, SD Boost
80
60
kΩ (min)
TWUBC
Boost Converter Wake-up Time
CSS = 10nF
2
5
ms (max)
TWUA
Audio Amplifier Wake-up Time
(For Vdd = 2.7V to 8.5V)
20
40
msec
VOUT
Output Voltage Swing
THD = 1% (max), f = 1kHz
15
14
Vpp (min)
THD+N
Total Harmonic Distortion + Noise
Vout = 14Vpp, f = 1kHz
0.4
1.0
εOS
Output Noise
A-Weighted Filter, VIN = 0V
125
PSRR
Power Supply Rejection Ratio
VRIPPLE = 200mVp-p, f = 100Hz,
Input Referred
86
71
dB (min)
Ron-sw-leak
On Resistance on SW-Leak
SD Boost = GND
Isink = 100μA
30
50
Ω (max)
Ron
Flagout On resistance
Isink = 1mA
50
100
Ω (max)
Vovp
Sensitivity of Over Voltage Protection Flagout = GND
on VAMP
9.0
9.5
8.5
V (max)
V (min)
Vocp
Sensitivity of Over Current Protection Flagout = GND
(Voltage Across RS)
185
275
75
mV (max)
mV (min)
Ileak
Leak Current on Flagout pin
2
μA (max)
ISW
SW Current Limit
2
2.7
A (max)
1.2
A (min)
150
°C (min)
TSD
Thermal Shutdown Temperature
Vos
Output Offset Voltage
VFB
Feedback Voltage
(1)
(2)
(3)
(4)
6
Vflagout = VDD
SD Boost = VDD
SD Amp = VDD
%
µV
5
25
mV
1.23
1.15
1.31
V (min)
V (max)
Typicals are measured at 25°C and represent the parametric norm.
Limits are specified to AOQL (Average Outgoing Quality Level).
Datasheet min/max specification limits are specified by design, test, or statistical analysis.
Shutdown current is measured in a normal room environment. The Shutdown pin should be driven as close as possible to Vin for
minimum shutdown current.
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Typical Performance Characteristics
THD+N vs Frequency
VDD = 3.2V, VO = 4.95VRMS, ZL = 2μF+9.4Ω
THD+N vs Frequency
VDD = 4.2V, VO = 4.95VRMS, ZL = 2μF+9.4Ω
10
10
5
5
2
2
1
THD+N (%)
THD+N (%)
1
0.5
0.2
0.1
0.5
0.2
0.1
0.05
0.05
0.02
0.02
0.01
100
300
1k
10k
4k
2k
0.01
100
300
FREQUENCY (Hz)
4k
2k
1k
10k
FREQUENCY (Hz)
Figure 4.
Figure 5.
THD+N vs Frequency
VDD = 5V, VO = 4.95VRMS, ZL = 2μF+9.4Ω
THD+N vs Output Voltage Swing
= 3.2V, ZL = 2μF+9.4Ω, f = 1kHz
VDD
10
10
5
5
f = 1 kHz
f = 10 kHz
2
2
1
THD+N (%)
THD+N (%)
1
0.5
0.2
0.5
0.2
0.1
f = 100 Hz
0.05
0.1
0.02
0.05
0.01
20m 50m
0.02
0.01
100
200m 500m 1
2
5
10
OUTPUT VOLTAGE SWING (Vrms)
300
1k
4k
2k
10k
FREQUENCY (Hz)
10
5
Figure 6.
Figure 7.
THD+N vs Output Voltage Swing
VDD = 4.2V, ZL = 2μF+9.4Ω, f = 1kHz
THD+N vs Output Voltage Swing
VDD = 5V, ZL = 2μF+9.4Ω, f = 1kHz
10
5
f = 1 kHz
2
2
1
1
f = 1 kHz
THD+N (%)
THD+N (%)
f = 10 kHz
0.5
0.2
f = 10 kHz
0.1
0.05
0.5
0.2
0.1
0.05
f = 100 Hz
0.02
f = 100 Hz
0.02
0.01
20m 50m
200m 500m 1
2
5
10
0.01
20m 50m
OUTPUT VOLTAGE SWING (Vrms)
200m 500m 1
2
5
10
OUTPUT VOLTAGE SWING (Vrms)
Figure 8.
Figure 9.
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Typical Performance Characteristics (continued)
PSRR vs Frequency
VDD = 3.2, ZL = 2μF+9.4Ω, VRIPPLE = 200mVP-P
PSRR vs Frequency
VDD = 4.2, ZL = 2μF+9.4Ω, VRIPPLE = 200mVP-P
0
-10
-10
-20
-20
-30
-30
-40
-40
PSRR (dB)
PSRR (dB)
0
-50
-60
-50
-60
-70
-70
-80
-80
-90
-90
-100
-100
20
1k
100
5k
20k
20
5k
20k
FREQUENCY (Hz)
Figure 10.
Figure 11.
PSRR vs Frequency
VDD = 5, ZL = 2μF+9.4Ω, VRIPPLE = 200mVP-P
Frequency Response vs Input Capacitor Size
0
20
16
-20
12
OUTPUT LEVEL (dB)
-10
-30
PSRR (dB)
1k
100
FREQUENCY (Hz)
-40
-50
-60
-70
-80
Ci = 1.0 PF
8
4
0
-4
-8
-12
Ci = 0.039 PF
-16
Ci = 0.39 PF
-20
-90
-24
-28
-100
20
100
1k
5k
20k
20
50 100 200 500
1k 2k
5k 10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 12.
Figure 13.
Boost Efficiency vs Output Voltage Swing
f = 1kHz, ZL = 2μF+9.4Ω
Inductor Current vs Output Voltage Swing
f = 1kHz, ZL = 2μF+9.4Ω
100
200
VDD = 5V
INDUCTOR CURRENT (mA)
BOOST EFFICIENCY (%)
95
90
VDD = 3V
85
80
VDD = 4.2V
75
70
0
1
2
3
150
VDD = 4.2V
100
50
VDD = 5V
0
4
5
6
0
1
2
3
4
5
6
OUTPUT VOLTAGE SWING (Vrms)
OUTPUT VOLTAGE SWING (Vrms)
Figure 14.
8
VDD = 3V
Figure 15.
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Typical Performance Characteristics (continued)
12
Supply Current vs Supply Voltage
Feedback Voltage vs Temperature
1.26
1.25
FEEDBACK VOLTAGE (V)
SUPPLY CURRENT (mA)
10
8
6
4
2
0
2.5
3.5
3.0
4.0
5.0
4.5
1.24
1.23
1.22
1.21
1.20
1.19
-60 -40
5.5
-20
SUPPLY VOLTAGE (V)
20
40
80 100
60
TEMPERATURE (°C)
Figure 16.
Figure 17.
VOCP vs Vamp
250
0
1200
Rds(on) vs VBOOTSTRAP
1000
200
Rds(on) (m:)
VOCP (V)
800
150
100
50
600
400
200
0
2
4
6
8
10
0
2.5
3.5
4.5
5.5
6.5
7.5
8.5
BOOTSTRAP VOLTAGE (V)
VAMP (V)
Figure 18.
Figure 19.
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APPLICATION INFORMATION
BRIDGE CONFIGURATION EXPLANATION
The Audio Amplifier portion of the LM4962 has two internal amplifiers allowing different amplifier configurations.
The first amplifier’s gain is externally configurable, whereas the second amplifier is internally fixed in a unity-gain,
inverting configuration. The closed-loop gain of the first amplifier is set by selecting the ratio of Rf to Ri while the
second amplifier’s gain is fixed by the two internal 20kΩ resistors. Figure 2 shows that the output of amplifier one
serves as the input to amplifier two. This results in both amplifiers producing signals identical in magnitude, but
out of phase by 180°. Consequently, the differential gain for the Audio Amplifier is
AVD = 2 *(Rf/Ri)
(1)
By driving the load differentially through outputs Vo1 and Vo2, an amplifier configuration commonly referred to as
“bridged mode” is established. Bridged mode operation is different from the classic single-ended amplifier
configuration where one side of the load is connected to ground.
A bridge amplifier design has a few distinct advantages over the single-ended configuration. It provides
differential drive to the load, thus doubling the output swing for a specified supply voltage.
BOOST CONVERTER POWER DISSIPATION
At higher duty cycles, the increased ON-time of the switch FET means the maximum output current will be
determined by power dissipation within the LM4962 FET switch. The switch power dissipation from ON-time
conduction is calculated by Equation (2).
PD(SWITCH) = DC x IIND(AVE)2 x RDS(ON)
(2)
where:
DC is the duty cycle.
There will be some switching losses as well, so some derating needs to be applied when calculating IC power
dissipation.
MAXIMUM AMPLIFIER POWER DISSIPATION
Power dissipation is a major concern when designing a successful amplifier, whether the amplifier is bridged or
single-ended. A direct consequence of the increased power delivered to the load by a bridge amplifier is an
increase in internal power dissipation. Since the amplifier portion of the LM4962 has two operational amplifiers,
the maximum internal power dissipation is 4 times that of a single-ended amplifier. The maximum power
dissipation for a given BTL application can be derived from Equation (3).
PDMAX(AMP) = (2VDD 2) / (π2RL)
(3)
where:
RL = Ro1 + Ro2
MAXIMUM TOTAL POWER DISSIPATION
The total power dissipation for the LM4962 can be calculated by adding Equation (2) and Equation (3) together
to establish Equation (4):
PDMAX(TOTAL) = (2VDD 2) / (π2EFF2RL)
(4)
where:
EFF = Efficiency of boost converter
RL = Ro1 + Ro2
The result from Equation (4) must not be greater than the power dissipation that results from Equation (5):
PDMAX = (TJMAX - TA) / θJA
10
(5)
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For the LQA28A, θJA = 73°C/W. TJMAX = 125°C for the LM4962. Depending on the ambient temperature, TA, of
the system surroundings, Equation (5) can be used to find the maximum internal power dissipation supported by
the IC packaging. If the result of Equation (4) is greater than that of Equation (5), then either the supply voltage
must be increased, the load impedance increased or TA reduced. 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.
START-UP SEQUENCE
For the LM4962 correct start-up sequencing is important for optimal device performance. Using the correct start
up sequence will improve click/pop performance as well as avoid transients that could reduce battery life. For
ringer/loudspeaker mode, the supply voltage should be applied first and both the boost converter and the
amplifier should be in shutdown. The boost converter can then be activated followed by the amplifier (see timing
diagram, Figure 20). If the boost converter shutdown is toggled while the amplifier is active a very audible pop
will be heard.
SHUTDOWN FUNCTION
In many applications, a microcontroller or microprocessor output is used to control the shutdown circuitry to
provide a quick, smooth transition into shutdown. Another solution is to use a single-pole, single-throw switch
connected between VDD and Shutdown pins.
BAND SWITCH FUNCTION
The LM4962 features a Band Switch function which allows the user to use one amplifier for both receiver
(earpiece) mode and ringer/loudspeaker mode. When the boost converter and the amplifier are both active the
device is is in ringer mode. This enables the boost converter and sets the externally configurable closed loop
gain selection to BW1. If the boost converter is in the shutdown and the amplifier is active the device is in
receiver mode. In this mode the gain selection is switched to BW2. This allows the amplifier to be powered
directly from the battery minus the voltage drop across the Schottky diode.
SD Boost
SD Amp
Receiver Mode (BW2)
Low
High
Boosted Ringer Mode (BW1)
High
High
Shutdown
Low
Low
BOOTSTRAP PIN
The bootstrap pin, featured in the LM4962, provides a voltage supply for the internal switch driver. Connecting
the bootstrap pin to V1 (See Figure 2) allows for a higher voltage to drive the gate of the switch thereby reducing
the Ron. This configuration is necessary in applications with heavier loads. The bootstrap pin can be connected
to VDD when driving lighter loads to improve device performance (Iddq, THD+N, Noise, etc.).
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Vdd
Battery
Voltage
0V
Vdd
Boost
Converter
Shutdown
0V
Vdd
Amplifier
Shutdown
0V
V1
V1 (output of
Boost
Converter)
Vdd-Vd*
Vamp/2
Vo1/Vo2
(Amplifier
DC Bias)
(Vdd-Vd)/2*
0V
Ringer Mode
Receiver Mode
*Vd = Voltage drop across diode D2
Figure 20. Power on Sequence Timing Diagram
OVER-CURRENT AND OVER-VOLTAGE PROTECTION FUNCTION
Flagout Pin The Flagout pin indicates a fault when an over current or over voltage condition has been detected.
The Flagout pin is high impedance when inactive. When active, the Flagout pin is pulled down to a 50Ω
short to GND.
Over-Voltage Protection (OVP) Operation When a voltage (Vamp) greater than 8.5V (min) is detected at the
OC/OV Detect pin, the LM4962 indicates a fault by activating the Flagout pin. The boost converter
momentarily shutdown and reinitialize the soft-start sequence. The Flagout pin will remain active until both
shutdowns pins are pulled low.
Over-Current Protection (OCP) Operation The OCP circuitry monitors the voltage across Rocd to detect the
output current of the boost converter. If a voltage greater than 185mV (typ) is detected the device will
shutdown and the Flagout pin will be activated. For the device to return to normal operation both shutdown
pins need to be pulled low to reset the Flagout pin.
Disable OCP The Over-Current Protection Circuitry can be disabled by shorting out RS. In this configuration the
OVP circuitry is still active.
Disable both OVP and OCP Both features can be disabled by grounding the OC/OV Detect pin. In this
configuration the Flagout pin will be inactive.
12
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Timing Diagrams
Vdd
Amplifier
Shutdown
0V
Vdd
Boost
Shutdown
0V
185 mV
Vscd *
0V
Vdd
Flagout
0V
On
Internal
Boost
Operation
Off
On
Internal
Amplifier
Operation
Off
t1 < 3 Ps
t1
* Vscd refers to the voltage differential across Rs
Figure 21. OCP Timing Diagram
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Vdd
Amplifier
Shutdown
0V
Vdd
Boost
Shutdown
0V
8.5V
7.5V
Vdd
Vamp
0V
Vdd
Flagout
0V
On
Internal
Boost
Operation
Off
On
Internal
Amplifier
Operation
Off
t3
t2
t1
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