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LM4670 Boomer™ Audio Power Amplifier Series Filterless High Efficiency 3W Switching
Audio Amplifier
Check for Samples: LM4670
1FEATURES DESCRIPTION
The LM4670 is a fully integrated single-supply high
23• No Output Filter Required for Inductive Loads efficiency switching audio amplifier. It features an
• Externally Configurable Gain innovative modulator that eliminates the LC output
• Very Fast Turn on Time: 1.35ms (Typ) filter used with typical switching amplifiers.
Eliminating the output filter reduces external
• Minimum External Components component count, simplifies circuit design, and
• "Click and Pop" Suppression Circuitry reduces board area. The LM4670 processes analog
• Micro-Power Shutdown Mode inputs with a delta-sigma modulation technique that
lowers output noise and THD when compared to
• Short Circuit Protection conventional pulse width modulators.
• Available in Space-Saving DSBGA and WSON
Packages The LM4670 is designed to meet the demands of
mobile phones and other portable communication
devices. Operating on a single 5V supply, it is
APPLICATIONS capable of driving a 4Ωspeaker load at a continuous
• Mobile Phones average output of 2.3W with less than 1% THD+N. Its
• PDAs flexible power supply requirements allow operation
from 2.4V to 5.5V.
• Portable Electronic Devices The LM4670 has high efficiency with speaker loads
KEY SPECIFICATIONS compared to a typical Class AB amplifier. With a 3.6V
supply driving an 8Ωspeaker, the IC's efficiency for a
• Efficiency at 3.6V, 100mW into 8ΩSpeaker, 100mW power level is 77%, reaching 88% at 600mW
77% (Typ) output power.
• Efficiency at 3.6V, 600mW into 8ΩSpeaker, The LM4670 features a low-power consumption
88% (Typ) shutdown mode. Shutdown may be enabled by
• Efficiency at 5V, 1W into 8ΩSpeaker, 87% driving the Shutdown pin to a logic low (GND).
(Typ) The gain of the LM4670 is externally configurable
• Quiescent Current, 3.6V Supply, 4.8mA (Typ) which allows independent gain control from multiple
• Total Shutdown Power Supply Current, 0.01µA sources by summing the signals.
(Typ)
• Single Supply Range, 2.4 to 5.5V
1Please 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.
2Boomer is a trademark of Texas Instruments.
3All other trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date. Copyright © 2004–2013, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
C
B
A
GND
Vo1
Vo2
IN+
VDD
IN-
2
GND
SHUTDOWN PVDD
31
LM4670
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Typical Application
Figure 1. Typical Audio Amplifier Application Circuit
Connection Diagram
Figure 2. 9 Bump DSBGA Package
Top View
See Package Number YZR0009
Figure 3. WSON Package
Top View
See Package Number NGQ0008A
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.
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Absolute Maximum Ratings(1)(2)
Supply Voltage(1) 6.0V
Storage Temperature −65°C to +150°C
Voltage at Any Input Pin VDD + 0.3V ≥V≥GND - 0.3V
Power Dissipation(3) Internally Limited
ESD Susceptibility(4) 2.0kV
ESD Susceptibility(5) 200V
Junction Temperature (TJMAX) 150°C
θJA (DSBGA) 220°C/W
Thermal Resistance θJA (WSON) 73°C/W
Soldering Information
See AN-1112 (SNVA009) "DSBGA Wafers Level Chip Scale Package."
(1) All voltages are measured with respect to the ground pin, unless otherwise specified.
(2) 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.
(3) The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX,θJA, and the ambient temperature
TA. The maximum allowable power dissipation is PDMAX = (TJMAX–TA)/θJA or the number given in Absolute Maximum Ratings, whichever
is lower. For the LM4670, TJMAX = 150°C. The typical θJA is 220°C/W for the DSBGA package and 64°C/W for the WSON package.
(4) Human body model, 100pF discharged through a 1.5kΩresistor.
(5) Machine Model, 220pF – 240pF discharged through all pins.
Operating Ratings(1) (2)
TMIN ≤TA≤TMAX −40°C ≤TA≤85°C
Temperature Range Supply Voltage(3) 2.4V ≤VDD ≤5.5V
(1) All voltages are measured with respect to the ground pin, unless otherwise specified.
(2) 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.
(3) The maximum operating voltage for the LM4670 in the SDA (WSON) package when driving 4Ωloads to greater than 10% THD+N is
5.0V.
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Electrical Characteristics(1)(2)
The following specifications apply for AV= 2V/V (RI= 150kΩ), RL= 15µH + 8Ω+ 15µH unless otherwise specified. Limits
apply for TA= 25°C. LM4670 Units
Symbol Parameter Conditions (Limits)
Typical(3) Limit(4)(5)
VI= 0V, AV= 2V/V,
|VOS| Differential Output Offset Voltage 25 mV (max)
VDD = 2.4V to 5.0V
VDD = 2.4V to 5.0V,
PSRRGSM GSM Power Supply Rejection Ratio 64 dB
Input Referred
VDD = 2.4V to 5.0V
VIC = VDD/2 to 0.5V,
CMRRGSM GSM Common Mode Rejection Ratio 80 dB
VIC = VDD/2 to VDD – 0.8V,
Input Referred
|IIH| Logic High Input Current VDD = 5.0V, VI= 5.8V 20 100 μA (max)
|IIL| Logic Low Input Current VDD = 5.0V, VI= –0.3V 1 5 μA (max)
VIN = 0V, No Load, VDD = 5.0V 7.0 10 mA (max)
IDD Quiescent Power Supply Current VIN = 0V, No Load, VDD = 3.6V 4.8 mA
VIN = 0V, No Load, VDD = 2.4V 3.8 5 mA (max)
VSHUTDOWN = 0V
ISD Shutdown Current(6) 0.01 1 μA (max)
VDD = 2.4V to 5.0V
VSDIH Shutdown voltage input high 1.0 1.4 V (min)
VSDIL Shutdown voltage input low 0.8 0.4 V (max)
ROSD Output Impedance VSHUTDOWN = 0.4V >100 kΩ
270kΩ/RIV/V (min)
AVGain 300kΩ/RI330kΩ/RIV/V (max)
Resistance from Shutdown Pin to
RSD 300 kΩ
GND RL= 15μH + 4Ω+ 15μH,
THD = 10% (max)
f = 1kHz, 22kHz BW
VDD = 5V 3.0 W
VDD = 3.6V 1.5 W
VDD = 2.5V 675 mW
POOutput Power(7)(8) RL= 15μH + 4Ω+ 15μH,
THD+N = 1% (max)
f = 1kHz, 22kHz BW
VDD = 5V, 2.3 W
VDD = 3.6V, 1.2 W
VDD = 2.5V, 550 mW
(1) All voltages are measured with respect to the ground pin, unless otherwise specified.
(2) 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.
(3) Typical specifications are specified at 25°C and represent the parametric norm.
(4) Tested limits are specified to Texas Instruments' AOQL (Average Outgoing Quality Level).
(5) Datasheet min/max specification limits are ensured by design, test, or statistical analysis.
(6) Shutdown current is measured in a normal room environment. Exposure to direct sunlight will increase ISD by a maximum of 2µA. The
Shutdown pin should be driven as close as possible to GND for minimal shutdown current. See Application Information under
SHUTDOWN FUNCTION for more information.
(7) Typical output power numbers are for the LM4670 in the ITL (DSBGA) package. In the WSON (SDA) package, the output power will be
lower due to higher resistance seen from the IC output pad to PCB trace. The difference increases with lower impedance loads.
(8) The maximum operating voltage for the LM4670 in the SDA (WSON) package when driving 4Ωloads to greater than 10% THD+N is
5.0V.
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Electrical Characteristics(1)(2) (continued)
The following specifications apply for AV= 2V/V (RI= 150kΩ), RL= 15µH + 8Ω+ 15µH unless otherwise specified. Limits
apply for TA= 25°C. LM4670 Units
Symbol Parameter Conditions (Limits)
Typical(3) Limit(4)(5)
RL= 15μH + 8Ω+ 15μH,
THD = 10% (max)
f = 1kHz, 22kHz BW
VDD = 5V 1.65 W
VDD = 3.6V 850 mW
VDD = 2.5V 400 mW
POOutput Power(7) RL= 15μH + 8Ω+ 15μH,
THD+N = 1% (max)
f = 1kHz, 22kHz BW
VDD = 5V, 1.35 W
VDD = 3.6V, 680 mW (min)
VDD = 2.5V, 325 600 mW
VDD = 5V, PO= 1WRMS,0.35 %
f = 1kHz
VDD = 3.6V, PO= 0.5WRMS,0.30 %
f = 1kHz
THD+N Total Harmonic Distortion + Noise VDD = 3.6V, PO= 0.5WRMS,0.30 %
f = 5kHz
VDD = 3.6V, PO= 0.5WRMS,0.30 %
f = 10kHz
VDD = 3.6V,
VRipple = 200mVPP Sine,
fRipple = 217Hz 68 dB
Inputs to AC GND, CI= 0.1μ,
Input Referred
VDD = 3.6V,
VRipple = 200mVPP Sine,
PSRR Power Supply Rejection Ratio fRipple = 1kHz 65 dB
Inputs to AC GND, CI= 0.1μF
Input Referred
VDD = 3.6V,
VRipple = 200mVPP Sine,
fRipple = 217Hz 62 dB
fIN = 1kHz, PO= 10mWRMS
Input Referred
SNR Signal to Noise Ratio VDD = 5V, PO= 1WRMS 93 dB
VDD = 3.6V, f = 20Hz – 20kHz
Inputs to AC GND, CI= 0.1μF 85 μVRMS
No Weighting, Input Referred
εOUT Output Noise VDD = 3.6V, Inputs to AC GND
CI= 0.1μF, A Weighted 65 μVRMS
Input Referred
VDD = 3.6V, VRipple = 1VPP Sine
CMRR Common Mode Rejection Ratio 80 dB
fRipple = 217Hz, Input Referred
TWU Wake-up Time VDD = 3.6V 1.35 ms
TSD Shutdown Time VDD = 3.6V 0.01 ms
External Components Description
See Figure 1
Components Functional Description
1. CSSupply bypass capacitor which provides power supply filtering. Refer to POWER SUPPLY BYPASSING for
information concerning proper placement and selection of the supply bypass capacitor.
2. RIGain setting resistor. Differential gain is set by the equation AV= 2 * 150kΩ/ Ri(V/V).
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Typical Performance Characteristics(1)
THD+N vs Frequency THD+N vs Frequency
VDD = 2.5V, RL= 15µH + 4Ω+ 15µH VDD = 3.6V, RL= 15µH + 4Ω+ 15µH
POUT = 375mW, 22kHz BW POUT = 750mW, 22kHz BW
Figure 4. Figure 5.
THD+N vs Frequency THD+N vs Frequency
VDD = 5V, RL= 15µH + 4Ω+ 15µH VDD = 2.5V, RL= 15µH + 8Ω+ 15µH
POUT = 1.5W, 22kHz BW POUT = 200mW, 22kHz BW
Figure 6. Figure 7.
THD+N vs Frequency THD+N vs Frequency
VDD = 3.6V, RL= 15µH + 8Ω+ 15µH VDD = 5V, RL= 15µH + 8Ω+ 15µH
POUT = 500mW, 22kHz BW POUT = 1W, 22kHz BW
Figure 8. Figure 9.
(1) The performance graphs were taken using the Audio Precision AUX-0025 Switching Amplifier Measurement Filter in series with the LC
filter on the board.
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Typical Performance Characteristics(1) (continued)
THD+N vs Output Power THD+N vs Output Power
RL= 15µH + 4Ω+ 15µH RL= 15µH + 8Ω+ 15µH
f = 1kHz, 22kHz BW f = 1kHz, 22kHz BW
Figure 10. Figure 11.
CMRR vs Frequency PSRR vs Frequency
VDD = 3.6V, RL= 15µH + 8Ω+ 15µH VDD = 3.6V, RL= 15µH + 8Ω+ 15µH
VCM = 1VP-P Sine Wave, 22kHz BW VCM = 200mVP-P Sine Wave, 22kHz BW
Figure 12. Figure 13.
Efficiency and Power Dissipation Efficiency and Power Dissipation
vs Output Power vs Output Power
RL= 15µH + 4Ω+ 15µH, f = 1kHz, THD < 2% RL= 15µH + 8Ω+ 15µH, f = 1kHz, THD < 1%
Figure 14. Figure 15.
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Typical Performance Characteristics(1) (continued)
Output Power vs Supply Voltage Output Power vs Supply Voltage
RL= 15µH + 4Ω+ 15µH, f = 1kHz, 22kHz BW RL= 15µH + 8Ω+ 15µH, f = 1kHz, 22kHz BW
Figure 16. Figure 17.
Supply Current (RMS) vs Output Power Supply Current (RMS) vs Output Power
RL= 15µH + 4Ω+ 15µH, f = 1kHz RL= 15µH + 8Ω+ 15µH, f = 1kHz
Figure 18. Figure 19.
Shutdown Threshold Shutdwon Threshold vs Supply Voltage
RL= 15µH + 8Ω+ 15µH RL= 15µH + 8Ω+ 15µH
Figure 20. Figure 21.
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Typical Performance Characteristics(1) (continued)
Supply Current vs Shutdown Voltage Supply Current vs Supply Voltage
RL= 15µH + 8Ω+ 15µH RL= 15µH + 8Ω+ 15µH
Figure 22. Figure 23.
Supply Current vs Supply Voltage Differential Gain vs Supply Voltage
RL= Different µH loads RL= 15µH + 8Ω+ 15µH, Ri= 150kΩ, f = 1kHz
Figure 24. Figure 25.
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APPLICATION INFORMATION
GENERAL AMPLIFIER FUNCTION
The output signals generated by the LM4670 consist of two, BTL connected, output signals that pulse
momentarily from near ground potential to VDD. The two outputs can pulse independently with the exception that
they both may never pulse simultaneously as this would result in zero volts across the BTL load. The minimum
width of each pulse is approximately 350ns. However, pulses on the same output can occur sequentially, in
which case they are concatenated and appear as a single wider pulse to achieve an effective 100% duty cycle.
This results in maximum audio output power for a given supply voltage and load impedance. The LM4670 can
achieve much higher efficiencies than class AB amplifiers while maintaining acceptable THD performance.
The short (350ns) drive pulses emitted at the LM4670 outputs means that good efficiency can be obtained with
minimal load inductance. The typical transducer load on an audio amplifier is quite reactive (inductive). For this
reason, the load can act as it's own filter, so to speak. This "filter-less" switching amplifier/transducer load
combination is much more attractive economically due to savings in board space and external component cost
by eliminating the need for a filter.
POWER DISSIPATION AND EFFICIENCY
In general terms, efficiency is considered to be the ratio of useful work output divided by the total energy required
to produce it with the difference being the power dissipated, typically, in the IC. The key here is “useful” work. For
audio systems, the energy delivered in the audible bands is considered useful including the distortion products of
the input signal. Sub-sonic (DC) and super-sonic components (>22kHz) are not useful. The difference between
the power flowing from the power supply and the audio band power being transduced is dissipated in the
LM4670 and in the transducer load. The amount of power dissipation in the LM4670 is very low. This is because
the ON resistance of the switches used to form the output waveforms is typically less than 0.25Ω. This leaves
only the transducer load as a potential "sink" for the small excess of input power over audio band output power.
The LM4670 dissipates only a fraction of the excess power requiring no additional PCB area or copper plane to
act as a heat sink.
DIFFERENTIAL AMPLIFIER EXPLANATION
As logic supply voltages continue to shrink, designers are increasingly turning to differential analog signal
handling to preserve signal to noise ratios with restricted voltage swing. The LM4670 is a fully differential
amplifier that features differential input and output stages. A differential amplifier amplifies the difference between
the two input signals. Traditional audio power amplifiers have typically offered only single-ended inputs resulting
in a 6dB reduction in signal to noise ratio relative to differential inputs. The LM4670 also offers the possibility of
DC input coupling which eliminates the two external AC coupling, DC blocking capacitors. The LM4670 can be
used, however, as a single ended input amplifier while still retaining it's fully differential benefits. In fact,
completely unrelated signals may be placed on the input pins. The LM4670 simply amplifies the difference
between the signals. A major benefit of a differential amplifier is the improved common mode rejection ratio
(CMRR) over single input amplifiers. The common-mode rejection characteristic of the differential amplifier
reduces sensitivity to ground offset related noise injection, especially important in high noise applications.
PCB LAYOUT CONSIDERATIONS
As output power increases, interconnect resistance (PCB traces and wires) between the amplifier, load and
power supply create a voltage drop. The voltage loss on the traces between the LM4670 and the load results is
lower output power and decreased efficiency. Higher trace resistance between the supply and the LM4670 has
the same effect as a poorly regulated supply, increase ripple on the supply line also reducing the peak output
power. The effects of residual trace resistance increases as output current increases due to higher output power,
decreased load impedance or both. To maintain the highest output voltage swing and corresponding peak output
power, the PCB traces that connect the output pins to the load and the supply pins to the power supply should
be as wide as possible to minimize trace resistance.
The use of power and ground planes will give the best THD+N performance. While reducing trace resistance, the
use of power planes also creates parasite capacitors that help to filter the power supply line.
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The rising and falling edges are necessarily short in relation to the minimum pulse width (350ns), having
approximately 16ns rise and fall times, typical, depending on parasitic output capacitance. The inductive nature
of the transducer load can also result in overshoot on one or both edges, clamped by the parasitic diodes to
GND and VDD in each case. From an EMI standpoint, this is an aggressive waveform that can radiate or conduct
to other components in the system and cause interference. It is essential to keep the power and output traces
short and well shielded if possible. Use of ground planes, beads, and micro-strip layout techniques are all useful
in preventing unwanted interference.
As the distance from the LM4670 and the speaker increase, the amount of EMI radiation will increase since the
output wires or traces acting as antenna become more efficient with length. What is acceptable EMI is highly
application specific. Ferrite chip inductors placed close to the LM4670 may be needed to reduce EMI radiation.
The value of the ferrite chip is very application specific.
POWER SUPPLY BYPASSING
As with any power amplifier, proper supply bypassing is critical for low noise performance and high power supply
rejection ratio (PSRR). The capacitor (CS) location should be as close as possible to the LM4670. Typical
applications employ a voltage regulator with a 10µF and a 0.1µF bypass capacitors that increase supply stability.
These capacitors do not eliminate the need for bypassing on the supply pin of the LM4670. A 1µF tantalum
capacitor is recommended.
SHUTDOWN FUNCTION
In order to reduce power consumption while not in use, the LM4670 contains shutdown circuitry that reduces
current draw to less than 0.01µA. The trigger point for shutdown is shown as a typical value in Electrical
Characteristics and in the Shutdown Hysteresis Voltage graphs found in Typical Performance Characteristics. It
is best to switch between ground and supply for minimum current usage while in the shutdown state. While the
LM4670 may be disabled with shutdown voltages in between ground and supply, the idle current will be greater
than the typical 0.01µA value. Increased THD may also be observed with voltages less than VDD on the
Shutdown pin when in PLAY mode.
The LM4670 has an internal resistor connected between GND and Shutdown pins. The purpose of this resistor is
to eliminate any unwanted state changes when the Shutdown pin is floating. The LM4670 will enter the shutdown
state when the Shutdown pin is left floating or if not floating, when the shutdown voltage has crossed the
threshold. To minimize the supply current while in the shutdown state, the Shutdown pin should be driven to
GND or left floating. If the Shutdown pin is not driven to GND, the amount of additional resistor current due to the
internal shutdown resistor can be found by Equation 1.
(VSD - GND) / 300kΩ(1)
With only a 0.5V difference, an additional 1.7µA of current will be drawn while in the shutdown state.
PROPER SELECTION OF EXTERNAL COMPONENTS
The gain of the LM4670 is set by the external resistors, Ri in Figure 1, The Gain is given by Equation 2. Best
THD+N performance is achieved with a gain of 2V/V (6dB).
AV= 2 * 150 kΩ/ Ri(V/V) (2)
It is recommended that resistors with 1% tolerance or better be used to set the gain of the LM4670. The Ri
resistors should be placed close to the input pins of the LM4670. Keeping the input traces close to each other
and of the same length in a high noise environment will aid in noise rejection due to the good CMRR of the
LM4670. Noise coupled onto input traces which are physically close to each other will be common mode and
easily rejected by the LM4670.
Input capacitors may be needed for some applications or when the source is single-ended (see Figure 27 and
Figure 29). Input capacitors are needed to block any DC voltage at the source so that the DC voltage seen
between the input terminals of the LM4670 is 0V. Input capacitors create a high-pass filter with the input
resistors, Ri. The –3dB point of the high-pass filter is found using Equation 3.
fC= 1 / (2πRiCi) (Hz) (3)
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The input capacitors may also be used to remove low audio frequencies. Small speakers cannot reproduce low
bass frequencies so filtering may be desired . When the LM4670 is using a single-ended source, power supply
noise on the ground is seen as an input signal by the +IN input pin that is capacitor coupled to ground (see
Figure 29 to Figure 31). Setting the high-pass filter point above the power supply noise frequencies, 217Hz in a
GSM phone, for example, will filter out this noise so it is not amplified and heard on the output. Capacitors with a
tolerance of 10% or better are recommended for impedance matching.
DIFFERENTIAL CIRCUIT CONFIGURATIONS
The LM4670 can be used in many different circuit configurations. The simplest and best performing is the DC
coupled, differential input configuration shown in Figure 26.Equation 2 above is used to determine the value of
the Riresistors for a desired gain.
Input capacitors can be used in a differential configuration as shown in Figure 27.Equation 3 above is used to
determine the value of the Cicapacitors for a desired frequency response due to the high-pass filter created by
Ciand Ri.Equation 2 above is used to determine the value of the Riresistors for a desired gain
The LM4670 can be used to amplify more than one audio source. Figure 28 shows a dual differential input
configuration. The gain for each input can be independently set for maximum design flexibility using the Ri
resistors for each input and Equation 2. Input capacitors can be used with one or more sources as well to have
different frequency responses depending on the source or if a DC voltage needs to be blocked from a source.
SINGLE-ENDED CIRCUIT CONFIGURATIONS
The LM4670 can also be used with single-ended sources but input capacitors will be needed to block any DC at
the input terminals. Figure 29 shows the typical single-ended application configuration. The equations for Gain,
Equation 2, and frequency response, Equation 3, hold for the single-ended configuration as shown in Figure 29.
When using more than one single-ended source as shown in Figure 30, the impedance seen from each input
terminal should be equal. To find the correct values for Ci3 and Ri3 connected to the +IN input pin the equivalent
impedance of all the single-ended sources are calculated. The single-ended sources are in parallel to each other.
The equivalent capacitor and resistor, Ci3 and Ri3, are found by calculating the parallel combination of all
Civalues and then all Rivalues. Equation 4 and Equation 5 below are for any number of single-ended sources.
Ci3 = Ci1 + Ci2 + Cin ... (F) (4)
Ri3 = 1 / (1/Ri1 + 1/Ri2 + 1/Rin ...) (Ω) (5)
The LM4670 may also use a combination of single-ended and differential sources. A typical application with one
single-ended source and one differential source is shown in Figure 31. Using the principle of superposition, the
external component values can be determined with the above equations corresponding to the configuration.
Figure 26. Differential input configuration
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Figure 27. Differential input configuration with input capacitors
Figure 28. Dual differential input configuration
Figure 29. Single-ended input configuration
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REFERENCE DESIGN BOARD SCHEMATIC
Figure 32. Reference Design Board Schematic
In addition to the minimal parts required for the application circuit, a measurement filter is provided on the
evaluation circuit board so that conventional audio measurements can be conveniently made without additional
equipment. This is a balanced input, grounded differential output low pass filter with a 3dB frequency of
approximately 35kHz and an on board termination resistor of 300Ω(see Figure 32). Note that the capacitive load
elements are returned to ground. This is not optimal for common mode rejection purposes, but due to the
independent pulse format at each output there is a significant amount of high frequency common mode
component on the outputs. The grounded capacitive filter elements attenuate this component at the board to
reduce the high frequency CMRR requirement placed on the analysis instruments.
Even with the grounded filter the audio signal is still differential, necessitating a differential input on any analysis
instrument connected to it. Most lab instruments that feature BNC connectors on their inputs are NOT differential
responding because the ring of the BNC is usually grounded.
The commonly used Audio Precision analyzer is differential, but its ability to accurately reject fast pulses of
350ns width is questionable necessitating the on board measurement filter. When in doubt or when the signal
needs to be single-ended, use an audio signal transformer to convert the differential output to a single ended
output. Depending on the audio transformer's characteristics, there may be some attenuation of the audio signal
which needs to be taken into account for correct measurement of performance.
Measurements made at the output of the measurement filter suffer attenuation relative to the primary, unfiltered
outputs even at audio frequencies. This is due to the resistance of the inductors interacting with the termination
resistor (300Ω) and is typically about -0.25dB (3%). In other words, the voltage levels (and corresponding power
levels) indicated through the measurement filter are slightly lower than those that actually occur at the load
placed on the unfiltered outputs. This small loss in the filter for measurement gives a lower output power reading
than what is really occurring on the unfiltered outputs and its load.
Copyright © 2004–2013, Texas Instruments Incorporated Submit Documentation Feedback 15
Product Folder Links: LM4670
LM4670
SNAS240C –DECEMBER 2004–REVISED MAY 2013
www.ti.com
LM4670 DSBGA BOARD ARTWORK
Figure 33. Composite View Figure 34. Silk Screen
Figure 35. Top Layer Figure 36. Internal Layer 1, GND
Figure 37. Internal Layer 2, VDD Figure 38. Bottom Layer
16 Submit Documentation Feedback Copyright © 2004–2013, Texas Instruments Incorporated
Product Folder Links: LM4670
LM4670
www.ti.com
SNAS240C –DECEMBER 2004–REVISED MAY 2013
LM4670 WSON BOARD ARTWORK
Figure 39. Composite View Figure 40. Silk Screen
Figure 41. Top Layer Figure 42. Internal Layer 1, GND
Figure 43. Internal Layer 2, VDD Figure 44. Bottom Layer
Revision History
Rev Date Description
1.0 12/15/04 Initial WEB of the D/S (TL pkg).
1.1 7/06/05 Re-released D/S to the WEB (added the SD
package).
1.2 7/13/06 Edited Note 9, then re-released D/S to the
WEB.
C 5/02/13 Changed layout of National Data Sheet to TI
format
Copyright © 2004–2013, Texas Instruments Incorporated Submit Documentation Feedback 17
Product Folder Links: LM4670
PACKAGE OPTION ADDENDUM
www.ti.com 26-Aug-2013
Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status
(1)
Package Type Package
Drawing Pins Package
Qty Eco Plan
(2)
Lead/Ball Finish MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
LM4670ITL/NOPB ACTIVE DSBGA YZR 9 250 Green (RoHS
& no Sb/Br) SNAGCU Level-1-260C-UNLIM -40 to 85 G
E6
LM4670ITLX/NOPB ACTIVE DSBGA YZR 9 3000 Green (RoHS
& no Sb/Br) SNAGCU Level-1-260C-UNLIM -40 to 85 G
E6
LM4670SD/NOPB ACTIVE WSON NGQ 8 1000 Green (RoHS
& no Sb/Br) Call TI Level-1-260C-UNLIM -40 to 85 L4670
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
PACKAGE OPTION ADDENDUM
www.ti.com 26-Aug-2013
Addendum-Page 2
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
LM4670ITL/NOPB DSBGA YZR 9 250 178.0 8.4 1.57 1.57 0.76 4.0 8.0 Q1
LM4670ITLX/NOPB DSBGA YZR 9 3000 178.0 8.4 1.57 1.57 0.76 4.0 8.0 Q1
LM4670SD/NOPB WSON NGQ 8 1000 178.0 12.4 3.3 3.3 1.0 8.0 12.0 Q1
PACKAGE MATERIALS INFORMATION
www.ti.com 12-Aug-2013
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
LM4670ITL/NOPB DSBGA YZR 9 250 210.0 185.0 35.0
LM4670ITLX/NOPB DSBGA YZR 9 3000 210.0 185.0 35.0
LM4670SD/NOPB WSON NGQ 8 1000 210.0 185.0 35.0
PACKAGE MATERIALS INFORMATION
www.ti.com 12-Aug-2013
Pack Materials-Page 2
MECHANICAL DATA
NGQ0008A
www.ti.com
SDA08A (Rev A)
MECHANICAL DATA
YZR0009xxx
www.ti.com
TLA09XXX (Rev C)
0.600±0.075 D
E
A
. All linear dimensions are in millimeters. Dimensioning and tolerancing per ASME Y14.5M-1994.
B. This drawing is subject to change without notice.
4215046/A 12/12
NOTES:
D: Max =
E: Max =
1.514 mm, Min =
1.489 mm, Min =
1.454 mm
1.428 mm
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