Eutech EUA6019 3-w stereo audio power amplifier with advanced dc volume control Datasheet

EUA6019
3-W Stereo Audio Power Amplifier
with Advanced DC Volume Control
DESCRIPTOIN
FEATURES
The EUA6019 is a stereo audio power amplifier that drives 3
W/channel of continuous RMS power into a 3-Ω load.
Advanced dc volume control minimizes external components
and allows BTL (speaker) volume control and SE (headphone)
volume control. Notebook and pocket PCs benefit from the
integrated feature set that minimizes external components
without sacrificing functionality.
To simplify design, the speaker volume level is adjusted by
applying a dc voltage to the VOLUME terminal. Likewise, the
delta between speaker volume and headphone volume can be
adjusted by applying a dc voltage to the SEDIFF terminal. To
avoid an unexpected high volume level through the
headphones, a third terminal, SEMAX, limits the headphone
volume level when a dc voltage is applied. Finally, to ensure a
smooth transition between active and shutdown modes, a fade
mode ramps the volume up and down.
z
z
z
z
z
APPLICATIONS
z
z
z
DS6019 Ver 1.1 May. 2007
1
Advanced DC Volume Control With 2-dB Steps
From -40 dB to 20 dB
-Fade Mode
-Maximum Volume Setting for SE Mode
-Adjustable SE Volume Control
Referenced to BTL Volume control
3 W into 3-Ω Speakers
Stereo Input MUX
Differential Inputs
RoHS Compliant and 100% Lead (Pb)-Free
Notebook PC
LCD Monitors
Pocket PC
EUA6019
Block Diagram
DS6019 Ver 1.1 May. 2007
2
EUA6019
Typical Application Circuit
Figure 1. Application circuit using single-ended inputs and input MUX
Figure 2. Application circuit using differential inputs
DS6019 Ver 1.1 May. 2007
3
EUA6019
Pin Configurations
Package Type
Pin Configurations(Top View)
TSSOP-24
Pin Description
PIN
PIN
I/O
DESCRIPTION
PGND
LOUTPVDD
LHPIN
1,13
12
3,11
10
O
I
LLINEIN
9
I
LIN
8
I
VDD
7
-
RIN
6
I
RLINEIN
5
I
Power ground
Left channel negative audio output
Supply voltage terminal for power stage
Left channel headphone input, selected when HP/ LINE is held high
Left channel line input, selected when HP/ LINE is held low
Common left channel input for fully differential input. AC ground for single-ended
inputs.
Supply voltage terminal
Common right channel input for fully differential input. AC ground for single-ended
inputs.
Right channel line input, selected when HP/ LINE is held low
RHPIN
ROUTROUT+
SHUTDOWN
4
2
24
I
O
O
Right channel headphone input, selected when HP/ LINE is held high
Right channel negative audio output
Right channel positive audio output
15
I
Places the amplifier in shutdown mode if a TTL logic low is placed on this terminal
FADE
16
I
BYPASS
AGND
SEMAX
17
18
19
I
I
SEDIFF
20
I
VOLUME
21
I
HP/ LINE
22
I
SE/ BTL
23
I
LOUT+
14
O
DS6019 Ver 1.1 May. 2007
Places the amplifier in fade mode if a logic low is placed on this terminal; normal
operation if a logic high is placed on this terminal
Tap to voltage divider for internal midsupply bias generator used for analog reference
Analog power supply ground
Sets the maximum volume for single ended operation. DC voltage range is 0 to VDD.
Sets the difference between BTL volume and SE volume. DC voltage range is 0 to
VDD.
Terminal for dc volume control. DC voltage range is 0 to VDD.
Input MUX control. When logic high, RHPIN and LHPIN inputs are selected .When
logic low, RLINEIN and LLINEIN inputs are selected.
Output MUX control. When this terminal is high, SE outputs are selected. When this
terminal is low, BTL outputs are selected.
Left channel positive audio output.
4
EUA6019
Ordering Information
Order Number
Package Type
EUA6019QIR1
TSSOP 24
xxxxx
A6019A
-40 °C to 85°C
EUA6019QIT1
TSSOP 24
xxxxx
A6019A
-40 °C to 85°C
EUA6019
Marking
□ □ □ □
Lead Free Code
1: Lead Free 0: Lead
Packing
R: Tape& Reel
T: Tube
Operating temperature range
I: Industry Standard
Package Type
Q: TSSOP
DS6019 Ver 1.1 May. 2007
5
Operating Temperature range
EUA6019
Absolute Maximum Ratings
„
„
„
„
„
„
„
„
Supply voltage, VDD------------------------------------------------------------------------------------------------ 6V
Input voltage, VI------------------------------------------------------------------------------ –0.3 V to VDD +0.3 V
Continuous total power dissipation---------------------------- internally limited (see Dissipation Rating Table)
Operating free-air temperature range, TA--------------------------------------------------------- –40°C to 85° C
Operating junction temperature range, TJ ------------------------------------------------------ - –40°C to 150°C
Storage temperature range, Tstg------------------------------------------------------------------ -- –65°C to 150°C
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds----------------------------------------- 260°C
Thermal Resistance θJA (TSSOP) ------------------------------------------------------------------------ 87.9°C/W
Recommended Operating Conditions
Supply voltage, VDD
High-level input voltage, VIH
Low-level input voltage, VIL
Min
Max
Unit
4
5.5
V
SE/ BTL , HP/ LINE , FADE
VDD × 0.8
SHUTDOWN
2
V
SE/ BTL , HP/ LINE , FADE
VDD × 0.6
SHUTDOWN
0.8
Operating free-air temperature, TA
-40
V
85
°C
Electrical Characteristics at Specified Free-air Temperature, VDD = PVDD=5.5V, TA = 25°C
Symbol
Parameter
VOO
Output offset voltage
(measured differentially)
PSRR
Power supply rejection ratio
IIH
High-level input current
( SE/ BTL , SHUTDOWN ,
FADE , HP/ LINE ,SEMAX,
VOLUME,SEDIFF)
IIL
Low-level input current
IDD
Supply current, no load
IDD
Supply current, max power into a
3-Ω load
IDD(SD)
Supply current, shutdown mode
DS6019 Ver 1.1 May. 2007
Conditions
EUA6019
Min.
Typ. Max.
Unit
VDD= 5.5V,Gain=0 dB, SE/ BTL =0V
30
mV
VDD= 5.5V,Gain=20 dB, SE/ BTL =0V
50
mV
VDD= PVDD= 4 V to 5.5 V
-40
-68
dB
VDD= PVDD=5.5V, VI = VDD =PVDD
1
µA
VDD= PVDD=5.5V, VI = 0V
1
µA
VDD= PVDD=5.5V, SE/ BTL =0V,
SHUTDOWN =2V
VDD= PVDD=5.5V, SE/ BTL =5.5V
SHUTDOWN =2V
VDD= PVDD=5.5V, SE/ BTL =0V,
SHUTDOWN =2V,RL=3Ω,
Po=2 W, stereo
SHUTDOWN =0V
6
7.3
mA
4.4
1.5
1
ARMS
20
µA
EUA6019
Operating Characteristics, VDD =PVDD= 5V, TA = 25°C, RL = 3Ω, Gain =6 dB
Symbol
Parameter
PO
Output power
THD+N
Total harmonic distortion plus
noise
VOH
VOL
V(Bypass)
BOM
EUA6019
Min.
Typ.
THD=1%, f=1kHz
2
THD=10%, f=1kHz,VDD=5.5V
3
PO=1W, RL=8Ω,f=1 kHz
RL =8Ω,Measured between output
and VDD
RL =8Ω,Measured between output
Low-level output voltage
and GND
Measured at pin 17,No load,
Bypass voltage (Nominally VDD/2)
VDD=5.5V
Maximum output power
THD=5%
bandwidth
Noise output voltage
f =1kHz,Gain=0 dB
C(BYP)=0.47µF
f=20 Hz to 20 kHz,
Gain=0 dB,
C(BYP)=0.47µF,
Input impedance (see Figure 25) VOLUME=5 V
DS6019 Ver 1.1 May. 2007
7
Max.
Unit
W
<0.4%
High-level output voltage
Supply ripple rejection ratio
ZI
Conditions
2.65
2.75
700
mV
400
mV
2.85
V
＞20
kHz
BTL mode
-63
dB
SE mode
-57
dB
BTL mode
36
µVRMS
14
kΩ
EUA6019
DS6019 Ver 1.1 May. 2007
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
8
EUA6019
Figure 9
Figure 10
Figure 11
Figure 12
Figure 13
DS6019 Ver 1.1 May. 2007
Figure 14
9
EUA6019
DS6019 Ver 1.1 May. 2007
Figure 15
Figure 16
Figure 17
Figure 18
Figure 19
Figure 20
10
EUA6019
Figure 21
Figure 22
Figure 23
Figure 24
Figure 25
DS6019 Ver 1.1 May. 2007
11
EUA6019
Application Information
Table 1. DC Volume Control (BTL Mode, VDD=5V)(1)
VOLUME(PIN21)
From(V)
To(V)
Gain of amplifier (dB)
0.00
0.26
-85(2)
0.33
0.37
-40
0.44
0.48
-38
0.56
0.59
36
0.67
0.70
-34
0.78
0.82
-32
0.89
0.93
-30
1.01
1.04
-28
1.12
1.16
-26
1.23
1.27
-24
1.35
1.38
-22
1.46
1.49
-20
1.57
1.60
-18
1.68
1.72
-16
1.79
1.83
-14
1.91
1.94
-12
2.02
2.06
-10
2.13
2.17
-8
2.25
2.28
-6(2)
2.36
2.39
-4
2.47
2.50
-2
2.58
2.61
0
2.70
2.73
2
2.81
2.83
4
2.92
2.95
6
3.04
3.06
8
3.15
3.17
10
3.26
3.29
12
3.38
3.40
14
3.49
3.51
16
3.60
3.63
18
3.71
5.00
20(2)
(1)For other values of VDD ,scale the voltage values in the table by a factor of VDD/5.
(2)Tested in production. Remaining gain steps are specified by design.
DS6019 Ver 1.1 May. 2007
12
EUA6019
Table 2. DC Volume Control (SE Mode, VDD=5V)
(1)
VOLUME=VOLUME-SEDIFF or SEMAX
From(V)
To(V)
Gain of amplifier (dB)
0.00
0.26
-85(2)
0.33
0.37
-46
0.44
0.48
-44
0.56
0.59
-42
0.67
0.70
-40
0.78
0.82
-38
0.89
0.93
-36
1.01
1.04
-34
1.12
1.16
-32
1.23
1.27
-30
1.35
1.38
-28
1.46
1.49
-26
1.57
1.60
-24
1.68
1.72
-22
1.79
1.83
-20
1.91
1.94
-18
2.02
2.06
-16
2.13
2.17
-14
2.25
2.28
-12
2.36
2.39
-10
2.47
2.50
-8
2.58
2.61
-6(2)
2.70
2.73
-4
2.81
2.83
-2
2.92
2.95
0(2)
3.04
3.06
2
3.15
3.17
4
3.26
3.29
6(2)
3.38
3.40
8
3.49
3.51
10
3.60
3.63
12
3.71
5.00
14
(1)For other values of VDD ,scale the voltage values in the table by a factor of VDD/5.
(2)Tested in production. Remaining gain steps are specified by design.
DS6019 Ver 1.1 May. 2007
13
EUA6019
gain step depending on the direction the voltage is
changing .If using a DAC to control the volume, set the
voltage in the middle of each range to ensure that the
desired gain is achieved.
A pictorial representation of the volume control can be
found in Figure 27.The graph focuses on three gain steps
with the trip points defined in Table 1 for BTL gain. The
dotted line represents the hysteresis about each gain step.
VOLUME,SEDIFF, and SEMAX Operation
Three pins labeled VOLUME, SEDIFF, and SEMAX
control the BTL volume when driving speakers and the SE
volume when driving headphones. All of these pins are
controlled with a dc voltage, which should not exceed VDD.
When driving speakers in BTL mode, the VOLUME pin is
the only pin that controls the gain. Table 1 shows the gain
for the BTL mode. The voltages listed in the table are for
VDD =5V. For a different VDD, the values in the table scale
linearly. If VDD=4V , multiply all the voltages in the table by
4 V/5V, or 0.8.
The EUA6019 allows the user to specify a difference
between BTL gain and SE gain. This is desirable to avoid
any listening discomfort when plugging in headphones.
When switching to SE mode, the SEDIFF and SEMAX pins
control the singe-ended gain proportional to the gain set by
the voltage on the VOLUME pin,. When SEDIFF =0V, the
difference between the BTL gain and the SE gain is 6dB.
Refer to the section labeled bridged-tied load versus
single-ended load for an explanation on why the gain in
BTL mode is 2x that of single-ended mode, or 6DB greater.
As the voltage on the SEDIFF terminal is increased, the
gain in SE mode decreases. The voltage on the SEDIFF
terminal is subtracted from the voltage on the VOLUME
terminal and this value is used to determine the SE gain.
Some audio systems require that the gain be limited in the
single-ended mode to a level that is comfortable for
headphone listening. Most volume control devices only
have one terminal for setting the gain. For example, if the
speaker gain is 20dB , the gain in the headphone channel is
fixed at 14dB. This level of gain could cause discomfort to
listeners and the SEMAX pin allows the designer to limit
this discomfort when plugging in headphones. The SEMAX
terminal controls the maximum gain for single-ended mode.
The functionality of the SEDIFF and SEMAX pin are
combined to set the SE gain. A block diagram of the
combined functionality is shown in Figure 26. The value
obtained from the block diagram for SE_VOLUME is a dc
voltage that can be used in conjunction with Table 2 to
determine the SE gain. Again, the voltages listed in the
table are for VDD =5V. The values must be scaled for other
values of VDD.
Table 1 and Table 2 show a range of voltages for each gain
step . There is a gap in the voltage between each gain step .
This gap represents the hysteresis about each trip point in
the internal comparator. The hysteresis ensures that the gain
control is monotonic and does not oscillate form one gain
step to another . If a potentiometer is used to adjust the
voltage on the control terminals, the gain increases as the
potentiometer is turned in one direction and decreases as it
is turned back the other direction. The trip point, where the
gain actually changes , is different depending on whether
the voltage is increased or decreased as a result of the
hysteresis about each trip point. The gaps in Table 1 and
Table 2 can also be through of as indeterminate states where
the gain could be in the next higher gain step or the lower
DS6019 Ver 1.1 May. 2007
Figure 26. Block diagram of SE Volume Control
Figure 27. DC Volume Control Operation
14
EUA6019
HP/LINE Operation
The HP/LINE input controls the internal input
multiplexer (MUX).Refer to the block diagram in Figure
30.This allows the device to switch between two separate
stereo inputs to the amplifier. For design flexibility, the
HP/LINE control is independent of the output mode, SE
or BTL, which is controlled by the aforementioned
SE/ BTL pin. To allow the amplifier to switch from the
LINE inputs to the HP inputs when the output switches
from BTL mode to SE mode, simply connect the
SE/ BTL control input to the HP/LINE input.
When this input is logic high, the RHPIN and LHPIN
inputs are selected .when this terminal is logic low, the
RLINEIN and LLINEIN inputs are selected. This operation
is also detailed in Table 4 and the trip levels for a logic low
(VIL) or logic high (VIH) can be found in the recommended
operation conditions table.
Shutdown Modes
The EUA6019 employs a shutdown mode of operation
designed to reduce supply current, IDD, to the absolute
minimum level during periods of nonuse for
battery-power conservation. The SHUTDOWN input
terminal should be held high during normal operation
when the amplifier is in use. Pulling SHUTDOWN low
causes the outputs to mute and the amplifier to enter a
low-current state, IDD<1µA. SHUTDOWN should never
be left unconnected because amplifier operation would be
unpredictable.
Table 3 . HP/LINE , SE/ BTL , and Shutdown Function
Inputs
HP/ LINE
X
Low
Low
High
High
SE/ BTL SHUTDOWN
X
Low
High
Low
High
Low
High
High
High
High
Amplifier State
INPUT OUTPUT
X
Line
Line
HP
HP
Mute
BTL
SE
BTL
SE
X= Do not care
DS6019 Ver 1.1 May. 2007
15
FADE Operation
For design flexibility, a fade mode is provided to slowly
ramp up the amplifier gain when coming out of shutdown
mode and conversely ramp the gain down when going into
shutdown. This mode provides a smooth transition
between the active and shutdown states and virtually
eliminates any pops or clicks on the outputs.
When the FADE input is a logic low, the device is placed
into fade-on mode. A logic high on this pin places the
amplifier in the fade-off mode. The voltage trip levels for
a logic low (VIL) or logic high (VIH) can be found in the
recommended operating conditions table.
When a logic low is applied to the FADE pin and a logic
low is then applied on the SHUTDOWN pin, the channel
gain steps down from gain step to gain step at a rate of
two clock cycles per step. With a nominal internal clock
frequency of 58HZ,this equates to 34 ms (1/24 Hz) per
step. The gain steps down until the lowest gain step is
reached .The time it takes to reach this step depends on the
gain setting prior to placing the device in shutdown. For
example, if the amplifier is in the highest gain mode of
20dB, the time it takes to ramp down the channel gain is
1.05 seconds. This number is calculated by taking the
number of steps to reach the lowest gain from the highest
gain, or 31 steps, and multiplying by the time per step, or
34 ms.
After the channel gain is stepped down to the lowest gain,
the amplifier begins discharging the bypass capacitor from
the nominal voltage of VDD/2 to ground.
This time is dependent on the value of the bypass
capacitor. For a 0.47-µF capacitor that is used in the
application diagram in Figure 1, the time is approximately
500ms. This time scales linearly with the value of bypass
capacitor. For example, if a 1-µF capacitor is used for
bypass, the time period to discharge the capacitor to
ground is twice that of the 0.47-µF capacitor, or 1 second.
Figure 30 below is a waveform captured at the output
during the shutdown sequence when the part is in fade-on
mode. The gain is set to the highest level and the output is
at VDD when the amplifier is shut down.
When a logic high is placed on the SHUTDOWN pin
and the FADE pin is still held low, the device begins the
start-up process, the bypass capacitor will begin charging.
Once the bypass voltage reaches the final value of VDD/2,
the gain increases in2-dB steps from the lowest gain level
to the gain level set by the dc voltage applied to the
VOLUME, SEDIFF, and SEMAX pins.
In the fade-off mode, the amplifier stores the gain value
prior the staring the shutdown sequence. The output of the
amplifier immediately drops to VDD/2 and the bypass
capacitor begins a smooth discharge to ground when
shutdown is released, the bypass capacitor charges up to
VDD/2 and the channel gain returns immediately to the
value stored in memory. Figure 31 below is a waveform
captured at the output during the shutdown sequence when
EUA6019
the part is in the fade-off mode. The gain is set to the
highest level, and the output is at VDD when the amplifier
is shut down.
The power-up sequence is different from the shutdown
sequence and the voltage on the pin does not change the
power-up sequence. Upon a power-up condition, the
EUA6019 begins in the lowest gain setting and steps
up 2 dB every 2 clock cycles until the final value is
reached as determined by the dc voltage applied to the
VOLUME, SEDIFF , and SEMAX pins.
is due to the high pass filter network created with the
speaker impedance and the coupling capacitance and is
calculated with equation 2.
fC =
V(rms) = VO(PP)
Power =
2 2
V(rms)
----------------------------------(2)
Figure 29. Single-Ended configuration and
Frequency Response
Increasing power to the load does carry a penalty of
increased internal power dissipation. The increased
dissipation is understandable considering that the BTL
configuration produces 4 × the output power of the SE
configuration. Internal dissipation versus output power is
discussed further in the crest factor and thermal
considerations section.
------(1)
RL
Single-Ended Operation
In SE mode the load is driven from the primary amplifier
output for each channel (OUT+, terminals 21 and 4 ). The
amplifier switches single-ended operation when the
SE/ BTL terminal is held high. This puts the negative
outputs in a high-impedance state, and reduces the
amplifier’s gain to 1V/V.
Figure 28.Bridge-Tied Load configuration
Input MUX Operation
The input MUX allows two separate inputs to be applied
to the amplifier. This allow the designer to choose which
input is active independent of the state of the
SE/ BTL terminal. When the HP/LINE terminal is held
high, the headphone inputs are active. When the
HP/LINE terminal is held low, the line BTL inputs are
active.
In a typical computer sound channel operating at 5V,
bridging raises the power into an 8-Ω speaker from a
singled-ended (SE, ground reference) limit of 250 mW to
1W. In sound power that is a 6-dB improvement, which is
loudness that can be heard. In addition to increased power
there are frequency response concerns. Consider the
single-supply SE configuration shown in Figure 29.
A coupling capacitor is required to block the dc offset
voltage from reaching the load. These capacitors can be
quite large (approximately 33µF to 1000µF) so they tend
to be expensive, heavy, occupy valuable PCB area, and
have the additional drawback of limiting low-frequency
performance of the system. This frequency limiting effect
DS6019 Ver 1.1 May. 2007
2 π R LCC
For example, a 68µF capacitor with an 8-Ω speaker would
attenuate low frequencies below 293 Hz. The BTL
configuration cancels the dc offsets, which eliminates the
need for the blocking capacitors. Low-frequency
performance is then limited only by the input network and
speaker response. Cost and PCB space are also minimized
by eliminating the bulky coupling capacitor.
Bridged-Tied Load Versus Single-Ended Mode
Figure 28 show a Class-AB audio power amplifier (APA)
in a BTL configuration. The EUA6019 BTL amplifier
consists of two Class-AB amplifiers driving both ends of
the load. There are several potential benefits to this
differential drive configuration, but initially consider
power to the load. The differential drive to the speaker
means that as one side is slewing up, the other side is
slewing down, and vice versa. This in effect doubles the
voltage swing on the load as compared to a ground
referenced load. Plugging 2×VO(PP) into the power
equation, where voltage is squared, yields 4× the output
power from the same supply rail and load impedance(see
equation 1)
2
1
16
EUA6019
SE/BTL Operation
The ability of the EUA6019 to easily switch between BTL
and SE modes is one of its most important cost saving
features. This feature eliminates the requirement for an
additional headphone amplifier in applications where
internal stereo speakers are driven in BTL mode but
external headphone or speakers must be accommodated.
Internal to the EUA6019 , two separate amplifiers drive
OUT+ and OUT- .The SE/ BTL input (terminal 15)
control the operation of the follower amplifier that drives
LOUT- and ROUT- (terminals 9 and 16).When
SE/ BTL is held low, the amplifier is on and the EUA6019
is in the BTL mode. When SE/ BTL is held high, the
OUT- amplifiers are in a high output impedance state,
which configures the EUA6019 as an SE driver from
LOUT+ and ROUT+ (terminals 4 and 21). IDD is reduced
by approximately one-half in SE mode. Control of the
SE/ BTL input can be from a logic-level CMOS source or,
more typically, from a resistor divider network as shown
in Figure 30.
Input Resistance
Each gain setting is achieved by varying the input
resistance of the amplifier, which can range from its
smallest value to over 6 times that value. As a results, if a
single capacitor is used in the input high-pass filter, the –3
dB or cut-off frequency will also change by over 6 times.
Figure 31. Input Resistor
The-3dB frequency can be calculated using equation
3:
1
f-3dB =
2 π C (R || R i )
-------------- (3)
If the filter must be more accurate, the value of the
capacitor should be increased while the value of the resistor
to ground should be decreased. In addition, the order of the
filter could be increased.
Input Capacitor, Ci
In the typical application an input capacitor, Ci, is required
to allow the amplifier to bias the input signal to the proper
dc level for optimum operation. In this case, Ci and the input
impedance of the amplifier, Zi, from a high-pass filter with
the corner frequency determined in equation 4.
Figure 30. Resistor divider Network circuit 2
fc(highpass)=
Using a readily available 1/8-in. (3.5mm) stereo headphone
jack, the control switch is closed when no plug is inserted.
When closed the 100-kΩ /1-kΩ divider pulls the
SE/ BTL input low. When a plug is inserted, the 1-kΩ
resistor is disconnected and the SE/ BTL input is pulled
high. When the input goes high, the OUT- amplifier is shut
down causing the speaker to mute(virtually open-circuits
the speaker).The OUT+ amplifier then drives through the
output capacitor (CO) into the headphone jack.
1
-----------------(4)
2 π Zi Ci
The value of Ci is important to consider as it directly affects
the bass (low frequency) performance of the circuit.
Consider the example where Zi is 70kΩ and the
specification calls for a flat bass response down to 40Hz.
Equation 2 is reconfigured as equation 5.
Ci =
1
----------------------------(5 )
2 π Z fC
i
DS6019 Ver 1.1 May. 2007
17
EUA6019
Output Coupling Capacitor, (CC)
For general signal-supply SE configuration, the output
coupling capacitor (CC) is required to block the dc bias at
the output of the amplifier thus preventing dc currents in
the load. As with the input coupling capacitor, the output
coupling capacitor and impedance of the load form a
high-pass filter governed by equation 6.
In this example, Ci is 56nF so one would likely choose a
value in the range of 56nF to 1µF. A further consideration
for this capacitor is the leakage path from the input source
through the input network (Ci) and the feedback network
to the load. This leakage current creates a dc offset voltage
at the input to the amplifier that reduces useful headroom,
especially in high gain applications. For this reason, a
low- leakage tantalum or ceramic capacitor is the best
choice. When polarized capacitors are used, the positive
side of the capacitor should face the amplifier input in
most applications as the dc level there is held at VDD/2,
which is likely higher than the source dc level. Note that it
is important to confirm the capacitor polarity in the
application.
fc(high)=
Decoupling Capacitor, (CS)
The EUA6019 is a high-performance CMOS audio
amplifier that requires adequate power supply decoupling
to ensure the output total harmonic distortion (THD) is as
low as possible. Power supply decoupling also prevents
oscillations for long lead lengths between
the amplifier and the speaker. The optimum decoupling is
achieved by using two capacitors of different types that
target different types of noise on the power supply leads.
For higher frequency transients, spikes, or digital hash on
the line, a good low equivalent-series-resistance (ESR)
ceramic capacitor, typically 0.1µF placed as close as
possible to the device VDD lead, works best. For filtering
lower-frequency noise signals, a larger aluminum
electrolytic capacitor of 10µF or greater placed near the
audio power amplifier is recommended.
2π R C
L C
-------------------(6)
The main disadvantage, from a performance standpoint, is
the load impedances are typically small, which drives the
low-frequency corner higher, degrading the bass response.
Large values of CC are required to pass low frequencies
into the load. Consider the example where a
CC of 330µF is chosen and loads vary from 3Ω, 4Ω, 8Ω,
32Ω, 10kΩ, to 47kΩ. Table 3 summarizes the frequency
response characteristics of each configuration.
Bypass Capacitor, (CB)
The bypass capacitor, CB, is the most critical capacitor and
serves several important functions. During start-up or
recovery from shutdown mode, CB determines the rate at
which the amplifier starts up. The second function is to
reduce noise produced by the power supply caused by
coupling into the output drive signal. This noise is from the
midrail generation circuit internal to the amplifier, which
appears as degraded PSRR and THD+N. Bypass capacitor,
CB, values of 0.47µF to 1µF ceramic or tantalum low-ESR
capacitors are recommended for the best THD and noise
performance.
DS6019 Ver 1.1 May. 2007
1
18
Table4. Common Load Impedances vs Low Frequency
Output characteristics in SE Mode
CC
Lowest
RL
Frequency
3Ω
330µF
161Hz
4Ω
330µF
120Hz
8Ω
330µF
60Hz
32Ω
330µF
15Hz
10000Ω
330µF
0.05Hz
47000Ω
330µF
0.01Hz
As Table 4 indicates, most of the bass response is
attenuated into a 4-Ω load and 8-Ω load is adequate,
headphone response is good, and drive into line level
inputs (a home stereo for example) is exceptional.
Using Low- ESR Capacitors
Low- ESR capacitors are recommended throughout this
applications section. A real (as opposed to ideal) capacitor
can be modeled simply as a resistor in series with an ideal
capacitor. The voltage drop across this resistor minimizes
the beneficial effects of the capacitor in the circuit. The
lower the equivalent value of this resistance the more the
real capacitor behaves like an ideal capacitor.
EUA6019
Thermal Pad Considerations
The thermal pad must be connected to ground. The
package with thermal pad of the EUA6019 requires
special attention on thermal design. If the thermal
design issues are not properly addressed, the EUA6019
will go into thermal shutdown when driving a heavy
load.
The thermal pad on the bottom of the EUA6019 should
be soldered down to a copper pad on the circuit board.
Heat can be conducted away from the thermal pad
through the copper plane to ambient. If the copper plane
is not on the top surface of the circuit board, 8 to 10
vias of 13 mil or smaller in diameter should be used to
thermally couple the thermal pad to the bottom plane.
For good thermal conduction, the vias must be plated
through and solder filled. The copper plane used to
conduct heat away from the thermal pad should be as
large as practical.
If the ambient temperature is higher than 25℃,a larger
copper plane or forced-air cooling will be required to
keep the EUA6019 junction temperature below the
thermal shutdown temperature (150℃). In higher
ambient temperature, higher airflow rate and/or larger
copper area will be required to keep the IC out of
thermal shutdown.
DS6019 Ver 1.1 May. 2007
19
EUA6019
Package Information
TSSOP-24
SYMBOLS
A
A1
b
D
E
E1
e
L
D1
E2
DS6019 Ver 1.1 May. 2007
MILLIMETERS
MIN.
MAX.
-----1.20
0.00
0.15
0.19
0.30
7.80
6.20
6.60
4.40
0.65
0.45
0.75
4.60
2.84
20
IN INCHES
MIN.
-----0.000
0.007
0.307
0.244
0.173
0.026
0.018
0.181
0.112
MAX.
0.047
0.006
0.012
0.260
0.030