STMicroelectronics TS4994 Datasheet
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TS4994
1W differential input/output audio power amplifier with selectable standby
Features
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Differential inputs
Near-zero pop & click
100dB PSRR @ 217Hz with grounded inputs
Operating range from V
CC
= 2.5V to 5.5V
1W rail-to-rail output power @ V
CC
THD = 1%, F = 1kHz, with 8 Ω load
= 5V,
90dB CMRR @ 217Hz
Ultra-low consumption in standby mode (10nA)
Selectable standby mode (active low or active high)
Ultra fast startup time: 15ms typ.
Available in DFN10 3x3 (0.5mm pitch) &
MiniSO-8
All lead-free packages
Description
The TS4994 is an audio power amplifier capable of delivering 1W of continuous RMS output power into an 8
Ω
load @ 5V. Due to its differential inputs, it exhibits outstanding noise immunity.
An external standby mode control reduces the supply current to less than 10nA. An STBY
MODE pin allows the standby to be active HIGH or LOW (except in the MiniSO-8 version). An internal thermal shutdown protection is also provided, making the device capable of sustaining short-circuits.
The device is equipped with common mode feedback circuitry allowing outputs to be always
Order codes
Part number
TS4994IQT
TS4994IST
Temperature range
-40°C to +85°C
Package
DFN10
MiniSO-8
Pin connections (top view)
TS4994IQT - DFN10
TS4994IST - MiniSO-8 biased at V
CC
/2 regardless of the input common mode voltage.
The TS4994 is designed for high quality audio applications such as mobile phones and requires few external components.
Applications
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Mobile phones (cellular / cordless)
Laptop / notebook computers
PDAs
Portable audio devices
Packing
Tape & reel
Marking
K994
K994
December 2006 Rev 6 1/35 www.st.com
35
Contents
Contents
TS4994
Application component information . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Absolute maximum ratings and operating conditions . . . . . . . . . . . . . 5
Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Differential configuration principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Gain in typical application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Common mode feedback loop limitations . . . . . . . . . . . . . . . . . . . . . . . . . 21
Low and high frequency response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Calculating the influence of mismatching on PSRR performance . . . . . . 23
Power dissipation and efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
WU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Single-ended input configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2/35
TS4994 Application component information
Components
C s
C b
R feed
R
C in in
Functional description
Supply bypass capacitor that provides power supply filtering.
Bypass capacitor that provides half supply filtering.
Feedback resistor that sets the closed loop gain in conjunction with R in
A
V
= closed loop gain = R feed
/R in
.
Inverting input resistor that sets the closed loop gain in conjunction with R feed
.
Optional input capacitor making a high pass filter together with R in
(F
CL
= 1/(2 π R in
C in
).
.
Figure 1.
Typical application, DFN10 version
Diff. input -
Cin1
Rin1
220nF
Cin2
20k
Rin2
GND
220nF
Diff. Input +
Optional
20k
+
Cb
1u
GND
2
4
5
Rfeed1
20k
Vin-
Vin+
Bypass
Mode
3
Stdby
1
VCC
+
Cs
1u
GND
9
VCC
-
+
Bias
Standby
GND
7
GND
Rfeed2
20k
TS4994IQ
Vo+ 10
Vo-
6
8 Ohms
GND VCC GND VCC
3/35
Application component information
Figure 2.
Typical application, MiniSO-8 version
Diff. input -
Cin1
Rin1
220nF
Cin2
20k
Rin2
GND
220nF
Diff. Input +
Optional
20k
+
Cb
1u
GND
TS4994
Rfeed1
20k
2 Vin-
3 Vin+
4 Bypass
Stdby
1
VCC
+
Cs
1u
GND
7
VCC
-
+
Bias
Standby
GND
6
GND
Rfeed2
20k
TS4994IS
Vo+ 8
Vo-
5
8 Ohms
GND VCC
4/35
TS4994
2
Absolute maximum ratings and operating conditions
Absolute maximum ratings and operating conditions
Table 1.
Symbol
V
CC
V i
T oper
T stg
T j
R thja
P diss
ESD
Absolute maximum ratings
Parameter
Supply voltage
(1)
Input voltage
(2)
Operating free air temperature range
Storage temperature
Maximum junction temperature
Thermal resistance junction to ambient
(3)
DFN10
MiniSO-8
Power dissipation
Human body model
Machine model
Latch-up immunity
Lead temperature (soldering, 10sec)
1.
All voltage values are measured with respect to the ground pin.
2.
The magnitude of the input signal must never exceed V
CC
+ 0.3V / GND - 0.3V.
3.
The device is protected by a thermal shutdown active at 150°C.
Value
6
GND to V
CC
-40 to + 85
-65 to +150
150
120
215 internally limited
2
200
200
260
°C/W
Table 2.
Symbol
Operating conditions
Parameter Value Unit
V
V
V
CC
SM
STBY
T
R
SD
R
L thja
Supply voltage
Standby mode voltage input:
Standby active LOW
Standby active HIGH
Standby voltage input:
Device ON (V
SM
Device OFF (V
SM
= GND) or device OFF (V
SM
= GND) or device ON (V
SM
= V
CC
)
= V
CC
)
Thermal shutdown temperature
Load resistor
Thermal resistance junction to ambient
DFN10
(2)
MiniSO-8
1.5
≤
GND
2.5 to 5.5
V
V
≤
SM
SM
V
=GND
=V
STBY
STBY
150
≥ 8
80
190
CC
V
≤
CC
0.4
(1)
1.
The minimum current consumption (I
STBY temperature range.
) is guaranteed when V
STBY
= GND or V
CC
(i.e. supply rails) for the whole
2.
When mounted on a 4-layer PCB.
V
V
V
°C
Ω
°C/W
W kV
V mA
°C
Unit
V
V
°C
°C
°C
5/35
Electrical characteristics TS4994
Table 3.
Electrical characteristics for V
CC specified)
= +5V, GND = 0V, T amb
= 25°C (unless otherwise
Parameter Min.
Typ.
Max.
Unit Symbol
I
CC
Supply current
No input signal, no load
4 7
I
STBY
V
THD + N
PSRR
CMRR
SNR
GBP t
V
P
ICM
V oo out
N
WU
IG
Standby current
No input signal, V
STBY
= V
SM
No input signal, V
STBY
= V
SM
= GND, R
= V
CC
, R
L
L
= 8 Ω
= 8 Ω
Differential output offset voltage
No input signal, R
L
= 8 Ω
Input common mode voltage
CMRR ≤ -60dB
Output power
THD = 1% Max, F= 1kHz, R
L
= 8 Ω
Total harmonic distortion + noise
P out
= 850mW rms, A
V
= 1, 20Hz
≤
F
≤
L
= 8
Ω
Power supply rejection ratio with inputs grounded
(1)
F = 217Hz, R = 8 Ω, A
V
= 1, C in
= 4.7
μ F, C b
=1 μ F
V ripple
= 200mV
PP
Common mode rejection ratio
F = 217Hz, R
L
= 8 Ω, A
V
= 1, C in
= 4.7
μ F, C b
=1 μ F
V ic
= 200mV
PP
Signal-to-noise ratio (A-weighted filter, A
V
= 2.5)
R
L
= 8 Ω, THD +N < 0.7%, 20Hz ≤ F ≤
Gain bandwidth product
R
L
= 8 Ω
Output voltage noise, 20Hz F ≤
L
= 8 Ω
Unweighted, A
V
= 1
A-weighted, A
V
= 1
Unweighted, A
V
= 2.5
A-weighted, A
V
= 2.5
Unweighted, A
V
= 7.5
A-weighted, A
V
= 7.5
Unweighted, Standby
A-weighted, Standby
Wake-up time
(2)
C b
=1 μ F
0.6
0.8
10
0.1
1
0.5
100
90
100
2
6
5.5
12
10.5
33
28
1.5
1
15
V
1000
10
CC
- 0.9
1.
Dynamic measurements - 20*log(rms(V out
)/rms (V ripple
)). V ripple
is the super-imposed sinus signal relative to V
CC
.
2.
Transition time from standby mode to fully operational amplifier.
mA nA mV
V
W
% dB dB dB
MHz
μ V
RMS ms
6/35
TS4994 Electrical characteristics
Table 4.
Electrical characteristics for V
CC
= +3.3V (all electrical values are guaranteed with correlation measurements at 2.6V and 5V), GND = 0V, T amb
= 25°C (unless otherwise specified)
Parameter Min.
Typ.
Max.
Unit Symbol
I
CC
Supply current no input signal, no load 3 7
I
STBY
V
V
P
V oo
ICM out
THD + N
PSRR
SNR
GBP
N
IG
CMRR
Standby current
No input signal, V
STBY
= V
SM
No input signal, V
STBY
= V
SM
= GND, R
= V
CC
, R
L
L
= 8 Ω
= 8 Ω
Differential output offset voltage
No input signal, R
L
= 8 Ω
Input common mode voltage
CMRR ≤ -60dB
Output power
THD = 1% max, F= 1kHz, R
L
= 8 Ω
Total harmonic distortion + noise
P out
= 300mW rms, A
V
= 1, 20Hz ≤ F ≤
L
= 8 Ω
Power supply rejection ratio with inputs grounded
(1)
F = 217Hz, R = 8 Ω, A
V
= 1, C in
= 4.7
μ F, C b
=1 μ F
V ripple
= 200mV
PP
Common mode rejection ratio
F = 217Hz, R
L
= 8 Ω, A
V
= 1, C in
= 4.7
μ F, C b
=1 μ F
V ic
= 200mV
PP
Signal-to-noise ratio (A-weighted filter, A
V
= 2.5)
R
L
= 8 Ω, THD +N < 0.7%, 20Hz ≤ F ≤
Gain bandwidth product
R
L
= 8 Ω
Output voltage noise, 20Hz F ≤
L
= 8 Ω
Unweighted, A
V
= 1
A-weighted, A
V
= 1
Unweighted, A
V
= 2.5
A-weighted, A
V
= 2.5
Unweighted, A
V
= 7.5
A-weighted, A
V
= 7.5
Unweighted, Standby
A-weighted, Standby
0.6
300
10
0.1
380
0.5
100
90
100
2
6
5.5
12
10.5
33
28
1.5
1
V
1000
10
CC
- 0.9
t
WU
Wake-up time
(2)
C b
=1 μ F
15
1.
Dynamic measurements - 20*log(rms(V out
)/rms (V ripple
)). V ripple
is the super-imposed sinus signal relative to V
CC
.
2.
Transition time from standby mode to fully operational amplifier.
mA nA mV
V mW
% dB dB dB
MHz
μ V
RMS ms
7/35
Electrical characteristics TS4994
Table 5.
Electrical characteristics for V
CC specified)
= +2.6V, GND = 0V, T amb
= 25°C (unless otherwise
Parameter Min.
Typ.
Max.
Unit Symbol
I
CC
Supply current
No input signal, no load
3 7
I
STBY
THD + N
PSRR t
V
V
P oo
ICM out
IG
CMRR
SNR
GBP
V
N
WU
Standby current
No input signal, V
STBY
= V
SM
No input signal, V
STBY
= V
SM
= GND, R
= V
CC
, R
L
L
= 8 Ω
= 8 Ω
Differential output offset voltage
No input signal, R
L
= 8 Ω
Input common mode voltage
CMRR ≤
Output power
THD = 1% max, F= 1kHz, R
L
= 8 Ω
Total harmonic distortion + noise
P out
= 225mW rms, A
V
= 1, 20Hz F ≤
L
= 8 Ω
Power supply rejection ratio with inputs grounded
(1)
F = 217Hz, R = 8
Ω,
A
V
= 1, C in
= 4.7
μ
F, C b
=1
μ
F
V ripple
= 200mV
PP
Common mode rejection ratio
F = 217Hz, R
L
= 8 Ω, A
V
= 1, C in
= 4.7
μ F, C
V ic
= 200mV
PP b
=1 μ F
Signal-to-noise ratio (A-weighted filter, A
V
= 2.5)
R
L
= 8
Ω,
THD +N < 0.7%, 20Hz F 20kHz
Gain bandwidth product
R
L
= 8 Ω
Output voltage noise, 20Hz F ≤
L
= 8 Ω
Unweighted, A
V
= 1
A-weighted, A
V
= 1
Unweighted, A
V
= 2.5
A-weighted, A
V
= 2.5
Unweighted, A
V
= 7.5
A-weighted, A
V
= 7.5
Unweighted, Standby
A-weighted, Standby
Wake-up time
(2)
C b
=1 μ F
0.6
200
10
0.1
250
0.5
100
90
100
2
6
5.5
12
10.5
33
28
1.5
1
15
V
1000
10
CC
- 0.9
1.
Dynamic measurements - 20*log(rms(V out
)/rms (V ripple
)). V ripple
is the super-imposed sinus signal relative to V
CC
.
2.
Transition time from standby mode to fully operational amplifier.
mA nA mV
V mW
% dB dB dB
MHz
μ
V
RMS ms
8/35
TS4994 Electrical characteristics
Figure 3.
Current consumption vs. power supply voltage
4.0
3.5
No load
Tamb=25 ° C
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0 1 2 3
Power Supply Voltage (V)
4 5
Figure 4.
Current consumption vs. standby voltage
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0 1
Standby mode=0V
Standby mode=5V
2 3
Standby Voltage (V)
Vcc = 5V
No load
Tamb=25 ° C
4 5
Figure 5.
Current consumption vs. power supply voltage
3.5
3.0
2.5
Standby mode=0V
Standby mode=3.3V
2.0
1.5
1.0
0.5
0.0
0.0
0.6
1.2
1.8
Standby Voltage (V)
2.4
Vcc = 3.3V
No load
Tamb=25 ° C
3.0
Figure 6.
Current consumption vs. standby voltage
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0.0
Standby mode=0V
Standby mode=2.6V
0.6
1.2
1.8
Standby Voltage (V)
Vcc = 2.6V
No load
Tamb=25 ° C
2.4
Figure 7.
Differential DC output voltage vs. common mode input voltage
1000
Av = 1
Tamb = 25 ° C
100
Vcc=3.3V
Vcc=2.5V
10
Vcc=5V
1
Figure 8.
Power dissipation vs. output power
0.6
0.4
RL=8 Ω
0.2
0.1
0.01
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Common Mode Input Voltage (V)
0.0
0.0
0.2
RL=16 Ω
0.4
0.6
Output Power (W)
Vcc=5V
F=1kHz
THD+N<1%
0.8
1.0
9/35
Electrical characteristics TS4994
Figure 9.
Power dissipation vs. output power Figure 10.
Power dissipation vs. output power
0.3
0.20
Vcc=2.6V
F=1kHz
THD+N<1%
RL=8 Ω
0.15
0.2
RL=8 Ω
0.10
0.1
0.0
0.0
0.1
RL=16 Ω
0.2
0.3
Output Power (W)
Vcc=3.3V
F=1kHz
THD+N<1%
0.4
Figure 11.
Output power vs. power supply voltage
1.0
0.8
Cb = 1 μ F
F = 1kHz
BW < 125kHz
Tamb = 25 ° C
0.6
8 Ω
16 Ω
0.05
0.00
0.0
RL=16 Ω
0.1
0.2
Output Power (W)
Figure 12.
Output power vs. power supply voltage
1.50
1.25
1.00
Cb = 1 μ F
F = 1kHz
BW < 125kHz
Tamb = 25 ° C
8 Ω
16 Ω
0.75
0.3
0.4
0.2
0.50
0.25
32 Ω 32 Ω
0.0
2.5
3.0
3.5
Vcc (V)
4.0
4.5
5.0
0.00
2.5
3.0
3.5
Vcc (V)
4.0
4.5
5.0
Figure 13.
Output power vs. load resistance Figure 14.
Power derating curves
1.0
1.5
0.8
Vcc=5V
Vcc=4.5V
THD+N=1%
Cb = 1 F
F = 1kHz
BW < 125kHz
Tamb = 25 ° C 1.0
with 4 layers PCB
0.6
Vcc=4V
0.4
0.5
AMR Value
0.2
0.0
Vcc=3.5V
12
Vcc=3V
Vcc=2.5V
20
Load Resistance
28
0.0
0 25 50 75
Ambiant Temperature ( C)
100 125
10/35
TS4994 Electrical characteristics
Figure 15.
Power derating curves
0.6
0.4
0.2
AMR Value
Nominal Value
0.0
0 25 50 75
Ambiant Temperature ( C)
100
Figure 17.
Open loop gain vs. frequency
60
Gain
40
20
Phase
0
-20
-40
0.1
Vcc = 3.3V
ZL = 8 Ω + 500pF
Tamb = 25 ° C
1 10 100
Frequency (kHz)
-120
-160
1000
-200
10000
0
-40
-80
125
Figure 16.
Open loop gain vs. frequency
0
60
40
Gain
20
Phase
0
-20
-40
0.1
Vcc = 5V
ZL = 8 Ω + 500pF
Tamb = 25 ° C
1 10 100
Frequency (kHz)
-40
-80
-120
-160
1000
-200
10000
Figure 18.
Open loop gain vs. frequency
0
60
40
Gain
20 Phase
0
-20
-40
0.1
Vcc = 2.6V
ZL = 8 Ω + 500pF
Tamb = 25 ° C
1 10 100
Frequency (kHz)
-40
-80
-120
-160
1000
-200
10000
Figure 19.
Closed loop gain vs. frequency
0 10
0
Gain
Phase
-40
-10
-20
Vcc = 5V
-30
Av = 1
ZL = 8 Ω + 500pF
-40
0.1
Tamb = 25 ° C
1 10 100
Frequency (kHz)
-80
-120
-160
1000
-200
10000
Figure 20.
Closed loop gain vs. frequency
0 10
0
Gain
Phase
-40
-10
-20
Vcc = 3.3V
-30
Av = 1
ZL = 8 Ω + 500pF
-40
0.1
Tamb = 25 ° C
1 10 100
Frequency (kHz)
-80
-120
-160
1000
-200
10000
11/35
Electrical characteristics TS4994
Figure 21.
Closed loop gain vs. frequency
0 10
0
Gain
Phase
-40
-10
-20
Vcc = 2.6V
-30
-40
0.1
Av = 1
ZL = 8 Ω + 500pF
Tamb = 25 ° C
1 10 100
Frequency (kHz)
-80
-120
-160
1000
-200
10000
Figure 22.
PSRR vs. frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
20
Vcc = 5V
Vripple = 200mVpp
Inputs = Grounded
Av = 1, Cin = 4.7
μ F
RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=0.47
Cb=1 μ F
μ F
1000
Frequency (Hz)
Cb=0.1
μ F
Cb=0
10000 20k
Figure 23.
PSRR vs. frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
20
Vcc = 3.3V
Vripple = 200mVpp
Inputs = Grounded
Av = 1, Cin = 4.7
μ F
RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=0.47
Cb=1 μ F
μ F
1000
Frequency (Hz)
Cb=0.1
μ F
Cb=0
10000 20k
Figure 24.
PSRR vs. frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
20
Vcc = 2.6V
Vripple = 200mVpp
Inputs = Grounded
Av = 1, Cin = 4.7
μ F
RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=0.47
Cb=1 μ F
μ F
1000
Frequency (Hz)
Cb=0.1
μ F
Cb=0
10000 20k
Figure 25.
PSRR vs. frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
20
Vcc = 5V
Vripple = 200mVpp
Inputs = Grounded
Av = 2.5, Cin = 4.7
μ F
RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=1
Cb=0.47
μ F
Cb=0.1
μ
1000
F
Frequency (Hz)
μ F
Cb=0
10000 20k
Figure 26.
PSRR vs. frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
20
Vcc = 3.3V
Vripple = 200mVpp
Inputs = Grounded
Av = 2.5, Cin = 4.7
μ F
RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=1
Cb=0.47
μ F
Cb=0.1
μ
1000
F
Frequency (Hz)
μ F
Cb=0
10000 20k
12/35
TS4994 Electrical characteristics
Figure 27.
PSRR vs. frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
20
Vcc = 2.6V
Vripple = 200mVpp
Inputs = Grounded
Av = 2.5, Cin = 4.7
μ F
RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=1
Cb=0.47
μ F
Cb=0.1
μ
1000
F
Frequency (Hz)
μ F
Cb=0
10000 20k
Figure 28.
PSRR vs. frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
20
Vcc = 5V
Vripple = 200mVpp
Inputs = Floating
Rfeed = 20k Ω
RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=0.47
Cb=1 μ F
μ F
1000
Frequency (Hz)
Cb=0.1
μ F
Cb=0
10000 20k
Figure 29.
PSRR vs. frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
20
Vcc = 3.3V
Vripple = 200mVpp
Inputs = Floating
Rfeed = 20k Ω
RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=0.47
Cb=1 μ F
μ F
1000
Frequency (Hz)
Cb=0.1
μ F
Cb=0
10000 20k
Figure 30.
PSRR vs. frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
20
Vcc = 2.6V
Vripple = 200mVpp
Inputs = Floating
Rfeed = 20k Ω
RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=0.47
Cb=1 μ F
μ F
1000
Frequency (Hz)
Cb=0.1
μ F
Cb=0
10000 20k
Figure 31.
PSRR vs. common mode input voltage
0
-20
-40
Vcc = 5V
Vripple = 200mVpp
Inputs Grounded
F = 217Hz
Av = 1
RL ≥ 8 Ω
Tamb = 25 ° C
-60
Cb=0
-80
Cb=1 μ F
Cb=0.47
μ F
Cb=0.1
μ F
-100
0 1 2 3
Common Mode Input Voltage (V)
4 5
Figure 32.
PSRR vs. common mode input voltage
0
-20
-40
Vcc = 3.3V
Vripple = 200mVpp
Inputs Grounded
F = 217Hz
Av = 1
RL ≥ 8 Ω
Tamb = 25 ° C
-60
Cb=0
-80
-100
0.0
0.6
1.2
Cb=1 μ F
Cb=0.47
Cb=0.1
1.8
μ
μ
F
F
2.4
Common Mode Input Voltage (V)
3.0
13/35
Electrical characteristics
Figure 33.
PSRR vs. common mode input voltage
0
-20
-40
Vcc = 2.5V
Vripple = 200mVpp
Inputs Grounded
F = 217Hz
Av = 1
RL ≥ 8 Ω
Tamb = 25 ° C
-60
-80
-100
0.0
0.5
1.0
Cb=0
1.5
Cb=1
2.0
Common Mode Input Voltage (V)
μ
Cb=0.1
F
Cb=0.47
μ
μ
F
F
2.5
Figure 34.
CMRR vs. frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
20
Vcc = 5V
Vic = 200mVpp
Av = 1, Cin = 470 μ F
RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=1 μ F
Cb=0.47
μ F
Cb=0.1
Cb=0
μ F
1000
Frequency (Hz)
Figure 35.
CMRR vs. frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
20
Vcc = 3.3V
Vic = 200mVpp
Av = 1, Cin = 470 μ F
RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=1 μ F
Cb=0.47
μ F
Cb=0.1
Cb=0
μ F
1000
Frequency (Hz)
Figure 37.
CMRR vs. frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
20
Vcc = 5V
Vic = 200mVpp
Av = 2.5, Cin = 470 μ F
RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=1 μ F
Cb=0.47
μ F
Cb=0.1
Cb=0
μ F
1000
Frequency (Hz)
10000 20k
10000 20k
Figure 36.
CMRR vs. frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
20
Vcc = 2.6V
Vic = 200mVpp
Av = 1, Cin = 470 μ F
RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=1 μ F
Cb=0.47
μ F
Cb=0.1
Cb=0
μ F
1000
Frequency (Hz)
Figure 38.
CMRR vs. frequency
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
20
Vcc = 3.3V
Vic = 200mVpp
Av = 2.5, Cin = 470 μ F
RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=1 μ F
Cb=0.47
μ F
Cb=0.1
Cb=0
μ F
1000
Frequency (Hz)
TS4994
10000 20k
10000 20k
10000 20k
14/35
TS4994 Electrical characteristics
Figure 39.
CMRR vs. frequency
-30
-40
-50
-60
0
-10
-20
-70
-80
-90
-100
20
Vcc = 2.6V
Vic = 200mVpp
Av = 2.5, Cin = 470 μ F
RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=1 μ F
Cb=0.47
μ F
Cb=0.1
Cb=0
μ F
1000
Frequency (Hz)
10000 20k
Figure 41.
CMRR vs. common mode input voltage
0
Vcc=3.3V
-20
-40
Vcc=2.5V
-60
-80
Vic = 200mVpp
F = 217Hz
Av = 1, Cb = 1 μ F
RL ≥ 8 Ω
Tamb = 25 ° C
-100
Vcc=5V
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Common Mode Input Voltage (V)
Figure 42.
THD+N vs. output power
0
-20
-40
Vcc=2.5V
Vcc=3.3V
-60
-80
Vic = 200mVpp
F = 217Hz
Av = 1, Cb = 0
RL ≥ 8 Ω
Tamb = 25 ° C
-100
Vcc=5V
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Common Mode Input Voltage (V)
Figure 40.
CMRR vs. common mode input voltage
10
1
RL = 8 Ω
F = 20Hz
Av = 1
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
0.1
0.01
1E-3
1E-3
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.01
0.1
Output Power (W)
1
Figure 43.
THD+N vs. output power
10
1
RL = 8 Ω
F = 20Hz
Av = 2.5
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
0.1
Vcc=2.6V
Vcc=3.3V
Vcc=5V
Figure 44.
10
1
RL = 8 Ω
F = 20Hz
Av = 7.5
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
0.1
THD+N vs. output power
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.01
1E-3
1E-3 0.01
0.1
Output Power (W)
1
0.01
1E-3 0.01
0.1
Output Power (W)
1
15/35
Electrical characteristics
Figure 45.
THD+N vs. output power
10
1
RL = 8 Ω
F = 1kHz
Av = 1
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.1
0.01
1E-3 0.01
0.1
Output Power (W)
Figure 47.
THD+N vs. output power
10
1
RL = 8 Ω
F = 1kHz
Av = 7.5
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.1
1
0.01
1E-3 0.01
0.1
Output Power (W)
Figure 49.
THD+N vs. output power
10
1
RL = 8 Ω
F = 20kHz
Av = 2.5
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
1
0.1
1E-3 0.01
0.1
Output Power (W)
1
TS4994
Figure 46.
THD+N vs. output power
10
1
RL = 8 Ω
F = 1kHz
Av = 2.5
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.1
0.01
1E-3 0.01
0.1
Output Power (W)
Figure 48.
THD+N vs. output power
10
1
RL = 8 Ω
F = 20kHz
Av = 1
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
1
0.1
1E-3 0.01
0.1
Output Power (W)
Figure 50.
THD+N vs. output power
10
1
RL = 8 Ω
F = 20kHz
Av = 7.5
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
1
0.1
1E-3 0.01
0.1
Output Power (W)
1
16/35
TS4994
Figure 51.
THD+N vs. output power
10
1
0.1
RL = 16 Ω
F = 20Hz
Av = 1
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.01
1E-3
1E-3 0.01
Output Power (W)
0.1
Figure 53.
THD+N vs. output power
10
1
RL = 16 Ω
F = 1kHz
Av = 1
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
0.1
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.01
1E-3
1E-3 0.01
Output Power (W)
0.1
Figure 55.
THD+N vs. output power
10
1
RL = 16 Ω
F = 20kHz
Av = 1
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.1
Electrical characteristics
Figure 52.
THD+N vs. output power
10
1
RL = 16 Ω
F = 20Hz
Av = 7.5
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
0.1
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.01
1
1E-3
1E-3 0.01
Output Power (W)
0.1
Figure 54.
THD+N vs. output power
10
1
RL = 16 Ω
F = 1kHz
Av = 7.5
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
0.1
Vcc=2.6V
Vcc=3.3V
Vcc=5V
1
1
0.01
1E-3 0.01
Output Power (W)
0.1
Figure 56.
THD+N vs. output power
10
1
RL = 16 Ω
F = 20kHz
Av = 7.5
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
1
0.01
1E-3 0.01
Output Power (W)
0.1
1
0.1
1E-3 0.01
Output Power (W)
0.1
1
17/35
Electrical characteristics
Figure 57.
THD+N vs. output power
10
1
RL = 8 Ω
Vcc = 5V
Av = 1
Cb = 0
BW < 125kHz
Tamb = 25 ° C
F=20kHz
F=1kHz
0.1
F=20Hz
0.01
1E-3 0.01
0.1
Output Power (W)
1
Figure 59.
THD+N vs. output power
10
1
RL = 16 Ω
Vcc = 5V
Av = 1, Cb = 0
BW < 125kHz
Tamb = 25 ° C
0.1
F=20kHz
F=1kHz
F=20Hz
0.01
1E-3
1E-3
Figure 61.
THD+N vs. frequency
10
1
RL = 8 Ω
Av = 1
Cb = 1 μ F
Bw < 125kHz
Tamb = 25 ° C
0.1
Vcc=2.6V, Po=225mW
0.01
1E-3
20
0.01
0.1
Output Power (W)
1
100
Vcc=5V, Po=850mW
1000
Frequency (Hz)
10000 20k
Figure 58.
THD+N vs. output power
10
1
RL = 8 Ω
Vcc = 2.6V
Av = 1, Cb = 0
BW < 125kHz
Tamb = 25 ° C
0.1
F=20kHz
F=1kHz
0.01
1E-3
1E-3
F=20Hz
0.01
Output Power (W)
0.1
Figure 60.
THD+N vs. output power
10
1
RL = 16 Ω
Vcc = 2.6V
Av = 1, Cb = 0
BW < 125kHz
Tamb = 25 ° C
0.1
F=20kHz
F=1kHz
F=20Hz
0.01
TS4994
1E-3
1E-3 0.01
Output Power (W)
0.1
Figure 62.
THD+N vs. frequency
10
1
RL = 8 Ω
Av = 1
Cb = 0
Bw < 125kHz
Tamb = 25 ° C
0.1
Vcc=2.6V, Po=225mW
0.01
1E-3
20 100
Vcc=5V, Po=850mW
1000
Frequency (Hz)
10000 20k
18/35
TS4994
Figure 63.
THD+N vs. frequency
10
1
RL = 8 Ω
Av = 7.5
Cb = 1 μ F
Bw < 125kHz
Tamb = 25 ° C
Vcc=2.6V, Po=225mW
Electrical characteristics
Figure 64.
THD+N vs. frequency
10
1
RL = 8 Ω
Av = 7.5
Cb = 0
Bw < 125kHz
Tamb = 25 ° C
Vcc=2.6V, Po=225mW
0.1
0.1
0.01
20 100
Vcc=5V, Po=850mW
1000
Frequency (Hz)
10000 20k
Figure 65.
THD+N vs. frequency
10
1
RL = 16 Ω
Av = 1
Cb = 1 μ F
Bw < 125kHz
Tamb = 25 ° C
0.1
Vcc=2.6V, Po=155mW
0.01
20 100
Vcc=5V, Po=850mW
1000
Frequency (Hz)
10000 20k
Figure 66.
THD+N vs. frequency
10
1
RL = 16 Ω
Av = 7.5
Cb = 1 μ F
Bw < 125kHz
Tamb = 25 ° C
0.1
Vcc=2.6V, Po=155mW
0.01
0.01
1E-3
20 100
Vcc=5V, Po=600mW
1000
Frequency (Hz)
10000 20k
1E-3
20 100
Vcc=5V, Po=600mW
1000
Frequency (Hz)
10000 20k
Figure 67.
SNR vs. power supply voltage with unweighted filter
Figure 68.
SNR vs. power supply voltage with
A-weighted filter
110 110
RL=16 Ω
RL=16 Ω
105 105
100
95 RL=8 Ω
90
Av = 2.5
Cb = 1 μ F
85
THD+N < 0.7%
80
2.5
Tamb = 25 ° C
3.0
3.5
4.0
Power Supply Voltage (V)
4.5
5.0
100
95
RL=8 Ω
90
Av = 2.5
Cb = 1 μ F
85
THD+N < 0.7%
80
2.5
Tamb = 25 ° C
3.0
3.5
4.0
Power Supply Voltage (V)
4.5
5.0
19/35
Electrical characteristics
Figure 69.
Startup time vs. bypass capacitor
20
Tamb=25 ° C
Vcc=5V
15
Vcc=3.3V
10
5
Vcc=2.6V
0
0.0
0.4
0.8
1.2
1.6
Bypass Capacitor Cb ( F)
2.0
TS4994
20/35
TS4994 Application information
4.2
Note:
4.3
The TS4994 is a monolithic full-differential input/output power amplifier. The TS4994 also includes a common mode feedback loop that controls the output bias value to average it at
V
CC
/2 for any DC common mode input voltage. This allows the device to always have a maximum output voltage swing, and by consequence, maximize the output power.
Moreover, as the load is connected differentially, compared to a single-ended topology, the output is four times higher for the same power supply voltage.
●
●
●
The advantages of a full-differential amplifier are:
●
●
●
Very high PSRR (power supply rejection ratio).
High common mode noise rejection.
Virtually zero pop without additional circuitry, giving a faster start-up time compared with conventional single-ended input amplifiers.
Easier interfacing with differential output audio DAC.
No input coupling capacitors required due to common mode feedback loop.
In theory, the filtering of the internal bias by an external bypass capacitor is not necessary. But, to reach maximum performance in all tolerance situations, it is better to keep this option.
The main disadvantage is:
● As the differential function is directly linked to the mismatch between external resistors, paying particular attention to this mismatch is mandatory in order to get the best performance from the amplifier.
Gain in typical application schematic
Typical differential applications are shown in
In the flat region of the frequency-response curve (no C in expressed by the relation:
effect), the differential gain is
A
V diff
=
V – V
------------------------------------------------------
Diff input+
– Diff input-
=
R
--------------
R in where R in
= R in1
= R in2
and R feed
= R feed1
= R feed2
.
For the rest of this section, Av diff
will be called A
V
to simplify the expression.
Common mode feedback loop limitations
As explained previously, the common mode feedback loop allows the output DC bias voltage to be averaged at V
CC
/2 for any DC common mode bias input voltage.
However, due to V
ICM
limitation of the input stage (see Table 3 on page 6
), the common mode feedback loop can play its role only within a defined range. This range depends upon
21/35
Application information TS4994 the values of V
CC
, R in
and R feed
( A
V
). To have a good estimation of the V
ICM
value, use the following formula:
V
ICM
=
V × ×
------------------------------------------------------------------------- (V)
2
R in
× (
+
R
2 in
×
+
V
R feed
)
R feed with
V ic
=
Diff +
------------------------------------------------------ (V)
2
Diff input-
The result of the calculation must be in the range:
≤
ICM
≤ V
CC
– 0.9V
If the result of the V
ICM
calculation is not in this range, an input coupling capacitor must be used.
Example: With V
CC
=2.5V, R in
= R feed
= 20k and V ic
= 2V, we find V
ICM
= 1.63V. This is higher than 2.5V - 0.9V = 1.6V, so input coupling capacitors are required. Alternatively, you can change the V ic
value.
4.4 Low and high frequency response
In the low frequency region, C in
starts to have an effect. C in
forms, with R in
, a high-pass filter with a -3dB cut-off frequency. F
CL
is in Hz.
F
CL
=
1
2 × π × R in
× C in
( Hz )
In the high-frequency region, you can limit the bandwidth by adding a capacitor (C feed
) in parallel with R feed
. It forms a low-pass filter with a -3dB cut-off frequency. F
CH
is in Hz.
F
CH
=
1
2 × π × R feed
× C feed
( Hz )
While these bandwidth limitations are in theory attractive, in practice, because of low performance in terms of capacitor precision (and by consequence in terms of mismatching), they deteriorate the values of PSRR and CMRR.
The influence of mismatching on PSRR and CMRR performance is discussed in more detail in the following sections.
Example: A typical application with input coupling and feedback capacitor with F
CL and F
CH
= 8kHz. We assume that the mismatching between R in1,2
and C feed1,2
= 50Hz
can be neglected. If we sweep the frequency from DC to 20kHz we observe the following with respect to the PSRR value:
● From DC to 200Hz, the C in
impedance decreases from infinite to a finite value and the
C feed
impedance is high enough to be neglected. Due to the tolerance of C in1,2
, we
22/35
TS4994 Application information
●
● must introduce a mismatch factor (R in1 performance.
x C in
≠
R in2 x C in2
) that will decrease the PSRR
From 200Hz to 5kHz, the C in
impedance is low enough to be neglected when compared with R in,
and the C feed
impedance is high enough to be neglected as well. In this range, we can reach the PSRR performance of the TS4994 itself.
From 5kHz to 20kHz, the C in
impedance is low to be neglected when compared to R in, and the C feed
impedance decreases to a finite value. Due to tolerance of C feed1,2
, we introduce a mismatching factor (R feed1 x C feed1
≠
R feed2 x C feed2
) that will decrease the
PSRR performance.
4.5 Calculating the influence of mismatching on PSRR performance
For calculating PSRR performance, we consider that C in
and C feed
have no influence.
We use the same kind of resistor (same tolerance) and Δ R is the tolerance value in %.
The following PSRR equation is valid for frequencies ranging from DC to about 1kHz.
The PSRR equation is ( Δ R in %):
PSRR
≤
20
×
Log
⎣
⎢
⎡ Δ
R
( 10000
×
100
− Δ
R
2
) ⎦
⎥
⎤
( dB )
This equation doesn't include the additional performance provided by bypass capacitor filtering. If a bypass capacitor is added, it acts, together with the internal high output impedance bias, as a low-pass filter, and the result is a quite important PSRR improvement with a relatively small bypass capacitor.
The complete PSRR equation (
Δ
R in %, C b
in microFarad and F in Hz) is:
PSRR
≤ 20 × log
(1000 –
Δ
R
2
)
×
R ×
1
100
+ F
2
×
C b
2
×
22.2
)
Example: With
Δ
R = 0.1% and C b
= 0, the minimum PSRR would be -60dB. With a 100nF bypass capacitor, at 100Hz the new PSRR would be -93dB.
This example is a worst case scenario, where each resistor has extreme tolerance. It illustrates the fact that with only a small bypass capacitor, the TS4994 provides high PSRR performance.
Note also that this is a theoretical formula. Because the TS4994 has self-generated noise, you should consider that the highest practical PSRR reachable is about -110dB. It is therefore unreasonable to target a -120dB PSRR.
23/35
Application information TS4994
The three following graphs show PSRR versus frequency and versus bypass capacitor C b
in worst-case conditions (
Δ
R = 0.1%).
Figure 70.
PSRR vs. frequency (worst case conditions)
Figure 71.
PSRR vs. frequency (worst case conditions)
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
20
Vcc = 5V, Vripple = 200mVpp
Av = 1, Cin = 4.7
μ F
Δ R/R = 0.1%, RL ≥ 8 Ω
Tamb = 25 ° C, Inputs = Grounded
Cb=1
100
μ F
Cb=0.1
μ F
Cb=0.47
μ F
1000
Frequency (Hz)
Cb=0
10000 20k
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
20
Vcc = 3.3V, Vripple = 200mVpp
Av = 1, Cin = 4.7
μ F
Δ R/R = 0.1%, RL ≥ 8 Ω
Tamb = 25 ° C, Inputs = Grounded
Cb=1
100
μ F
Cb=0.1
μ F
Cb=0.47
μ F
1000
Frequency (Hz)
Cb=0
10000 20k
Figure 72.
PSRR vs. frequency (worst case conditions)
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
20
Vcc = 2.5V, Vripple = 200mVpp
Av = 1, Cin = 4.7
μ F
Δ R/R = 0.1%, RL ≥ 8 Ω
Tamb = 25 ° C, Inputs = Grounded
Cb=1
100
μ F
Cb=0.1
μ F
Cb=0.47
μ F
1000
Frequency (Hz)
Cb=0
10000 20k
24/35
TS4994 Application information
The two following graphs show typical applications of the TS4994 with a random selection of four
Δ
R/R values with a 0.1% tolerance.
Figure 73.
PSRR vs. frequency with random choice condition
Figure 74.
PSRR vs. frequency with random choice condition
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
20
Vcc = 5V, Vripple = 200mVpp
Av = 1, Cin = 4.7
μ F
Δ R/R ≤ 0.1%, RL ≥ 8 Ω
Tamb = 25 ° C, Inputs = Grounded
Cb=1
100
μ F
Cb=0.1
μ F
Cb=0.47
μ F
1000
Frequency (Hz)
Cb=0
10000 20k
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
20
Vcc = 2.5V, Vripple = 200mVpp
Av = 1, Cin = 4.7
μ F
Δ R/R ≤ 0.1%, RL ≥ 8 Ω
Tamb = 25 ° C, Inputs = Grounded
Cb=1
100
μ F
Cb=0.1
μ F
Cb=0.47
μ F
1000
Frequency (Hz)
Cb=0
10000 20k
For calculating CMRR performance, we consider that C in
and C feed
have no influence. C b has no influence in the calculation of the CMRR.
We use the same kind of resistor (same tolerance) and
Δ
R is the tolerance value in %.
The following CMRR equation is valid for frequencies ranging from DC to about 1kHz.
The CMRR equation is (
Δ
R in %):
CMRR ≤ 20 × Log
⎣
⎢
⎡ Δ
R
( 10000
×
−
200
Δ
R
2
) ⎦
⎥
⎤
Example: With
Δ
R = 1%, the minimum CMRR is -34dB.
( dB )
This example is a worst case scenario where each resistor has extreme tolerance. Ut illustrates the fact that for CMRR, good matching is essential.
As with the PSRR, due to self-generated noise, the TS4994 CMRR limitation is about
-110dB.
and
Figure 76 show CMRR versus frequency and versus bypass capacitor C
b worst-case conditions (
Δ
R=0.1%).
in
25/35
Application information TS4994
Figure 75.
CMR vs. frequency (worst case conditions)
0
-10
-20
Vcc = 5V
Vic = 200mVpp
Av = 1, Cin = 470 μ F
Δ R/R = 0.1%, RL ≥ 8 Ω
Tamb = 25 ° C
-30
-40
-50
-60
20 100
Cb=1
Cb=0
μ F
1000
Frequency (Hz)
10000 20k
Figure 76.
CMR vs. frequency (worst case conditions)
0
-10
-20
Vcc = 2.5V
Vic = 200mVpp
Av = 1, Cin = 470 μ F
Δ R/R = 0.1%, RL ≥ 8 Ω
Tamb = 25 ° C
-30
-40
-50
-60
20 100
Cb=1
Cb=0
μ F
1000
Frequency (Hz)
10000 20k
and
Figure 78 show CMRR versus frequency for a typical application with a
random selection of four
Δ
R/R values with a 0.1% tolerance.
Figure 77.
CMR vs. frequency with random choice condition
Figure 78.
CMR vs. frequency with random choice condition
-40
-50
-60
0
-10
-20
-30
Vcc = 5V
Vic = 200mVpp
Av = 1, Cin = 470 μ F
Δ R/R ≤ 0.1%, RL ≥ 8 Ω
Tamb = 25 ° C
-70
-80
-90
20 100
Cb=1
Cb=0
μ F
1000
Frequency (Hz)
10000 20k
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
20
Vcc = 2.5V
Vic = 200mVpp
Av = 1, Cin = 470 μ F
Δ R/R ≤ 0.1%, RL ≥ 8 Ω
Tamb = 25 ° C
100
Cb=1
Cb=0
μ F
1000
Frequency (Hz)
10000 20k
4.7
26/35
Power dissipation and efficiency
Assumptions:
●
●
Load voltage and current are sinusoidal (V
Supply voltage is a pure DC source (V
CC
) out
and I out
)
The output voltage is:
V out
= Vpeak sin ω t (V) and
I out
=
V out
------------ (A)
R
L
TS4994
Note:
Application information and
P out
=
V peak
L
2
-------------------- (W)
2R
Therefore, the average current delivered by the supply voltage is:
Equation 1
I
CC AVG = 2
V peak
π R
L
---------------- (A)
The power delivered by the supply voltage is:
P supply
= V
CC
⋅ I
CC
AVG
(W)
Therefore, the power dissipated by each amplifier is:
P diss
= P supply
– P out
(W)
Equation 2
P diss
=
2 2V
---------------------P
π R
L out
– P out and the maximum value is obtained when:
∂
P diss
∂
P out
----------------- = 0 and its value is:
Equation 3
Pdiss max
=
2 Vcc
2
π 2
R
L
( W )
This maximum value is only dependent on the power supply voltage and load values.
The efficiency is the ratio between the output power and the power supply:
Equation 4
η
=
P
------------------ =
P supply
π V
--------------------
4V
CC
The maximum theoretical value is reached when V
PEAK
= V
CC
, so:
η =
π
= 78.5%
4
The maximum die temperature allowable for the TS4994 is 125°C. However, in case of overheating, a thermal shutdown set to 150°C, puts the TS4994 in standby until the temperature of the die is reduced by about 5°C.
27/35
Application information
To calculate the maximum ambient temperature T amb
allowable, you need to know:
● The value of the power supply voltage, V
CC
●
●
The value of the load resistor, R
L
The R thja value for the package type
Example: V
CC
= 5V, R
L
= 8 Ω, R thja
= 80°C/W
Using the power dissipation formula given above in Equation 3 this gives a result of:
P dissmax
= 633mW
T amb
is calculated as follows:
Equation 5
T amb
= 125 ° C – R
TJHA
× P dissmax
Therefore, the maximum allowable value for T amb
is:
T amb
= 125-80x0.633=74°C
TS4994
4.8 Decoupling of the circuit
Two capacitors are needed to correctly bypass the TS4994. A power supply bypass capacitor C s
and a bias voltage bypass capacitor C b
.
C s
has particular influence on the THD+N in the high frequency region (above 7kHz) and an indirect influence on power supply disturbances. With a value for C s of 1µF, you can expect similar THD+N performance to that shown in the datasheet.
In the high frequency region, if C s
is lower than 1µF, it increases THD+N, and disturbances on the power supply rail are less filtered.
On the other hand, if C s
is higher than 1µF, the disturbances on the power supply rail are more filtered.
C b
has an influence on THD+N at lower frequencies, but its function is critical to the final result of PSRR (with input grounded and in the lower frequency region).
4.9 Wake-up time: t
WU
When the standby is released to put the device ON, the bypass capacitor C b
is not charged immediately. As C b
is directly linked to the bias of the amplifier, the bias will not work properly until the C b
voltage is correct. The time to reach this voltage is called the wake-up time or t
WU
and is specified in
, with C b
=1µF. During the wake-up time, the
TS4994 gain is close to zero. After the wake-up time, the gain is released and set to its nominal value.
If C b
has a value other than 1µF, refer to the graph in Figure 69 on page 20 to establish the
wake-up time.
28/35
TS4994 Application information
Note:
When the standby command is set, the time required to put the two output stages in high impedance and the internal circuitry in shutdown mode is a few microseconds.
In shutdown mode, the Bypass pin and Vin+, Vin- pins are short-circuited to ground by internal switches. This allows a quick discharge of the C b
and C in
capacitors.
Due to its fully differential structure, the pop performance of the TS4994 is close to perfect.
However, due to mismatching between internal resistors R in
, R feed
, and external input capacitors C in
, some noise might remain at startup. To eliminate the effect of mismatched components, the TS4994 includes pop reduction circuitry. With this circuitry, the TS4994 is close to zero pop for all possible common applications.
In addition, when the TS4994 is in standby mode, due to the high impedance output stage in this configuration, no pop is heard.
4.12 Single-ended input configuration
It is possible to use the TS4994 in a single-ended input configuration. However, input
coupling capacitors are needed in this configuration. The schematic in Figure 79
shows this configuration using the MiniSO-8 version of the TS4994 as an example.
Figure 79.
Single-ended input typical application
Ve
GND
Cin1
Rin1
220nF
Cin2
20k
Rin2
220nF
20k
Optional +
Cb
1u
GND
Rfeed1
20k
2 Vin-
3 Vin+
4 Bypass
Stdby
1
VCC
+
Cs
1u
GND
7
VCC
-
+
Bias
Standby
GND
6
GND
Rfeed2
20k
TS4994IS
Vo+ 8
Vo-
5
8 Ohms
GND VCC
29/35
Application information TS4994
The component calculations remain the same, except for the gain. In single-ended input configuration, the formula is:
Av
SE
=
V
O
+
−
Ve
V
O
−
=
R feed
R in
4.13 Demoboard
A demoboard for the TS4994 is available. It is designed for the TS4994 in the DFN10 package. However, we can guarantee that all electrical parameters except the power dissipation are similar for all packages.
For more information about this demoboard, refer to Application Note AN2013.
30/35
TS4994
5 Package mechanical data
Package mechanical data
In order to meet environmental requirements, STMicroelectronics offers these devices in
ECOPACK
®
packages. These packages have a Lead-free second level interconnect. The category of second level interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an STMicroelectronics trademark. ECOPACK specifications are available at: www.st.com
.
31/35
Package mechanical data
ackage
Ref.
b
D
D2
E
A
A1
A2
A3
E2 e
L
Min.
0.80
0.18
2.21
1.49
0.3
Dimensions
Millimeters
Typ.
0.23
3.00
2.26
3.00
0.90
0.02
0.70
0.20
1.64
0.50
0.4
Max.
1.00
0.05
0.30
2.31
1.74
0.5
Min.
31.5
7.1
87.0
58.7
11.8
TS4994
Mils
Typ.
35.4
0.8
25.6
7.9
9.1
118.1
89.0
118.1
64.6
19.7
15.7
Max.
39.4
2.0
11.8
91.0
68.5
19.7
32/35
TS4994 Package mechanical data
Ref.
c
D
E
E1
A
A1
A2 b e
K
L
L1
Min.
0.05
0.78
0.25
0.13
2.90
4.75
2.90
0°
0.40
Dimensions
0.10
0.86
0.33
0.18
3.00
4.90
3.00
0.65
Millimeters
Typ.
Max.
0.23
3.10
5.05
3.10
1.1
0.15
0.94
0.40
0.55
6°
0.70
0.10
Min.
0°
0.016
0.002
0.031
0.010
0.005
0.114
0.187
0.114
Inches
Typ.
0.004
0.034
0.013
0.007
0.118
0.193
0.118
0.026
0.022
Max.
0.043
0.006
0.037
0.016
0.009
0.122
0.199
0.122
6°
0.028
0.04
33/35
Revision history
Date
1-Sep-2003
1-Oct-2004
2-Jan-2005
2-Apr-2005
15-Nov- 2005
12-Dec-2006
Revision
4
4
1
2
5
6
Changes
Initial release.
Curves updated in the document.
Update mechanical data on flip-chip package.
Remove data on flip-chip package.
Mechanical data updated on DFN10 package.
Removed demo board views. Format update.
TS4994
34/35
TS4994
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