1W differential input/output audio power amplifier
Features
■ Differential inputs
■ Near-zero pop & click
■ 100dB PSRR @ 217Hz with grounded inputs
■ Operating range from V
■ 1W rail-to-rail output power @ V
THD = 1%, F = 1kHz, with 8Ω
■ 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 8Ω load @ 5V. Due to its differential input s,
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 de vice capable of sustain ing
short-circuits.
The device is equipped with common mode
feedback circuitry allowing outputs to be always
= 2.5V to 5.5V
CC
CC
load
=5V,
TS4994
with selectable standb y
Pin connections (top view)
TS4994IQT - DFN10
1
1
1
STBY
STBY
2
2
2
V
V
IN -
IN -
3
3
STBY MODE
STBY MODE
BYPASS
BYPASS
3
V
V
4
4
4
IN +
IN +
5
5
5
TS4994IST - MiniSO-8
STBY
biased at V
STBY
BYPASS
BYPASS
/2 regardless of the input common
CC
1
1
V
V
IN-
IN-
2
2
V
V
IN+
IN+
3
3
4
4
mode voltage.
The TS4994 is designed for high quality audio
applications such as mobile phones and requir es
few external components.
Applications
■ Mobile phones (cellular / cordless)
■ Laptop / notebook computers
■ PDAs
■ Portable audio devices
10
10
10
V
V
O+
O+
V
V
9
9
9
DD
DD
N/C
N/C
8
8
8
GND
GND
7
7
7
6
6
6
V
V
O-
O-
V
V
O+
O+
8
8
Vcc
Vcc
7
7
GND
GND
6
6
V
V
5
5
O-
O-
Order codes
Part number Temperature range Package Packing Marking
TS4994IQT
-40°C to +85°C
TS4994IST MiniSO-8 K994
December 2006 Rev 6 1/35
DFN10
Tape & reel
K994
www.st.com
35
Contents TS4994
Contents
1 Application component information . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Absolute maximum ratings and operating conditions . . . . . . . . . . . . . 5
3 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.1 Differential configuration principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.2 Gain in typical application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.3 Common mode feedback loop limitations . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.4 Low and high frequency response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.5 Calculating the influence of mismatching on PSRR performance . . . . . . 23
4.6 CMRR performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.7 Power dissipation and efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.8 Decoupling of the circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.9 Wake-up time: t
4.10 Shutdown time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.11 Pop performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.12 Single-ended input configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.13 Demoboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
WU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
5 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.1 DFN10 package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.2 MiniSO-8 package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
6 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2/35
TS4994 Application component information
1 Application component information
Components Functional description
C
s
C
b
R
feed
R
in
C
in
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 Rin
AV= closed loop gain = R
feed/Rin
.
Inverting input resistor that sets the closed loop gain in conjunction with R
Optional input capacitor making a high pass filter together with Rin.
(FCL= 1/(2πRinCin).
Figure 1. Typical application, DFN10 version
Rfeed1
20k
Diff. input -
GND
Diff. Input +
Cin1
220nF
Cin2
220nF
Optional
Rin1
+
20k
Rin2
+
20k
+
Cb
1u
GND
Vin-
2
Vin+
4
Bypass
5
Mode Stdby TS4994IQ
1
VCC
9
VCC
-
+
Bias
Standby
GND
73
GND
+
GND
Rfeed2
20k
Cs
1u
Vo+
Vo-
.
feed
10
6
8 Ohms
GND GNDVCC VCC
3/35
Application component information TS4994
Figure 2. Typical application, MiniSO-8 version
VCC
+
Cs
GND
Rfeed2
20k
1u
Vo+
8
Vo-
5
8 Ohms
TS4994IS
Diff. input -
GND
Diff. Input +
Cin1
220nF
Cin2
220nF
Optional
Rfeed1
20k
Rin1
+
20k
Rin2
+
20k
+
Cb
1u
GND
2
3
4
Vin-
Vin+
Bypass
Stdby
1
7
VCC
-
+
Bias
Standby
GND
6
GND
GNDVCC
4/35
TS4994 Absolute maximum ratings and operating conditions
2 Absolute maximum ratings and operating conditions
Table 1. Absolute maximum ratings
Symbol Parameter Value Unit
(2)
(1)
(3)
6V
GND to V
CC
120
215
V
T
T
R
P
CC
V
oper
stg
T
thja
diss
Supply voltage
Input voltage
i
Operating free air tempe rature range -40 to + 85 °C
Storage temperature -65 to +150 °C
Maximum junction temperature 150 °C
j
Thermal resistance junction to ambient
DFN10
MiniSO-8
Power dissipation internally limited W
Human body model 2 kV
ESD
Machine model 200 V
Latch-up immunity 200 mA
Lead temperature (soldering, 10sec) 260 °C
1. All voltage values are measured with respect to the ground pin.
2. The magnitude of the input signal must never exceed V
3. The device is protected by a thermal shutdown active at 150°C.
Table 2. Operating conditions
+ 0.3V / GND - 0.3V.
CC
V
°C/W
Symbol Parameter Value Unit
V
CC
Supply voltage 2.5 to 5.5 V
Standby mode voltage input:
V
SM
Standby active LOW
Standby active HIGH
=GND
V
SM
V
SM=VCC
Standby voltage input:
V
T
STBY
SD
R
L
Device ON (VSM= GND) or device OFF (VSM=VCC)
Device OFF (V
= GND) or device ON (VSM=VCC)
SM
Thermal shutdown temperature 150 °C
Load resistor ≥ 8 Ω
1.5 ≤ V
≤ V
GND
STBY
STBY
≤ VCC
≤ 0.4
(1)
Thermal resistance junction to ambient
R
thja
DFN10
MiniSO-8
1. The minimum current consumption (I
temperature range.
2. When mounted on a 4-layer PCB.
(2)
) is guaranteed when V
STBY
80
190
=GND or VCC (i.e. supply rails) for the whole
STBY
V
V
°C/W
5/35
Electrical characteristics TS4994
3 Electrical characteristics
Table 3. Electrical characteristics for VCC = +5V, GND = 0V, T
= 25°C (unless otherwise
amb
specified)
Symbol Parameter Min. Typ. Max. Unit
I
CC
I
STBY
V
oo
V
ICM
P
out
THD + N
PSRR
CMRR
SNR
Supply current
No input signal, no load
Standby current
No input signal, V
No input signal, V
= VSM = GND, RL = 8Ω
STBY
= VSM = VCC, RL = 8Ω
STBY
Differential output offset voltage
No input signal, RL = 8Ω
Input common mode voltage
CMRR ≤ -60dB
Output power
THD = 1% Max, F= 1kHz, RL = 8Ω
Total harmonic distortion + noise
=850mW rms, AV=1, 20Hz ≤ F ≤ 20kHz, RL=8Ω
P
out
Power supply rejection ratio with inputs grounded
F = 217Hz, R = 8Ω, AV = 1, Cin = 4.7μF, Cb =1μF
IG
V
ripple
= 200mV
PP
Common mode rejection ratio
F = 217Hz, R
= 200mV
V
ic
= 8Ω, AV = 1, Cin = 4.7μF, Cb =1μF
L
PP
Signal-to-noise ratio (A-weighted filter, A
RL = 8Ω, THD +N < 0.7%, 20Hz ≤ F ≤ 20kHz
= 2.5)
V
(1)
47mA
10 1000 nA
0.1 10 mV
0.6 V
-0.9 V
CC
0.8 1 W
0.5 %
100 dB
90 dB
100 dB
GBP
Gain bandwidth product
R
= 8Ω
L
Output voltage noise, 20Hz ≤ F ≤ 20kHz, RL = 8Ω
Unweighted, A
A-weighted, A
Unweighted, A
V
N
A-weighted, A
Unweighted, A
A-weighted, A
= 1
V
= 1
V
= 2.5
V
= 2.5
V
= 7.5
V
= 7.5
V
Unweighted, Standby
A-weighted, Standby
t
WU
1. Dynamic measurements - 20*log(rms(V
2. Transition time from standby mode to fully operational amplifier.
Wake-up time
Cb =1μF
(2)
)/rms (V
out
ripple
)). V
ripple
6/35
2MHz
6
5.5
12
10.5
33
28
1.5
1
15 ms
is the super-imposed sinus signal relative to VCC.
μV
RMS
TS4994 Electrical characteristics
Table 4. Electrical characteristics for VCC = +3.3V (all electrical values are guaranteed with
correlation measurements at 2.6V and 5V), GND = 0V, T
= 25°C (unless otherwise
amb
specified)
Symbol Parameter Min. Typ. Max. Unit
I
CC
I
STBY
V
oo
V
ICM
P
out
THD + N
PSRR
CMRR
SNR
Supply current no input signal, no load 3 7 mA
Standby current
No input signal, V
No input signal, V
= VSM = GND, RL = 8Ω
STBY
= VSM = VCC, RL = 8Ω
STBY
Differential output offset voltage
No input signal, RL = 8Ω
Input common mode voltage
CMRR ≤ -60dB
Output power
THD = 1% max, F= 1kHz, R
= 8Ω
L
Total harmonic distortion + noise
= 300mW rms, AV = 1, 20Hz ≤ F ≤ 20kHz, RL = 8Ω
P
out
Power supply rejection ratio with inputs grounded
F = 217Hz, R = 8Ω, AV = 1, Cin = 4.7μF, Cb =1μF
IG
V
ripple
= 200mV
PP
0.6 V
300 380 mW
(1)
10 1000 nA
0.1 10 mV
-0.9 V
CC
0.5 %
100 dB
Common mode rejection ratio
F = 217Hz, R
= 200mV
V
ic
Signal-to-noise ratio (A-weighted filter, A
RL = 8Ω, THD +N < 0.7%, 20Hz ≤ F ≤ 20kHz
= 8Ω, AV = 1, Cin = 4.7μF, Cb =1μF
L
PP
= 2.5)
V
90 dB
100 dB
GBP
Gain bandwidth product
R
= 8Ω
L
Output voltage noise, 20Hz ≤ F ≤ 20kHz, RL = 8Ω
Unweighted, A
V
= 1
A-weighted, AV = 1
V
N
A-weighted, A
Unweighted, A
A-weighted, A
Unweighted, A
= 2.5
V
= 2.5
V
= 7.5
V
= 7.5
V
Unweighted, Standby
A-weighted, Standby
t
WU
1. Dynamic measurements - 20*log(rms(V
2. Transition time from standby mode to fully operational amplifier.
Wake-up time
Cb =1μF
(2)
)/rms (V
out
ripple
)). V
ripple
2MHz
6
5.5
12
10.5
33
28
1.5
1
15 ms
is the super-imposed sinus signal relative to VCC.
μV
RMS
7/35
Electrical characteristics TS4994
Table 5. Electrical characteristics for VCC = +2.6V, GND = 0V, T
= 25°C (unless otherwise
amb
specified)
Symbol Parameter Min. Typ. Max. Unit
I
CC
I
STBY
V
V
ICM
P
out
THD + N
PSRR
CMRR
SNR
GBP
V
t
WU
Supply current
No input signal, no load
Standby current
No input signal, V
No input signal, V
Differential output offset voltage
oo
No input signal, R
= VSM = GND, RL = 8Ω
STBY
= VSM = VCC, RL = 8Ω
STBY
= 8Ω
L
Input common mode voltage
CMRR ≤ -60dB
Output power
THD = 1% max, F= 1kHz, RL = 8Ω
Total harmonic distortion + noise
= 225mW rms, AV = 1, 20Hz ≤ F ≤ 20kHz, RL = 8Ω
P
out
Power supply rejection ratio with inputs grounded
F = 217Hz, R = 8Ω, AV = 1, Cin = 4.7μF, Cb =1μF
IG
V
= 200mV
ripple
PP
Common mode rejection ratio
F = 217Hz, R
Vic = 200mV
= 8Ω, AV = 1, Cin = 4.7μF, Cb =1μF
L
PP
Signal-to-noise ratio (A-weighted filter, A
= 8Ω, THD +N < 0.7%, 20Hz ≤ F ≤ 20kHz
R
L
Gain bandwidth product
= 8Ω
R
L
Output voltage noise, 20Hz ≤ F ≤ 20kHz, RL = 8Ω
Unweighted, AV = 1
A-weighted, A
V
= 1
Unweighted, AV = 2.5
N
A-weighted, A
Unweighted, A
A-weighted, A
= 2.5
V
= 7.5
V
= 7.5
V
Unweighted, Standby
A-weighted, Standby
Wake-up time
(2)
Cb =1μF
= 2.5)
V
(1)
37mA
10 1000 nA
0.1 10 mV
0.6 V
- 0.9 V
CC
200 250 mW
0.5 %
100 dB
90 dB
100 dB
2MHz
6
5.5
12
10.5
33
28
1.5
1
15 ms
μV
RMS
1. Dynamic measurements - 20*log(rms(V
2. Transition time from standby mode to fully operational amplifier.
)/rms (V
out
ripple
)). V
ripple
8/35
is the super-imposed sinus signal relative to VCC.
TS4994 Electrical characteristics
012345
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Standby mode=0V
Standby mode=5V
Vcc = 5V
No load
Tamb=25°C
Current Consumption (mA)
Standby Voltage (V)
0.0 0.6 1.2 1.8 2.4
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Standby mode=0V
Standby mode=2.6V
Vcc = 2.6V
No load
Tamb=25°C
Current Consumption (mA)
Standby Voltage (V)
Figure 3. Current consumption vs. power
supply voltage
4.0
No load
Tamb=25°C
3.5
3.0
2.5
2.0
1.5
1.0
Current Consumption (mA)
0.5
0.0
012345
Power Supply Voltage (V)
Figure 5. Current consumption vs. power
supply voltage
3.5
3.0
2.5
Standby mode=0V
Figure 4. Current consumption vs. standby
voltage
Figure 6. Current consumption vs. standby
voltage
2.0
1.5
1.0
Current Consumption (mA)
0.5
0.0
0.0 0.6 1.2 1.8 2.4 3.0
Standby mode=3.3V
Standby Voltage (V)
Figure 7. Differential DC output voltage vs.
common mode input voltage
1000
Av = 1
Tamb = 25°C
100
Vcc=2.5V
10
Voo (mV)
1
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)
Vcc = 3.3V
No load
Tamb=25°C
Vcc=3.3V
Vcc=5V
Figure 8. Power dissipation vs. output power
0.6
RL=8
Ω
0.4
0.2
Power Dissipation (W)
0.0
0.0 0.2 0.4 0.6 0.8 1.0
9/35
RL=16
Ω
Output Power (W)
Vcc=5V
F=1kHz
THD+N<1%
Electrical characteristics TS4994
Figure 9. Power dissipation vs. output powe r Figure 10. Power dissipation vs. output power
0.3
RL=8
Ω
0.2
0.1
Power Dissipation (W)
RL=16
Ω
Vcc=3.3V
F=1kHz
0.0
0.0 0.1 0.2 0.3 0.4
THD+N<1%
Output Power (W)
Figure 11. Output power vs. power supply
voltage
1.0
Cb = 1μF
F = 1kHz
0.8
BW < 125kHz
Tamb = 25°C
0.6
0.4
8
Ω
16
Ω
0.20
Vcc=2.6V
F=1kHz
THD+N<1%
0.15
RL=8
Ω
0.10
0.05
Power Dissipation (W)
0.00
0.0 0.1 0.2 0.3
RL=16
Ω
Output Power (W)
Figure 12. Output power vs. power supply
voltage
1.50
1.25
1.00
0.75
0.50
Cb = 1μF
F = 1kHz
BW < 125kHz
Tamb = 25°C
8
Ω
16
Ω
0.2
32
Output power @ 1% THD + N (W)
0.0
2.5 3.0 3.5 4.0 4.5 5.0
Ω
Vcc (V)
0.25
Output power @ 10% THD + N (W)
0.00
2.5 3.0 3.5 4.0 4.5 5.0
Vcc (V)
Figure 13. Output power vs. load resistance Figure 14. Power derating curves
1.0
THD+N=1%
Cb = 1 F
0.8
0.6
Vcc=5V
Vcc=4.5V
Vcc=4V
F = 1kHz
BW < 125kHz
Tamb = 25°C
0.4
Output power (W)
0.2
Vcc=3.5V
0.0
88121616 20 2424 28 3232
Vcc=3V
Vcc=2.5V
Load Resistance
1.5
with 4 layers PCB
1.0
0.5
AMR Value
DFN10 Package Power Dissipation (W)
0.0
0 25 50 75 100 125
Ambiant Temperature ( C)
32
Ω
10/35
TS4994 Electrical characteristics
0.1 1 10 100 1000 10000
-40
-20
0
20
40
60
-200
-160
-120
-80
-40
0
Gain
Phase
Gain (dB)
Frequency (kHz)
Vcc = 5V
ZL = 8Ω + 500pF
Tamb = 25°C
Phase (°)
Figure 15. Power derating curves Figure 16. Open loop gain vs. frequency
0.6
Nominal Value
0.4
0.2
MiniSO8 Package Power Dissipation (W)
0.0
AMR Value
0 25 50 75 100 125
Ambiant Temperature ( C)
Figure 17. Open loop gain vs. frequency Figure 18. Open loop gain vs. frequency
0
60
Gain
40
20
Gain (dB)
0
Phase
-40
-80
-120
Phase (°)
60
Gain
40
20
Gain (dB)
0
Phase
0
-40
-80
-120
Phase (°)
Vcc = 3.3V
-20
ZL = 8Ω + 500pF
Tamb = 25°C
-40
0.1 1 10 100 1000 10000
Frequency (kHz)
-160
-200
Vcc = 2.6V
-20
ZL = 8Ω + 500pF
Tamb = 25°C
-40
0.1 1 10 100 1000 10000
Frequency (kHz)
-160
-200
Figure 19. Closed loop gain vs. frequency Figure 20. Closed loop gain vs. frequency
10
Gain
0
-10
-20
Gain (dB)
Vcc = 5V
-30
Av = 1
ZL = 8Ω + 500pF
Tamb = 25°C
-40
0.1 1 10 100 1000 10000
Frequency (kHz)
Phase
0
-40
-80
-120
-160
-200
10
Gain
0
-10
Phase (°)
-20
Gain (dB)
Vcc = 3.3V
-30
Av = 1
ZL = 8Ω + 500pF
Tamb = 25°C
-40
0.1 1 10 100 1000 10000
Frequency (kHz)
Phase
11/35
0
-40
-80
-120
-160
-200
Phase (°)
Electrical characteristics TS4994
100 1000 10000
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
Cb=0.1μF
Cb=1μF
Cb=0
20k
20
Cb=0.47μF
Vcc = 3.3V
Vripple = 200mVpp
Inputs = Grounded
Av = 2.5, Cin = 4.7μF
RL ≥ 8Ω
Tamb = 25°C
PSRR (dB)
Frequency (Hz)
Figure 21. Closed loop gain vs. frequency Figure 22. PSRR vs. frequency
PSRR (dB)
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
0
20
Vcc = 5V
Vripple = 200mVpp
Inputs = Grounded
Av = 1, Cin = 4.7μF
RL ≥ 8Ω
Tamb = 25°C
100 1000 10000
Cb=0.47μF
Cb=1μF
Frequency (Hz)
10
Gain
0
-10
-20
Gain (dB)
Vcc = 2.6V
-30
Av = 1
ZL = 8Ω + 500pF
Tamb = 25°C
-40
0.1 1 10 100 1000 10000
Frequency (kHz)
Phase
0
-40
-80
-120
-160
-200
Phase (°)
Figure 23. PSRR vs. frequency Figure 24. PSRR vs. frequency
PSRR (dB)
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
0
20
Vcc = 2.6V
Vripple = 200mVpp
Inputs = Grounded
Av = 1, Cin = 4.7μF
RL ≥ 8Ω
Tamb = 25°C
100 1000 10000
Cb=0.47μF
Cb=1μF
Frequency (Hz)
0
-10
Vcc = 3.3V
Vripple = 200mVpp
-20
Inputs = Grounded
-30
Av = 1, Cin = 4.7μF
-40
RL ≥ 8Ω
-50
Tamb = 25°C
-60
-70
PSRR (dB)
-80
-90
-100
-110
-120
20
Cb=0.1μF
Cb=0.47μF
Cb=1μF
Cb=0
100 1000 10000
Frequency (Hz)
20k
Cb=0.1μF
Cb=0
20k
Cb=0.1μF
Cb=0
20k
Figure 25. PSRR vs. frequency Figure 26. PSRR vs. frequency
0
-10
Vcc = 5V
Vripple = 200mVpp
-20
Inputs = Grounded
-30
Av = 2.5, Cin = 4.7μF
-40
RL ≥ 8Ω
-50
Tamb = 25°C
-60
-70
PSRR (dB)
-80
Cb=1μF
-90
-100
-110
-120
20
100 1000 10000
Frequency (Hz)
12/35
Cb=0.1μF
Cb=0.47μF
Cb=0
20k
TS4994 Electrical characteristics
100 1000 10000
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
Cb=0.1μF
Cb=1μF
Cb=0
20k
20
Cb=0.47μF
Vcc = 5V
Vripple = 200mVpp
Inputs = Floating
Rfeed = 20kΩ
RL ≥ 8Ω
Tamb = 25°C
PSRR (dB)
Frequency (Hz)
100 1000 10000
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
Cb=0.1μF
Cb=1μF
Cb=0
20k
20
Cb=0.47μF
Vcc = 2.6V
Vripple = 200mVpp
Inputs = Floating
Rfeed = 20kΩ
RL ≥ 8Ω
Tamb = 25°C
PSRR (dB)
Frequency (Hz)
0.0 0.6 1.2 1.8 2.4 3.0
-100
-80
-60
-40
-20
0
Cb=1μF
Cb=0.47μF
Cb=0.1μF
Cb=0
Vcc = 3.3V
Vripple = 200mVpp
Inputs Grounded
F = 217Hz
Av = 1
RL ≥ 8
Ω
Tamb = 25°C
PSRR(dB)
Common Mode Input Voltage (V)
Figure 27. PSRR vs. frequency Figure 28. PSRR vs. frequency
0
-10
Vcc = 2.6V
-20
Vripple = 200mVpp
Inputs = Grounded
-30
Av = 2.5, Cin = 4.7μF
-40
PSRR (dB)
-100
-110
-120
-50
-60
-70
-80
-90
RL ≥ 8Ω
Tamb = 25°C
20
Cb=1μF
100 1000 10000
Frequency (Hz)
Cb=0.1μF
Cb=0.47μF
Cb=0
20k
Figure 29. PSRR vs. frequency Figure 30. PSRR vs. frequency
0
-10
Vcc = 3.3V
Vripple = 200mVpp
-20
Inputs = Floating
-30
Rfeed = 20kΩ
-40
PSRR (dB)
-100
-110
-120
-50
-60
-70
-80
-90
RL ≥ 8Ω
Tamb = 25°C
20
Cb=0.47μF
Cb=1μF
100 1000 10000
Frequency (Hz)
Cb=0.1μF
Cb=0
20k
Figure 31. PSRR vs. common mode input
voltage
0
Vcc = 5V
Vripple = 200mVpp
-20
Inputs Grounded
F = 217Hz
Av = 1
-40
RL ≥ 8
Ω
Tamb = 25°C
-60
PSRR(dB)
-80
-100
012345
Cb=0
Common Mode Input Voltage (V)
Cb=1μF
Cb=0.47μF
Cb=0.1μF
Figure 32. PSRR vs. common mode input
voltage
13/35
Electrical characteristics TS4994
100 1000 10000
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
Cb=1μF
Cb=0.47μF
Cb=0.1μF
Cb=0
20k
20
Vcc = 5V
Vic = 200mVpp
Av = 1, Cin = 470μF
RL ≥ 8
Ω
Tamb = 25°C
CMRR (dB)
Frequency (Hz)
100 1000 10000
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
Cb=1μF
Cb=0.47μF
Cb=0.1μF
Cb=0
20k
20
Vcc = 2.6V
Vic = 200mVpp
Av = 1, Cin = 470μF
RL ≥ 8
Ω
Tamb = 25°C
CMRR (dB)
Frequency (Hz)
100 1000 10000
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
Cb=1μF
Cb=0.47μF
Cb=0.1μF
Cb=0
20k
20
Vcc = 3.3V
Vic = 200mVpp
Av = 2.5, Cin = 470μF
RL ≥ 8
Ω
Tamb = 25°C
CMRR (dB)
Frequency (Hz)
Figure 33. PSRR vs. common mode input
Figure 34. CMRR vs. frequency
voltage
0
Vcc = 2.5V
Vripple = 200mVpp
Inputs Grounded
-20
F = 217Hz
Av = 1
-40
RL ≥ 8
Ω
Tamb = 25°C
-60
PSRR(dB)
-80
-100
0.0 0.5 1.0 1.5 2.0 2.5
Common Mode Input Voltage (V)
Cb=0
Cb=1μF
Cb=0.47μF
Cb=0.1μF
Figure 35. CMRR vs. frequency Figure 36. CMRR vs. frequency
0
-10
Vcc = 3.3V
Vic = 200mVpp
-20
Av = 1, Cin = 470μF
-30
RL ≥ 8
CMRR (dB)
-100
-110
-120
-40
-50
-60
-70
-80
-90
Tamb = 25°C
20
Ω
100 1000 10000
Cb=1μF
Cb=0.47μF
Cb=0.1μF
Cb=0
20k
Frequency (Hz)
Figure 37. CMRR vs. frequency Figure 38. CMRR vs. frequency
0
Vcc = 5V
-10
Vic = 200mVpp
-20
Av = 2.5, Cin = 470μF
RL ≥ 8
-30
-40
-50
-60
CMRR (dB)
-70
-80
-90
-100
14/35
Ω
Tamb = 25°C
20
Cb=1μF
Cb=0.47μF
Cb=0.1μF
Cb=0
100 1000 10000
Frequency (Hz)
20k
TS4994 Electrical characteristics
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
-100
-80
-60
-40
-20
0
Vcc=3.3V
Vcc=2.5V
Vcc=5V
Vic = 200mVpp
F = 217Hz
Av = 1, Cb = 1μF
RL ≥ 8
Ω
Tamb = 25°C
CMRR(dB)
Common Mode Input Voltage (V)
1E-3 0.01 0.1 1
1E-3
0.01
0.1
1
10
Vcc=5V
Vcc=3.3V
Vcc=2.6V
RL = 8
Ω
F = 20Hz
Av = 1
Cb = 1μF
BW < 125kHz
Tamb = 25°C
THD + N (%)
Output Power (W)
Figure 39. CMRR vs. frequency Figure 40. CMRR vs. common mode input
voltage
0
Vcc = 2.6V
-10
Vic = 200mVpp
-20
Av = 2.5, Cin = 470μF
RL ≥ 8Ω
-30
Tamb = 25°C
-40
-50
-60
CMRR (dB)
-70
-80
-90
-100
20
100 1000 10000
Figure 41. CMRR vs. common mode input
Cb=1μF
Cb=0.47μF
Cb=0.1μF
Cb=0
Frequency (Hz)
20k
Figure 42. THD+N vs. output power
voltage
-20
0
Vcc=2.5V
Vcc=3.3V
-40
-60
CMRR(dB)
-80
-100
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)
Vcc=5V
Vic = 200mVpp
F = 217Hz
Av = 1, Cb = 0
RL ≥ 8
Ω
Tamb = 25°C
Figure 43. THD+N vs. output power Figure 44. THD+N vs. output power
10
RL = 8
Ω
1
THD + N (%)
0.1
F = 20Hz
Av = 7.5
Cb = 1μF
BW < 125kHz
Tamb = 25°C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.01
1E-3 0.01 0.1 1
Output Power (W)
15/35
10
RL = 8
Ω
F = 20Hz
Av = 2.5
1
Cb = 1μF
BW < 125kHz
Tamb = 25°C
0.1
THD + N (%)
0.01
1E-3
1E-3 0.01 0.1 1
Output Power (W)
Vcc=2.6V
Vcc=3.3V
Vcc=5V
Electrical characteristics TS4994
1E-3 0.01 0.1 1
0.01
0.1
1
10
Vcc=5V
Vcc=3.3V
Vcc=2.6V
RL = 8
Ω
F = 1kHz
Av = 2.5
Cb = 1μF
BW < 125kHz
Tamb = 25°C
THD + N (%)
Output Power (W)
1E-3 0.01 0.1 1
0.1
1
10
Vcc=5V
Vcc=3.3V
Vcc=2.6V
RL = 8
Ω
F = 20kHz
Av = 1
Cb = 1μF
BW < 125kHz
Tamb = 25°C
THD + N (%)
Output Power (W)
1E-3 0.01 0.1 1
0.1
1
10
Vcc=5V
Vcc=3.3V
Vcc=2.6V
RL = 8
Ω
F = 20kHz
Av = 7.5
Cb = 1μF
BW < 125kHz
Tamb = 25°C
THD + N (%)
Output Power (W)
Figure 45. THD+N vs. output power Figure 46. THD+N vs. output power
10
RL = 8
Ω
F = 1kHz
1
THD + N (%)
0.1
Av = 1
Cb = 1μF
BW < 125kHz
Tamb = 25°C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.01
1E-3 0.01 0.1 1
Output Power (W)
Figure 47. THD+N vs. output power Figure 48. THD+N vs. output power
10
RL = 8
F = 1kHz
Av = 7.5
Cb = 1μF
1
BW < 125kHz
Tamb = 25°C
Ω
Vcc=2.6V
Vcc=3.3V
Vcc=5V
THD + N (%)
0.1
0.01
1E-3 0.01 0.1 1
Output Power (W)
Figure 49. THD+N vs. output power Figure 50. THD+N vs. output power
10
RL = 8
Ω
F = 20kHz
Av = 2.5
Cb = 1μF
BW < 125kHz
1
Tamb = 25°C
THD + N (%)
0.1
1E-3 0.01 0.1 1
Output Power (W)
16/35
Vcc=2.6V
Vcc=3.3V
Vcc=5V
TS4994 Electrical characteristics
1E-3 0.01 0.1 1
0.01
0.1
1
10
Vcc=5V
Vcc=3.3V
Vcc=2.6V
RL = 16
Ω
F = 1kHz
Av = 7.5
Cb = 1μF
BW < 125kHz
Tamb = 25°C
THD + N (%)
Output Power (W)
1E-3 0.01 0.1 1
0.1
1
10
Vcc=5V
Vcc=3.3V
Vcc=2.6V
RL = 16Ω
F = 20kHz
Av = 7.5
Cb = 1μF
BW < 125kHz
Tamb = 25°C
THD + N (%)
Output Power (W)
Figure 51. THD+N vs. output power Figure 52. THD+N vs. output power
10
RL = 16
1
Ω
F = 20Hz
Av = 1
Cb = 1μF
Vcc=2.6V
Vcc=3.3V
BW < 125kHz
Tamb = 25°C
0.1
Vcc=5V
THD + N (%)
0.01
1E-3
1E-3 0.01 0.1 1
Output Power (W)
10
RL = 16
F = 20Hz
Av = 7.5
1
Cb = 1μF
Ω
Vcc=2.6V
Vcc=3.3V
BW < 125kHz
Tamb = 25°C
0.1
Vcc=5V
THD + N (%)
0.01
1E-3
1E-3 0.01 0.1 1
Output Power (W)
Figure 53. THD+N vs. output power Figure 54. THD+N vs. output power
10
RL = 16
1
0.1
THD + N (%)
Ω
F = 1kHz
Av = 1
Cb = 1μF
BW < 125kHz
Tamb = 25°C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.01
1E-3
1E-3 0.01 0.1 1
Output Power (W)
Figure 55. THD+N vs. output power Figure 56. THD+N vs. output power
10
RL = 16
Ω
F = 20kHz
Av = 1
Cb = 1μF
1
BW < 125kHz
Tamb = 25°C
THD + N (%)
0.1
0.01
1E-3 0.01 0.1 1
Output Power (W)
Vcc=2.6V
Vcc=3.3V
Vcc=5V
17/35
Electrical characteristics TS4994
1E-3 0.01 0.1
1E-3
0.01
0.1
1
10
F=20kHz
F=20Hz
F=1kHz
RL = 8
Ω
Vcc = 2.6V
Av = 1, Cb = 0
BW < 125kHz
Tamb = 25°C
THD + N (%)
Output Power (W)
1E-3 0.01 0.1
1E-3
0.01
0.1
1
10
F=20kHz
F=20Hz
F=1kHz
RL = 16
Ω
Vcc = 2.6V
Av = 1, Cb = 0
BW < 125kHz
Tamb = 25°C
THD + N (%)
Output Power (W)
100 1000 10000
1E-3
0.01
0.1
1
10
Vcc=2.6V, Po=225mW
Vcc=5V, Po=850mW
RL = 8
Ω
Av = 1
Cb = 0
Bw < 125kHz
Tamb = 25°C
20k20
THD + N (%)
Frequency (Hz)
Figure 57. THD+N vs. output power Figure 58. THD+N vs. output power
10
RL = 8
Ω
Vcc = 5V
Av = 1
1
Cb = 0
BW < 125kHz
Tamb = 25°C
0.1
THD + N (%)
F=20kHz
F=1kHz
F=20Hz
0.01
1E-3 0.01 0.1 1
Output Power (W)
Figure 59. THD+N vs. output power Figure 60. THD+N vs. output power
10
RL = 16
Ω
Vcc = 5V
Av = 1, Cb = 0
1
0.1
THD + N (%)
0.01
BW < 125kHz
Tamb = 25°C
F=20kHz
F=1kHz
F=20Hz
1E-3
1E-3 0.01 0.1 1
Figure 61. THD+N vs. frequency Figure 62. THD+N vs. frequency
10
RL = 8
Ω
Av = 1
Cb = 1μF
1
Bw < 125kHz
Tamb = 25°C
0.1
THD + N (%)
0.01
1E-3
18/35
100 1000 10000
Output Power (W)
Vcc=2.6V, Po=225mW
Vcc=5V, Po=850mW
20k20
Frequency (Hz)
TS4994 Electrical characteristics
100 1000 10000
1E-3
0.01
0.1
1
10
Vcc=2.6V, Po=155mW
Vcc=5V, Po=600mW
RL = 16
Ω
Av = 7.5
Cb = 1μF
Bw < 125kHz
Tamb = 25°C
20k20
THD + N (%)
Frequency (Hz)
2.5 3.0 3.5 4.0 4.5 5.0
80
85
90
95
100
105
110
Av = 2.5
Cb = 1μF
THD+N < 0.7%
Tamb = 25°C
RL=16
Ω
RL=8
Ω
Signal to Noise Ratio (dB)
Power Supply Voltage (V)
Figure 63. THD+N vs. frequency Figure 64. THD+N vs. frequency
THD + N (%)
0.01
10
0.1
RL = 8
Av = 7.5
Cb = 1μF
Bw < 125kHz
1
Tamb = 25°C
Ω
Vcc=2.6V, Po=225mW
Vcc=5V, Po=850mW
100 1000 10000
Frequency (Hz)
20k20
THD + N (%)
10
0.1
0.01
RL = 8
Av = 7.5
Cb = 0
Bw < 125kHz
1
Tamb = 25°C
Ω
Vcc=2.6V, Po=225mW
Vcc=5V, Po=850mW
100 1000 10000
Frequency (Hz)
Figure 65. THD+N vs. frequency Figure 66. THD+N vs. frequency
10
RL = 16
Ω
Av = 1
Cb = 1μF
1
Bw < 125kHz
Tamb = 25°C
Vcc=2.6V, Po=155mW
20k20
0.1
THD + N (%)
0.01
Vcc=5V, Po=600mW
1E-3
100 1000 10000
Frequency (Hz)
Figure 67. SNR vs. power supply voltage with
unweighted filter
110
RL=16
Ω
RL=8
105
100
95
90
Av = 2.5
Signal to Noise Ratio (dB)
Cb = 1μF
85
THD+N < 0.7%
Tamb = 25°C
80
2.5 3.0 3.5 4.0 4.5 5.0
Power Supply Voltage (V)
20k20
Figure 68. SNR vs. power supply voltage with
A-weighted filter
Ω
19/35
Electrical characteristics TS4994
Figure 69. Startup time vs. bypass capacitor
20
Tamb=25°C
15
10
Startup Time (ms)
5
0
0.0 0.4 0.8 1.2 1.6 2.0
Vcc=5V
Vcc=3.3V
Vcc=2.6V
Bypass Capacitor Cb ( F)
20/35
TS4994 Application information
4 Application information
4.1 Differential configuration principle
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
/2 for any DC common mode input voltage. This allows the device to always have a
CC
maximum output voltage swing, and by co nsequence, 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 . Bu t, 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.
4.2 Gain in typical application schematic
Typical differential applications are shown in Figure 1 and Figure 2 on page 4.
In the flat region of the frequency-response curve (no C
effect), the differential gain is
in
expressed by the relation:
R
feed
--------------==
R
where R
in
= R
in1
= R
and R
in2
Note: For the rest of this section, Av
V
–
O+VO
A
------------------------------------------------------
V
diff
Diff
input+
= R
feed
diff
feed1
will be called AV to simplify the expression.
= R
Diff
–
feed2
input-
.
4.3 Common mode feedback loop limitations
As explained pre viously, the common mode feedback loop allows the output DC bias voltage
to be averaged at V
However, due to V
mode feedback loop can play its role only within a defined rang e. This range depends upon
/2 for any DC common mode bias input voltage.
CC
limitation of the input stage (see Table 3 on page 6), the common
ICM
in
21/35
Application information TS4994
the values of VCC, Rin and R
(AV). To have a good estimation of the V
feed
following formula:
V
× 2VicR
CCRin
V
------------------------------------------------------------------------- -
ICM
2R
inRfeed
+()×
with
Diff
input+
------------------------------------------------------ -
V
ic
Diff
+
input-
2
The result of the calculation must be in the range:
If the result of the V
0.6V V
calculation is not in this range, an input coupling capacitor must be
ICM
ICMVCC
used.
Example: With V
=2.5V, Rin=R
CC
= 20k and Vic= 2V, we find V
feed
higher than 2.5V- 0.9V = 1.6V, so input coupling capacitors are required. Alternatively, you
can change the V
value.
ic
4.4 Low and high frequency response
In the low frequency region, Cin starts to have an effect. Cin forms, with Rin, a high-pass filter
with a -3dB cut-off frequency. F
is in Hz.
CL
F
CL
=
1
CR2
××π×
value, use the
ICM
××+
feed
(V)=
(V)=
0.9V–≤≤
= 1.63V. This is
ICM
)Hz(
inin
In the high-frequency region, you can limit the bandwidth by adding a capacitor (C
parallel with R
. It forms a low-pass filter with a -3dB cut-of f frequency. FCH is in Hz.
feed
=
F
CH
1
××π×
CR2
feedfeed
)Hz(
feed
) in
While these bandwidth limitations are in theory attractive, in practice, because of low
performance in terms of capacitor precision (and by consequen ce 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
and F
= 8kHz. We assume that the mismatching between R
CH
in1,2
and C
feed1,2
=50Hz
CL
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
C
impedance is high enough to be neglected. Due to the tolerance of C
feed
impedance decreases from infinite to a finite value and the
in
in1,2
, we
22/35
TS4994 Application information
must introduce a mismatch fa ctor (R
in1xCin
≠ R
in2xCin2
) that will decrease the PSRR
performance.
● From 200Hz to 5kHz, the C
compared with R
and the C
in,
impedance is low enough to be neglected when
in
impedance is high enough to be neglected as well. In
feed
this range, we can reach the PSRR performance of the TS4994 itself.
● From 5kHz to 20kHz, the C
and the C
impedance decreases to a finite value. Due to tolerance of C
feed
introduce a mismatching factor (R
impedance is low to be neglected when compared to R
in
feed1xCfeed1
≠ R
feed2xCfeed2
) that will decrease the
PSRR performance.
4.5 Calculating the influence of mismatching on PSRR performance
For calculating PSRR performance, we consider that Cin and C
We use the same kind of resistor (same tolerance) and ΔR is the tolerance value in %.
The following PSRR equation is valid for frequencies ranging from DC to about 1kHz.
The PSRR equation is (ΔR in %):
⎡
×≤
Log20PSRR
×Δ
⎢
⎣
⎤
100R
⎥
2
Δ−
)R10000(
⎦
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.
have no influence.
feed
)dB(
feed1,2
, we
in,
The complete PSRR equation (ΔR in %, C
PSRR 20 log ×≤
Example: With ΔR = 0.1% and C
--------------------------------------------------------------------------------------------------------(1000 R
= 0, the minimum PSRR would be -60dB. With a 100nF
b
in microFarad and F in Hz) is:
b
R 100×Δ
2
) 1F
2
2
C
b
dB()
22.2××+×Δ–
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 g raphs show PSRR v ersus frequency and v ersus b ypass capacitor Cb in
worst-case conditions (
Figure 70. PSRR vs. frequency (worst case
conditions)
Δ
R = 0.1%).
Figure 71. PSRR vs. frequency (worst case
conditions)
0
-10
Vcc = 5V, Vripple = 200mVpp
-20
Av = 1, Cin = 4.7μF
-30
Δ
R/R = 0.1%, RL ≥ 8
-40
Tamb = 25°C, Inputs = Grounded
-50
-60
-70
-80
PSRR (dB)
-90
-100
-110
-120
-130
-140
20
Cb=1μF
100 1000 10000
Ω
Cb=0
Cb=0.1μF
Cb=0.47μF
Frequency (Hz)
Figure 72. PSRR vs. frequency (worst case
conditions)
0
-10
Vcc = 2.5V, Vripple = 200mVpp
-20
Av = 1, Cin = 4.7μF
-30
ΔR/R = 0.1%, RL ≥ 8Ω
Tamb = 25°C, Inputs = Grounded
PSRR (dB)
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
Cb=0.1μF
Cb=1μF
20
100 1000 10000
Cb=0.47μF
Frequency (Hz)
Cb=0
20k
20k
0
-10
Vcc = 3.3V, Vripple = 200mVpp
-20
Av = 1, Cin = 4.7μF
-30
Δ
R/R = 0.1%, RL ≥ 8
Tamb = 25°C, Inputs = Grounded
-40
-50
-60
-70
-80
PSRR (dB)
-90
-100
-110
-120
-130
-140
Cb=1μF
20
100 1000 10000
Ω
Cb=0.1μF
Cb=0.47μF
Frequency (Hz)
Cb=0
20k
24/35
TS4994 Application information
The two followin g graphs sho w typical applications of the TS4994 wit h 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
Vcc = 5V, Vripple = 200mVpp
Av = 1, Cin = 4.7μF
-20
Δ
PSRR (dB)
R/R ≤ 0.1%, RL ≥ 8
-30
Tamb = 25°C, Inputs = Grounded
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
20
Cb=1μF
100 1000 10000
Ω
Cb=0.1μF
Cb=0.47μF
Frequency (Hz)
Cb=0
4.6 CMRR performance
For calculating CMRR performance, we consider that Cin and C
has no influence in the calculation of the CMRR.
We use the same kind of resistor (same tolerance) and ΔR is the tolerance value in %.
The following CMRR equation is valid for frequencies ranging from DC to about 1kHz.
The CMRR equation is (ΔR in %):
20k
0
-10
Vcc = 2.5V, Vripple = 200mVpp
Av = 1, Cin = 4.7μF
-20
Δ
R/R ≤ 0.1%, RL ≥ 8
-30
Tamb = 25°C, Inputs = Grounded
-40
-50
-60
-70
-80
PSRR (dB)
-90
-100
-110
-120
-130
-140
20
⎡
Log20CMRR
×≤
⎢
⎣
Cb=1μF
100 1000 10000
200R
×Δ
2
)R10000(
Δ−
Cb=0.1μF
⎤
⎥
⎦
Ω
Cb=0
Cb=0.47μF
Frequency (Hz)
have no influence. Cb
feed
)dB(
20k
Example: With ΔR = 1%, the minimum CMRR is -34dB.
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.
Figure 75 and Figure 76 show CMRR versus frequency and versus bypass capacitor C
worst-case conditions (ΔR=0.1%).
25/35
b
in
Application information TS4994
Figure 75. CMR vs. frequency (worst case
conditions)
0
Vcc = 5V
Vic = 200mVpp
-10
Av = 1, Cin = 470μF
Δ
-20
-30
CMRR (dB)
-40
-50
-60
Tamb = 25°C
20
R/R = 0.1%, RL ≥ 8
100 1000 10000
Ω
Cb=1μF
Cb=0
Frequency (Hz)
Figure 77 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
0
Vcc = 5V
-10
Vic = 200mVpp
-20
Av = 1, Cin = 470μF
Δ
-30
-40
-50
CMRR (dB)
-60
-70
-80
-90
Tamb = 25°C
20
R/R ≤ 0.1%, RL ≥ 8
100 1000 10000
Ω
Cb=1μF
Cb=0
Frequency (Hz)
Figure 76. CMR vs. frequency (worst case
conditions)
0
Vcc = 2.5V
Vic = 200mVpp
-10
Av = 1, Cin = 470μF
Δ
20k
-20
-30
CMRR (dB)
-40
-50
-60
Tamb = 25°C
20
R/R = 0.1%, RL ≥ 8
100 1000 10000
Ω
Cb=1μF
Cb=0
Frequency (Hz)
Figure 78. CMR vs. frequency with random
choice condition
0
Vcc = 2.5V
-10
Vic = 200mVpp
Av = 1, Cin = 470μF
-20
Δ
20k
-30
-40
-50
CMRR (dB)
-60
-70
-80
-90
20
R/R ≤ 0.1%, RL ≥ 8
Tamb = 25°C
100 1000 10000
Ω
Cb=1μF
Cb=0
Frequency (Hz)
20k
20k
4.7 Power dissipation and efficiency
Assumptions:
● Load voltage and current are sinusoidal (V
● Supply voltage is a pure DC source (V
The output voltage is:
V
out
and
26/35
I
= V
out
CC
=
out
)
peak
V
out
------------ -
R
and I
sinωt (V)
(A)
L
out
)
TS4994 Application information
and
2
V
peak
-------------------- -
P
out
=
2R
(W)
L
Therefore, the average current delivered by the supply voltag e is:
Equation 1
V
peak
---------------- -
AVG
= 2
I
CC
πR
(A)
L
The power delivered by the supply voltage is:
P
supply
V
CCICC
AVG
(W)⋅=
Therefore, the power dissipated by each amplifier is:
P
dissPsupplyPout
(W)–=
Equation 2
P
diss
----------------------
π R
L
–=
P
outPout
22V
CC
and the maximum value is obtained when:
∂P
diss
----------------- = 0
∂P
out
and its value is:
Equation 3
2
maxPdiss
Vcc2
=
π
)W(
2
R
L
Note: 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
P
-------------------
η =
P
supply
The maximum theoretical value is reached when V
η =
out
π
---- -
= 78.5%
4
πV
--------------------
=
PEAK
peak
4V
CC
= VCC, so:
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 TS4994
To calculate the maximum ambient temperature T
● The value of the power supply voltage, V
● The value of the load resistor, R
● The R
Example: V
value f or the package type
thja
=5V, RL=8Ω, R
CC
thja
Using the power dissipation formula given above in Equation 3 this gives a result of:
P
T
is calculated as follows:
amb
dissmax
= 633mW
Equation 5
T
amb
Therefore, the maximum allowable value for T
T
= 125-80x0.633=74°C
amb
4.8 Decoupling of the circuit
Two capacitors are needed to correctly bypass the TS4994. A power supply bypass
capacitor C
C
has particular influence on the THD+N in the high frequency region (abov e 7kHz) and an
s
indirect influence on power supply disturbances. With a value for C
similar THD+N performance to that shown in the datasheet.
and a bias voltage bypass capacitor Cb.
s
L
= 80°C/W
125° CR
allowable, you need to know:
amb
CC
×–=
TJHAPdissmax
is:
amb
of 1µF, you can expect
s
In the high frequency region, if C
on the power supply rail are less filtered.
On the other hand, if C
more filtered.
C
has an influence on THD+N at lower frequencies, but its function is critical to the final
b
result of PSRR (with input grounded and in the lower frequency region).
4.9 Wake-up time: t
When the standby is released to put the device ON, the bypass capa cit or Cb is not charged
immediately. As C
properly until the C
time or t
and is specified in Table 3 on page 6, with Cb=1µF. During the wake-up time, the
WU
TS4994 gain is close to zero. After the wake-up time, the gain is released and set to its
nominal value.
If C
has a value other than 1µF, refer to the graph in Figure 69 on page 20 to establish the
b
wake-up time.
is directly linked to the bias of the amplifier, the bias will not work
b
voltage is correct. The time to reach this voltage is called the wake-up
b
is lower than 1µF, it increases THD+N, and disturbances
s
is higher than 1µF, the disturbances on the power supply rail are
s
WU
28/35
TS4994 Application information
4.10 Shutdown time
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 micr oseconds.
Note: 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
and Cin capacitors.
b
4.11 Pop performance
Due to its fully differential structure, the pop performance of the TS4994 is close to perfect.
However, due to mismatching between internal resistors R
capacitors C
, some noise might remain at startup. To eliminate the effect of mismatched
in
, R
in
, and external input
feed
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 standb y mode, due to the h igh 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 schema tic in Figure 79 shows this
configuration using the MiniSO-8 version of the TS4994 as an example.
Figure 79. Single-ended input typical application
VCC
+
Cs
GND
Rfeed2
20k
1u
Vo+
8
Vo-
5
8 Ohms
TS4994IS
Ve
GND
Cin1
220nF
Cin2
220nF
Optional
Rfeed1
20k
Rin1
+
20k
Rin2
+
20k
+
Cb
1u
GND
2
3
4
Vin-
Vin+
Bypass
Stdby
1
7
VCC
-
+
Bias
Standby
GND
6
GND
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:
R
=
Av =
SE
VV
Ve
feedOO
−+
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 Package mechanical data
5 Package mechanical data
In order to meet environmental requirements, STMicroelectronics offers these devices in
ECOPACK
category of second level interconnect is marke d on the pa ckage and on the inner box label,
in compliance with JEDEC Standard JESD97. The maximum ratings related t o soldering
conditions are also marked on the inner box label. ECOPACK is an STMicroelectronics
trademark. ECOPACK specifications are available at: www.st.com
®
packages. These packages have a Lead-free second level interconnect. The
.
31/35
Package mechanical data TS4994
5.1 DFN10 package
Dimensions
Ref.
Millimeters Mils
Min. Typ. Max. Min. Typ. Max.
A 0.80 0.90 1.00 31.5 35.4 39.4
A1 0.02 0.05 0.8 2.0
A2 0.70 25.6
A3 0.20 7.9
b 0.18 0.23 0.30 7 .1 9.1 11.8
D 3.00 118.1
D2 2.21 2.26 2.31 87.0 89.0 91.0
E 3.00 118.1
E2 1.49 1.64 1.74 58.7 64.6 68.5
e 0.50 19.7
L 0.3 0.4 0.5 11.8 15.7 19.7
32/35
TS4994 Package mechanical data
5.2 MiniSO-8 package
Dimensions
Ref.
Millimeters Inches
Min. Typ. Max. Min. Typ. Max.
A 1.1 0.043
A1 0.05 0.10 0.15 0.002 0.004 0.006
A2 0.78 0.86 0.94 0.031 0.034 0.037
b 0.25 0.33 0.40 0.010 0.013 0.016
c 0.13 0.18 0.23 0.005 0.007 0.009
D 2.90 3.00 3.10 0.114 0.118 0.122
E 4.75 4.90 5.05 0.187 0.193 0.199
E1 2.90 3.00 3.10 0.114 0.118 0.122
e 0.65 0.026
K0°6°0°6°
L 0.40 0.55 0.70 0.016 0.022 0.028
L1 0.10 0.04
33/35
Revision history TS4994
6 Revision history
Date Revision Changes
1-Sep-2003 1 Initial release.
1-Oct-2004 2 Curves updated in the document.
2-Jan-2005 4 Update mechanical data on flip-chip package.
2-Apr-2005 4 Remove data on flip-chip package.
15-Nov- 2005 5 Mechanical data updated on DFN10 package.
12-Dec-2006 6 Removed demo board views. Format update.
34/35
TS4994
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