STMICROELECTRONICS TS4994IST

TS4994
1W Differential Input/Output Audio Power Amplifier
with Selectable Standby
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Differential inputs
Near zero pop & click
100dB PSRR @ 217Hz with grounded inputs
Operating from VCC = 2.5V to 5.5V
1W RAIL to RAIL output power @ Vcc=5V,
THD=1%, F=1kHz, with 8Ω load
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 &
MiniSO8
All lead-free packages
Pin Connections (top view)
TS4994IQT - DFN10
STBY
1
10
VO+
VIN -
2
9
VDD
STBY MODE
3
8
N/C
VIN +
4
7
GND
BYPASS
5
6
VO-
TS4994IST - MiniSO8
Description
The TS4994 is an audio power amplifier capable
of delivering 1W of continuous RMS output power
into an 8Ω load @ 5V. Thanks to its differential
inputs, it exhibits outstanding noise immunity.
STBY
1
8
VO+
VIN-
2
7
Vcc
VIN+
3
6
GND
An external standby mode control reduces the
supply current to less than 10nA. A STBY MODE
pin allows the standby pin to be active HIGH or
LOW (except in the MiniSO8 version). An internal
thermal shutdown protection is also provided,
making the device capable of sustaining shortcircuits.
BYPASS
4
5
VO-
The device is equipped with Common Mode
Feedback circuitry allowing outputs to be always
biased at Vcc/2 regardless of the input common
mode voltage.
Applications
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Mobile phones (cellular / cordless)
Laptop / notebook computers
PDAs
Portable audio devices
The TS4994 has been designed for high quality
audio applications such as mobile phones and
requires few external components.
Order Codes
Part Number
TS4994IQT
TS4994IST
April 2005
Temperature Range
Package
Packaging
Marking
-40°C to +85°C
-40°C to +85°C
DFN10
MiniSO8
Tape & Reel
Tape & Reel
K994
K994
Revision 4
1/31
TS4994
Application Component Information
1 Application Component Information
Components
Functional Description
CS
Supply Bypass capacitor which provides power supply filtering.
CB
Bypass capacitor which provides half supply filtering.
RFEED
RIN
CIN
Feedback resistor which sets the closed loop gain in conjunction with RIN
AV= Closed Loop Gain= RFEED/RIN.
Inverting input resistor which sets the closed loop gain in conjunction with RFEED.
Optional input capacitor making a high pass filter together with RIN. (fcl = 1 / (2 x Pi x RIN x CIN)
Figure 1. Typical Application DFN10 Version
VCC
+
Rfeed1
20k
9
Cs
1u
GND
VCC
Cin1
+
Diff. input -
Rin1
+
220nF 20k
Cin2 Rin2
GND
2 Vin-
-
4 Vin+
+
Vo+ 10
Vo6
220nF 20k
Diff. Input +
Optional
8 Ohms
5 Bypass
Bias
+
Cb
1u
Standby
Mode
Stdby
GND
1
7
GND
3
TS4994IQ
Rfeed2
GND
20k
GND VCC
GND VCC
Figure 2. Typical Application Mini-SO8 Version
VCC
+
Rfeed1
20k
7
Cs
1u
GND
VCC
+
Diff. input - Cin1
Rin1
+
GND
220nF 20k
Cin2
Rin2
220nF 20k
Diff. Input +
Optional
2 Vin-
-
3 Vin+
+
Vo+ 8
Vo5
8 Ohms
4 Bypass
Bias
Cb
1u
+
Standby
Stdby
GND
1
6
GND
GND
TS4994IS
Rfeed2
20k
GNDVCC
2/31
Absolute Maximum Ratings
TS4994
2 Absolute Maximum Ratings
Table 1. Key parameters and their absolute maximum ratings
Symbol
VCC
Parameter
1
Value
Unit
6
V
V
Toper
Input Voltage
Operating Free Air Temperature Range
GND to VCC
-40 to + 85
°C
Tstg
Storage Temperature
-65 to +150
°C
150
°C
120
215
°C/W
internally limited
2
200
200
260
W
kV
V
mA
°C
Value
Unit
Vi
Tj
Rthja
Pd
ESD
ESD
Supply voltage
2
Maximum Junction Temperature
Thermal Resistance Junction to Ambient
DFN10
Mini-SO8
Power Dissipation
Human Body Model
Machine Model
Latch-up Immunity
Lead Temperature (soldering, 10sec)
3
1) All voltages values are measured with respect to the ground pin.
2) The magnitude of input signal must never exceed VCC + 0.3V / GND - 0.3V
3) The device is protected by a thermal shutdown active at 150°C
Table 2. Operating conditions
Symbol
Parameter
VCC
Supply Voltage
2.5 to 5.5
V
VSM
Standby Mode Voltage Input:
Standby Active LOW
Standby Active HIGH
VSM=GND
VSM=VCC
V
VSTB
Standby Voltage Input:
Device ON (VSM=GND) or Device OFF (VSM=VCC)
Device OFF (VSM=GND) or Device ON (VSM=VCC)
TSD
RL
RTHJA
1.5 ≤ VSTB ≤ VCC
GND ≤ VSTB ≤ 0.4 1
V
Thermal Shutdown Temperature
150
°C
Load Resistor
≥8
Ω
Thermal Resistance Junction to Ambient
DFN10 2
Mini-SO8
80
190
°C/W
1) The minimum current consumption (ISTANDBY) is guaranteed when V STB=GND or V CC (i.e. supply rails) for the whole temperature
range.
2) When mounted on a 4-layer PCB.
3/31
TS4994
Electrical Characteristics
3 Electrical Characteristics
Table 3. Electrical characteristics - VCC = +5V, GND = 0V, Tamb = 25°C (unless otherwise
specified)
Symbol
Typ.
Max.
Unit
Supply Current
No input signal, no load
4
7
mA
Standby Current
No input signal, Vstdby = VSM = GND, RL = 8Ω
No input signal, Vstdby = VSM = VCC, RL = 8Ω
10
1000
nA
Voo
Differential Output Offset Voltage
No input signal, RL = 8Ω
0.1
10
mV
VICM
Input Common Mode Voltage
CMRR ≤ -60dB
0.6
VCC- 0.9
V
Output Power
THD = 1% Max, F= 1kHz, RL = 8Ω
0.8
ICC
ISTANDBY
Po
Parameter
Min.
1
W
THD + N
Total Harmonic Distortion + Noise
Po = 850mW rms, Av = 1, 20Hz ≤ F ≤ 20kHz, RL = 8Ω
0.5
%
PSRRIG
Power Supply Rejection Ratio with Inputs Grounded1
F = 217Hz, R = 8Ω, Av = 1, Cin = 4.7µF, Cb =1µF
Vripple = 200mVPP
100
dB
CMRR
Common Mode Rejection Ratio
F = 217Hz, RL = 8Ω, Av = 1, Cin = 4.7µF, Cb =1µF
Vic = 200mVPP
90
dB
SNR
Signal-to-Noise Ratio (A Weighted Filter, Av = 2.5)
(RL = 8Ω, THD +N < 0.7%, 20Hz ≤ F ≤ 20kHz)
100
dB
GBP
Gain Bandwidth Product
RL = 8Ω
2
MHz
VN
TWU
Output Voltage Noise, 20Hz ≤ F ≤ 20kHz, RL = 8Ω
Unweighted, Av = 1
A weighted, Av = 1
Unweighted, Av = 2.5
A weighted, Av = 2.5
Unweighted, Av = 7.5
A weighted, Av = 7.5
Unweighted, Standby
A weighted, Standby
Wake-Up Time2
Cb =1µF
6
5.5
12
10.5
33
28
1.5
1
15
1) Dynamic measurements - 20*log(rms(Vout)/rms (Vripple)). Vripple is the super-imposed sinus signal relative to Vcc.
2) Transition time from standby mode to fully operational amplifier.
4/31
µVRMS
ms
Electrical Characteristics
Table 4.
TS4994
Electrical Characteristics: VCC = +3.3V (all electrical values are guaranteed with correlation
measurements at 2.6V and 5V) GND = 0V, Tamb = 25°C (unless otherwise specified)
Symbol
Typ.
Max.
Unit
Supply Current No input signal, no load
3
7
mA
Standby Current
No input signal, Vstdby = VSM = GND, RL = 8Ω
No input signal, Vstdby = VSM = VCC, RL = 8Ω
10
1000
nA
Voo
Differential Output Offset Voltage
No input signal, RL = 8Ω
0.1
10
mV
VICM
Input Common Mode Voltage
CMRR ≤ -60dB
0.6
VCC- 0.9
V
Output Power
THD = 1% Max, F= 1kHz, RL = 8Ω
300
ICC
ISTANDBY
Po
Parameter
Min.
380
mW
THD + N
Total Harmonic Distortion + Noise
Po = 300mW rms, Av = 1, 20Hz ≤ F ≤ 20kHz, RL = 8Ω
0.5
%
PSRRIG
Power Supply Rejection Ratio with Inputs Grounded1
F = 217Hz, R = 8Ω, Av = 1, Cin = 4.7µF, Cb =1µF
Vripple = 200mVPP
100
dB
CMRR
Common Mode Rejection Ratio
F = 217Hz, RL = 8Ω, Av = 1, Cin = 4.7µF, Cb =1µF
Vic = 200mVPP
90
dB
SNR
Signal-to-Noise Ratio (A Weighted Filter, Av = 2.5)
(RL = 8Ω, THD +N < 0.7%, 20Hz ≤ F ≤ 20kHz)
100
dB
GBP
Gain Bandwidth Product
RL = 8Ω
2
MHz
VN
TWU
Output Voltage Noise, 20Hz ≤ F ≤ 20kHz, RL = 8Ω
Unweighted, Av = 1
A weighted, Av = 1
Unweighted, Av = 2.5
A weighted, Av = 2.5
Unweighted, Av = 7.5
A weighted, Av = 7.5
Unweighted, Standby
A weighted, Standby
Wake-Up Time2
Cb =1µF
6
5.5
12
10.5
33
28
1.5
1
15
µVRMS
ms
1) Dynamic measurements - 20*log(rms(Vout)/rms (Vripple)). Vripple is the super-imposed sinus signal relative to Vcc.
2) Transition time from standby mode to fully operational amplifier.
5/31
TS4994
Table 5.
Electrical Characteristics
Electrical Characteristics - VCC = +2.6V, GND = 0V, Tamb = 25°C (unless otherwise specified)
Symbol
Typ.
Max.
Unit
Supply Current
No input signal, no load
3
7
mA
Standby Current
No input signal, Vstdby = VSM = GND, RL = 8Ω
No input signal, Vstdby = VSM = VCC, RL = 8Ω
10
1000
nA
Voo
Differential Output Offset Voltage
No input signal, RL = 8Ω
0.1
10
mV
VICM
Input Common Mode Voltage
CMRR ≤ -60dB
0.6
VCC0.9
V
Output Power
THD = 1% Max, F= 1kHz, RL = 8Ω
200
ICC
ISTANDBY
Po
Parameter
Min.
250
mW
THD + N
Total Harmonic Distortion + Noise
Po = 225mW rms, Av = 1, 20Hz ≤ F ≤ 20kHz, RL = 8Ω
0.5
%
PSRRIG
Power Supply Rejection Ratio with Inputs Grounded1
F = 217Hz, R = 8Ω, Av = 1, Cin = 4.7µF, Cb =1µF
Vripple = 200mVPP
100
dB
CMRR
Common Mode Rejection Ratio
F = 217Hz, RL = 8Ω, Av = 1, Cin = 4.7µF, Cb =1µF
Vic = 200mVPP
90
dB
SNR
Signal-to-Noise Ratio (A Weighted Filter, Av = 2.5)
(RL = 8Ω, THD +N < 0.7%, 20Hz ≤ F ≤ 20kHz)
100
dB
GBP
Gain Bandwidth Product
RL = 8Ω
2
MHz
VN
TWU
Output Voltage Noise, 20Hz ≤ F ≤ 20kHz, RL = 8Ω
Unweighted, Av = 1
A weighted, Av = 1
Unweighted, Av = 2.5
A weighted, Av = 2.5
Unweighted, Av = 7.5
A weighted, Av = 7.5
Unweighted, Standby
A weighted, Standby
Wake-Up Time2
Cb =1µF
6
5.5
12
10.5
33
28
1.5
1
15
1) Dynamic measurements - 20*log(rms(Vout)/rms (Vripple)). Vripple is the super-imposed sinus signal relative to Vcc.
2) Transition time from standby mode to fully operational amplifier.
6/31
µVRMS
ms
Electrical Characteristics
TS4994
Figure 3. Current consumption vs. power
supply voltage
Figure 6. Current consumption vs. standby
voltage
3.0
4.0
Current Consumption (mA)
Current Consumption (mA)
No load
3.5 Tamb=25°C
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
1
2
3
4
2.5
Standby mode=0V
Standby mode=2.6V
2.0
1.5
1.0
Vcc = 2.6V
No load
Tamb=25°C
0.5
0.0
0.0
5
0.6
1.2
Power Supply Voltage (V)
Figure 4. Current consumption vs. standby
voltage
4.0
2.4
Figure 7. Differential DC output voltage vs.
common mode input voltage
1000
Av = 1
Tamb = 25°C
3.5
100
3.0
Vcc=3.3V
Standby mode=0V
2.5
Voo (mV)
Current Consumption (mA)
1.8
Standby Voltage (V)
Standby mode=5V
2.0
1.5
Vcc=2.5V
10
Vcc=5V
1
1.0
0.0
0.1
Vcc = 5V
No load
Tamb=25°C
0.5
0
1
2
3
4
0.01
0.0
5
Standby Voltage (V)
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 5. Current consumption vs. standby
voltage
Figure 8. Power dissipation vs. output power
0.6
3.0
2.5
Power Dissipation (W)
Current Consumption (mA)
3.5
Standby mode=0V
Standby mode=3.3V
2.0
1.5
1.0
Vcc = 3.3V
No load
Tamb=25°C
0.5
0.0
0.0
0.6
1.2
1.8
Standby Voltage (V)
2.4
3.0
RL=8Ω
0.4
0.2
RL=16Ω
Vcc=5V
F=1kHz
THD+N<1%
0.0
0.0
0.2
0.4
0.6
Output Power (W)
0.8
1.0
7/31
TS4994
Electrical Characteristics
Figure 9. Power dissipation vs. output power
Figure 12. Output power vs. power supply
voltage
1.50
RL=8Ω
0.2
0.1
RL=16Ω
0.0
0.0
0.1
Vcc=3.3V
F=1kHz
THD+N<1%
0.2
0.3
Output Power (W)
Output power @ 10% THD + N (W)
Power Dissipation (W)
0.3
1.00
8Ω
16Ω
0.75
0.50
0.25
32Ω
0.00
2.5
0.4
3.0
3.5
4.0
4.5
5.0
Vcc (V)
Figure 10. Power dissipation vs. output power
Figure 13. Output power vs. load resistance
0.20
1.0
Vcc=2.6V
F=1kHz
THD+N<1%
0.8
0.15
Output power (W)
Power Dissipation (W)
Cb = 1µF
F = 1kHz
BW < 125kHz
Tamb = 25°C
1.25
RL=8Ω
0.10
THD+N=1%
Cb = 1 F
F = 1kHz
BW < 125kHz
Tamb = 25°C
Vcc=5V
Vcc=4.5V
0.6
Vcc=4V
0.4
0.05
RL=16Ω
0.2
Vcc=3.5V
Vcc=3V
0.00
0.0
0.1
0.2
0.0
0.3
8
12
Output Power (W)
Figure 11. Output power vs. power
supply voltage
8Ω
16Ω
0.6
0.4
0.2
32Ω
0.0
2.5
3.5
4.0
32
1.5
with 4 layers PCB
1.0
0.5
AMR Value
0.0
3.0
Vcc (V)
8/31
DFN10 Package Power Dissipation (W)
Output power @ 1% THD + N (W)
0.8
28
Figure 14. Power derating curves
1.0
Cb = 1µF
F = 1kHz
BW < 125kHz
Tamb = 25°C
Vcc=2.5V
16
20
24
Load Resistance
4.5
5.0
0
25
50
75
Ambiant Temperature ( C)
100
125
Electrical Characteristics
TS4994
Figure 18. Open Loop gain vs. frequency
0
0.6
60
Gain
Nominal Value
-40
0.4
AMR Value
0.2
-80
20
0
25
50
75
100
-120
0
-20
0.0
Phase
-160
Vcc = 2.6V
ZL = 8Ω + 500pF
Tamb = 25°C
-40
0.1
125
Phase (°)
40
Gain (dB)
MiniSO8 Package Power Dissipation (W)
Figure 15. Power derating curves
1
10
100
1000
-200
10000
Frequency (kHz)
Ambiant Temperature ( C)
Figure 19. Close loop gain vs. frequency
Figure 16. Open loop gain vs. frequency
0
0
10
Phase
60
Gain
-40
0
Gain
-40
-120
0
-20
-40
0.1
-160
Vcc = 5V
ZL = 8Ω + 500pF
Tamb = 25°C
1
10
100
1000
-10
-80
-20
-120
-30
-200
10000
Vcc = 5V
Av = 1
ZL = 8Ω + 500pF
Tamb = 25°C
-40
0.1
1
Frequency (kHz)
Phase (°)
Phase
Gain (dB)
-80
20
Phase (°)
Gain (dB)
40
-160
10
100
1000
-200
10000
Frequency (kHz)
Figure 20. Close loop gain vs. frequency
Figure 17. Open loop gain vs. frequency
0
0
10
Phase
60
Gain
-40
0
Gain
-40
-120
0
-20
-40
0.1
-160
Vcc = 3.3V
ZL = 8Ω + 500pF
Tamb = 25°C
1
10
100
Frequency (kHz)
1000
-200
10000
-10
-80
-20
-120
-30
-40
0.1
Vcc = 3.3V
Av = 1
ZL = 8Ω + 500pF
Tamb = 25°C
1
Phase (°)
Phase
Gain (dB)
-80
20
Phase (°)
Gain (dB)
40
-160
10
100
1000
-200
10000
Frequency (kHz)
9/31
TS4994
Electrical Characteristics
Figure 24. PSRR vs. frequency
Figure 21. Close loop gain vs. frequency
0
10
0
Phase
-10
Gain
0
Vcc = 2.6V
Vripple = 200mVpp
Inputs = Grounded
Av = 1, Cin = 4.7µF
RL ≥ 8Ω
Tamb = 25°C
-20
-40
-120
-20
PSRR (dB)
-80
-10
Phase (°)
Gain (dB)
-30
-40
-50
Cb=0.1µF
-60
Cb=0.47µF
-70
Cb=1µF
-80
Vcc = 2.6V
Av = 1
ZL = 8Ω + 500pF
Tamb = 25°C
-30
-40
0.1
1
-90
-160
-100
Cb=0
-110
10
100
1000
-200
10000
-120
20
100
Frequency (kHz)
0
0
-20
-30
-40
PSRR (dB)
-10
Vcc = 5V
Vripple = 200mVpp
Inputs = Grounded
Av = 1, Cin = 4.7µF
RL ≥ 8Ω
Tamb = 25°C
-50
-60
-30
Cb=0.1µF
Cb=0.47µF
-70
Cb=1µF
-80
-90
-50
Cb=0.1µF
Cb=0.47µF
-60
-70
Cb=1µF
-90
Cb=0
-100
Cb=0
-110
-110
20
100
1000
Frequency (Hz)
-120
10000 20k
20
100
1000
Frequency (Hz)
10000 20k
Figure 26. PSRR vs. frequency
Figure 23. PSRR vs. frequency
0
0
-10
Vcc = 3.3V
Vripple = 200mVpp
Inputs = Grounded
Av = 1, Cin = 4.7µF
RL ≥ 8Ω
Tamb = 25°C
-20
-30
-40
-50
-60
-30
Cb=0.1µF
Cb=0.47µF
-70
Cb=1µF
-80
Vcc = 3.3V
Vripple = 200mVpp
Inputs = Grounded
Av = 2.5, Cin = 4.7µF
RL ≥ 8Ω
Tamb = 25°C
-20
PSRR (dB)
-10
PSRR (dB)
-40
-80
-100
-40
-50
-70
Cb=1µF
-80
-90
-100
-100
Cb=0
-110
Cb=0.1µF
Cb=0.47µF
-60
-90
10/31
Vcc = 5V
Vripple = 200mVpp
Inputs = Grounded
Av = 2.5, Cin = 4.7µF
RL ≥ 8Ω
Tamb = 25°C
-20
PSRR (dB)
-10
-120
10000 20k
Figure 25. PSRR vs. frequency
Figure 22. PSRR vs. frequency
-120
1000
Frequency (Hz)
Cb=0
-110
20
100
1000
Frequency (Hz)
10000 20k
-120
20
100
1000
Frequency (Hz)
10000 20k
Electrical Characteristics
TS4994
Figure 30. PSRR vs. frequency
Figure 27. PSRR vs. frequency
0
0
-20
-30
PSRR (dB)
-10
Vcc = 2.6V
Vripple = 200mVpp
Inputs = Grounded
Av = 2.5, Cin = 4.7µF
RL ≥ 8Ω
Tamb = 25°C
-40
-50
-30
Cb=0.1µF
Cb=0.47µF
-60
-70
Cb=1µF
-80
-40
-50
-70
Cb=1µF
-90
Cb=0
-110
-100
Cb=0
-110
20
100
1000
Frequency (Hz)
10000 20k
-120
20
Vcc = 5V
Vripple = 200mVpp
Inputs = Floating
Rfeed = 20kΩ
RL ≥ 8Ω
Tamb = 25°C
-30
-40
-50
-60
Cb=0.1µF
Cb=0.47µF
-70
Vcc = 5V
Vripple = 200mVpp
Inputs Grounded
F = 217Hz
Av = 1
RL ≥ 8Ω
Tamb = 25°C
-20
-40
PSRR(dB)
-20
Cb=1µF
Cb=0.47µF
Cb=0.1µF
-60
Cb=0
Cb=1µF
-80
-80
-90
-100
Cb=0
-110
20
100
1000
Frequency (Hz)
-100
0
10000 20k
0
Vcc = 3.3V
Vripple = 200mVpp
Inputs = Floating
Rfeed = 20kΩ
RL ≥ 8Ω
Tamb = 25°C
-30
-40
-50
-60
-20
PSRR(dB)
-20
Cb=0.1µF
Cb=0.47µF
-70
2
-40
Vcc = 3.3V
Vripple = 200mVpp
Inputs Grounded
F = 217Hz
Av = 1
RL ≥ 8Ω
Tamb = 25°C
-60
4
5
Cb=1µF
Cb=0.47µF
Cb=0.1µF
Cb=0
Cb=1µF
-80
3
Figure 32. PSRR vs. common mode input
voltage
0
-10
1
Common Mode Input Voltage (V)
Figure 29. PSRR vs. frequency
PSRR (dB)
10000 20k
1000
Frequency (Hz)
0
0
-10
-80
-90
-100
Cb=0
-110
-120
100
Figure 31. PSRR vs. common mode input
voltage
Figure 28. PSRR vs. frequency
PSRR (dB)
Cb=0.47µF
-80
-100
-120
Cb=0.1µF
-60
-90
-120
Vcc = 2.6V
Vripple = 200mVpp
Inputs = Floating
Rfeed = 20kΩ
RL ≥ 8Ω
Tamb = 25°C
-20
PSRR (dB)
-10
20
100
1000
Frequency (Hz)
10000 20k
-100
0.0
0.6
1.2
1.8
2.4
3.0
Common Mode Input Voltage (V)
11/31
TS4994
Electrical Characteristics
Figure 33. PSRR vs. common mode input
voltage
PSRR(dB)
-20
-40
0
Vcc = 2.5V
Vripple = 200mVpp
Inputs Grounded
F = 217Hz
Av = 1
RL ≥ 8Ω
Tamb = 25°C
-60
-10
-30
Cb=1µF
Cb=0.47µF
Cb=0.1µF
Cb=0
-80
-40
-60
-70
-90
-100
-110
0.5
1.0
1.5
2.0
-120
2.5
20
100
Common Mode Input Voltage (V)
Figure 34. CMRR vs. frequency
1000
Frequency (Hz)
10000 20k
Figure 37. CMRR vs. frequency
0
0
Vcc = 5V
Vic = 200mVpp
Av = 1, Cin = 470µF
RL ≥ 8Ω
Tamb = 25°C
-20
-30
-40
-50
-60
Vcc = 5V
Vic = 200mVpp
Av = 2.5, Cin = 470µF
RL ≥ 8Ω
Tamb = 25°C
-10
-20
-30
Cb=1µF
Cb=0.47µF
Cb=0.1µF
Cb=0
CMRR (dB)
-10
CMRR (dB)
Cb=1µF
Cb=0.47µF
Cb=0.1µF
Cb=0
-50
-80
-100
0.0
Vcc = 2.6V
Vic = 200mVpp
Av = 1, Cin = 470µF
RL ≥ 8Ω
Tamb = 25°C
-20
CMRR (dB)
0
Figure 36. CMRR vs. frequency
-70
-80
-40
Cb=1µF
Cb=0.47µF
Cb=0.1µF
Cb=0
-50
-60
-70
-90
-80
-100
-110
-90
-120
-100
20
100
1000
Frequency (Hz)
10000 20k
Figure 35. PSRR vs. frequency
100
1000
Frequency (Hz)
10000 20k
Figure 38. CMRR vs. frequency
0
0
Vcc = 3.3V
Vic = 200mVpp
Av = 1, Cin = 470µF
RL ≥ 8Ω
Tamb = 25°C
-20
-30
-40
-50
-60
Vcc = 3.3V
Vic = 200mVpp
Av = 2.5, Cin = 470µF
RL ≥ 8Ω
Tamb = 25°C
-10
-20
-30
Cb=1µF
Cb=0.47µF
Cb=0.1µF
Cb=0
CMRR (dB)
-10
CMRR (dB)
20
-70
-80
-40
Cb=1µF
Cb=0.47µF
Cb=0.1µF
Cb=0
-50
-60
-70
-90
-80
-100
-110
-90
-120
-100
12/31
20
100
1000
Frequency (Hz)
10000 20k
20
100
1000
Frequency (Hz)
10000 20k
Electrical Characteristics
TS4994
Figure 42. THD+N vs. output power
Figure 39. CMRR vs. frequency
10
0
-20
CMRR (dB)
-30
-40
THD + N (%)
Vcc = 2.6V
Vic = 200mVpp
Av = 2.5, Cin = 470µF
RL ≥ 8Ω
Tamb = 25°C
-10
Cb=1µF
Cb=0.47µF
Cb=0.1µF
Cb=0
-50
-60
-70
RL = 8Ω
F = 20Hz
Av = 1
1
Cb = 1µF
BW < 125kHz
Tamb = 25°C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.1
0.01
-80
-90
-100
20
100
10000 20k
1000
Frequency (Hz)
1E-3
1E-3
0.01
0.1
Output Power (W)
1
Figure 43. THD+N vs. output power
Figure 40. CMRR vs. common mode input
voltage
10
0
Vcc=3.3V
Vcc=2.5V
THD + N (%)
CMRR(dB)
-20
Vic = 200mVpp
F = 217Hz
Av = 1, Cb = 1µF
RL ≥ 8Ω
Tamb = 25°C
-40
-60
RL = 8Ω
F = 20Hz
Av = 2.5
1
Cb = 1µF
BW < 125kHz
Tamb = 25°C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.1
0.01
-80
-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
1E-3
1E-3
Common Mode Input Voltage (V)
0.01
0.1
Output Power (W)
1
Figure 44. THD+N vs. output power
Figure 41. CMRR vs. common mode input
voltage
10
0
Vcc=3.3V
Vcc=2.5V
THD + N (%)
CMRR(dB)
-20
Vic = 200mVpp
F = 217Hz
Av = 1, Cb = 0
RL ≥ 8Ω
Tamb = 25°C
-40
-60
RL = 8Ω
F = 20Hz
Av = 7.5
1 Cb = 1µF
BW < 125kHz
Tamb = 25°C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.1
-80
0.01
-100
0.0
Vcc=5V
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
1E-3
0.01
0.1
Output Power (W)
1
Common Mode Input Voltage (V)
13/31
TS4994
Electrical Characteristics
Figure 48. THD+N vs. output power
Figure 45. THD+N vs. output power
RL = 8Ω
F = 1kHz
Av = 1
1 Cb = 1µF
BW < 125kHz
Tamb = 25°C
10
Vcc=2.6V
THD + N (%)
THD + N (%)
10
Vcc=3.3V
Vcc=5V
0.1
RL = 8Ω
F = 20kHz
Av = 1
Cb = 1µF
BW < 125kHz
1 Tamb = 25°C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.1
0.01
1E-3
0.01
0.1
Output Power (W)
1
1E-3
10
10
Vcc=2.6V
THD + N (%)
THD + N (%)
1
Figure 49. THD+N vs. output power
Figure 46. THD+N vs. output power
RL = 8Ω
F = 1kHz
Av = 2.5
1 Cb = 1µF
BW < 125kHz
Tamb = 25°C
0.01
0.1
Output Power (W)
Vcc=3.3V
Vcc=5V
0.1
RL = 8Ω
F = 20kHz
Av = 2.5
Cb = 1µF
BW < 125kHz
1 Tamb = 25°C
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.1
0.01
1E-3
0.01
0.1
Output Power (W)
1E-3
1
10
10
RL = 8Ω
F = 20kHz
Av = 7.5
Cb = 1µF
BW < 125kHz
Tamb = 25°C
Vcc=2.6V
Vcc=3.3V
THD + N (%)
THD + N (%)
1
Figure 50. THD+N vs. output power
Figure 47. THD+N vs. output power
RL = 8Ω
F = 1kHz
Av = 7.5
1 Cb = 1µF
BW < 125kHz
Tamb = 25°C
0.01
0.1
Output Power (W)
Vcc=5V
0.1
1
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.01
1E-3
14/31
0.01
0.1
Output Power (W)
1
0.1
1E-3
0.01
0.1
Output Power (W)
1
Electrical Characteristics
TS4994
Figure 54. THD+N vs. output power
Figure 51. THD+N vs. output power
10
RL = 16Ω
F = 20Hz
1 Av = 1
Cb = 1µF
BW < 125kHz
Tamb = 25°C
0.1
RL = 16Ω
F = 1kHz
Av = 7.5
1 Cb = 1µF
BW < 125kHz
Tamb = 25°C
Vcc=2.6V
Vcc=3.3V
THD + N (%)
THD + N (%)
10
Vcc=5V
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.1
0.01
0.01
1E-3
1E-3
0.01
0.1
Output Power (W)
1
1E-3
10
10
RL = 16Ω
F = 20kHz
Av = 1
Cb = 1µF
1
BW < 125kHz
Tamb = 25°C
Vcc=2.6V
Vcc=3.3V
THD + N (%)
THD + N (%)
1
Figure 55. THD+N vs. output power
Figure 52. THD+N vs. output power
RL = 16Ω
F = 20Hz
1 Av = 7.5
Cb = 1µF
BW < 125kHz
Tamb = 25°C
0.1
0.01
0.1
Output Power (W)
Vcc=5V
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.1
0.01
1E-3
1E-3
0.01
0.1
Output Power (W)
1
0.01
1E-3
10
10
RL = 16Ω
F = 20kHz
Av = 7.5
Cb = 1µF
BW < 125kHz
Tamb = 25°C
Vcc=2.6V
Vcc=3.3V
THD + N (%)
THD + N (%)
1
Figure 56. THD+N vs. output power
Figure 53. THD+N vs. output power
RL = 16Ω
F = 1kHz
1 Av = 1
Cb = 1µF
BW < 125kHz
Tamb = 25°C
0.1
0.01
0.1
Output Power (W)
Vcc=5V
Vcc=2.6V
Vcc=3.3V
Vcc=5V
1
0.01
1E-3
1E-3
0.01
0.1
Output Power (W)
1
0.1
1E-3
0.01
0.1
Output Power (W)
1
15/31
TS4994
Electrical Characteristics
Figure 60. THD+N vs. output power
Figure 57. THD+N vs. output power
10
F=20kHz
THD + N (%)
THD + N (%)
1
10
RL = 8Ω
Vcc = 5V
Av = 1
Cb = 0
BW < 125kHz
Tamb = 25°C
F=1kHz
0.1
RL = 16Ω
Vcc = 2.6V
Av = 1, Cb = 0
1
BW < 125kHz
Tamb = 25°C
F=20kHz
F=1kHz
0.1
F=20Hz
F=20Hz
0.01
0.01
1E-3
0.01
0.1
Output Power (W)
1E-3
1E-3
1
10
10
RL = 8Ω
Vcc = 2.6V
Av = 1, Cb = 0
1
BW < 125kHz
Tamb = 25°C
THD + N (%)
F=20kHz
F=1kHz
0.1
RL = 8Ω
Av = 1
Cb = 1µF
1
Bw < 125kHz
Tamb = 25°C
Vcc=2.6V, Po=225mW
0.1
0.01
0.01
Vcc=5V, Po=850mW
F=20Hz
1E-3
1E-3
1E-3
0.01
Output Power (W)
0.1
20
100
1000
Frequency (Hz)
10000 20k
Figure 62. THD+N vs. frequency
Figure 59. THD+N vs. output power
10
10
RL = 16Ω
Vcc = 5V
Av = 1, Cb = 0
1
BW < 125kHz
Tamb = 25°C
F=20kHz
THD + N (%)
THD + N (%)
0.1
Figure 61. THD+N vs. frequency
Figure 58. THD+N vs. output power
THD + N (%)
0.01
Output Power (W)
F=1kHz
0.1
RL = 8Ω
Av = 1
Cb = 0
1
Bw < 125kHz
Tamb = 25°C
Vcc=2.6V, Po=225mW
0.1
F=20Hz
0.01
0.01
Vcc=5V, Po=850mW
1E-3
1E-3
16/31
1E-3
0.01
0.1
Output Power (W)
1
20
100
1000
Frequency (Hz)
10000 20k
Electrical Characteristics
TS4994
Figure 66. THD+N vs. frequency
Figure 63. THD+N vs. frequency
10
RL = 8Ω
Av = 7.5
Cb = 1µF
Bw < 125kHz
1 Tamb = 25°C
RL = 16Ω
Av = 7.5
Cb = 1µF
1
Bw < 125kHz
Tamb = 25°C
Vcc=2.6V, Po=225mW
THD + N (%)
THD + N (%)
10
0.1
Vcc=2.6V, Po=155mW
0.1
0.01
Vcc=5V, Po=850mW
0.01
20
100
1000
Frequency (Hz)
10000 20k
Vcc=5V, Po=600mW
1E-3
10000 20k
1000
Frequency (Hz)
110
10
RL = 8Ω
Av = 7.5
Cb = 0
Bw < 125kHz
1 Tamb = 25°C
RL=16Ω
Signal to Noise Ratio (dB)
THD + N (%)
100
Figure 67. SNR vs. power supply voltage with
unweighted filter
Figure 64. THD+N vs. frequency
Vcc=2.6V, Po=225mW
0.1
Vcc=5V, Po=850mW
0.01
20
20
100
1000
Frequency (Hz)
10000 20k
105
100
RL=8Ω
95
90
Av = 2.5
85 Cb = 1µF
THD+N < 0.7%
Tamb = 25°C
80
2.5
3.0
3.5
4.0
4.5
5.0
Power Supply Voltage (V)
Figure 68. SNR vs. power supply voltage with
a weighted filter
Figure 65. THD+N vs. frequency
RL = 16Ω
Av = 1
Cb = 1µF
1
Bw < 125kHz
Tamb = 25°C
110
Vcc=2.6V, Po=155mW
0.1
0.01
Vcc=5V, Po=600mW
1E-3
20
100
1000
Frequency (Hz)
10000 20k
Signal to Noise Ratio (dB)
THD + N (%)
10
RL=16Ω
105
100
RL=8Ω
95
90
Av = 2.5
85 Cb = 1µF
THD+N < 0.7%
Tamb = 25°C
80
2.5
3.0
3.5
4.0
4.5
5.0
Power Supply Voltage (V)
17/31
TS4994
Electrical Characteristics
Figure 69. Startup time vs. bypass capacitor
20
Tamb=25°C
Startup Time (ms)
Vcc=5V
15
Vcc=3.3V
10
5
0
0.0
18/31
Vcc=2.6V
0.4
0.8
1.2
1.6
Bypass Capacitor Cb ( F)
2.0
Application Information
TS4994
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 Vcc/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:
l Very high PSRR (Power Supply Rejection Ratio).
l High common mode noise rejection.
l Virtually zero pop without additional circuitry, giving an faster start-up time compared to conventional
single-ended input amplifiers.
l Easier interfacing with differential output audio DAC.
l No input coupling capacitors required thanks to common mode feedback loop.
l In theory, the filtering of the internal bias by an external bypass capacitor is not necessary. But, to
reach maximal performances in all tolerance situations, it’s better to keep this option.
The main disadvantage is:
l As the differential function is directly linked to external resistors mismatching, in order to reach
maximal performances of the amplifier paying particular attention to this mismatching is mandatory.
4.2 Gain in typical application schematic
Typical differential applications are shown on the figures on page 2.
In the flat region of the frequency-response curve (no Cin effect), the differential gain is expressed by the
relation:
Av diff =
VO + − VO −
R
= feed
Diff.Input + −Diff.Input −
Rin
where Rin = Rin1 = Rin2 and Rfeed = R feed1 = R feed2 .
Note:
For the rest of this chapter, Avdiff will be called Av to simplify the expression.
4.3 Common mode feedback loop limitations
As explained previously, the common mode feedback loop allows the output DC bias voltage to be
averaged at Vcc/2 for any DC common mode bias input voltage.
However, due to VICM limitation of the input stage (see Electrical Characteristics on page 4), the
common mode feedback loop can ensure its role only within a defined range. This range depends upon
the values of Vcc, Rin and Rfeed (Av). To have a good estimation of the VICM value, we can apply this
formula:
Vcc × Rin + 2 × VIC × Rfeed
(V)
VICM =
2 × (Rin + Rfeed )
with
VIC =
Diff.Input + + Diff.Input −
2
(V)
19/31
TS4994
Application Information
and the result of the calculation must be in the range:
0.6V ≤ VICM ≤ Vcc − 0.9V
If the result of VICM calculation is not in the previous range, an input coupling capacitor must be used.
Example: With Vcc=2.5V, R in=Rfeed=20k and V IC=2V, we found VICM=1.63V. This is higher than 2.5V0.9V=1.6V, so input coupling capacitors are required or you will have to change the VIC value.
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. FCL is in Hz.
1
FCL =
(Hz)
2 × π × Rin × Cin
In the high-frequency region, you can limit the bandwidth by adding a capacitor (Cfeed) in parallel with
Rfeed. It forms a low-pass filter with a -3dB cut-off frequency. FCH is in Hz.
1
FCH =
(Hz)
2 × π × Rfeed × Cfeed
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.
We will discuss the influence of mismatching on PSRR and CMRR performance in more detail in the
following paragraphs.
Example: A typical application with input coupling and feedback capacitor with FCL=50Hz and
FCH=8kHz. We assume that the mismatching between Rin1,2 and C feed1,2 can be neglected. If we sweep
the frequency from DC to 20kHz we observe the following with respect to the PSRR value:
l From DC to 200Hz, the C in impedance decreases from infinite to a finite value and the Cfeed
impedance is high enough to be neglected. Due to the tolerance of C in1,2, we must introduce a
mismatch factor (Rin1 x Cin ≠ Rin2 x Cin2) that will decrease the PSRR performance.
l From 200Hz to 5kHz, the C in impedance is low enough to be neglected when compare to Rin, 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.
l From 5kHz to 20kHz, the C in impedance is low to be neglected when compared to Rin, and the Cfeed
impedance decreases to a finite value. Due to tolerance of C feed1,2, we introduce a mismatching
factor (R feed1 x C feed1 ≠ Rfeed2 x Cfeed2) that will decrease the PSRR performance.
20/31
Application Information
TS4994
4.5 Calculating the influence of mismatching
On PSRR performance:
For this calculation, we consider that Cin and C feed have no influence.
We use the same kind of resistor (same tolerance) and ∆R is the tolerance value in %.
The following equation is valid for frequencies ranging from DC to about 1kHz. Above this frequency,
parasitic effects start to be significant and a literal equation is not possible to write.
The PSRR equation is (∆R in %):
⎡ ∆R × 100 ⎤
PSRR ≤ 20 × Log⎢
2 ⎥
⎣ (10000 − ∆R ) ⎦
(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 (∆R in %, Cb in microFarad and F in Hz) is:
∆R × 100
PSRR ≤ 20 × log ----------------------------------------------------------------------------------------------------2
2
2
( 10000 – ∆R ) × 1 + F × C b × 22.2
(dB)
Example: With ∆R=0.1% and Cb=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 and illustrates the fact
that with only a small bypass capacitor, the TS4994 produce high PSRR performance.
In addition, it’s important to note that this is a theoretical formula. As 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.
The three following graphs show PSRR versus frequency and versus bypass capacitor Cb in worst-case
condition (∆R=0.1%).
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
Vcc = 5V, Vripple = 200mVpp
Av = 1, Cin = 4.7µF
∆R/R = 0.1%, RL ≥ 8Ω
Tamb = 25°C, Inputs = Grounded
Cb=0
Cb=0.1µF
Cb=1µF
20
100
Cb=0.47µF
1000
Frequency (Hz)
Figure 71. PSRR vs. frequency worst case
condition
PSRR (dB)
PSRR (dB)
Figure 70. PSRR vs. frequency worst case
condition
10000 20k
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
Vcc = 3.3V, Vripple = 200mVpp
Av = 1, Cin = 4.7µF
∆R/R = 0.1%, RL ≥ 8Ω
Tamb = 25°C, Inputs = Grounded
Cb=0
Cb=0.1µF
Cb=1µF
20
100
Cb=0.47µF
1000
Frequency (Hz)
10000 20k
21/31
TS4994
Application Information
PSRR (dB)
Figure 72. PSRR vs. frequency worst case condition
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
Vcc = 2.5V, Vripple = 200mVpp
Av = 1, Cin = 4.7µF
∆R/R = 0.1%, RL ≥ 8Ω
Tamb = 25°C, Inputs = Grounded
Cb=0
Cb=0.1µF
Cb=1µF
20
100
Cb=0.47µF
10000 20k
1000
Frequency (Hz)
The two following graphs show typical application of TS4994 with four 0.1% tolerances and a random
choice for them.
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
Figure 74. PSRR vs. frequency with random
choice condition
Vcc = 5V, Vripple = 200mVpp
Av = 1, Cin = 4.7µF
∆R/R ≤ 0.1%, RL ≥ 8Ω
Tamb = 25°C, Inputs = Grounded
Cb=0
Cb=0.1µF
Cb=1µF
20
100
PSRR (dB)
PSRR (dB)
Figure 73. PSRR vs. frequency with random
choice condition
Cb=0.47µF
1000
Frequency (Hz)
10000 20k
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
Vcc = 2.5V, Vripple = 200mVpp
Av = 1, Cin = 4.7µF
∆R/R ≤ 0.1%, RL ≥ 8Ω
Tamb = 25°C, Inputs = Grounded
Cb=0.1µF
Cb=1µF
20
100
Cb=0
Cb=0.47µF
1000
Frequency (Hz)
10000 20k
CMRR performance
For this calculation, we consider there to be no influence of Cin and Cfeed. Cb has no influence in the
calculation of the CMRR.
We use the same kind of resistor (same tolerance) and ∆R is the tolerance value in %.
The following equation is valid for frequencies ranging from DC to about 1kHz. Above this frequency,
parasitic effects start to be significant and a literal equation is not possible to write.
The CMRR equation is (∆R in %):
⎡ ∆R × 200 ⎤
CMRR ≤ 20 × Log⎢
2 ⎥
⎣ (10000 − ∆R ) ⎦
(dB)
Example: With ∆R=1%, the minimum CMRR would be -34dB.
With a DC Vic=2.5V, the DC differential output (Voo) which results is 50mV maximum. As this Voo is
across the load, for an 8Ω load the extra consumption would be 50mV/8=6.2mA.
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Application Information
TS4994
With ∆R=1%, the minimum CMRR would be -53dB that give Voo=5.6mV and an maximum extra
consumption less than 700µA.
This example is of a worst case scenario where each resistor has extreme tolerance and illustrates the
fact that for CMRR, good matching is essential.
As with the PSRR, due to self-generated noise, the TS4994 CMRR limitation would be about -110dB.
Figures 75 and 76 show CMRR versus frequency and versus bypass capacitor Cb in worst-case condition
(∆R=0.1%).
Figure 75. CMRR vs. frequency worst case
condition
Figure 76. CMRR vs. frequency worst case
condition
0
0
Vcc = 5V
Vic = 200mVpp
Av = 1, Cin = 470µF
∆R/R = 0.1%, RL ≥ 8Ω
Tamb = 25°C
-20
-30
-40
-20
-30
-40
Cb=1µF
Cb=0
Cb=1µF
Cb=0
-50
-50
-60
Vcc = 2.5V
Vic = 200mVpp
Av = 1, Cin = 470µF
∆R/R = 0.1%, RL ≥ 8Ω
Tamb = 25°C
-10
CMRR (dB)
CMRR (dB)
-10
-60
20
100
1000
Frequency (Hz)
10000 20k
20
100
1000
Frequency (Hz)
10000 20k
Figures 77 and 78 show CMRR versus frequency for a typical application with four 0.1% tolerances and
a random choice for them.
Figure 77. CMRR vs. frequency with random
choice condition
Figure 78. CMRR vs. frequency with random
choice condition
0
0
Vcc = 5V
Vic = 200mVpp
Av = 1, Cin = 470µF
∆R/R ≤ 0.1%, RL ≥ 8Ω
Tamb = 25°C
CMRR (dB)
-20
-30
-20
-40
-50
Cb=1µF
Cb=0
-60
-30
-40
-50
-70
-80
-80
-90
20
100
1000
Frequency (Hz)
Cb=1µF
Cb=0
-60
-70
-90
Vcc = 2.5V
Vic = 200mVpp
Av = 1, Cin = 470µF
∆R/R ≤ 0.1%, RL ≥ 8Ω
Tamb = 25°C
-10
CMRR (dB)
-10
10000 20k
20
100
1000
Frequency (Hz)
10000 20k
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TS4994
Application Information
4.6 Power dissipation and efficiency
Assumptions:
l Load voltage and current are sinusoidal (Vout and Iout)
l Supply voltage is a pure DC source (Vcc)
Regarding the load we have:
V out = V PEAK sinωt (V)
and
V out
I out = -------------- (A)
RL
and
VPE AK2
P out = ---------------------- (W)
2R L
Therefore, the average current delivered by the supply voltage is:
I CC
AVG
VPEAK
= 2 -------------------- (A)
πR L
The power delivered by the supply voltage is:
Psupply = Vcc Icc AVG (W)
Then, the power dissipated by each amplifier is
Pdiss = Psupply - Pout (W)
2 2V CC
P diss = ------------------------ P out – P ou t
π RL
and the maximum value is obtained when:
∂Pdiss
---------------------- = 0
∂P out
and its value is:
Pdiss max =
Note:
2 Vcc 2
π 2RL
(W)
This maximum value is only dependent on power supply voltage and load values.
The efficiency is the ratio between the output power and the power supply
P out
πV P E A K
η = --------------------- = ----------------------P supply
4V C C
The maximum theoretical value is reached when Vpeak = Vcc, so
π
----- = 78.5%
4
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Application Information
TS4994
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.
To calculate the maximum ambient temperature TAMB allowable, we need to know:
l Power supply Voltage value, Vcc
l Load resistor value, RL
l The package type, RTHJA
Example: Vcc=5V, RL=8Ω, RTHJAFlip-Chip=100°C/W (100mm2 copper heatsink).
We calculate Pdissmax = 633mW.
With
TAMB = 125°C − RTHJA × Pdiss
(°C)
TAMB = 125-100x0.633=61.7°C
4.7 Decoupling of the circuit
Two capacitors are needed to correctly bypass the TS4994. A power supply bypass capacitor CS and a
bias voltage bypass capacitor CB.
CS 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 CS of 1µF, you can expect similar THD+N
performances to those shown in the datasheet.
In the high frequency region, if CS is lower than 1µF, it increases THD+N and disturbances on the power
supply rail are less filtered.
On the other hand, if CS is higher than 1µF, those disturbances on the power supply rail are more filtered.
Cb 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).
4.8 Wake-up Time: TWU
When the standby is released to put the device ON, the bypass capacitor Cb will not be charged
immediately. As Cb is directly linked to the bias of the amplifier, the bias will not work properly until the Cb
voltage is correct. The time to reach this voltage is called the wake-up time or TWU and is specified in the
tables found in Electrical Characteristics on page 4, with Cb=1µF. During the wake-up time phase, the
TS4994 gain is close to zero. After the wake-up time period, the gain is released and set to its nominal
value.
If Cb has a value other than 1µF, please refer to the graph in Figure 69 on page 18 to establish the wakeup time value.
4.9 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 microseconds.
Note:
In shutdown mode, Bypass pin and Vin+, Vin- pins are short-circuited to ground by internal switches. This allows
a quick discharge of Cb and Cin capacitors.
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TS4994
Application Information
4.10 Pop performance
In theory, due to a fully differential structure, the pop performance of the TS4994 should be perfect.
However, due to Rin, Rfeed, and C in mismatching, some noise could remain at startup. In TS4994 we
included a pop reduction circuitry reach the pop that is theoretical with mismatched components. With this
circuitry, the TS4994 is close to zero pop for all common applications possible.
In addition, when the TS4994 is set in standby, due to the high impedance output stage configuration in
this mode, no pop is possible.
4.11 Single ended input configuration
It’s possible to use the TS4994 in a single-ended input configuration. However, input coupling capacitors
areneeded in this configuration. The schematic in Figure 79 shows this configuration using the miniSO8
version of the TS4994 as example.
Figure 79. Single ended input typical application
VCC
+
Rfeed1
20k
7
Cs
1u
GND
VCC
Cin1
+
Ve
+
220nF
Cin2
GND
220nF
Rin1
2 Vin-
-
3 Vin+
+
Rin2
Vo5
20k
8 Ohms
4 Bypass
+
Optional
Vo+ 8
20k
Bias
Cb
1u
Standby
Stdby
GND
1
6
GND
GND
TS4994IS
Rfeed2
20k
GND VCC
The components calculations remain the same except for the gain. The new formula is:
V − VO − Rfeed
Av SE = O +
=
Ve
Rin
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Application Information
TS4994
4.12 Demoboard
A demoboard for the TS4994 is available, however it is designed only for the TS4994 in the DFN10
package. However, we can guarantee that all electrical parameters are similar except for the power
dissipation.
For more information about this demoboard, please refer to Application Note AN2013.
Figure 80. Demoboard schematic
Cn8
Vcc
+
C4
1uF/6V
C5
100nF/10V
GND
R2
GND
GND
22k/1%
R4
22k/1%
Cn3
9
J1
VCC
Cn1
C1
Pos. Input
R1
2 Vin-
-
4 Vin+
+
Cn5
Vo+ 10
100nF/10V 22k/1%
100nF/10V
GND
Neg. Input
C2
Cn2
R3
5 Bypass
+
GND
Vo6
22k/1%
Bias
C3
1uF/6V
J2
Standby
Cn4
Mode
Stdby
GND
1
7
GND
3
Cn6
J3
Vcc
Figure 81. Components location
Vcc Cn7
1
1
2
2
3
GND
TS4994DFN10
GND
J4
3
GND
Figure 82. Top layer
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TS4994
Figure 83. Bottom layer
28/31
Application Information
Package Mechanical Data
TS4994
5 Package Mechanical Data
5.1 MiniSO8 package
29/31
TS4994
Package Mechanical Data
5.2 DFN10 package
Dimensions in millimeters unless otherwise indicated.
3.0
10
3.0
0.35
1
0.8
0.25
0.5
* The Exposed Pad is connected to the Ground
30/31
Revision History
TS4994
6 Revision History
Date
Revision
01 Sept. 2003
1
01 Oct. 2004
Description of Changes
First Release
Curves updated in the document
01 Jan. 2005
2
Update Mechanical Data on Flip-Chip Package
17 Mar. 2005
3
Remove datas on Flip-Chip Package
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of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted
by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject
to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not
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