TI TS4994IST

TS4994
1W differential input/output audio power amplifier
with selectable standby
Features
Pin connections (top view)
■
Differential inputs
■
Near-zero pop & click
■
100dB PSRR @ 217Hz with grounded inputs
■
Operating range 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) &
MiniSO-8
■
All lead-free packages
TS4994IQT - DFN10
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
1
10
VO+
VIN -
2
9
VDD
STBY MODE
3
8
N/C
VIN +
4
7
GND
BYPASS
5
6
VO-
TS4994IST - MiniSO-8
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 inputs,
it exhibits outstanding noise immunity.
STBY
STBY
1
8
VIN-
2
7
Vcc
VO+
VIN+
3
6
GND
BYPASS
4
5
VO-
biased at VCC/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
■
Mobile phones (cellular / cordless)
■
Laptop / notebook computers
■
PDAs
■
Portable audio devices
Order codes
Part number
Temperature range
TS4994IQT
Package
DFN10
-40°C to +85°C
TS4994IST
December 2006
Packing
Marking
K994
Tape & reel
MiniSO-8
Rev 6
K994
1/35
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
5
6
2/35
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: tWU
4.10
Shutdown time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.11
Pop performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.12
Single-ended input configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.13
Demoboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.1
DFN10 package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.2
MiniSO-8 package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
TS4994
Application component information
Components
Functional description
Cs
Supply bypass capacitor that provides power supply filtering.
Cb
Bypass capacitor that provides half supply filtering.
Rfeed
Feedback resistor that sets the closed loop gain in conjunction with Rin
AV = closed loop gain = Rfeed/Rin.
Rin
Inverting input resistor that sets the closed loop gain in conjunction with Rfeed.
Cin
Optional input capacitor making a high pass filter together with Rin.
(FCL = 1/(2πRinCin).
Figure 1.
Typical application, DFN10 version
VCC
+
Rfeed1
20k
9
Cs
1u
GND
VCC
Cin1
+
Diff. input -
220nF 20k
Cin2 Rin2
+
GND
Rin1
220nF 20k
Diff. Input +
Optional
+
1
Application component information
2 Vin-
-
4 Vin+
+
Vo+ 10
Vo6
8 Ohms
5 Bypass
Bias
Cb
1u
Standby
Mode
Stdby
GND
1
7
GND
3
GND
TS4994IQ
Rfeed2
20k
GND VCC
GND VCC
3/35
Application component information
Figure 2.
TS4994
Typical application, MiniSO-8 version
VCC
+
Rfeed1
20k
7
Cs
1u
GND
VCC
Cin1
+
Diff. input -
220nF 20k
Cin2 Rin2
+
GND
Rin1
2 Vin-
-
3 Vin+
+
Vo+ 8
Vo5
220nF 20k
8 Ohms
4 Bypass
+
Diff. Input +
Optional
Bias
Cb
1u
Standby
Stdby
GND
1
6
GND
GND
TS4994IS
Rfeed2
20k
GND VCC
4/35
TS4994
Absolute maximum ratings and operating conditions
2
Absolute maximum ratings and operating conditions
Table 1.
Absolute maximum ratings
Symbol
VCC
Vi
Parameter
Supply voltage (1)
Input voltage
(2)
Value
Unit
6
V
GND to VCC
V
Toper
Operating free air temperature range
-40 to + 85
°C
Tstg
Storage temperature
-65 to +150
°C
150
°C
120
215
°C/W
internally limited
W
2
kV
Machine model
200
V
Latch-up immunity
200
mA
Lead temperature (soldering, 10sec)
260
°C
Value
Unit
Tj
Maximum junction temperature
Rthja
Thermal resistance junction to ambient
DFN10
MiniSO-8
Pdiss
Power dissipation
(3)
Human body model
ESD
1. All voltage values are measured with respect to the ground pin.
2. The magnitude of the 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
1.5 ≤ VSTBY ≤ VCC
GND ≤ VSTBY≤ 0.4 (1)
V
VSTBY
Standby voltage input:
Device ON (VSM = GND) or device OFF (VSM = VCC)
Device OFF (VSM = GND) or device ON (VSM = VCC)
TSD
Thermal shutdown temperature
150
°C
RL
Load resistor
≥8
Ω
Thermal resistance junction to ambient
DFN10 (2)
MiniSO-8
80
190
°C/W
Rthja
1. The minimum current consumption (ISTBY) is guaranteed when VSTBY = GND or VCC (i.e. supply rails) for the whole
temperature range.
2. When mounted on a 4-layer PCB.
5/35
Electrical characteristics
TS4994
3
Electrical characteristics
Table 3.
Electrical characteristics for VCC = +5V, GND = 0V, Tamb = 25°C (unless otherwise
specified)
Symbol
ICC
ISTBY
Voo
Parameter
Min.
Typ.
Max.
Unit
Supply current
No input signal, no load
4
7
mA
Standby current
No input signal, VSTBY = VSM = GND, RL = 8Ω
No input signal, VSTBY = VSM = VCC, RL = 8Ω
10
1000
nA
Differential output offset voltage
No input signal, RL = 8Ω
0.1
10
mV
VCC - 0.9
V
VICM
Input common mode voltage
CMRR ≤ -60dB
0.6
Pout
Output power
THD = 1% Max, F= 1kHz, RL = 8Ω
0.8
1
W
THD + N
Total harmonic distortion + noise
Pout = 850mW rms, AV = 1, 20Hz ≤ F ≤ 20kHz, RL = 8Ω
0.5
%
PSRRIG
Power supply rejection ratio with inputs grounded(1)
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
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
tWU
Wake-up time(2)
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.
6/35
μVRMS
ms
TS4994
Table 4.
Electrical characteristics
Electrical characteristics for 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
ICC
ISTBY
Voo
Parameter
Min.
Typ.
Max.
Unit
Supply current no input signal, no load
3
7
mA
Standby current
No input signal, VSTBY = VSM = GND, RL = 8Ω
No input signal, VSTBY = VSM = VCC, RL = 8Ω
10
1000
nA
Differential output offset voltage
No input signal, RL = 8Ω
0.1
10
mV
VCC - 0.9
V
VICM
Input common mode voltage
CMRR ≤ -60dB
0.6
Pout
Output power
THD = 1% max, F= 1kHz, RL = 8Ω
300
380
mW
THD + N
Total harmonic distortion + noise
Pout = 300mW rms, AV = 1, 20Hz ≤ F ≤ 20kHz, RL = 8Ω
0.5
%
PSRRIG
Power supply rejection ratio with inputs grounded(1)
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
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
tWU
Wake-up time(2)
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.
7/35
Electrical characteristics
Table 5.
Electrical characteristics for VCC = +2.6V, GND = 0V, Tamb = 25°C (unless otherwise
specified)
Symbol
ICC
ISTBY
Voo
TS4994
Parameter
Min.
Typ.
Max.
Unit
Supply current
No input signal, no load
3
7
mA
Standby current
No input signal, VSTBY = VSM = GND, RL = 8Ω
No input signal, VSTBY = VSM = VCC, RL = 8Ω
10
1000
nA
Differential output offset voltage
No input signal, RL = 8Ω
0.1
10
mV
VCC- 0.9
V
VICM
Input common mode voltage
CMRR ≤-60dB
0.6
Pout
Output power
THD = 1% max, F= 1kHz, RL = 8Ω
200
250
mW
THD + N
Total harmonic distortion + noise
Pout = 225mW rms, AV = 1, 20Hz ≤ F ≤ 20kHz, RL = 8Ω
0.5
%
PSRRIG
Power supply rejection ratio with inputs grounded(1)
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
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
tWU
Wake-up time(2)
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.
8/35
μVRMS
ms
TS4994
Electrical characteristics
Current consumption vs. power
supply voltage
Figure 4.
4.0
4.0
No load
3.5 Tamb=25°C
3.5
Current Consumption (mA)
Current Consumption (mA)
Figure 3.
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Current consumption vs. standby
voltage
3.0
Standby mode=0V
2.5
Standby mode=5V
2.0
1.5
1.0
Vcc = 5V
No load
Tamb=25°C
0.5
0
1
2
3
4
0.0
5
0
1
2
Power Supply Voltage (V)
Current consumption vs. power
supply voltage
Figure 6.
3.5
3.0
3.0
2.5
2.5
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
2.4
Current Consumption (mA)
Current Consumption (mA)
Figure 5.
4
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
3.0
Current consumption vs. standby
voltage
0.6
Standby Voltage (V)
Figure 7.
3
Standby Voltage (V)
1.2
1.8
2.4
Standby Voltage (V)
Differential DC output voltage vs.
common mode input voltage
Figure 8.
Power dissipation vs. output power
1000
Av = 1
Tamb = 25°C
Voo (mV)
Power Dissipation (W)
0.6
100
Vcc=3.3V
Vcc=2.5V
10
Vcc=5V
1
RL=8Ω
0.4
0.2
RL=16Ω
0.1
0.01
0.0
Vcc=5V
F=1kHz
THD+N<1%
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Common Mode Input Voltage (V)
4.5
5.0
0.0
0.0
0.2
0.4
0.6
Output Power (W)
0.8
1.0
9/35
Electrical characteristics
Figure 9.
TS4994
Power dissipation vs. output power
Figure 10. Power dissipation vs. output power
0.20
0.3
Power Dissipation (W)
Power Dissipation (W)
Vcc=2.6V
F=1kHz
THD+N<1%
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)
RL=8Ω
0.10
0.05
RL=16Ω
0.00
0.0
0.4
0.1
0.2
Figure 12. Output power vs. power supply
voltage
1.0
1.50
Cb = 1μF
F = 1kHz
BW < 125kHz
Tamb = 25°C
8Ω
Output power @ 10% THD + N (W)
0.8
16Ω
0.6
0.4
0.2
32Ω
0.0
2.5
3.0
3.5
4.0
4.5
1.25
1.00
8Ω
16Ω
0.75
0.50
0.25
0.00
2.5
5.0
Cb = 1μF
F = 1kHz
BW < 125kHz
Tamb = 25°C
32Ω
3.0
3.5
1.0
Output power (W)
0.8
THD+N=1%
Cb = 1 F
F = 1kHz
BW < 125kHz
Tamb = 25°C
Vcc=5V
Vcc=4.5V
0.6
Vcc=4V
0.4
0.2
Vcc=3.5V
Vcc=3V
10/35
8
12
Vcc=2.5V
16
20
24
Load Resistance
32
5.0
1.5
with 4 layers PCB
1.0
0.5
AMR Value
0.0
28
4.5
Figure 14. Power derating curves
DFN10 Package Power Dissipation (W)
Figure 13. Output power vs. load resistance
4.0
Vcc (V)
Vcc (V)
0.0
0.3
Output Power (W)
Figure 11. Output power vs. power supply
voltage
Output power @ 1% THD + N (W)
0.15
0
25
50
75
Ambiant Temperature ( C)
100
125
TS4994
Electrical characteristics
Figure 16. Open loop gain vs. frequency
0.6
0
60
Nominal Value
Gain
AMR Value
0.2
-80
20
Phase
-120
0
25
50
75
100
-40
0.1
125
1
10
100
1000
Figure 18. Open loop gain vs. frequency
0
0
60
60
Gain
Gain
-40
-40
Phase
-120
0
-160
Vcc = 3.3V
ZL = 8Ω + 500pF
Tamb = 25°C
1
10
100
1000
-80
20
Phase
-120
0
-40
0.1
-200
10000
-160
Vcc = 2.6V
ZL = 8Ω + 500pF
Tamb = 25°C
-20
1
10
100
Figure 19. Closed loop gain vs. frequency
Figure 20. Closed loop gain vs. frequency
0
10
0
10
Phase
Phase
-40
-20
-120
-40
0.1
Vcc = 5V
Av = 1
ZL = 8Ω + 500pF
Tamb = 25°C
1
-160
10
100
Frequency (kHz)
1000
-200
10000
Gain (dB)
-80
0
Phase (°)
Gain (dB)
Gain
-10
-30
-200
10000
Frequency (kHz)
Frequency (kHz)
0
1000
Gain
-40
-10
-80
-20
-120
-30
-40
0.1
Vcc = 3.3V
Av = 1
ZL = 8Ω + 500pF
Tamb = 25°C
1
Phase (°)
-40
0.1
Phase (°)
-80
20
Gain (dB)
40
Phase (°)
Gain (dB)
40
-20
-200
10000
Frequency (kHz)
Ambiant Temperature ( C)
Figure 17. Open loop gain vs. frequency
-160
Vcc = 5V
ZL = 8Ω + 500pF
Tamb = 25°C
-20
0
Phase (°)
0.4
0.0
-40
40
Gain (dB)
MiniSO8 Package Power Dissipation (W)
Figure 15. Power derating curves
-160
10
100
1000
-200
10000
Frequency (kHz)
11/35
Electrical characteristics
TS4994
Figure 21. Closed loop gain vs. frequency
Figure 22. PSRR vs. frequency
0
0
10
Phase
Gain
-30
-120
-20
PSRR (dB)
-80
-10
Vcc = 5V
Vripple = 200mVpp
Inputs = Grounded
Av = 1, Cin = 4.7μF
RL ≥ 8Ω
Tamb = 25°C
-20
-40
Phase (°)
0
Gain (dB)
-10
-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
10
100
1000
-120
Frequency (kHz)
Figure 23. PSRR vs. frequency
PSRR (dB)
-40
-50
-30
Cb=0.1μF
-60
Cb=0.47μF
-70
Cb=1μF
-80
-40
-50
10000 20k
Cb=0.1μF
-60
Cb=0.47μF
-70
Cb=1μF
-80
-90
-90
-100
-100
Cb=0
-110
Cb=0
-110
20
100
1000
Frequency (Hz)
-120
10000 20k
Figure 25. PSRR vs. frequency
20
100
1000
Frequency (Hz)
10000 20k
Figure 26. PSRR vs. frequency
0
0
-10
Vcc = 5V
Vripple = 200mVpp
Inputs = Grounded
Av = 2.5, Cin = 4.7μF
RL ≥ 8Ω
Tamb = 25°C
-20
-30
-40
-50
-30
Cb=0.1μF
Cb=0.47μF
-60
-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)
1000
Frequency (Hz)
Vcc = 2.6V
Vripple = 200mVpp
Inputs = Grounded
Av = 1, Cin = 4.7μF
RL ≥ 8Ω
Tamb = 25°C
-20
PSRR (dB)
-30
-40
-50
Cb=0.1μF
Cb=0.47μF
-60
-70
Cb=1μF
-80
-90
-90
Cb=0
-100
-110
12/35
100
0
-10
Vcc = 3.3V
Vripple = 200mVpp
Inputs = Grounded
Av = 1, Cin = 4.7μF
RL ≥ 8Ω
Tamb = 25°C
-20
-120
20
Figure 24. PSRR vs. frequency
0
-10
-120
Cb=0
-110
-200
10000
Cb=0
-100
-110
20
100
1000
Frequency (Hz)
10000 20k
-120
20
100
1000
Frequency (Hz)
10000 20k
TS4994
Electrical characteristics
Figure 27. PSRR vs. frequency
Figure 28. PSRR vs. frequency
0
0
-20
-30
-40
PSRR (dB)
-10
Vcc = 2.6V
Vripple = 200mVpp
Inputs = Grounded
Av = 2.5, Cin = 4.7μF
RL ≥ 8Ω
Tamb = 25°C
-50
-30
Cb=0.1μF
Cb=0.47μF
-60
-70
Cb=1μF
-80
-40
-50
Cb=1μF
-90
Cb=0
-100
-110
Cb=0
-110
20
100
-120
10000 20k
1000
Frequency (Hz)
Figure 29. PSRR vs. frequency
20
100
10000 20k
1000
Frequency (Hz)
Figure 30. PSRR vs. frequency
0
0
-10
Vcc = 3.3V
Vripple = 200mVpp
Inputs = Floating
Rfeed = 20kΩ
RL ≥ 8Ω
Tamb = 25°C
-20
-30
-40
-50
-30
Cb=0.1μF
-60
Cb=0.47μF
-70
Cb=1μF
-80
Vcc = 2.6V
Vripple = 200mVpp
Inputs = Floating
Rfeed = 20kΩ
RL ≥ 8Ω
Tamb = 25°C
-20
-40
PSRR (dB)
-10
PSRR (dB)
Cb=0.47μF
-70
-80
-100
-50
Cb=0.1μF
-60
Cb=0.47μF
-70
Cb=1μF
-80
-90
-90
-100
-100
Cb=0
-110
-120
Cb=0.1μF
-60
-90
-120
Vcc = 5V
Vripple = 200mVpp
Inputs = Floating
Rfeed = 20kΩ
RL ≥ 8Ω
Tamb = 25°C
-20
PSRR (dB)
-10
Cb=0
-110
20
100
10000 20k
1000
Frequency (Hz)
Figure 31. PSRR vs. common mode input
voltage
-120
20
100
10000 20k
1000
Frequency (Hz)
Figure 32. PSRR vs. common mode input
voltage
0
-40
-20
PSRR(dB)
-20
PSRR(dB)
0
Vcc = 5V
Vripple = 200mVpp
Inputs Grounded
F = 217Hz
Av = 1
RL ≥ 8Ω
Tamb = 25°C
Cb=1μF
Cb=0.47μF
Cb=0.1μF
-60
-40
Vcc = 3.3V
Vripple = 200mVpp
Inputs Grounded
F = 217Hz
Av = 1
RL ≥ 8Ω
Tamb = 25°C
-60
Cb=0
Cb=0
-80
-80
-100
-100
0
1
2
3
4
Common Mode Input Voltage (V)
5
0.0
Cb=1μF
Cb=0.47μF
Cb=0.1μF
0.6
1.2
1.8
2.4
3.0
Common Mode Input Voltage (V)
13/35
Electrical characteristics
TS4994
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
-50
-60
-70
-90
-100
-110
0.5
1.0
1.5
2.0
-120
2.5
20
100
Common Mode Input Voltage (V)
Figure 35. CMRR vs. frequency
-40
-50
Vcc = 2.6V
Vic = 200mVpp
Av = 1, Cin = 470μF
RL ≥ 8Ω
Tamb = 25°C
-20
-30
Cb=1μF
Cb=0.47μF
Cb=0.1μF
Cb=0
-60
CMRR (dB)
CMRR (dB)
-30
-70
-80
-40
Cb=1μF
Cb=0.47μF
Cb=0.1μF
Cb=0
-50
-60
-70
-80
-90
-90
-100
-100
-110
-110
20
100
1000
Frequency (Hz)
-120
10000 20k
Figure 37. CMRR vs. frequency
20
100
1000
Frequency (Hz)
10000 20k
Figure 38. CMRR vs. frequency
0
0
Vcc = 5V
Vic = 200mVpp
Av = 2.5, Cin = 470μF
RL ≥ 8Ω
Tamb = 25°C
-20
-30
-40
-20
-30
Cb=1μF
Cb=0.47μF
Cb=0.1μF
Cb=0
-50
-60
-70
Vcc = 3.3V
Vic = 200mVpp
Av = 2.5, Cin = 470μF
RL ≥ 8Ω
Tamb = 25°C
-10
CMRR (dB)
-10
CMRR (dB)
10000 20k
0
-10
Vcc = 3.3V
Vic = 200mVpp
Av = 1, Cin = 470μF
RL ≥ 8Ω
Tamb = 25°C
-20
-40
Cb=1μF
Cb=0.47μF
Cb=0.1μF
Cb=0
-50
-60
-70
-80
-80
-90
-90
-100
-100
14/35
1000
Frequency (Hz)
Figure 36. CMRR vs. frequency
0
-10
-120
Cb=1μF
Cb=0.47μF
Cb=0.1μF
Cb=0
-80
-100
0.0
Vcc = 5V
Vic = 200mVpp
Av = 1, Cin = 470μF
RL ≥ 8Ω
Tamb = 25°C
-20
CMRR (dB)
0
Figure 34. CMRR vs. frequency
20
100
1000
Frequency (Hz)
10000 20k
20
100
1000
Frequency (Hz)
10000 20k
TS4994
Electrical characteristics
Figure 39. CMRR vs. frequency
Figure 40. CMRR vs. common mode input
voltage
0
-30
-40
Vcc=3.3V
-20
CMRR(dB)
-20
CMRR (dB)
0
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
Vcc=2.5V
Vic = 200mVpp
F = 217Hz
Av = 1, Cb = 1μF
RL ≥ 8Ω
Tamb = 25°C
-40
-60
-80
-80
-100
-90
-100
20
100
0.0
10000 20k
1000
Frequency (Hz)
Vcc=5V
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 41. CMRR vs. common mode input
voltage
Figure 42. THD+N vs. output power
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
-80
Vcc=3.3V
Vcc=5V
0.1
Vcc=5V
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)
Figure 43. THD+N vs. output power
1
10
Vcc=2.6V
Vcc=3.3V
THD + N (%)
RL = 8Ω
F = 20Hz
Av = 2.5
1
Cb = 1μF
BW < 125kHz
Tamb = 25°C
0.01
0.1
Output Power (W)
Figure 44. THD+N vs. output power
10
THD + N (%)
Vcc=2.6V
0.01
-100
0.0
RL = 8Ω
F = 20Hz
Av = 1
1
Cb = 1μF
BW < 125kHz
Tamb = 25°C
Vcc=5V
0.1
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
0.01
0.01
1E-3
1E-3
0.01
0.1
Output Power (W)
1
1E-3
0.01
0.1
Output Power (W)
1
15/35
Electrical characteristics
TS4994
Figure 45. THD+N vs. output power
Figure 46. THD+N vs. output power
10
10
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.1
0.01
1E-3
RL = 8Ω
F = 1kHz
Av = 2.5
1 Cb = 1μF
BW < 125kHz
Tamb = 25°C
THD + N (%)
THD + N (%)
RL = 8Ω
F = 1kHz
Av = 1
1 Cb = 1μF
BW < 125kHz
Tamb = 25°C
Vcc=5V
0.1
0.01
0.1
Output Power (W)
1
1E-3
0.01
0.1
Output Power (W)
1
Figure 48. THD+N vs. output power
10
10
Vcc=2.6V
Vcc=3.3V
THD + N (%)
THD + N (%)
Vcc=3.3V
0.01
Figure 47. THD+N vs. output power
RL = 8Ω
F = 1kHz
Av = 7.5
1 Cb = 1μF
BW < 125kHz
Tamb = 25°C
Vcc=2.6V
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
Figure 49. THD+N vs. output power
1E-3
10
RL = 8Ω
F = 20kHz
Av = 7.5
Cb = 1μF
BW < 125kHz
Tamb = 25°C
Vcc=2.6V
THD + N (%)
THD + N (%)
1
Figure 50. THD+N vs. output power
10
RL = 8Ω
F = 20kHz
Av = 2.5
Cb = 1μF
BW < 125kHz
1 Tamb = 25°C
0.01
0.1
Output Power (W)
Vcc=3.3V
Vcc=5V
1
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.1
1E-3
16/35
0.01
0.1
Output Power (W)
1
0.1
1E-3
0.01
0.1
Output Power (W)
1
TS4994
Electrical characteristics
Figure 51. THD+N vs. output power
Figure 52. 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 = 20Hz
1 Av = 7.5
Cb = 1μF
BW < 125kHz
Tamb = 25°C
0.1
Vcc=2.6V
Vcc=3.3V
THD + N (%)
THD + N (%)
10
Vcc=5V
Vcc=2.6V
Vcc=3.3V
Vcc=5V
0.01
0.01
1E-3
1E-3
0.01
0.1
Output Power (W)
1
Figure 53. THD+N vs. output power
1E-3
1E-3
10
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 (%)
1
Figure 54. THD+N vs. output power
10
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
0.1
0.01
0.01
1E-3
1E-3
0.01
0.1
Output Power (W)
1
Figure 55. THD+N vs. output power
1E-3
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
10
RL = 16Ω
F = 20kHz
Av = 1
Cb = 1μF
1
BW < 125kHz
Tamb = 25°C
0.01
0.1
Output Power (W)
Vcc=5V
Vcc=2.6V
Vcc=3.3V
Vcc=5V
1
0.1
0.01
1E-3
0.01
0.1
Output Power (W)
1
0.1
1E-3
0.01
0.1
Output Power (W)
1
17/35
Electrical characteristics
TS4994
Figure 57. THD+N vs. output power
Figure 58. THD+N vs. output power
10
10
F=20kHz
THD + N (%)
THD + N (%)
1
RL = 8Ω
Vcc = 5V
Av = 1
Cb = 0
BW < 125kHz
Tamb = 25°C
F=1kHz
0.1
RL = 8Ω
Vcc = 2.6V
Av = 1, Cb = 0
1
BW < 125kHz
Tamb = 25°C
F=20kHz
F=1kHz
0.1
F=20Hz
0.01
0.01
F=20Hz
1E-3
0.01
0.1
Output Power (W)
1E-3
1E-3
1
Figure 59. THD+N vs. output power
10
RL = 16Ω
Vcc = 5V
Av = 1, Cb = 0
1
BW < 125kHz
Tamb = 25°C
THD + N (%)
F=20kHz
F=1kHz
0.1
RL = 16Ω
Vcc = 2.6V
Av = 1, Cb = 0
1
BW < 125kHz
Tamb = 25°C
F=1kHz
F=20Hz
0.01
1E-3
1E-3
0.01
0.1
Output Power (W)
1E-3
1E-3
1
Figure 61. THD+N vs. frequency
0.1
10
Vcc=2.6V, Po=225mW
THD + N (%)
RL = 8Ω
Av = 1
Cb = 1μF
1
Bw < 125kHz
Tamb = 25°C
THD + N (%)
0.01
Output Power (W)
Figure 62. THD+N vs. frequency
10
0.1
0.01
RL = 8Ω
Av = 1
Cb = 0
1
Bw < 125kHz
Tamb = 25°C
Vcc=2.6V, Po=225mW
0.1
0.01
Vcc=5V, Po=850mW
18/35
F=20kHz
0.1
F=20Hz
0.01
1E-3
0.1
Figure 60. THD+N vs. output power
10
THD + N (%)
0.01
Output Power (W)
20
100
1000
Frequency (Hz)
10000 20k
Vcc=5V, Po=850mW
1E-3
20
100
1000
Frequency (Hz)
10000 20k
TS4994
Electrical characteristics
Figure 63. THD+N vs. frequency
Figure 64. THD+N vs. frequency
10
RL = 8Ω
Av = 7.5
Cb = 1μF
Bw < 125kHz
1 Tamb = 25°C
Vcc=2.6V, Po=225mW
THD + N (%)
THD + N (%)
10
0.1
RL = 8Ω
Av = 7.5
Cb = 0
Bw < 125kHz
1 Tamb = 25°C
Vcc=2.6V, Po=225mW
0.1
Vcc=5V, Po=850mW
0.01
20
100
Vcc=5V, Po=850mW
0.01
10000 20k
1000
Frequency (Hz)
Figure 65. THD+N vs. frequency
100
10
RL = 16Ω
Av = 1
Cb = 1μF
1
Bw < 125kHz
Tamb = 25°C
RL = 16Ω
Av = 7.5
Cb = 1μF
1
Bw < 125kHz
Tamb = 25°C
THD + N (%)
Vcc=2.6V, Po=155mW
0.1
Vcc=2.6V, Po=155mW
0.1
0.01
0.01
Vcc=5V, Po=600mW
1E-3
10000 20k
1000
Frequency (Hz)
Figure 66. THD+N vs. frequency
10
THD + N (%)
20
20
100
Vcc=5V, Po=600mW
10000 20k
1000
Frequency (Hz)
1E-3
20
100
10000 20k
1000
Frequency (Hz)
Figure 67. SNR vs. power supply voltage with Figure 68. SNR vs. power supply voltage with
unweighted filter
A-weighted filter
110
110
105
Signal to Noise Ratio (dB)
Signal to Noise Ratio (dB)
RL=16Ω
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
Power Supply Voltage (V)
4.5
5.0
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)
19/35
Electrical characteristics
TS4994
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
20/35
Vcc=2.6V
0.4
0.8
1.2
1.6
Bypass Capacitor Cb ( F)
2.0
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
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:
●
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:
●
4.2
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 Figure 1 and Figure 2 on page 4.
In the flat region of the frequency-response curve (no Cin effect), the differential gain is
expressed by the relation:
AV
diff
R feed
V O+ – V O
- = ------------= ----------------------------------------------------Diff input+ – Diff inputR in
where Rin = Rin1 = Rin2 and Rfeed = Rfeed1 = Rfeed2.
Note:
For the rest of this section, 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 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 VCC, Rin and Rfeed (AV). To have a good estimation of the VICM value, use the
following formula:
V CC × R in + 2 × V ic × R feed
V ICM = -------------------------------------------------------------------------2 × ( R in + R feed )
(V)
with
Diff input+ + Diff inputV ic = ------------------------------------------------------2
(V)
The result of the calculation must be in the range:
0.6V ≤V ICM ≤ V CC – 0.9V
If the result of the VICM calculation is not in this range, an input coupling capacitor must be
used.
Example: With VCC=2.5V, Rin = Rfeed = 20k and Vic = 2V, we find VICM = 1.63V. This is
higher than 2.5V - 0.9V = 1.6V, so input coupling capacitors are required. Alternatively, you
can 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.
FCL =
1
2 × π × Rin × Cin
(Hz)
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.
FCH =
1
2 × π × Rfeed × Cfeed
(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 FCL = 50Hz
and FCH = 8kHz. We assume that the mismatching between Rin1,2 and Cfeed1,2 can be
neglected. If we sweep the frequency from DC to 20kHz we observe the following with
respect to the PSRR value:
●
22/35
From DC to 200Hz, the Cin impedance decreases from infinite to a finite value and the
Cfeed impedance is high enough to be neglected. Due to the tolerance of Cin1,2, we
TS4994
Application information
must introduce a mismatch factor (Rin1 x Cin ≠ Rin2 x Cin2) that will decrease the PSRR
performance.
4.5
●
From 200Hz to 5kHz, the Cin impedance is low enough to be neglected when
compared with Rin, and the Cfeed 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 Cin impedance is low to be neglected when compared to Rin,
and the Cfeed impedance decreases to a finite value. Due to tolerance of Cfeed1,2, we
introduce a mismatching factor (Rfeed1 x Cfeed1 ≠ Rfeed2 x Cfeed2) that will decrease the
PSRR performance.
Calculating the influence of mismatching on PSRR
performance
For calculating PSRR performance, we consider that Cin and Cfeed have no influence.
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 %):
⎡ ΔR × 100 ⎤
PSRR ≤ 20 × Log ⎢
2 ⎥
⎣ (10000 − ΔR ) ⎦
(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 (ΔR in %, Cb in microFarad and F in Hz) is:
ΔR × 100
PSRR ≤20 × log --------------------------------------------------------------------------------------------------------- ( dB )
2
2
2
(1000 – ΔR ) × 1 + F × C b × 22.2
Example: With ΔR = 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. 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 Cb in
worst-case conditions (ΔR = 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
ΔR/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
PSRR (dB)
Figure 72. PSRR vs. frequency (worst case
conditions)
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
24/35
Vcc = 2.5V, Vripple = 200mVpp
Av = 1, Cin = 4.7μF
ΔR/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
conditions)
PSRR (dB)
PSRR (dB)
Figure 70. PSRR vs. frequency (worst case
conditions)
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
ΔR/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
TS4994
Application information
The two following graphs show typical applications of the TS4994 with a random selection of
four ΔR/R values with a 0.1% tolerance.
4.6
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
ΔR/R ≤ 0.1%, RL ≥ 8Ω
Tamb = 25°C, Inputs = Grounded
Cb=0.1μF
Cb=1μF
20
100
PSRR (dB)
PSRR (dB)
Figure 73. PSRR vs. frequency with random
choice condition
Cb=0
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
ΔR/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 calculating CMRR performance, we consider that Cin and Cfeed have no influence. Cb
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 %):
⎡ Δ R × 200
⎤
CMRR ≤ 20 × Log ⎢
2 ⎥
⎣ (10000 − Δ R ) ⎦
(dB )
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 Cb in
worst-case conditions (ΔR=0.1%).
25/35
Application information
TS4994
Figure 75. CMR vs. frequency (worst case
conditions)
Figure 76. CMR vs. frequency (worst case
conditions)
0
0
Vcc = 5V
Vic = 200mVpp
Av = 1, Cin = 470μF
ΔR/R = 0.1%, RL ≥ 8Ω
Tamb = 25°C
-20
-30
-40
-20
-30
-40
Cb=1μF
Cb=0
-50
-60
Vcc = 2.5V
Vic = 200mVpp
Av = 1, Cin = 470μF
ΔR/R = 0.1%, RL ≥ 8Ω
Tamb = 25°C
-10
CMRR (dB)
CMRR (dB)
-10
Cb=1μF
Cb=0
-50
20
100
1000
Frequency (Hz)
-60
10000 20k
20
100
1000
Frequency (Hz)
10000 20k
Figure 77 and Figure 78 show CMRR versus frequency for a typical application with a
random selection of four ΔR/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
0
0
Vcc = 5V
Vic = 200mVpp
Av = 1, Cin = 470μF
ΔR/R ≤ 0.1%, RL ≥ 8Ω
Tamb = 25°C
CMRR (dB)
-20
-30
Cb=1μF
Cb=0
-60
-30
-40
-50
-70
-80
-80
20
100
1000
Frequency (Hz)
Cb=1μF
Cb=0
-60
-70
-90
4.7
-20
-40
-50
Vcc = 2.5V
Vic = 200mVpp
Av = 1, Cin = 470μF
ΔR/R ≤ 0.1%, RL ≥ 8Ω
Tamb = 25°C
-10
CMRR (dB)
-10
10000 20k
-90
20
100
Power dissipation and efficiency
Assumptions:
●
Load voltage and current are sinusoidal (Vout and Iout)
●
Supply voltage is a pure DC source (VCC)
The output voltage is:
V out = V peak sinωt (V)
and
V out
I out = ------------- (A)
RL
26/35
1000
Frequency (Hz)
10000 20k
TS4994
Application information
and
V peak 2
P out = --------------------- (W)
2R L
Therefore, the average current delivered by the supply voltage is:
Equation 1
V peak
I CC AVG = 2 ----------------- (A)
πR L
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
2 2V CC
P diss = ---------------------- P out – P out
π RL
and the maximum value is obtained when:
∂P diss
----------------- = 0
∂P out
and its value is:
Equation 3
Pdiss max =
Note:
2 Vcc 2
π2RL
(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
P out
πV peak
η = ------------------- = -------------------P supply
4V CC
The maximum theoretical value is reached when VPEAK = VCC, so:
π
η = ----- = 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
TS4994
To calculate the maximum ambient temperature Tamb allowable, you need to know:
●
The value of the power supply voltage, VCC
●
The value of the load resistor, RL
●
The Rthja value for the package type
Example: VCC = 5V, RL = 8Ω, Rthja = 80°C/W
Using the power dissipation formula given above in Equation 3 this gives a result of:
Pdissmax = 633mW
Tamb is calculated as follows:
Equation 5
T amb = 125° C – R TJHA × P dissmax
Therefore, the maximum allowable value for Tamb is:
Tamb = 125-80x0.633=74°C
4.8
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 performance to that 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, the 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).
4.9
Wake-up time: tWU
When the standby is released to put the device ON, the bypass capacitor Cb is not 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 Table 3 on page 6, with Cb=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 Cb 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
4.10
Application information
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, the Bypass pin and Vin+, Vin- pins are short-circuited to ground by
internal switches. This allows a quick discharge of the Cb and Cin capacitors.
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 Rin, Rfeed, and external input
capacitors Cin, 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.
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
VCC
+
Rfeed1
20k
7
Cs
1u
GND
VCC
Cin1
+
Ve
Rin1
+
220nF 20k
Cin2 Rin2
GND
2 Vin-
-
3 Vin+
+
Vo+ 8
Vo5
220nF 20k
8 Ohms
4 Bypass
Optional
+
4.12
Bias
Cb
1u
Standby
Stdby
GND
1
6
GND
GND
TS4994IS
Rfeed2
20k
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 =
4.13
VO + − VO − Rfeed
=
Ve
Rin
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
5.1
TS4994
DFN10 package
Dimensions
Ref.
Millimeters
Min.
Typ.
Max.
Min.
Typ.
Max.
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
A
b
0.18
D
D2
E2
2.21
0.30
7.1
2.26
1.49
1.64
2.31
87.0
0.4
11.8
89.0
91.0
118.1
1.74
58.7
0.50
0.3
9.1
118.1
3.00
e
L
0.23
3.00
E
32/35
Mils
64.6
68.5
19.7
0.5
11.8
15.7
19.7
TS4994
5.2
Package mechanical data
MiniSO-8 package
Dimensions
Ref.
Millimeters
Min.
Typ.
A
Inches
Max.
Min.
Typ.
1.1
Max.
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
K
0°
L
0.40
L1
0.55
0.026
6°
0°
0.70
0.016
0.10
6°
0.022
0.028
0.04
33/35
Revision history
6
34/35
TS4994
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.
TS4994
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35/35