TS4998
2 x 1W differential input stereo audio amplifier
Features
QFN16 4x4mm
■
Operating range from VCC= 2.7V to 5.5V
■
1W output power per channel @ VCC=5V,
THD+N=1%, RL=8Ω
■
Ultra low standby consumption: 10nA typ.
■
80dB PSRR @ 217Hz with grounded inputs
■
High SNR: 106dB(A) typ.
■
Fast startup time: 45ms typ.
■
Pop&click-free circuit
■
Dedicated standby pin per channel
■
Lead-free QFN16 4x4mm package
Cellular mobile phones
■
Notebook and PDA computers
■
LCD monitors and TVs
■
Portable audio devices
Description
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Pin connections (top view)
Applications
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The TS4998 is designed for top-class stereo
audio applications. Thanks to its compact and
power-dissipation efficient QFN16 package with
exposed pad, it suits a variety of applications.
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With a BTL configuration, this audio power
amplifier is capable of delivering 1W per channel
of continuous RMS output power into an 8Ω load
@ 5V.
Each output channel (left and right), also has its
own external controlled standby mode pin to
reduce the supply current to less than 10nA per
channel. The device also features an internal
thermal shutdown protection.
The gain of each channel can be configured by
external gain setting resistors.
December 2007
Rev 1
1/33
www.st.com
33
Contents
TS4998
Contents
1
Typical application schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4
Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
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General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.2
Differential configuration principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.3
Gain in typical application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.4
Common mode feedback loop limitations . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.5
Low frequency response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.6
Power dissipation and efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.7
Footprint recommendation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.8
Decoupling of the circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.9
Standby control and wake-up time tWU
4.10
Shutdown time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.11
Pop performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.12
Single-ended input configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.13
Notes on PSRR measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
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4.1
QFN16 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
TS4998
1
Typical application schematics
Typical application schematics
Figure 1 shows a typical application for the TS4998 with a gain of +6dB set by the input
resistors.
Figure 1.
Typical application schematics
VCC
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Optional
Diff. input L-
13
1uF
U1
Cin1
Rin1
330nF
25k
TS4998
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Vcc
P1
4
RIN-
3
RIN+
LEFT
Diff. input R-
Cin3
Rin3
330nF
25k
P3
Cin4
Rin4
330nF
25k
)
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14
Bypass
BIAS
GND
1uF
Cb
GND
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Table 1.
LOUT+
11
-
ROUT-
9
+
ROUT+
10
Left Speaker
8 Ohms
Right Speaker
8 Ohms
STBY
STBYL Control
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RIGHT
P4
Diff. input R+
ete
+
STBYL
25k
8
330nF
6
Diff. input L+
12
STBYR
LIN+
-
7
2
Rin2
P2
Pr
LOUT-
TS4998 - QFN16
STBYR Control
LIN-
5
Cin2
1
External component descriptions
Components
Functional description
RIN
Input resistors that set the closed loop gain in conjunction with a fixed internal
feedback resistor (Gain = Rfeed/RIN, where Rfeed = 50kΩ).
CIN
Input coupling capacitors that block the DC voltage at the amplifier input
terminal. Thanks to common mode feedback, these input capacitors are
optional. However, if they are added, they form with RIN a 1st order high pass
filter with -3dB cut-off frequency (fcut-off = 1 / (2 x π x RIN x CIN)).
CS
Supply bypass capacitors that provides power supply filtering.
CB
Bypass pin capacitor that provides half supply filtering.
3/33
Absolute maximum ratings
2
TS4998
Absolute maximum ratings
Table 2.
Absolute maximum ratings
Symbol
Parameter
Value
Unit
6
V
GND to VCC
V
Supply voltage (1)
VCC
Vin
Input voltage
(2)
Toper
Operating free air temperature range
-40 to + 85
°C
Tstg
Storage temperature
-65 to +150
°C
Maximum junction temperature
150
°C
Thermal resistance junction to ambient
120
Tj
Rthja
Power dissipation
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°C/W
Internally limited
ESD
Human body model (3)
Digital pins STBYL, STBYR
ESD
Machine model
let
Latch-up immunity
1. All voltage values are measured with respect to the ground pin.
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200
V
200
mA
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2
1.5
2. The magnitude of the input signal must never exceed VCC + 0.3V / GND - 0.3V.
3. All voltage values are measured from each pin with respect to supplies.
Table 3.
Symbol
Supply voltage
VICM
Common mode input voltage range
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RL
4/33
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Parameter
VCC
VSTBY
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Operating conditions
Standby voltage input:
Device ON
Device OFF
Load resistor
ROUT/GND Output resistor to GND (VSTBY = GND)
Value
Unit
2.7 to 5.5
V
GND to VCC - 1V
V
1.3 ≤ VSTBY ≤ VCC
GND ≤ VSTBY ≤0.4
V
≥4
Ω
≥1
MΩ
TSD
Thermal shutdown temperature
150
°C
Rthja
Thermal resistance junction to ambient
QFN16(1)
QFN16(2)
45
85
°C/W
1.
When mounted on a 4-layer PCB with vias.
2.
When mounted on a 2-layer PCB with vias.
TS4998
Electrical characteristics
3
Electrical characteristics
Table 4.
VCC = +5V, GND = 0V, Tamb = 25°C (unless otherwise specified)
Symbol
Typ.
Max.
Unit
Supply current
No input signal, no load, left and right channel active
7.4
9.6
mA
Standby current (1)
No input signal, VSTBYL = GND, VSTBYR = GND, RL = 8Ω
10
2000
nA
Voo
Output offset voltage
No input signal, RL = 8Ω
1
35
mV
Po
Output power
THD = 1% max, F = 1kHz, RL = 8Ω
ICC
ISTBY
THD + N
PSRR
CMRR
Parameter
Crosstalk
Power supply rejection ratio(2), inputs grounded
RL = 8Ω, G = 6dB, Cb = 1µF, Vripple = 200mVpp
F = 217Hz
F = 1kHz
Common mode rejection ratio(3)
RL = 8Ω, G = 6dB, Cb = 1µF, Vincm = 200mVpp
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57
Channel separation, RL = 8Ω, G = 6dB
F = 1kHz
F = 20Hz to 20kHz
Pr
108
dB
105
80
dB
Output voltage noise, F = 20Hz to 20kHz, RL = 8Ω, G=6dB
Cb = 1µF
µVrms
15
10
Unweighted
A-weighted
40
kΩ
----------------
%
dB
80
75
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1000
0.5
Signal-to-noise ratio
A-weighted, G = 6dB, Cb = 1µF, RL = 8Ω
(THD + N ≤ 0.5%, 20Hz < F < 20kHz)
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VN
800
Total harmonic distortion + noise
Po = 700mWrms, G = 6dB, RL = 8Ω, 20Hz ≤ F ≤ 20kHz
F = 217Hz
F = 1kHz
SNR
Min.
50
kΩ
----------------
60
kΩ
----------------
Gain
Gain value (RIN in kΩ)
tWU
Wake-up time (Cb = 1µF)
46
ms
tSTBY
Standby time (Cb = 1µF)
10
µs
ΦM
Phase margin at unity gain
RL = 8Ω, CL = 500pF
65
Degrees
GM
Gain margin, RL = 8Ω, CL = 500pF
15
dB
GBP
Gain bandwidth product, RL = 8Ω
1.5
MHz
R IN
R IN
R IN
V/V
1. Standby mode is active when VSTBY is tied to GND.
2. Dynamic measurements - 20*log(rms(Vout)/rms(Vripple)). Vripple is the sinusoidal signal superimposed upon VCC.
3. Dynamic measurements - 20*log(rms(Vout)/rms(Vincm)).
5/33
Electrical characteristics
Table 5.
TS4998
VCC = +3.3V, GND = 0V, Tamb = 25°C (unless otherwise specified)
Symbol
Typ.
Max.
Unit
Supply current
No input signal, no load, left and right channel active
6.6
8.6
mA
Standby current (1)
No input signal, VSTBYL = GND, VSTBYR = GND, RL = 8Ω
10
2000
nA
Voo
Output offset voltage
No input signal, RL = 8Ω
1
35
mV
Po
Output power
THD = 1% max, F = 1kHz, RL = 8Ω
ICC
ISTBY
THD + N
Parameter
Min.
370
Total harmonic distortion + noise
Po = 300mWrms, G = 6dB, RL = 8Ω, 20Hz ≤ F ≤ 20kHz
460
CMRR
Power supply rejection
inputs grounded
RL = 8Ω, G = 6dB, Cb = 1µF, Vripple = 200mVpp
F = 217Hz
F = 1kHz
SNR
Crosstalk
Signal-to-noise ratio
A-weighted, G = 6dB, Cb = 1µF, RL = 8Ω
(THD + N ≤ 0.5%, 20Hz < F < 20kHz)
)
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104
dB
105
80
dB
Output voltage noise, F = 20Hz to 20kHz, RL = 8Ω, G=6dB
Cb = 1µF
VN
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Gain
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Unweighted
A-weighted
Gain value (RIN in kΩ)
µVrms
15
10
40
kΩ
---------------R IN
dB
dB
57
57
Channel separation, RL = 8Ω, G = 6dB
F = 1kHz
F = 20Hz to 20kHz
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%
80
75
Common mode rejection ratio(3)
RL = 8Ω, G = 6dB, Cb = 1µF, Vincm = 200mVpp
F = 217Hz
F = 1kHz
)
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0.5
ratio(2),
PSRR
mW
50
kΩ
---------------R IN
60
kΩ
---------------R IN
V/V
tWU
Wake-up time (Cb = 1µF)
47
ms
tSTBY
Standby time (Cb = 1µF)
10
µs
ΦM
Phase margin at unity gain
RL = 8Ω, CL = 500pF
65
Degrees
GM
Gain margin, RL = 8Ω, CL = 500pF
15
dB
GBP
Gain bandwidth product, RL = 8Ω
1.5
MHz
1. Standby mode is active when VSTBY is tied to GND.
2. Dynamic measurements - 20*log(rms(Vout)/rms(Vripple)). Vripple is the sinusoidal signal superimposed upon VCC.
3. Dynamic measurements - 20*log(rms(Vout)/rms(Vincm)).
6/33
TS4998
Table 6.
Electrical characteristics
VCC = +2.7V, GND = 0V, Tamb = 25°C (unless otherwise specified)
Symbol
Typ.
Max.
Unit
Supply current
No input signal, no load, left and right channel active
6.2
8.1
mA
Standby current (1)
No input signal, VSTBYL = GND, VSTBYR = GND, RL = 8Ω
10
2000
nA
Voo
Output offset voltage
No input signal, RL = 8Ω
1
35
mV
Po
Output power
THD = 1% max, F = 1kHz, RL = 8Ω
ICC
ISTBY
THD + N
Parameter
Min.
220
Total harmonic distortion + noise
Po = 200mWrms, G = 6dB, RL = 8Ω, 20Hz ≤ F ≤ 20kHz
295
CMRR
Power supply rejection
inputs grounded
RL = 8Ω, G = 6dB, Cb = 1µF, Vripple = 200mVpp
F = 217Hz
F = 1kHz
SNR
Crosstalk
Signal-to-noise ratio
A-weighted, G = 6dB, Cb = 1µF, RL = 8Ω
(THD + N ≤ 0.5%, 20Hz < F < 20kHz)
)
(s
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102
dB
105
80
dB
Output voltage noise, F = 20Hz to 20kHz, RL = 8Ω, G=6dB
Cb = 1µF
VN
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Gain
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Pr
Unweighted
A-weighted
Gain value (RIN in kΩ)
µVrms
15
10
40
kΩ
---------------R IN
dB
dB
57
57
Channel separation, RL = 8Ω, G = 6dB
F = 1kHz
F = 20Hz to 20kHz
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%
76
73
Common mode rejection ratio(3)
RL = 8Ω, G = 6dB, Cb = 1µF, Vincm = 200mVpp
F = 217Hz
F = 1kHz
)
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0.5
ratio(2),
PSRR
mW
50
kΩ
---------------R IN
60
kΩ
---------------R IN
V/V
tWU
Wake-up time (Cb = 1µF)
46
ms
tSTBY
Standby time (Cb = 1µF)
10
µs
ΦM
Phase margin at unity gain
RL = 8Ω, CL = 500pF
65
Degrees
GM
Gain margin, RL = 8Ω, CL = 500pF
15
dB
GBP
Gain bandwidth product, RL = 8Ω
1.5
MHz
1. Standby mode is active when VSTBY is tied to GND.
2. Dynamic measurements - 20*log(rms(Vout)/rms(Vripple)). Vripple is the sinusoidal signal superimposed upon VCC.
3. Dynamic measurements - 20*log(rms(Vout)/rms(Vincm)).
7/33
Electrical characteristics
Table 7.
TS4998
Index of graphics
Description
Figure
THD+N vs. output power
Figure 2 to 13
page 9 to page 10
THD+N vs. frequency
Figure 14 to 19
page 11
PSRR vs. frequency
Figure 20 to 28
page 12 to page 13
PSRR vs. common mode input voltage
Figure 29
page 13
CMRR vs. frequency
Figure 30 to 35
page 13 to page 14
CMRR vs. common mode input voltage
Figure 36
page 14
Crosstalk vs. frequency
Figure 37 to 39
page 14 to page 15
SNR vs. power supply voltage
Figure 40 to 45
page 15 to page 16
Differential DC output voltage vs. common mode input
voltage
Figure 46 to 48
page 16
Current consumption vs. power supply voltage
Figure 49
Current consumption vs. standby voltage
Figure 50 to 52
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Standby current vs. power supply voltage
Figure 53
Frequency response
Output power vs. load resistance
Output power vs. power supply voltage
Power dissipation vs. output power
)
(s
Power derating curves
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Page
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page 17
page 17
Figure 54 to 56
page 17 to page 18
Figure 57
page 18
Figure 58 to 59
page 18
Figure 60 to 62
page 18 to page 19
Figure 63
page 19
TS4998
Figure 2.
Electrical characteristics
THD+N vs. output power
Figure 3.
10
RL = 4 Ω
G = +6dB
F = 1kHz
Cb = 1 μ F
1 BW < 125kHz
Tamb = 25 ° C
Vcc=3.3V
Vcc=2.7V
0.1
0.01
1E-3
RL = 4 Ω
G = +12dB
F = 1kHz
Cb = 1 μ F
1 BW < 125kHz
Tamb = 25 ° C
Vcc=5V
THD + N (%)
THD + N (%)
10
THD+N vs. output power
0.01
0.1
Vcc=3.3V
Vcc=2.7V
0.1
0.01
1E-3
1
Vcc=5V
0.01
Output power (W)
Figure 4.
THD+N vs. output power
Vcc=5V
Vcc=3.3V
Vcc=2.7V
)
(s
0.1
0.01
1E-3
0.01
t
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0.1
THD + N (%)
THD + N (%)
THD+N vs. output power
RL = 8 Ω
G = +12dB
F = 1kHz
Cb = 1 μ F
1 BW < 125kHz
Tamb = 25 ° C
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0.01
P
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RL = 16 Ω
G = +6dB
F = 1kHz
Cb = 1 μ F
1 BW < 125kHz
Tamb = 25 ° C
Figure 7.
Vcc=5V
Vcc=3.3V
Vcc=2.7V
0.1
0.01
1E-3
0.01
1
THD+N vs. output power
10
THD + N (%)
THD + N (%)
O
bs
0.1
Output power (W)
THD+N vs. output power
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Vcc=3.3V
Vcc=2.7V
0.01
1E-3
1
Vcc=5V
0.1
Output power (W)
Figure 6.
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P
10
RL = 8 Ω
G = +6dB
F = 1kHz
Cb = 1 μ F
1 BW < 125kHz
Tamb = 25 ° C
1
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Figure 5.
10
)
s
(
t
0.1
Output power (W)
0.1
Output power (W)
1
RL = 16 Ω
G = +12dB
F = 1kHz
Cb = 1 μ F
1 BW < 125kHz
Tamb = 25 ° C
Vcc=5V
Vcc=3.3V
Vcc=2.7V
0.1
0.01
1E-3
0.01
0.1
1
Output power (W)
9/33
Electrical characteristics
Figure 8.
TS4998
THD+N vs. output power
Figure 9.
10
10
RL = 4 Ω
G = +6dB
F = 10kHz
Cb = 1 μ F
1 BW < 125kHz
Tamb = 25 ° C
Vcc=3.3V
Vcc=2.7V
0.1
0.01
1E-3
RL = 4 Ω
G = +12dB
F = 10kHz
Cb = 1 μ F
1 BW < 125kHz
Tamb = 25 ° C
Vcc=5V
THD + N (%)
THD + N (%)
THD+N vs. output power
0.01
0.1
Vcc=3.3V
Vcc=2.7V
0.1
0.01
1E-3
1
Vcc=5V
0.01
Output power (W)
Figure 11. THD+N vs. output power
10
Vcc=2.7V
)
(s
0.01
t
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0.1
RL = 8 Ω
G = +12dB
F = 10kHz
Cb = 1 μ F
1 BW < 125kHz
Tamb = 25 ° C
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Output power (W)
P
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Vcc=5V
Vcc=3.3V
Vcc=2.7V
0.01
0.1
Output power (W)
10/33
0.1
1
10
0.1
0.01
1E-3
0.01
Figure 13. THD+N vs. output power
THD + N (%)
O
THD + N (%)
bs
Vcc=2.7V
Output power (W)
Figure 12. THD+N vs. output power
RL = 16 Ω
G = +6dB
F = 10kHz
Cb = 1 μ F
1 BW < 125kHz
Tamb = 25 ° C
Vcc=3.3V
0.1
0.01
1E-3
1
Vcc=5V
so
Vcc=3.3V
THD + N (%)
THD + N (%)
Vcc=5V
0.1
10
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10
0.01
1E-3
1
c
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Figure 10. THD+N vs. output power
RL = 8 Ω
G = +6dB
F = 10kHz
Cb = 1 μ F
1 BW < 125kHz
Tamb = 25 ° C
)
s
(
t
0.1
Output power (W)
1
RL = 16 Ω
G = +12dB
F = 10kHz
Cb = 1 μ F
1 BW < 125kHz
Tamb = 25 ° C
Vcc=5V
Vcc=3.3V
Vcc=2.7V
0.1
0.01
1E-3
0.01
0.1
Output power (W)
1
TS4998
Electrical characteristics
Figure 14. THD+N vs. frequency
10
10
RL = 4 Ω
G = +6dB
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
Vcc=5V
Pout=950mW
1
Vcc=3.3V
Pout=430mW
THD + N (%)
THD + N (%)
1
Figure 15. THD+N vs. frequency
0.1
RL = 4 Ω
G = +12dB
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
Vcc=5V
Pout=950mW
Vcc=3.3V
Pout=430mW
0.1
Vcc=2.7V
Pout=260mW
Vcc=2.7V
Pout=260mW
0.01
100
1000
0.01
10000
100
Frequency (Hz)
Figure 16. THD+N vs. frequency
10
Vcc=5V
Pout=700mW
1
O
)
Vcc=2.7V
Pout=200mW
s
(
t
c
du
100
1000
t
e
l
o
0.01
10000
o
r
P
100
0.01
THD + N (%)
THD + N (%)
RL = 16 Ω
G = +12dB
Cb = 1 μ F
BW < 125kHz
1 Tamb = 25 ° C
Vcc=5V
Pout=450mW
Vcc=3.3V
Pout=200mW
Vcc=2.7V
Pout=120mW
100
10000
10
RL = 16 Ω
G = +6dB
Cb = 1 μ F
BW < 125kHz
1 Tamb = 25 ° C
0.1
1000
Figure 19. THD+N vs. frequency
10
O
Vcc=3.3V
Pout=300mW
Frequency (Hz)
Figure 18. THD+N vs. frequency
bs
Vcc=5V
Pout=700mW
Vcc=2.7V
Pout=200mW
0.1
Frequency (Hz)
e
t
e
ol
u
d
o
r
P
e
RL = 8 Ω
G = +12dB
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
bs
Vcc=3.3V
Pout=300mW
THD + N (%)
THD + N (%)
RL = 8 Ω
G = +6dB
Cb = 1 μ F
BW < 125kHz
1 Tamb = 25 ° C
0.01
10000
Figure 17. THD+N vs. frequency
10
0.1
)
s
(
ct
1000
Frequency (Hz)
1000
Frequency (Hz)
10000
Vcc=5V
Pout=450mW
Vcc=3.3V
Pout=200mW
Vcc=2.7V
Pout=120mW
0.1
0.01
100
1000
10000
Frequency (Hz)
11/33
Electrical characteristics
TS4998
Figure 20. PSRR vs. frequency
Figure 21. PSRR vs. frequency
0
-20
-30
PSRR (dB)
-40
0
Vcc = 5V
Vripple = 200mVpp
G = +6dB
Cb = 1 μ F, Cin = 4.7 μ F
Inputs Grounded
Tamb = 25 ° C
-20
-30
-50
-60
-40
-50
-60
-70
-70
-80
-80
-90
-90
-100
Vcc = 5V
Vripple = 200mVpp
G = +12dB
Cb = 1 μ F, Cin = 4.7 μ F
Inputs Grounded
Tamb = 25 ° C
-10
PSRR (dB)
-10
100
1000
-100
10000
100
Frequency (Hz)
Figure 22. PSRR vs. frequency
Figure 23. PSRR vs. frequency
0
-20
-30
-10
-30
PSRR (dB)
-50
-60
)-
-70
-90
c
u
d
100
1000
s
b
O
-40
-50
-60
-70
t(s
-80
-100
r
P
e
Vcc = 3.3V
Vripple = 200mVpp
G = +6dB
Cb = 1 μ F, Cin = 4.7 μ F
Inputs Grounded
Tamb = 25 ° C
t
e
l
o
-20
-40
-80
-90
-100
10000
100
1000
Frequency (Hz)
Frequency (Hz)
Figure 24. PSRR vs. frequency
Figure 25. PSRR vs. frequency
e
t
e
ol
o
r
P
0
bs
-20
-40
PSRR (dB)
O
-30
-10
-20
-30
-50
-60
-60
-70
-80
-90
-90
1000
Frequency (Hz)
12/33
-50
-80
100
10000
Vcc = 3.3V
Vripple = 200mVpp
Cb = 1 μ F
Inputs Floating
Tamb = 25 ° C
-40
-70
-100
10000
0
Vcc = 3.3V
Vripple = 200mVpp
G = +12dB
Cb = 1 μ F, Cin = 4.7 μ F
Inputs Grounded
Tamb = 25 ° C
PSRR (dB)
-10
10000
u
d
o
0
Vcc = 5V
Vripple = 200mVpp
Cb = 1 μ F
Inputs Floating
Tamb = 25 ° C
PSRR (dB)
-10
)
s
(
ct
1000
Frequency (Hz)
-100
100
1000
Frequency (Hz)
10000
TS4998
Electrical characteristics
Figure 26. PSRR vs. frequency
Figure 27. PSRR vs. frequency
0
-20
-30
PSRR (dB)
-40
0
Vcc = 2.7V
Vripple = 200mVpp
G = +6dB
Cb = 1 μ F, Cin = 4.7 μ F
Inputs Grounded
Tamb = 25 ° C
-20
-30
-50
-60
-40
-50
-60
-70
-70
-80
-80
-90
-90
-100
Vcc = 2.7V
Vripple = 200mVpp
G = +12dB
Cb = 1 μ F, Cin = 4.7 μ F
Inputs Grounded
Tamb = 25 ° C
-10
PSRR (dB)
-10
100
1000
-100
10000
100
Frequency (Hz)
Figure 29. PSRR vs. common mode input
voltage
0
-30
Vcc = 2.7V
Vripple = 200mVpp
Cb = 1 μ F
Inputs Floating
Tamb = 25 ° C
-20
PSRR (dB)
s
b
O
-30
-50
)
(s
-60
-70
t
c
u
-80
-90
-100
od
100
1000
r
P
e
-40
-50
-80
-90
-20
-30
let
1
2
3
4
5
Figure 31. CMRR vs. frequency
0
Vcc = 5V
RL ≥ 8 Ω
G = +6dB
Vic = 200mVpp
Cb = 1 μ F, Cin = 4.7 μ F
Tamb = 25°C
-10
-20
-40
-30
-50
-60
-60
100
1000
Frequency (Hz)
10000
Vcc = 5V
RL ≥ 8 Ω
G = +12dB
Vic = 200mVpp
Cb = 1 μ F, Cin = 4.7 μ F
Tamb = 25°C
-40
-50
-70
0
Common Mode Input Voltage (V)
CMRR (dB)
CMRR (dB)
b
O
Vcc=5V
-70
10000
Figure 30. CMRR vs. frequency
-10
Vcc=3.3V
Vcc=2.7V
-60
Frequency (Hz)
so
t
e
l
o
Vripple = 200mVpp
F = 217Hz, G = +6dB
Cb = 1 μ F, RL ≥ 8 Ω
Tamb = 25°C
-10
-40
0
r
P
e
0
PSRR (dB)
-20
10000
u
d
o
Figure 28. PSRR vs. frequency
-10
)
s
(
ct
1000
Frequency (Hz)
-70
100
1000
10000
Frequency (Hz)
13/33
Electrical characteristics
TS4998
Figure 32. CMRR vs. frequency
Figure 33. CMRR vs. frequency
0
0
Vcc = 3.3V
RL ≥ 8 Ω
G = +6dB
Vic = 200mVpp
Cb = 1 μ F, Cin = 4.7 μ F
Tamb = 25°C
CMRR (dB)
-20
-30
-10
-20
CMRR (dB)
-10
-40
-30
-40
-50
-50
-60
-60
-70
100
1000
Vcc = 3.3V
RL ≥ 8 Ω
G = +12dB
Vic = 200mVpp
Cb = 1 μ F, Cin = 4.7 μ F
Tamb = 25°C
-70
10000
100
Frequency (Hz)
Figure 34. CMRR vs. frequency
-30
-10
-20
-40
)-
-50
-70
du
100
1000
t
e
l
o
-30
-40
-50
s
(
t
c
-60
Vcc = 2.7V
RL ≥ 8 Ω
G = +12dB
Vic = 200mVpp
Cb = 1 μ F, Cin = 4.7 μ F
Tamb = 25°C
s
b
O
CMRR (dB)
-20
CMRR (dB)
r
P
e
0
Vcc = 2.7V
RL ≥ 8 Ω
G = +6dB
Vic = 200mVpp
Cb = 1 μ F, Cin = 4.7 μ F
Tamb = 25°C
-60
-70
10000
100
Frequency (Hz)
o
r
P
s
b
O
10
0
Vripple = 200mVpp
F = 217Hz, G = +6dB
Cb = 1 μ F, RL ≥ 8 Ω
Tamb = 25°C
0
-10
-20
CMRR (dB)
-10
-20
-30
Vcc=3.3V
Vcc=2.7V
-40
-50
-60
Vcc=5V
-40
-50
Vcc=5V
Vcc=3.3V
Vcc=2.7V
-60
-70
-80
-90
-110
-120
0
1
2
3
Common Mode Input Voltage (V)
14/33
-30
RL = 4 Ω
G = +6dB
Cin = 1 μ F, Cb = 1 μ F
Tamb = 25 ° C
-100
-70
-80
10000
Figure 37. Crosstalk vs. frequency
Crosstalk Level (dB)
20
1000
Frequency (Hz)
Figure 36. CMRR vs. common mode input
voltage
e
t
e
ol
10000
u
d
o
Figure 35. CMRR vs. frequency
0
-10
)
s
(
ct
1000
Frequency (Hz)
4
5
100
1000
Frequency (Hz)
10000
TS4998
Electrical characteristics
Figure 38. Crosstalk vs. frequency
Figure 39. Crosstalk vs. frequency
0
Crosstalk Level (dB)
-20
-30
0
RL = 8 Ω
G = +6dB
Cin = 1 μ F, Cb = 1 μ F
Tamb = 25 ° C
-10
-20
Crosstalk Level (dB)
-10
-40
-50
Vcc=5V
Vcc=3.3V
Vcc=2.7V
-60
-70
-80
-90
-30
-40
-50
-70
-80
-90
-100
-110
-110
100
1000
Vcc=5V
Vcc=3.3V
Vcc=2.7V
-60
-100
-120
RL = 16 Ω
G = +6dB
Cin = 1 μ F, Cb = 1 μ F
Tamb = 25 ° C
-120
10000
100
108
106
106
104
102
100
)-
A - Weighted filter
F = 1kHz
G = +6dB, RL = 4 Ω
THD + N < 0.5%
Tamb = 25 ° C
92
90
2.5
3.0
3.5
4.0
d
o
r
uc
t(s
4.5
5.0
Singnal to Noise Ratio (dB)
Singnal to Noise Ratio (dB)
110
108
98
u
d
o
Figure 41. SNR vs. power supply voltage
110
94
r
P
e
t
e
l
o
104
s
b
O
102
100
98
A - weighted filter
F = 1kHz
G = +6dB ,RL = 8 Ω
THD + N < 0.5%
Tamb = 25 ° C
96
94
92
90
2.5
5.5
3.0
Supply Voltage (V)
108
P
e
t
e
l
o
102
100
98
A - Weighted filter
F = 1kHz
G = +6dB ,RL = 16 Ω
THD + N < 0.5%
Tamb = 25 ° C
96
94
92
3.0
5.0
5.5
108
104
90
2.5
4.5
110
Singnal to Noise Ratio (dB)
Singnal to Noise Ratio (dB)
O
4.0
Figure 43. SNR vs. power supply voltage
bs
106
3.5
Supply Voltage (V)
Figure 42. SNR vs. power supply voltage
110
10000
Frequency (Hz)
Figure 40. SNR vs. power supply voltage
96
)
s
(
ct
1000
Frequency (Hz)
3.5
4.0
4.5
Supply Voltage (V)
5.0
106
104
102
100
98
Unweighted filter (20Hz to 20kHz)
F = 1kHz
G = +6dB, RL = 4 Ω
THD + N < 0.5%
Tamb = 25 ° C
96
94
92
5.5
90
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Supply Voltage (V)
15/33
Electrical characteristics
TS4998
Figure 45. SNR vs. power supply voltage
110
110
108
108
106
106
Singnal to Noise Ratio (dB)
Singnal to Noise Ratio (dB)
Figure 44. SNR vs. power supply voltage
104
102
100
98
Unweighted filter (20Hz to 20kHz)
F = 1kHz
G = +6dB, RL = 8 Ω
THD + N < 0.5%
Tamb = 25 ° C
96
94
92
90
2.5
3.0
3.5
4.0
4.5
5.0
104
102
100
98
Unweighted filter (20Hz to 20kHz)
F = 1kHz
G = +6dB, RL = 16 Ω
THD + N < 0.5%
Tamb = 25 ° C
96
94
92
90
2.5
5.5
3.0
3.5
Supply Voltage (V)
s
b
O
)
(s
0.1
ct
0.01
u
d
o
2
3
|Voo| (mV)
|Voo| (mV)
e
t
e
ol
10
1
4
1
0.1
0.01
5
r
P
e
1E-3
0.0
0.5
Common Mode Input Voltage (V)
let
2.0
2.5
3.0
No load
Tamb = 25 ° C
Current Consumption (mA)
7
10
|Voo| (mV)
1.5
Figure 49. Current consumption vs. power
supply voltage
8
1000 Vcc = 2.7V
G = +6dB
Tamb = 25 ° C
100
O
1.0
Common Mode Input Voltage (V)
Figure 48. Differential DC output voltage vs.
common mode input voltage
o
s
b
5.5
o
r
P
1000 Vcc = 3.3V
G = +6dB
Tamb = 25 ° C
100
10
1
5.0
Figure 47. Differential DC output voltage vs.
common mode input voltage
1000 Vcc = 5V
G = +6dB
Tamb = 25 ° C
100
0
)
s
(
t
4.5
c
u
d
Figure 46. Differential DC output voltage vs.
common mode input voltage
1E-3
4.0
Supply Voltage (V)
1
0.1
0.01
6
5
Both channels active
4
3
2
One channel active
1
1E-3
0.0
0.5
1.0
1.5
2.0
Common Mode Input Voltage (V)
16/33
2.5
0
0
1
2
3
4
Power Supply Voltage (V)
5
TS4998
Electrical characteristics
Figure 51. Current consumption vs. standby
voltage
8
7
7
6
6
Current Consumption (mA)
Current Consumption (mA)
Figure 50. Current consumption vs. standby
voltage
Both channels active
5
4
3
One channel active
2
Vcc = 5V
No load
Tamb = 25 ° C
1
0
0
1
2
3
4
5
Both channels active
4
3
One channel active
2
Vcc = 3.3V
No load
Tamb = 25 ° C
0
0.0
5
0.5
1.0
4
3
)-
s
(
t
c
One channel active
2
u
d
o
0.5
Pr
1.0
1.5
Standby Current (nA)
Current Consumption (mA)
Both channels active
Vcc = 2.7V
No load
Tamb = 25 ° C
2.0
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
2.5
0
1
Figure 54. Frequency response
bs
Cin=4.7 μ F, Rin=12k Ω
Cin=680nF, Rin=12k Ω
Cin=4.7 μ F, Rin=24k Ω
Cin=330nF, Rin=24k Ω
20
100
1000
Frequency (Hz)
3
4
5
Figure 55. Frequency response
Gain (dB)
Gain (dB)
O
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
2
Power Supply Voltage (V)
Standby Voltage (V)
e
t
e
ol
r
P
e
s
b
O
0.8
5
3.0
t
e
l
o
No load
0.9 Tamb = 25 ° C
6
2.5
Figure 53. Standby current vs. power supply
voltage
1.0
0
0.0
2.0
Standby Voltage (V)
7
1
1.5
u
d
o
Standby Voltage (V)
Figure 52. Current consumption vs. standby
voltage
)
s
(
ct
1
Vcc = 5V
Po = 700mW
ZL = 8 Ω + 500pF
Tamb = 25 ° C
10000 20k
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Cin=4.7 μ F, Rin=12k Ω
Cin=680nF, Rin=12k Ω
Cin=4.7 μ F, Rin=24k Ω
Cin=330nF, Rin=24k Ω
20
100
1000
Vcc = 3.3V
Po = 300mW
ZL = 8 Ω + 500pF
Tamb = 25 ° C
10000 20k
Frequency (Hz)
17/33
Electrical characteristics
TS4998
Figure 56. Frequency response
1800
Cin=4.7 μ F, Rin=12k Ω
Vcc=5V
1400
Cin=680nF, Rin=12k Ω
Cin=4.7 μ F, Rin=24k Ω
Vcc = 2.7V
Po = 200mW
ZL = 8 Ω + 500pF
Tamb = 25 ° C
Cin=330nF, Rin=24k Ω
20
100
Vcc=4.5V
1200
Vcc=4V
1000
Vcc=3.3V
800
Vcc=3V
600
400
200
0
10000 20k
1000
Vcc=2.7V
4
8
12
16
RL=4 Ω
1200
1000
)-
RL=8 Ω
600
t(s
RL=16 Ω
400
uc
200
0
2.5
3.0
od
3.5
4.0
r
P
e
4.5
RL=32 Ω
5.0
Output power at 10% THD + N (mW)
Output power at 1% THD + N (mW)
e
t
e
ol
2200
800
28
32
Figure 59. Output power vs. power supply
voltage
1800
1400
)
s
(
t
24
c
u
d
Figure 58. Output power vs. power supply
voltage
1600
20
Load Resistance (Ω )
Frequency (Hz)
F = 1kHz
Cb = 1 μ F
BW < 125 kHz
Tamb = 25 ° C
THD+N = 1%
F = 1kHz
Cb = 1 μ F
BW < 125kHz
Tamb = 25 ° C
Vcc=5.5V
1600
Output power (mW)
Gain (dB)
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Figure 57. Output power vs. load resistance
2000
1800
F = 1kHz
Cb = 1 μ F
BW < 125 kHz
Tamb = 25 ° C
o
r
P
s
b
O
1600
1400
RL=4 Ω
1200
1000
RL=8 Ω
800
600
RL=16 Ω
400
RL=32 Ω
200
0
2.5
5.5
3.0
3.5
Vcc (V)
4.0
4.5
5.0
5.5
Vcc (V)
t
e
l
o
Figure 60. Power dissipation vs. output power Figure 61. Power dissipation vs. output power
600
O
Power Dissipation (mW)
bs
550
500
RL=4 Ω
RL=8 Ω
RL=16 Ω
Vcc = 5V
F = 1kHz
THD+N < 1%
0
200
400
600
800
1000 1200 1400 1600
Output Power (mW)
18/33
Power Dissipation (mW)
1500
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
RL=4 Ω
450
400
350
RL=8 Ω
300
250
200
RL=16 Ω
150
Vcc = 3.3V
F = 1kHz
THD+N < 1%
100
50
0
0
100
200
300
400
500
Output Power (mW)
600
700
TS4998
Electrical characteristics
Figure 62. Power dissipation vs. output power Figure 63. Power derating curves
Power Dissipation (mW)
350
RL=4 Ω
300
250
RL=8 Ω
200
150
RL=16 Ω
100
Vcc = 2.7V
F = 1kHz
THD+N < 1%
50
0
0
50
100
150
200
250
300
350
400
450
QFN16 Package Power Dissipation (W)
400
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Mounted on 4-layer PCB
with vias
Mounted on 2-layer PCB
with vias
No Heat sink -AMR value
0
25
50
75
)
s
(
t
100
Ambiant Temperature (° C)
125
150
c
u
d
Output Power (mW)
e
t
e
ol
)
(s
o
r
P
s
b
O
t
c
u
d
o
r
P
e
t
e
l
o
s
b
O
19/33
Application information
TS4998
4
Application information
4.1
General description
The TS4998 integrates two monolithic full-differential input/output power amplifiers with two
selectable standby pins dedicated for each channel. The gain of each channel is set by
external input resistors.
4.2
Differential configuration principle
The TS4998 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 maximum
output voltage swing, and therefore, to maximize the output power. Moreover, as the load is
connected differentially instead of single-ended, output power is four times higher for the
same power supply voltage.
)
s
(
ct
u
d
o
r
P
e
The advantages of a full-differential amplifier are:
●
High PSRR (power supply rejection ratio),
●
High common mode noise rejection,
●
Virtually no pops&clicks without additional circuitry, giving a faster startup time
compared to conventional single-ended input amplifiers,
●
Easier interfacing with differential output audio DAC,
●
No input coupling capacitors required due to common mode feedback loop.
)
(s
t
e
l
o
s
b
O
In theory, the filtering of the internal bias by an external bypass capacitor is not necessary.
However, to reach maximum performance in all tolerance situations, it is recommended to
keep this option.
t
c
u
The only constraint is that the differential function is directly linked to external resistor
mismatching, therefore you must pay particular attention to this mismatching in order to
obtain the best performance from the amplifier.
d
o
r
Gain
t in typical application schematic
e
l
o
4.3
bs
O
P
e
A typical differential application is shown in Figure 1 on page 3.
The value of the differential gain of each amplifier is dependent on the values of external
input resistors RIN1 to RIN4 and of integrated feedback resistors with fixed value. In the flat
region of the frequency-response curve (no CIN effect), the differential gain of each channel
is expressed by the relation given in Equation 1.
Equation 1
AV
diff
R feed
V O+ – V O- = ------------= ----------------------------------------------------- = 50kΩ
-------------Diff input+ – Diff inputR IN
R IN
where RIN = RIN1 = RIN2 = RIN3 = RIN4 expressed in kΩ and Rfeed = 50kΩ (value of internal
feedback resistors).
20/33
TS4998
Application information
Due to the tolerance on the internal 50kΩ feedback resistors, the differential gain will be in
the range (no tolerance on RIN):
40kΩ
-------------- ≤A V ≤60kΩ
-------------diff
R IN
R IN
The difference of resistance between input resistors of each channel have direct influence
on the PSRR, CMRR and other amplifier parameters. In order to reach maximum
performance, we recommend matching the input resistors RIN1, RIN2, RIN3, and RIN4 with a
maximum tolerance of 1%.
Note:
For the rest of this section, Avdiff will be called AV to simplify the mathematical expressions.
4.4
Common mode feedback loop limitations
)
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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.
u
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Due to the VICM limitation of the input stage (see Table 3 on page 4), the common mode
feedback loop can fulfil its role only within the defined range. This range depends upon the
values of VCC, RIN and Rfeed (AV). To have a good estimation of the VICM value, use the
following formula:
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Equation 2
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V CC × R IN + 2 × V ic × 50kΩ
V CC × R IN + 2 × V ic × R feed
V ICM = --------------------------------------------------------------------------- = --------------------------------------------------------------------------- ( V )
2 × ( R IN + R feed )
2 × ( R IN + 50kΩ)
)
(s
with VCC in volts, RIN in kΩ and
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Diff input+ + Diff inputV ic = ------------------------------------------------------2
(V)
The result of the calculation must be in the range:
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GND ≤ V ICM ≤ V CC – 1V
Due to the +/-20% tolerance on the 50kΩ feedback resistors Rfeed (no tolerance on RIN), it is
also important to check that the VICM remains in this range at the tolerance limits:
V CC × R IN + 2 × V ic × 60kΩ
V CC × R IN + 2 × V ic × 40kΩ
------------------------------------------------------------------------- ≤V ICM ≤-------------------------------------------------------------------------(V)
2 × ( R IN + 40kΩ)
2 × ( R IN + 60kΩ)
If the result of the VICM calculation is not in this range, an input coupling capacitor must be
used.
Example: VCC = 2.7V, AV = 2, and Vic = 2.2V.
With internal resistors Rfeed = 50kΩ, calculated external resistors are RIN = Rfeed/AV = 25kΩ,
VCC = 2.7V and Vic = 2.2V, which gives VICM = 1.92V. Taking into account the tolerance on
the feedback resistors, with Rfeed = 40kΩ the common mode input voltage is VICM = 1.87V
and with Rfeed = 60kΩ, it is VICM = 1.95V.
These values are not in range from GND to VCC - 1V = 1.7V, therefore input coupling
capacitors are required. Alternatively, you can change the Vic value.
21/33
Application information
4.5
TS4998
Low frequency response
The input coupling capacitors block the DC part of the input signal at the amplifier inputs. In
the low frequency region, CIN starts to have an effect. CIN and RIN form a first-order high
pass filter with a -3dB cut-off frequency.
1
F CL = ----------------------------------------------- ( Hz )
2 × π × R IN × C IN
with RIN expressed in Ω and CIN expressed in F.
So, for a desired -3dB cut-off frequency we can calculate CIN:
1
C IN = ------------------------------------------------ ( F )
2 × π × R IN × F CL
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From Figure 64, you can easily establish the CIN value required for a -3 dB cut-off frequency
for some typical cases.
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Figure 64. -3dB lower cut-off frequency vs. input capacitance
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Low -3dB Cut Off Frequency (Hz)
Tamb=25 ° C
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100
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Rin=6.2k Ω
G~18dB
10
0.1
Rin=12k Ω
G~12dB
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Rin=24k Ω
G~6dB
0.2
0.4
Input Capacitor Cin ( μ F)
0.6
0.8
1
TS4998
4.6
Application information
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
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and
V peak 2
P out = --------------------- (W)
2R L
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Therefore, the average current delivered by the supply voltage is:
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Equation 3
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V peak
I ccAVG = 2 ----------------- (A)
πR L
)
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The power delivered by the supply voltage is:
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Equation 4
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Psupply = VCC IccAVG (W)
Therefore, the power dissipated by each amplifier is:
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Pdiss = Psupply - Pout (W)
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2 2V CC
P diss = ---------------------- P out – P out ( W )
π RL
and the maximum value is obtained when:
∂Pdiss
--------------------- = 0
∂P out
and its value is:
Equation 5
Pdiss max =
Note:
2 Vcc2
π2RL
(W)
This maximum value is only dependent on the power supply voltage and load values.
23/33
Application information
TS4998
The efficiency is the ratio between the output power and the power supply:
Equation 6
P out
πV peak
η = ------------------- = -------------------P supply
4Vcc
The maximum theoretical value is reached when Vpeak = VCC, so:
η = π----- = 78.5%
4
The TS4998 is stereo amplifier so it has two power amplifiers. Each amplifier produces heat
due to its power dissipation. Therefore, the maximum die temperature is the sum of each
amplifier’s maximum power dissipation. It is calculated as follows:
●
Pdiss 1 = Power dissipation of left channel power amplifier
●
Pdiss 2 = Power dissipation of right channel power amplifier
●
Total Pdiss =Pdiss 1 + Pdiss 2 (W)
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In most cases, Pdiss 1 = Pdiss 2, giving:
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4 2V CC
TotalP diss = 2 × P diss1 = ---------------------- P out – 2P out ( W )
π RL
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The maximum die temperature allowable for the TS4998 is 150°C. In case of overheating, a
thermal shutdown protection set to 150°C, puts the TS4998 in standby until the temperature
of the die is reduced by about 5°C.
)
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To calculate the maximum ambient temperature Tamb allowable, you need to know:
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●
the power supply voltage value, VCC
●
the load resistor value, RL
●
the package type, RTHJA
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Example: VCC=5V, RL=8Ω, RTHJAQFN16=85°C/W (with 2-layer PCB with vias).
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Using the power dissipation formula given in Equation 5, the maximum dissipated power per
channel is:
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Pdissmax = 633mW
And the power dissipated by both channels is:
Total Pdissmax = 2 x Pdissmax = 1266mW
Tamb is calculated as follows:
Equation 7
T amb = 150° C – R TJHA × TotalPdissmax
Therefore, the maximum allowable value for Tamb is:
Tamb = 150 - 85 x 2 x 1.266=42.4°C
If a 4-layer PCB with vias is used, RTHJAQFN16 = 45°C/W and the maximum allowable
value for Tamb in this case is:
Tamb = 150 - 45 x 2 x 1.266 = 93°C
24/33
TS4998
4.7
Application information
Footprint recommendation
Footprint soldering pad dimensions are given in Figure 72 on page 30. As discussed in the
previous section, the maximum allowable value for ambient temperature is dependent on
the thermal resistance junction to ambient RTHJA. Decreasing the RTHJA value causes better
power dissipation.
Based on best thermal performance, it is recommended to use 4-layer PCBs with vias to
effectively remove heat from the device. It is also recommended to use vias for 2-layer PCBs
to connect the package exposed pad to heatsink cooper areas placed on another layer.
For proper thermal conductivity, the vias must be plated through and solder-filled. Typical
thermal vias have the following dimensions: 1.2mm pitch, 0.3mm diameter.
)
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Figure 65. QFN16 footprint recommendation
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4.8
Decoupling of the circuit
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Two capacitors are needed to correctly bypass the TS4998: a power supply bypass
capacitor CS and a bias voltage bypass capacitor Cb.
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The CS capacitor has particular influence on the THD+N at high frequencies (above 7kHz)
and an indirect influence on power supply disturbances. With a value for CS of 1µF, one can
expect THD+N performance similar to that shown in the datasheet.
In the high frequency region, if CS is lower than 1µF, then THD+N increases and
disturbances on the power supply rail are less filtered.
On the other hand, if CS is greater than 1µF, then those disturbances on the power supply
rail are more filtered.
The Cb capacitor has an influence on the THD+N at lower frequencies, but also impacts
PSRR performance (with grounded input and in the lower frequency region).
25/33
Application information
4.9
TS4998
Standby control and wake-up time tWU
The TS4998 has two dedicated standby pins (STBYL, STBYR). These pins allow to put
each channel in standby mode or active mode independently. The amplifier is designed to
reach close to zero pop when switching from one mode to the other.
When both channels are in standby (VSTBYL = VSTBYR = GND), the circuit is in shutdown
mode. When at least one of the two standby pins is released to put the device ON, the
bypass capacitor Cb starts to be charged. Because 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 4 on page 5, with Cb=1µF.
During the wake-up phase, the TS4998 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 different from 1µF, then refer
to the graph in Figure 66 to establish the corresponding wake-up time.
)
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When a channel is set to standby mode, the outputs of this channel are in high impedance
state.
Figure 66. Typical startup time vs. bypass capacitor
100
90
Startup Time (ms)
70
Vcc=2.7V
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Vcc=5V
40
30
0.0
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4.10
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Vcc=3.3V
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Tamb=25 ° C
80
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0.5
1.0
1.5
2.0
2.5 3.0
3.5
Bypass Capacitor Cb (μ F)
4.0
4.5
Shutdown time
When the standby command is activated (both channels put into standby mode), the time
required to put the two output stages of each channel in high impedance and the internal
circuitry in shutdown mode is a few microseconds.
Note:
In shutdown mode when both channels are in standby, the Bypass pin and LIN+, LIN-, RIN+,
RIN- pins are shorted to ground by internal switches. This allows a quick discharge of Cb and
CIN capacitors.
4.11
Pop performance
Due to its fully differential structure, the pop performance of the TS4998 is close to perfect.
However, due to mismatching between internal resistors Rfeed, external resistors RIN and
26/33
TS4998
Application information
external input capacitors CIN, some noise might remain at startup. To eliminate the effect of
mismatched components, the TS4998 includes pop reduction circuitry. With this circuitry,
the TS4998 is close to zero pop for all possible common applications.
In addition, when the TS4998 is in standby mode, due to the high impedance output stage in
this configuration, no pop is heard.
4.12
Single-ended input configuration
It is possible to use the TS4998 in a single-ended input configuration. However, input
coupling capacitors are needed in this configuration. The schematic diagram in Figure 67
shows an example of this configuration for a gain of +6dB set by the input resistors.
)
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Figure 67. Typical single-ended input application
VCC
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Cs
Pr
1uF
13
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U1
Cin1
Rin1
330nF
25k
Cin2
Rin2
TS4998
Vcc
P1
25k
Cin3
Rin3
4
RIN-
3
RIN+
25k
-
LOUT-
12
+
LOUT+
11
-
ROUT-
9
+
ROUT+
10
Left Speaker
8 Ohms
Right Speaker
RIGHT
8 Ohms
Rin4
25k
s
b
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GND
1uF
Cb
STBY
GND
STBYR
BIAS
7
Bypass
TS4998 - QFN16
STBYR Control
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14
STBYL
P
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330nF
-O
LEFT
8
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Cin4
LIN+
)
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(
t
uc
330nF
2
bs
STBYL Control
P2
LIN-
5
Diff. input R-
330nF
1
6
Diff. input L-
The component calculations remain the same for the gain. In single-ended input
configuration, the formula is:
V O+ – V OR feed
50kΩAv SE = -------------------------- = ------------- = ------------Ve
R IN
R IN
with RIN expressed in kΩ.
27/33
Application information
4.13
TS4998
Notes on PSRR measurement
What is the PSRR?
The PSRR is the power supply rejection ratio. The PSRR of a device is the ratio between a
power supply disturbance and the result on the output. In other words, the PSRR is the
ability of a device to minimize the impact of power supply disturbance to the output.
How is the PSRR measured?
The PSRR is measured as shown in Figure 68.
Figure 68. PSRR measurement
)
s
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Vripple
du
13
Vcc
U1
Rin1
TS4998
Vcc
e
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ol
4.7uF
1
LI N-
2
LI N+
4
RIN-
Rin2
LEFT
bs
4.7uF
Rin3
)
s
(
t
4.7uF
3
s
b
O
LOUT-
12
+
LOUT+
11
-
ROUT-
9
+
ROUT+
10
RL
8Ohms
RL
8Ohms
GND
1uF
Cb
STBY
GND
STBYR
BIAS
7
Bypass
STBYL
o
r
P
14
TS4998 - QFN16
STBYR Control
e
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ol
-
Rin4
c
u
d
4.7uF
o
r
P
RIGHT
RIN+
STBYL Control
Cin4
-O
5
Cin3
6
Cin2
8
Cin1
Principles of operation
●
The DC voltage supply (VCC) is fixed
●
The AC sinusoidal ripple voltage (Vripple) is fixed
●
No bypass capacitor CS is used
The PSRR value for each frequency is calculated as:
RMS ( Output )
PSRR = 20 × Log --------------------------------- ( dB )
RMS ( Vripple )
RMS is an rms selective measurement.
28/33
TS4998
5
QFN16 package information
QFN16 package information
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.
Figure 69. QFN16 package
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Figure 70. QFN16 pinout (top view)
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29/33
QFN16 package information
TS4998
Figure 71. QFN16 4x4mm package mechanical data
Dimensions
Millimeters (mm)
Ref
Min
Typ
Max
0.8
0.9
1.0
A1
0.02
0.05
A3
0.20
A
*
* The Exposed Pad is connected to Ground.
)-
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(
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0.18
0.25
0.30
D
3.85
4.0
4.15
D2
2.1
E
3.85
E2
2.1
)
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u
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4.0
r
P
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let
so
b
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2.6
4.15
2.6
0.65
K
0.2
L
0.30
r
0.11
0.40
0.50
Figure 72. QFN16 footprint soldering pad
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30/33
Footprint data
Ref
mm
A
4.2
B
4.2
C
0.65
D
0.35
E
0.65
F
2.70
TS4998
6
Ordering information
Ordering information
Table 8.
Order codes
Order code
TS4998IQT
Temperature range
Package
Packaging
Marking
-40°C to +85°C
QFN16 4x4mm
Tape & reel
K998
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Revision history
7
TS4998
Revision history
Table 9.
Document revision history
Date
Revision
20-Dec-2007
1
Changes
Initial release.
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TS4998
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Please Read Carefully:
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Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the
right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any
time, without notice.
r
P
e
All ST products are sold pursuant to ST’s terms and conditions of sale.
Purchasers are solely responsible for the choice, selection and use of the ST products and services described herein, and ST assumes no
liability whatsoever relating to the choice, selection or use of the ST products and services described herein.
t
e
l
o
No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. If any part of this
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or services, or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoever of such
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)
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UNLESS OTHERWISE SET FORTH IN ST’S TERMS AND CONDITIONS OF SALE ST DISCLAIMS ANY EXPRESS OR IMPLIED
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Resale of ST products with provisions different from the statements and/or technical features set forth in this document shall immediately void
any warranty granted by ST for the ST product or service described herein and shall not create or extend in any manner whatsoever, any
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