STMICROELECTRONICS TS472EIJT

TS472
Very low noise microphone preamplifier with
2.0V bias output and active low standby mode
Features
■
Low noise: 10nV/√Hz typ. equivalent input
noise @ F = 1kHz
■
Fully differential input/output
■
2.2V to 5.5V single supply operation
■
Low power consumption @20dB: 1.8mA
■
Fast start up time @ 0dB: 5ms typ.
■
Low distortion: 0.1% typ.
■
40kHz bandwidth regardless of the gain
■
Active low standby mode function (1μA max)
■
Low noise 2.0V microphone bias output
■
Available in flip-chip lead-free package and in
QFN24 4x4mm package
■
ESD protection (2kV)
Flip-chip - 12 bumps
Pin Connections (top view)
C1
C2
STDBY
VCC
OUTPUT
BIAS
GS
OUT+
OUT-
IN+
IN-
GND
BYPASS
QFN24
Description
The TS472 is a differential-input microphone
preamplifier optimized for high-performance, PDA
and notebook audio systems.
This device features an adjustable gain from 0dB
to 40dB with excellent power-supply and
common-mode rejection ratios. In addition, the
TS472 has a very low-noise microphone bias
generator of 2V.
Pin Connection (top view)
It also includes a complete shutdown function,
with active low standby mode.
Applications
■
Video and photo cameras with sound input
■
Sound acquisition & voice recognition
■
Video conference systems
■
Notebook computers and PDAs
September 2006
Rev 4
1/24
www.st.com
24
Contents
TS472
Contents
1
Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Typical application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5
Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6
7
2/24
5.1
Differential configuration principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.2
Higher cut-off frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.3
Lower cut-off frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.4
Low-noise microphone bias source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.5
Gain settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.6
Wake-up time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.7
Standby mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.8
Layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.9
Single-ended input configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.10
Demo board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.1
Flip-chip package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.2
QFN24 package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
TS472
1
Ordering information
Ordering information
Table 1.
Order codes
Temperature
range
Package
Packing
Marking
TS472EIJT
-40°C, +85°C
Flip-chip
Tape & reel
472
TS472IQT
-40°C, +85°C
QFN24 4x4mm
Tape & reel
K472
Part number
3/24
Typical application schematic
2
TS472
Typical application schematic
Figure 1 shows a typical application schematic for the TS472.
Figure 1.
Application schematic (flip-chip)
Table 2.
External component descriptions
Components
Cin+, Cin-
Input coupling capacitors that block the DC voltage at the amplifier input
terminal.
Cout+, Cout-
Output coupling capacitors that block the DC voltage coming from the
amplifier output terminal (pins C2 and D2) and determine Lower cut-off
frequency.
Rout+, Rout-
Output load resistors used to charge the output coupling capacitors Cout.
These output resistors can be represented by an input impedance of a
following stage.
Rpos, Rneg
Polarizing resistors for biasing of a microphone.
Cs
Supply bypass capacitor that provides power supply filtering.
Cb
Bypass pin capacitor that provides half-supply filtering.
C1, C2
4/24
Functional description
Low pass filter capacitors allowing to cut the high frequency.
TS472
3
Absolute maximum ratings
Absolute maximum ratings
Table 3.
Absolute maximum ratings
Symbol
VCC
Vi
Parameter
Supply voltage (1)
Input voltage
Value
Unit
6
V
-0.3 to VCC+0.3
V
Toper
Operating free air temperature range
-40 to + 85
°C
Tstg
Storage temperature
-65 to +150
°C
Maximum junction temperature
150
°C
Rthja
Thermal resistance junction to ambient:
Flip-chip
QFN24
180
110
°C/W
ESD
Human body model
2
kV
ESD
Machine model
200
V
Lead temperature (soldering, 10sec)
250
°C
Tj
1. All voltages values are measured with respect to the ground pin.
Table 4.
Operating conditions
Symbol
VCC
A
VSTBY
Parameter
Supply voltage
Typical differential gain (GS connected to 4.7kΩ or bias)
Standby voltage input:
Device ON
Device OFF
Value
Unit
2.2 to 5.5
V
20
dB
1.5 ≤VSTBY ≤VCC
GND ≤VSTBY ≤0.4
V
Top
Operational free air temperature range
-40 to +85
°C
Rthja
Thermal resistance junction to ambient:
Flip-chip
QFN24
150
60
°C/W
5/24
Electrical characteristics
4
Electrical characteristics
Table 5.
Electrical characteristics at VCC = 3V
with GND = 0V, Tamb = 25°C (unless otherwise specified)
Symbol
Parameter
Min.
Typ.
Max.
Unit
Equivalent input noise voltage density
REQ=100Ω at 1KHz
10
nV
-----------Hz
Total harmonic distortion + noise
20Hz ≤F ≤ 20kHz, Gain=20dB, Vin=50mVRMS
0.1
%
Vin
Input voltage, Gain=20dB
10
BW
Bandwidth @ -3dB
Bandwidth @ -1dB
pin A3, B3 floating
40
20
en
THD+N
G
Overall output voltage gain (Rgs variable):
Minimum gain, Rgs infinite
Maximum gain, Rgs=0
Zin
70
mVRMS
kHz
-3
39.5
-1.5
41
0
42.5
dB
Input impedance referred to GND
80
100
120
kΩ
RLOAD
Resistive load
10
CLOAD
Capacitive load
ICC
Supply current, Gain=20dB
ISTBY
Standby current
PSRR
Power supply rejection ratio, Gain=20dB, F=217Hz,
Vripple=200mVpp, inputs grounded
Differential output
Single-ended outputs,
Table 6.
kΩ
1.8
100
pF
2.4
mA
1
μA
dB
-70
-46
Bias output: VCC = 3V, GND = 0V, Tamb = 25°C (unless otherwise specified)
Symbol
Parameter
Min.
Typ.
Max.
Unit
Vout
No load condition
1.9
2
2.1
V
Rout
Output resistance
80
100
120
W
Iout
Output bias current
PSRR
6/24
TS472
Power supply rejection ratio, F=217Hz,
Vripple=200mVpp
70
2
mA
80
dB
TS472
Electrical characteristics
Table 7.
Differential RMS noise voltage
Input referred noise voltage
(μVRMS)
Gain
(dB)
Unweighted filter
A-weighted filter
Unweighted filter
A-weighted filter
0
15
10
15
10
20
3.4
2.3
34
23
40
1.4
0.9
141
91
Table 8.
Table 9.
Bias output RMS noise voltage
Cout
(μF)
Unweighted filter
(μVRMS)
A-weighted filter
(μVRMS)
1
5
4.4
10
2.2
1.2
SNR (signal to noise ratio), THD+N < 0.5%
Unweighted filter
(dB)
Gain
(dB)
Note:
Output noise voltage
(μVRMS)
A-weighted filter
(dB)
VCC=2.2V
VCC=3V
VCC=5.5V
VCC=2.2V
VCC=3V
VCC=5.5V
0
75
76
76
79
80
80
20
82
83
83
89
90
90
40
70
72
74
80
82
84
Unweighted filter = 20Hz ≤F ≤20kHz
7/24
Electrical characteristics
Table 10.
TS472
Index of graphics
Description
Current consumption vs. power supply voltage
Figure 2 and Figure 3
Current consumption vs. standby voltage
Figure 4 and Figure 5
Standby threshold voltage vs. power supply voltage
Figure 6
Frequency response
Figure 7
Bias output voltage vs. bias output current
Figure 8
Bias output voltage vs. power supply voltage
Figure 9
Bias PSRR vs. frequency
Differential output PSRR vs. frequency
8/24
Figure
Figure 10 and Figure 11
Figure 12 to Figure 15
Single-ended output PSRR vs. frequency
Figure 16
Equivalent input noise voltage density
Figure 17
Δgain vs. power supply voltage
Figure 18
Dgain vs. ambient temperature
Figure 19
Maximum input voltage vs. gain, THD+N<1%
Figure 20
Maximum input voltage vs. power supply voltage, THD+N<1%
Figure 21
THD+N vs. input voltage
Figure 22 to Figure 27
THD+N vs. frequency
Figure 28 to Figure 29
Transient response
Figure 30 to Figure 31
TS472
Electrical characteristics
2.5
2.5
Current Consumption (mA)
3.0
Tamb=85°C
2.0
1.5
Tamb=25°C
1.0
Tamb=-40°C
0.5
No Loads
GS floating
0
Figure 4.
Current Consumption (mA)
Figure 3.
3.0
0.0
1
2
3
4
Power Supply Voltage (V)
5
Current consumption vs. standby
voltage
Tamb=85°C
0.5
2.0
Vcc=5V
1.0
0.5
No Loads
GS floating
Tamb = 25°C
0
Figure 6.
1
2
3
Standby Voltage (V)
4
0
1
Current consumption vs. standby
voltage
Vcc=5V
0.5
30
0.8
20
PSRR (dB)
6
1.0
1.0
0.4
5
Vcc=3V
No Loads
GS grounded
Tamb = 25°C
0
1
Figure 7.
0.6
2
3
4
Power Supply Voltage (V)
1.5
0.0
5
Standby threshold voltage vs.
power supply voltage
No Loads
GS grounded
Figure 5.
2.0
Vcc=3V
Tamb=-40°C
1.0
2.5
1.5
Tamb=25°C
1.5
0.0
6
Current consumption vs. power
supply voltage
2.0
2.5
0.0
Standby Treshold Voltage (V)
Current consumption vs. power
supply voltage
Current Consumption (mA)
Current Consumption (mA)
Figure 2.
2
3
Standby Voltage (V)
4
5
Frequency response
Cb=1μ F, T AMB =25° C, Gain=20dB, Rout=100kΩ
10
no C1,C2
C1,C2=100pF
0
Cin,Cout=100nF
0.2
0.0
C1,C2=220pF
-10
Cin,Cout=10nF
No Loads
Tamb = 25°C
2.2
3
4
Power Supply Voltage (V)
5
5.5
-20
10
100
1000
Frequency (Hz)
10000
100000
9/24
Electrical characteristics
Figure 8.
TS472
Bias output voltage vs. bias output Figure 9.
current
2.2
2.2
Vcc=2.5-6V
Tamb=25°C
2.0
Bias Output Voltage (V)
Bias Output Voltage (V)
Bias output voltage vs. power
supply voltage
Tamb=85°C
1.8
Tamb=-40°C
1.6
Ibias=0mA
2.0
Ibias=2mA
1.8
Ibias=4mA
1.6
Tamb=25°C
1.4
1.4
0
1
2
3
Bias Output Current (mA)
4
Figure 10. Bias PSRR vs. frequency
4
Power Supply Voltage (V)
5
5.5
Figure 11. Bias PSRR vs. frequency
0
0
Vripple=200mVpp
Vcc=3V
Cb=1 μ F
Tamb =25 ° C
-40
Vripple=200mVpp
Vcc=5V
Cb=1 μ F
Tamb=25 ° C
-20
PSRR (dB)
-20
PSRR (dB)
3
2.2
Bias floating or 1k Ω to GND
-60
Bias = 1k Ω to GND
-40
-60
-80
-80
-100
-100
Bias floating
50
100
1000
50
10000 20k
100
1000
Frequency (Hz)
Frequency (Hz)
Figure 12. Differential output PSRR vs.
frequency
Figure 13. Differential output PSRR vs.
frequency
0
PSRR (dB)
-20
-30
0
Vripple=200mVpp
Inputs grounded
Vcc=3V
Cb=1 μ F
Cin=100nF
Tamb=25 ° C
-10
-20
GS grounded
-40
GS=bias
GS floating
-50
PSRR (dB)
-10
-30
-70
-70
10/24
100
1000
Frequency (Hz)
10000 20k
GS grounded
-50
-60
50
Vripple=200mVpp
Inputs grounded
Vcc=5V
Cb=1 μ F
Cin=100nF
Tamb=25 ° C
-40
-60
-80
10000 20k
-80
50
GS=bias
GS floating
100
1000
Frequency (Hz)
10000 20k
TS472
Electrical characteristics
Figure 14. Differential output PSRR vs.
frequency
Figure 15. Differential output PSRR vs.
frequency
0
0
V RIPPLE=200mV PP , Inputs grounded
-40
Cb=1μ F
No Cb
V CC =3V, Gain=20dB, Cin=1 μ F, T AMB =25° C
-20
PSRR (dB)
-20
PSRR (dB)
V RIPPLE =200mV PP, Inputs grounded
V CC =3V, Minimum Gain, Cin=1μ F, T AMB =25 ° C
Cb=100nF
-60
-40
Cb=1μ F
No Cb
-60
-80
-80
-100
50
-100
50
Cb=100nF
100
1k
Frequency (Hz)
10k
20k
Figure 16. Single-ended output PSRR vs.
frequency
1k
Frequency (Hz)
10k
20k
Figure 17. Equivalent input noise voltage
density
0
1000
-20
-30
Cin=100nF
R EQ=100 Ω
Vcc=3V
T AMB =25 ° C
en (nV/√ Hz)
Vripple=200mVpp
Inputs grounded
Cb=1μ F
Cin=100nF
Tamb=25° C
-10
PSRR (dB)
100
-40
-50
100
10
-60
-70
Vcc=2.2V
-80
100
50
Vcc=5V
1000
Frequency (Hz)
1
10
10000 20k
Figure 18. Δgain vs. power supply voltage
10k
100k
0.50
F=1kHz
Vin=5mV
Tamb=25°C
0.25
Maximum Gain
0.6
F=1kHz
V IN =5mV
0.00
Δ Gain (dB)
Δ Gain (dB)
1k
Frequency (Hz)
Figure 19. Δgain vs. ambient temperature
1.0
0.8
100
0.4
0.2
-0.25
Maximum Gain
-0.50
0.0
Gain=20dB
Minimum Gain
-0.2
-0.75
Gain=20dB
-0.4
2.2
3
4
Power Supply Voltage (V)
5
5.5
-1.00
-40
Minimum Gain
-20
0
20
40
Ambient Temperature (°C)
60
80
11/24
Electrical characteristics
TS472
Figure 20. Maximum input voltage vs. gain,
THD+N<1%
Figure 21. Maximum input voltage vs. power
supply voltage, THD+N<1%
F=1kHz
THD+N<1%
100
50
V CC =3V
V CC =2.2V
0
T AMB =25°C, F=1kHz, THD+N<1%
140
T AMB =25°C
V CC =5.5V
Maximum Input Voltage (mVRMS)
Maximum Input Voltage (mVRMS)
150
120
100
80
60
10
20
Gain (dB)
30
2.2
4
Power Supply Voltage (V)
GS=bias
THD+N (%)
1
0.1
GS=bias
0.1
GS grounded
GS grounded
Tamb=25°C, Vcc=3V, F=100Hz,
Cb=1 μ F, RL=10k Ω , BW=100Hz-120kHz
0.01
1E-3
0.01
0.01
0.1
0.3
Tamb=25°C, Vcc=5V, F=100Hz,
Cb=1 μ F, RL=10k Ω , BW=100Hz-120kHz
1E-3
0.01
Input Voltage (V)
0.1
0.3
Input Voltage (V)
Figure 24. THD+N vs. input voltage
Figure 25. THD+N vs. input voltage
10
10
GS floating
GS floating
GS=bias
GS=bias
1
THD+N (%)
1
THD+N (%)
5.5
GS floating
1
0.1
0.1
GS grounded
GS grounded
Tamb=25°C, Vcc=3V, F=1kHz,
Cb=1 μ F, RL=10k Ω , BW=100Hz-120kHz
1E-3
0.01
Input Voltage (V)
12/24
5
10
GS floating
THD+N (%)
3
Figure 23. THD+N vs. input voltage
10
0.01
Gain=20dB
20
40
Figure 22. THD+N vs. input voltage
Gain=30dB
Gain=40dB
40
0
0
Gain=0dB
0.01
0.1
0.3
1E-3
Tamb=25°C, Vcc=5V, F=1kHz,
Cb=1 μ F, RL=10k Ω , BW=100Hz-120kHz
0.01
Input Voltage (V)
0.1
0.3
TS472
Electrical characteristics
Figure 26. THD+N vs. input voltage
Figure 27. THD+N vs. input voltage
10
10
GS floating
GS floating
GS=bias
GS grounded
1
THD+N (%)
THD+N (%)
1
0.1
GS=bias
0.1
GS grounded
0.01
Tamb=25°C, Vcc=3V, F=20kHz,
Cb=1 μ F, RL=10k Ω , BW=100Hz-120kHz
1E-3
0.01
Tamb=25°C, Vcc=5V, F=20kHz,
Cb=1 μ F, RL=10k Ω , BW=100Hz-120kHz
0.01
0.1
0.3
1E-3
0.01
Input Voltage (V)
Figure 28. THD+N vs. frequency
10
Tamb=25°C
Vcc=3V
RL=10k Ω
Cb=1 μ F
BW=100Hz-120kHz
GS grounded, Vin=20mV
1
Tamb=25 ° C
Vcc=5V
RL=10k Ω
Cb=1 μ F
BW=100Hz-120kHz
GS=bias, Vin=100mV
THD + N (%)
THD + N (%)
0.3
Figure 29. THD+N vs. frequency
10
1
50
100
1000
Frequency (Hz)
Figure 30. Transient response
GS=bias, Vin=100mV
GS grounded, Vin=20mV
GS floating, Vin=100mV
GS floating, Vin=100mV
0.1
0.1
Input Voltage (V)
10000
20k
0.1
50
100
1000
Frequency (Hz)
10000
20k
Figure 31. Transient response
13/24
Application information
TS472
5
Application information
5.1
Differential configuration principle
The TS472 is a full-differential input/output microphone preamplifier. The TS472 also
includes a common mode feedback loop that controls the output bias value to average it at
VCC/2. This allows the device to always have a maximum output voltage swing, and by
consequence, maximize the input dynamic voltage range.
The advantages of a full-differential amplifier are:
5.2
●
Very high PSRR (power supply rejection ratio).
●
High common mode noise rejection.
●
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.
Higher cut-off frequency
The higher cut-off frequency FCH of the microphone preamplifier depends on the external
capacitors C1, C2.
TS472 has an internal first order low pass filter (R=40kΩ, C=100pF) to limit the highest cutoff frequency on 40kHz (with a 3dB attenuation). By connecting C1, C2 you can decrease
FCH by applying the following formula:
1
F CH = --------------------------------------------------------------------------------------------3
– 12
2π ⋅ 40 × 10 ⋅ ( C 1, 2 + 100 × 10 )
Figure 32 below indicates directly the higher cut-off frequency in Hz versus the value of the
output capacitors C1, C2 in nF.
Figure 32. Higher cut-off frequency vs. output
capacitors
Higher Cut-off Frequency (kHz)
40
10
1
200
400
600
C1, C2 (pF)
800
1000
For example, FCH is almost 20kHz with C1,2=100pF.
14/24
TS472
Application information
5.3
Lower cut-off frequency
The lower cut-off frequency FCL of the microphone preamplifier depends on the input
capacitors Cin and output capacitors Cout. These input and output capacitors are mandatory
in an application because of DC voltage blocking.
The input capacitors Cin in series with the input impedance of the TS472 (100kΩ) are
equivalent to a first order high pass filter. Assuming that FCL is the lowest frequency to be
amplified (with a 3dB attenuation), the minimum value of Cin is:
1
C in = -----------------------------------------------------3
2π ⋅ F CL ⋅ 100 × 10
The capacitors Cout in series with the output resistors Rout (or an input impedance of the
next stage) are also equivalent to a first order high pass filter. Assuming that FCL is the
lowest frequency to be amplified (with a 3dB attenuation), the minimum value of Cout is:
1
C out = -----------------------------------------2π ⋅ F CL ⋅ R out
Figure 33. Lower cut-off frequency vs. input
capacitors
Figure 34. Lower cut-off frequency vs. output
capacitors
1000
1000
Rout=10kΩ
Typical Zin
100
ZinMIN
10
1
10
Cin (nF)
100
Lower Cut-off frequency (Hz)
Lower Cut-off frequency (Hz)
ZinMAX
100
Rout=100kΩ
10
1
10
100
1000
Cout (nF)
Figure 33 and Figure 34 give directly the lower cut-off frequency (with 3dB attenuation)
versus the value of the input or output capacitors
Note:
In case FCL is kept the same for calculation, take into account that the 1st order high-pass
filter on the input and the 1st order high-pass filter on the output create a 2nd order highpass filter in the audio signal path with an attenuation of 6dB on FCL and a rolloff of
40dB⁄ decade.
5.4
Low-noise microphone bias source
The TS472 provides a very low noise voltage and power supply rejection BIAS source
designed for biasing an electret condenser microphone cartridge. The BIAS output is
typically set at 2.0 VDC (no load conditions), and can typically source 2mA with respect to
drop-out, determined by the internal resistance 100Ω (for detailed load regulation curves
see Figure 8).
15/24
Application information
5.5
TS472
Gain settings
The gain in the application depends mainly on:
●
the sensitivity of the microphone
●
the distance to the microphone
●
the audio level of the sound
●
the desired output level
The sensitivity of the microphone is generally expressed in dB/Pa, referenced to 1V/Pa. For
example, the microphone used in testing had an output voltage of 6.3mV for a sound
pressure of 1 Pa (where Pa is the pressure unit, Pascal). Expressed in dB, the sensitivity is:
20Log(0.0063) = -44 dB/Pa
To facilitate the first approach, Table 11 below gives voltages and gains used with a low cost
omnidirectional electret condenser microphone of -44dB/Pa.
Table 11.
Typical TS472 gain vs. distance to the microphone (sensitivity -44dB/Pa)
Distance to microphone
Microphone output voltage
TS472 Gain
1cm
30mVRMS
20
20cm
3mVRMS
100
The gain of the TS472 microphone preamplifier can be set:
1.
From -1.5 dB to 41 dB by connecting an external grounded resistor RGS to the GS pin.
It allows to adapt more precisely the gain to each application.
Table 12.
Selected gain vs. gain select resistor
Gain (dB)
0
10
20
30
40
RGS (Ω)
470k
27k
4k7
1k
68
Figure 35. Gain in dB vs. gain select resistor
Figure 36. Gain in V/V vs. gain select resistor
50
Tamb=25 ° C
Tamb=25 ° C
100
40
Gain (V/V)
Gain (dB)
30
20
10
10
0
1
-10
10
100
2.
16/24
1k
10k
R GS (Ω )
100k
1M
10
100
1k
10k
R GS (Ω )
100k
1M
To 20dB by applying VGS > 1VDC on Gain Select (GS) pin. This setting can help to
reduce a number of external components in an application, because 2.0 VDC is
provided by TS472 itself on BIAS pin.
TS472
Application information
Figure 37 below gives other values of the gain vs. voltage applied on GS pin.
Figure 37. Gain vs. gain select voltage
Tamb=25° C
40
Gain (dB)
20
0
-20
-40
-60
-80
0.2
0.4
0.6
0.8
V GS (V )
4
5
Wake-up time
When the standby is released to put the device ON, a signal appears on the output a few
microseconds later, and the bypass capacitor Cb is charged in a few milliseconds. As Cb is
directly linked to the bias of the amplifier, the bias will not work properly until the Cb voltage
is correct.
In the typical application, when a biased microphone is connected to the differential input via
the input capacitors (Cin), (and the output signal is in line with the specification), the wake-up
time will depend upon the values of the input capacitors Cin and the gain. When gain is
lower than 0dB, the wake-up time is determined only by the bypass capacitor Cb, as
described above. For a gain superior to 0dB, see Figure 38 below.
Figure 38. Wake-up time in the typical application vs. input capacitors
60
50
Wake-up Time (ms)
5.6
0
Tamb = 25°C
Vcc=3V
Cb=1μ F
40
Maximum Gain
Gain=20dB
30
20
10
0
20
40
60
Input capacitors C IN (nF)
80
100
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Application information
5.7
TS472
Standby mode
When the standby command is set, the time required to set the output stages (differential
outputs and 2.0V bias output) in high impedance and the internal circuitry in shutdown mode
is a few microseconds.
5.8
Layout considerations
The TS472 has sensitive pins to connect C1, C2 and Rgs. To obtain high power supply
rejection and low noise performance, it is mandatory that the layout track to these
component is as short as possible.
Decoupling capacitors on VCC and bypass pin are needed to eliminate power supply drops.
In addition, the capacitor location for the dedicated pin should be as close to the device as
possible.
5.9
Single-ended input configuration
It’s possible to use the TS472 in a single-ended input configuration. The schematic in
Figure 39 provides an example of this configuration.
Figure 39. Single ended input typical application
Optional
C1
VCC
Cs
1uF
Cin+
A3
B3
TS472
Cout+
A1
IN+
OUT+
C2
B1
IN-
OUT-
D2
+
Electret Mic
Vcc
C2
U1
C1
Rpos
D3
C3
1uF
C2
Cout-
G
BIAS
2.0V
GND
STDBY
C3
Bias
C1
A2
B2
BYPASS
D1
Cb
1uF
Standby Control
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Positive Output
Negative Output
Cin-
GAIN
SELECT
Rout+
Rout-
TS472
5.10
Application information
Demo board
A demo board for the TS472 is available. For more information about this demo board,
please refer to Application Note AN2240, which can be found on www.st.com.
Figure 40. PCB top layer
Figure 41. PCB bottom layer
Figure 42. Component location
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Package mechanical data
6
TS472
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.
6.1
Flip-chip package
Figure 43. TS472 footprint recommendation
75µm min.
100μm max.
500μm
500μm
Track
Φ=400μm typ.
150μm min.
Φ=340μm min.
500μm
500μm
Φ=250μm
Non Solder mask opening
Pad in Cu 18μm with Flash NiAu (2-6μm, 0.2μm max.)
Figure 44. Pin-out (top view)
3
C1
2
OUTPUT
BIAS
1
C2
STDBY
VCC
GS
OUT+
OUT-
IN+
IN-
GND
BYPASS
A
B
C
D
Balls are underneath
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TS472
Package mechanical data
Figure 45. Marking (top view)
■
ST logo
■
Part number: 472
■
E Lead free bumps
■
Three digits datecode: YWW
■
The dot indicates pin A1
E
472
YWW
Figure 46. Flip-chip - 12 bumps
2.1 mm
1.6 mm
■
Die size: 2.1mm x 1.6mm ± 30µm
■
Die height (including bumps): 600µm
■
Bumps diameter: 315µm ±50µm
■
Bump diameter before reflow: 300µm ±10µm
■
Bump height: 250µm ±40µm
■
Die height: 350µm ±20µm
■
Pitch: 500µm ±50µm
■
Coplanarity: 50µm max
0.5mm
0.5mm
∅ 0.315mm
600µm
Figure 47. Tape & reel specification (top view)
1.5
4
1
1
A
Die size Y + 70µm
A
8
Die size X + 70µm
4
All dimensions are in mm
User direction of feed
21/24
Package mechanical data
6.2
QFN24 package
Figure 48. QFN24 package mechanical data
22/24
TS472
TS472
7
Revision history
Revision history
Table 13.
Document revision history
Date
Revision
Changes
1-Jul-05
1
Initial release corresponding to product preview version.
1-Oct-05
2
First release of fully mature product datasheet.
1-Dec-05
3
Added single-ended input operation in Section 5: Application
information.
12-Sep-2006
4
Added QFN package information. Updated curves, added new ones
in Section 4: Electrical characteristics.
23/24
TS472
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