TS472
Very low noise microphone preamplifier with 2.0V bias output and active low standby mode
Features
Flip-chip - 12 bumps
Low noise: 10nV/ z typ. equivalent input H 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 (1A max) Low noise 2.0V microphone bias output Available in flip-chip lead-free package and in QFN24 4x4mm package ESD protection (2kV) QFN24
C1 C2 STDBY VCC
Pin Connections (top view)
OUTPUT BIAS
GS
OUT+
OUT-
IN+
IN-
GND
BYPASS
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. It also includes a complete shutdown function, with active low standby mode.
Pin Connection (top view)
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 2 3 4 5 Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Typical application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 Differential configuration principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Higher cut-off frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Lower cut-off frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Low-noise microphone bias source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Gain settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Wake-up time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Standby mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Single-ended input configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Demo board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.1 6.2 Flip-chip package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 QFN24 package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
7
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
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TS472
Ordering information
1
Ordering information
Table 1. Order codes
Temperature range -40C, +85C -40C, +85C Package Flip-chip QFN24 4x4mm Packing Tape & reel Tape & reel Marking 472 K472
Part number TS472EIJT TS472IQT
3/24
Typical application schematic
TS472
2
Typical application schematic
Figure 1 shows a typical application schematic for the TS472. Figure 1. Application schematic (flip-chip)
Table 2.
External component descriptions
Functional description Input coupling capacitors that block the DC voltage at the amplifier input terminal. Output coupling capacitors that block the DC voltage coming from the amplifier output terminal (pins C2 and D2) and determine Lower cut-off frequency. 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. Polarizing resistors for biasing of a microphone. Supply bypass capacitor that provides power supply filtering. Bypass pin capacitor that provides half-supply filtering. Low pass filter capacitors allowing to cut the high frequency.
Components Cin+, Cin-
Cout+, Cout-
Rout+, RoutRpos, Rneg Cs Cb C1, C2
4/24
TS472
Absolute maximum ratings
3
Absolute maximum ratings
Table 3.
Symbol VCC Vi Toper Tstg Tj Rthja ESD ESD Supply voltage (1) Input voltage Operating free air temperature range Storage temperature Maximum junction temperature Thermal resistance junction to ambient: Flip-chip QFN24 Human body model Machine model Lead temperature (soldering, 10sec)
1. All voltages values are measured with respect to the ground pin.
Absolute maximum ratings
Parameter Value 6 -0.3 to VCC+0.3 -40 to + 85 -65 to +150 150 180 110 2 200 250 Unit V V C C C C/W kV V C
Table 4.
Symbol VCC A VSTBY Top Rthja
Operating conditions
Parameter Supply voltage Typical differential gain (GS connected to 4.7k or bias) Standby voltage input: Device ON Device OFF Operational free air temperature range Thermal resistance junction to ambient: Flip-chip QFN24 Value 2.2 to 5.5 20 1.5 VSTBY VCC GND VSTBY 0.4 -40 to +85 150 60 Unit V dB V C C/W
5/24
Electrical characteristics
TS472
4
Electrical characteristics
Table 5.
Symbol en THD+N Vin BW
Electrical characteristics at VCC = 3V with GND = 0V, Tamb = 25C (unless otherwise specified)
Parameter Equivalent input noise voltage density REQ=100 at 1KHz Total harmonic distortion + noise 20Hz F 20kHz, Gain=20dB, Vin=50mVRMS Input voltage, Gain=20dB Bandwidth @ -3dB Bandwidth @ -1dB pin A3, B3 floating Overall output voltage gain (Rgs variable): Minimum gain, Rgs infinite Maximum gain, Rgs=0 Input impedance referred to GND Resistive load Capacitive load Supply current, Gain=20dB Standby current Power supply rejection ratio, Gain=20dB, F=217Hz, Vripple=200mVpp, inputs grounded Differential output Single-ended outputs, 1.8 -3 39.5 80 10 100 2.4 1 Min. Typ. 10 0.1 10 40 20 70 Max. Unit
nV ----------Hz
% mVRMS kHz
G Zin RLOAD CLOAD ICC ISTBY
-1.5 41 100
0 42.5 120
dB k k pF mA A
PSRR
-70 -46
dB
Table 6.
Symbol Vout Rout Iout PSRR
Bias output: VCC = 3V, GND = 0V, Tamb = 25C (unless otherwise specified)
Parameter No load condition Output resistance Output bias current Power supply rejection ratio, F=217Hz, Vripple=200mVpp 70 Min. 1.9 80 Typ. 2 100 2 80 Max. 2.1 120 Unit V W mA dB
6/24
TS472 Table 7.
Gain (dB) 0 20 40
Electrical characteristics Differential RMS noise voltage
Input referred noise voltage (VRMS) Unweighted filter 15 3.4 1.4 A-weighted filter 10 2.3 0.9 Output noise voltage (VRMS) Unweighted filter 15 34 141 A-weighted filter 10 23 91
Table 8.
Bias output RMS noise voltage
Cout (F) 1 10 Unweighted filter (VRMS) 5 2.2 A-weighted filter (VRMS) 4.4 1.2
Table 9.
Gain (dB)
SNR (signal to noise ratio), THD+N < 0.5%
Unweighted filter (dB) VCC=2.2V VCC=3V 76 83 72 VCC=5.5V 76 83 74 VCC=2.2V 79 89 80 A-weighted filter (dB) VCC=3V 80 90 82 VCC=5.5V 80 90 84
0 20 40
75 82 70
Note:
Unweighted filter = 20Hz F 20kHz
7/24
Electrical characteristics Table 10. Index of graphics
Description Current consumption vs. power supply voltage Current consumption vs. standby voltage Standby threshold voltage vs. power supply voltage Frequency response Bias output voltage vs. bias output current Bias output voltage vs. power supply voltage Bias PSRR vs. frequency Differential output PSRR vs. frequency Single-ended output PSRR vs. frequency Equivalent input noise voltage density Figure
TS472
Figure 2 and Figure 3 Figure 4 and Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 and Figure 11 Figure 12 to Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Figure 22 to Figure 27 Figure 28 to Figure 29 Figure 30 to Figure 31
gain vs. power supply voltage
Dgain vs. ambient temperature Maximum input voltage vs. gain, THD+N<1% Maximum input voltage vs. power supply voltage, THD+N<1% THD+N vs. input voltage THD+N vs. frequency Transient response
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TS472
Electrical characteristics
Figure 2.
Current consumption vs. power supply voltage
Figure 3.
Current consumption vs. power supply voltage
3 .0 2 .5 2 .0 1 .5 1 .0 0 .5 0 .0
N o Loads G S floating Tam b=8 5C
3 .0 2 .5
T a m b = 8 5 C
Current Consumption (mA)
Current Consumption (mA)
2 .0 1 .5 1 .0 0 .5 0 .0
N o Loads G S grounded Ta m b=2 5C
Ta m b=2 5C
T a m b = -4 0 C
T a m b = -4 0 C
0
1
2 3 4 Pow er Supply Voltage (V)
5
6
0
1
2 3 4 Pow er Supply Voltage (V)
5
6
Figure 4.
Current consumption vs. standby voltage
Figure 5.
Current consumption vs. standby voltage
2 .5
2 .5
1 .5 Vcc=3V 1 .0 Vcc=5V
Current Consumption (mA)
Current Consumption (mA)
2 .0
2 .0
1 .5
Vcc= 3V
Vcc=5V
1 .0
0 .5
0 .0
N o Loads G S floating T a m b = 25C
0 .5
0
1
2 3 Standby Voltage (V)
4
5
0 .0
N o Loads G S grounded T a m b = 25C
0
1
2 3 Standby Voltage (V)
4
5
Figure 6.
Standby threshold voltage vs. power supply voltage
Figure 7.
Frequency response
1.0
Standby Treshold Voltage (V)
30
C b= 1 F , T A M B = 25 C , Gain=20dB, Rout=100k
0.8
PSRR (dB)
20
0.6
10
no C1,C2 C 1 ,C 2 = 1 0 0 p F C in , C o u t = 1 0 0 n F
0.4
0
0.2 N o Loads T am b = 25C 2.2 3 4 P o w e r Supply Voltage (V) 5 5.5
-10
C 1 ,C 2 = 2 2 0 p F C in ,C o u t = 1 0 n F
0.0
-20 10
100
1000 F re q u en cy (Hz)
10000
1000 00
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Electrical characteristics
TS472
Figure 8.
Bias output voltage vs. bias output Figure 9. current
2 .2
Bias output voltage vs. power supply voltage
2 .2
V c c = 2 .5 - 6 V
Bias Output Voltage (V)
T a m b= 2 5 C
Ibia s= 0m A
Bias Output Voltage (V)
2 .0
Tam b=8 5C
2 .0 Ibia s= 2m A 1 .8 Ibia s= 4m A 1 .6
1 .8
1 .6
Tamb=-40C Ta m b = 2 5 C
1 .4
0
1 2 3 Bias Output Current (mA)
4
1 .4 2.2
3
4 P o w e r Supply Voltage (V)
5
5 .5
Figure 10. Bias PSRR vs. frequency
0 V r ip p l e = 2 0 0 m V p p V cc =3 V Cb=1 F T a m b =25C
Figure 11. Bias PSRR vs. frequency
0 V r ip p l e = 2 0 0 m V p p V cc =5 V Cb=1 F Tam b=25C B ia s = 1k to GND
-2 0
P S R R (dB)
-2 0
P S R R (dB)
-4 0
B ia s floating or 1k to GND
-4 0
-6 0
-6 0
-8 0
-8 0 B ia s floating
-1 0 0
-1 0 0
50
100
1000
F r e q u e n c y (Hz)
100 00 20k
50
100
1000
F r e q u e n c y (Hz)
100 00 20k
Figure 12. Differential output PSRR vs. frequency
0 -1 0 -2 0
P S R R (dB)
Figure 13. Differential output PSRR vs. frequency
0 V r ip p l e = 2 0 0 m V p p In p u ts grounded V c c=5 V Cb=1 F C in = 1 0 0 n F Tam b=25C G S grounded G S = b ia s G S floating
-3 0 -4 0
P S R R (dB)
V r i p p le = 2 0 0 m V p p In p u ts grounded V cc =3 V Cb=1 F C in = 1 0 0 n F Tam b=25C G S grounded G S = b ia s G S floating
-1 0 -2 0 -3 0 -4 0 -5 0 -6 0 -7 0
-5 0 -6 0 -7 0 -8 0
50
100
1000 F r e q u e n c y (Hz)
10 000 20k
-8 0
50
100
1000 F r e q u e n c y (Hz)
1 0 0 0 0 2 0k
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TS472
Electrical characteristics
Figure 14. Differential output PSRR vs. frequency
0 V R IP P LE= 2 00m V P P , Inputs grounded -20 V C C = 3V , Minimum Gain, Cin=1F, T AM B =25C
Figure 15. Differential output PSRR vs. frequency
0 V RIP P LE = 200m V P P, Inputs grounded -20 V CC = 3V , Gain=20dB, Cin=1F, T A M B =25C
PSRR (dB)
-40 N o Cb -60 C b =100nF
PSRR (dB)
C b=1 F
-40 C b=1 F N o Cb -60
-80
-80 C b=100nF
-100 50
100
1k F r eq u e n c y (Hz)
10k
20k
-100 50
100
1k F r eq u e n c y (Hz)
10k
20k
Figure 16. Single-ended output PSRR vs. frequency
0 -10 -20
PSRR (dB)
Figure 17. Equivalent input noise voltage density
1 00 0
-30 -40 -50 -60 -70 -80
50
en (nV/Hz)
V r i p p le = 2 0 0 m V p p Inputs grounded C b=1 F C in = 1 0 0 n F Ta m b= 25 C
C in = 1 0 0 n F R EQ= 1 00
V c c= 3 V
10 0
T A M B = 25 C
10
V c c= 2.2V 100 1000 F re q u e n c y (Hz)
V cc = 5 V 1000 0 2 0k
1 10 1 00 1k F re q u e n c y (Hz) 10 k 1 0 0k
Figure 18. gain vs. power supply voltage
1 .0 0 .8 0 .6 0 .4 0 .2 0 .0 - 0 .2 - 0 .4 2.2 F = 1 kH z V in = 5 m V Tam b=25C
Figure 19. gain vs. ambient temperature
0 .5 0 0 .2 5 0 .0 0
Gain (dB)
M axim um Gain
F = 1 kH z V IN = 5 m V
Gain (dB)
- 0 .2 5 M axim um Gain - 0 .5 0 G a in = 2 0 d B M inim um Gain -2 0 0 20 40 A m b ie n t Temperature (C) 60 80
M inim um Gain G a in = 2 0 d B 3 4 P o w e r Supply Voltage (V) 5 5 .5
- 0 .7 5 - 1 .0 0 -40
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Electrical characteristics
TS472
Figure 20. Maximum input voltage vs. gain, THD+N<1%
150
Maximum Input Voltage (mVRMS)
Figure 21. Maximum input voltage vs. power supply voltage, THD+N<1%
14 0
Maximum Input Voltage (mVRMS)
V CC = 5 .5V
T AM B = 2 5 C F = 1 kH z THD+N <1%
T A M B = 2 5 C , F=1kHz, THD+N<1%
G a in = 0 d B
12 0 10 0 80 60 40 20 0 3 4 P o w e r Supply Voltage (V) 5 5 .5 G a in = 4 0 d B G a in = 3 0 d B G a in = 2 0 d B
100
50 VCC=3V V C C = 2 .2 V 0 0 10 20 G a in (dB) 30 40
2 .2
Figure 22. THD+N vs. input voltage
10 G S floating G S = b ia s 1
T H D + N (%)
Figure 23. THD+N vs. input voltage
10 G S floating G S = b ia s
1
T H D + N (%)
0 .1 G S grounded 0 .0 1 1 E -3 T a m b = 2 5 C , Vcc=3V, F=100Hz, C b = 1 F , RL=10k , BW=100Hz-120kHz 0 .0 1
In p u t Voltage (V)
0 .1 G S grounded 0 .0 1 Ta m b = 2 5 C , Vcc=5V, F=100Hz, C b = 1 F , RL=10k , BW=100Hz-120kHz 0 .0 1
In p u t Voltage (V)
0 .1
0 .3
1 E -3
0 .1
0 .3
Figure 24. THD+N vs. input voltage
10 G S floating G S = b ia s 1
T H D + N (%)
Figure 25. THD+N vs. input voltage
10 G S floating G S = b ia s 1
T H D + N (%)
0 .1 G S grounded 0 .0 1 T a m b = 2 5 C , Vcc=3V, F=1kHz, Cb=1F, RL=10k , BW=100Hz-120kHz 0 .0 1
In p u t Voltage (V)
0 .1 G S grounded 0 .0 1 T a m b = 2 5 C , Vcc=5V, F=1kHz, C b = 1 F, RL=10k , BW=100Hz-120kHz 0 .0 1
In p u t Voltage (V)
1 E -3
0 .1
0 .3
1 E -3
0 .1
0 .3
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TS472
Electrical characteristics
Figure 26. THD+N vs. input voltage
10 G S floating G S = b ia s 1
T H D + N (%)
Figure 27. THD+N vs. input voltage
10 G S floating G S grounded 1
T H D + N (%)
G S = b ia s
0 .1 G S grounded 0 .0 1 T a m b = 2 5 C , Vcc=3V, F=20kHz, C b = 1 F , RL=10k , BW=100Hz-120kHz 0 .0 1
In p u t Voltage (V)
0 .1
0 .0 1 0 .1
0 .3
T a m b = 2 5 C , Vcc=5V, F=20kHz, C b = 1 F, RL=10k , BW=100Hz-120kHz 0 .0 1
In p u t Voltage (V)
1 E -3
1 E -3
0 .1
0 .3
Figure 28. THD+N vs. frequency
10
Tam b=2 5C V cc =3 V R L =10 k Cb=1 F B W = 1 0 0 H z-1 2 0 kH z G S = b ia s , Vin=100mV
Figure 29. THD+N vs. frequency
10 Tam b=25C Vcc=5V RL=10k Cb=1 F B W = 1 0 0 H z -1 2 0 k H z 1
T H D + N (%)
1
G S grounded, Vin=20mV
T H D + N (%)
G S = b ia s , Vin=100mV
G S grounded, Vin=20mV
G S floating, Vin=100mV
G S floating, Vin=100mV 10000 20k 0 .1 50 100 1000 F r e q u e n c y (Hz) 10000 20k
0.1
50
100
1000 F r e q u e n c y (Hz)
Figure 30. Transient response
Figure 31. Transient response
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Application information
TS472
5
5.1
Application information
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:
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.
5.2
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=40k C=100pF) to limit the highest cut, off frequency on 40kHz (with a 3dB attenuation). By connecting C1, C2 you can decrease FCH by applying the following formula:
1 F C H = --------------------------------------------------------------------------------------------3 12 2 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
40
H igher Cut-off Frequency (kHz)
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 (100k) 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 i n = -----------------------------------------------------3 2 F C L 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 o u t = -----------------------------------------2 FC L Ro u t
Figure 33. Lower cut-off frequency vs. input capacitors
10 0 0 Z in M A X Typical Zin
Figure 34. Lower cut-off frequency vs. output capacitors
10 0 0 R o u t= 1 0 k
Lower Cut-off frequency (Hz)
Lower Cut-off frequency (Hz)
100
100
Z i n M IN
R o u t= 1 0 0 k
10
1
10 C in (nF)
100
10
1
10
C o u t (nF)
10 0
1000
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 100 (for detailed load regulation curves see Figure 8).
15/24
Application information
TS472
5.5
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)
Microphone output voltage 30mVRMS 3mVRMS TS472 Gain 20 100
Distance to microphone 1cm 20cm
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. Selected gain vs. gain select resistor
0 470k 10 27k 20 4k7 30 1k 40 68
Table 12.
Gain (dB) RGS ()
Figure 35. Gain in dB vs. gain select resistor
50 Tamb=25C 40 30
G ain (dB)
Figure 36. Gain in V/V vs. gain select resistor
Tamb=25C 100
G a in (V/V)
20 10 0 -1 0 10
10
1 10 100 1k 10k R G S () 100k 1M
100
1k
10k R G S ()
100k
1M
2.
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.
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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
40 20 0 -20 -40 -60 -80 Tam b=25 C
Gain (dB)
0
0.2
0 .4
0 .6 0.8 V GS (V)
4
5
5.6
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)
T a m b = 25C V cc= 3V C b= 1 F
M axim um Gain
40 30 20 10 0
G ain= 20 dB
20
40 60 In p u t capacitors C IN (nF)
80
100
17/24
Application information
TS472
5.7
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
O ptional C1
VCC
Cs 1uF
C2
D3
A3
C3 1uF
Rpos
U1
B3
TS 4 7 2 Rout+
C1
C2
Vc c
Cin+
Cout+
A1 B1
IN + IN -
OU T+ OU TGA I N S E LE C T
C2 D2
CoutRout-
+
Electret Mic Cin-
Positive Output Negative Output
G
A2
B2
B IA S 2. 0 V GND
B ia s S T D BY
BYPASS
D1
Cb 1uF
C1
C3
Standby Control
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TS472
Application information
5.10
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
TS472
6
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
500m =250m 500m 75m min. 100m max. Track
500m
=400m typ. =340m min.
150m min.
Non Solder mask opening
500m
Pad Pad in Cu 18m with Flash NiAu (2-6m, 0.2m max.)
Figure 44. Pin-out (top view)
3 2 1
C1
C2
STDBY
VCC
OUTPUT BIAS
GS
OUT+
OUT-
IN+
IN-
GND
BYPASS
A
B
C
D
Balls are underneath
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TS472 Figure 45. Marking (top view)
Package mechanical data
ST logo Part number: 472 E Lead free bumps Three digits datecode: YWW The dot indicates pin A1
472 472 YW W
E
Figure 46. Flip-chip - 12 bumps
2 .1 mm
1 .6 mm
Die size: 2.1mm x 1.6mm 30m Die height (including bumps): 600m Bumps diameter: 315m 50m Bump diameter before reflow: 300m 10m Bump height: 250m 40m Die height: 350m 20m Pitch: 500m 50m Coplanarity: 50m max
0 .5 m m
0 .5 m m
0 .3 1 5 m m
600m
Figure 47. Tape & reel specification (top view)
4
1.5
1 A A
Die size Y + 70m
1
8
Die size X + 70m
4
All dimensions are in mm
User direction of feed
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Package mechanical data
TS472
6.2
QFN24 package
Figure 48. QFN24 package mechanical data
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TS472
Revision history
7
Revision history
Table 13.
Date 1-Jul-05 1-Oct-05 1-Dec-05 12-Sep-2006
Document revision history
Revision 1 2 3 4 Changes Initial release corresponding to product preview version. First release of fully mature product datasheet. Added single-ended input operation in Section 5: Application information. Added QFN package information. Updated curves, added new ones in Section 4: Electrical characteristics.
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TS472
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