ST TS472 User Manual

TS472

Very low noise microphone preamplifier with

2.0 V bias output and active low standby mode

Features

■ Low noise: 10 nV/√Hz typ. equivalent input

noise at F = 1 kHz

■ Fully-differential input/output

■ 2.2 to 5.5 V single supply operation

■ Low power consumption at 20 dB: 1.8 mA

■ Fast start up time at 0 dB: 5 ms typ.

■ Low distortion: 0.1% typ.

■ 40 kHz bandwidth regardless of the gain

■ Active low standby mode function (1 μA max)

■ Low noise 2.0 V microphone bias output

■ Available in flip-chip lead-free package and in

QFN24 4 x 4 mm package

■ ESD protection (2 kV)

Applications

■ Video and photo cameras with sound input

■ Sound acquisition and voice recognition

■ Video conference systems

■ Notebook computers and PDAs

Flip-chip - 12 bumps

Pin connections (top view)

QFN24

Description

Pin connections (top view)

The TS472 is a differential-input microphone

GND STBY VCC

preamplifier optimized for high-performance PDA
and notebook audio systems.

This device features an adjustable gain from 0 to
40 dB with excellent power-supply and common­mode 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.

August 2009 Doc ID 11015 Rev 6 1/25

BYP

GND

1

NC

2

3

NC

4

5

IN-

6

NC

8 9 10 11 12

7

IN+ GS BIAS

NC NC NC

NCNCNC

192021222324

18

NC

OUT+

17

OUT-

16

C2

15

14

C1

13

NC

www.st.com

25

Contents TS472

Contents

1 Typical application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

4.1 Differential configuration principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

4.2 Higher cut-off frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

4.3 Lower cut-off frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.4 Low-noise microphone bias source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.5 Gain settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4.6 Wake-up time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4.7 Standby mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

4.8 Layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

4.9 Single-ended input configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

4.10 Demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

5 Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5.1 Flip-chip package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5.2 QFN24 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6 Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2/25 Doc ID 11015 Rev 6

TS472 Typical application schematic

1 Typical application schematic

Figure 1 shows a typical application schematic for the TS472.

Figure 1. Application schematic (flip-chip)

Optional

VCC

C1

Cs
1uF

C3

Rpos

1uF

Cin+

+

Electret Mic

Table 1. Description of external components

Cin-

Rneg

U1 TS472_FC

Vcc

IN+

IN-

BIAS

2.0V

GND

C1

G

Bias

STDBY

C2

GAIN
SELECT

BYPASS

Standby Control

C2

OUT+

OUT-

Components Functional description

C

, C

in+

in-

Input coupling capacitors that block the DC voltage at the amplifier input
terminal.

Output coupling capacitors that block the DC voltage coming from the

, C

C

out+

out-

amplifier output terminal (pins C2 and D2) and determine the lower cut-off
frequency (see Section 4.3: Lower cut-off frequency).

Output load resistors used to charge the output coupling capacitors C

, R

R

out+

out-

These output resistors can be represented by an input impedance of a
following stage.

, R

R

pos

neg

C

s

C

b

, C

C

1

2

C

3

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.

Bias output filtering capacitor.

Cb
1uF

Cout+

Cout-

Rout+

Rout-

Positive Output

Negative Output

out

.

Doc ID 11015 Rev 6 3/25

Typical application schematic TS472

Table 2. Pin descriptions

Pin name

IN+ A1 8 Positive differential input

IN- B1 5 Negative differential input

BIAS A2 10 2 V bias output

GND C1 4, 22 Ground

STBY C3 21 Standby

BYP D1 2 Bypass

GS B2 9 Gain select

OUT- D2 16 Negative differential output

OUT+ C2 17 Positive differential output

C1 A3 14 Low-pass filter capacitor

C2 B3 15 Low-pass filter capacitor

Vcc D3 20 Power supply

NC ---

Flip-chip

designator

QFN

designator

3, 6, 7, 11,
12, 13, 18,

19, 23, 24

Not connected, floating pins

Pin description

4/25 Doc ID 11015 Rev 6

TS472 Absolute maximum ratings

2 Absolute maximum ratings

Table 3. Absolute maximum ratings

Symbol Parameter Value Unit

V

T

T

CC

V

oper

stg

T

Supply voltage

Input voltage -0.3 to VCC+0.3 V

i

Operating free air temperature range -40 to + 85 °C

Storage temperature -65 to +150 °C

Maximum junction temperature 150 °C

j

Thermal resistance junction to ambient:

R

thja

Flip-chip
QFN24

ESD Human body model 2 kV

ESD Machine model 200 V

Lead temperature (soldering, 10sec) 250 °C

1. All voltage values are measured with respect to the ground pin.

Table 4. Operating conditions

(1)

6V

180
110

°C/W

Symbol Parameter Value Unit

V

CC

A

Supply voltage 2.2 to 5.5 V

Typical differential gain
(GS connected to 4.7 kΩ or bias)

20 dB

Standby voltage input:

V

R

STBY

T

op

thja

Device ON
Device OFF

1.5 ≤ V

GND ≤ V

STBY

STBY

≤ V

CC

≤ 0.4

Operational free air temperature range -40 to +85 °C

Thermal resistance junction to ambient:

Flip-chip
QFN24

150

60

V

°C/W

Doc ID 11015 Rev 6 5/25

Electrical characteristics TS472

3 Electrical characteristics

Table 5. Electrical characteristics at VCC = 3 V with GND = 0 V, T

(unless otherwise specified)

Symbol Parameter Min. Typ. Max. Unit

amb

= 25° C

e

THD+N

V

Equivalent input noise voltage density

n

=100Ω at 1 kHz

R

EQ

Total harmonic distortion + noise
20 Hz ≤F ≤ 20 kHz, gain = 20 dB, V

Input voltage, gain = 20 dB 10 70 mV

in

=50mV

in

Bandwidth at -3 dB

B

Bandwidth at -1 dB

W

pin A3, B3 floating

Overall output voltage gain (Rgs variable):

G

Minimum gain, Rgs infinite
Maximum gain, Rgs = 0

Input impedance referred to GND 80 100 120 kΩ

in

Resistive load 10 kΩ

Capacitive load 100 pF

Supply current, gain = 20 dB 1.8 2.4 mA

Standby current 1 μA

R

LOAD

C

LOAD

I

I

STBY

Z

CC

Power supply rejection ratio, gain = 20 dB,

PSRR

F = 217 Hz, V

Differential output

= 200 mVpp, inputs grounded

ripple

Single-ended outputs,

Table 6. Bias output: VCC = 3 V, GND = 0 V, T

(unless otherwise specified)

RMS

amb

39.5

= 25° C

-3

nV

10

------------

0.1 %

40
20 kHz

-1.5

dB

41042.5

-70

dB

-46

Hz

RMS

Symbol Parameter Min. Typ. Max. Unit

V

R

I

out

PSRR

No load condition 1.9 2 2.1 V

out

Output resistance 80 100 120 W

out

Output bias current 2 mA

Power supply rejection ratio, F = 217 Hz,

= 200 mVpp

V

ripple

6/25 Doc ID 11015 Rev 6

70 80 dB

TS472 Electrical characteristics

Table 7. Differential RMS noise voltage

Gain

Input referred noise voltage

(μV

)

RMS

Output noise voltage

(μV

)

RMS

(dB)

Unweighted filter A-weighted filter Unweighted filter A-weighted filter

015 10 15 10

20 3.4 2.3 34 23

40 1.4 0.9 141 91

Table 8. Bias output RMS noise voltage

(1)

C

3

(μF)

Unweighted filter

RMS

)

(μV

154.4

10 2.2 1.2

1. Bias output filtering capacitor.

Table 9. SNR (signal to noise ratio), THD+N < 0.5%

Unweighted filter 20 Hz - 20 kHz

Gain

(dB)

(dB)

=2.2V VCC=3V VCC=5.5V VCC=2.2V VCC=3V VCC=5.5V

V

CC

0 75 76 76798080

A-weighted filter

(μV

RMS

A-weighted filter

(dB)

)

20 82 83 83 89 90 90

40 70 72 74 80 82 84

Doc ID 11015 Rev 6 7/25

Electrical characteristics TS472

Figure 2. Current consumption vs. power

supply voltage

3.0

2.5

2.0

1.5

1.0

0.5

Current Consumption (mA)

0.0
0123456

Tamb=85°C

Tamb=25°C

Tamb=-40°C

No Loads
GS floating

Power Supply Voltage (V)

Figure 4. Current consumption vs. standby

voltage

2.5

2.0

Figure 3. Current consumption vs. power

supply voltage

3.0

2.5

2.0

1.5

1.0

0.5

Current Consumption (mA)

0.0
0123456

Tamb=85°C

Tamb=25°C

Tamb=-40°C

No Loads
GS grounded

Power Supply Voltage (V)

Figure 5. Current consumption vs. standby

voltage

2.5

2.0

1.5

1.0

0.5

Current Consumption (mA)

0.0
012345

Vcc=3V

Standby Voltage (V)

Vcc=5V

No Loads
GS floating
Tamb = 25°C

Figure 6. Standby threshold voltage vs.

power supply voltage

1.0

0.8

0.6

0.4

0.2

Standby Treshold Voltage (V)

0.0

2.2

345

Power Supply V oltage (V)

No Loads
Tamb = 25°C

1.5

1.0

0.5

Current Consumption (mA)

0.0
012345

Standby Voltage (V)

Figure 7. Frequency response

30

5.5

Cb=1μF, T

20

10

PSRR (dB)

0

-10

-20
10 100 1000 10000 100000

=25°C, Gain=20dB, Rout=100k

AMB

Cin,Cout=100nF

Cin,Cout=10nF

Frequency (Hz)

Vcc=3V

no C1,C2

C1,C2=100pF

C1,C2=220pF

Vcc=5V

No Loads
GS grounded
Tamb = 25°C

Ω

8/25 Doc ID 11015 Rev 6