SGS Thomson Microelectronics TDA7512 Datasheet

AM/FM CAR RADIO TUNER IC WITH INTELLIGENT

FM-PART

■ RF AGC GENERATION BY RF AND IF

DETECTION

■ I/Q MIXER FOR 1S T FM IF 10.7MHz WIT H

IMAGE REJECTION

■ 2 PROGRAMMABLE IF-GAIN STAGES

■ MIXER FOR 2

■ INTERNAL 450KHz BANDPASS FILTER WITH

THREE BANDWIDTHS CONTROLLED BY ISS

■ FULLY INTEGR ATED FM-DEMODULATOR

WITH NOISE CANCELLATION

AM-PART

■ WIDE AND NARROW AGC GENERATION

■ PREAMPLIFIER AND MIXER FOR 1ST IF

10.7MHz, AM UPCONVERSION

■ MIXER FOR 2

■ INTEGRATED AM-DEMODULATOR

■ OUTPUT FOR AM-STEREO-DECODER

ADDITIONAL FEATURES

■ VCO FOR WORLD TUNING RANGE

■ HIGH PERFORMANCE FAST PLL FOR RDS-

SYSTEM

■ IF COUNTER FOR FM AND AM WITH

SEARCH STOP SIGNAL

■ QUALITY DETECTOR FOR LEVEL,

DEVIATION, ADJACENT CHANNEL AND
MULTIPATH

■ QUALITY DETECTION INFORMATIONS AS

ANALOG SIGNALS EXT ERN AL AVAIL ABLE

nd

IF 450KHz

nd

IF 450KHz

TDA7512

SELECTIVITY SYSTEM (ISS)

PRELIMINARY DATA

TQFP64

ORDERING NUMBER: TDA7512

■

ISS (INTELLIG ENT SELECTIVITY SYSTEM)
FOR CANCELLATION OF ADJACENT
CHANNEL AND NOISE INFLUENCES

■ ADJACENT CHANNEL MUTE

■ FULLY ELECTR ONIC ALIGNMENT

■ ALL FUNCTIONS I

■ ISS FILTE R STATUS I NFORMATION I

READABLE

DESCRIPTION

The TDA7512 is a high performance tuner circuit for
AM/FM car radio. It contains mixer, IF amplifier, de­modulator for AM and FM, q uality detection, ISS filter
and PLL synthesizer with IF count er on a single c hip.
Use of BICMOS technology allows the implementa­tion of several tuning function s and a mini mum of ex­ternal components.

2

C-BUS CONTROLLED

2

C-BUS

September 2003

This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice.

1/42

TDA7512

BLOCK DIAGRAM

2/42

PIN CONNECTION (Top view )

AMMIX1IN2
AMMIX1IN1

AMRFAGCIN

AMRFAGCOUT

AMPINDR
FMPINDR

FMMIX1IN1

GNDRF

FMMIX1IN2

FMAGCTC

TV1
TV2

ADJCH

FSU

ISSTC

VCCVCO

MIX1OUT2

MIX1OUT1

63

64

1
2
3
4
5
6
7
8
9

10

12
13
14

15
16

17 18 19 20 21

VCCIF1

AMRFAGCTC

60

61

62

GNDIF1

AMIF1IN/ISS

FMAMP1IN

AMMIX2OUT1

FMAMP1OUT

AMMIX2OUT2

FMIF1REF

FMAMP2IN

FMIF1AGCIN

59 58 57 56 5455 53 52 51 50 49

22 23 24 25 26

271128 29 30 31 32

VCC2

FMAMP2OUT

GNDVCC2

48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33

TDA7512

VREF1
GNDDEM
FMMIX2IN1
FMMIX2IN2
REFDEMC FM/AM
AMIF2IN
MUTETC
AMDETC
AMAGC2TC
AMIFBPF
AMIFREF
MPX/AFAM
VCC1
FSW
AMST/MP
GNDVCC1

SCL

SDA

VCOB

GNDVCO

VCOE

XTALG

DEVTC

XTALD

GNDVCC3

SSTOP

VCC3

LPOUT

PIN DESCRIPTI ON

N° Pin Name Function

1 AMMIX1IN2 AM Input2 Mixer 1
2 AMMIX1IN1 AM Input1 Mixer 1
3 AMRF AGCIN Input AM RF AGC
4 AMRFAGCOUT Output AM RF AGC
5 AMPINDR AM PIN Diode Driver Output
6 FMPINDR FM PIN Diode Driver Output
7 FMMIX1IN1 FM Input1 Mixer1
8 GNDRF RF Ground

9 FMMIX1IN2 FM Input2 Mixer1
10 FMAGCTC FM AGC Time Constant
11 TV1 Tuning Voltage Preselection1

LPAM

VREF2

LPFM

LPHC

TQFP64

12 TV2 Tuning Voltage Preselection2
13 ADJCH Ident. Adjacent Channel Output

3/42

TDA7512

PIN DESCRIPTI ON (continued)

N° Pin Name Function

14 FSU Unweighted Fieldstrength Output
15 ISSTC Time Constant for ISS Filter Switch
16 VCCVCO VCO Supply
17 GNDVCO VCO Ground
18 VCOB VCO Input Base
19 VCOE VCO Output Emitter
20 DEVTC Deviation Detector Time Constant
21 XTALG Xtal Oscillator to MOS Gate
22 XTALD Xtal Oscillator to MOS Drain
23 GNDVCC3 VCC3 Ground
24 SSTOP Search Stop Output
25 SDA

26 SCL

27 VCC3 Supply Tuning Voltage
28 LPOUT O p Amp O u tput to PLL Loop Filters
29 VREF2 Voltage Reference for PLL Op Amp
30 LPAM Op Amp Input to PLL Loop Filters AM
31 LPFM Op Amp Input to PLL Loop Filters FM
32 LPHC High Current PLL Loop Filter Input
33 GNDVCC1 Digital Ground
34 AMST/MP AM Stereo Out / Ident. Multipath Output
35 FSW Weighted Fi eldstrength Output
36 VCC1 Digital Supply
37 MPX/AFAM MPX Output / AM AF Out put
38 AMI FREF Reference Voltage AM IF Amp
39 AMIFBPF AM IF Filter
40 AMAGC2TC AM AGC2 Time Constant

2

C-Bus Da ta

I

2

C-Bus Clock

I

41 AMDETC AM Detector Capacitor
42 MUTETC Softmute Time Constant
43 AMIF2IN Input AM IF2
44 REFDEMC FM/AM Demodulator Reference FM/AM
45 FMMIX2IN2 FM IF1 MIX2 Input1

4/42

PIN DESCRIPTI ON (continued)

N° Pin Name Function

46 FMMIX2IN1 FM IF1 MIX2 Input2
47 GNDDEM Ground FM Demodul ator
48 VREF1 Reference 5V
49 GNDVCC2 Analog Ground
50 FMAMP2OUT FM IF1 Amplifier2 Output
51 VCC2 Analog Supply
52 FMAMP2IN FM IF1 Amplifier2 Input
53 FMIF1REF FM IF1 Amplifier Reference
54 FMAMP1OUT FM IF1 Amplifier1 Output
55 AMMIX2OUT2 AM Tank 450kHz
56 AMMIX2OUT1 AM Tank 450kHz
57 FMAMP1IN FM IF1 Amplifier1 Input
58 AMIF1IN/ISS AM IF1 Input/ISS filter status

TDA7512

59 GNDIF1 FM IF1 Ground
60 FMIF1AGCIN FM IF1 AG C Input
61 VCCIF1 IF1 Supply
62 AMRFAGCTC AM RF AGC Time Constant
63 MIX1OUT2 MIX Tank 10.7MHz
64 MIX1OUT1 MIX Tank 10.7MHz

THERMA L D ATA
Table 1.

Symbol Parameter Value Unit

R

th(j-a)

Thermal resistance junction to ambient 68 max. °C/W

ABSOLUTE MAXIMUM RATINGS
Table 2.

Symbol Parameter Value Unit

V

T

amb

T

stg

Supply Voltage 10.5 V

S

Ambient Temperature -40 to 85 °C
Storage Temperature -55 to +150 °C

5/42

TDA7512

Table 3. ELECTRICAL CHARACTERISTICS

T

= +25°C, V

amb

f

=1kHz, f

MOD

specified.

Symbol Parameter Test Condition Min. Typ. Max. Unit

Supply

= V

CC1

IF1

CC2

=10.7MHz, f

= V

= V

CC3

=450KHz, f

IF2

CCVCO

= V

= V

CCMIX1

= 10.25MHz, in application circuit, unless otherwise

Xtal

=8.5V, fRF= 98MHz, dev. = 40kHz,

CCIF1

V

CC1

V

CC2

V

CC3

V

CCVCO

V

CCMIX1

V

CCMIX2

V

CCIF1

I

CC1

I

CC1

I

CC2

I

CC2

I

CC3

I

CCVCO

I

CCMIX1

I

CCMIX1

Digital supply voltage 7.5 8.5 10 V
Analog supply voltage 7.5 8.5 10 V
Analog tuning voltage 7.5 8.5 10 V
VCO supply voltage 7.5 8.5 10 V
MIX1 supply voltage 7.5 8.5 10 V
MIX2 supply voltage 7.5 8.5 10 V
IF1 supply voltage 7.5 8.5 10 V
Supply current FM ON 7.5 mA
Supply current AM ON 10 mA
Supply current FM ON / VCO:3 70 mA
Supply current AM ON 70 mA
Supply current 2 mA
Supply current 9 mA
Supply current FM ON 8 mA
Supply current AM ON 7 mA

I

CCMIX2

I

CCIF1

Supply current AM ON 7 mA
Supply current 6 mA

Reference Voltages

V
V

REF1

REF2

Internal reference voltage I
Internal reference voltage I

Wide Band RF AGC

V
V

Lower threshold start V10 = 2.5V 85

7-9

Upper threshold start V10 = 2.5V 96

7-9

Narrow Band IF & Keying AGC

V
V

Lower threshold start KAGC = off, V

60

Upper threshold start KAGC = off, V

60

6/42

= 0mA 5 V

REF1

= 0mA 2.5 V

REF2

7-9

7-9

= 0mV
= 0mV

RMS

RMS

86
98

dB
dB

dB
dB

µV
µV

µV
µV

TDA7512

Table 3. ELECTRICAL CHARACTERISTICS (continued)

T

= +25°C, V

amb

f

=1kHz, f

MOD

specified.

Symbol Parameter Test Condition Min. Typ. Max. Unit

= V

CC1

IF1

CC2

=10.7MHz, f

= V

= V

CC3

=450KHz, f

IF2

CCVCO

= V

= V

CCMIX1

= 10.25MHz, in application circuit, unless otherwise

Xtal

=8.5V, fRF= 98MHz, dev. = 40kHz,

CCIF1

V

V

R
C

Lower threshold start with KAGC KAGC = max, V

60

Startpoint KAGC KAGC = max, V

35

Control range KAGC

∆

Input resistance 10

IN

Input capacitanc e 2.5 pF

IN

AGC Time Constant Output

V

V

Max. AGC output voltage V

10

Min. AGC output voltage V

10

I

Min. AGC charge current V

10

I

Max. AGC discharge current V

10

AGC PIN Diode Driver Output

AGC OUT, current min. V

I

6

I

AGC OUT, current max. V

6

= 0mV

∆f

=300KHz

IF

∆f

=300KHz

IF

f

generate FSW level at V

IF1

∆V

= +0.4V

35

= 0mV

7-9

= 50mV

7-9

= 0mV

7-9

= 50mV

7-9

= 0mV

7-9

= 50 mV

7-9

7-9

= 0mV

7-9

RMS

RMS

RMS,V10

RMS

= 2.5V -12.5

RMS,V10

, V6 = 2.5V 50

, V6 = 2.5V -20 mA

RMS

RMS,

RMS,

35

98

3.6 V

dB

16 dB

Ω

k

V

+V

REF1

BE

V

0.5 V

µA

= 2.5V 1.25 mA

µA

µV

I/Q Mixer1 (10.7MHz)

R
C

R

V

g

CP

Input resistance differential 10

IN

Input capacitanc e differential 4 pF

IN

Output resistance differential 100

OUT

Input dc bias 3.2 V

7,9

Conversion transconductance 17 mS

m

F Noise figure

1dB compression point referred to diff. mixer input 100

1dB

Ω generator resistance

400

3dB

IIP3 3rd order intermodulation 122
IQG I/Q gain adjust G -1 +1 %

IQP I/Q phase adjust PH -7 +8 DEG
IRR Image rejection ratio ratio wanted/image 30 40 dB
IRR Image rejection ratio with gain and phase adjust 40 46 dB

dB
dB

k

k

Ω

Ω

µV
µV

7/42

TDA7512

Table 3. ELECTRICAL CHARACTERISTICS (continued)

T

= +25°C, V

amb

f

=1kHz, f

MOD

specified.

Symbol Parameter Test Condition Min. Typ. Max. Unit

IF1 Amplifier1 +2 (10.7MHz)

= V

CC1

IF1

CC2

=10.7MHz, f

= V

= V

CC3

=450KHz, f

IF2

CCVCO

= V

= V

CCMIX1

= 10.25MHz, in application circuit, unless otherwise

Xtal

=8.5V, fRF= 98MHz, dev. = 40kHz,

CCIF1

G

G

R

R

CP

IIP3 3rd order Intermodulation

Min. gain IFG 18 dB

min

Max. gain IFG

max

Input resistance 330

IN

Output resistance 330

OUT

1dB compression point

1dB

referred to 330
referred to 330

Ω input
Ω input

26

105

126

Mixer2 (450kHz)

R
V

V

Input impedance 330

IN

Max. input voltage 900 mV

46

Limiting sensitivity S/N = 20dB 25

48

G Mixer gain 18 dB

Limiter 1 (450kHz)

G

Limiter

Gain 80 dB

Demodulator, Audio Output

THD Dev.= 75kHz, V

= 10mV

46

RMS

0.1 %

dB

Ω
Ω

dBµV
dBµV

Ω

RM

S

µV

V

R

|∆V|

∆V|

|

MPX output signal Dev.= 75kHz 500 mV

MPX

Output resistance 50

OUT

DC offset fine adjust DEM, MENA=1 8.5 mV

min

DC offset fine adjust DEM, MENA=1 264 mV

max

S/N Dev.= 40kHz,V

Quality Detection
S-meter, Unweighted Fieldstrength

V
V
V

∆V
∆V

Min. input voltage MIX2 10

46

Fieldstrength output V46 = 0V

14

Fieldstrength output V46 = 1V

14

voltage per decade SMSL = 0 1 V

14

voltage per decade SMSL = 1 1.5 V

14

8/42

RMS

RMS

= 10mV

46

RMS

RM

S

Ω

76 dB

µV

0.1 V

4.9 V

TDA7512

Table 3. ELECTRICAL CHARACTERISTICS (continued)

T

= +25°C, V

amb

f

=1kHz, f

MOD

specified.

Symbol Parameter Test Condition Min. Typ. Max. Unit

= V

CC1

IF1

CC2

=10.7MHz, f

= V

= V

CC3

=450KHz, f

IF2

CCVCO

= V

= V

CCMIX1

= 10.25MHz, in application circuit, unless otherwise

Xtal

=8.5V, fRF= 98MHz, dev. = 40kHz,

CCIF1

∆V

R

S-meter offset SL, SMSL=1 -15 15 dB

14

Output resistance 200

OUT

TK Temp coeff. 0 ppm/K

S-meter, Weighted Fieldstrength

R

V
V

OUT

Fieldstrength output V46 = 0V

35

Fieldstrength output V46 = 1V

35

RMS

RMS

Output resistance 12

2.5 V

4.9 V

Adjacent Channel Gain

G

G

Gain minimum ACG=0 32 dB

min

Gain maximum ACG=1 38 dB

max

Adjacent Channel Filter

f
f

f

-20dB

-3dB frequency highpass ACF=0 100 kHz

HP

Centre frequency ACF=1 100 kHz

BP

Attenuation 20dB 70 kHz

Adjacent Channel Output

V

Output voltage low 0.1 V

13

Ω

Ω

k

V

R

Output voltage high 4.9 V

13

Output resistance 4

OUT

Multipath Channel Gain

G

G

Gain minimum MPG=0 12 dB

min

Gain maximum MPG=1 23 dB

max

Multipath Bandpass Filter

f

Lower

f

Upper

Centre frequency low MPF=0 19 kHz
Centre frequency up MPF=1 31 kHz

Q Quality factor 5 10

Multipath Output

V
V

R

Output voltage low 0.1 V

34

Output voltage high 4.9 V

34

Output resistance 2.5

OUT

k

k

Ω

Ω

9/42

TDA7512

Table 3. ELECTRICAL CHARACTERISTICS (continued)

T

= +25°C, V

amb

f

=1kHz, f

MOD

specified.

Symbol Parameter Test Condition Min. Typ. Max. Unit
ISS (intelligent Selectivity System)
Filter 450kHz

= V

CC1

IF1

CC2

=10.7MHz, f

= V

= V

CC3

=450KHz, f

IF2

CCVCO

= V

= V

CCMIX1

= 10.25MHz, in application circuit, unless otherwise

Xtal

=8.5V, fRF= 98MHz, dev. = 40kHz,

CCIF1

f

centre

Centre frequency f

REF_intern

= 450kHz 450 kHz

BW 3dB Bandwidth, -3dB ISS80 = 1 80 kHz

BW

Bandwidth, -20dB ISS80 = 1 150 kHz

20dB

BW 3dB Bandwidth, -3dB ISS80 = 0 120 kHz

BW

Bandwidth, -20dB ISS80 = 0 250 kHz

20dB

BW 3dB Bandwidth weather band ISS30 = 1 30 kHz

BW

-20dB weather band ISS30 = 1 80 kHz

20dB

Adjacent Channel ISS Filter Threshold

V

V
V
V

Internal low threshold ACNTH 0 V

NTH

Internal high threshold ACNTH 0.3 V

NTH

Internal low threshold ACWTH 0.25 V

WTH

Internal high threshold ACWTH

WTH

0.95

Multipath Threshold

V

THMP

Internal low threshold MPTH 0.50 V

V

V

THMP

Internal high threshold MPTH 1.25 V

ISS Filter Time Constant

Charge current low mid TISS, ISSCTL = 1 -74

I

15

I

Charge current high mid TISS, ISSCTL = 1 -60

15

I

Charge current low narrow TISS, ISSCTL = 1 -124

15

I

Charge current high narrow TISS, ISSCTL = 1 -110

15

I

Discharge current low TISS, ISSCTL = 0

15

I

Discharge current high TISS, ISSCTL = 0 15

15

V

Low voltage ISSCTL = 0 0.1 V

15

10/42

µA
µA
µA
µA

1

µA
µA

TDA7512

Table 3. ELECTRICAL CHARACTERISTICS (continued)

T

= +25°C, V

amb

f

=1kHz, f

MOD

specified.

Symbol Parameter Test Condition Min. Typ. Max. Unit

= V

CC1

IF1

CC2

=10.7MHz, f

= V

= V

CC3

=450KHz, f

IF2

CCVCO

= V

= V

CCMIX1

= 10.25MHz, in application circuit, unless otherwise

Xtal

=8.5V, fRF= 98MHz, dev. = 40kHz,

CCIF1

V

High voltage ISSCTL = 1 4.9 V

15

ISS Filter Switch Threshold

V

15

V

15

V

15

V

15

I

20

I

20

I

20

I

20

DEV
DEV
RATIO

n

RATIO

Threshold ISS on ISSCTL = 0 3 V
Threshold ISS off ISSCTL = 0 1 V
Threshold ISS narrow on ISSCTL = 0 4 V
Threshold ISS narrow off ISSCTL = 0 2 V
Charge current low TDEV -20
Charge current high TDEV -34
Discharge current low TDEV 6
Discharge current high TDEV 20
Internal low threshold DWTH 30 kHz

WTH

Internal high threshold DWTH 75 kHz

WTH

Referred to threshold DTH 1

mi

Referred to threshold DTH 1.5

m

ax

Softmute

µA
µA
µA
µA

V

ANT

V

ANT

a

SMmin

a

SMmax

a

SMTHIS

S

V

ACTH

a

SMAC

I

42

I

42

S/N Over All

S/N

Upper startpoint SMTH, SMD, SLOPE = 0 10
lower startpoint SMTH, SMD, SLOPE = 0 3
Min. softmute depth SMD, SLOPE = 0, SMTH
Max. softmute depth SMD, SLOPE = 0, SMTH

Upper

Upper

18 dB
36 dB

dB
dB

Mute depth threshold for ISS filter onSMCTH 0.2 2 dB

Internal AC mute threshold ACM 60 340 mV
AC mute depth ACMD 4 10 dB
Charge current -47.5
Discharge current 2.5

V

ANT_min

= 60dBµV,

66 dB

µA
µA

dev.= 40kHz,LP=15KHz
deemphasis t = 50

µs

11/42

µV
µV

TDA7512

Table 4. ELECTRICAL CHARACTERISTICS

T

= +25°C, V

amb

30% AMf
V

antenna input).

INRF

= 10.7MHz, f

IF1

Symbol Parameter Test Condition Min. Typ. Max. Unit

Global

CC1

= V

= V

CC2

=450kHz, f

IF2

CC3

= V

= V

CCVCO

= 10.25MHz, in application circuit, (unless ot herwise noted,

xtal

CCMIX1

= V

=8.5V, fRF=1MHz, f

CCMIX2

MOD

= 400Hz at

ANT

Max. sensitivity

Ref.: V

= 60dBµV,

INRF

V

min

us Usable sensitivity (S+N)/N = 20 dB 30 26

V

ANT

∆V

(S+N)/N Signal to Noise Ratio

a

IF2 AGC Range

ANT

IF rejection

IF

Ref.: V
Ref.: V
Ref: V

= 60dBµV,

INRF

= 60ddBµV

INRF

= 60dBµV,

INRF

IF1 = 10.7MHz
IF2 = 450kHz

f

THD Total Harmonic Distortion

Frequency response

AF

Ref.: V

∆V

AF

V

INRF

= 60dBµV,

INRF

= -3 dB

= 60dBµV, m = 0.8

m = 0.3
V

= 120 dbµV, m = 0.8

INRF

m = 0.3

V

V

Output level

37

Output level

34

V

Min. RF AGC threshold

3

= 60dBµV

V

INRF

= 60dBµ, m=off

V

INRF

WAGC 90

Max. RF AGC threshold

19

dBµV

dB
56 dB
50 60 dB

100
100

3.6 kHz

0.5

0.3

1.0

0.3

220 mV

190 mV

dB

109

dB

µV

dB
dB

%

RM

S

RM

S

µV
µV

V

Min. IF AGC threshold

58

WAGC 90

Max. IF AGC threshold

V

Min. DAGC threshold

58

DAGC 74

Max. DAGC threshold

|I

| AGC2 charge current se ek 160

40max

CCR Charge current ratio seek/seek off 30

AGC Voltage Driver Output

Max. AGC output voltage 3.5 V

V

4

V

Min. AGC output voltage

4

| AGC current 100

| I

4

AGC PIN Diode Driver Output

AGC driver current -2 mA

I

5

12/42

109

96

0.5

dB

dB

dB

dB

µV
µV

µV
µV

µA

V

µA

TDA7512

Table 4. ELECTRICAL CHARACTERISTICS (continued)

T

= +25°C, V

amb

30% AMf
V

antenna input).

INRF

= 10.7MHz, f

IF1

Symbol Parameter Test Condition Min. Typ. Max. Unit

AM Mixer1 (10.7MHz)

CC1

= V

= V

CC2

=450kHz, f

IF2

CC3

= V

= V

CCVCO

= 10.25MHz, in application circuit, (unless ot herwise noted,

xtal

CCMIX1

= V

=8.5V, fRF=1MHz, f

CCMIX2

MOD

= 400Hz at

R
C

R

CP

IIP3 3rd order intermodulation 132

Input resistance differential 1.2

IN

Input capacitanc e differential 4 pF

IN

Output impedance differential 100

OUT

1dB compression point referred to diff. mixer input 115

1dB

Ω

k

Ω

k

µV

dB

dBµV

F Noise figure 8dB

A Gain 26 dB

Min. capacitance step IF1T 0.55 pF

min

Max. capacitance IF1T 8.25 pF

max

IF1T 2 pF

C

C

C

31-64

AM Mixer2 (450kHz)

R
C

CP

IIP3 3rd order intermodulation 132

Input resistance 10

58

Input capacitanc e 2.5 pF

58

1dB compression point referred to diff. mixer input 120

1dB

dB

dB

Ω

k

µV
µV

F Noise figure 12 dB

A Max. gain Mixer2 tank output 34 dB

Gain control range 20 dB
Min. cap step IF2T 1.6 pF

min

Max. cap IF2T 24 pF

max

IF2T 2 pF

C

C

∆A

C

55-56

13/42