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CXA3668N
Reception Analog Signal Processor IC for Infrared Space Digital Audio Communication
Description The CXA3668N is an IC that performs reception side analog signal processing for optical communication in combination with an infrared photodiode within a Digital Infrared Audio Transmission (DIAT) system. This IC incorporates a low noise trans-conductance amplifier (I/V amplifier) that converts the optical current from the photodiode into a voltage and amplifies it, an AGC amplifier, a low-pass filter, bandpass filters, and an output amplifier. The band-pass filters are used to separate the desired signal and the interfering signal. This chip has the two types of Full (3 to 6MHz) and Half (3 to 4.5MHz) band-pass filters, and these can be switched according to the application. * Full: Full-band width (3 to 6MHz) * Half: Half-band width (3 to 4.5MHz) Features * Wide dynamic range * On-chip I/V amplifier * On-chip output filter * Filter band switching pin * Surface mounting package (24-pin SSOP) Applications * Infrared headphones * Infrared speakers Structure Bi-CMOS IC Absolute Maximum Ratings * Supply voltage * Storage temperature * Allowable power dissipation (Ta = 25C) VCCI, VCC2, VCCS, VCCO Tstg PD 24 pin SSOP (Plastic)
3.3 V -55 to +150 C 400 mW
Recommended Operating Conditions * Supply voltage VCCI, VCC2, VCCS, VCCO * Operating temperature Topr
2.3 to 2.7 -40 to +85
V C
Sony reserves the right to change products and specifications without prior notice. This information does not convey any license by any implication or otherwise under any patents or other right. Application circuits shown, if any, are typical examples illustrating the operation of the devices. Sony cannot assume responsibility for any problems arising out of the use of these circuits.
-1-
E04244-PS
Pin Configuration and Block Diagram
AGCIREF3 AGCIREF2 AGCCAP1 AGCCAP2
GND2
VCCO
DIVCODE
GNDO
VCC2
24
23
22
21
20
19 comp Vcc - 0.5V
OUT
DET
18
17
16
15
14
13
BIAS comp FWR
4k S/D CONV I/V AMP 0deg 180deg GCA LPF fc = DIVCODE_H: 6MHz DIVCODE_L: 4.5MHz HPF fc = 3MHz
PREAMP
OUTPUT_AMP
0deg FWR 180deg
FWR
comp
CONT GNDMOS
1
AGCIREF1
2
GNDMOS
3
SIS
4
VCCI
5
IN
6
GNDI
7
AGCIN
8
GNDS
9
GNDR
10
GNDR
11
GNDR
12
GNDR
VCCS
-2-
CXA3668N
CXA3668N
Pin Description Pin No. Symbol I/O Standard voltage level
Vcc2
Equivalent circuit
Description
1
AGCIREF1
0.2V
1
Reference current generation for determining the input AGC attack time. Connect to GND2 through a 390 or more resistor. Reducing the resistance value shortens the attack time. Input block shunt GND.
GND2
2
GNDMOS
GND
Vcc2 Vcc1
3
3
SIS
O
0V
2 GND2
Shunt input. This shunts the optical current of the photodiode and applies the AGC.
4
VCCI
+2.5V (Typ.)
VccI
Input block power supply.
5
IN
I
0.8V
5
Photodiode input. This is the current-voltage conversion input for amplifying the photodiode current. Input impedance: approximately 60
GNDI
6
GNDI
GND
Vcc2
Input block GND.
7
AGCIN
I
1.1V
7
AGC input.
GND2
8
GNDS
GND GND +2.5V (Typ.) -3-
Signal processing block GND. GND. Signal processing block power supply.
9, 10, GNDR 11, 12 13 VCCS
CXA3668N
Pin No.
Symbol
I/O
Standard voltage level
VccS
Equivalent circuit
Description Filter characteristics switching. * Low: Full-band BPF (3 to 6MHz) * High: Half-band BPF (3 to 4.5MHz) Logic level: * Low: 0 to 0.5V * High: 1.5V to VCC Output amplifier block GND.
14
DIVCODE
I
14
GNDS
15
GNDO
GND
VccO
16
Signal output. The load capacitance should be as small as possible to ensure stable output. * Load resistance: 3k or more * Load capacitance: 18pF or less
16
OUT
O
1.25V
GNDO
17
VCCO
+2.5V (Typ.)
Vcc2
Output amplifier block power supply. Input level detection. This detects whether the input level is the prescribed value, and outputs the judgment results. This pin outputs low when the input level is 0.05Ap-p or less, and high when the input level is 0.3Ap-p or more. AGC GND.
Vcc2
18
DET
O
18
GND2
19
GND2
GND
20
20
AGCCAP2
AGC2 response setting. Connect to VCC2 through a capacitor.
GND2
-4-
CXA3668N
Pin No.
Symbol
I/O
Standard voltage level
Vcc2
Equivalent circuit
Description
21
AGCIREF2
0.2V
21
Reference current generation for determining the AGC2 attack time. Connect to GND2 through a 390 or more resistor. Reducing the resistance value shortens the attack time.
GND2
22
VCC2
+2.5V (Typ.)
Vcc2
AGC power supply.
23
AGCIREF3
1.25V
23
Reference current generation for determining the input AGC and the AGC2 recovery time. Connect to VCC2 through a 33k resistor.
GND2
Vcc2
24
24
AGCCAP1
Input AGC response setting. Connect to VCC2 through a capacitor.
GND2
-5-
CXA3668N
Electrical Characteristics Item Supply voltage VCC Current consumption (1) ICC1 (H) Current consumption difference (2) dICC1 (L) AGC variable range Output amplitude (1) Output amplitude (2) [BPF characteristics] Full BPF-1 Full BPF-2 Full BPF-3 Full BPF-4 Half Low BPF-1 Half Low BPF-2 Half Low BPF-3 Half Low BPF-4 S/N (1) S/N (2) Output secondary distortion < 2.0/4.5MHz 3.15/4.5MHz 5.85/4.5MHz > 8.0/4.5MHz < 2.0/3.75MHz 3.15/3.75MHz 4.35/3.75MHz > 5.8/3.75MHz 100Ap-p input 0.1Ap-p input 100Ap-p input Conditions (VCCI, VCC2, VCCS, VCCO = VCC) 100Ap-p, ICC total
(Ta = 25C, VCCI, VCC2, VCCS, VCCO = 2.5V) Min. 2.3 10 -100 72 0.2 1.5 -- -3 -3 -- -- -3 -3 -- 40 20 30 -- -- -- 0 0 -- -- 0 0 -- -- -- -- -- 2.0 -30 3 3 -36.1 -30 3 3 -36.1 -- -- -- Typ. 2.5 18 30 Max. 2.7 25 100 Unit V mA A dB Vp-p Vp-p dB dB dB dB dB dB dB dB dB dB dB
300Ap-p, dICC1 (L) = ICC1 (L) - ICC1 Input signal (1mAp-p/0.25Ap-p) 0.1Ap-p input, load 3k, 18pF 100Ap-p input, load 3k, 18pF
-6-
Electrical Characteristics Measurement Circuit
VCC VCC VCC VCC
VCC 10 0.01 DET VCC Gain control
VCC
VCC 6k 6k
Full-band mode; 0.5V Half-band mode; VCC - 0.5V VCC OUTPUT 18p
4700p
33k
0.1 22 21
1.5k 20
0.1 18 17 16 15 14 13
0.1
24
23
19
GNDO
AGCIREF2
AGCCAP1
AGCIREF3
AGCCAP2
comp Vcc - 0.5V
BIAS comp FWR
4k S/D CONV I/V AMP 0deg 180deg GCA LPF fc = DIVCODE_H: 6MHz DIVCODE_L: 4.5MHz HPF fc = 3MHz
PREAMP
OUTPUT_AMP
0deg FWR 180deg
FWR
comp
CONT GNDMOS
AGCIREF1
GNDMOS
AGCIN
GNDR
GNDR
GNDR
DIVCODE
GND2
VCCO
SIS
1 1k
2
3 VCC
4 0.1
5 6800p 6800p
6
7 100p
8
9
10
11
12
1k 100p
GNDR
GNDS
GNDI
VCCI
IN
VCCS
VCC2
DET
OUT
-7-
CXA3668N
6.8 22p
CXA3668N
Description of Operation (1) Trans-impedance amplifier circuit (I/V amplifier) The input block is comprised of the trans-impedance amplifier circuit which converts the optical current Ip from the photodiode into a current, and the AGCATT circuit. Fig. 1 shows the I/V amplifier equivalent circuit.
Zt Zt: Trans-impedance A: Amplifier gain vi i -A vo
Fig. 1 The following equations are satisfied in the circuit shown in Fig. 1. vo = -A x vi vi - vo = i x Zt The input impedance Zi of the I/V amplifier is obtained from these equations as follows. Zi = vi/i = Zt/ (1 + A) The trans-impedance Zt of this IC is 4k (typ.) and the amplifier gain A is 65 times (typ.), so Zi is 60.6 (typ.). (2) AGC ATT The IC operates at an input optical current of up to 1mAp-p (max.), so the trans-impedance input current It is controlled so that the trans-impedance amplifier circuit does not produce a saturated state. Labeling the SIS impedance as Zs, It = Ip x Zs/(Zs + Zin). It is controlled so that the trans-impedance amplifier circuit output does not go to 250mVp-p or more, and when Ip is 63.5Ap-p or less, It = Ip (Zs >> Zin). When Ip is 63.5Ap-p or more and 1mAp-p or less, Zs decreases and Ip goes to 63.5Ap-p so that the transimpedance output level is 250mVp-p. * The AGC ATT attack time and recovery time response are as follows. The attack time and the recovery time are determined by the capacitor Ca connected between AGCCAP1 (Pin 24) and VCC2. Increasing the Ca value lengthens both the attack time and the recovery time, and reducing the Ca value shortens both the attack time and the recovery time. The reference current (Iat = 0.2/Raa) used to determine the attack time is determined by the resistor Raa connected between AGCIREF1 (Pin 1) and GND. Reducing the resistance value increases the reference current and shortens the attack time. Increasing the resistance value lengthens the attack time. The reference current (Iar = 0.625/Rar) used to determine the recovery time is determined by the resistor Rar connected between AGCIREF3 (Pin 23) and VCC. Use a Rar of 33k. -8-
CXA3668N
(3) IN frequency response Fig. 2 shows the IN input circuit.
Cd
Pd C2
SIS
C3
IN
Vd
L
C1 Zs Zi
Vd: Photodiode bias voltage Cd: Photodiode junction capacitor Pd: Photodiode L: External inductor C1, C2, C3: External capacitors Zs: SIS pin impedance Zi: I/V amplifier input impedance
Fig. 2 (1) When the photodiode current Ip 63.5Ap-p Zs goes to 100k and can be ignored. The circuit in Fig. 2 can be expressed by the equivalent circuit in Fig. 3.
C5 IN Ip L C4 Zi
Fig. 3 However, C4 and C5 are as follows. C4 = C1 + Cd C5 = C2/2 (however, C2 = C3) The IN voltage VI is obtained from the equivalent circuit in Fig. 3 as follows. S2 C4 S3 +
VI =
(
1 1 + C4 C5
)
s2 s 1 + + Zi C4L C4C5LZi
x Ip
VI/Ip (Ga) is as follows. - 2 C4
Ga =
VI = Ip
[
1 1 1 - + C4C5LZi C4 C5
(
)](
+j
2 Zi
1 + C4L C4C5LZi
)
When set to Cd = 72pF, C1 = 47pF, L = 6.8H, and C2 = C3 = 6800pF, the Ga frequency response is as shown in Fig. 4.
-9-
CXA3668N
INPUT frequency response
(Ta = 25C, VCC = 2.5V) 40 35 30 25 Gain [dB] 20 15 10 5 0 -5 -10 0.1 1 Frequency [MHz] 10 100
Fig. 4 Set L, C1, C2 and C3 so that the gain is flat from the 3MHz band to the 6MHz band.
(2) When the photodiode current Ip > 63.5Ap-p Labeling the Ip peak-to-peak size as Ipp, Zs in Fig. 2 is as follows. Rsis = 233 x 10-3 60.6 x Ipp - 3.85 x 10-3
In addition, the circuit in Fig. 2 can be expressed by the equivalent circuit in Fig. 5.
C2 C4 Rsis Zi C3 IN (VI) Ip L
Fig. 5 However, C4 = Cp + C1. When set to Cd = 72pF, C1 = 47pF, L = 6.8H, and C2 = C3 = 6800pF, the VI/Ip frequency response at Ipp = 100Ap-p, 300Ap-p and 1mAp-p are as shown in Fig. 6.
- 10 -
CXA3668N
INPUT frequency response
(Ta = 25C, VCC = 2.5V) 40 30 20 10
Gain [dB]
0 -10 -20 -30 -40 0.1
Ip = 100Ap-p Ip = 300Ap-p Ip = 1mAp-p
1 Frequency [MHz]
10
100
Fig. 6
(4) AGCIN The signal input from AGCIN (Pin 7) and the I/V amplifier output signal are added and converted to a differential signal. This differential signal is input to the gain control amplifier (GCA), and the GCA output is input to the filter. When using AGCIN, input through a coupling capacitor C (100pF). When not using AGCIN, connect it to GND through C (100pF). (5) Band-pass filter Full-band mode and Half-band mode can be selected by the DIVCODE (Pin 14) pin voltage. The cutoff frequencies (fc) for the Full-band and Half-band modes which correspond to the DIVCODE pin voltage are as follows. DIVCODE Low High Mode Full-band (3MHz to 6MHz) Half-band (3MHz to 4.5MHz)
High; 1.5V to VCC, Low; 0 to 0.5V
- 11 -
CXA3668N
(6) AGC2 The band-pass filter output is amplified to 4 times by the preamplifier, and the GCA gain is varied so that the preamplifier output is approximately 0.8Vp-p. The preamplifier output is converted from a differential signal to a single signal by a subtracter with a gain of approximately 2.1 times, and is then output from OUT (Pin 16) at a level of approximately 1.7Vp-p. * The AGC2 attack time and recovery time response are as follows. The attack time and the recovery time are determined by the capacitor Ca2 connected between AGCCAP2 (Pin 20) and VCC2. Increasing the Ca2 value lengthens both the attack time and the recovery time, and reducing the Ca2 value shortens both the attack time and the recovery time. The reference current (Iat2 = 0.2/Raa2) used to determine the attack time is determined by the resistor Raa2 connected between AGCIREF2 (Pin 21) and GND. Reducing the resistance value increases the reference current and shortens the attack time. Increasing the resistance value lengthens the attack time. The reference current used to determine the recovery time is determined by the resistor Rar connected between AGCIREF3 (Pin 23) and VCC. (7) DET When the GCA input level is so low that the AGC2 does not operate (typ.; Ip = less than 0.15Ap-p), DET (Pin 18) goes low. When the GCA input level is high enough for the AGC2 to operate (typ.; Ip = 0.15Ap-p or more), DET goes high.
- 12 -
Application Circuit
2.5V
DET
OUT
DIVCODE
10 4700p 24 AGCCAP1 23 AGCIREF3 33k 22 VCC2 0.1 1.5k 21 AGCIREF2 20 AGCCAP2 0.01 19 GND2 18 DET 17 VCCO 0.1 16 OUT 15 GNDO 14 DIVCODE 13 VCCS 12 GNDR 0.1
comp Vcc - 0.5V
BIAS comp FWR
4k S/D CONV I/V AMP 0deg 180deg GCA LPF fc = DIVCODE_H: 6MHz DIVCODE_L: 4.5MHz HPF fc = 3MHz
AGCIREF1
GNDMOS
AGCIN
GNDR
GNDR
1
2
3
4 0.1
5 6800p
6
7
8
9
10
11
100p 1k PD 0.1 VB 100p 22p 6800p 6.8 AGCIN
GNDR
GNDS
GNDI
VCCI
SIS
IN
- 13 -
PREAMP
OUTPUT_AMP
0deg FWR 180deg
FWR
comp
CONT GNDMOS
CXA3668N
Application circuits shown are typical examples illustrating the operation of the devices. Sony cannot assume responsibility for any problems arising out of the use of these circuits or for any infringement of third party patent and other right due to same.
CXA3668N
Notes on Operation Care should be taken for the following points when using the CXA3668N. * This IC has a high I/O gain (particularly during no signal or weak signal input of 0.15Ap-p (typ.) or less at which the AGC does not operate), so care should be taken for the power supply and GND pattern when designing the printed circuit board. The power supplies and GND are divided by function block as follows. 1) Input block Power supply: VCCI GND: GNDI 2) Input block shunt GND: GNDMOS 3) AGC block Power supply: VCC2 GND: GND2 4) Filter block Power supply: VCCS GND: GNDS 5) Output block Power supply: VCCO GND: GNDO 6) Other GND: GNDR Using tantalum, ceramic or other chip capacitors with excellent frequency response to decouple the power supply and GND pins of each function block is recommended. These capacitors should be connected between the pins as close to the respective IC pins as possible. The pattern should be designed as short and wide as possible. In addition, shielding each external circuit (particularly the input circuit connected to the IN pin) is recommended to prevent spatial crosstalk from the output circuit, etc.
- 14 -
CXA3668N
Example of Representative Characteristics (Ta = 25C, VCCI, VCC2, VCCS, VCCO = 2.5V)
Output voltage vs. Input current
10 0 10
Output voltage [Vp-p]
Input current vs. SNR
20
SNR [dB]
30 40 50 60
1
0.1 0.01
0.10
1.00
10.00
100.00 1000.00
70 0.01
0.1
1
10
100
1000
Input current [Ap-p]
Input current [Ap-p]
Output voltage vs. Temperature 2ndary distortion vs. Input current
60 2.00 1.75
Output voltage [Vp-p]
Input current = 100Ap-p Freq. = 4.5MHz
50
2ndary distortion [dB]
1.50 1.25 1.00 0.75 0.50
40
30
20
10 0.25 0 0.01 0 -50
0.1
1
10
100
1000
0
50
100
Input current [Ap-p]
Temperature [C]
Filter characteristic Full-band mode
10 0 -10
Gain [dB] Gain [dB]
Filter characteristic Half-band mode
10 0 -10 -20 -30 -40 -50 -60
-20 -30 -40 -50 -60 1 2 3 4 5 6 7 8 9 10 Frequency [MHz]
1
2
3
4
5
6
7
8
9
10
Frequency [MHz]
- 15 -
CXA3668N
Package Outline
Unit: mm
24PIN SSOP (PLASTIC)
+ 0.2 1.25 - 0.1 7.8 0.1 0.1 13
24
A
1 b
12
0.13 M B 0.65
5.6 0.1
b=0.22 0.03 0.1 0.1
0.5 0.2
DETAIL B : PALLADIUM
0 to 10 NOTE: Dimension "" does not include mold protrusion. DETAIL A
PACKAGE STRUCTURE
PACKAGE MATERIAL EPOXY RESIN PALLADIUM PLATING COPPER ALLOY 0.1g LEAD TREATMENT LEAD MATERIAL PACKAGE MASS
SONY CODE EIAJ CODE JEDEC CODE
SSOP-24P-L01 P-SSOP24-7.8x5.6-0.65
+ 0.03 0.15 - 0.01
7.6 0.2
- 16 -
Sony Corporation

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