SN761643
www.ti.com ..................................................................................................................................................................................................... SLES246 – APRIL 2009
AGC AMPLIFIER
FEATURES
1
•
•
•
•
Low-Distortion Automatic Gain Control (AGC)
Amplifier
5-V Power Supply
8-Pin Mini Small-Outline Package (MSOP)
Wide Gain Control Range
APPLICATIONS
•
•
•
Digital TVs
Digital CATVs
Digital Set-Top Boxes (STBs)
DGK PACKAGE
(TOP VIEW)
VCC
1
8
GND1
IN1 2
7
OUT1
IN2 3
6
OUT2
5
GND2
AGC 4
AGC Control
DESCRIPTION
The SN761643 is an automatic gain control (AGC) amplifier for the TV tuner system of a digital TV, CATV, or
STB. The circuit consists of three stages of controlled-gain amplification, followed by a fixed-gain output
amplifier.
The device is packaged in an 8-pin MSOP suitable for surface mounting.
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2009, Texas Instruments Incorporated
SN761643
SLES246 – APRIL 2009 ..................................................................................................................................................................................................... www.ti.com
TERMINAL FUNCTIONS
TERMINAL
NAME
NO.
I/O
EQUIVALENT CIRCUIT
DESCRIPTION
60 Ω
4
AGC
4
I
Gain control voltage input
100 kΩ
GND1
8
GND2
5
Power amplifier ground
–
Pre-amplifier ground
Vbias
1 kΩ
1 kΩ
2
IN1
IN2
2
3
I
OUT1
OUT2
7
6
O
3
AGC amplifier input
AGC amplifier output
15 Ω
6
7
VCC
1
–
5-V power supply
Correct Use
(See Note A)
Pre-amplifier
Power Amplifier
IN1
OUT1
IN2
OUT2
GND2
GND1
(See Note B)
2
A.
Be careful to keep enough isolation between input and output line.
B.
Form a ground pattern as widely as possible. GND1 and GND2 should not have common impedance.
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SN761643
www.ti.com ..................................................................................................................................................................................................... SLES246 – APRIL 2009
ABSOLUTE MAXIMUM RATINGS (1)
over operating free-air temperature range (unless otherwise noted)
MIN
MAX
VCC
Supply voltage range (2)
VCC (pin 1)
–0.4
6.5
V
VI
Input voltage range (2)
AGC (pin 4)
–0.4
VCC
V
477
mW
150
°C
(3)
PD
Continuous total dissipation
TJC
Maximum junction temperature
(1)
(2)
(3)
UNIT
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating
Conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
Voltage values are with respect to the GND of the circuit.
At TA ≤ 25°C. For TA > 25°C, the derating factor is 3.82 mW/°C.
RECOMMENDED OPERATING CONDITIONS
MIN
VCC
Supply voltage
4.5
TOPE
Operating free-air temperature
–20
NOM MAX
5
UNIT
5.5
V
85
°C
DC ELECTRICAL CHARACTERISTICS
VCC = 5 V, TA = 25°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
ICC
Supply current
VAGC = 3 V
28
IIAGC
Input current (AGC)
VAGC = 3 V
30
VAGCMAX
AGC maximum gain control voltage
Maximum gain
VAGCMIN
AGC minimum gain control voltage
Minimum gain
MAX
UNIT
mA
60
µA
3
VCC
V
0
0.2
V
AC ELECTRICAL CHARACTERISTICS
VCC = 5 V, TA = 25°C, parameters measured in test circuit (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
GMAX1
Maximum gain 1
VAGC = 3 V, fIN = 44 MHz, VIN = –60 dBm,
differential out, see Figure 10
57
61
65
dB
GMIN1
Minimum gain 1
VAGC = 0 V, fIN = 44 MHz, VIN = –60 dBm,
differential out, see Figure 10
–7
–4
–1
dB
GMAX2
Maximum gain 2
VAGC = 3 V, fIN = 44 MHz, VIN = –60 dBm, see
Figure 1 and Figure 11
51
55
59
dB
GMIN2
Minimum gain 2
VAGC = 0 V, fIN = 44 MHz, VIN = –60 dBm, see
Figure 1 and Figure 11
–13
–10
–7
dB
GCR
Gain control range
VAGC = 0 V to 3 V
65
dB
VOUT
Output voltage
Single-ended output, see Figure 3
2.1
Vp-p
NF
Noise figure
Maximum gain, see Figure 2
11
dB
IM3
Third-order intermodulation distortion
fIN1 = 43.5 MHz, fIN2 = 44.5 MHz, Maximum gain,
VOUT = –2 dBm/tone, 1Vp-p
See Figure 5 and Figure 12
–50
dBc
IIP3
Input intercept point
Minimum gain
11
dBm
rIN
Input resistance (IN1, IN2)
1
kΩ
rOUT
Output resistance (OUT1, OUT2)
25
Ω
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SN761643
SLES246 – APRIL 2009 ..................................................................................................................................................................................................... www.ti.com
TYPICAL CHARACTERISTICS
35
60
50
30
25
30
NF (dB)
Gain (dB)
40
20
10
15
VCC = 4.5 V
VCC = 5 V
VCC = 5.5 V
0
–10
–20
0.0
20
10
5
0.5
1.0
1.5
AGC (V)
2.0
2.5
10
3.0
Figure 1. Gain vs AGC (TA = 25°C)
15
20
25
30 35 40
Gain (dB)
45
50
55
60
Figure 2. Noise Figure vs Gain (VCC = 5 V, TA = 25°C)
60
30
20
50
0
40
–10
Gain (dB)
Output Level (dBm)
10
–20
–30
–40
–50
Maximum gain
–60
Minimum gain
30
20
10
–70
–80
–70
–60
–50
–40 –30 –20
Input Level (dBm)
–10
0
0
10
10
Figure 3. Output Level vs Input Level (TA = 25°C)
10
–10
Output Level (dBm)
Output Level (dBm)
0
–20
42.5 MHz
43.5 MHz
–30
–40
–50
–60
–70
–80
0
10
20
30
Gain (dB)
40
50
Figure 5. IM3 vs Gain (VCC = 5 V, TA = 25°C)
4
100
Frequency (MHz)
60
Figure 4. Gain vs Frequency (Gain = Max, TA = 25°C)
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
–35 –30 –25 –20 –15 –10 –5
VIN (dBm)
42.5 MHz
43.5 MHz
0
5
10
15
Figure 6. IM3 (Gain = Min, VCC = 5 V, TA = 25°C)
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www.ti.com ..................................................................................................................................................................................................... SLES246 – APRIL 2009
Output Level (dBm)
TYPICAL CHARACTERISTICS (continued)
20
10
0
–10
–20
–30
–40
–50
–60
–70
42.5 MHz
43.5 MHz
–80
–90
–100
–80 –75 –70 –65 –60 –55 –50 –45 –40 –35 –30
VIN (dBm)
Figure 7. IM3 (Gain = Max, VCC = 5 V, TA = 25°C)
S-Parameter
20 MHz
70 MHz
20 MHz
70 MHz
Figure 8. IN1
Figure 9. OUT1
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SN761643
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APPLICATION INFORMATION
Test Circuits
This application information is advisory, and a performance check is required for actual application circuits.
VCC
Gv = 20log(VOUTdiff/VIN)
47 mF
= 20log(VOUT/VIN) + 6 + 14
0.1 mF
SG
50 Ω
1
VCC
GND1
8
0.1 mF
VIN
50 W
2
IN1
OUT1
7
3
IN2
OUT2
6
0.1 mF
0.1 mF
200 Ω
0.1 mF
VOUTdiff
VOUT
4
AGC
GND2
5
Spectrum
Analyzer
50 Ω
250 W
0.1 mF
Figure 10. Measurement Circuit for Gain and Output Voltage 1
VCC
Gv = 20log(VOUT/VIN) + 14
47 mF
0.1 mF
SG
50 Ω
1
VCC
GND1
8
0.1 mF
0.1 mF
VIN
50 Ω
2
IN1
OUT1
7
3
IN2
OUT2
6
200 Ω
Spectrum
Analyzer
0.1 mF
0.1 mF
VOUT
4
AGC
GND2
5
50 Ω
250 W
0.1 mF
Figure 11. Measurement Circuit for Gain and Output Voltage 2
SG1
VCC
50 Ω
47 mF
0.1 mF
+
SG2
1
VCC
GND1
8
0.1 mF
0.1 mF
50 Ω
2
IN1
OUT1
7
3
IN2
OUT2
6
4
AGC
GND2
5
Spectrum
Analyzer
0.1 mF
0.1 mF
50 Ω
200 Ω
50 Ω
250 Ω
0.1 mF
Figure 12. Measurement Circuit for IM3 and IIP3
6
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