ChipFind - документация

Электронный компонент: U4476B

Скачать:  PDF   ZIP
U4476B
Preliminary Information
TELEFUNKEN Semiconductors
Rev. A2, 15-Jan-98
1 (7)
IF Amplifier / Converter for DVB (Cable)
Description
The U4476B is a bipolar circuit for the processing of
DVB-Cable IF signals (Digital Video Broadcasting). The
amplifier/ converter is suitable for QAM modulated IF
signals (1st IF) and provides the gain controlled 2nd IF.
With 5 V supply voltage the IC allows application in
RF/IF front ends for DVB-Cable receivers (set top boxes).
Features
D Gain controlled amplifier for the 1st IF (36 MHz)
D IF converter for the 2nd IF (7 MHz);
VCO circuit is controlled by external PLL
D Bandwidth of the output signal: 10 MHz (1 dB)
D Internal AGC with average detection for the QAM
modulated DVB signal, reference level is adjustable
D 5 V supply voltage; low-power consumption
Package: 28-pin small outline plastic package (SO28)
Block Diagram
Tuner
AGC
Band
Gap
Control
AGC:
QAM
VCO
PLL
I
2
C
IF 2
Tuner
V
S
2nd IF
Input
select
12703
5
6
9
10
Ref
(DVB)
7
12
11
24
3
8
21
23
22
20
18
13
15
28
IF 1
Figure 1. Block diagram
U4476B
TELEFUNKEN Semiconductors
Rev. A2, 15-Jan-98
Preliminary Information
2 (7)
Ordering Information
Extended Type Number
Package
Remarks
U4476B-MFLG3
SO28
Taped and reeled, 2000 pcs
Pin Description
1
2
3
4
5
6
7
8
10
9
27
22
21
20
18
19
17
12
11
28
25
26
23
24
V
in1
C
AGC
GND
V
in2
V
in2
Rtop
NC
V
in1
Itun
C
Ref
NC
NC
V
vco
V
vco
GND
LO
out
NC
V
tun
NC
V
S
NC
NC
NC
AGC
Ref
16
15
14
13
14529
V
out
NC
NC
V
sw
Figure 2. Pinning
Pin
Symbol
Function
1, 2
NC
Not connected
3
C
Ref
Capacitor for internal band gap
reference voltage
4
NC
Not connected
5, 6
V
in1
IF input 1 (symmetrical)
7
C
AGC
DVB AGC (time constant)
8
GND
Ground
9, 10
V
in2
IF input 2 (symmetrical)
11
Rtop
Take-over point, tuner AGC
12
Itun
Tuner AGC output current
13
V
out
Output signal (2nd IF)
14
NC
Not connected
15
V
sw
IF input selector switch
16
NC
Not connected
17
NC
Not connected
18
V
tun
Input for the external
VCO tuning voltage
19
NC
Not connected
20
LO
out
Local oscillator output
(reference signal)
21
GND
Ground
22, 23
V
vco
VCO circuit (symmetrical)
24
V
S
Supply voltage
25
NC
Not connected
26
NC
Not connected
27
NC
Not connected
28
AGC
Ref
External reference voltage
(comparator DVB AGC)
Absolute Maximum Ratings
Parameters
Symbol
Value
Unit
Supply voltage
V
S
5.5
V
Supply current
I
S
100
mA
Power dissipation, V
S
= + 5.5 V
P
tot
550
mW
Output currents
I
out
5
mA
Junction temperature
T
j
125
C
Storage temperature
T
stg
25 to +125
C
Electrostatic handling *)
V
ESD
tbd
V
*) Equivalent to discharging a 200-pF capacitor through a 0-
W resistor
U4476B
Preliminary Information
TELEFUNKEN Semiconductors
Rev. A2, 15-Jan-98
3 (7)
Operating Range
Parameters
Symbol
Value
Unit
Supply voltage range
V
S
4.5 to 5.5
V
Ambient temperature
T
amb
0 to +85
C
Thermal Resistance
Parameters
Symbol
Value
Unit
Junction ambient when soldered to PCB
R
thJA
75
K/W
Electrical Characteristics
V
S
= 5 V, T
amb
= 25
C
Parameters
Test Conditions / Pins
Symbol
Min.
Typ.
Max.
Unit
DC supply
Supply voltage
V
S
4.5
5.0
5.5
V
Supply current
I
S
80
100
mA
IF inputs
Input sensitivity, rms value
v
in
80
120
V
rms
Input impedance
See note 1
R
in
1.2
k
W
Input capacitance
See note 1
C
in
2
pF
DVB AGC (QAM modulation)
IF gain control range
IF2 output voltage
Pin 13 = 1.8 V
pp
G
v
60
65
dB
VCO
Oscillator frequency
f
vco
43
60
MHz
Tuning range
f
vco
= 43 MHz
C
vco
= 8.2 pF
Df
tun
1.5
MHz
Local oscillator output signal
f
vco
= 43 MHz
C
vco
= 8.2 pF
LOout
100
mV
Local oscillator control
signal
f
vco
= 43 MHz
C
vco
= 8.2 pF
vtun
0.5
2.7
4.5
V
2nd IF output
Output current source
Output current sink
I
out
2
5
4
mA
Output resistance
See note 1
R
out
100
W
Output amplitude
Peak-to-peak value
v
o,vid
1.6
1.8
2.0
V
DC output voltage
2.2
V
Bandwidth of 2nd IF (1 dB)
R
L
1 k
W, C
L
50 pF
B
10
MHz
Frequency response over
AGC range
DB
2.0
dB
IF input switch
Control voltage
Input 1 is active
Input 2 is active
See also note 2,
`high' (IF1 active, Pin 56)
`low' (IF2 active, Pin 910)
V
SW
V
SW
2.5
3.5
1.5
V
V
Switching current
(Pin 15 to ground)
I
SW
30
mA
U4476B
TELEFUNKEN Semiconductors
Rev. A2, 15-Jan-98
Preliminary Information
4 (7)
Electrical Characteristics
V
s
= 5 V, T
amb
= +25
C
Parameters
Test Conditions / Pins
Symbol
Min.
Typ.
Max.
Unit
Tuner AGC
Available tuner AGC current
I
tun
1
2
4
mA
Allowable output voltage
V
out
0.3
13.5
V
IF slip tuner AGC
Current I
tun
: 10% to 90%
DG
IF
8
10
dB
IF input signal for minimum
take over point
v
in
4
mV
IF input signal for maximum
take over point
v
in
40
mV
Variation of the take over
point by temperature
(Pin 28 open)
DT
amb
= 55
C
IF AGC: G
v
= 46 dB
v
in
2
3
dB
Notes:
1.
This parameter is given as an application information and not tested during production.
2.
Without external control voltage (pin not connected) the input 1 is automatically selected.
Basic Application Circuit
28
1
2
3
4
U4476B
5
6
7
8
9
10
11
12
13
14
27
26
25
24
23
22
21
20
19
18
17
16
15
8.2 pF
10 nF
22
mF
50 k
W
10 nF
DVB
Ref
VCO
Frequency
10 k
W
2.2
mF
IF 1
IF 2
AGC
Tuner AGC
take over
point
Tuner
AGC
2 nd IF
1
U4744B
2
3
4
8
7
6
5
50
W
10 nF
10 nF
IF
10 nF
2.2
mF
+12 V
13900
V
S
VCO
Tuning
Input
Switch
SAW 1
SAW 2
2.2
mF
*)
*)
U4744B:
SAW driver, device phased out, not for new development
current
Figure 3.
U4476B
Preliminary Information
TELEFUNKEN Semiconductors
Rev. A2, 15-Jan-98
5 (7)
IM3 Measurements and Application Recommendations
IM3 Measurement
For correct measurement of IM3 with the 2-carrier
method, it is necessary to control the internal IF amplifier
via an external voltage at Pin 7. The criteria for a correct
value of the external control voltage is the output
amplitude of 1.8 V
pp
(or lower). Please note that
* each
change of the input level requests a correction of the
external gain control voltage at Pin 7 in order to achieve
the 1.8-V
pp
output level again. In this case, IM3 is nearly
43 dB, independent from the input level. With an output
voltage of 1.5 V
pp
only, the IM3 is about 50 dB.
Anyway, if the output amplitude is more than 1.8 V
pp
(specified), the IM3 will decrease rapidly. In the graphic
below, IM3 is shown for two different conditions:
30
32
34
36
38
40
42
44
46
48
50
40
50
60
70
80
90
100
IM3 ( dB )
Input voltage (each carrier) ( dB
mV )
14778
V
out
= 1.5 V
pp
V
out
= 1.8 V
pp
Figure 4. IM3 vs. IF input voltage and IF2out voltage
Test conditions: input: f
1
= 38 MHz,
f
2
= 39 MHz, LO = 43 MHz
Circuitry for External Gain Control
If the gain control of the IC is carried out by an external
DSP, the internal charge pumps of the AGC (Pin 7) have
to be overlapped by an external voltage source. The
internal AGC currents are
20
A. Therefore, the
minimum current capacity of the external voltage source
should be
30
A or more.
The circuitry shown in figure 5 takes some more current.
14581
S852T
10 k
100 nF
to Pin 7
+5 V
from DSP
Figure 5.
External LO Application
If the internal VCO is not used, the LO can be fed
unbalanced or balanced to the VCO Pins 22 and 23. The
application shown below is generating an unbalanced LO
signal by using a 36-MHz third-overtone quartz
reference. The application circuit is taken from IQD
Limited Crystal Product Data Book. The LO signal is fed
unbalanced with 1 nF coupling capacity to Pin 22. Pin 23
has to be blocked to ground with an 1-nF capacitor. The
typical LO amplitude is 100 dB
V. The variation of the
LO input amplitude should not exceed
5 dB (better:
3 dB).
560
100 pF
490 nH
4.7 k
47 pF
68 pF
560
1 nF
S852T
to Pin 22
+5 V
10 k
14582
Figure 6.
Note:
With external LO operation, Pin 18 (VCO tuning voltage)
should be connected to the supply voltage, and Pin 20
(LO output) should not be connected to the PCB.