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ROHM Semiconductor |
Video ICs
2-channel PRE / REC amplifier with
auto-tracking interface
BA7181FS
The BA7181FS is a PRE / REC amplifier developed for use in video cassette recorders. It has been designed for use
in two-head decks and features built-in FB damping, two preamplifiers, a chroma output amplifier, an FM output
amplifier (with AGC), an envelope detector, a constant-current BTL-drive REC amplifier (with AGC)and built-in chan-
nel and REC / PB switches on a single monolithic IC.
•Applications
VCRs
•Features
1) The playback amplifier has a total gain of 57dB
(Typ.), and has a low-noise preamplifier. Designed
for VHS-band operation with low external parts
count. The IC has two circuits for two-head VCR
applications.
2) Two playback output systems (through output and
AGC output). The AGC output level is 300mVP-P(Typ.);
suitable for FM brightness signal output.
3) Auto-tracking interface is provided for automated
tracking adjustment. The detector characteristic is
linear, and the sensitivity can be adjusted using
external components.
4) The recording amplifier uses constant-current BLT
drive that handles load variations (i.e. head imped-
ance)well, and gives stable recording characteris-
tics. A single circuit is provided for two-head VCR
use.
5) Built-in recording level AGC means adjustment of
FM recording current is not necessary.
6) Head switches for two-channel PRE / REC system
provided.
7) Operates off a single 5V power supply, with low
power dissipation.
•Absolute maximum ratings (Ta = 25°C)
Parameter
Symbol
Limits
Applied voltage
Power dissipation
VCC 7.0
Pd 937.5∗
Operating temperature
Topr
– 20 ~ + 65
Storage temperature
Tstg – 55 ~ + 150
∗ When mounted on a 90mm × 50mm, t = 1.6mm glass epoxy board.
Reduced by 7.5mW for each increase in Ta of 1°C over 25°C.
Unit
V
mW
°C
°C
•Recommended operating (Ta = 25°C)
Parameter
Symbol
Playback / recording (voltage range)
VCC
᭺Not designed for radiation resistance.
Min.
4.5
Typ.
5.0
Max.
5.5
Unit Conditions
V 11pin
1
Video ICs
•Block diagram
DFF IN
DET FILTER
REC DCFB
PRE IN 1
(REC - OUT 1)
GND 1
PRE IN 2
(REC - OUT 2)
REC + OUT
PB / EE / REC CTRL
REC AGC FILTER
AT ENVE FB
BA7181FS
GND 2
REC LEVEL ADJ
PB AGC OUT
PB AGC FILTER
AT ENVE PEAKING
H SYNC IN
PB RF OUT
AT ENVE OUT
REC IN
VCC
•Electrical characteristics (unless otherwise noted, Ta = 25°C, VCC = 5.0V and f = 4.0MHz)
Parameter
Symbol Min. Typ. Max. Unit
〈Playback system〉 (Fig. 1 measurement circuit, pin 8: “H” )
Quiescent current
Iq (P) — 18 45 mA No signal
Conditions
Measurement
circuit
Fig.1
Voltage gain CH-1
GVP1
54
57
60
dB
Pin 4 input = 0.3mVP-P, pin 1: L,
pin 14 output measurement
Fig.1
Voltage gain CH-2
GVP2
54
57
60
dB
Pin 6 input = 0.3mVP-P, pin 1: H,
pin 14 output measurement
Fig.1
Voltage gain differential ∆GVP — 0 1 dB ∆GVP= | GVP1—GVP2 |
Fig.1
Frequency characteristic ∆GVf – 7 – 3
2nd harmonic distortion∗ 2HDP — – 45
3rd harmonic distortion∗ 3HDP — – 45
0
dB
Difference in pin 14 output level for f = 8.0 / 1.0MHz,
VIN = 0.3mVP-P
— dBc VIN = 0.3mVP-P, 8.0MHz spurious
— dBc VIN = 0.3mVP-P, 12.0MHz spurious
Fig.1
Fig.1
Fig.1
Maximum output level VOMP 1.0 1.5 — VP-P When pin 14 output 2nd harmonic distortion is –30dBc
Fig.1
Crosstalk
CTP — – 38 – 32 dBc Difference in pin 14 output level for pin 1: H / L
Fig.1
∗ Design reference values.
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