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Video ICs
VCR audio signal processing system
BH7775K
The BH7775K is an audio signal processing system IC that includes a peak-noise reduction (PNR) processor, an FM modulator / demodulator circuit, an input / output switcher, an automatic FM detector circuit, an FM band-pass filter, a normal-audio circuit, a regulator circuit, and automatic adjusting circuits (VCO and BPF).
Applications • VHS Video cassette recorders
Features • 1) Operates off dual ± power supply which allows a large reduction in the number of coupling capacitors required. A built-in regulator makes it easy to construct a power supply system. A built-in 2-wire serial control decoder circuit allows serial control of the internal mode settings. Automatic adjusting VCO and BPF circuits that use the color signal subcarrier frequency (NTSC: 3.579545MHz and PAL: 4.433619MHz) ensure stable adjustment that is not effected by stress when the chip is mounted, or variations over time. 4-input switcher (turner, BS, and line 1 and 2). Output switch with built-in STEREO / LEFT / RIGHT switching, Hi-Fi / MIX / NORMAL switching, and BS monitor functions. The PNR processor and FM modulation / demodulation circuit provide reverse characteristics at record-
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2) 3)
7) 8) 9)
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ing and playback. Also, carrier frequency adjustment and FM de-emphasis / playback level adjustment have been combined. Built-in FM band-pass filter connects directly to the playback amplifier and excels at attenuation of the other channel. The FM recording output circuit has a high-performance high-frequency cutoff filter that produces a sine wave output. Switching noise is reduced by a slope-control type differential compensation circuit. Built-in envelope detector circuit and noise-detecting automatic FM detector circuit. Built-in normal-audio signal processing circuit that allows SP / LP / EP equalizer switching. Control terminal provided for use with the BA7755AF high-voltage head switcher.
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Video ICs
BH7775K
•Absolute maximum ratings (Ta = 25°C)
Parameter Symbol VCC
Applied voltage
Limits 23, 55 pin · · · · · · · · · · 6.0 59 pin · · · · · · · · · · · · – 6.0 7, 8, 22 pin · · · · · · · · · 6.5 Pin other than above · · · · 6.0
800∗
Unit V V V V mW °C °C
VEE VIN VIN
Power dissipation Operating temperature Storage temperature
Pd Topr Tstg
– 10 ~ + 70 – 55 ~ + 125
∗ When IC is stand alone, reduced by 8.0mW for each increase in Ta of 1°C over 25°C. When mounted on a
90mm × 50mm, t = 1.6mm glass epoxy board, Pd = 1.3W (reduced by 13.0mW for each increase in Ta of 1°C over 25°C). ᭺Not designed for rediation resistance.
•Recommended operating conditions (Ta = 25°C)
Parameter
Power supply voltage Power supply voltage
Symbol UNREG-VCC UNREG-VEE
Range + 7.0 ~∗ + 7.0 ~∗
Unit V V
∗ The built-in regulator in this IC outputs + 5.0V from pin 55, and - 5.0V from pin 59. The supply voltage range
given above is the voltage to be applied to UNREG VCC and UNREG VEE pins in the measurement circuit to obtain regulator output. Therefore, the upper limit of the voltage range is set by the externally connected transistor that forms the regulator circuit, and not by the IC itself. Note, also, that the lower limit will change depending on the value of the resistor connected between the collector and base of the transistor.
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Video ICs
BH7775K
•Block diagram
NA REC OUT NA HEAD IN
HEAD EQ
48
47
46
45
44
43 EQ
42
41
40 ALC
39
38
37
36
35
34
33
REC EQ NA REC FB MIX ALC MIX OUT LINE OUT R LINE OUT L Vcc ERP GND ERM VEE LINE1 R IN LINE1 L IN LINE2 R IN LINE2 L IN VREFP
49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
NR EMPH R 32
Hi-Fi OUT R
NA PB NFB
NA PB OUT
WTNG1 R
Hi-Fi IN R
NA PB IN
NR TC R
PB EQ
NA ALC
NA FB
GNN
WTNG2 R
RECAMP REC EQ
EQ
PB
DC FB R VCO f0 ADJ R DAC BF OUT R GNMR FM REC OUT AUDIO HEAD SW PULSE IN RHS CTRL FM ALC BPF f0 ADJ VCB MUTE CTRL FM PB IN GNML DAC BF OUT L VCO f0 ADJ L DC FB L
PNR
31 30 29 28 27 26 25
AMP MIX AMP LINE AMP LINE AMP
SW
ATT MODEM
OUTPUT SWITCH Hi-Fi DET
REC D.O. COM.
FM BPF
24 23 22
DATA DECODER
MODEM
ENVE LOPE
21 20 19
INPUT SWITCH PNR
18 17
1 BS R IN
2 BS L IN
3 TUNER R IN
4 TUNER L IN
5 TUNER M IN
6 GNDD
7 DATA
8 CLOCK
9 ENVE OUT / ADJ FLAG / Hi-Fi DET
10 FSC IN
11 Hi-Fi IN L
12 Hi-Fi OUT L
13 NR TC L
14 WTNG1 L
15 WTNG2 L
16 NR EMPH L
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Video ICs
BH7775K
•Pin descriptions
Pin function - 1 / 2 Pin No. 2, 1 4, 3, 5 6 7 8 9 10 11, 38 12, 37 13, 36 14, 35 15, 34 16, 33 17, 32 18, 31 19, 30 20, 29 21 22 23 24 25 26 27 28
Pin name Function BS input (L and R). TUNER input (L, R, and M). Serial control GND. Serial control data input. Serial control clock input. FM input Lch signal component envelope output. Hi-Fi DET output for FM input. ADJ FLAG output for ADJ. fsc input terminal for VCO and BPF adjustment. Hi-Fi input for output switcher. PNR audio output. PNR attack and recovery time setting. Attack R: 530Ω, recovery R: 6.5kΩ. Waiting characteristic low-frequency time co.