LA7265W(1998) Ver la hoja de datos (PDF) - SANYO -> Panasonic

Número de pieza

componentes Descripción

Fabricante

LA7265W
(Rev.:1998)

Single-Chip Black and White CCD Camera Signal Processing IC

SANYO -> Panasonic 

Continued from preceding page.

Pin No. Symbol

I/O

LA7265W

Equivalent circuit

Unit (resistance: Ω), I: input, O: output, B: I/O, P: power supply

Function

12

VREF

O

1.8 V reference voltage. This pin outputs the OPB clamping

reference voltage used by pins 14, 23, 24 and 29. Insert a capacitor

between this pin and ground to stabilize this voltage.

13

Y1. OUT

O

14

Y1. IN

I

15

GAMMA

I

Output for the signal amplified by the AGC circuit.

The signal that passed through the AGC amplifier is input to this pin

through a low-pass filter and a coupling capacitor. OPB clamping is

applied at the input stage. This clamping is applied with the timing of

the clamping pulse input to pin 41. The clamping level is about 1.8 V,

and when the OPB level is 1.8 V signals and noise with a level of

under about 0.5 V must not be input. If signals or noise at such levels

occur, or if pedestal displacement occurs at pin 23, (both of these

condition occur when the AGC maximum gain is at its maximum

level) first low clip the signal by inserting an NPN emitter follower at

pin 13, and then insert a low-pass filter. Use a low-pass filter with an

input impedance ratio of 1:10.

Gamma circuit selection and gamma variation control. The signal

OPB clamped at pin 14 is divided into two paths. The first path goes

to the gamma correction system. First, this signal is blanked with the

timing of the pre-blanking pulse input to pin 39 and pedestal is added

by a built-in DC source with a level essentially identical to the OPB

level. At that time, low clipping is applied at a level about 300 mV or

more below the OPB level. Next, the signal passes through the γ

correction circuit. However, there are three γ-correction circuits, one

with γ = 0.45, one with γ = 1, and one with a variable γ. The gamma

correction circuit is selected by this pin.

Pin 15 = 0 V: ........................The γ = 0.45 circuit is used.

Pin 15 = 1 to 4 V: .................The variable γ circuit is used.

(When pin 15 is open:..........The variable γ circuit at γ = 0.6 is used.)

Pin 15 = 5 V: ........................The γ = 1 circuit is used.

To select the maximum γ for the variable γ circuit, set the pin 15

voltage to 4 V. See the description of pin 35 for the second signal

path

Continued on next page.

No. 4850-12/24

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