ITT - Index of

_ ITT _____
SEMICONDUCTORS
CAMERA INTEGRATED
CIRCUIT
UAA110
C_A_M_E_R_A_,_N_T_EG_R_A_T_E_D_C_,R_C_U_,T
A monolithic integrated cricuit for the control
and monitoring of all functions of an electronic
(single-shot) camera. Fig. 2 shows the circuit
diagram of such a camera using the UAA-
110. In order to avoid over-exposure while
taking brightly-lit scenes and camera movement
in dim light, a mea,surement phase precedes
the automatic setting of the exposure
time. In this phase, the light intensity is measured
as the shutter release is depressed half
way. The indicator-lamps Lu (over-exposure indicator)
and Ls (tripod-indicator) show respectively
whether the aperture must be reduced or
whether a tripod (or a larger aperture) should
be used. For this purpose two voltage comparators
are used which are driven during the
measurement-phase from the photo-resistor RF •
In addition, the state of the battery can be
checked by blocking, (with the finger, for example)
the light to the photoresistor. If the
lamp Ls does not light, the batter is exhausted.
If the shutter-release is fully depressed, the
photoresistor is connected to the integrated
capacitor at input of the threshold amplifier. At
the same time, the shutter is opened and held
open with a latch during the exposure. The exposure
time is determined by the charging of
the capacitor CF through the photoresistor
whose resistance is dependent of the illumination.
When the voltage on the capacitor
reaches the threshold voltage of the amplifier
(determined by the voltage divider Ry, Rx) the
electromagnet M is activated and the shutter
latch is released, permitting the shutter to be
closed by means of a spring.
RECOMMENDED OPERATING CONDITIONS
(see the circuit of fig. 3)
V" Supply voltage .......... 3,5 to 6V
Potential divider ratio .... 0,55 to 0,8
Photoresistor ........ 100 to 2x10 n T
Riso! Insulation resistance ...... >250MO
TA Ambient temperature
range ........... -18 to +50°C
I
I
--7,62----1
Fig. 1-Package
QS5it--+----,t-i:.....
O.4t--+--+---t
+ CM
~4---6-+--------4-~O
Fig. 2~Block diagram of camera
8-89