參數(shù)資料
型號: LB8652T
廠商: Sanyo Electric Co.,Ltd.
英文描述: Monolithic Digital IC Driver for Digital Still Cameras
中文描述: 單片數(shù)字集成電路驅動數(shù)碼相機
文件頁數(shù): 7/8頁
文件大?。?/td> 101K
代理商: LB8652T
LB8652T
No.7896-7/8
Points to Take into Consideration When Designing
(1) For shutter control Constant current setting (RFG, OUT1, OUT2)
The constant current when flowing the current from OUT2 to OUT1 can be specified by a resistor connected
between RFG and GND. The reference voltage is generated in the IC and it is approximately 0.21V. The voltage
is controlled in such a way so that the voltage generated at the resistor used for current detection connected
between RFG and GND would be equal to this voltage.
The formula for calculating the output current is as given below. In addition, as a fundamental setting, it is
designed so that the approx. 200mA would flow through the coil when RFG resistor is connected with 1
.
(Current flows from OUT2 to OUT1)
= 0.21V
÷
(Resistance between RFG and GND+0.05
) - (Drive current of output Tr)
This 0.05
is for a common impedance of the output Tr emitter which drives constant current in the RFG pin and
the sensing wiring for the constant current control amplifier.
Also, the drive current of output Tr is equal to 1/hfe (a 80th to 200th part approx.) of the coil current.
The constant current flowed from OUT2 to OUT1 is more accurate than that flowed from OUT1 to OUT2.
Therefore make sure to use this method for shutter closing drive.
(2) For shutter control Open-loop constant current control setting (ILM, OUT1, OUT2)
In order to prevent the high-current flowing when shutter opening, the output current control circuit is
implemented for current flowing from OUT1 to OUT2. The constant current when flowing the current from
OUT1 to OUT2 can be specified by a resistor connected between ILM and GND.
The formula for calculating the output current is as given below.
(Current flows from OUT1 to OUT2) = 1.36V
÷
(Resistance between ILM and GND)
×
200 approx.
Due to open-loop control by which feedback signals are not sent, the accuracy of constant current is relatively
inferior. It is used for shutter opening drive.
(3) Phase compensation capacitor (FC)
See and check the capacitor value for FC pin between 0.0015 to 0.033
μ
F. Choose a capacitance value which does
not cause oscillation problems for output. In particular, when a coil with large inductance is used, it is necessary
to choose a sufficiently large capacitance.
(4) Constant voltage control Oscillation-stopping capacitor (OUT4, OUT8)
When controlling the constant voltages, it is necessary to place capacitors between the OUT pins to stop
oscillation. See and check the capacitance value between 0.01
μ
F to 0.1
μ
F. Choose a capacitance value which
does not cause oscillation problems for output.
When driving at saturation, there is no need for such oscillation-stopping capacitors.
(5) GND wiring and power line capacitors : (GND
×
2, VCC, VB)
Connect GND (2 places) near the IC, and place the capacitors as close as possible to each of the power pins.
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