NCP5080 데이터 시트보기 (PDF) - ON Semiconductor
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NCP5080 Datasheet PDF : 12 Pages
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NCP5080
Table 4. FLASH OPERATING TRUE TABLE
EN TRGFL
PHREF
PHSEN
Status
0
X
X
X
System Disabled: The boost and the flash are de-activated. Any on going flash
is immediately switched OFF.
1
0
0.5 V to
1.5 V
GND
System Active: The output reservoir is being charged and the output voltage
regulated. The photo sense is deactivated. The IGBT gate drive is LOW.
1
1
0.5 V to
1.5 V
GND
System Active: The output reservoir is being charged and the output voltage
regulated. The photo sense is deactivated. The IGBT gate drive is HIGH
whatever be the Vout voltage value . The xenon tube is fired if Vout = Vxen minim‐
um and the flash light keeps going until either TRGFL = 0, or the reservoir
capacitor is fully discharged.
1
0
VREF
PHOTODIODE
System Active: The output reservoir is being charged and the output voltage
regulated. The photo sense is activated . The IGBT gate drive is LOW.
1
1
VREF
PHOTODIODE
System Active: The output reservoir is being charged and the output voltage
regulated. The photo sense is deactivated and the flash is switched OFF if the
voltage present at the PHSEN Pin is higher the reference voltage applied to the
PHREF Pin. The IGBT gate drive is HIGH whatever be the Vout voltage value .
The Xenon tube is fired if Vout = Vxen minimum and the IGBT keeps going until
either TRGFL = 0, or the PHSEN > PHREF, or the reservoir capacitor is fully
discharged.
The TRGFL signal provides a simple way to generate
multiple consecutive flashes (similar to the stroboscope
effect) to minimize the red eye effect, or to freeze multiple
pictures of moving objects. The IGBT must be capable to
turn ON with limited Gate voltage.
Photodiode Sensor
The photodiode sensor provides a feedback from the
illumination generated by the xenon flash to avoid the
overexposed picture. The PHREF pin shall be biased
according to the model of xenon tube (in particular, the
energy level) and optical lens aperture.
The function can be deactivated when not used in the
application shown in Table 5. More over, connecting the
PHREF Pin to the IPKREF Pin provides an easy way to fully
disconnect the photo sense function.
The external photo sense element shall be connected
across PHSEN and VBAT to source the current as the
illumination increases, with a pull-down resistor connected
to the ground reference as depicted in Figure 4. The sense
resistor is calculated to get the collector current when the
photo diode is saturated. With a typical 10 mA to 30 mA of
photodiode current, the resistor will be 100 kW to cope with
the low input battery supply voltage situation.
Table 5. NCP5080 PHOTO SENSE TRUE TABLE
Pin
Operation
0.5 V v PHREF w 1.5 V
PHSEN = GND
Photodiode Sense Deactivated
PHREF = VPH
PHSEN = Photodiode
Photodiode Sense Activated
Operation
The IGBT is solely controlled by the TRGFL Pin
The IGBT is controlled by the [TRGFL AND PHSEN ] status.
VBAT
4 VBAT
D2
PHOTO
VBAT
-
12 PHSEN
U1
+
GND
1
PHREF
GND
R1
100k
R2
100k
-
U2
+
Comparator
Figure 4. Basic Photo Sense Input Circuit
PHSTP
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