NCP5007
Output Load Drive
The Schottky diode D1, associated with capacitor C2 (see
Figure 9), provides a rectification and filtering function.
When a pulse−operating mode is required:
• A PWM mode control can be used to adjust the output
current range by means of a resistor and a capacitor
connected across FB pin. On the other hand, the
Schottky diode can be removed and replaced by at least
one LED diode, keeping in mind such LED shall
sustain the large pulsed peak current during the
operation.
In order to take advantage of the built−in Boost
capabilities, one shall operate the NCP5007 in the
continuous output current mode. Such a mode is achieved by
using and external reservoir capacitor (see Table 1) across
the LED.
At this point, the peak current flowing into the LED diodes
shall be within the maximum ratings specified for these
devices. Of course, pulsed operation can be achieved, thanks
to the EN signal pin 3, to force high current into the LED
when necessary.
TYPICAL OPERATING CHARACTERISTICS
100
100
90
4 LED/10 mA
4 LED/4 mA
90
80
80
5 LED/4 mA
70
5 LED/10 mA
70
60
50
40
30
2 LED/10 mA
3 LED/10 mA
3 LED/4 mA
2 LED/4 mA
60
50
40
30
20
10
0
20
10
0
2.50
3.00
3.50
4.00
Vbat (V)
4.50
5.00
5.50
2.50
3.00
3.50
4.00
4.50
5.00
5.50
Vbat (V)
Figure 10. Overall Efficiency vs. Power Supply −
Figure 11. Overall Efficiency vs. Power Supply −
Iout = 4.0 mA, L = 22 mH
Iout = 10 mA, L = 22 mH
100
90
100
90
3 LED/15 mA
3 LED/20 mA
80
80
70
60
50
40
30
20
10
0
70
60
50
40
30
20
10
0
5 LED/20 mA
5 LED/15 mA
2 LED/15 mA
4 LED/15 mA
2 LED/20 mA
4 LED/20 mA
2.50
3.00
3.50
4.00
4.50
5.50
2.50
3.00
3.50
4.00
4.50
5.00
5.50
5.00
Vbat (V)
Vbat (V)
Figure 12. Overall Efficiency vs. Power Supply −
Figure 13. Overall Efficiency vs. Power Supply −
Iout = 15 mA, L = 22 mH
Iout = 20 mA, L = 22 mH
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