NCP5007

http://onsemi.com

5

temperature, unless otherwise noted.)

Rating

Pin

Symbol

Min

Typ

Max

Unit

High Level Input Voltage

Low Level Input Voltage

1

EN

1.3

−

−

−

−

0.4

V

EN Pull Down Resistor

1

−

100

−

k

W

Feedback Voltage Threshold

4

FB

170

200

230

mV

Output Current Stabilizes @ 5% time delay following a

5

−

100

−

ms

5

−

1.7

−

W

5. The overall tolerance depends upon the accuracy of the external resistor.

THEORY OF OPERATION

The DC−DC converter is designed to supply a constant

current to the external load, the circuit being powered from

a standard battery supply. Since the regulation is made by

means of a current loop, the output voltage will vary

depending upon the dynamic impedance presented by the

load.

Considering a high intensity LED, the output voltage can

range from a low of 6.4 V (two LED in series biased with a

low current), up to 22 V, the maximum the chip can sustain

continuously. The basic DC−DC structure is depicted in

Figure 3.

With a 22 V operating voltage capability, the power

device Q1 can accommodate a high voltage source without

any leakage current degradation.

POR

LOGIC

CONTROL

TIME_OUT

ZERO_CROSSING

RESET

GND

Vdsense

Q1

Vds

L1

22

mH

D1

GND

Vs

R2

xR

GND

R1

C2

+

−

GND

Vref

V(Ipeak)

+

−

Vdsense

Figure 3. Basic DC−DC Converter Structure

4

1