Peak current definition

The peak current rating is a design parameter whose

value is dependent upon the overall application. For

the high brightness reference designs, a peak current

of 190mA was chosen to ensure that the converter

could provide the required output power to the LED.

the switching transistor, Q1, is in full saturation with

maximum output power conditions, assuming

worse-case input voltage and transistor gain under all

operating temperature extremes.

determined by:

A selection guide of sense resistor and inductor values

for given input voltages, output currents and number

of LED connected in series is provided in the table

below.

SEMICO NDUC TORS

ZXSC310

ISSUE 3 - SEPTEMBER 2007

10

R

V

I

SENSE

ISENSE

PK

=

Input Voltage

(V)

LED current

(mA)

No. of LED’s

R

SENSE

(m )

Inductor

( H)

Efficiency

(%)

3.3V

10

3

510

68

80

3.3V

10

4

330

68

81

3.3V

10

6

150

68

79

3.3V

20

3

220

68

84

3.3V

20

4

150

68

93

3.3V

20

6

77

68

79

3.3V

30

3

170

68

84

3.3V

30

4

100

68

84

3.3V

30

6

47

68

77

5V

10

3

750

68

83

5V

10

4

510

68

84

5V

10

6

330

68

79

5V

20

3

440

68

85

5V

20

4

250

68

85

5V

20

6

150

68

82

5V

30

3

330

68

86

5V

30

4

170

68

85

5V

30

6

100

68

83