between the RLIM pin and GND. The peak inductor current is defined by:

The saturation current specified for the inductor needs to be greater then the peak current to

avoid saturating the inductor, which would result in a loss in efficiency and could damage the

the circuit to deliver up to 180mA for 1.3V input and 400mA for 2.6V input. Other values could

be selected using the above relationships.

6) Using the LBON - Low Battery Output Function

The SP6648 will regulate the output current until the input battery is completely discharged. To

provide an early low battery warning, the Low Battery Output function of the SP6648 switching

connected between VIN, the LBI input pin and GND. When the LBI comparator falling threshold

of 0.61V is reached, D1 switches on, indicating low battery condition. Low battery detect trip

point can be calculated by the following formula:

2

2

1

LOWBAT

R

R

R

61

.

0

V

+

⋅

=

threshold of about 2.0V. Using this relationship, other low battery threshold values can be set

by the user.

7) Brightness Control

One approach to control LED brightness is to apply a PWM signal to the SHDN input of the

SP6648. In this case, the output current will be equal to the product of 350mA and the average

LED. LED current is varied by the potentiometer between almost zero and full 350mA.

POWER SUPPLY DATA

For the standard evaluation board, The efficiency curve is shown in the figure below.

60

65

70

75

80

85

90

95

100

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

Battery Voltage (V)

Fig.3 Efficiency curve of the SP6648LED evaluation board