Programming Example:

Dim LEDs 0 to 7 at 1 Hz at 25% duty cycle

Dim LEDs 8 to 12 at 5 Hz at 50% duty cycle

Set LEDs 13, 14 and 15 off

Step 1: Set PSC0 to achieve DIM0 of 1s

Step 2: Set PWM0 duty cycle to 25%

Step 3: Set PSC1 to achieve DIM1 of 0.2s

Step 4: Set PWM1 duty cycle to 50%

Step 5: Set LEDs 13, 14 and 15 off by loading the data into LS3 register

Step 6: Set LEDs 0 to 7 to point to DIM0

Step 7: Set LEDs 8 to 12 to point to DIM1

Step

Description

Register Name

Set to (Hex)

1

Set DIM0 = 1s

1 = (PSC0 + 1)/160

PSC0 = 159

PSC0

0x09F

2

Set duty cycle to 25%

Duty Cycle = PWM0/256

PWM0 = 64

PWM0

0x40

3

Set DIM1 = 0.2s

0.2 = (PSC1 + 1)/160

PSC1 = 31

PSC1

0x1F

4

Set duty cycle to 50%

Duty Cycle = PWM1/256

PWM1 = 128

PWM1

0x80

5

LEDs 13, 14 and 15 off

Output = HIGH

LS3

0x03

6

LEDs0to7

Output = DIM0

LS0, LS1

LS0 = 0xAA

LS1 = 0xAA

7

LEDs8to12

Output = DIM1

LS2, LS3

LS2 = 0xFF

LS3 = 0x03

REDUCING I

In many applications, the LEDs and the LP3943 share the

same V

When the LEDs are off, the LED pins are at a lower potential

than V

∆I

this current, consider keeping the LED pins at a voltage

equal to or greater than V

20079614

FIGURE 9. Methods to Reduce I

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