LP3944ISQEV National Semiconductor, LP3944ISQEV Datasheet - Page 10

• Manufacturer Part Number: LP3944ISQEV
• Description: BOARD EVALUATION LP3944ISQ
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LP3944ISQEV

• Current - Output / Channel: 25mA
• Outputs And Type: 8, Non-Isolated
• Features: Dimmable, I²C Interface
• Voltage - Input: 2.3 ~ 5.5 V
• Utilized Ic / Part: LP3944
• Core Chip: LP3944
• No. Of Outputs: 8
• Output Current: 25mA
• Dimming Control Type: I2C
• Kit Contents: Board, User Guide
• Development Tool Type: Hardware - Eval/Demo Board
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Voltage - Output: -

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Application Notes
PWM1 register determines the duty cycle of DIM1. The LED outputs are LOW (LED on) when the count is less than the value in PWM1 and HIGH (LED off) when
it is greater. If PWM1 is programmed with 0x00, LED output is always HIGH (LED off).
The duty cycle of DIM1 is: PWM1/256
Default value is 50% duty cycle.
BINARY FORMAT FOR SELECTOR REGISTERS — ADDRESS 0x06 to 0x07
Programming Example:
Dim LEDs 0 to 7 at 1 Hz at 25% duty cycle
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 LEDs 0 to 7 to point to DIM0
Step
Bit #
Default value
Bit #
Default value
Bit #
Default value
Set DIM0 = 1s
1 = (PSC0 + 1)/160
PSC0 = 159
Set duty cycle to 25%
Duty Cycle = PWM0/256
PWM0 = 64
Set DIM1 = 0.2s
0.2 = (PSC1 + 1)/160
PSC1 = 31
LEDs 0 to 7
Output = DIM0
B1
0
0
1
1
B1
B1
7
0
7
0
Description
7
1
(Continued)
LED3
LED7
LED States With Respect To Values in "B1" and "B0"
B0
B0
6
0
6
0
6
0
Address 0x05 (PWM1)
Address 0x06 (LS0)
Address 0x07 (LS1)
B1
B1
5
0
5
0
5
0
B0
0
1
0
1
LED2
LED6
10
Register Name
B0
B0
LS0, LS1
4
0
4
0
4
0
PWM0
PSC0
PSC1
B1
B1
3
0
3
0
3
0
LED1
LED5
B0
B0
2
0
2
0
2
0
Output Hi-Z
(LED off)
Output LOW
(LED on)
Output dims
(DIM0 rate)
Output dims
(DIM1 rate)
Function
Set to (Hex)
LS0 = 0xAA
LS1 = 0xAA
0x09F
B1
B1
0x1F
0x40
1
0
1
0
1
0
LED0
LED4
B0
B0
0
0
0
0
0
0