LP3944ISQEV National Semiconductor, LP3944ISQEV Datasheet - Page 9

• 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: -

Application Notes
Note: Registers 1, 8 and 9 are empty and non-functional registers. Register 1 is read-only, with all bits hard-wired to zero. Registers 8 and 9 can be written and read,
but the content does ot have any effect on the operation of the LP3944.
BINARY FOMAT FOR INPUT REGISTERS (READ ONLY) — ADDRESS 0x00 and 0x01
X = don’t care
BINARY FORMAT FOR FREQUENCY PRESCALER AND PWM REGISTERS — ADDRESS 0x02 to 0x05
PSC0 register is used to program the period of DIM0.
DIM0 = (PSC0+1)/160
The maximum period is 1.6s when PSC0 = 255.
PWM0 register determines the duty cycle of DIM0. The LED outputs are LOW (LED on) when the count is less than the value in PWM0 and HIGH (LED off) when
it is greater. If PWM0 is programmed with 0x00, LED output is always HIGH (LED off).
The duty cycle of DIM0 is: PWM0/256
Default value is 50% duty cycle.
PSC1 register is used to program the period of DIM1.
DIM1 = (PSC1 + 1)/160
The maximum period is 1.6s when PSC1 = 255.
Address (Hex)
Bit #
Default value
Bit #
Default value
Bit #
Default value
Bit #
Default value
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
Input 1
Register 1
PSC0
PWM0
PSC1
PWM1
LS0
LS1
Register 8
Register 9
LED7
X
7
Register Name
7
0
7
1
7
0
(Continued)
LED6
6
X
6
0
6
0
6
0
TABLE 1. LP3944 REGISTER TABLE
Read Only
Read Only
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
LED5
Address 0x03 (PWM0)
Address 0x02 (PSC0)
Address 0x04 (PSC1)
X
5
Address 0x00
5
0
5
0
5
0
Read/Write
9
LED4
X
4
4
0
4
0
4
0
LED3
LED0–7 Input Register
None
Frequency Prescaler 0
PWM Register 0
Frequency Prescaler 1
PWM Register 1
LED0–3 Selector
LED4–7 Selector
None
None
X
3
3
0
3
0
3
0
LED2
X
2
2
0
2
0
2
0
Register Function
LED1
1
X
1
0
1
0
1
0
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LED0
X
0
0
0
0
0
0
0