LP3943ISQ National Semiconductor, LP3943ISQ Datasheet - Page 11

• Manufacturer Part Number: LP3943ISQ
• Description: LED Driver IC
• Manufacturer: National Semiconductor

Specifications of LP3943ISQ

• Driver Case Style: LLP
• Peak Reflow Compatible (260 C): No
• Leaded Process Compatible: No
• No. Of Pins: 24
• Package / Case: 24-LLP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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Application Notes
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
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
Step
DD
, as shown in Section Typical Application Circuit.
Q
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
Set duty cycle to 50%
Duty Cycle = PWM1/256
PWM1 = 128
LEDs 13, 14 and 15 off
Output = HIGH
LEDs 0 to 7
Output = DIM0
LEDs 8 to 12
Output = DIM1
WHEN LEDS ARE OFF
Description
(Continued)
FIGURE 9. Methods to Reduce I
11
Register Name
than V
this current, consider keeping the LED pins at a voltage
equal to or greater than V
LS0, LS1
LS2, LS3
PWM0
PWM1
Q
PSC0
PSC1
LS3
When LEDs Are Off
DD
, causing extra supply current (∆I
DD
.
Set to (Hex)
LS0 = 0xAA
LS1 = 0xAA
LS2 = 0xFF
LS3 = 0x03
20079614
0x09F
0x40
0x1F
0x80
0x03
Q
). To minimize
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