LM3553SD-HALF National Semiconductor, LM3553SD-HALF Datasheet - Page 11

• Manufacturer Part Number: LM3553SD-HALF
• Description: 1.2A Dual Flash LED Driver System with I2C Compatible
• Manufacturer: National Semiconductor

Torch Current Control Register
TC6-TC0: Sets Torch current level for D1 and D2. xxx1 1111
= Fullscale
Flash Current Control Register
FC6-FC0: Sets Flash current level for D1 and D2. x111 1111
= Fullscale
Current Level Equation
The Full-Scale Flash Current Level is set through the use of
an external resistor (R
R
each of the two current sinks, D1 and D2.
R
The current through each current sink, D1 and D2, can be
approximated by the following equation using the values
stored in either the Torch or Flash Current Control registers.
I
where N is the decimal equivalent number (0
Flash and 0
Current control registers and I
scale. Brightness codes 0 through 4 are repeated and each
sets the total LED current to approximately 40mA.
Flash Safety Timer Control Register
FD3-FD0: Sets Flash Duration for D1 and D2. 1111 =
Fullscale
FLASH
SET
SET
selection equation can be used to set the current through
= 6770 × 1.24V ÷ I
≊
(N + 1) × I
≤
N
≤
I
Flash
LED_TOTAL
R
31 for Torch) stored in the Torch or Flash
500mA
600mA
SET
1.2A
ID2
1A
= ID1 +
SET
FIGURE 10.
Dx
FIGURE 8.
FIGURE 9.
Selection Table
) connected to the I
÷ 128
LED_TOTAL
33.6kΩ
16.8kΩ
28kΩ
14kΩ
R
SET
= I
D1
≤
+ I
SET
N
D2
≤
pin. The
20171406
20171407
20171408
@ Full-
127 for
11
EN1
Safety Timer Duration
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Code (Binary)
LM3553 Functionality Truth Table
EN0
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
FEN Terminated Pulse
F
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
EN
T
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
X
Typical Safety Timer
(milliseconds)
Duration
1000
1100
1200
1300
1400
3200
100
200
300
400
500
600
700
800
900
Shutdown
Shutdown
50
Indicator
Indicator
Result
Flash
Torch
Flash
Torch
Torch
Torch
Flash
Torch
Flash
Torch
Flash
Torch
www.national.com
20171426