LP3931 Datasheet, PDF (13/17 Pages) National Semiconductor (TI) – Dual RGB LED Driver with High Current Boost DC-DC Converter

RGB Driver Electrical Characteristics
(R1, G1, B1, R2, G2, B2 outputs)
Symbol
Parameter
Conditions
R_DS-ON
I_LEAKAGE
I_MAX
T_SMAX
T_SMIN
T_SRES
T_START/STOP
Duty
ON Resistance
Off State Leakage Current
Maximum Sink Current
Maximum Slope Period
Minimum Slope Period
Slope Resolution
Start/Stop Resolution
Duty Step Size
V_FB = 5V, LED driver off
(Note 5)
At Maximum Duty Setting
At Maximum Duty Setting
At Maximum Duty Setting
Cycle 1s
T_BLINK
D_CYCF
D_CYC
D_RESF
D_RES
F_PWMF
F_PWM
Blinking Cycle Accuracy
Duty Cycle Range
Duty Cycle Range
Duty Resolution
Duty Resolution
PWM Frequency
PWM Frequency
EN_FLASH = 1
EN_FLASH = 0
EN_FLASH = 1 (4-bit)
EN_FLASH = 0 (4-bit)
EN_FLASH = 1
EN_FLASH = 0
Min
Typ
Max
Units
3.5
6
Ω
0.03
1
µA
120
mA
0.93
s
31
ms
62
ms
1/16
s
1/16
−6
±3
+6
%
0
99.6
%
0
33.2
%
6.64
%
2.21
%
20
kHz
6.67
kHz
RGB LED PWM Control (Note 14)
R1DUTY[3:0]
G1DUTY[3:0]
B1DUTY[3:0]
R2DUTY[3:0]
G2DUTY[3:0]
B2DUTY[3:0]
R1SLOPE[3:0]
G1SLOPE[3:0]
B1SLOPE[3:0]
R2SLOPE[3:0]
G2SLOPE[3:0]
B2SLOPE[3:0]
R1ON[3:0]
G1ON[3:0]
B1ON[3:0]
R2ON[3:0]
G2ON[3:0]
B2ON[3:0]
R1OFF[3:0]
G1OFF[3:0]
B1OFF[3:0]
R2OFF[3:0]
G2OFF[3:0]
B2OFF[3:0]
CYCLE[1:0]
DUTY sets the brightness of the LED by adjusting the duty cycle of the PWM driver. The minimum DUTY
cycle is 0% [0000] and the maximum in the Flash mode is ∼ 100% [1111] of peak pulse current. The
peak pulse current is determined by the external resistor, LED forward voltage drop and the boost
voltage. In normal mode the maximum duty cycle is 33%.
SLOPE sets the turn-on and turn-off slopes. Fastest slope is set by [0000] and slowest by [1111]. SLOPE
changes the duty cycle at constant, programmable rate. For each slope setting the maximum slope time
appears at maximum DUTY setting. When DUTY is reduced, the slope time decreases proportionally. For
example, in case of maximum DUTY, the sloping time can be adjusted from 31 ms [0000] to 930 ms
[1111]. For 50% DUTY [0111] the sloping time is 14 ms [0000] to 434 ms [1111]. The blinking cycle has
no effect on SLOPE.
ON sets the beginning time of the turn-on slope. The on-time is relative to the selected blinking cycle
length. On-setting N (N = 0 – 15) sets the on-time to N/16 * cycle length.
OFF sets the beginning time of the turn-off slope. Off-time is relative to the blinking cycle length in the
same way as the on-time.
If ON = 0, OFF = 0 and RGB_PWM = 1, then the RGB outputs are continuously on (no blinking), the
DUTY setting controls the brightness and the SLOPE control is ignored.
If ON and OFF are the same, but not 0, the RGB outputs are turned off.
CYCLE sets the blinking cycle: [00] for 0.25s, [01] for 0.5s, [10] for 1s and [11] for 2s. CYCLE effects to
all RGB LEDs.
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