ROUT

GOUT

BOUT

First cycle

Next cycles

ON

OFF

ON<OFF

OFF<ON

ON

OFF

ON=OFF=0

ON

OFF

OFF

ON

LP3936

www.ti.com

SNVS259D – NOVEMBER 2003 – REVISED MAY 2013

Figure 25. Example Blinking Waveforms

RGB Driver Electrical Characteristics

Symbol

Parameter

Conditions

Min

Typ

Max

Units

ON Resistance

2

4.5

Ω

Off State Leakage Current

0.04

1

µA

Maximum Sink Current

120

mA

Maximum Slope Period

Maximum Duty Setting

0.93

s

Minimum Slope Period

Maximum Duty Setting

31

ms

Slope Resolution

Maximum Duty Setting

62

ms

Start/Stop Resolution

Cycle 1s

1/16

s

Duty

Duty Step Size

1/16

Blinking Cycle Accuracy

−6

±3

+6

%

Duty Cycle Range

EN_FLASH = 1

0

94

%

Duty Cycle Range

EN_FLASH = 0

0

31

%

Duty Resolution

EN_FLASH = 1 (4-bit)

6.27

%

Duty Resolution

EN_FLASH = 0 (4-bit)

2.09

%

PWM Frequency

EN_FLASH = 1

20

kHz

PWM Frequency

EN_FLASH = 0

6.67

kHz

(1)

The total load current of the boost converter should be limited to 250 mA.

RDUTY[3:0]

DUTY sets the brightness of the LED by adjusting the duty cycle of the PWM driver. The minimum DUTY cycle [0000]

GDUTY[3:0]

is 0% and the maximum [1111] in the Flash mode is 94% and in the normal mode 31% of the peak pulse current. The

BDUTY[3:0]

peak pulse current is determined by the external resistor, LED forward voltage drop and the boost voltage.

RSLOPE[3:0]

SLOPE sets the turn-on and turn-off slopes. Fastest slope is set by [0000] and slowest by [1111]. SLOPE changes the

GSLOPE[3:0]

duty cycle at constant, programmable rate. For each slope setting the maximum slope time appears at maximum

BSLOPE[3:0]

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 [1000] the sloping time

is 17 ms [0000] to 496 ms [1111]. The blinking cycle has no effect on SLOPE.

RON[6:0]

ON sets the beginning time of the turn-on slope. The on-time is relative to the selected blinking cycle length. On-

GON[6:0]

setting N (N = 0–127) sets the on-time to N/128 * cycle length.

BON[6:0]

ROFF[6:0]

OFF sets the beginning time of the turn-off slope. Off-time is relative to blinking cycle length in the same way as on-

GOFF[6:0]

time.

BOFF[6:0]

If ON = 0, OFF = 0 and RGB_PWM = 1, then RGB outputs are continuously on (no blinking), DUTY controls the

brightness and SLOPE is ignored.

If ON and OFF are the same, but not 0, RGB outputs are turned off.

(2)

TI's AN-1293 Driving RGB LEDs Using LP3936 Lighting Management System Application Report (SNVA071) contains a thorough

description of the RGB driver functionality including programming examples.

Copyright © 2003–2013, Texas Instruments Incorporated

Submit Documentation Feedback

19

Product Folder Links: LP3936