LP3936 Datasheet, PDF (20/30 Pages) National Semiconductor (TI) – Lighting Management System for Six White LEDs and One RGB or FLASH LED

LP3936
SNVS259D – NOVEMBER 2003 – REVISED MAY 2013
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CYCLE[1:0]
CYCLE sets the blinking cycle: [00] for 0.25s, [01] for 0.5s, [10] for 1s and [11] for 2s. CYCLE setting is common to all
R, G and B drivers.
RSW
GSW
BSW
Enable for R switch
Enable for G switch
Enable for B switch
RGB_START
Master Switch:
RGB_START = 0 → RGB OFF
RGB_START = 1 → RGB ON, starts the new cycle from t = 0
RGB_PWM
RGB_PWM = 0 → RSW, GWS and BSW control directly the RGB outputs (on/off control only)
RGB_PWM = 1 → Normal PWM RGB functionality (duty, slope, on/off times, cycle)
EN_FLASH
Flash Mode enable control for RGB. In Flash mode (EN_FLASH = 1) RGB outputs are PWM controlled
simultaneously, not in 3-phase system as in the Normal Mode.
EN_RED_PWM
EN_GREEN_PWM
EN_BLUE_PWM
EN_X_PWM = 0 → External PWM control from RGB_EN pin is disabled
EN_X_PWM = 1 → External PWM control from RGB_EN pin is enabled
Internal PWM control (DUTY) can be used independently of external PWM control. External PWM has the same effect
on all enabled colors.
WLED Drivers
White LED drivers drive each white LED with a regulated constant current. The outputs are combined in two
groups, four outputs for the main display backlight and two outputs for the sub display backlight. The current is
controlled between 0 and 25.5 mA using the 8-bit current mode DA-converters. WLED outputs can be used to
drive any kind of LED.
Main and sub display outputs have separate enable control bits, EN_4LED and EN_2LED.
PWM control of WLED outputs for dimming or on/off control is possible using RGB_EN pin together with
EN_4LED_PWM and EN_2LED_PWM enable control bits from the user register. Recommended maximum
frequency of WLED external PWM control is 1 kHz.
RGB_EN
EN_4LED_PWM
MAIN
WLED[7:0]
8-Bit IDAC
EN_4LED
EN_2LED_PWM
SUB
WLED[7:0]
8-Bit IDAC
EN_2LED
WLED1
WLED2
WLED3
WLED4
WLED5
WLED6
Main
display
LEDs
0 - 25mA
Sub
display
LEDs
0 - 25mA
WLED and CLED Driver Electrical Characteristics
Symbol
I_RANGE
I_MAX
I_LEAKAGE
I_MATCH
Parameter
Sink Current Range
Maximum Sink Current
Leakage Current
Sink Current Matching ⁽²⁾
Conditions
Min
V_FB = 4.55V, Control 00h–FFh
See ⁽¹⁾
24
22
V_FB = 5V
I_SINK = 13 mA, between WLED1 …
4 or WLED5 … 6
Typ
0–25.5
25.5
0.04
1.0
Max Units
mA
27
mA
28
mA
1
µA
4
%
(1) A minimum voltage, Dropout Voltage, is required on the WLED outputs for maintaining the LED current. The current reduction at lower
voltages is shown by the graph in Figure 26.
(2) Match % = 100% * (Max – Min)/Min
20
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