MAIN

WLED[7:0]

EN_4LED

8-Bit IDAC

EN_4LED_PWM

RGB_EN

SUB

WLED[7:0]

EN_2LED

8-Bit IDAC

EN_2LED_PWM

WLED1

WLED2

WLED3

WLED4

WLED5

WLED6

Main

display

LEDs

0 - 25mA

Sub

display

LEDs

0 - 25mA

LP3936

SNVS259D – NOVEMBER 2003 – REVISED MAY 2013

www.ti.com

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

Enable for R switch

GSW

Enable for G switch

BSW

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_X_PWM = 0

→ External PWM control from RGB_EN pin is disabled

EN_GREEN_PWM

EN_X_PWM = 1

→ External PWM control from RGB_EN pin is enabled

EN_BLUE_PWM

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.

WLED and CLED Driver Electrical Characteristics

Symbol

Parameter

Conditions

Min

Typ

Max

Units

Sink Current Range

0–25.5

mA

Maximum Sink Current

24

25.5

27

mA

22

28

mA

Leakage Current

0.04

1

µA

1.0

4

%

4 or WLED5 … 6

(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

Submit Documentation Feedback

Copyright © 2003–2013, Texas Instruments Incorporated

Product Folder Links: LP3936