TLC5944 Datasheet, PDF (24/34 Pages) Texas Instruments – 16-Channel, 12-Bit PWM LED Driver with 6-Bit Dot Correction and Pre-Charge FET

TLC5944
SBVS112 – JUNE 2008 ...................................................................................................................................................................................................... www.ti.com
VLED
(Power-Supply for LED)
SW
PMOS1
LED1-1
LED1-2
SW
NMOS1
LED1-0
VLED
C0
C1
SW
PMOS0
I_CHRG
Line 1
¼
Parasitic Capacitor
C2
Line 0
SW
NMOS0
LED0-0
LED0-1
LED0-2
OUT0
OUT1
¼
OUT2
Ordinal
LED Driver
OUT0
OUT1
OUT2
ON
ON
ON
¼
Constant Current
I_OUT = 50 mA
SW ^ON
PMOS0 _OFF
SW ^ON
NMOS0 _OFF
SW ^ON
PMOS1 _OFF
SW ^ON
NMOS1 _OFF
High
BLANK
Low
ON
OUT0
OFF
OUT0
VLED
Voltage
VLED - V_F
LED0-0
Current
LED1-0
Current
50 mA
0 mA
50 mA
0 mA
Line 0 is VLED level.
Line 0 is GND level.
Line 1 is VLED level.
Line 1 is GND level.
V_CHG
GND
(1) (2)
OUT0 voltage is pulled down to GND side
by the coupling with LED lamp capacitor
between Line 0 and OUT0.
(3)
(4)
Ghost phenomenon is observed
when Line 1 goes up to VLED.
Figure 33. LED Ghost-Lighting Phenomenon Mechanism
VLED
(Power-Supply for LED)
SW
PMOS1
LED1-1
LED1-2
SW
NMOS1
VLED
LED1-0
SW
PMOS0
C0
C1
Disappearing I_CHRG
Line 1
¼
Parasitic Capacitor
C2
Line 0
SW
NMOS0
VUP
LED0-0
LED0-1
LED0-2
OUT0
OUT1
¼
OUT2
Pre-Charge MOS
BLANK
Timing
Control
OUT0
ON
TLC5944
LED Driver
Constant Current
I_OUT = 50 mA
OUT0
ON
OUT0
ON
PCHGON
¼
SW
PMOS0
SW
NMOS0
SW
PMOS1
SW
NMOS1
BLANK
OUT0
PCHGON
Signal
ON
OFF
ON
OFF
ON
OFF
ON
OFF
High
Low
ON
OFF
ON
OFF
OUT0
VLED
Voltage
VLED - V_F
LED0-0
Current
LED1-0
Current
50 mA
0 mA
50 mA
0 mA
Line 0 is VLED level.
Line 0 is GND level.
Line 1 is VLED level.
Line 1 is GND level.
V_CHG
GND
(1) (2)
(3)
(4)
Ghost phenomenon not seen
Figure 34. LED Ghost-Lighting Mechanism by Pre-Charge FET
24
Submit Documentation Feedback
Product Folder Link(s): TLC5944
Copyright © 2008, Texas Instruments Incorporated