LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
LD1074
LD1074
16-Channel Constant Current LED Driver
With 16-bit PWM Control and Dot-Correction
Ver. 1.1 / Jul. 2013
This document is a general product description and is subject to change without notice.
LDT Inc. does NOT assume any responsibility for use of circuits described.
1
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Description
LD1074 is a 16-channel constant current LED driver with selectable 16-/12-bit gray scale control and 8-bit pixel
correction. LD1074 provides constant current ranging from 2mA to 60mA for each output channel. The output
current can be set by an external resistor. LD1074 adopts open/short error detection, thermal detection, and external
resistor connection and adjusts current gain control for brightness.
Features
16 constant-current output channels
Constant output current range per channel: 2~60mA ( 2~60mA @ 5V, 2~45mA @ 3.3V )
Excellent output current accuracy,
- Between channels: <±1.0% (typ.);
- Between ICs: <±1.5% (typ.)
Visual effect control
- Increased refresh rate
- selectable gray scale (16bit or 12bit)
- Individual pixel-correction (256 steps : 8-bit control)
- Brightness control (7-bit linear programmable output current gain)
Error detection control
- Individual LED Open/Short-circuit detection
- External Resistor Detection (R-EXT pin Open Detection)
- Thermal protection ( Alarm & Shut-Down)
EMI reduction
- Delay between output channels.
- Fast / Slow output switching Speed
Maximum gray scale clock frequency: 33MHz
Application
Full-color LED display
VMS (Variable Message Sign)
2
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
SDO
GCLK
R-EXT
VDD
LE
1
24 23 22 21 20 19
18
OUT15
OUT0
2
17
OUT14
OUT1
3
16
OUT13
OUT2
4
15
OUT12
OUT3
5
14
OUT11
OUT4
6
13
9 10 11 12
OUT10
OUT5
OUT6
8
GND
7
OUT7
VDD
R-EXT
SDO
GCLK
OUT15
OUT14
OUT13
OUT12
OUT11
OUT10
OUT9
OUT8
OUT8
24
23
22
21
20
19
18
17
16
15
14
13
OUT9
GND 1
SDI 2
DCLK 3
LE 4
OUT0 5
OUT1 6
OUT2 7
OUT3 8
OUT4 9
OUT5 10
OUT6 11
OUT7 12
SDI
DCLK
Pin Configuration
GFN
SSOP/TSSOP
Terminal Description
Function
Pin Name
GND
Ground terminal for control logic and current sink
SDI
Serial data input to the shift register
DCLK
LE
OUT0~OUT15
Clock input terminal used to shift data on rising edge and carries command information when
LE is asserted.
Data strobe terminal and controlling command with DCLK
Constant current output terminals
GCLK
Gray scale clock terminal
Clock input for gray scale. The gray scale display is counted by gray scale clock comparing
with input data.
SDO
Serial data output to the SDI of next driver IC
R-EXT
VDD
Input terminal used to connect an external resistor for setting up output current for all output
channels
3.3V/5V supply voltage terminal
3
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
OUT15
OUT1
OUT0
R-EXT
OUT14
Block Diagram
Io Regulator
Thermal Detector
16
16
Gray Scale Pixel
Buffers
Gray Scale Pixel
GND
Gray Scale Pixel
Gray Scale Pixel
Configuration
Register
SYNC
Control
Comparators
16
16
LE
Comparators
Comparators
Comparators
16bit/12bit
Counter
GCLK
-bit error status
34
Error Detector
34
16
16
8-bit Dot Correction
SDI
256-bit Shift Register (FIFO)
SDO
DCLK
4
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Equivalent Circuits of Inputs and Outputs
GCLK, DCLK, SDI terminal
LE terminal
SDO terminal
Maximum Rating
Characteristic
Symbol
Rating
Unit
Supply Voltage
VDD
0~7
V
Input Pin Voltage (SDI)
VIN
-0.4~VDD+0.4
V
Output Current
IOUT
+80
mA
Sustaining Voltage at OUT Port
VDS
-0.5~5.5
V
GND Terminal Current
IGND
+1280
mA
SSOP24
Power Dissipation
(On PCB, Ta=25°C)
Thermal Resistance
(On PCB, Ta=25°C)
TSSOP24
PD
3.53
QFN24
3.13
SSOP24
49.69
TSSOP24
35.45
QFN24
Empirical Thermal
Resistance
(Ta=25°C)
2.52
SSOP24
Rth(j-a)
40.01
W
˚C/W
78.83
TSSOP24
89.11
QFN24
94.25
Operating Temperature
Topr
-40~+85
˚C
Storage Temperature
Tstg
-55~+150
˚C
5
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Electrical Characteristics (VDD=5.0V, Ta=25°C)
Characteristics
Supply Voltage
Sustaining Voltage at OUT
Ports
Symbol
VDD
-
VDS
OUT0 ~ OUT15
Output Leakage Current
Current Skew (Channel)
Current Skew (IC)
Output Current vs.
Output Voltage Regulation*
Output Current vs.
Supply Voltage Regulation*
“H” level
Input Voltage
“L” level
Output Voltage SDO
LED Open Error Detection
Threshold
Pull-down Resistor of LE
Supply Current
(DCLK=GCLK
=0Hz)
“Off”
“On”
Supply Current
(DCLK=GCLK
=30MHz,
“On”
SDI=15MHz
switching)
Thermal Flag
Temperature 1
Thermal Flag
Temperature 2
*One channel on.
Min.
Typ.
Max.
Unit.
4.5
5.0
5.5
V
-
-
5.5
V
2
-
60
mA
-
-
-1.0
mA
IOH
Refer to “Test Circuit for
Electrical Characteristics”
SDO
IOL
SDO
-
-
1.0
mA
IOUT
VDS=5.5V
-
-
0.5
μA
IOUT
Output Current
Condition
dIOUT
dIOUT2
IOUT=25.8mA
VDS=1.0V
Rext=560Ω
-
±1.0
±2.0
%
IOUT=45mA
VDS=1.0V
Rext=310Ω
-
±1.0
±2.0
%
IOUT=25.8mA
VDS=1.0V
Rext=560Ω
-
±1.5
±3.0
%
IOUT=45mA
VDS=1.0V
Rext=310Ω
-
±1.5
±3.0
%
%/dVDS
VDS within 1.0V and 3.0V,
Rext=560Ω@25.8mA
-
±0.3
±1.0
%/V
%/dVDD
VDD within 4.5V and 5.5V
-
±0.5
±1.0
%/V
VIH
Ta=-40~85ºC
0.7ⅹVDD
-
VDD
V
VIL
Ta=-40~85ºC
GND
-
0.3ⅹVDD
V
VOL
IOL=+1.0mA
-
-
0.4
V
VOH
IOH=-1.0mA
4.6
-
-
V
VDS,TH
-
-
0.30
0.35
V
250
450
800
KΩ
RIN(down) IDD(off) 1
Rext=Open, OUT0 ~ OUT15 =Off
-
2.4
5
IDD(off) 2
Rext=560Ω, OUT0 ~ OUT15 =Off
-
6.5
10
IDD(off) 3
Rext=310Ω, OUT0 ~ OUT15 =Off
-
8.8
12
IDD(on) 1
Rext=560Ω, OUT0 ~ OUT15 =On
-
6.6
11
IDD(on) 2
Rext=310Ω, OUT0 ~ OUT15 =On
-
9.9
13
IDD(on) 1
Rext=560Ω, OUT0 ~ OUT15 =On
-
23.0
-
IDD(on) 2
Rext=310Ω, OUT0 ~ OUT15 =On
-
23.7
-
TTF1
Junction Temperature
-
140
-
˚C
TTF2
Junction Temperature
-
160
-
˚C
mA
6
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Electrical Characteristics (VDD=3.3V, Ta=25°C)
Characteristics
Supply Voltage
Sustaining Voltage at OUT
Ports
Symbol
VDD
-
VDS
OUT0 ~ OUT15
Output Leakage Current
Current Skew (Channel)
Current Skew (IC)
Output Current vs.
Output Voltage Regulation*
Output Current vs.
Supply Voltage Regulation*
“H” level
Input Voltage
“L” level
Output Voltage SDO
LED Open Error Detection
Threshold
Pull-down Resistor of LE
Supply Current
(DCLK=GCLK
=0Hz)
“Off”
“On”
Supply Current
(DCLK=GCLK
=30MHz,
“On”
SDI=15MHz
switching)
Thermal Flag
Temperature 1
Thermal Flag
Temperature 2
Min.
Typ.
Max.
Unit.
3.0
3.3
3.6
V
-
-
5.5
V
2
-
45
mA
-
-
-1.0
mA
IOH
Refer to “Test Circuit for
Electrical Characteristics”
SDO
IOL
SDO
-
-
1.0
mA
IOUT
VDS=5.5V
-
-
0.5
μA
IOUT
Output Current
Condition
dIOUT
dIOUT2
IOUT=25.8mA
VDS=1.0V
Rext=560Ω
-
±1.0
±2.0
%
IOUT=45mA
VDS=1.0V
Rext=310Ω
-
±1.0
±2.0
%
IOUT=25.8mA
VDS=1.0V
Rext=560Ω
-
±1.5
±3.0
%
IOUT=45mA
VDS=1.0V
Rext=310Ω
-
±1.5
±3.0
%
%/dVDS
VDS within 1.0V and 3.0V,
Rext=560Ω@25.8mA
-
±0.3
±1.0
%/V
%/dVDD
VDD within 4.5V and 5.5V
-
±0.5
±1.5
%/V
VIH
Ta=-40~85ºC
0.7ⅹVDD
-
VDD
V
VIL
Ta=-40~85ºC
GND
-
0.3ⅹVDD
V
VOL
IOL=+1.0mA
-
-
0.4
V
VOH
IOH=-1.0mA
2.9
-
-
V
VDS,TH
-
-
0.30
0.35
V
250
450
800
KΩ
RIN(down) IDD(off) 1
Rext=Open, OUT0 ~ OUT15 =Off
-
1.9
4.5
IDD(off) 2
Rext=560Ω, OUT0 ~ OUT15 =Off
-
6.1
9.5
IDD(off) 3
Rext=310Ω, OUT0 ~ OUT15 =Off
-
8.3
11.5
IDD(on) 1
Rext=560Ω, OUT0 ~ OUT15 =On
-
6.1
11
IDD(on) 2
Rext=310Ω, OUT0 ~ OUT15 =On
-
9.4
13
IDD(on) 1
Rext=560Ω, OUT0 ~ OUT15 =On
-
16.2
-
IDD(on) 2
Rext=310Ω, OUT0 ~ OUT15 =On
-
16.7
-
TTF1
Junction Temperature
-
140
-
˚C
TTF2
Junction Temperature
-
160
-
˚C
mA
7
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Test Circuit for Electrical Characteristics
8
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Switching Characteristics (VDD=5.0V; Ta=25°C)
Characteristics
Setup Time
Hold Time
Propagation Delay Time
Staggered Delay of Output
Pulse Width
Symbol
Condition
Min.
Typ.
Max.
Unit.
SDI–DCLK↑
tSU0
5
-
-
ns
LE↑–DCLK↑
tSU1
5
-
-
ns
LE↓–DCLK↑
tSU2
10
-
-
ns
DCLK↑–SDI
tH0
10
-
-
ns
DCLK↑–LE↓
tH1
15
-
-
ns
DCLK–SDO
tPD0
-
25
33
ns
GCLK –OUT4n *
tPD1
-
50
-
ns
LE–SDO**
tPD2
-
30
40
ns
OUT4n +1*
tDL1
-
5
-
ns
OUT4n +2 *
tDL2
-
10
-
ns
OUT4n +3 *
tDL3
-
15
-
ns
LE
tw(L)
15
-
-
ns
VDD=5.0V
VIH=VDD
VIL=GND
Rext=700Ω
VDS=1V
RL=150Ω
CL=10pF
C1=100nF
C2=10μF
CSDO=10pF
VLED=4.0V
In-message Error Detection Duration
(Count by GCLK)
tEDD
-
-
10
GCLK
Compulsory Error Detection Operation
Time***
tERR-C
-
-
700
ns
Data Clock Frequency
FDCLK
-
-
30
MHz
Gray Scale Clock Frequency****
FGCLK
-
-
33
MHz
Rise Time
Switching High-Speed
Fall Time
Speed of
Output
Rise Time
Channels Low-Speed
Fall Time
tOR
-
17
-
ns
-
40
-
ns
-
20
-
ns
-
75
-
ns
tOF
tOR
tOF
GCLK=2MHz
(All channels
turn on)
* Refer to the Timing Waveform, where n=0, 1, 2, 3.
**In timing of “Read Configuration” and “Read Error Status Code”, the next DCLK rising edge should be t PD2 after the
falling edge of LE.
***Users have to leave more time than the maximum error detection time for the error detection.
****With uniform output current.
9
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Switching Characteristics (VDD=3.3V; Ta=25°C)
Characteristics
Setup Time
Hold Time
Propagation Delay Time
Staggered Delay of Output
Pulse Width
Symbol
Condition
Min.
Typ.
Max.
Unit.
SDI–DCLK↑
tSU0
5
-
-
ns
LE↑–DCLK↑
tSU1
5
-
-
ns
LE↓–DCLK↑
tSU2
10
-
-
ns
DCLK↑–SDI
tH0
10
-
-
ns
DCLK↑–LE↓
tH1
15
-
-
ns
DCLK–SDO
tPD0
-
30
40
ns
GCLK –OUT4n *
tPD1
-
60
-
ns
LE–SDO**
tPD2
-
40
50
ns
OUT4n +1*
tDL1
-
5
-
ns
OUT4n +2 *
tDL2
-
10
-
ns
OUT4n +3 *
tDL3
-
15
-
ns
LE
tw(L)
15
-
-
ns
VDD=3.3V
VIH=VDD
VIL=GND
Rext=700Ω
VDS=1V
RL=150Ω
CL=10pF
C1=100nF
C2=10μF
CSDO=10pF
VLED=4.0V
In-message Error Detection Duration
(Count by GCLK)
tEDD
-
-
10
GCLK
Compulsory Error Detection Operation
Time***
tERR-C
-
-
700
ns
Data Clock Frequency
FDCLK
-
-
25
MHz
Gray Scale Clock Frequency****
FGCLK
-
-
20
MHz
Rise Time
Switching High-Speed
Fall Time
Speed of
Output
Rise Time
Channels Low-Speed
Fall Time
tOR
-
20
-
ns
-
50
-
ns
-
25
-
ns
-
90
-
ns
tOF
tOR
tOF
GCLK=2MHz
(All channels
turn on)
* Refer to the Timing Waveform, where n=0, 1, 2, 3.
**In timing of “Read Configuration” and “Read Error Status Code”, the next DCLK rising edge should be t PD2 after the
falling edge of LE.
***Users have to leave more time than the maximum error detection time for the error detection.
****With uniform output current.
10
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Test Circuit for Switching Characteristics
11
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Timing Waveform
(1)
tW(DCLK)
DCLK
tSU1
tH1
tSU2
tw(LE)
LE
tSU0 tH0
SDI
tPD0
tPD2
SDO
(2)
GCLK
tPD1
OUT4n
tDL1
OUT4n+1
tDL2
OUT4n+2
tDL3
OUT4n+3
(3)
1/FGCLK
tW(GCLK)
GCLK
Output
Ports
90%
10%
tOF
90%
10%
tOR
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
12
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Principle of Operation
Power On Reset
Write Configuration
Dot Correction
Enable Output
PWM Gray Data Setting
Disable Output
First users should set the operation modes in the configuration register through the “write configuration” command before
sending gray scale data. During display the operation mode can not be changed.
13
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Application Example
DATA
VLED
OUT0
OUT15
SDI
DCLK
Controller
VLED
LE
GCLK
Error
Read
GCLK
VDD
LD1074
IC1
REXT
VDD
OUT0
OUT15
SDO
DCLK
LE
LD1074
IC n
VDD
VDD
GCLK
GND
RREXT
VLED
SDI
SDO
DCLK
LE
VLED
REXT
GND
RREXT
3
Timing Format
Case1 : DCLK low start, low end
Case2 : DCLK high start, high end
For LD1074, Case1 & Case2 are possible.
14
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Control Command
Signals Combination
Description
Command Name
LE
Number of DCLK Rising
Edge When LE is Asserted
Latch data
High
0
Latch the serial data to the latch for dot
correction or configuration register mode
Dot correction
High
1
Enter the dot correction mode; the shift register
is set to be 128 bits
Enable output
High
3
Enable output channels and activate the PWM
counter
Compulsory error
detection
High
4
Start compulsory error detection
Write configuration
High
5
Write 16-bit configuration register
Read configuration
High
6
Read the configuration register value
Disable output
High
7
Disable output channels and reset the PWM
counter
12-bit gray scale
High
192(12x16)
Set the 12-bit gray scale mode
16-bit gray scale
High
256(16x16)
Set the 16-bit gray scale mode
The Action After a Falling Edge of LE
Note: Please do not use the number of DCLK which are not specified in the table. Otherwise, it might cause
malfunction on the LED drivers.
15
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Definition of Configuration Register
LSB
MSB
F
E
D
C
B
A
9
8
7
6
5
4
3
2
1
0
9
8
7
6
5
4
3
2
1
0
e.g. Default Value
F
E
D
C
B
A
1
1
1
0
1
1
Bit
Attribute
F
Read/Write
PWM gray scale mode
E
Read/Write
PWM algorithm
D
Read/Write
PWM data
synchronization
C
Read/Write
PWM counting mode
B
Read/Write
Thermal shutdown
A
Read/Write
1111111
Value
Function
0
12 bits
1 (Default)
16 bits
0
Conventional PWM
1 (Default)
S-PWM, divide the duty into 64 parts
0
Manual synchronization
1 (Default)
Auto synchronization
0 (Default)
Continuous counting mode
1
One-shot counting mode
0
Disable thermal shutdown
1 (Default)
Enable thermal shutdown
0
Disable both in-message and compulsory
error detections
Error detection
9~8
Read/Write
7
Read/Write
Switching speed of output
Channels
Read/Write
0
Definition
Threshold voltage of
short-circuit detection
6~0
00
Output current gain
adjustment
1 (Default)
Enable both in-message and compulsory
error detections
00(Default)
01
10
11
2’b00: Disable short-circuit detection
2’b01: 0.4xVDD±0.1(V)
2’b10: 0.5xVDD±0.1(V)
2’b11: 0.73xVDD±0.1(V)
0 (Default)
Low switching speed
1
High switching speed
1111111
(Default)
Output current; I=I0xCurrent Gain[6:0]/127;
I0=(VR-EXT/Rext)x23
16
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
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Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Shift Register
The effective length of the shift register in LD1074 is auto-adjusted among 256 / 192 / 128 / 16 bits according to
different modes of input data.
Write Configuration Register
LD1074 can write the configuration register when receiving one LE pulse containing 5 DCLKs, and then send 16-bit
configuration setting to each LED driver. The following waveform shows the input signal waveform when cascading
N pieces of LD1074 :
LE+5DCLKs
LE
DCLK
SDI
Data of 1st LD1074
Cascade N x LD1074
Read Configuration Register
LD1074 can read the configuration register when receiving one LE pulse containing 5 DCLKs in order to set the
shift register length to 16 bits, and then send one LE pulse containing 6 DCLKs to read the configuration setting.
After the command, 16-bit configuration of each LD1074 will be shifted out sequentially from the Nth LD1074 to
the 1st LD1074. The following waveform shows the output signal waveform when cascading N pieces of LD1074 :
LE+5DCLKs
LE+6DCLKs
LE
DCLK
SDO
16-bit configuration register data x N
Cascade N x LD1074
Input the Dot Correction Data
LD1074 can input the dot correction data when receiving one LE pulse containing one DCLK, and then send
128-bit dot correction data to each LED driver. The following waveform shows the input signal waveform when
cascading N pieces of LD1074 :
LE+1DCLKs
LE
DCLK
SDI
12-bit dot correction data x N
Cascade N x LD1074
17
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Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Enable and Disable Output
LD1074 can disable output channels when receiving one LE pulse containing 7 DCLKs. The output channels will
be enabled again when receiving one LE pulse containing 3 DCLKs. This “enable” command can also reactivate the
IC from thermal shutdown when the junction temperature decreases.
Set the PWM Gray Scale Mode
LD1074 provides a selectable 16-bit or 12-bit gray scale mode by setting bit “F” of the configuration register. For
16-bit gray scale mode, the bit “F” is set to “1” (default), and for 12-bit gray scale mode, the bit “F” is set to “0”.
Users need to set the gray scale mode before sending the data, and then send the data from Nth LD1074 to the 1st
LD1074. LD1074 will enter 16-bit gray scale mode when receiving one LE containing 256 DCLKs, and enter 12-bit
gray scale mode when receiving one LE containing 192 DCLKs in order to latch the data. The following waveform
shows the input signal waveform when cascading N pieces of LD1074 :
16-bit gray scale: LE+256 DCLKs
12-bit gray scale: LE+192 DCLKs
16-bit gray scale: LE+256 DCLKs
12-bit gray scale: LE+192 DCLKs
LE
DCLK
SDI
data of Nth~2nd LD1074
data of 1st LD1074
data of Nth~2nd LD1074
data of frame M
data of 1st LD1074
LSB
Gray Scale Data Format
The data input sequence of both 16-bit and 12-bit gray scale data are the same, and the following waveform
illustrates the sequence:
write dot correction
MSB
write PWM data
LSB
MSB
LSB
T1 T1 T2
T128 T1
NxT128
T1 T2
T192 T1
T1 T2
Nth IC
N-1 IC
1st IC
Nth IC
N-1 IC
1st IC
dot correction data
T1-T12
CH15
Bit11
tH2
PWM gray scale data (MSB first)
T13-T24
CH15 CH14
Bit0 Bit11
T192
CH14
Bit0
T169-T180
CH 1
Bit11
T181-T192
CH 1 CH 0
Bit0 Bit11
CH 0
Bit0
tH2: In the end of gray scale mode, DCLK↓–LE↓ should be no less than 10ns.
18
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
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Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Set the PWM Counting Mode
PWM Algorithm
LD1074 defines the different counting algorithms that support scrambled PWM technology, S-PWM. With S-PWM,
the total PWM cycles can be broken down into MSB (Most Significant Bits) and LSB (Least Significant Bits) of gray
scale cycles, and the MSB information can be dithered across 63 refresh cycles.
LD1074 is flexible for either the conventional PWM algorithm or S-PWM algorithm by setting bit “E” of the
configuration register. For S-PWM algorithm, the bit “E” is set to “1” (default), and for conventional PWM algorithm,
the bit “E” is set to “0”:
Conventional PWM
Bit E="0"
Bit F="0": 16-bit PWM Counting, 65536 GCLKs
Bit F="1": 12-bit PWM Counting, 4096 GCLKs
Once of 16-bit/12-bit PWM Counting
S-PWM
Bit E="1"
Bit F="0": MSB 10-bit PWM Counting, 1023 GCLKs
Bit F="1": MSB 10-bit PWM Counting, 1023 GCLKs
LSB 6bit PWM counting
LSB 2bit PWM counting
Output ports are turned “on”.
Synchronization of PWM Cycle
LD1074 is also flexible for either manual synchronization or auto synchronization by setting bit “D” of the
configuration register.
For auto synchronization, the bit “D” is set to “1” (default). LD1074 will automatically process the synchronization of
previous data and next data for PWM counting. The next image data will be updated to output buffers and start PWM
counting when the previous data finishes one internal PWM cycle. This prevents the lost count of image data
resolution and guarantees the data accuracy.
For manual synchronization, the bit “D” is set to “0”. Once the next input data is correctly recognized, LD1074 will
stop the present PWM cycle and restart a new PWM cycle to show the new data immediately.
19
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Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
PWM Counting Mode
Users can set either continuous counting mode or one-shot counting mode by setting bit “C” of the configuration
register.
For the continuous counting mode, the bit “C” is set to “0” (default). In the continuous counting mode, LD1074 will
continuously repeat the PWM cycles and turn on the output channels according to the image data until the next
image data is correctly recognized.
For the one-shot counting mode, the bit “C” is set to “1”. In the one-shot counting mode, LD1074 will run the PWM
cycle for each image data one time, and then stop the output channels until the next image data is correctly
recognized.
Error Detection Principle
LD1074 provides two error detection functions: in-message error detection and compulsory error detection. Users
can read the open-/short-circuit error reports, thermal flag, and REXT open flag from SDO. For all the detection
functions, “0” indicates error or abnormal state and “1” indicates normal state.
In-message Error Detection
Users can set the in-message error detection by bit “A” of configuration register. To enable the in-message error
detection, the bit “A” is set to “1” (default). To disable the in-message error detection, the bit “A” is set to “0”.
The open-/short-circuit error will be reported only when output channels are turned on in 10 GCLKs, and the error
reports will be put into the shift register after the gray scale data is latched.
Since the PWM output duty cycle of LD1074 is the product of gray scale data and dot correction data. If the S-PWM
algorithm is selected, the open-/short-circuit in-message error detection will be performed while the product of gray
scale data and dot correction data is from 640 to 65,535 in the 16-bit gray scale mode or from 640 to 4,095 in the
12-bit gray scale mode. If the conventional PWM algorithm is selected, the open-/short-circuit error will be reported
when the product of gray scale data and dot correction data is larger than 10.
LD1074 will judge if the turn-on time is enough or not to deliver the error report. If the turned-on time is too short,
LD1074 will report normal state coded as “1”.
Error data (N)=error data(N-1) presents detection result.
It will be reset to 1 until the error data is read out.
20
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
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Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Please see the example of the following diagram of 12-bit gray scale mode for the control sequence and data output
format of all error reports.
LE
DCLK
T1 T2
T192
T1 … T10 … TX
GCLK
SDI
T1 T2
…
T1 …
T1 T2 T3
T192
T1
T10 TY
PWM data
OUTn
Internal error
register
10 GCLKs
th
10 GCLKs
<10 GCLKs
th
error status ts-1/m IC
error status ts/nth IC
error status ts/1 IC
error status ts-1/mth IC
SDO
Thermal Alert Thermal Shutdown
OUT15
OUT0 OUT15
11111111…..
Rext open
thermal
open error message
157 bits
1 bits
2 bits
16 bits
OUT0
short error message
16 bits
21
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
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Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Compulsory Error Detection
LD1074 can also perform the compulsory error detection when receiving one LE pulse containing 4 DCLKs and
stop the compulsory error detection when receiving one LE pulse containing 0 DCLK. The output channels will be
forced to turned on within 700ns (between the LE falling edges) to perform the compulsory error detection. The error
report will be pushed out after compulsory error detection operation time (700ns). LD1074 will shift out both open
and short error reports from SDO simultaneously. The following is an illustration of the timing sequence of
compulsory error detection of 12-bit gray scale mode.
Error detection time>700ns
LE
DCLK
T1 T2
T192
T1 T2
T1 T2
T192
T4
GCLK
SDI
PWM data
Internal error
register
Error report
SDO
Error report
Thermal Alert Thermal Shutdown
OUT15
OUT0 OUT15
OUT0
11111111…..
Rext open
thermal
open error message
short error message
157 bits
1 bits
2 bits
16 bits
16 bits
22
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
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Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Setting the Threshold Voltage for Compulsory Short-Circuit Detection
Users can set the threshold voltage (VSD.TH) for compulsory short-circuit detection by bit [9:8] of configuration register
as summarized below:
2’b00: Disable the short-circuit detection (default)
2’b01: 0.4xVDD±0.1(V)
2’b10: 0.5xVDD±0.1(V)
2’b11: 0.73xVDD±0.1(V)
LD1074 provides settable VSD,TH for different LED configuration. If the detected voltage is larger than VSD.TH, the
LD1074 identifies the LED as short-circuit. For example, if each output channel of LD1074 drives one red LED,
the VSD,TH should be set smaller. If each output channel of LD1074 drives several white LEDs, the VSD,TH should be
set larger. The system should consider the accumulated VF of the LEDs to set a suitable VSD,TH.
VLED
VDD
R
VF
VSDTH
VDS
Thermal Protection
Users can set the thermal protection by bit “B” of configuration register. To enable the thermal shutdown function,
the bit “B” is set to “1” (default). To disable the thermal shutdown function, the bit “B” is set to “0”.
LD1074 provides two thermal flags:
Thermal flag 1 is over-temperature alarm, and thermal flag 2 is thermal shutdown. When the IC junction temperature
is over 140°C, thermal flag 1 will report “0”. When the IC junction temperature is under 120°C, thermal flag 1 will
recover to “1”.
When the IC junction temperature is over 160°C, the thermal flag 2 will become “0” and LD1074 will turn off the
output current of all channels automatically. LD1074 will turn on the output channels when receiving one LE pulse
containing 3 DCLKs.
23
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Adjust the Switching Speed of the Output Channels
Users can select the switching speed of output channels by bit “7” of configuration register. For low switching speed,
the bit “7” is set to “0” (default). For high switching speed, the bit “7” is set to “1”.
Low switching speed helps to reduce the EMI and overshoot of the output channels. On the other hand, high
switching speed is suitable for high GCLK frequency and high refresh rate applications.
Adjust the Output Current Gain
Users can adjust output current gain by bit [6:0] of configuration register. The default current gain value is
7b’1111111.
The output current; I=I0xCurrent Gain [6:0]/127, where I0=(VR-EXT/Rext)x23
The current gain value is proportional to the output current. In other words, current gain value versus output current
is linear. This function helps users to tune the output current by software in stead of by hardware for daily operation.
24
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Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Setting Output Current
The output current (IOUT) is set by an external resistor, Rext. The default relationship between IOUT and Rext is shown in
the following figure.
Also, the output current can be calculated from the equation:
VR-EXT=0.61xG/127; IOUT=(VR-EXT/Rext)x23
Whereas Rext is the resistance of the external resistor connected to R-EXT terminal and VR-EXT is its voltage. G is the
digital current gain, which is set by the bit[6:0] of the configuration register. The default value of G is 127. For your
information, the output current is about 25mA when Rext=560Ω and 45mA when Rext=310Ω if G is set to default value
127. The formula and setting for G are described in further section.
LD1074 Rext vs. IOUT
-표준
IOUT(mA)
-표준
-표준
-표준
-표준
-표준
-표준
-표준
Rext(Ω)
25
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Constant Current
In LED display application, LD1074 provides nearly no variation in current from channel to channel and from IC to
IC. This can be achieved by:
1) The typical current variation between channels is less than 1.5%, and that between ICs is less than ±3%.
2) In addition, the current characteristic of output stage is flat and users can refer to the figure as shown below. The
output current can be kept constant regardless of the variations of LED forward voltages (VF). This guarantees LED
to be performed on the same brightness as user’s specification.
26
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Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
Staggered Delay of Output
LD1074 has a built-in staggered circuit to perform delay mechanism. Among output ports exist a graduated 5ns
delay time among OUT4n , OUT4n +1 , OUT4n + 2 , and OUT4n + 3 , by which the output ports will be
divided to four groups at a different time so that the instant current from the power line will be lowered.
Package Power Dissipation (PD)
The maximum allowable package power dissipation is determined as PD(max)=(Tj–Ta)/Rth(j-a). When 16 output
channels are turned on simultaneously, the actual package power dissipation is
PD(act)=(IDDxVDD)+(IOUTxDutyxVDSx16). Therefore, to keep PD (act)≤PD (max), the allowable maximum output current
as a function of duty cycle is:
IOUT={[(Tj–Ta)/Rth(j-a)]–(IDDxVDD)}/VDS /Duty/16, where Tj=150°C.
LD1074 SSOP
LD1074 TSSOP
LD1074 GFN
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Device
Type
Rth(j-a)
(˚C/W)
SSOP
49.69
TSSOP
35.45
GFN
40.01
27
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
The maximum power dissipation, PD(max)=(Tj–Ta)/Rth(j-a), decreases as the ambient temperature increases.
LD1074 Maximum Power Dissipation at Various Ambient Temperature
Usage of Thermal Pad
The PCB area L2xW2 is 4 times of the IC’s area L1xW1.The thickness of the PCB is 1.6mm, copper foil 1 Oz. The
thermal pad on the IC’s bottom has to be mounted on the copper foil.
28
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
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Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
LED Supply Voltage (VLED)
LD1074 are designed to operate with VDS ranging from 0.4V to 1.0V (depending on IOUT=2~60mA) considering the
package power dissipating limits. VDS may be higher enough to make PD (act) >PD (max) when VLED=5V and
VDS=VLED–VF, in which VLED is the load supply voltage. In this case, it is recommended to use the lowest possible
supply voltage or to set an external voltage reducer, VDROP.
A voltage reducer lets VDS=(VLED–VF)–VDROP.
Resistors or Zener diode can be used in the applications as shown in the following figures.
Switching Noise Reduction
LED drivers are frequently used in switch-mode applications which always behave with switching noise due to the
parasitic inductance on PCB. To eliminate switching noise, refer to “Application Note for 8-bit and 16-bit LED
Drivers-Overshoot”.
29
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
30
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
31
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1
LD1074
16-Channel Constant Current LED Driver With 16-Bit PWM Control and Dot-Correction
32
LDT Inc. WE bldg. 5F, 126-33 Han-dle 1ro, Seobuk-gu, Cheonan, Chungnam, korea, 331-220
Tel. +82 41 520 7300 Fax. +82 41 520 7337 www.ldt.co.kr
Ver 1.1