16-CHANNEL CONSTANT CURRENT LED DRIVER WITH

DM634
Version
: A.004
Issue Date : 2010/07/28
File Name : SP-DM634-A.004.doc
Total Pages : 25
16-CHANNEL CONSTANT CURRENT LED DRIVER
WITH PROGRAMMABLE PWM OUTPUTS
新竹市科學園區展業一路 9 號 7 樓之 1
SILICON TOUCH TECHNOLOGY INC.
9-7F-1, Prosperity Road I, Science Based Industrial Park,
Hsin-Chu, Taiwan 300, R.O.C.
Tel：886-3-5645656
Fax：886-3-5645626
DM634
DM634
16-CHANNEL CONSTANT CURRENT LED DRIVER
WITH PROGRAMMABLE PWM OUTPUTS
General Description
DM634 is a 16-channel constant current sink LED driver. Each channel has adjustable 16-bits
(65536 steps) grayscale PWM control current outputs. 7-bit global brightness control is included in
supporting user to adjust chip current easily. It incorporates shift registers, data latches, constant
current circuitry with current value set by an external resistor, selectable oscillator source for PWM
functioning, and built-in LED open/short detection circuit to detect error status. It supports thermal
alarm and shutdown function; system retrieve the message to indicate when junction temperature
over limitation of chip. It is specifically designed for LED display and lighting applications.
Features
z
Constant-current outputs: 5mA to 90mA
z
16-bit linear PWM control current output per channel
z
7-bit high accuracy global brightness control
z
Maximum output voltage: 17V
z
Maximum clock frequency: 25MHz
z
Selectable internal/external PWM reference clock
z
PWM free-running capability (refresh rate ~ 275 Hz with internal oscillator ~ 18 MHz)
z
Build-in real-time LED open/short detection
z
Thermal Alarm and Shotdown –
Alarm : Junction Temperature >110℃
Shutdown : Junction Temperature > 180℃
z
Package and pin assignment (except QFN32) compatible to conventional LED driver series
(ST2221C, DM134B/5B, DM13C)
z
Power supply voltage: 3.3V to 5.5 V
Applications
z Indoor/Outdoor LED Video Display
z
LED Variable Message Signs (VMS) System
z
LED Decorative Lighting
Package Types
z
SOP24, SSOP24, TSSOP24E (with exposed pad)
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 1
DM634
Block Diagram
OUT 0
OUT 1
OUT 15
LED Open/Short
Detector
(0)
LED Open/Short
Detector
(1)
LED Open/Short
Detector
(15)
7-bit High
Accuracy Global
Brightness
Control
Constant Current Driver
(0)
Constant Current Driver
(1)
Constant Current Driver
(15)
REXT
16-bit
Counter
16-bit PWM Generator
(0)
16-bit PWM Generator
(1)
16-bit PWM Generator
(15)
SOMODE/
GCK
VCC
GND
16
LAT
16-bit Latch Register
(0)
16
16-bit Latch Register
(1)
16
DAI
16
16-bit Latch Register
(15)
16
16
16-bit Shift Register
16-bit Shift Register
16-bit Shift Register
(0)
(1)
(15)
DAO
DCK
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 2
DM634
Pin Connection
GND
DAI
DCK
LAT
OUT0
OUT1
OUT2
OUT3
OUT4
OUT5
OUT6
OUT7
1
24
2
23
3
22
4
SOP24
5
21
20
6
SSOP24
19
7
TSSOP24E
18
8
17
9
16
10
15
11
12
14
( top view )
13
VCC
REXT
DAO
SOMODE/GCK
OUT 15
OUT 14
OUT 13
OUT 12
OUT 11
OUT 10
OUT 9
OUT 8
Pin Description
PIN No.
PIN NAME
FUNCTION
SOP24/SSOP24/TSSOP24E: 1
TSSOP24E: exposed pad
GND
Ground terminal.
SOP24/SSOP24/TSSOP24E: 2
DAI
Serial data input terminal.
SOP24/SSOP24/TSSOP24E: 3
DCK
Synchronous clock input terminal for serial data
transfer. Data is sampled at the rising edge of DCK.
LAT
Input terminal of data strobe:
‘H’ means data on shift register goes through
latch
(level trigger),
‘L’ means data is latched.
SOP24/SSOP24/TSSOP24E: 4
SOP24/SSOP24/TSSOP24E: 5~20
OUT0~15 Sink constant-current outputs (open-drain).
SOP24/SSOP24/TSSOP24E: 21
Serial Out Mode Selection(SOMODE) :
‘H’: DAO is shifted out and synchronized to
falling edge of DCK,
SOMODE
‘L’ : DAO is shifted out and synchronized to
/GCK
rising edge of DCK.
Gray Scale Clock(GCK) : Input terminal for PWM
operation.
SOP24/SSOP24/TSSOP24E: 22
DAO
Serial data output terminal.
SOP24/SSOP24/TSSOP24E: 23
REXT
External resistors connected between REXT and
GND for output current value setting.
SOP24/SSOP24/TSSOP24E: 24
VCC
Supply voltage terminal.
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 3
DM634
Equivalent Circuit of Inputs and Outputs
1. DCK, DAI, LAT , SOMODE/GCK terminals
2. DAO terminals
PCB Layout Consideration
To connect an external resistor to REXT pin and ground can determine the maximum output
current. If there is any disturbance occurred to REXT pin, the constant current output may be
unstable or noisy. Since REXT (pin23), DAO (pin22), and SOMODE/GCK (pin21) are next to each
other, the most possible interference is caused by DAO or SOMODE/GCK signal. Accordingly, it is
recommended that adding some shielding area within the above pins in PCB layout, or laying the
signal line of above pins on different PCB layer will prevent the noise problems effectively.
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 4
DM634
Maximum Ratings (Ta=25°C, Tj(max) = 150°C)
CHARACTERISTIC
Supply Voltage
Input Voltage
SYMBOL
RATING
UNIT
VCC
-0.3 ~ 7.0
V
VIN
-0.3 ~ VCC+0.3
V
Output Current
IOUT
100
mA
Output Voltage
VOUT
-0.3 ~ 17
V
Input Clock Frequency
FDCK
25
MHz
GND Terminal Current
IGND
1600
mA
Power Dissipation
(4 layer PCB, Ta=25°C)
PD
Thermal Resistance
(4 layer PCB, Ta=25°C)
Rth(j-a)
4.31(TSSOP24E exposed pad)
W
2.5(SOP24)
1.81(SSOP24 )
29 ( TSSOP24E exposed pad)
°C/W
50 (SOP24)
69 (SSOP24 )
Operating Temperature
Top
-40 ~ 85
°C
Storage Temperature
Tstg
-55 ~ 150
°C
Recommended Operating Condition
CHARACTERISTIC
SYMBOL
CONDITION
MIN.
TYP.
MAX.
UNIT
Supply Voltage
VCC
⎯
3.3
5.0
5.5
V
Output Voltage
VOUT
Driver On
1.0
⎯
0.5VCC
Output Voltage
VOUT
Driver Off
⎯
⎯
17
Output Current
*2
IO
OUTn
5
⎯
90
IOH
VOH = VCC – 0.4 V
-0.8
⎯
-2
IOL
VOL = 0.2 V
VIH
Input Voltage
*1
VIL
VCC = 3.3 V ~ 5.5V
+0.8
⎯
+2
⎯
VCC
0.0
⎯
0.2VCC
FDCK
Single Chip Operation
⎯
⎯
25
Input PWM Frequency
FGCK
VCC= 3.3V ~ 5.5V
⎯
⎯
25
15
⎯
⎯
Pulse Width
tw LAT
tw DCK
15
⎯
⎯
Set-up Time for DAI
tsetup(D)
10
⎯
⎯
Hold Time for DAI
thold(D)
10
⎯
⎯
Set-up Time for LAT
tsetup(L)
10
⎯
⎯
Hold Time for LAT
thold(L)
10
⎯
⎯
FOSC
14.4
18
22
DCK Pulse Width
Internal Oscillator Frequency
*1
*2
VCC = 5.0V
mA
0.8VCC
Input Clock Frequency
V
V
MHz
ns
MHz
Notice that the power dissipation is limited to its package and ambient temperature.
The driver output voltage including any overshoot stress has to be compliant with the maximum voltage (17V).
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 5
DM634
Electrical Characteristics (VCC = 5.0 V, Ta = 25°C, GBC = 95 unless otherwise noted)
CHARACTERISTIC
Output Leakage Current
SYMBOL
CONDITION
MIN.
TYP.
MAX.
UNIT
IOL
VOH = 17 V
⎯
⎯
±1.0
uA
VOL
IOL = 1.5 mA
⎯
⎯
0.4
VOH
IOH= -1.3mA
4.5
⎯
⎯
⎯
⎯
±3
%
18.275
⎯
20.607
mA
Rrext = 2.2 KΩ
VOUT = 1 V ~ 3 V
⎯
±0.1
±0.5
% / VCC
Rrext = 2.2 KΩ
⎯
±1
±4
IDD(off)
power on
all pins are open
unless VCC and GND
(free-running mode)
⎯
5.41
6.5
IDD(off)
power on
all pins are open
unless VCC and GND
(external GCK mode)
⎯
4.61
⎯
IDD(off)
input signal is static
Rrext = 12.4 KΩ
all outputs turn off
⎯
5.97
⎯
IDD(off)
input signal is static
Rrext = 2.2 KΩ
all outputs turn off
⎯
8.27
⎯
IDD(off)
input signal is static
Rrext = 570 Ω
all outputs turn off
⎯
17.61
⎯
Output Voltage (S-OUT)
Output Current Skew
(Channel-to-Channel)
*1
Output Current Skew
(Chip-to-Chip)
*2
Output Voltage Regulation
Supply Voltage Regulation
Supply Current
IOL1
V
VOUT = 1.0 V
Rrext = 2.2 KΩ
IOL2
% / VOUT
*3
%/V
mA
mA
*1
Channel-to-channel skew is defined as the ratio between (any Iout – average Iout) and average Iout, where average
Iout = (Imax + Imin) / 2.
*2
Chip-to-Chip skew is defined as the range into which any output current of any IC falls.
*3
IO excluded.
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 6
DM634
Electrical Characteristics (VCC = 3.3 V, Ta = 25°C, GBC = 95 unless otherwise noted)
CHARACTERISTIC
Output Leakage Current
SYMBOL
CONDITION
MIN.
TYP.
MAX.
UNIT
IOL
VOH = 17 V
⎯
⎯
±1.0
uA
VOL
IOL = 1.5 mA
⎯
⎯
0.4
VOH
IOH= -1.3 mA
2.8
⎯
⎯
⎯
⎯
±3
%
18.275
⎯
20.607
mA
Rrext = 2.2 KΩ
VOUT = 1 V ~ 3 V
⎯
±0.1
±0.5
% / VCC
Rrext = 2.2 KΩ
⎯
±1
±4
IDD(off)
power on
all pins are open
unless VCC and GND
(free-running mode)
⎯
4.19
⎯
IDD(off)
power on
all pins are open
unless VCC and GND
(external GCK mode)
⎯
3.79
⎯
IDD(off)
input signal is static
Rrext = 12.4 KΩ
all outputs turn off
⎯
4.75
⎯
IDD(off)
input signal is static
Rrext = 2.2 KΩ
all outputs turn off
⎯
7.04
⎯
IDD(off)
input signal is static
Rrext = 570 Ω
all outputs turn off
⎯
16.014
⎯
Output Voltage (S-OUT)
Output Current Skew
(Channel-to-Channel)
*1
Output Current Skew
(Chip-to-Chip)
*2
Output Voltage Regulation
Supply Voltage Regulation
Supply Current
IOL1
V
VOUT = 1.0 V
Rrext = 2.2 KΩ
IOL2
% / VOUT
*3
%/V
mA
*1
Channel-to-channel skew is defined as the ratio between (any Iout – average Iout) and average Iout, where average
Iout = (Imax + Imin) / 2.
*2
Chip-to-Chip skew is defined as the range into which any output current of any IC falls.
*3
IO excluded.
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 7
DM634
Switching Characteristics (VCC = 5.0V, Ta = 25°C, GBC = 95 unless otherwise noted)
CHARACTERISTIC
SYMBOL
(‘H’ to ‘L’)
TYP.
MAX.
⎯
47.5
⎯
⎯
25
⎯
⎯
14.4
⎯
⎯
28.5
⎯
VIL = GND
⎯
24
⎯
Rrext = 2.2 KΩ
⎯
9.7
⎯
⎯
15
⎯
⎯
7.5
⎯
td
⎯
33
⎯
top*1
⎯
⎯
4.6
tpLH
DCK(rising)-to-DAO
Propagation Delay
MIN.
GCK-to-OUT
Propagation Delay
(‘L’ to ‘H’)
CONDITION
DCK(falling)-to-DAO
VIH = VCC
GCK-to-OUT
DCK(rising)-to-DAO
tpHL
DCK(falling)-to-DAO
Output Current Rise Time
tor
Output Current Fall Time
tof
VL = 5.0 V
CL = 13 pF
Output to output Delay Time Unit
Output Current
(Propagation Delay after LAT trigger)
UNIT
ns
ms
Switching Characteristics (VCC = 3.3V, Ta = 25°C, GBC = 95 unless otherwise noted)
CHARACTERISTIC
SYMBOL
TYP.
MAX.
⎯
51.5
⎯
⎯
30.5
⎯
⎯
18.3
⎯
⎯
31.5
⎯
⎯
29
⎯
Rrext = 2.2 KΩ
⎯
14.4
⎯
VL = 3.3 V
⎯
20
⎯
⎯
10
⎯
⎯
34
⎯
⎯
⎯
4.6
tpLH
DCK(rising)-to-DAO
DCK(falling)-to-DAO
VIH = VCC
GCK-to-OUT
Propagation Delay
DCK(rising)-to-DAO
(‘H’ to ‘L’)
MIN.
GCK-to-OUT
Propagation Delay
(‘L’ to ‘H’)
CONDITION
VIL = GND
tpHL
DCK(falling)-to-DAO
Output Current Rise Time
tor
Output Current Fall Time
tof
Output to output Delay Time Unit
td
Output Current
(Propagation Delay after LAT trigger)
CL = 13 pF
top*1
UNIT
VL
VCC
A
DAI
OUTn
DCK
CL
CL
CL
CL
REXT
LAT
SOMODE DAO
/GCK
Rrext
CL
GND
Switching Characteristics Test Circuit
*1
Reload the new PWM data at the end of the last PWM frame.
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 8
ns
ms
DM634
Constant-Current Output
Constant-current value (Iout*1) of each output channel is set by an external resistor connected
between the REXT pin and GND. The current scale ranging can be adjusted from 5mA to 70mA by
varying the resistor value. User can input GBC value to increase Iout to 90mA. The reference
voltage of REXT terminal (Vrext) is approximately 1.23V. The output current value is calculated by
the following equation:
Iout(mA)
5
10
20
30
40
50
60
70
M
41.13
39.35
36.78
35.09
33.75
32.53
31.35
30.09
Output Current as a Functiono Rext value
80
70
Iout(mA)
60
Iout*1 (mA) ~
50
V rext(V)
× M
Rrext (KΩ)
40
30
20
10
0
0
1
2
3
4
5
6
7
8
9
10
Rext(KΩ)
Output Current as a Function of Output Voltage
80
70
Iout (mA)
60
50
40
30
20
10
0
0
0.5
1
1.5
2
2.5
3
Vout (V)
In order to obtain a good performance of constant-current output, a suitable output voltage is
necessary. Users can get related information about the minimum output voltage above.
*1
Iout is typical current value setting under 100% PWM duty cycle and 95 DGBC Value.
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 9
DM634
Serial Data Interface
The serial-in data (DAI) will be clocked into 16 × 16 bit shift registers synchronized on the
rising edge of the clock (DCK). The data will be transferred into the 16 × 16 bit latch registers
when the strobe signal ( LAT ) is kept at high level (level trigger); otherwise, the data will be held.
The latch pulse should be sent after the falling edge of the last clock within a frame data. The trigger
timing of the serial-out data (DAO) will be shifted out on synchronization to the rising edge of the
clock if serial out selection (SOMODE) is kept at low level. And if serial out selection (SOMODE)
is kept at high level, the serial-out data (DAO) will be shifted out on synchronization to the falling
edge of the clock (DCK).
Input Data Format
Serial-out Data Format
shift out first
OUT 15
D15 [15]
THF
D15[13]
D15 [12]
D15[11]
D15 [10]
D15 [9]
MSB
D14 [15]
D15[8]
D15[7]
D15 [6]
D15[5]
D15[4]
D 15[3]
D15 [2]
D15[1]
LSB
OUT 14
D14[14]
D14 [13]
D14 [12]
D14[11]
D14 [10]
D14[9]
D14[8]
D14 [7]
E[15]
D14[6]
D14[5]
D 14[4]
D14 [3]
D14[2]
D 14[1]
E[14]
LSB
MSB
OUT 0
D0 [15]
D0 [14]
D0 [13]
D0[12]
D0 [11]
D0[10]
D0 [9]
D0 [8]
D0[7]
D0 [6]
D0 [5]
D0[4]
D 0[3]
D0 [2]
D0 [1]
E[0]
LSB
MSB
＊E[15], E[14], ... E[ 0 ] are Error Messages of LED Open Detection. ｀1＇is normal, and ｀0＇is abnormal.
＊THF is the Error Message of chip thermal detection. ｀1＇is normal, and ｀0＇is abnormal.
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 10
DM634
LED Open/Short Detection
DM634 provides a real time monitor of LED open / short detection function without extra
components or circuit design. When O/S flag*1 set “L”, it will be identified as a LED open failure
when the output is turned on but the output voltage is below 0.3V. The test result of each channel
will write to its correspondent shift register which is in LSB position (D15[0], D14[0], …., D0[0])
while strobe signal is active. User can refer to timing diagram on page12. Detecting report could be
retrieved from serial-out (DAO) data. If the system reads ‘1’ back, that indicates LED is in normal
status. But if ‘0’ was retrieved, it means LED open failure has occurred. In the short detection, O/S
flag set “H”. And system reads result as ‘1’ means normal, ‘0’ means LED short failure occurred.
The short detection threshold voltage is 65% of VCC. In order to make sure LED open/short
detection function is in well operating condition, it is recommended that all the luminance data are
wrote to ‘1’ then almost turning on the outputs during detection process.
Thermal Alarm and Shutdown
During operation, when the junction temperature of the chip reaches approximately above
180℃, driver will shutdown all the outputs. Basically, the chip will cool down and return to the
safe operating temperature which is approximately below 110℃. DM634 will restart all the outputs
at the same time. Operating upon 180℃ may cause chip to be damaged permanently.
Normal
Normal
Shutdown
Shutdown
Alarm
T( ℃ )
110 ℃
180 ℃
DM634 provides a real time monitor of chip thermal alarm and shutdown function. Except
avoid the damage occurs when local junction temperature over the limitation, system can recognize
which chip is under this situation. When O/S flag set “ 0”, it will be identified as the chip thermal
over 110℃ as the THF flag retrieved ‘ 0’. The test result of each chip will write to its correspondent
shift register which is in the position (D255[0]) while strobe signal is active. User can refer to timing
diagram on page14. Detecting report could be retrieved from serial-out (DAO) data. If the system
reads ‘ 1’ back, that indicates chip is in normal status. But if ‘ 0’ was retrieved, it means the chip
juction temperature is over 180℃ when O/S flag set to ‘ 1’ .
*1
“L” is the default value of O/S flag. User can refer to Global Brightness Control to know how to set O/S flag on page
16.
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 11
DM634
Selection of Internal/External PWM Frequency
The default operation mode is the free-running PWM signal generated by internal oscillator
after power-on. Users could switch internal to external PWM frequency source by following timing
sequence. There are two alternative options could be selected. The option 1 shows three rising edges
of latch pulse ( LAT ) when the clock (DCK) kept at high level then two rising edges of clock (DCK)
pulse when the latch pulse ( LAT ) kept at high level. Then the SOMODE/GCK pin could input
external frequency to operate PWM function. The option 2 shows four rising edges of latch
pulse( LAT ) when clock(DCK) kept at high level then sending three rising edges of clock (DCK)
signal, while latch( LAT ) signal kept high level at the same time. Meanwhile the GCK external mode
can be set back to the free-running mode. Notice that when internal RESET at low level, all the shift
registers in DM634 will be cleared (Kept at Low level) and all output current will be off
immediately.
DCK
LAT
Normal Operation
1
t
2
1
DCK
2
3
DCK
1
2
3
1
LAT
LAT
RESET
(internal)
RESET
(internal)
2
3
t
t
Option 1 : Timing Combination to set up
external GCK mode
16-channel 16-bit PWM Constant Current LED Driver
4
Option 2 : Timing Combination to set up
free-running mode
Version : A.004
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Page 12
DM634
Timing Diagram
1. DCK(rising edge) - DAI, DAO (SOMODE = ”L” at free-running mode, or external GCK
mode)
2. DCK(falling edge) - DAO (SOMODE = “H” at free-running mode)
tw DCK
DCK
50%
twDCK
50%
50%
50%
50%
DAO
50%
tpLH
tpHL
3. DCK-LAT
50%
50%
DCK
t setup(L)
t hold(L)
50%
50%
LAT
twLAT
4. Output to Output Delay Time Unit (n=2,3,4,5,6,7,10,11,12,13,14,15)
50%
OUTn
td
50%
OUTn-2
5. GCK-OUT0
50%
50%
GCK
50%
OUT0
tpLH
16-channel 16-bit PWM Constant Current LED Driver
50%
t pHL
Version : A.004
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Page 13
4
*5
256
DA [255]
DA [0]
9
E[0]* 2
Frame Data A*
256
DB [0]
DB[255]
1
DC[255]
2
DC[254]
*7
65536 x GCK
256
DC[0]
DC [255]
16-channel 16-bit PWM Constant Current LED Driver
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8
DC [253]
Page 14
Input GCK Frequency (Hz)
Total PWM resolution (216)
For example, if the refresh rate in display system is higher than 60Hz, the input GCK frequency must be higher than 4M Hz.
Refresh Rate (Hz) =
When using external frequency for PWM operation, the PWM refresh rate (frame rate) can be calculated by following equation :
*6
*5
THFC
2
DD[254]
Frame Data C*
1
DD[255]
SOMODE function work in free-running mode. SOMODE default value is“L＂when external GCK mode selected.
When switching to external GCK mode, all registers in DM634 will be reset simultaneously.
*7 Starting the new PWM frame after the last PWM period finish competely.
*8 When swithcing to GCK mode, outputs will be active after 65536 GCK pulses.
*2
LAT is level trigger, not edge trigger.
DA[1]
255
DB [1]
THF is the flag of alarm / shutdown according to O/S flag is“L＂/“H＂ .
254
DB [2]
*4
THFA
2
DB[2 54]
*3
1
DB[255]
Grayscale data clock-in period
DAO is shifted out on synchronization to rising / falling edge of DCK according to SOMODE is “L＂ / “H＂.
E[0] is the error message of LED open/short detection according to O/S flag is “L＂/“H＂.
Frame Data Z
65536 x GCK(internal)
E[0]*2
255
254
DZ[1]
DA [1]
DA[2]
External GCK mode switch
*1
(current )
OUTn
SOMODE* /GCK
3
LAT*
DAO
*1
DCK
DAI
Grayscale data clock-in period
off
on
0
1
low
high
0
1
low
high
0
1
DM634
Timing Diagram (free-running mode switch to external GCK mode example)
(current )
OUTn
SOMODE/GCK
LAT
DAO
DCK
DAI
256
ED [255]
Frame Data C
65536 x GCK
DD[0]
1
2
ED[253]
DE[254]
THFD
DE[255]
Grayscale data clock-in period
256
2
Frame Data D
1
EE [255]
3
DE[0]
4
1
THFE
Internal GCK mode switch
2
EE [253]
3
1
DF[255]
2
DF[254]
65536 x GCK(internal)
256
DF [0]
DF [255]
THFF
2
DF[253]
DG[254]
Frame Data E
1
DG[255]
Grayscale data clock-in period
off
on
0
1
low
high
0
1
low
high
0
1
DM634
Timing Diagram (external GCK mode switch to free-running mode example)
16-channel 16-bit PWM Constant Current LED Driver
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Page 15
DM634
Output Modulation Technique
DM634 provides a new LED drive technique of output modulation. It mixes traditional Pulse
Width Modulation (PWM) represented by LSB 12 bit with Sequential Split Modulation (SSM)
represented by MSB 4 bit. The main benefits of SSM are to drive LED with an equivalent higher
refresh rate (up to 380Hz in DM634 when FGCK = 25MHz) and change bit to next bit smoothly. The
relationships between PWM and SSM in time domain can be refer to the diagram below (not to
scale):
A complete modulation cycle
0
8
1
9
2
10
3
11
4
12
5
13
6
14
7
15
Sequential Split Modulation represented by Bit [15:12]
t
Traditional PWM Width represented by Bit [11:0]
Ultra High Resolution Current Outputs
DM634 could provide 16-bit linear PWM control current outputs for each channel. There are
two advantages for system design. One is DM634 has sufficient bit resolution (65536 steps), not
only LED color information but additional data such as global brightness, dot correction, and
gamma correction can be represented by the proper algorithms. The other is to reduce a lot of clock
and data rate compared to conventional ON-OFF type LED drivers.
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 16
DM634
High Accuracy Global Brightness Correction
DM634 has built-in global brightness Correction feature. It can save PCB space and cost of
system by eliminating the circuit of Rrext value adjusting or voltage drop adjusting across the
external resistors. The output current is calculating by following equation*1*2*3:
Iout*1 = Vrext / Rext x M*2 x ( 1 + DGBC*3)/96
Global Brightness data and Open/Short Flag format
shift in first
D C [6]
D C [5]
D C [4]
D C [3]
D C [2]
D C [1]
D C [0]
O/S
LSB
MSB
The Shift in data sequence of GBC data and detection flag as above. Dc[6], Dc[5] to Dc[0] are
7-bit data of GBC value. The last bit O/S is the flag of detection. When O/S flag set “L”, the LED
open detection function be selected. Otherwise, if the flag set “H”, the LED short failure detection
function be selected. .
Global Brightness Control
The default GBC data (DGBC) is “1011111” (Iout = 75% Imax*4 ) after power-on. Users could
shift GBC data in by following timing sequence without changing luminous data. The sequence
shows four triggering latch pulses ( LAT ) with high level clock (DCK), circuit switch into GBC
mode at falling edge of the 4th latch pulse ( LAT ) then user can make eight triggering clock pulses to
set 7-bit GBC data and O/S flag. Notice that PWM data won’t be changed while GBC data is
latched.
1
2
254 255 256
1
2
3
4
5
6
7
8
DCK
1
2
3
4
LAT
t
Timing Combination to set GBC data and O/S flag
*1
Iout is the current value setting under 100% PWM duty cycle.
Vrext/Rext * M as the equation in Page 9.
*3
DGBC is the data of global brightness correction. User can refer to Timing Sequence to know how to set DGBC on page 18.
*4
Imax means the GBC data is “1111111”.
*2
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 17
(current)
OUTn
*1
SOMODE/GCK
LAT
DAO
DCK
DAI
255
254
256
DA [255]
65536 x GCK(internal)
DA [0]
GBC mode switch
GBCZ [6]
2
*1
GBCZ [4]
Frame Data A
GBCZ [5]
1
GBCA[6] GBCA[5]
8
O/SA
GBCZ [0]
7
GBCA[0]
GBC data clock-in period
The difference between Frame data A and Aa is max output current.
Frame Data Z
E[0]
DA [1]
DA[2]
DZ[1]
Grayscale data
clock-in period
O/SZ
DA [247]
1
2
DA [245]
DB [254]
DA [246]
DB [255]
255
O/SZ
DB [1]
Frame Data Aa
DB [255]
256
DB [0]
Grayscale data clock-in period
off
on
0
1
low
high
0
1
low
high
0
1
DM634
Timing Diagram (GBC data input example)
16-channel 16-bit PWM Constant Current LED Driver
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Page 18
DM634
Output to Output Delay
DM634 has build-in output to output delay with a special arrangement. This arrangement help
chip avoid noise cause by large current during channels switching. The arrangement details are
shown as following table.
Channel
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15
Delay units 0
4
1
5
2
6
3
7
3
7
2
4
1
5
0
4
Power Dissipation
The power dissipation of a semiconductor chip is limited to its package and ambient
temperature, in which the device requires the maximum output current calculated for given
operating conditions. The maximum allowable power consumption can be calculated by the
following equation:
Tj(junction temperature)(max)(°C)– Ta(ambient temperature)(°C)
Pd(max)(Watt) =
Rth(junction-to-air thermal resistance)(°C/Watt)
The relationship between power dissipation and operating temperature can be referred to the
figure below:
5
Power Dissipation Pd(W)
4.5
TSSOP24E
Tj(max)=150°C
4
Rth(TSSOP24E)=29°C/Watt
3.5
Rth(SOP24)=50°C/Watt
3
Rth(SSOP24)=69°C/Watt
SOP24
2.5
2
SSOP24
1.5
1
0.5
0
0
20
40
60
80
100
120
140
160
Ambient Temperature Ta ( ℃ )
The power consumption of IC can be determined by the following equation and should be less
than the maximum allowable power dissipation:
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 19
DM634
Typical Application
DM634
DM634
DM634
DM634
DM634
DM634
DM634
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 20
DM634
Package Outline Dimension
DM634-SSOP
SYMBOLS
DIMENSIONS IN INCH
DIMENSIONS IN MM
A
0.053
0.064
0.069
1.346
1.626
1.753
A1
0.004
0.006
0.010
0.102
0.152
0.254
A2
-
-
0.059
-
-
1.499
b
0.008
-
0.012
0.203
-
0.305
C
0.007
-
0.010
0.178
-
0.254
D
0.337
0.341
0.344
8.560
8.661
8.738
E
0.228
0.236
0.244
5.791
5.994
6.198
e
0.025
BSC
0.635
BSC
E1
0.150
0.154
0.157
3.810
3.912
3.988
L
0.016
0.025
0.050
0.406
0.635
1.270
L1
θ°
0.041 BSC
0
-
1.041 BSC
8
16-channel 16-bit PWM Constant Current LED Driver
0
-
8
Version : A.004
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Page 21
DM634
Package Outline Dimension
DM634-SOP
DIMENSIONS IN INCH
SYMBOLS
DIMENSIONS IN MM
A
-
-
0.104
-
-
2.642
A1
0.004
-
-
0.102
-
-
b
0.016 BSC
0.406 BSC
D
0.612
0.618
0.624
15.545
15.697
15.850
E
0.292
0.296
0.299
7.417
7.518
7.595
e
0.05 BSC
1.270 BSC
H
0.405
0.412
0.419
10.287
10.465
10.643
L
0.021
0.031
0.041
0.533
0.787
1.041
θ°
0
4
8
0
4
8
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 22
DM634
Package Outline Dimension
DM634-TSSOP (exposed pad)
61cm
DIMENSIONS IN INCH
SYMBOLS
DIMENSIONS IN MM
A
-
-
0.047
-
-
1.200
A1
0.000
-
0.006
0.000
-
0.150
A2
0.031
0.039
0.041
0.800
1.000
1.050
b
0.007
-
0.012
0.190
-
0.300
D
0.303
0.307
0.311
7.700
7.800
7.900
E1
0.169
0.173
0.177
4.300
4.400
4.500
E
0.252 BSC
6.400 BSC
e
0.0256 BSC
0.650 BSC
L1
0.039 REF
1.000 REF
L
0.018
0.024
0.030
0.450
0.600
0.750
S
0.008
-
-
0.200
-
-
θ°
0
-
8
0
-
8
PAD SIZE
(112×18E)
E2
0.090
-
0.112
2.280
-
2.850
D1
0.146
-
0.182
3.700
-
4.620
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 23
DM634
The products listed herein are designed for ordinary electronic applications, such
as electrical appliances, audio-visual equipment, communications devices and so
on. Hence, it is advisable that the devices should not be used in medical
instruments, surgical implants, aerospace machinery, nuclear power control
systems, disaster/crime-prevention equipment and the like. Misusing those
products may directly or indirectly endanger human life, or cause injury and
property loss.
Silicon Touch Technology, Inc. will not take any responsibilities regarding the
misusage of the products mentioned above. Anyone who purchases any products
described herein with the above-mentioned intention or with such misused
applications should accept full responsibility and indemnify. Silicon Touch
Technology, Inc. and its distributors and all their officers and employees shall
defend jointly and severally against any and all claims and litigation and all
damages, cost and expenses associated with such intention and manipulation.
Silicon Touch Technology, Inc. reserve the right to make changes to their products
or to discontinue any product or service without notice, and advise customers to
obtain the latest version of relevant information to verify, before placing orders,
that information being relied on is current and complete.
16-channel 16-bit PWM Constant Current LED Driver
Version : A.004
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Page 24