DM621 - Silicon Touch Technology Inc.

DM621
Version
: A.001
Issue Date : 2007/11/26
File Name : SP-DM621-A.001.doc
Total Pages : 23
12-CHANNELS PRE-PROGRAMMABLE
CONSTANT CURRENT LED DRIVER
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
點晶科技股份有限公司
DM621
SILICON TOUCH TECHNOLOGY INC.
DM621
12-CHANNELS PRE-PROGRAMMABLE
CONSTANT CURRENT LED DRIVER
General Description
The DM621 is an innovative LED driver that integrates a new data transmit interface to
accomplish 2-wires control for lighting applications. By the combination of SIN and
DCK, DM621 could be pre-programmed to set the operating modes that involve GCK
frequency division, PWM grayscale selection, inverse IOUT PWM signal, and GCK
frequency selection. DM621 also provides the auto-latch function and incorporates a
particular PWM method (AS-PWM). The IOUT waveform is averagely divided into 16
sections in order to reduce the flickers and enhance the visual refresh rate. The DM621
could also be constructed as a PWM controller for LED drivers. In this case, resistors
must be connected at output pins to achieve this function (Fig.18).
This chip incorporates 4x3-channel constant current circuitry with current value set by
3 external resistors and 256/1024/4096/16384 gray scale PWM function unit. Each
channel provides a maximum current of 90mA. The maximum output sustaining voltage
of 28V would make more serial LEDs possible. And DM621 also integrates an internal
regulator to make power supply voltage up to 18V. Meanwhile, retiming of DCKO and
SOUT is advantageous in the LED decorating and long-cascade applications.
Features
z
4 x 3(R/G/B) Output Channels
z
8/10/12/14-bits PWM grayscale Control
z
Maximum Clock Frequency: 20MHz
z
Constant Current Output: 5mA to 90mA
z
Maximum Output Sustaining voltage: 28V
z
Power Supply Voltage: 5V to 18V
z
Average Separated IOUT PWM Waveform
z
Auto-latch Function
z
Retiming of DCKO and SOUT for long cascade applications
z
Serial Shift-In Architecture for Data of Grayscale, frequency Division and PWM bit number
z
Incorporating internal GCK oscillator 12MHz (Refresh rate = 46.8KHz @ 8-bits PWM)
z
Package: TSSOP24 (with thermal pad), QFN20 (with thermal pad)
z
Constant Current Matching:
Chip-to-Chip:
± 6.0% (max)
Bit-to-Bit:
± 4.0% (max)
12-Channels Pre-programmable
Constant Current LED Driver
(Ta = 25°C、VDD = 12V)
Version:A.001
Page 1
點晶科技股份有限公司
DM621
SILICON TOUCH TECHNOLOGY INC.
Block Diagram
Figure 1. Functional Schematic of Whole Chip
The schematic of DM621 comprises of several fundamental units as shown in Figure1.
The grayscale data and command data, transferred according to the synchronous clock
DCK, are input into the SIN pin of DM621. Meanwhile, the combination of DCK and SIN
data could produce the control signal to switch these two modes and achieve the
auto-latch function. The Retiming block is advised to rearrange the timing of DCKO and
SOUT in order to realize the Auto-Latch function and improve the ability of long cascade.
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
Page 2
點晶科技股份有限公司
DM621
SILICON TOUCH TECHNOLOGY INC.
Pin Description
PIN NAME
FUNCTION
PIN No.
VDD
Power supply terminal
QFN20:1 ,TSSOP24:23
DCK
Synchronous clock input for serial data.
The input data of SIN is transferred at rising
edges of DCK. It also could be used as GCK.
QFN20:11 ,TSSOP24:11
Synchronous clock output
QFN20:12 ,TSSOP24:12
Driver ground terminal
DCKO
SIN
Serial input for grayscale data
QFN20: Thermal Pad
TSSOP24:10,15,22,24
QFN20:13 ,TSSOP24:13
SOUT
Serial output for grayscale data
QFN20:14 ,TSSOP24:14
VSS_DR
REXT_R
REXT_G
REXT_B
External resistor connected between REXT
and GND for driver current setting.
IOUT_R [3:0]
IOUT_G [3:0]
LED driver outputs
IOUT_B [3:0]
QFN20:2 ,TSSOP24:1
QFN20:3 ,TSSOP24:2
QFN20:4 ,TSSOP24:3
QFN20:5,8,15,18
TSSOP24:4,7,16,19
QFN20:6,9,16,19
TSSOP24:5,8,17,20
QFN20:7,10,17,20
TSSOP24:6,9,18,21
Pin Configuration (Top View)
Figure 2. The Package of QFN20
12-Channels Pre-programmable
Constant Current LED Driver
Figure 3. The Package of TSSOP24
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
Equivalent Circuit of Inputs and Outputs
1. DCK, SIN terminals
VDD
INPUT
GND
2. DCKO, SOUT terminals
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
Page 4
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DM621
SILICON TOUCH TECHNOLOGY INC.
Maximum Ratings (Ta = 25°C, Tj(max) = 150°C)
CHARACTERISTIC
SYMBOL
RATING
UNIT
Supply Voltage
VDD
18
V
Input Voltage
VIN
5
V
Output Current
IOUT
90
mA
Output Voltage
VOUT
28
V
DCK Frequency
FDCK
20
MHz
IGND Terminal Current
IGND
750
mA
3.1 (QFN20: Ta=25°C)
Power Dissipation
PD
Thermal Resistance
Rth(j-a)
40.21 (QFN20)
45 (TSSOP24 exposed pad)
°C/W
Operating Temperature
Topr
85
°C
Storage Temperature
Tstg
150
°C
2.78 ( TSSOP24 exposed pad: Ta=25°C)
W
Recommended Operating Condition
CHARACTERISTIC
SYMBOL
CONDITION
MIN.
TYP.
MAX.
UNIT
Supply Voltage
VDD
⎯
5
⎯
18
V
Output Voltage
VOUT
⎯
⎯
⎯
28
V
Operating Temperature
TOPR
⎯
-40
⎯
85
℃
IOUT
OUT
5
⎯
90
mA
IOH
VOH =VDD – 0.2V
⎯
⎯
2.5
mA
IOL
VOL= 0.2V
⎯
⎯
-2
mA
4
⎯
5
0
⎯
1
Output Current
Input Voltage
VIH
VIL
12-Channels Pre-programmable
Constant Current LED Driver
VDD=5V~17V
Version:A.001
V
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DM621
SILICON TOUCH TECHNOLOGY INC.
Electrical Characteristics (VDD = 12 V, Ta = 25°C unless otherwise noted)
CHARACTERISTIC
SYMBOL
CONDITION
MIN.
TYP.
MAX.
Input Voltage “H” Level
VIH
⎯
3
⎯
5
Input Voltage “L” Level
VIL
⎯
0
⎯
1
Output Leakage Current
IOL
VOUT = 28 V
⎯
⎯
1.0
uA
Output Current Skew
(Bit-Bit)
Output Current Skew
(Chip-Chip)
UNIT
V
ΔIout
VOUT = 1V
IOUT=25mA
⎯
⎯
±4
%
ΔIout
VOUT = 1V
IOUT=25mA
⎯
⎯
±6
%
IOUT=25mA
⎯
0.1
0.5
%/V
Vout = 1.2V ~ 5.0V
Output Voltage Regulation
I
Supply Voltage Regulation
% / VREF
VDD = 5V ~18V
⎯
0.5
1
%/V
fosc
VDD = 5V ~18V
9.8
12.3
14.75
MHz
REXT = OPEN, all outputs off
⎯
1.7
⎯
REXT = 2KΩ (Iout=60mA),
all outputs off
⎯
13.3
⎯
REXT = 2KΩ (Iout=60mA),
all outputs on
⎯
13.3
⎯
MIN.
TYP.
MAX.
UNIT
Internal Oscillator Frequency
Supply Current “OFF”
Supply Current “ON”
Idd (off)
Idd (on)
(% / Vout)
mA
Switching Characteristics (Ta = 25 °C unless otherwise noted)
CHARACTERISTIC
SYMBOL
SOUT Propagation Delay
(“L” to “H”)
DCK to SOUT
SOUT Propagation Delay
(“H” to “L”)
DCKO Propagation Delay
(“L” to “H”)
DCK to DCKO
DCKO Propagation Delay
(“H” to “L”)
tPLH(sout)
⎯
25
⎯
ns
tPHL(sout)
⎯
20
⎯
ns
⎯
12
⎯
ns
⎯
10
⎯
ns
⎯
20
⎯
ns
⎯
20
⎯
ns
tPLH(DCKO)
tPHL(DCKO)
Output Current Rise Time
tor
Output Current Fall Time
tof
CONDITION
VDD=12V
VIH=5V
VIL=GND
Rext=2.1KΩ
VLED=5V
RL=62Ω
CL=13pF
SIN Setup Time
tsetup
⎯
1
⎯
ns
SIN Hold Time
thold
⎯
3
⎯
ns
Command Delay Time
tCMD
⎯
20
⎯
ns
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
Figure 4. Measurement Architecture
Figure 5. The Definitions of Parameters
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
Typical Performance Characteristics (refer to Figure.4)
IOUT=25mA
DCK
IOUT=60mA
DCK
DCKO
DCKO
DCK
DCK
SOUT
SOUT
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
DCK
DCK
SIN
SIN
DCKO
DCKO
SOUT
SOUT
DCK
DCKO
SIN
DCKO
SOUT
SOUT
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
Serial Shift-In Luminance Data (Shift Register Architecture)
Figure 6. Serial Shift-In Luminance Data Structure
This serial shift (shift register) architecture follows a FIFO (first-in first-out) format.
The MSB (Most Significant Bit) data is the first data bit that shift into the driver.
The LSB (Least Significant Bit) data is the last bit in the data sequence.
And the PWM [1:0] command determines the data rate of each channel.
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
Average Separated PWM (AS-PWM) Waveform
The DM621 incorporates a new PWM method, hence the IOUT waveform demonstrates
a very different characteristic compared to conventional PWM method. The IOUT
waveform is averagely divided into 16 sections in a whole PWM period at each PWM mode.
Furthermore, this progressive algorithm could efficiently reduce flickers and enhance the
visual refresh rate.
Figure 7. The Progressive PWM Method (1)
Figure 8. The Progressive PWM Method (2)
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
Command/Data Switching and Auto-latch Function
Figure 9(a). The Command/Data Method
Figure 9(b). The Auto-latch Method
DM621 combines the signals of DCK and SIN to realize the Command/Data switching
and Auto-latch function. When the area that DCK keeps at high level includes two
positive edges of SIN, DM621 would switch automatically to the command data mode,
illustrated in Figure 9(a). At this time, 8-bits command data could be transmitted to set
the operating condition adequate for different applications. After command data
transmission is accomplished, a latch signal would have to be executed by Auto-latch
function. And this chip would latch command data into internal registers and return to the
grayscale data mode as a latch instruction is executed. The Auto-latch function is
realized by this method that the area that DCK keeps at high level includes only one
positive edge of SIN, illustrated in Figure 9(b). Note that the latch signal of command
data and grayscale data could be completed according to the same Auto-latch process.
Both Command/Data switching and Auto-latch process would produce signals to control
synchronously every serial DM621s. Therefore, each serial DM621 would enter the
command mode and execute a latch instruction simultaneously. And DM621 also
supports the internal synchronous clock for grayscale display. These characteristics
would make great grayscale display possible. In this specific design, the smallest
limitation of tCMD, the time from the positive edge of DCK to the first positive edge of SIN,
is 20ns in order to promise the correct command and grayscale data could be received.
Note that command data have to be transmitted to pre-programmed DM621s when the
system is restarted because there are no EEPROM in this chip to save the command data
and the grayscale data.
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
Command Data
COMMAND
FUNCTION
8/10/12/14-bits PWM mode selection
PWM [1:0] = 2’b00: 8-bits PWM count
PWM [1:0] = 2’b01: 10-bits PWM count
PWM [1:0] = 2’b10: 12-bits PWM count
PWM [1:0] = 2’b11: 14-bits PWM count
GCK frequency division selection
FREQ [1:0] = 2’b00: GCK=CLK
FREQ [1:0] = 2’b01: GCK=CLK/2
FREQ [1:0] = 2’b10: GCK=CLK/4
FREQ [1:0] = 2’b11: GCK=CLK/8
GCK source selection
OSC =1’b0: Internal oscillator (12MHz)
OSC =1’b1: External DCK signal
Inverse PWM data selection
POLAR =1’b0: Normal PWM signal
POLAR =1’b1: Inverse PWM signal
Command Data Error Code (avoid interference)
DEC [1:0] =2’b11: Command data is enable
DEC [1:0] =others: Command data is disable
PWM [1:0]
FREQ [1:0]
OSC
POLAR
DEC [1:0]
Timing Diagram
By the combination of DCK and SIN data, DM621 could produce the internal CMD and
LATCH signal to control the system automatically.
(*Note: CMD and LATCH are both the internal control signals)
(**Note: CMD=”1” Æ command data mode, CMD=”0” Æ grayscale data mode)
Command Data:
Figure 10. The timing diagram of command data
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
When there is two positive edges of SIN at DCK=”H”, DM621 produces CMD signal to
switch to command data mode. Then users have to input 8bits command data to set the
DM621 operating conditions described above. DM621 will latch command data into
internal registers by incorporating one positive edge of SIN at DCK=”H”. Meanwhile, the
CMD signal will return to zero.
Grayscale Data:
Figure 11. The timing diagram of grayscale data
According to the operating condition set at command mode, DM621 receives the 8bits/
10bits/12bits/14bits PWM grayscale data. DM621 will latch grayscale data by
incorporating one positive edges of SIN at DCK=”H”. Figure 11 is an illustration of 10-bits
PWM grayscale data when the command data PWM [1:0]=2’b01.
Complete Data Transference:
Figure 12. Detailed timing diagram of data transference
This is an illustration of the complete data transference of DM621. The command data
sets the condition is 10-bits PWM mode, no GCK frequency division, no inverse PWM
signal and the internal oscillator is utilized.
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
Figure 13. Timing diagram of serial data transference
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
Driver Output Current
Constant-current value of each output channel is set by an external resistor, which is
connected between the REXT pin and GND. Varying the resistor value can adjust the
current scale ranging from 5mA to 90mA. The reference voltage (Vrext) of REXT
terminal is approximately 1.23V. The constant current formula is
IOUT (mA) =
Vrext (V )
1.23V
*100 =
*100
Re xt (kΩ)
Re xt (kΩ)
Figure 14.
Figure 15.
12-Channels Pre-programmable
Constant Current LED Driver
IOUT V.S. VOUT curve
IOUT V.S. Rext curve
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
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:
Pd(max)(Watt) =
Tj(junction temperature)(max)(°C)– Ta(ambient temperature)(°C)
Rth(junction-to-air thermal resistance)(°C/Watt)
The relationship between power dissipation and operating temperature can refer to the figure
below:
4
Tj(max)=150 °C
Power Dissipation Pd(W)
3.5
Rth(QFN20)=40.21 °C/Watt
QFN20
3
Rth(TSSOP24)=45 °C/Watt
TSSOP24
2.5
2
1.5
1
0.5
0
0
20
40
60
80
100
120
140
160
Ambient Temperature Ta(℃)
Based on the Pd (max), the maximum allowable voltage of output terminal can be determined by
the following equation:
VoutR × IoutR × DutyR + VoutG × IoutG × DutyG + VoutB × IoutB × DutyB < Pd(max)(W)– VCC(V) × IDD(A)
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
Application Diagram
(1) DCK global connection (Figure 16):
(2) DCK serial connection (Figure 17):
Just connected as the architecture illustrated above, DM621 could automatically
produce the global latch and make serial data possible. The system just needs four lines
(VDD, VSS, SIN, and DCK) to realize the cascade architecture. Please utilize a slower
DCK frequency and increase tCMD to realize a long cascade.
(3) PWM generator (Figure 18):
DM621 could be utilized as a PWM
generator. In this case, DM621 will
output inverse PWM signals by the
POLAR command.
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
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DM621
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(4) Demo board (TSSOP24 PCB available):
Top View
Bottom View
Photo
The length of DCK should be equal to that of SIN as close as possible. Similarly, DCKO and
SOUT should obey this rule in order to avoid the error of timing in long-cascade applications.
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
Package Outline
TSSOP24
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
QFN20 (4mm*4mm)
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
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DM621
SILICON TOUCH TECHNOLOGY INC.
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.
12-Channels Pre-programmable
Constant Current LED Driver
Version:A.001
Page 22