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PDF SCT2027 Data sheet ( Hoja de datos )
| Número de pieza | SCT2027 | |
| Descripción | 16-bit Constant-Current LED Driver | |
| Fabricantes | StarChips | |
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StarChips
Technology
SCT2027 V01_03; Jun/13
16-bit Constant-Current LED Driver with ModelessTM Error Detection
Product Description
The SCT2027 is a serial interfaced 16 bit constant current sinker with error detection designed for LED
displays and LED lighting applications. In applications, an external resistor is used to adjust the full scale
output current from 5mA up to 90mA. The serial data are shifted into 16 bit shift register by clock signal.
Input data appear at the SDO output 16 clock cycles later to allow cascading of multiple SCT2027s. The
latch enable input, LA/, loads the 16 bits data of shift register into a 16 bit latch to determine which LEDs
are on and off. The output enable input, OE/ gates all 16 outputs on and off, and is fast enough to be
used as PWM input for the LED intensity control.
The SCT2027 combines the SCT2024/6 with ModelessTM technique to detect open load and
shorted load errors while driving the LEDs without mode switching*. With the pin to pin compatible
design, all the LED display or lighting systems can be upgraded to perform the on the fly error detection
functions simply by replacing all the SCT2024/6s with SCT2027s directly. Also, by the ModelessTM
technique, the software and hardware works well without reworks between systems of the SCT2024/6
and SCT2027.
During operations, the SCT2027 takes only 200ns to generate error status codes after the rising edge of
LA/. The error status codes saved in the shift register can be shifted out via SDO bit by bit along with
CLK, at the same time the new serial data can be shifted into SCT2027 via SDI. By comparing the
display data with error status codes, the system control unit can read the error status to determine
whether or not the LEDs are properly lit. If the input display signals are inconsistent with the
corresponding output status code, the corresponding LEDs are determined to have been stuck open or
short.
Since the high clock frequency can reach up to 25MHz, the SCT2027 satisfies the system requirements
of high volume data transmission to control the LED display. The SCT2027 also guarantees each output
endures up to 7V voltage stress, thus each output can drive multiple LEDs. The ModelessTM SCT2027
combines the error detection mechanism with display signals; hence the control unit does not need to
switch between different modes, and therefore both the hardware costs and the control complexity can
be reduced. In addition, the LED error status codes can be read in real time, and hence the fault status
of the faulty LEDs can be discovered sooner.
*Starchips’ patent protection.
1 page  
16-bit Constant-Current LED Driver with ModelessTM Error Detection SCT2027
Selector Guide
Part
SCT2110
SCT2168
SCT2169
SCT2167
SCT2210
SCT2026
SCT2027
SCT2024
Number of
Outputs
8
8
8
8
16
16
16
16
Max Output
Current (mA)
180
120
120
60
120
90
90
60
Min PWM Pulse
Width (ns)
100
120
120
180
50
120
120
180
Supply
Voltage (V)
5
3.3/5
3.3/5
3.3/5
5
3.3/5
3.3/5
3.3/5
Error Detection
NA
NA
Yes
NA
NA
NA
Yes
NA
Ordering Information
Part
SCT2027CSSG
SCT2027CSTG
SCT2027CSOG
Marking
SCT2027CSSG
SCT2027CSTG
SCT2027CSOG
Package
Green SSOP24
Green SSOP24 1
Green SOP24
StarChips Technology, Inc.
4F, No.5, Technology Rd., Science Based Industrial Park, Hsin Chu, Taiwan, R.O.C.
Tel : +886 3 577 5767 Ext.555
Fax: +886 3 577 6575
E mail : [email protected]
Unit per reel(pcs)
2500
2000
1000
Page 5 of 18
5 Page 
16-bit Constant-Current LED Driver with ModelessTM Error Detection SCT2027
Adjusting Output Current
The SCT2027’s output current (IOUT) are set by one external resistor at pin REXT. The output current
IOUT versus resistance of REXT is shown as the following figure.
SCT2027 IOUT vs. REXT
100
80
1V<VOUT<4V
60
40
20
0
0 0.5 1 1.5 2 2.5 3 3.5 4
REXT(KΩ)
According to SCT20277’ I V curve, the output voltage should be larger than 1V to get 60 mA constant
current. By applying proper output voltage, the SCT2027’ output current set by an external resistor is
approximate to: IOUT = 30(630 / REXT) (mA) (chip skew < ±4%). Thus the output current is set to be
about 21mA at REXT = 900U.
Output Characteristics
The current characteristic of output curve is flat. The output current can be kept constant regardless of
the variations of LED forward voltage when VOUT > VDO(Drop Out voltage). The relationship between IOUT
and VOUT is shown below. The output voltage should be kept as low as possible to prevent the SCT2027
from being overheated.
SCT2027 IOUT vs. VOUT@VDD=5V, TA=25°C
100
80
60
40
20
0
0
Drop-out voltage is current dependent, e.g., VDO=0.5V@IOUT=20mA
1 VOU2T(V) 3
4
Page 11 of 18
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet SCT2027.PDF ] | |
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