8-Bit LED Driver
CS8818
1 Rev. 1.3
Chiplus reserves the right to change product or specification without notice.
Revision History
Rev. No. History Issue Date
1.0 New issue Sep. 30, 2008
1.1 Update AC data
Modify Rext vs. Iout relation
Dec. 29, 2008
1.2 Modify Rext vs. Iout relation Oct. 8, 2009
1.3 Format modify Oct. 19, 2010
8-Bit LED Driver
CS8818
2 Rev. 1.3
Chiplus reserves the right to change product or specification without notice.
CS8818(CT/AD)
8-Bit Constant Current LED Driver with 3.0V to 5.5V Supply Voltage
Description
The CS8818 is an 8-Bit constant current LED driver IC which is designed for LED displays. The output
current can be adjusted by using an external resistor. All outputs will have the same current drive level which
is crucial in LED display application. This driver has built-in 8-bit constant current outputs, an 8-bit shift
register, and an 8-bit latch circuit. These drivers have been designed by using CMOS process.
Feature
Output current capability: 70mA each output
Constant current range: 5mA to 70mA
For common anode LED application
Power supply voltage range VDD=3.0V to 5.5V
Maximum output drain voltage 7.0V
Serial data transfer rate: 25MHz(Cascade Connection)
Operating temperature range: -40 to 85 degree C
Output current accuracy:
Between Bits : < +-1.5 %
Between ICs: < +-4 %
Product Family
CS8818CT ------- 16SOP(150mil, 1.27mm lead-pitch)
CS8818AD ------- 16SSOP(150mil, 0.635mm lead-pitch)
8-Bit LED Driver
CS8818
3 Rev. 1.3
Chiplus reserves the right to change product or specification without notice.
Pin Assignment
Block Diagram
Truth Table
CLOCK LATCH ENABLE SERIAL-IN
OUT0---OUT3---OUT7 SERIAL-OUT
Positive edge
H L Dn /Dn---/Dn-3---/Dn-7 Dn-7
Positive edge
L L Dn+1 No Change Dn-6
Positive edge
H L Dn+2 /Dn+2---/Dn-1---/Dn-5 Dn-5
Negative edge
X L Dn+3 /Dn+2---/Dn-1---/Dn-5 Dn-5
Negative edge
X H Dn+3 Off Dn-5
8-Bit LED Driver
CS8818
4 Rev. 1.3
Chiplus reserves the right to change product or specification without notice.
Timing Diagram
Note:
1. The latch circuit is a level-latch, not an edge-triggered latch.
2. The latch circuit holds data when LATCH pin low. When the LATCH pin is at high-level, the latch circuit
passes the data from input to output. When ENABLE pin is at low-level, the latched data is transferred to
the output pin OUT0~OUT7. When ENABLE pin is at high-level, the OUT0~OUT7 is turned off regardless
of the latch data.
8-Bit LED Driver
CS8818
5 Rev. 1.3
Chiplus reserves the right to change product or specification without notice.
Pin Description
Pin No.
Pin Name Function
1 GND GND Pin.
2 SERIAL-IN Serial input data pin.
3 CLOCK Clock input terminal for shift register, rising edge trigger.
4 LATCH Data latch input pin. When LATCH=High-level, data is passed to
OUT0~OUT7, when LATCH=Low-level, data is latched.
5~12 OUT0~OUT7 8 constant current output pins to drive common anode LEDs.
13 ENABLE Data output enable pin, when ENABLE=High-level, all OUT0~OUT7 are
turned off, and when ENABLE=Low-level, all OUT0~OUT7 are enabled.
14 SERIAL-OUT Serial data output pin for cascade operation.
15 R-EXT The external resistor connection pin to adjust the output current.
16 VDD 3.0V~5.5V supply voltage pin.
Equivalent Circuits of I/O Pins
8-Bit LED Driver
CS8818
6 Rev. 1.3
Chiplus reserves the right to change product or specification without notice.
Absolute Maximum Ratings
Characteristics Symbol Rating Unit
Supply Voltage VDD +7.0 V
Input Voltage Vin -0.4 to VDD+0.4 V
Output Current Iout +70 mA
Output Voltage Vout -0.5 to 7.0 V
GND Pin Current IGND 560 mA
Clock Frequency fCLK 25 MHz
Power Dissipation Pd CT: 0.86
AD: 0.79 W
Thermal Resistance Rth(j-a) CT: 110.9
AD: 115.4 /W℃
Operating Temperature Top -40 to 85 ℃
Storage Temperature Tstg -55 to 150 ℃
Recommended Operating Condition
Characteristics Symbol Condition Min Typ
Max Unit
Supply Voltage VDD 3.0 5.0
5.5 V
Output Voltage VOUT 7.0 V
Output Current IOUT
IOL
IOH
OUTn
SERIAL-OUT Vol=0.5V
SERIAL-OUT Voh=4.3V
70
2.5
-2.0
mA
Input Voltage VIH
VIL
0.7VDD
-0.3
VDD+0.3
0.3VDD
V
Clock Frequency fCLK VDD=5.0V, Cascade connection
VDD=3.0V, Cascade connection
25
20
MHz
Latch Pulse Width twLatch VDD=4.5V ~ 5.5V 15 ns
Clock Pulse Width twCLOCK
VDD=4.5V ~ 5.5V 15 ns
Set-Up Time for Data tSETUP3
VDD=4.5V ~ 5.5V 20 ns
Set-Up Time for Latch tSETUP2
VDD=4.5V ~ 5.5V 15 ns
Set-Up Time for Clock tSETUP1
VDD=4.5V ~ 5.5V 20 ns
Hold Time for Data tHOLD VDD=4.5V ~ 5.5V 20 ns
8-Bit LED Driver
CS8818
7 Rev. 1.3
Chiplus reserves the right to change product or specification without notice.
Electrical Characteristics
(Temp=25 )℃
Characteristics Symbol Condition Min
Typ
Max
Unit
Supply Voltage VDD 3.0
5.0
5.5
V
Output Current IOUT1
IOUT2
VOUT=1.0V, VDD=5.0V,
R-EXT=700Ohm
VOUT=1.0V, VDD=5.0V,
R-EXT=3450Ohm
24.6
5.0
mA
Output Current Error
Between Bits
IOUT1
IOUT2
VOUT=1.0V, R-EXT=700Ohm
VOUT=1.0V, R-EXT=3450Ohm
-1.5
-1.5
+1.5
+1.5
%
Output Current Error
Between Chips
ILO3
IOL4
VOUT=1.0V, R-EXT=700Ohm
VOUT=1.0V, R-EXT=3450Ohm
-4
-4
+4
+4
%
Output Leakage
Current
ILEAK VOUT=5.0V 1 uA
Input Voltage Low VIL VDD=5.0V 0 1.5
V
Input Voltage High VIH VDD=5.0V 3.5
5.0
V
Output Voltage SOUT VOL
VOH
IOL=+1.5mA, VDD=5.0V
IOH=-1.5mA, VDD=5.0V
4.3
0.5
V
Pull-Up Resistor R(UP) ENABLE Pin 202
KOhm
Pull-Down Resistor R(DOWN)
LATCH Pin 128
KOhm
Supply Current(Off)
(OUT0~OUT7 Off)
IDD(Off) VDD=5.0V, R-EXT=700Ohm
VDD=5.0V, R-EXT=3450Ohm
VDD=5.0V, R-EXT=Open
3.7
0.9
0.2
mA
Supply Current(On)
(OUT0~OUT7 On)
IDD(On) VDD=5.0V, R-EXT=700Ohm
VDD=5.0V, R-EXT=3450Ohm
3.7
0.9
mA
8-Bit LED Driver
CS8818
8 Rev. 1.3
Chiplus reserves the right to change product or specification without notice.
Switching Characteristics
(Temp=25 ,℃ VDD=5V, VIH=3.5V, VIL=0V, R-EXT=860Ohm)
Characteristics Symbol Condition Min
Typ
Max
Unit
tpLH1 CLK-OUTn, LATCH=“H”, ENABLE=“L” 40 60 ns
tpLH2 LATCH-OUTn, ENABLE=“L” 35 50 ns
tpLH3 ENABLE-OUTn, LATCH=“H” 20 30 ns
tpLH CLK-SERIAL OUT 30 40 ns
tpHL1 CLK-OUTn, LATCH=“H”, ENABLE=“L” 80 125
ns
tpHL2 LATCH-OUTn, ENABLE=“L” 75 120
ns
tpHL3 ENABLE-OUTn, LATCH=“H” 130
180
ns
Propagation Delay
tpHL CLK-SERIAL OUT 30 40 ns
tW(CLOCK) CLOCK 15 ns
tW(LATCH) LATCH 10 ns
Pulse Width
tW(ENABLE)
ENABLE 180
ns
Output Rise Time tor Voltage waveform 10%~90% 30 75 150
ns
Output Fall Time tof Voltage waveform 90%~10% 10 20 40 ns
Max CLK Rise Time
tr 480
ns
Max CLK Fall Time tf 480
ns
Test Circuit
(RL=162Ohm, CL=10pf, VL=5.0V)
8-Bit LED Driver
CS8818
9 Rev. 1.3
Chiplus reserves the right to change product or specification without notice.
Timing Waveform
8-Bit LED Driver
CS8818
10 Rev. 1.3
Chiplus reserves the right to change product or specification without notice.
Output Current vs. R-EXT (VDD=5V)
Iout = (1.22/Rext) x 14.62
CS8818 Rext vs. Iout Curve
0
10
20
30
40
50
60
70
80
90
0 1000 2000 3000 4000 5000 6000 7000
Rext (ohm)
Iout (mA)
CS8818 Vds vs. Iout Curve
0
10
20
30
40
50
60
70
80
0 0.5 1 1.5 2 2.5 3 3.5
Vds
Iout(mA)
1155ohm 691ohm 345ohm 247ohm
8-Bit LED Driver
CS8818
11 Rev. 1.3
Chiplus reserves the right to change product or specification without notice.
Typical Application
LED supply voltage is set-up by following equation:
VLED = VCE + Vf + Vo
To prevent too much power dissipated by driver due to the higher VLED, an additional R can be
introduced to reduce the Vo when output is consuming current.
R = ( VLED – VCE – Vf – Vo min)/( Io max * Bit max)
Order Information
Part No. Package Type Lead Pitch
CS8818CT 16SOP(150mil) 1.27mm
CS8818AD 16SSOP(150mil) 0.635mm
8-Bit LED Driver
CS8818
12 Rev. 1.3
Chiplus reserves the right to change product or specification without notice.
8-Bit LED Driver
CS8818
13 Rev. 1.3
Chiplus reserves the right to change product or specification without notice.
