IT1401
16-bit Constant Current LED Sink Driver
General Description
Features
IT1401 is a 16-bit constant current LED
z
16-bit constant current output channel.
driver incorporating shift register and data
z
Excellent output current accuracy
<±3%.
latch designed for LEDs and LED displays.
The output current can be set using an
z
Output current adjusted with an external
resistor.
external resistor.
All outputs have virtually the same current
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Constant output current range:5~90mA.
levels. Sixteen regulated current ports are
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Data transfer rate: 25MHz.
designed to provide uniform and constant
z
Maximum output terminal voltage: 17V
current for driving LEDs within a large range
z
5V Supply Voltage.
of VF variations.
z
Internal Power On Reset.
Current Accuracy
Between
Channels
<±3%
Between ICs
<±6%
Output Current
5mA~60mA
Pin Configurations
(TOP VIEW)
IT1401
16-bit Constant Current LED Sink Driver
Block Diagram
Pin Description
Pin
I/O
Description
NO.
Name
1
GND
2
SDI
I
Serial input data for data shift register
3
CLK
I
Clock input for data shift on rising edge
4
LE
I
5~20
21
22
——————
————————
Ground pin
Serial data is transferred to output latch when LE
is high.The data is latched when LE goes low.
OUT0 ~O U T 1 5
O
Constant current output bit 0
______
OE
I
Output enable, low active
SDO
O
Serial data output to the following next driver IC
Input terminal used to connect an external resistor
23
R-EXT
I
for
setting output current for all channels
24
VDD
I
Voltage supply input
IT1401
16-bit Constant Current LED Sink Driver
Equivalent Circuits of Inputs and Outputs
IT1401
16-bit Constant Current LED Sink Driver
Timing Diagram
IT1401
16-bit Constant Current LED Sink Driver
Absolute Maximum Ratings
Parameter
Symbol
Supply Voltage
Rated Value
Unit
Min.
Max.
VDD
-0.5
6.0
V
Input Voltage
VIN
-0.2
VDD+0.2
V
Output Current
IOUT
60
mA/ch
Output Voltage
VOUT
17
V
Power Dissipation
Pd
Thermal Resistance
Rth(j-a)
Operation Temperature
Topr
Junction Temperature
Storage Temperature
Minimum ESD Rating
-0.2
1
75
-40
Tj
Tstg
HBM
-55
W
o
C/W
85
o
150
o
150
o
2
200
C
C
C
KV
V
1.Stress beyond those listed under “Absolute Maximum Ratings” may cause permanent
damage to the device. These are stress ratings, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications
is not implied. Exposure to absolute maximum rating conditions for extended periods may
affect device reliability.
2. Device is ESD sensitive. Handling precaution recommended. The Human Body model is a
100pF capacitor discharged through a 1.5kΩ resistor into each pin.
MM
IT1401
16-bit Constant Current LED Sink Driver
Electrical Characteristics
Parameter
Supply Voltage
Range
Output Voltage
Output Current
Symbol
Conditions
Min.
Typ.
Max.
Unit
VDD
-
4.5
5
5.5
V
VOUT
-
-
-
17
V
DC Output Channel
5
IOUT
60
SDO=high
-1
SDO=low
Input Voltage
ViH
1
o
o
o
o
Ta=-40 C ~85 C
0.7VDD
VDD
0.3*VDD
ViL
Ta=-40 C ~85 C
0
Output
VOH
IOH=-1.0mA
4.6
Voltage(SDO)
VOL
IOL=1.0mA
0.4
IOH
VOUT=17.0V
1
Output Leakage
Current
Output Current1
IOUT1
Current Skew
dIOUT1
Output Current2
IOUT2
Current Skew
dIOUT2
Output Current vs.
Output Voltage
%/dVDS
VDS=0.8V,
REXT=1.65kΩ
VDS=0.5V,
REXT=3.3kΩ
Output Current vs.
Supply Voltage
%/dVDD
±3
VDS within 1.0V and
3.0V
VDD within 4.5V and
5.5V
Regulation
V
µA
%
mA
21
IOUT=21mA
V
mA
42
IOUT=42mA
Regulation
mA
±3
%
±0.1
%/V
±0.1
%/V
Pull-up Resistor
RIN(up)
______
OE
500
KΩ
Pull-down Resistor
RIN(dn)
LE
500
KΩ
Supply Current
(OFF)
Supply Current
(ON)
REXT=OPEN,
IDD(off)1
__________
IDD(off)2
__________
IDD(off)3
__________
OUT0 ~ OUT15 =OFF
REXT=3.3kΩ,
OUT0 ~ OUT15 =OFF
REXT=1.65kΩ,
OUT0 ~ OUT15 =OFF
REXT=3.3kΩ,
IDD(on)1
__________
IDD(on)2
__________
OUT0 ~ OUT15 =ON
REXT=1.65kΩ,
OUT0 ~ OUT15 =ON
8.1
8.4
8.9
8.4
8.9
mA
IT1401
16-bit Constant Current LED Sink Driver
Switching Characteristics
Symb
Characteristic
ol
Condition
Values
Min.
Typ.
Max.
Unit
CLK − OUTn
tpLH1
60
100
nS
LE − OUTn
tpLH2
50
100
nS
OE − OUTn
tpLH3
50
100
nS
CLK − SDO
tpLH
CLK − OUTn
tpHL1
LE − OUTn
tpHL2
OEB − OUTn
tpHL3
CLK − SDO
tpLH
CLK
tw(CLK)
20
nS
LE
tw(L)
20
nS
OE ( Iout =< 25mA)
tw(OE)
50
nS
Hold time for LE
th(L)
5
nS
Setup time for LE
tsu(L)
5
nS
Output Rise Time
tor
70
200
nS
Output Fall Time
tof
40
120
nS
Maximum CLK rise time
tr
500
nS
Maximum CLK fall time
tf
500
nS
Propagation Delay
(“L” to “H”)
Propagation Delay
(“H” to “L”)
Pulse Width
______
VDD=5.0V
nS
15
VDS=0.8V
60
150
nS
50
150
nS
RL=52Ω
50
150
nS
CL=10pF
15
VIH= VDD
VIL=GND
Rext=1.2KΩ
VL=4.0V
Test Circuit for Switching Characteristics
nS
IT1401
16-bit Constant Current LED Sink Driver
Timing Waveform
IT1401
16-bit Constant Current LED Sink Driver
Application Information
Constant Current
To design LED displays, IT1401 provides nearly no variations in current from channel to
channel and from IC to IC. This can be achieved by:
1) The maximum current variation between channels is less than ±3%, and that
between ICs is less than ±6%.
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 performs as a perfection of load
regulation.
70
60
Io u t(m A )
50
40
30
20
10
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 2.5
Vds(V)
IT1401
16-bit Constant Current LED Sink Driver
Adjusting Output Current
The output current of each channel (IOUT) is set by an external resistor, Rext. The
relationship between IOUT and Rext is shown in the following figure.
Resistance of the external resistor, Rext, in Ω
Also, the output current in milliamps can be calculated from the equation:
IOUT is (620/Rext)×120, approximately,
Where Rext, in Ω, is the resistance of the external resistor connected to R-EXT terminal.
The magnitude of current (as a function of Rext) is around 40mA at 1.65kΩ and 20mA at
3.3kΩ.
IT1401
16-bit Constant Current LED Sink Driver
Package Power Dissipation(PD)
This 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)=(IDD×VDD)+( IOUT×Duty×VDs×16). 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)]-(IDD×VDD)}/ VDs/Duty/16, where Tj=150oC.
Load Supply Voltage(VLED)
This device is operating with the VDS of 1.0V to 1.2V with LED forward voltage(VF) of 1.2V to
4.0V. If VDS be higher enough to make package power dissipation increased. It is
recommended to use lowest load supply voltage or to set any serials dropping voltage as
following figures.
VDS=VLED-VF-VDROP
IT1401
16-bit Constant Current LED Sink Driver
IT1401(SOP24-300) Outline Drawing
IT1401(SSOP24-150) Outline Drawing