IS31FL3743B
18×11 DOTS MATRIX LED DRIVER WITH 12MHZ SPI
May 2019
GENERAL DESCRIPTION
FEATURES
The IS31FL3743B is a general purpose 18×n (n=1~11)
LED Matrix programmed via 12MHz SPI interface.
Each LED can be dimmed individually with 8-bit PWM
data and 8-bit DC scaling data which allowing 256
steps of linear PWM dimming and 256 steps of DC
current adjustable level.
Additionally each LED open state can be detected,
IS31FL3743B store the open information in OpenRegisters. The Open Registers allowing MCU to read
out via SPI, inform MCU whether there are LEDs open
or short LEDs.
The IS31FL3743B operates from 2.7V to 5.5V and
features a very low shutdown and operational current.
IS31FL3743B is available in UQFN-40 (5mm×5mm)
package. It operates from 2.7V to 5.5V over the
temperature range of -40°C to +125°C.
Supply voltage range: 2.7V to 5.5V
18 current sinks (Maximum)
Support 18×n (n=1~11) LED matrix configurations
Individual 256 PWM control steps
Individual 256 DC current steps
Global 256 DC current steps
SDB rising edge reset SPI module
29kHz PWM frequency
12MHz SPI interface
State lookup registers
Individual open and short error detect function
180 degree phase delay operation to reduce
power noise
De-ghost
Cascade for synchronization of chips
UQFN-40 (5mm×5mm) package
APPLICATIONS
Hand-held devices for LED display
Gaming device (Keyboard, Mouse etc.)
LED in white goods application
TYPICAL APPLICATION CIRCUIT
5V
1 F 0.1 F 5
5V
1 F
22
PVCC
VCC
SW11
SW10
11
40
SW1 SW2 SW3 SW4 SW5 SW6 SW7 SW8 SW9 SW10 SW11
0.1 F
51R
28
27
25
Micro
Controller
24
26
MOSI
SCK
SW2
SW1
MISO
SDB
CS18
20R
6
CS17
20R
CS16
CS
IS31FL3743B
CS18
CS17
100k
4
12
13
51R
CS3
0.1 F
20R
30
29
10k
23
CS2
SYNC
ISET
GND
CS2
CS1
PGND
38
39
20R
CS1
16
Figure 1 Typical Application Circuit: 66 RGBs
Note 1: For the mobile applications the IC should be placed far away from the mobile antenna in order to prevent the EMI.
Note 2: PVCC and VCC should use same power supply to avoid the additional ISD, it is OK to use PVCC=VCC=5V and VIO=3.3V.
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IS31FL3743B
TYPICAL APPLICATION CIRCUIT (CONTINUED)
5V
1 F 0.1 F 5
5V
1 F
22
PVCC
VCC
SW11
SW10
11
40
SW1 SW2 SW3 SW4 SW5 SW6 SW7 SW8 SW9 SW10 SW11
0.1 F
20R
28
27
25
Micro
Controller
24
26
MOSI
SCK
SW2
SW1
20R
6
MISO
SDB
CS17
20R
CS16
CS
IS31FL3743B
CS18
CS17
100k
4
CS18
12
13
20R
CS3
0.1 F
20R
30
29
CS2
SYNC
ISET
CS2
CS1
38
39
20R
CS1
10k
23
GND
PGND
16
Figure 2 Typical Application Circuit: 198 Mono Color LEDs
Figure 2 Typical Application Circuit (Eight Parts Synchronization-Work)
Note 3: The 20R between LED and IC is only for thermal reduction, for mono red LED, if PVCC=VCC=3.3V, don’t need these resistors.
Note 4: One part is configured as master mode, all the other 7 parts configured as slave mode (slaves should be configured as slave before
master set as master). Work as master mode or slave mode specified by Configuration Register (SYNC bits, register 25h, Page 2). Master part
output master clock, and all the other parts which work as slave input this master clock.
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IS31FL3743B
PIN CONFIGURATION
Package
Pin Configuration (Top View)
UQFN-40
PIN DESCRIPTION
No.
Pin
Description
1~4
SW8,SW6,SW4,SW2
Power SW.
5
PVCC
Power for current source SW.
6~11
SW1,SW3,SW5,
SW7,SW9,SW11
Power SW.
12~15
CS18~CS15
Current sink pin for LED matrix.
16
PGND
Power GND.
17~21
CS14~CS10
Current sink pin for LED matrix.
22
VCC
Analog and digital circuits.
23
GND
Analog GND.
24
MISO
MISO of SPI.
25
CS
CS of SPI.
26
SDB
Shutdown pin.
27
SCK
SPI clock.
28
MOSI
SPI input data.
29
ISET
Set the maximum IOUT current.
30
SYNC
Synchronization.
31~39
CS9~CS1
Current sink pin for LED matrix.
40
SW10
Power SW.
Thermal Pad
Need to connect to GND.
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IS31FL3743B
ORDERING INFORMATION
Industrial Range: -40°C to +125°C
Order Part No.
Package
QTY/Reel
IS31FL3743B-QULS4-TR
UQFN-40, Lead-free
2500
Copyright © 2019 Lumissil Microsystems. All rights reserved. Lumissil Microsystems reserves the right to make changes to this specification and its
products at any time without notice. Lumissil Microsystems assumes no liability arising out of the application or use of any information, products or
services described herein. Customers are advised to obtain the latest version of this device specification before relying on any published information and
before placing orders for products.
Lumissil Microsystems does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can
reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use
in such applications unless Lumissil Microsystems receives written assurance to its satisfaction, that:
a.) the risk of injury or damage has been minimized;
b.) the user assume all such risks; and
c.) potential liability of Lumissil Microsystems is adequately protected under the circumstances
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IS31FL3743B
ABSOLUTE MAXIMUM RATINGS
Supply voltage, VCC
Voltage at any input pin
Maximum junction temperature, TJMAX
Storage temperature range, TSTG
Operating temperature range, TA=TJ
Package thermal resistance, junction to ambient (4 layer standard
test PCB based on JESD 51-2A), θJA
ESD (HBM)
ESD (CDM)
-0.3V ~+6.0V
-0.3V ~ VCC+0.3V
+150°C
-65°C ~+150°C
-40°C ~ +125°C
41.6°C/W
±7kV
±1kV
Note 6: Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress
ratings only and functional operation of the device at these or any other condition 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.
ELECTRICAL CHARACTERISTICS
The following specifications apply for VCC = 3.6V, TA = 25°C, unless otherwise noted.
Symbol
Parameter
Conditions
Min.
Typ.
VCC
Supply voltage
ICC
Quiescent power supply current
ISD
Shutdown current
IOUT
Maximum constant current of
CSx
RISET=10kΩ, GCC=0xFF,
SL=0xFF
ILED
Average current on each LED
ILED = IOUT(PEAK)/Duty(1/11.377)
RISET=10kΩ, GCC=0xFF,
SL=0xFF
3.03
Current switch headroom voltage
SWx
ISWITCH=612mA RISET=10kΩ,
GCC=0xFF, SL=0xFF
550
Current sink headroom voltage
CSx
ISINK=34mA, RISET=10kΩ,
GCC=0xFF, SL=0xFF
450
VHR
tSCAN
Period of scanning
tNOL1
Non-overlap blanking time during
scan, the SWx and CSy are all
off during this time
tNOL2
Delay total time for CS1 to CS
18, during this time, the SWx is
on but CSx is not all turned on
2.7
VSDB=VCC, all LEDs off
1.8
VSDB=0V
1.3
VSDB= VCC, Configuration Register
written “0000 0000
1.3
32.09
34.5
Max.
Unit
5.5
V
mA
μA
36.91
mA
mA
mV
(Note 7)
33
µs
0.83
µs
0.3
µs
Logic Electrical Characteristics (SCK, MISO, MOSI, CS, SDB, SYNC)
VIL
Logic “0” input voltage
VCC=2.7V~5.5V
VIH
Logic “1” input voltage
VCC=2.7V~5.5V
VOH
H level MISO pin output voltage
IOH= -8mA
VOL
L level MISO pin output voltage
IOL= 8mA
VHYS
Input Schmitt trigger hysteresis
VCC=3.6V
IIL
Logic “0” input current
IIH
Logic “1” input current
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Rev. A, 05/13/2019
0.6
2.4
VCC0.4V
0
V
V
VCC
V
0.4
V
0.2
V
SDB=L, VINPUT = L (Note 7)
5
nA
SDB=L, VINPUT = H (Note 7)
5
nA
5
IS31FL3743B
DIGITAL INPUT SPI SWITCHING CHARACTERISTICS (NOTE 7)
Symbol
fC
Parameter
Clock frequency
Min.
Typ.
Max.
Units
12
MHz
tSLCH
CS active set-up time
34
tSHCH
CS not active set-up time
17
ns
tSHSL
CS detect time
167
ns
tCHSH
CS active hold time
34
ns
tCHSL
CS not active hold time
17
ns
tCH
Clock high time
34
ns
tCL
Clock low time
34
ns
tCLCH
Clock rise time
9
ns
tCHCL
Clock fall time
9
ns
tDVCH
Data in set-up time
7
ns
tCHDX
Data in hold time
9
ns
tSHQZ
Output disable time
34
ns
tCLQV
Clock low to output valid
39
ns
tCLQX
Output hold time
tQLQH
Output rise time
17
ns
tQLQH
Output fall time
17
ns
ns
0
ns
Note 7: Guaranteed by design.
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IS31FL3743B
FUNCTIONAL BLOCK DIAGRAM
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IS31FL3743B
DETAILED DESCRIPTION
SPI INTERFACE
ADDRESS AUTO INCREMENT
IS31FL3743B uses a SPI protocol to control the chip’s
function with four wires: CS, SCK, MOSI and MISO.
SPI transfer starts form CS pin from high to low
controlled
by
Master
(Microcontroller),
and
IS31FL3743B latches data when clock rising.
To write multiple bytes of data into IS31FL3743B, load
the address of the data register that the first data byte
is intended for. During the 8th rising edge of receiving
the data byte, the internal address pointer will
increment by one. The next data byte sent to
IS31FL3743B will be placed in the new address, and
so on. The auto increment of the address will continue
as long as data continues to be written to
IS31FL3743B (Figure 7).
SPI data format is 8-bit length. The first command byte
composite of 1-bit R/W bit, 3-bit chip ID bit and 4-bit
page bit. The command byte must be sent first, and is
followed by register address byte then the register
data. If the R/W bit is “0”, it will be write operation and
Master (Micro-controller) can write the register data
into the register.
The maximum SCK
IS31FL3743B is 12MHz.
frequency
supported
Table 1 SPI Command Byte
Name
R/W
ID bit
Page No.
Bit
D7
D6:D4
D3:D0
Value
0: Write
1: Read
101
0x00: Point to Page 0
0x01: Point to Page 1
0x02: Point to Page 2
in
READING OPERATION
Page 0~Page 2 registers can be read by SPI.
To read the registers of Page 0 thru Page 2, The D7
of the Command Byte need to be set to “1” and select
the page number. If read one register, as shown in
Figure 8, read the MISO data after sending the
command byte and register address. If read more
registers, as shown in Figure 9, the register address
will auto increase during the 8th rising edge of
receiving the last bit of the previous register data.
Figure 4 SPI Input Timing
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IS31FL3743B
Figure 5 SPI Input Timing
Figure 6 SPI writing to IS31FL3743B (Typical)
Figure 7 SPI writing to IS31FL3743B (Automatic address increment)
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IS31FL3743B
Figure 8 SPI Reading From IS31FL3743B (Typical)
Figure 9 SPI Reading From IS31FL3743B (Automatic Address Increment)
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IS31FL3743B
Table 2 Register Definition
Address
Name
Function
Table
R/W
Default
Set PWM for each LED
3
W
0000 0000
Set Scaling for each LED
4
W
0000 0000
PG0 (0x50): PWM Register
01h~C6h
PWM Register
PG1 (0x51): LED Scaling
01h~C6h
Scaling Register
PG2 (0x52): Function Register
00h
Configuration Register
Configure the operation mode
6
W
0000 0000
01h
Global Current Control
Register
Set the global current
7
W
0000 0000
02h
Pull Down/Up Resistor
Selection Register
Set the pull down resistor for SWx and
pull up resistor for CSy
8
W
0011 0011
Open Register
Store the open information
9
R
0000 0000
24h
Temperature Status
Store the temperature point of the IC
10
W
0000 0000
25h
Spread Spectrum Register
Spread spectrum function enable
11
W
0000 0000
2Fh
Reset Register
Reset all register to POR state
-
W
0000 0000
03h~23h
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IS31FL3743B
Page 0 (PG0, Page No. = 0x50): PWM Register
Figure 10 PWM Register
Table 3 PG0: 01h ~ C6h PWM Register
Bit
D7:D0
Name
PWM
Default
0000 0000
Duty
PWM
I OUT ( PEAK ) Duty
256
PWM
(1)
7
D [n ] 2
(2)
IOUT is the output current of CSy (y=1~18),
Each dot has a byte to modulate the PWM duty in
256 steps.
The value of the PWM Registers decides the
average current of each LED noted ILED.
ILED computed by Formula (1):
I LED
33s
1
1
33s 0.83s 0.3s 11 11.377
n
n 0
Where Duty is the duty cycle of SWx, see SCANING
TIMING section for more information.
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I OUT( PEAK)
343 GCC SL
RISET 256 256
(3)
GCC is the Global Current Control register (PG2,
01h) value, SL is the Scaling Register value as Table
9 and RISET is the external resistor of ISET pin. D[n]
stands for the individual bit value, 1 or 0, in location
n.
For example: if D7:D0=1011 0101 (0xB5, 181),
GCC=1111 1111, RISET=10kΩ, SL=1111 1111:
I LED
343
255 255
1
181
10 k 256 256 11 . 377
256
12
IS31FL3743B
Page 1 (PG1, Page No.= 0x51): Scaling Register
T01
T02
SW1
T03
SW2
T04
SW3
T05
SW4
T06
SW5
T07
T08
SW7
SW6
T10
T09
SW8
T11
SW10 SW11
SW9
CS18
12
24
36
48
5A 6C
7E
90
A2
B4
C6
CS17
11
23
35
47
59
6B
7D
8F
A1
B3
C5
CS16
10
22
34
46
58
6A 7C
8E
A0
B2
C4
PVCC
PAGE 1
Y
X
CS3
CS2
CS1
03
15
27
39
4B
5D
6F
81
93
A5
B7
02
14
26
38
4A 5C
6E
80
92
A4
B6
01
13
25
37
49
6D
7F
91
A3
B5
5B
Figure 11 Scaling Register
IOUT is the output current of CSy (y=1~18), GCC is
the Global Current Control Register (PG2, 01h)
value and RISET is the external resistor of ISET pin.
D[n] stands for the individual bit value, 1 or 0, in
location n.
Table 4 PG1: 01h ~ C6h Scaling Register
Bit
D7:D0
Name
SL
Default
0000 0000
Scaling register control the DC output current of
each dot. Each dot has a byte to modulate the
scaling in 256 steps.
For example: if RISET=10kΩ, GCC=1111 1111,
SL=0111 1111:
SL
The value of the Scaling Register decides the peak
current of each LED noted IOUT(PEAK).
I OUT( PEAK)
343 GCC SL
RISET 256 256
SL
(3)
n
127
n0
I OUT
IOUT(PEAK) computed by Formula (3):
7
D[n] 2
343
255 127
16 . 8 mA
10 k 256 256
I LED 16 .8 mA
1
PWM
11 .377
256
7
D[n] 2
n
n0
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IS31FL3743B
Table 5 Page 2 (PG2, Page No. = 0x52): Function Register
Register
Name
Function
Table
R/W
Default
00h
Configuration Register
Configure the operation mode
10
W
0000 0000
01h
Global Current Control
Register
Set the global current
11
W
0000 0000
02h
Pull Down/Up Resistor
Selection Register
Set the pull down resistor for SWx
and pull up resistor for CSy
12
W
0011 0011
03h~23h
Open/short Register
Store the open/short information
13
R
0000 0000
24h
Temperature Status
Store the temperature point of the IC
14
W
0000 0000
25h
Spread Spectrum Register
Spread spectrum function enable
15
W
0000 0000
2Fh
Reset Register
Reset all register to POR state
-
W
0000 0000
Table 6 00h Configuration Register
Bit
D7:D4
D3
D2:D1
D0
Name
SWS
-
OSDE
SSD
Default
0000
1
00
0
The Configuration Register sets operating mode of
IS31FL3743B.
Note the D3 need to be configured as “1”.
When OSDE set to “01”, open detection will be trigger
once, the user could trigger open detection again by
set OSDE from “00” to “01”.
Before set OSDE, the GCC should set to 0x0F, please
check OPEN/SHORT DETECT FUNCTION section for
more information.
When SSD is “0”, IS31FL3743B works in software
shutdown mode and to normal operate the SSD bit
should set to “1”. SWS control the duty cycle of the SW,
default mode is 1/11.
SSD
0
1
Software Shutdown Control
Software shutdown
Normal operation
OSDE
00/11
01
10
Open Detection Enable
Disable open/short detection
Enable open detection
Enable short detection
SWS
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
SWx Setting
SW1~SW11, 1/11
SW1~SW10, 1/10, SW11 no-active
SW1~SW9, 1/9, SW10~SW11 no-active
SW1~SW8, 1/8, SW9~SW11 no-active
SW1~SW7, 1/7, SW8~SW11 no-active
SW1~SW6, 1/6, SW7~SW11 no-active
SW1~SW5, 1/5, SW6~SW11 no-active
SW1~SW4, 1/4, SW5~SW11 no-active
SW1~SW3, 1/3, SW4~SW11 no-active
SW1~SW2, 1/2, SW3~SW11 no-active
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1010 All CSx work as current sinks only, no scan
Others Not allowed
Table 7 01h Global Current Control Register
Bit
D7:D0
Name
GCC
Default
0000 0000
The Global Current Control Register modulates all
CSy (x=1~18) DC current which is noted as IOUT in
256 steps.
IOUT is computed by the Formula (3):
I OUT( PEAK)
343 GCC SL
RISET 256 256
GCC
(3)
7
D[ n ] 2
n
n0
Where D[n] stands for the individual bit value, 1 or 0,
in location n.
Table 8 02h Pull Down/Up Resistor Selection
Register
Bit
D7
D6:D4
D3
D2:D0
Name
PHC
SWPDR
-
CSPUR
Default
0
011
0
011
Set pull down resistor for SWx and pull up resistor for
CSy.
Please check DE-GHOST FUNCTION section for
more information.
PHC
0
1
Phase choice
0 degree phase delay
180 degree phase delay
14
IS31FL3743B
SWPDR
SWx Pull down Resistor Selection Bit
000
No pull down resistor
001
0.5kΩ only in SWx off time
010
1.0kΩ only in SWx off time
011
2.0kΩ only in SWx off time
100
1.0kΩ all the time
101
2.0kΩ all the time
110
4.0kΩ all the time
111
8.0kΩ all the time
CSPUR
CSy Pull up Resistor Selection Bit
000
No pull up resistor
001
0.5kΩ only in CSx off time
010
1.0kΩ only in CSx off time
011
2.0kΩ only in CSx off time
100
1.0kΩ all the time
101
2.0kΩ all the time
110
4.0kΩ all the time
111
8.0kΩ all the time
Table 9 Open Register (Read Only)
03h~23h Open Information
Bit
D7:D6
D5:D0
Name
-
CS18:CS13,
CS12:CS07,CS06:CS01
Default
00
00 0000
When OSDE (PG2, 00h) is set to “01”, open detection
will be trigger once, and the open information will be
stored at 03h~23h.
When OSDE (PG2, 00h) set to “10”, short detection
will be trigger once, and the short information will be
stored at 03h~23h.
Before set OSDE, the GCC should set to 0x0F, please
check OPEN/SHORT DETECT FUNCTION section for
more information.
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Figure 12 Open Register
Table 10 24h Temperature Status
Bit
D7:D4
D3:D2
D1:D0
Name
-
TS
TROF
Default
0000
00
00
TS store the temperature point of the IC. If the IC
temperature reaches the temperature point the IC will
trigger the thermal roll off and will decrease the
current as TROF set percentage.
TROF
00
01
10
11
percentage of output current
100%
75%
55%
30%
TS
00
01
10
11
Temperature Point, Thermal roll off start point
140D
120D
100D
90D
15
IS31FL3743B
Table 11 25h Spread Spectrum Register
Bit
D7:D6
D4
D3:D2
D1:D0
Name
SYNC
SSP
RNG
CLT
Default
00
0
00
00
When SYNC bits are set to “11”, the IS31FL3745 is
configured as the master clock source and the SYNC
pin will generate a clock signal distributed to the clock
slave devices. To be configured as a clock slave
device and accept an external clock input the slave
device’s SYNC bits must be set to “10”.
When SSP enable, the spread spectrum function will
be enabled and the RNG & CLT bits will adjust the
range and cycle time of spread spectrum function.
SYNC
0x
10
11
Enable of SYNC function
Disable SYNC function, 30kOhm pull-low
Slave, clock input
Master, clock output
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SSP
0
1
Spread spectrum function enable
Disable
Enable
RNG
00
01
10
11
Spread spectrum range
±5%
±15%
±24%
±34%
CLT
00
01
10
11
Spread spectrum cycle time
1980μs
1200μs
820μs
660μs
2Fh Reset Register
Once user writes the Reset Register with 0xAE,
IS31FL3743B will reset all the IS31FL3743B registers
to their default value. On initial power-up, the
IS31FL3743B registers are reset to their default
values for a blank display.
16
IS31FL3743B
APPLICATION INFORMATION
I OUT
343
GCC
SL
R ISET
256
256
Figure 13 Scanning Timing
SCANING TIMING
As shown in Figure above, the SW1~SW11 is turned
on by serial, LED is driven 11 by 11 within the SWx
(x=1~11) on time (SWx, x=1~11 is source and it is high
when LED on) , including the non-overlap blanking
time during scan, the duty cycle of SWx (active high,
x=1~11) is:
Duty
33s
1
1
(2)
33s 0.83s 0.3s 11 11.377
Where 33μs is tSCAN, the period of scanning and
0.83μs is tNOL, the non-overlap time and 0.3μs is the
CSx delay time.
PWM CONTROL
After setting the IOUT and GCC, the brightness of each
LEDs (LED average current (ILED)) can be modulated
with 256 steps by PWM Register, as described in
Formula (1).
I LED
PWM
I OUT ( PEAK ) Duty (1)
256
Where PWM is PWM Registers (PG0, 00h~B3h /PG1,
01h~C6h) data showing in Table 7.
343
255 255
34 mA
10 k 256 256
1
PWM
34 mA
11.377
256
I OUT ( PEAK )
I LED
Writing new data continuously to the registers can
modulate the brightness of the LEDs to achieve a
breathing effect.
GAMMA CORRECTION
In order to perform a better visual LED breathing
effect we recommend using a gamma corrected PWM
value to set the LED intensity. This results in a
reduced number of steps for the LED intensity setting,
but causes the change in intensity to appear more
linear to the human eye.
Gamma correction, also known as gamma
compression or encoding, is used to encode linear
luminance to match the non-linear characteristics of
display. Since the IS31FL3743B can modulate the
brightness of the LEDs with 256 steps, a gamma
correction function can be applied when computing
each subsequent LED intensity setting such that the
changes in brightness matches the human eye's
brightness curve.
For example, in Figure 1, if RISET= 10kΩ, PWM= 255,
and GCC= 255, Scaling= 255, then
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IS31FL3743B
256
Table 12 32 Gamma Steps with 256 PWM Steps
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
0
1
2
4
6
10
13
18
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
22
28
33
39
46
53
61
69
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
78
86
96
106
116
126
138
149
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
161
173
186
199
212
226
240
255
256
224
192
PWM Data
C(0)
160
128
96
64
32
224
0
0
8
16
PWM Data
192
32
40
48
56
64
Intensity Steps
160
Figure 15 Gamma Correction (64 Steps)
128
Note: The data of 32 gamma steps is the standard value and the
data of 64 gamma steps is the recommended value.
96
OPERATING MODE
64
32
0
0
4
8
12
16
20
24
28
32
Intensity Steps
Figure 14 Gamma Correction (32 Steps)
Choosing more gamma steps provides for a more
continuous looking breathing effect. This is useful for
very long breathing cycles. The recommended
configuration is defined by the breath cycle T. When
T=1s, choose 32 gamma steps, when T=2s, choose 64
gamma steps. The user must decide the final number
of gamma steps not only by the LED itself, but also
based on the visual performance of the finished
product.
Table 13 64 Gamma Steps with 256 PWM Steps
C(0)
24
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
0
1
2
3
4
5
6
7
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
8
10
12
14
16
18
20
22
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
24
26
29
32
35
38
41
44
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
47
50
53
57
61
65
69
73
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(38)
C(39)
77
81
85
89
94
99
104
109
C(40)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
C(47)
114
119
124
129
134
140
146
152
C(48)
C(49)
C(50)
C(51)
C(52)
C(53)
C(54)
C(55)
158
164
170
176
182
188
195
202
C(56)
C(57)
C(58)
C(59)
C(60)
C(61)
C(62)
C(63)
209
216
223
230
237
244
251
255
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IS31FL3743B can only operate in PWM Mode. The
brightness of each LED can be modulated with 256
steps by PWM registers. For example, if the data in
PWM Register is “0000 0100”, then the PWM is the
fourth step.
Writing new data continuously to the registers can
modulate the brightness of the LEDs to achieve a
breathing effect.
OPEN/SHORT DETECT FUNCTION
IS31FL3743B has open and short detect bit for each
LED.
By setting the OSD bits of the Configuration Register
(PG2, 00h) from “00” to “01” or ’10’, the LED
Open/short Register will start to store the open/short
information and after at least 2 scanning cycles and
the MCU can get the open/short information by
reading the 03h~23h, for those dots are turned off via
LED On/Off Registers (PG0, 00h~17h), the
open/short data will not get refreshed when setting the
OSD bit of the Configuration Register.
The two configurations need to set before setting the
OSD bits:
1
2
0x0F≤GCC≤0x40, 02h=0x00
0x01≤GCC≤0x40, 02h=0x30
Where GCC is the Global Current Control Register
(PG2, 01h) and both case 1 or two can get the correct
open and short information. 02h is the Pull Down/UP
Resistor Selection Register and 0x30 is to enable the
SWx pull-up function.
The detect action is one-off event and each time
before reading out the open/short information, the
OSD bit of the Configuration Register (PG3, 00h)
need to be set from “0” to “1” (clear before set
operation).
18
IS31FL3743B
DE-GHOST FUNCTION
Hardware Shutdown
The “ghost” term is used to describe the behavior of an
LED that should be OFF but instead glows dimly when
another LED is turned ON. A ghosting effect typically
can occur when multiplexing LEDs. In matrix
architecture any parasitic capacitance found in the
constant-current outputs or the PCB traces to the
LEDs may provide sufficient current to dimly light an
LED to create a ghosting effect.
The chip enters hardware shutdown when the SDB
pin is pulled low. All analog circuits are disabled
during hardware shutdown, typical the current
consume is 1.3μA.
To prevent this LED ghost effect, the IS31FL3743B
has integrated Pull down resistors for each SWx
(x=1~11) and Pull up resistors for each CSy (y=1~18).
Select the right SWx Pull down resistor (PG2, 02h)
and CSy Pull up resistor (PG2, 02h) which eliminates
the ghost LED for a particular matrix layout
configuration.
Typically, selecting the 2kΩ will be sufficient to
eliminate the LED ghost phenomenon.
The SWx Pull down resistors and CSy Pull up resistors
are active only when the CSy/SWx output working the
OFF state and therefore no power is lost through these
resistors.
SHUTDOWN MODE
Shutdown mode can be used as a means of reducing
power consumption. During shutdown mode all
registers retain their data.
Software Shutdown
By setting SSD bit of the Configuration Register (PG2,
00h) to “0”, the IS31FL3743B will operate in software
shutdown mode. When the IS31FL3743B is in
software shutdown, all current sources are switched off,
so that the matrix is blanked. All registers can be
operated. Typical current consume is 1.3μA.
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The chip releases hardware shutdown when the SDB
pin is pulled high. During hardware shutdown state
Function Register can be operated.
If VCC has risk drop below 1.75V but above 0.1V
during SDB pulled low, please re-initialize all Function
Registers before SDB pulled high.
LAYOUT
As described in external resistor (RISET), the chip
consumes lots of power. Please consider below
factors when layout the PCB.
1. The VCC (PVCC, AVCC) capacitors need to close to
the chip and the ground side should well connected to
the GND of the chip.
2. RISET should be close to the chip and the ground
side should well connect to the GND of the chip.
3. The thermal pad should connect to ground pins and
the PCB should have the thermal pad too, usually this
pad should have 16 or 25 via thru the PCB to other
side’s ground area to help radiate the heat. About the
thermal pad size, please refer to the land pattern of
each package.
4. The CSy pins maximum current is 34mA
(RISET=10kΩ), and the SWx pins maximum current is
larger, the width of the trace, SWx should have wider
trace then CSy.
19
IS31FL3743B
CLASSIFICATION REFLOW PROFILES
Profile Feature
Pb-Free Assembly
Preheat & Soak
Temperature min (Tsmin)
Temperature max (Tsmax)
Time (Tsmin to Tsmax) (ts)
150°C
200°C
60-120 seconds
Average ramp-up rate (Tsmax to Tp)
3°C/second max.
Liquidous temperature (TL)
Time at liquidous (tL)
217°C
60-150 seconds
Peak package body temperature (Tp)*
Max 260°C
Time (tp)** within 5°C of the specified
classification temperature (Tc)
Max 30 seconds
Average ramp-down rate (Tp to Tsmax)
6°C/second max.
Time 25°C to peak temperature
8 minutes max.
Figure 16 Classification Profile
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IS31FL3743B
PACKAGE INFORMATION
UQFN-40
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Rev. A, 05/13/2019
21
IS31FL3743B
RECOMMENDED LAND PATTERN
Note:
1. Land pattern complies to IPC-7351.
2. All dimensions in MM.
3. This document (including dimensions, notes & specs) is a recommendation based on typical circuit board manufacturing parameters. Since
land pattern design depends on many factors unknown (eg. User’s board manufacturing specs), user must determine suitability for use.
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Rev. A, 05/13/2019
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IS31FL3743B
REVISION HISTORY
Revision
Detail Information
Date
0A
Initial release
2018.04.18
0B
Add VOH and VOL in ELECTRICAL CHARACTERISTICS table
2018.09.20
A
Update to final version
2019.05.13
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