ISSI IS31FL3218

IS31FL3218
18 CHANNELS LED DRIVER
April 2012
GENERAL DESCRIPTION
FEATURES
IS31FL3218 is comprised of 18 constant current
channels each with independent PWM control,
designed for driving LEDs. The output current of each
channel can be set at up to 38mA (Max.) by an external
resistor. The average LED current of each channel can
be changed in 256 steps by changing the PWM duty
cycle through an I2C interface.







The chip can be turned off by pulling the SDB pin low or
by using the software shutdown feature to reduce
power consumption. The slave address is fixed “1010
1000”.
2.7V to 5.5V supply
I2C interface, automatic address increment
function
Internal reset register
Modulate LED brightness with 256 steps PWM
Each channel can be controlled independently
-40°C to +85°C temperature range
QFN-24 (4mm × 4mm), SOP-24 package
APPLICATIONS
IS31FL3218 is available in QFN-24 (4mm × 4mm) and
SOP-24. It operates from 2.7V to 5.5V over the
temperature range of -40°C to +85°C.


Mobile phones and other hand-held devices for
LED display
LED in home appliances
TYPICAL APPLICATION CIRCUIT
VBattery
VBattery
3
OUT1
VCC
1 F
OUT2
0.1 F
OUT3
OUT4
OUT5
VDD
4.7k
OUT6
5
6
Micro
Controller
OUT7
4.7k
24
IS31FL3218
OUT8
SDA
OUT9
SCL
OUT10
SDB
OUT11
OUT12
100k
OUT13
OUT14
2
OUT15
R_EXT
OUT16
3.3k
4
OUT17
GND
OUT18
Figure 1
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
1
Typical Application Circuit
Note: The maximum output current is set up to 23mA when REXT = 3.3kΩ. The maximum output current can be set by external resistor, REXT.
Please refer to the detail information in Page 9.
Note: The IC should be placed far away from the mobile antenna in order to prevent the EMI.
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Rev.B, 03/28/2012
1
IS31FL3218
PIN CONFIGURATION
Package
Pin Configuration (Top View)
QFN-24
SOP-24
PIN DESCRIPTION
No.
Pin
Description
1
OUT18
Output channel for LEDs.
2
R_EXT
Input terminal used to connect an external resistor.
This regulates the output current.
3
VCC
Power supply.
4
GND
Ground.
5
SDA
I2C serial data.
6
SCL
I2C serial clock.
7~23
OUT1 ~ OUT17
Output channel for LEDs.
24
SDB
Shutdown the chip when pulled low.
Thermal Pad
Connect to GND.
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2
IS31FL3218
ORDERING INFORMATION
Industrial Range: -40°C to +85°C
Order Part No.
Package
QTY
IS31FL3218-QFLS2-TR
QFN-24, Lead-free
2500/Reel
IS31FL3218-GRLS2
SOP-24, Lead-free
30/Tube
Copyright © 2011 Integrated Silicon Solution, Inc. All rights reserved. ISSI reserves the right to make changes to this specification and its products at any time without notice. ISSI 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. Integrated Silicon Solution, Inc. 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 Integrated Silicon Solution, Inc. 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 Integrated Silicon Solution, Inc is adequately protected under the circumstances
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Rev.B, 03/28/2012
3
IS31FL3218
ABSOLUTE MAXIMUM RATINGS
Supply voltage, VCC
Voltage at SCL, SDA, SDB
Voltage at OUT1 to OUT18
Maximum junction temperature, TJMAX
Storage temperature range, TSTG
Operating temperature range, TA
ESD (HBM)
-0.3V ~ +6.0V
-0.3V ~ VCC+0.3V
+5V
150°C
-65°C ~ +150°C
−40°C ~ +85°C
4kV
Note:
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
TA = -40°C ~ +85°C, VCC = 2.7V ~ 5.5V, unless otherwise noted. Typical values are TA = 25°C, VCC = 3.6V.
Symbol
Parameter
VCC
Supply voltage
IMAX
Maximum output
each channel
ICC
Condition
Min.
Typ.
2.7
current
of VCC = 4.2V, VOUT = 0.8V
REXT = 2kΩ (Note 1)
Max.
Unit
5.5
V
38
mA
Quiescent power supply current REXT = 3.3kΩ
5.25
mA
ISD
Shutdown current
VSDB = 0V or software shutdown
3.1
μA
IOZ
Output leakage current
VSDB = 0V or software shutdown,
VOUT = 5V
VEXT
1
Output voltage of R-EXT pin
1.3
μA
V
Logic Electrical Characteristics (SDA, SCL, SDB)
VIL
Logic “0” input voltage
VCC = 2.7V
VIH
Logic “1” input voltage
VCC = 5.5V
IIL
Logic “0” input current
IIH
Logic “1” input current
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Rev.B, 03/28/2012
0.4
1.4
V
V
5
(Note 2)
5
(Note 2)
nA
nA
4
IS31FL3218
DIGITAL INPUT SWITCHING CHARACTERISTICS (Note 2)
Symbol
Parameter
Condition
Min.
Typ.
Max.
Unit
400
kHz
fSCL
Serial-Clock frequency
tBUF
Bus free time between a STOP and a START
condition
1.3
μs
tHD, STA
Hold time (repeated) START condition
0.6
μs
tSU, STA
Repeated START condition setup time
0.6
μs
tSU, STO
STOP condition setup time
0.6
μs
tHD, DAT
Data hold time
tSU, DAT
Data setup time
100
ns
tLOW
SCL clock low period
1.3
μs
tHIGH
SCL clock high period
0.7
μs
0.9
μs
tR
Rise time of both SDA and SCL signals,
receiving
(Note 3)
20+0.1Cb
300
ns
tF
Fall time of both SDA and SCL signals,
receiving
(Note 3)
20+0.1Cb
300
ns
Note 1: The recommended minimum value of REXT is 2kΩ, or it may cause a large current.
Note 2: Guaranteed by design.
Note 3: Cb = total capacitance of one bus line in pF. ISINK ≤ 6mA. tR and tF measured between 0.3 × VCC and 0.7 × VCC.
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IS31FL3218
DETAILED DESCRIPTION
Then the master sends an SCL pulse. If the
IS31FL3218 has received the address correctly, then it
holds the SDA line low during the SCL pulse. If the SDA
line is not low, then the master should send a “STOP”
signal (discussed later) and abort the transfer.
I2C INTERFACE
The IS31FL3218 uses a serial bus, which conforms to
the I2C protocol, to control the chip’s functions with two
wires: SCL and SDA. The IS31FL3218’s slave address
is “1010 1000”. It only supports write operations.
Following acknowledge of IS31FL3218, the register
address byte is sent, most significant bit first.
IS31FL3218 must generate another acknowledge
indicating that the register address has been received.
The SCL line is uni-directional. The SDA line is
bi-directional (open-collector) with a pull-up resistor
(typically 4.7kΩ). The maximum clock frequency
specified by the I2C standard is 400kHz. In this
discussion, the master is the microcontroller and the
slave is the IS31FL3218.
Then 8-bit of data byte are sent next, most significant
bit first. Each data bit should be valid while the SCL
level is stable high. After the data byte is sent, the
IS31FL3218 must generate another acknowledge to
indicate that the data was received.
The timing diagram for the I2C is shown in Figure 2.
The SDA is latched in on the stable high level of the
SCL. When there is no interface activity, the SDA line
should be held high.
The “STOP” signal ends the transfer. To signal “STOP”,
the SDA signal goes high while the SCL signal is high.
The “START” signal is generated by lowering the SDA
signal while the SCL signal is high. The start signal will
alert all devices attached to the I2C bus to check the
incoming address against their own chip address.
ADDRESS AUTO INCREMENT
To write multiple bytes of data into IS31FL3218, load
the address of the data register that the first data byte
is intended for. During the IS31FL3218 acknowledge of
receiving the data byte, the internal address pointer will
increment by one. The next data byte sent to
IS31FL3218 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 IS31FL3218
(Figure 5).
The 8-bit chip address is sent next, most significant bit
first. Each address bit must be stable while the SCL
level is high.
After the last bit of the chip address is sent, the master
checks for the IS31FL3218’s acknowledge. The master
releases the SDA line high (through a pull-up resistor).
Figure 2
Interface timing
SDA
SCL
DATA LINE STABLE;
CHANGE OF DATA
DATA VALID
ALLOWED
Figure 3
Bit transfer
Figure 4 Writing to IS31FL3218(Typical)
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Rev.B, 03/28/2012
6
IS31FL3218
Figure 5 Writing to IS31FL3218(Automatic address increment)
REGISTERS DEFINITIONS
Table 1 Register Function
Address
00h
Name
Function
Table
Shutdown Register
Set software shutdown mode
2
PWM Register
18 channels PWM duty cycle data register
3
13h
LED Control Register1
Channel 1 to 6 enable bit
4
14h
LED Control Register2
Channel 7 to 12 enable bit
5
15h
LED Control Register3
Channel 13 to 18 enable bit
6
16h
Update Register
Load PWM Register and LED Control
Register’s data
-
17h
Reset Register
Reset all registers into default
-
01h~12h
Table 2
00h Shutdown Register
Bit
D7:D1
D0
Name
Reserved
SSD
Default
000000
0
The Shutdown Register sets software shutdown mode
of IS31FL3218.
SSD
0
1
Software Shutdown Enable
Software shutdown mode
Normal operation
Table 3
01h~12h
Bit
PWM Register(OUT1~OUT18)
D7:D0
Name
PWM
Default
0000 0000
The PWM Registers adjusts LED luminous intensity in
256 steps.
The value of a channel’s PWM Register decides the
average output current for each output, OUT1~OUT18.
The average output current may be computed using the
Formula (1):
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Rev.B, 03/28/2012
I OUT 
Default
0000 0000
xxxx xxxx
I MAX 7
  D[n]  2 n
256 n0
(1)
Where “n” indicates the bit location in the respective
PWM register.
For example: D7:D0 = 10110101,
IOUT = IMAX (20+22+24+25+27)/256
See Formula (2) in Page 9 to calculate the IMAX.
Table 4 13h LED Control Register 1
(OUT1~OUT6)
Bit
D7:D6
D5:D0
Name
Reserved
OUT6:OUT1
Default
00
000000
Table 5 14h LED Control Register 2
(OUT7~OUT12)
Bit
D7:D6
D5:D0
Name
Reserved
OUT12:OUT7
Default
00
000000
7
IS31FL3218
Table 6 15h LED Control Register 3
(OUT13~OUT18)
Bit
D7:D6
D5:D0
Name
Reserved
OUT18:OUT13
Default
00
000000
The LED Control Registers store the on or off state of
each column LED.
OUTx
0
1
LED State
LED off
LED on
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16h PWM Update Register
The data sent to the PWM Registers and the LED
Control Registers will be stored in temporary registers.
A write operation of any 8-bit value to the Update
Register is required to update the registers (01h~15h).
17h Reset Register
Once user writes any 8-bit data to the Reset Register,
IS31FL3218 will reset all registers to default value. On
initial power-up, the IS31FL3218 registers are reset to
their default values for a blank display.
8
IS31FL3218
APPLICATION INFORMATION
PWM CONTROL
256
The PWM Registers (01h~12h) can modulate LED
brightness of 18 channels with 256 steps. For example,
if the data in PWM Register is “0000 0100”, then the
PWM is the fourth step.
224
PWM Data
192
Writing new data continuously to the registers can
modulate the brightness of the LEDs to achieve a
breathing effect.
160
128
96
64
REXT
32
The maximum output current of OUT1~OUT18 can be
adjusted by the external resistor, REXT, as described in
Formula (2).
I MAX
V
 x  EXT
REXT
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 IS31FL3218 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.
C(2)
C(3)
C(4)
C(5)
8
C(6)
12
16
20
24
28
32
Intensity Steps
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 8
C(0)
64 gamma steps with 256 PWM steps
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(7)
C(40)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
C(47)
119
124
129
134
140
146
152
32 gamma steps with 256 PWM steps
C(1)
4
Figure 6
The recommended minimum value of REXT is 2kΩ.
C(0)
0
(2)
x = 58.5, VOUT = 0.8V, VEXT = 1.3V.
Table 7
0
0
1
2
4
6
10
13
18
114
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
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
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
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Rev.B, 03/28/2012
9
IS31FL3218
256
SHUTDOWN MODE
224
Shutdown mode can either be used as a means of
reducing power consumption or generating a flashing
display (repeatedly entering and leaving shutdown
mode). During shutdown mode all registers retain their
data.
PWM Data
192
160
128
SOFTWARE SHUTDOWN
96
64
32
0
0
8
16
24
32
40
48
56
64
Intensity Steps
Figure 7
Gamma Correction(64 Steps)
Note, the data of 32 gamma steps is the standard value and the data
of 64 gamma steps is the recommended value.
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Rev.B, 03/28/2012
By setting SSD bit of the Configuration Register (00h)
to “0”, the IS31FL3218 will operate in software
shutdown mode, wherein they consume only 3.1μA
(Typ.) current. When the IS31FL3218 is in software
shutdown mode, all current sources are switched off.
HARDWARE SHUTDOWN
The chip enters hardware shutdown mode when the
SDB pin is pulled low.
10
IS31FL3218
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 8
Classification profile
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11
IS31FL3218
PACKAGE INFORMATION
QFN-24
Note: All dimensions in millimeters unless otherwise stated.
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Rev.B, 03/28/2012
12
IS31FL3218
SOP-24
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13