IS31BL3228A/B

IS31BL3228A/B
WHITE LED DRIVER
January 2014
GENERAL DESCRIPTION
FEATURES
The IS31BL3228A (IS31BL3228B) is a low noise,
constant frequency charge pump DC/DC converter
for white LED applications. The IS31BL3228A
(IS31BL3228B) is capable of driving up to four (six)
channels of LEDs at preset 20mA per channel from a
2.8V to 5.5V input. The current sinks may be operated
individually or in parallel for driving higher current
LEDs. Only one 1μF small capacitor (at C+ thru C-)
and two small 2.2μF capacitors (at VCC and VOUT) are
needed, it makes this part ideally suited for small,
battery-powered applications.




The serial digital input is used to enable, disable, and
set current for each LED with 14 settings down to
1.8mA. Each output of the
IS31BL3228A/IS31BL3228B is equipped with built-in
soft-start circuitry prevents excessive inrush current
during start-up. A low-current shutdown feature
disconnects the load from the input and reduces
quiescent current to less than 3μA.





VCC range: 2.8V to 5.5V
Fully programmable current with single wire
14 current levels
Drives up to four (IS31BL3228A)/six
(IS31BL3228B) channels of LEDs
No inductors, low noise operation
Built-in thermal protection
Automatic soft start
Low shutdown current: ISD <3μA
UTQFN-12 (2mm × 2mm ) package
APPLICATIONS



Cell phone, smart phone, PDA
MP3, MP4, PMP
White LED backlighting
The IS31BL3228A and IS31BL3228B are available in
a Pb-free, space-saving 2mm × 2mm UTQFN-12
package.
TYPICAL APPLICATION CIRCUIT
Figure 1
Typical Application Circuit (IS31BL3228A)
Note: COUT can’t be less than 2.2μF, and when less than six channels are used, keep the unused pin to GND or floating. But channel D0 (Pin 1)
has to be used.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/31/2013
1
IS31BL3228A/B
VBattery
3
VCC
CIN
2.2 F
C+
1 F
9
D4
GND
Figure 2
8
D5
Typical Application Circuit (IS31BL3228B)
VBattery
3
CIN
2.2 F
VCC
VOUT
D0
C+
IS31BL3228A
1 F
5
6
D1
C-
D2
EN/SET
N<=14
7
Figure 3
D3
GND
1
12
11
10
Application Circuit for Less Than 4 LEDs (IS31BL3228A)
VBattery
3
CIN
2.2 F
4
VCC
5
6
C+
C-
EN/SET
D1
D2
D3
D4
GND
2
COUT
2.2 F
IS31BL3228A
N<=14
7
VOUT
D0
1 F
Figure 4
2
COUT
2.2 F
4
2
10
D3
EN/SET
7
1
11
D2
N<=14
2
12
D1
C-
6
1
1
IS31BL3228B
5
2
COUT
2.2 F
D0
4
1
2
VOUT
D5
1
12
11
10
9
8
Application Circuit for Less Than 6 LEDs (IS31BL3228B)
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/31/2013
2
IS31BL3228A/B
PIN CONFIGURATION
Package
Pin Configuration (Top View)
UTQFN-12
IS31BL3228A
UTQFN-12
IS31BL3228B
PIN DESCRIPTION
No.
IS31BL3228A IS31BL3228B
Description
White LED channel, channel D0 must be
used.
Charge pump output to drive load circuits,
requires 2.2μF capacitor connected between
this pin and ground pin.
1
D0
D0
2
VOUT
VOUT
3
VCC
VCC
4
C+
C+
Flying capacitor positive terminal.
5
C-
C-
Flying capacitor negative terminal.
6
EN/SET
EN/SET
7
GND
GND
NC
-
-
D5, D4
White LED channel 5 and channel 4.
D3~D1
D3~D1
White LED channel 3~1.
8, 9
10~12
Power supply input, requires 2.2μF capacitor
connect between this pin and ground pin.
Serial digital input, control the output current.
Ground.
No connection.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/31/2013
3
IS31BL3228A/B
ORDERING INFORMATION
Industrial Range: -40°C to +85°C
Order Part No.
IS31BL3228A-UTLS2-TR
IS31BL3228B-UTLS2-TR
Package
QTY/Reel
UTQFN-12, Lead-free
3000
Copyright © 2014 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
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/31/2013
4
IS31BL3228A/B
ABSOLUTE MAXIMUM RATINGS
Supply voltage, VCC
Voltage at any input pin
Maximum junction temperature, TJMAX
Storage temperature range, TSTG
Operating temperature range, TA
ESD (HBM)
ESD (CDM)
-0.3V ~ +6.0V
-0.3V ~ VCC+0.3V
150°C
-65°C ~ +150°C
−40°C ~ +85°C
1kV
1kV
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
CIN = COUT =2.2μF, TA = +25°C, unless otherwise noted. Typical value are TA = 25°C, VCC = 3.6V.
Symbol
Parameter
Condition
Min.
Typ.
Max.
Unit
5.5
V
Input Power Supply
VCC
Operation range
ICC
Operating current
2.8 ≤ VCC ≤ 5.5, ISET = 20mA
charge pump disable
0.5
1
mA
ISD
Shutdown current
VEN/SET = 0V
0.5
3
μA
IDX
ISINK average current accuracy
ISET = 20mA
20
mA
Current matching
ISET = 20mA
±0.9
%
210
mV
I(D-Match)
VTH
2.8
Transition threshold at any ISINK pin
Charge Pump Section
TSS
Soft-start time
(Note 1)
33
μs
fCLK
Clock frequency
(Note 1)
1
MHz
VEN(L)
Enable threshold low
VCC = 2.8V
VEN(H)
Enable threshold high
VCC = 5.5V
EN/SET
tEN/SET LO
EN/SET low time
0.4
1.4
V
0.3
tEN/SET_HI_MIN Minimum EN/SET high time
V
75
50
tEN/SET_HI_MAX Maximum EN/SET high time
μs
ns
75
μs
tOFF
EN/SET off timeout
(Note 1)
500
μs
tLAT
EN/SET latch timeout
(Note 1)
500
μs
REN/SET DOWN EN/SET pull down resistor
500
kΩ
Note 1: Guaranteed by design.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/31/2013
5
IS31BL3228A/B
TYPICAL PERFORMANCE CHARACTERISTIC
LED Current vs. Supply Voltage (IS31BL3228A)
Figure 6
22
560
21
540
520
20
LED Current vs. Supply Voltage (IS31BL3228B)
Charge Pump
Disable
ISET = 20mA
500
19
480
18
460
17
ICC
IDX - LED Current (mA)
Figure 5
16
440
420
15
-40
-15
Figure 7
10
35
60
85
LED Current vs. Temperature
400
2.5
3
Figure 8
3.5
4
4.5
5
5.5
ICC vs. Supply Voltage
1.4
1.2
1
0.8
0.6
ISD
0.4
0.2
0
2.5
3
3.5
Figure 9
4
4.5
5
5.5
ISD vs. Supply Voltage
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/31/2013
6
IS31BL3228A/B
FUNCTIONAL BLOCK DIAGRAM
IS31BL3228A
IS31BL3228B
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/31/2013
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IS31BL3228A/B
APPLICATION INFORMATION
GENERAL DESCRIPTION
The IS31BL3228A (IS31BL3228B) charge pump drives
up to four (six) white LEDs with regulated constant
current for uniform intensity. It achieves 20mA output
drive capability over the 1-cell lithium-battery input
voltage range. Fixed-frequency switching of 1MHz
allows for tiny external components, and the regulation
scheme is optimized to ensure low EMI and low input
ripple.
CONSTANT CURRENT OUTPUT LEVEL SETTING
The constant current source levels for D5/D3 to D0 are
set via the serial interface according to a logarithmic
scale. For the whole 14 codes, each code is
approximately 1.5dB lower than the previous code. In
this manner, LED brightness appears linear with each
increasing code count. Because the outputs D5/D3 to
D0 are true independent constant current sources, the
voltage observed on any single given output will be
determined by the actual forward voltage (VF) for the
LED being driven.
Figure 10
FUNCTIONAL DESCRIPTION
The four (six) constant current source outputs (D5/D3
to D0) can drive four (six) individual LEDs with a
maximum current of 20mA each. The PCC wire serial
interface enables the IS31BL3228A (IS31BL3228B)
and sets the current source magnitudes.
PCC wire Serial Interface Timing
PCC WIRE SERIAL INTERFACE
The current level magnitude is controlled by Pulse
Count Control (PCC wire) serial interface. The
interface records rising edges of the EN/SET pin and
decodes them into 14 different states. The 14 current
level settings available are indicated in Table 1.
The PCC wire serial interface has flexible timing. Data
can be clocked-in at speeds from 15kHz to above
1MHz. After data is submitted, EN/SET is held high to
latch the data. Once EN/SET has been held in the logic
high state for time tLAT, the programmed current
becomes active and the internal data register is reset
to zero. For subsequent current level programming,
the number of rising edges corresponding to the
desired code must be entered on the EN/SET pin.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/31/2013
Since the output current sources of the IS31BL3228A
(IS31BL3228B) are programmable, no PWM (pulse
width modulation) or additional control circuitry is
needed to control LED brightness. This feature greatly
reduces the burden on a microcontroller or system IC
to manage LED or display brightness, allowing the
user to "set it and forget it." With its high-speed serial
interface (1MHz data rate), the output current of the
IS31BL3228A (IS31BL3228B) can be changed
successively to brighten or dim LEDs, in smooth
transitions (e.g., to fade-out) or in abrupt steps, giving
the user complete programmability and real-time
control of LED brightness.
Table 1 Current Level Setting
Data
Output(mA/Ch)
Data
Output(mA/Ch)
1
20.0
8
6.0
2
17.0
9
5.0
3
14.0
10
4.2
4
12.0
11
3.6
5
10.0
12
3
6
8.6
13
2.4
7
7.0
14
1.8
8
IS31BL3228A/B
PCC WIRE SERIAL INTERFACE TIMING
CAPACITOR SELECTION
Figure 10 shows the timing of PPC wire. When
EN/SET is held low for an amount of time greater than
tOFF, the IS31BL3228A (IS31BL3228B) enters into
shutdown mode and draws less than 1µA from VCC.
The internal data register is reset to zero during
shutdown.
When driving fewer than four (IS31BL3228A) (six for
IS31BL3228B) LEDs, keep the unused pin to GND or
floating, but D0 must be connected.
Careful selection of the external capacitors (CIN and
COUT) is important because they will affect turn-on time,
output ripple, and transient performance. Optimum
performance will be obtained when low equivalent
series resistance (ESR) ceramic capacitors are used.
In general, low ESR may be defined as less than
100mΩ. A value of 2.2µF for all three capacitors is a
good starting point when choosing capacitors. If the
LED current sources are programmed only for light
current levels, then the capacitor size may be
decreased.
DEVICE SWITCHING NOISE PERFORMANCE
CAPACITOR CHARACTERISTICS
The IS31BL3228A (IS31BL3228B) operates at a fixed
frequency of approximately 1MHz to control noise and
limit harmonics that can interfere with the RF operation
of cellular telephone handsets or other communication
devices. Back-injected noise appearing on the input
pin of the charge pump is 60mV peak-to-peak, typically
ten times less than inductor-based DC/DC boost
converter white LED backlight solutions. The
IS31BL3228A (IS31BL3228B) soft-start feature
prevents noise transient effects associated with inrush
currents during start-up of the charge pump circuit.
Ceramic composition capacitors are highly recommended over all other types of capacitors for use with
the IS31BL3228A (IS31BL3228B). Ceramic capacitors
offer many advantages over their tantalum and
aluminum electrolytic counterparts. A ceramic
capacitor typically has very low ESR, is lowest cost,
has a smaller PCB footprint, and is non-polarized. Low
ESR ceramic capacitors help to maximize charge
pump transient response. Since ceramic capacitors
are non-polarized, they are not prone to incorrect
connection damage.
THERMAL PROTECTION
EQUIVALENT SERIES RESISTANCE
The IS31BL3228A (IS31BL3228B) has a thermal
protection circuit that will shut down the chip if the die
temperature rises above the thermal limit.
ESR is an important characteristic to consider when
selecting a capacitor. ESR is a resistance internal to a
capacitor that is caused by the leads, internal
connections, size or area, material composition, and
ambient temperature. Capacitor ESR is typically
measured in milliohms for ceramic capacitors and can
range to more than several ohms for tantalum or
aluminum electrolytic capacitors.
DRIVE FEWER LEDS
Although the IS31BL3228A (IS31BL3228B) is
designed for driving white LEDs, the device also can
be used to drive most types of LEDs with forward
voltage specifications ranging from 1.8V to 4.7V. LED
applications may include main and sub-LCD display
backlighting, camera photo-flash applications, color
(RGB) LEDs, infrared (IR) diodes for remotes, and
other loads benefiting from a controlled output current
generated from a varying input voltage. Since the
D5/D3 to D0 output current sources are matched with
negligible voltage dependence, the LED brightness will
be matched regardless of the specific LED forward
voltage (VF) levels. In some instances (e.g., in high
luminous output applications such as photo flash), it
may be necessary to drive high-VF type LEDs. The low
dropout current sources in the IS31BL3228A
(IS31BL3228B) make it capable of driving LEDs with
forward voltages as high as 4.7V at full current from an
input supply of 2.8V to 5.5V. Outputs can be paralleled
to drive high-current LEDs without complication
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/31/2013
CERAMIC CAPACITOR MATERIALS
Ceramic capacitors less than 0.1µF are typically made
from NPO or C0G materials. NPO and C0G materials
generally have tight tolerance and are very stable over
temperature. Larger capacitor values are usually
composed of X7R, X5R, Z5U, or Y5V dielectric
materials. Large ceramic capacitors (i.e., greater than
2.2µF) are often available in low-cost Y5V and Z5U
dielectrics.
Capacitor area is another contributor to ESR.
Capacitors that are physically large will have a lower
ESR when compared to an equivalent material smaller
capacitor. These larger devices can improve circuit
transient response when compared to an equal value
capacitor in a smaller package size.
9
IS31BL3228A/B
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 11
Classification profile
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/31/2013
10
IS31BL3228A/B
PACKAGE INFORMATION
UTQFN-12
Note: All dimensions in millimeters unless otherwise stated.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. B, 12/31/2013
11