IS31BL3233A

IS31BL3233A
2MHz, 1.5A FLASH/TORCH LED DRIVER
May 2015
GENERAL DESCRIPTION
FEATURES
The IS31BL3233A is the ideal power solution for
high-power flash LEDs used with cell phone camera
modules or digital still cameras. It is a highly integrated
step up DC-DC converter with very high switching
frequency, fixed at 2MHz, providing a very small total
solution for portable photo flash. The IS31BL3233A has
separate Flash Mode and Torch Mode enable pins for
maximum flexibility. The Flash Mode and Torch Mode
LED current is programmed by external resistors
respectively, making the flash LED solution simple to
control. If both enable pins are at logic high, the LED
current will be programmed by the Torch Mode setting
resistor. The two LED output sinks can be shorted
together externally for higher power single flash LEDs,
up to 1.5A continuous LED current. Thermal regulation
is integrated in Flash Mode to limit the IC’s temperature
and continuously provide the maximum allowed output
current.
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Various protection features are built into the
IS31BL3233A, including cycle-by-cycle input current
limit protection, output over-voltage protection, LED
fault (open or short) protection and thermal shutdown
protection. The IS31BL3233A is available in a RoHS
compliant DFN-14 (2mm × 3mm) package.
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Input voltage range: 2.7V~5.5V
Dual flash LED outputs
Drive up to total 1.5A or 0.75A per channel
1s time out in Flash Mode to protect LED
High efficiency up to 93% (1A, Flash Mode)
2MHz step-up converter
Independent Flash Mode enable and Torch Mode
enable pins
Torch Mode dimming via PWM control
Integrated thermal regulation control
LED open/short protection
Over-voltage protection
Cycle-by-cycle inductor current limit
Pb-free package: DFN-14 (2mm×3mm)
-40C° ~ +85C° temperature range
APPLICATIONS
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Mobile phones
Smart phones and PDAs
Digital still cameras
TYPICAL APPLICATION CIRCUIT
Figure 1
Typical Application Circuit (Torch Mode current is100mA and Flash Mode current is 500mA)
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Rev. A, 04/23/2015
1
IS31BL3233A
LX
1 H
VBattery
4
2.2 F
VCC
LX
5,6
0.1 F
8,9
10
Micro
Controller
11
VOUT
ENM
IS31BL3233A
1
RSETM
68k
RSETF
13.5k
2
3,13
Figure 2
COUT
4.7 F
ENF
D1
RSETM
RSETF
AGND
D2
PGND
12
14
7
Typical Application Circuit (Drive single LED, Torch Mode current is 200mA and Flash Mode current is 1A)
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2
IS31BL3233A
PIN CONFIGURATION
Package
Pin Configurations (Top View)
DFN-14
PIN DESCRIPTION
No.
Pin
Description
1
RSETM
Torch Mode current setting pin. ID1 = ID2 = 6800/RSETM.
2
RSETF
Flash Mode current setting pin. ID1 = ID2 = 6800/RSETF.
3, 13
AGND
Ground.
4
VCC
Supply voltage.
5, 6
LX
Switching node of the step-up converter.
7
PGND
Input clock for data shift on rising edge.
8, 9
VOUT
Output voltage pin.
10
ENF
Flash Mode enable pin. This pin has an internal 300kΩ pull
down resistor to AGND.
11
ENM
Torch Mode enable pin. This pin has an internal 300kΩ
pull-down resistor to AGND.
12
D1
Regulated output current sink 1, up to 0.75A current. Pins D1
and D2 can be connected together to sink 1.5A combined.
14
D2
Regulated output current sink 2, up to 0.75A current. Pins D1
and D2 can be connected together to sink 1.5A combined.
Thermal Pad
Connect to GND.
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3
IS31BL3233A
ORDERING INFORMATION
Industrial Range: -40°C to +85°C
Order Part No.
Package
QTY/Reel
IS31BL3233A-DLS2-TR
DFN-14, Lead-free
2500
Copyright © 2015 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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IS31BL3233A
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
8kV
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
The following specifications apply for VCC = 3.6V, TA = 25°C, unless otherwise noted.
Symbol
Description
Condition
Min.
Typ.
Max.
Units
5.5
V
2.68
V
IC Supply
VCC
UVLO
Input operating range
Input under voltage lockout
UVLOHYST
UVLO hysteresis
ICC
Operating current
ISD
Shutdown current
2.7
Rising edge
2.1
2.4
0.2
V
Not switching (RSETM = 135kΩ)
1.0
1.5
mA
Switching (RSETM = 135kΩ)
1.8
2.6
mA
VENF = VENM = GND
0.1
1
µA
Step-Up Converter
ILIM
Peak NMOS current limit
3
A
fSW
Oscillator frequency
2.0
MHz
DMAX
Maximum duty cycle
75
%
VOVP
Internal over voltage
threshold of VOUT
5.3
V
100
µs
tS
Flash mode soft start time
RSETF = 9.1kΩ (Note 1)
Total output current, Torch
Mode
VENM = VCC, RSETM = 135kΩ,
D1+D2
Total output current, Flash
Mode
VENF = VCC = 3.8V, VENM = GND,
RSETF = 9.1kΩ, D1+D2
∆IOUT
Output current matching
(Note 2)
ISHORT
LED short checking
current
Current Sink
IOUT
90
100
110
mA
1.305
1.5
1.695
A
50mA/CH
2
10
%
750m/CH
2
10
%
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Rev. A, 04/23/2015
3.5
mA
5
IS31BL3233A
ELECTRICAL CHARACTERISTICS (CONTINUE)
The following specifications apply for VCC = 3.6V, TA = 25°C, unless otherwise noted.
Symbol
Description
Condition
Min.
Typ.
Max.
Units
0.4
V
Control
VIL
ENF, ENM pin logic low threshold
VIH
ENF, ENM pin logic high threshold
RPD_F
ENF Internal pull-down Resistance
300
kΩ
RPD_M
ENM Internal pull-down Resistance
300
kΩ
TOTP
IC junction thermal shutdown threshold
(Note 1)
150
°C
THYS
IC junction thermal shutdown hysteresis
(Note 1)
20
°C
1.4
V
Note 1: Guarantee by design.
Note 2: The current matching between channels is defined as I OUT
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
I D1  I D 2
I D1  I D 2
.
6
IS31BL3233A
TYPICAL PERFORMANCE CHARACTERISTICS
700
110
ID1 = ID2 = 100mA/CH
Torch Mode
Channel 2
Output Current (mA)
Output Current (mA)
105
ID1 = ID2 = 500mA/CH
Flash Mode
100
Channel 1
95
90
600
Channel 1
500
Channel 2
400
300
85
80
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
200
2.7
3.1
3.5
Supply Voltage vs. Output Current (Torch Mode)
Figure 4
100
Efficiency (%)
95
4.3
4.7
5.1
5.5
Supply Voltage (V)
Supply Voltage (V)
Figure 3
3.9
VENM
5V/Div
ID1+ID2 = 0.2A
Torch Mode
Supply Voltage vs. Output Current (Flash Mode)
VCC = 4.0V
ID1 = ID2 =100mA/CH
Torch Mode
90
ID1+ID2 = 0.6A
Flash Mode
ID1+ID2 = 1.5A
Flash Mode
85
VOUT
2V/Div
ID1+ID2 = 1.0A
Flash Mode
80
VD1
1V/Div
75
70
3.2
3.4
Figure 5
3.6
3.8
4
4.2
ID1
100mA/Div
Supply Voltage (V)
Time (100µs/Div)
Boost Efficiency vs. Supply Voltage
Figure 6
VCC = 3.6V
ID1 = ID2 = 750mA/CH
Flash Mode
VCC = 3.9V
ID1 = ID2 = 750mA/CH
Flash Mode
VENF
2V/Div
VENF
2V/Div
VCC
2V/Div
VCC
2V/Div
ID1
500mA/Div
ILX
1A/Div
Time (40µs/Div)
Time (40ms/Div)
Figure 7
Torch Mode Turn On/Off
Flash Mode Operation
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Rev. A, 04/23/2015
Figure 8
LX Current
7
IS31BL3233A
VENF
2V/Div
VENF
2V/Div
VOUT
2V/Div
VOUT
2V/Div
VD1
2V/Div
VD1
2V/Div
ID1
500mA/Div
Time (100µs/Div)
Figure 9
VCC = 3.4V
ID1 = ID2 =750mA/CH
Flash Mode With Boost
Flash Soft Start with Boost
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ID1
500mA/Div
Time (100µs/Div)
Figure 10
VCC = 3.8V
ID1 = ID2 = 750mA/CH
Flash Mode Without Boost
Flash Soft Start without Boost
8
IS31BL3233A
FUNCTIONAL BLOCK DIAGRAM
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IS31BL3233A
APPLICATION INFORMATION
FUNCTIONAL DESCRIPTION
The IS31BL3233A is a very high switching frequency
step-up (boost) flash LED driver. Two current
regulating devices are integrated to drive up to 2 flash
LEDs.
The voltage step-up is accomplished by a boost
topology, using an inductor-based DC-DC switching
converter, in which the inductor serves as an energy
storage device. By integrating optimized power
MOSFETs, the IS31BL3233A internal switching
frequency is 2.0MHz while still maintaining high power
efficiency. Unlike a traditional DC-DC boost converter
with a fixed output voltage, the IS31BL3233A
dynamically changes its output voltage depending on
the flash LED forward voltage and current. The use of
unique control schemes maintains accurate current
regulation in each of the two current sinks while leaving
the output voltage at a minimum, increasing the overall
conversion efficiency. The internal step-up converter
boosts the output voltage high enough to drive the
LEDs with the highest forward voltage. The two current
sinks can be shorted together to drive a higher current
single flash LED, sinking up to 1.5A combined.
The control interface is designed for maximum design
flexibility and compatibility with various types of system
controls. When the ENF is pulled high while the ENM is
low, the LED current will be ramped up to the Flash
Mode current level which is programmed by RSETF
resistor. When ENM is pulled high while the ENF is low,
the LED current will be ramped up to the Torch Mode
current level which is programmed by RSETM resistor.
However, if both ENM and ENF are high, the LED
current will be set to Torch Mode current. The driver IC
and the flash LEDs will be shutdown when both ENF
and ENM are at logic low.
CURRENT SETTING
Torch Mode Current
The Torch Mode LED current can be programmed up to
a maximum total current of 500mA or up to 250mA per
channel. Just as in Flash Mode operation, the output
currents in D1 and D2 are internally matched. The
Torch Mode current in each channel is set by the RSETM
resistor. For the desired Torch Mode current in each
output, the resistor value can be calculated using the
following Equation (2):
I D1  I D 2  6800 / RSETM
The Flash Mode LED current can be programmed up to
a maximum total current of 1.5A or up to 0.75A per
channel. The sink current in D1 and D2 are internally
matched in the IS31BL3233A. The Flash Mode current
in each channel is set by the RSETF resistor. For the
desired Flash Mode current in each output, the resistor
value can be calculated using the following Equation
(1):
(1)
A flash event is initiated by asserting the ENF pin while
ENM is at logic low level. A flash event is automatically
terminated when ENF is deasserted or when ENM is
asserted.
(2)
A Torch Mode event is initiated by asserting the ENM
pin. For additional flexibility, a lower Torch Mode
current than the value calculated above can be realized
by applying a PWM dimming signal at ENM pin while
ENF is held low. The average Torch Mode current will
be proportional to the PWM duty ratio.
SINGLE/DUAL LED APPLICATIONS
Each of the sinks’ (D1 and D2) current is regulated and
matched for applications requiring two LEDs. For
single LED applications, D1 and D2 can be connected
together to drive one LED (see Figure 11). The current
per sink follows the Equations (1) and (2) in Current
Setting sections above.
LX
1 H
VBattery
Flash Mode Current
I D1  I D 2  6800 / RSETF
enabled and the flash current is set to a high current
value, the temperature of the IC can increase quickly.
Once the IC’s temperature goes above 100°C, the two
sinks’ currents will be automatically decreased
according to the thermal regulation control loop. This
can prevent the IC from triggering thermal shutdown
and causing the LEDs to flicker. Depending on the
thermal layout of the PCB and the Flash Mode current
setting, the IS31BL3233A sink current can be lower
than the programmed value due to the thermal
regulation protection feature.
4
2.2 F
VCC
LX
5,6
0.1 F
8,9
10
Micro
Controller
11
VOUT
ENM
IS31BL3233A
1
RSETM
68k
RSETF
13.5k
2
3,13
COUT
4.7 F
ENF
D1
RSETM
RSETF
AGND
D2
PGND
12
14
7
Figure 11 Single LED Application
Automatic thermal regulation control is active when
IS31BL3233A is in Flash Mode. If Flash Mode is
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IS31BL3233A
forward voltage and maximum load current conditions):
LED SHORT PROTECTION
When the IS31BL3233A is enabled, there is a 2.5mA
(Typ.) LED sensing current through each current sink. It
is used to detect whether either LED is shorted by
generating a voltage drop through each LED. The IC
internally compares the voltage difference between
VOUT and each sink node (D1 and D2). If this
difference is below a preset threshold (Typ. 1.7V), the
IC will treat the respective LED as shorted and disable
its Flash/Torch Mode current through this LED channel.
However, the 2.5mA sensing current will be kept to
generate the LED’s voltage drop. If the short circuit is
removed during operation, the channel will
automatically recover to the programmed current
setting.
LED OPEN PROTECTION
In case of LED open, the open channel will control the
loop first so that VOUT will reach OVP, then
IS31BL3233A will automatically detect which channel’s
LED is open and disable that channel. From that point,
the other channel with properly operating LED will
control the loop and VOUT will be regulated down to a
normal operating voltage. This protection feature
avoids unnecessary power consumption in the current
sink by regulating the output voltage at the lowest level
possible to maintain regulation for the active channel.
Not only does this protect from open LEDs failures, but
also allows only single flash LED operation with the
unused channel floating or open. Open-circuit LED fault
protection is reset when the IC is powered down and up
again.
INDUCTOR SELECTION
The IS31BL3233A is designed to use a 1.0μH to
4.7μH inductor. To prevent core saturation, ensure that
the inductor-saturation current rating exceeds the peak
inductor current for the application. The worst-case
peak inductor current can be calculated with the
following formula:
I PEAK( L) 
VOUT( MAX)  I LED( MAX)
0.8 VIN(MIN)

VIN( MIN)  tON( MAX)
2 L
(3)
where 0.8 is the estimated efficiency of 80%.
For example, for a 1.0A total (or 0.5A per channel) LED
current, the peak inductor current for a 1.0uH inductor
could be as high as (estimated 50% as the maximum
duty ratio at the minimum input voltage, maximum LED
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Rev. A, 04/23/2015
I PEAK( L) 
4V 1A 3.5V  0.25

 1.9 A
0.8  3.5V
2 1
If the inductor value is smaller, the inductor peak
current will increase. To maintain stable operations for
the boost converter, the inductor peak current must be
less than both the IS31BL3233A current limit threshold
and the inductor saturation current rating.
Manufacturer’s specifications of inductors list both the
inductor DC current rating, which is a thermal limitation,
and peak inductor current rating, which is determined
by the saturation characteristics. Measurements at full
load and high ambient temperature should be
performed to ensure that the inductor does not saturate
or overheat due to its parasitic resistance. Bench
measurements are recommended to confirm actual
inductor peak current IPEAK and to ensure that the
inductor does not saturate at maximum LED current
and minimum input supply voltage.
CAPACITOR SELECTION
For good input voltage filtering low ESR ceramic
capacitors are recommended. At least a 2.2μF input
capacitor is recommended for high current flash LEDs
to improve transient behavior of the regulator and EMI
behavior of the total power supply circuit. The input
capacitor should be placed as close as possible to the
input pin and the PGND pin of the IS31BL3233A.
The output capacitance required depends on the
required LED current. A 4.7μF ceramic capacitor works
well in most situations, but a 1.0μF capacitor is
acceptable for lower LED current conditions.
PCB LAYOUT
Due to the fast switching transitions and high-current
paths, careful PC board layout is required. Connect
AGND pin directly to the exposed paddle underneath
the IC; connect the exposed paddle to the PCB ground
plane. The output bypass capacitor should be placed
as close to the IC as possible. Minimize trace lengths
between the IC and the inductor, the input capacitor,
and the output capacitor; keep these traces short,
direct, and wide. The ground connections of CIN and
COUT should be as close together as possible and
connected to PGND.
11
IS31BL3233A
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 12 Classification Profile
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12
IS31BL3233A
PACKAGE INFORMATION
DFN-14
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Rev. A, 04/23/2015
13
IS31BL3233A
LAND PATTERN
Note:
1. Land pattern complies to IPC-7351.
2. All dimensions in MM.
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