IS31BL3506A

IS31BL3506A
1.0MHZ BOOST CONVERTER WITH 35V INTERNAL MOSFET SWITCH
January 2014
GENERAL DESCRIPTION
FEATURES
IS31BL3506A is a boost converter featuring an
integrated MOSFET switch designed for driving series
strings of LED or other device. Input operating voltage
range is 2.7V~5.5V. The device regulates the LED load
current is set using an external, low value sensing
resistor. The device adjusts the PWM duty cycle of the
switch to maintain the voltage at the FB pin at a value
of 0.3V. The IS31BL3506A operates at a constant
switching frequency of 1.0MHz to allow for small
component size. IS31BL3506A features an over
voltage shutdown pin which prevents the output
voltage from exceeding 35V (typ.) in the case of an
open circuit condition. The device is offered in a tiny
TSOT-23-6, SOT-23-6 and DFN-8 (2mm×2mm)
package and a temperature rating from -40°C ~ +85°C.
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Supply voltage: 2.7V~5.5V
Built-in soft start
Drive series strings of
-9 LEDs (DFN-8)
-8 LEDs (TSOT-23-6, SOT-23-6)
PWM or DC voltage dimming
Frequency of PWM is 500Hz ~ 500kHz
1.0MHz high speed switching frequency
300mV feedback voltage
Integrated high power MOSFET
Over voltage protection
-40°C ~ +85°C working temperature range
TSOT-23-6, SOT-23-6 and DFN-8 (2mm×2mm)
package
APPLICATIONS
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Small LCD Backlights
Notebook PC
GPS
TYPICAL APPLICATION CIRCUIT
Figure 1
Constant current white LED driver using PWM at the EN pin to control intensity
Note 1: COUT must be rated for 50V. Smaller values of output capacitance will cause the LED current ripple to increase.
Note 2: The resistor REST should be placed as close as possible to the FB pin to prevent the EMI.
Note 3: Because of the different packages, VOVP is not the same (Page 6). 9 LEDs can be driven by DFN-8 package and 8 LEDs can be driven
by TSOT-23-6 and SOT-23-6 package most.
Note 4: The high level of PWM signal for EN pin should last at least 200ns when power on, or the IC won’t start up.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. C, 01/09/2014
1
IS31BL3506A
VBattery
2.7~5.5V
L1
10 H
D1
0.1 F
2.2 F
VCC
COUT
1 F
(50V)
LX
PWM Signal
OUT
Micro
Controller
(4~8)×2
LEDs
EN IS31BL3506A
FB
100k
RSET
7.5
GND
Figure 2
Constant current white LED driver using PWM at the EN pin to control intensity (4~8)×2 LEDs VBattery
2.7~5.5V
2.2 F
L1
10 H
D1
VOUT =VFB× (R1 +RSET)/RSET
0.1 F
VCC
LX
OUT
Micro
Controller
EN
COUT
1 F
(50V)
R1
Load
IS31BL3506A
FB
100k
RSET
GND
Figure 3
Figure 4
Constant output voltage for general purpose use
Constant output current with DC dimming input
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Rev. C, 01/09/2014
2
IS31BL3506A
Figure 5
Constant output current with PWM dimming control
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Rev. C, 01/09/2014
3
IS31BL3506A
PIN CONFIGURATION
Package
Pin Configurations (Top View)
TSOT-23-6
SOT-23-6
LX
1
6
VCC
GND
2
5
OUT
FB
3
4
EN
DFN-8
PIN DESCRIPTION
No.
Pin
Description
8
LX
Switch input, connect to the inductor.
2
6
GND
Ground.
3
5
FB
Feedback input pin.
4
4
EN
Device enable pin, active high.
5
3
OUT
Output voltage sense pin for over voltage
protection.
6
2
VCC
Supply voltage input pin.
-
7
NC
No connection.
-
1
PGND
Power ground. Connect independently.
Thermal Pad
Connect to GND.
TSOT-23-6
SOT-23-6
DFN-8
1
-
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Rev. C, 01/09/2014
4
IS31BL3506A
ORDERING INFORMATION
Industrial Range: -40°C to +85°C
Order Part No.
Package
IS31BL3506A-TTLS2-TR
TSOT-23-6, Lead-free
IS31BL3506A-STLS2-TR
SOT-23-6, Lead-free
IS31BL3506A-DLS2-TR
DFN-8, Lead-free
QTY/Reel
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
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Rev. C, 01/09/2014
5
IS31BL3506A
ABSOLUTE MAXIMUM RATINGS
Supply voltage, VCC
LX pin voltage
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 ~ +40V
-0.3V ~ +6.0V
150°C
-65°C ~ +150°C
-40°C ~ +85°C
2kV
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
Test conditions：TA = -40°C ~ +85°C, VCC = 3.6V, unless otherwise noted. Typical values at TA = 25°C.
Symbol
Parameter
Condition
Min
Typ
2.7
Max
Unit
5.5
V
VCC
Supply Voltage
ICC
Quiescent current
Switching
1.2
mA
ISD
Shutdown Current
VEN = 0V
1.5
μA
VEN_ON
EN Input logic High
VEN rising
VEN_OFF
EN Input logic Low
VEN falling
1.4
V
0.4
V
fOSC
Operating Frequency
1
MHz
DMAX
Maximum Duty Cycle
90
%
RDS_ON
LX Switch On resistance
0.8
Ω
ISW_LK
LS Switch Leakage current
VSW = 35V
Switch over current limit
Duty = 90%
ISW_LIMIT
1.8
2.2
TSOT-23-6, SOT-23-6
35
DFN-8
38
1
μA
2.6
A
VOVP
OUT over voltage protection
VFB
Feedback Voltage
0.3
V
TST
Over temperature protection (Note 1)
160
°C
tPWM_H
EN pin PWM high level time
(Note 1)
(when power on)
200
V
ns
Note 1: Guaranteed by design.
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Rev. C, 01/09/2014
6
IS31BL3506A
TYPICAL PERFORMANCE CHARACTERISTIC
0.35
100
90
0.3
Reference Voltage(V)
80
Efficiency(%)
70
60
50
40
30
0.25
0.2
0.15
0.1
20
8 WLEDs
ILED = 20mA
10
0
2. 8
3
3. 5
4
4. 5
8 WLEDs
ILED = 20mA
0.05
0
2.8
5
3
3.5
Figure 8
Efficiency vs. VCC
Power On from EN
Figure 9
14
PWM Dimming from EN
25
EN Pin Dimming
VEN = 2.8V
VCC = 4.2V
f = 5kHz
8WLEDs
Output Current(mA)
Output Current(mA)
16
5
VFB vs. VCC
Figure 7
20
18
4.5
Power Supply(V)
Power Supply(V)
Figure 6
4
12
10
8
6
FB Pin PWM Dimming
VPWM = 2.8V
VCC = 3.6V
f = 2kHz
8WLEDs
20
15
10
5
4
2
0
0
20
40
60
80
100
0
0
20
Enable Pin Dimming
Integrated Silicon Solution, Inc. – www.issi.com
Rev. C, 01/09/2014
60
80
100
Duty Cycle(%)
Duty Cycle(%)
Figure 10
40
Figure 11
FB pin PWM Dimming
7
IS31BL3506A
Figure 12
Ripple Voltage
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Rev. C, 01/09/2014
8
IS31BL3506A
FUNCTIONAL BLOCK DIAGRAM
LX
VCC
Band Gap
Bias&Ref
FB
Vref
R
Slope
Compensation
OSC
S
Q
Σ
Ramp
Generater
GND
Current
Limite
Thermal
Shutdown
Block
OVP
OUT
EN
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Rev. C, 01/09/2014
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IS31BL3506A
APPLICATION INFORMATION
INPUT AND OUTPUT CAPACITOR
FB PIN DC VOLTAGE DIMMING
A 2.2μF input capacitor is used to reduce input ripple
and noise, where the input ripple amplitude is inversely
proportional to the value of the input capacitance. The
input and output capacitors should be placed as close
to the device as possible, so as to reduce the effect of
voltage ripple. The value of the output capacitor is
dependent upon the output ripple. A 1μF or 0.22μF
ceramic capacitor with a 50V rating is sufficient for the
majority of applications.
The schematic of Figure 4 show an example of using a
DC input voltage at the FB pin to implement LED
dimming. When the DC input voltage increases, the
current through R2 and R3 increases producing an
offset voltage across R2, thereby causing the LED
current to be reduced. The LED current may be
computed using the following equation, (3). VFB is 0.3V
(typ).
VFB 
INDUCTOR VALUE
The choice of the inductor value will affect the
performance of the device. Large value inductors will
reduce the current ripple in the inductor, thus reducing
output voltage ripple. However large value inductors of
the same current rating, typically also have larger DC
resistance, thus reducing the system efficiency. For the
majority of applications 4.7μH or 10μH is sufficient.
LED CURRENT SETPOINT
When the IS31BL3506A is used for LED driving
applications (Figure 1), the LED current flows through
the external feedback resistor RSET to regulate the LED
current. The internal feedback regulation point is 0.3V.
The maximum LED current may be calculated by the
following equation, (1).
I MAX  VFB / RSET
(1)
For accurate LED current, resistors should be 1% or
better tolerance.
LED INTENSITY CONTROL
I LED 
FB PIN PWM DIMMING
A PWM signal connected to the FB pin can also be
used to directly control the LED current (Figure 5). A
low pass filter converts the PWM duty cycle to a DC
level, which is in turn summed together with the
feedback voltage of RSET to effectively reduce the
LED current proportionally. Due to the filtering of the
PWM signal, the frequency of the PWM signal can
have an affect on the output voltage ripple. For a PWM
signal input signal of 2.8V, the recommended
frequency is greater than 2kHz. Using a fixed
frequency PWM signal and adjusting the PWM duty
cycle effectively adjusts the LED intensity. LED current
may be computed using the following equation, (4).
VFB is 0.3V (typ).
VFB 
I LED  I MAX  DPWM
(2)
IMAX is computed using equation (1). Recommended
PWM frequency is in the range of 500Hz ~ 500kHz. So
as to guarantee a reasonably good dimming effect, the
minimum duty cycle should be about 1%.
Driving the EN pin with a PWM signal can effectively
adjust the LED intensity. The PWM signal voltage
levels must meet the EN pin input voltage levels,
VEN_ON and VEN_OFF.
IS31BL3506A can also use a DC voltage or PWM
signal to directly control the LED current, and thus
provide fine adjustment for the LED intensity.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. C, 01/09/2014
（3）
When the DC voltage range is 0V~1.8V, a good value
for R2 is 75kΩ，and for R3 is 360kΩ.
EN PIN DIMMING
The EN pin of the IS31BL3506A can accept a PWM
signal to implement LED dimming (Figure 1). LED
current may be computed using the following equation,
(2).
R2  (VDC  VFB )
R3
RSET
I LED 
R2  (VPWM  Duty  VFB )
R4  R3
RSET
（4）
For a PWM signal range of 0V~1.8V, a suitable value
for R2 is 75kΩ, R3 is 150kΩ, R4 is 200kΩ. To ensure
good dimming effect, the minimum duty cycle is about
10%.
SETTING THE OUTPUT VOLTAGE
The IS31BL3506A can be configured to provide a
constant output voltage (Figure 3). The output voltage
level can be computed using the following equation,
(5). The device internal VFB is 0.3V (typ).
VOUT  VFB  R1  RSET  / RSET
（5）
OVERVOLTAGE THRESHOLD
Device open circuit protection is realized using the
overvoltage protection function (OVP). If the output
voltage surpasses the overvoltage threshold, the
overvoltage protection circuit is activated and the
device will stop working.
10
IS31BL3506A
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 13
Classification Profile
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Rev. C, 01/09/2014
11
IS31BL3506A
PACKAGE OUTLINE DRAWING
TSOT-23-6
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Rev. C, 01/09/2014
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IS31BL3506A
SOT-23-6
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Rev. C, 01/09/2014
13
IS31BL3506A
DFN-8
Note: All dimensions in millimeters unless otherwise stated.
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Rev. C, 01/09/2014
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