XPGBWT-L1-0000-00K53 - CREE

IS31BL3506B

Integrated Silicon Solution, Inc. – www.issi.com

Rev. A, 04/15/2013

1.0MHZ BOOST CONVERTER WITH 35V INTERNAL MOSFET SWITCH

April 2013

GENERAL DESCRIPTION

IS31BL3506B 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 0.2V. The IS31BL3506B operates at a constant

switching frequency of 1.0MHz to allow for small

component size. IS31BL3506B 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 and SOT-23-6 package and a temperature

rating from -40°C ~ +85°C.

FEATURES

 Supply voltage: 2.7V~5.5V

 Built-in soft start

 Drive series strings of 8 LEDs

 PWM or DC voltage dimming

 Frequency of PWM is 500Hz ~ 500kHz

 1.0MHz high speed switching frequency

 200mV feedback voltage

 Integrated high power MOSFET

 Over voltage protection

 -40°C ~ +85°C working temperature range

 TSOT-23-6 and SOT-23-6 package

APPLICATIONS

 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: The high level of PWM signal for EN pin should last at least 200ns when power on, or the IC won’t start up.

IS31BL3506B

Integrated Silicon Solution, Inc. – www.issi.com

Rev. A, 04/15/2013



OUT

LXVCC

GND

IS31BL3506B

100k

10 H

0.1 F

VBattery

2.7~5.5V

2.2 F

Micro

Controller

PWM Signal

RSET

COUT

1 F

(50V) (4~6)×2

LEDs



Figure 2 Constant current white LED driver using PWM at the EN pin to control intensity (4~6)×2 LEDs

OUT

LXVCC

GND

IS31BL3506B

10 H

0.1 F

2.2 F

R1Load

RSET

VOUT =VFB× (R1+RSET)/RSET

VBattery

2.7~5.5V

100k

Micro

Controller

COUT

1 F

(50V)

Figure 3 Constant output voltage for general purpose use

Figure 4 Constant output current with DC dimming input

IS31BL3506B

Integrated Silicon Solution, Inc. – www.issi.com

Rev. A, 04/15/2013

Figure 5 Constant output current with PWM dimming control

IS31BL3506B

Integrated Silicon Solution, Inc. – www.issi.com

Rev. A, 04/15/2013

PIN CONFIGURATION

Package Pin Configurations (Top View)

TSOT-23-6

SOT-23-6

OUT

VCC

GND

PIN DESCRIPTIO N

No. Pin Description

1 LX Switch input, connect to the inductor.

2 GND Ground.

3 FB Feedback input pin.

4 EN Device enable pin, active high.

5 OUT Output voltage sense pin for over voltage protection.

6 VCC Supply voltage input pin.

IS31BL3506B

Integrated Silicon Solution, Inc. – www.issi.com

Rev. A, 04/15/2013

ORDERING INFORMATION

Industrial Range: -40°C to +85°C

Order Part No. Package QTY/Reel

IS31BL3506B-TTLS2-TR

IS31BL3506B-STLS2-TR

TSOT-23-6, Lead-free

SOT-23-6, Lead-free 3000

Copyright©2013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

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IS31BL3506B

Integrated Silicon Solution, Inc. – www.issi.com

Rev. A, 04/15/2013

ABSOLUTE MAXIMUM RATINGS

Supply voltage, VCC -0.3V ~ +6.0V

LX pin voltage -0.3V ~ +40V

Voltage at any input pin -0.3V ~ +6.0V

Maximum junction temperature, TJMAX 150°C

Storage temperature range, TSTG -65°C ~ +150°C

Operating temperature range, TA -40°C ~ +85°C

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 Max Unit

VCC Supply voltage 2.7 5.5 V

ICC Quiescent current Switching 1.2 mA

ISD Shutdown current VEN = 0V 5.5 μA

VEN_ON EN Input logic High VEN rising 1.4 V

VEN_OFF EN Input logic Low VEN falling 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 1 μA

ISW_LIMIT Switch over current limit Duty = 90% 1.8 2.2 2.6 A

VOVP OUT over voltage protection 35 V

VFB Feedback voltage 0.2 V

TST Over temperature protection (Note 1) 160 °C

tPWM_H EN pin PWM high level time

(when power on) (Note 1) 200 ns

Note 1: Guaranteed by design.

IS31BL3506B

Integrated Silicon Solution, Inc. – www.issi.com

Rev. A, 04/15/2013

TYPICAL PERFORMANCE CHARACTERISTIC

Power Supply(V)

Efficiency(%)

100

2.5 3 3.5 4 4.5 5 5.5

8 WLEDs

LED

= 20mA

Figure 6 Efficiency vs. VCC

Figure 8 Power On from EN

Duty Cycle(%)

Output Current(mA)

020406080100

EN Pin Dimming

VEN = 2.8V

VCC = 3.6V

f = 20kHz

8WLEDs

Figure 10 Enable Pin Dimming

Power Supply(V)

Reference

oltage(V)

0.05

0.1

0.15

0.2

0.25

0.3

2.5 3 3.5 4 4.5 5 5.5

8 WLEDs

LED

= 20mA

Figure 7 V

FB vs. VCC

Figure 9 PWM Dimming from EN

Duty Cycle(%)

Output Current(mA)

020406080100

FB Pin PWM Dimming

PWM

= 2.8V

= 3.6V

f = 20kHz

8WLEDs

Figure 11 FB pin PWM Dimming

IS31BL3506B

Integrated Silicon Solution, Inc. – www.issi.com

Rev. A, 04/15/2013

Figure 12 Ripple Voltage

IS31BL3506B

Integrated Silicon Solution, Inc. – www.issi.com

Rev. A, 04/15/2013

FUNCTIONAL BLOCK DIAGRAM

Bias&Ref

Current

Limite

OVP

Band Gap

Shutdown

Block

Slope

Compensation

Ramp

Generater

OSC

Thermal

Vref

OUT

VCC

GND

IS31BL3506B

Integrated Silicon Solution, Inc. – www.issi.com

Rev. A, 04/15/2013

APPLICATION INFORMATION

INPUT AND OUTPUT CAP ACIT OR

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.

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 IS31BL3506B 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 0.2V.

The maximum LED current may be calculated by the

following equation, (1).

SETFBMAX RVI / (1)

For accurate LED current, resistors should be 1% or

better tolerance.

LED INTENSITY CONTROL

EN PIN DIMMING

The EN pin of the IS31BL3506B can accept a PWM

signal to implement LED dimming (Figure 1). LED

current may be computed using the following equation,

(2).

PWMMAXLED DII  (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.

IS31BL3506B can also use a DC voltage or PWM

signal to directly control the LED current, and thus

provide fine adjustment for the LED intensity.

FB PIN DC VOLTAGE DIMMING

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 0.2V

(typ.).

SET

FBDC

LED RRVVR

2)( 





 （3）

When the DC voltage range is 0V~1.8V, a good value

for R2 is 56kΩ, and for R3 is 400kΩ.

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 0.2V (typ.).

SET

FBPWM

LED RRR VDutyVR

I34

2)(









 （4）

For a PWM signal range of 0V~1.8V, a suitable value

for R2 is 56kΩ, R3 is 200kΩ, R4 is 200kΩ. To ensure

good dimming effect, the minimum duty cycle is about

10%.

SETTING THE OUTPUT VOLTAGE

The IS31BL3506B 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 0.2V (typ).





SETSETFBOUT RRRVV /







（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.

IS31BL3506B

Integrated Silicon Solution, Inc. – www.issi.com

Rev. A, 04/15/2013

CLASSIFICATION REFLOW PROFI LES

Profile Feature Pb-Free Assembly

Preheat & S oak

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

IS31BL3506B

Integrated Silicon Solution, Inc. – www.issi.com

Rev. A, 04/15/2013

PACKAGE OUTLINE DRAWING

TSOT-23-6

IS31BL3506B

Integrated Silicon Solution, Inc. – www.issi.com

Rev. A, 04/15/2013

SOT-23-6

Note: All dimensions in millimeters unless otherwise stated.