LM3530UMX-40NOPB_技术文档

August 20, 2011

LM3530

High Efficiency White LED Driver with Programmable

Ambient Light Sensing Capability and I²C-Compatible

Interface

General Description

Features

The LM3530 current mode boost converter supplies the pow-

er and controls the current in up to 11 series white LED’s. The

839mA current limit and 2.7V to 5.5V input voltage range

make the device a versatile backlight power source ideal for

operation in portable applications.

Drives up to 11 LED’s in series

■

1000:1 Dimming Ratio

90% Efficient

Programmable Dual Ambient Light Sensor Inputs with

internal ALS Voltage Setting Resistors

The LED current is adjustable from 0 to 29.5mA via an I²C-

compatible interface. The 127 different current steps and 8

different maximum LED current levels give over 1000 pro-

grammable LED current levels. Additionally, PWM brightness

control is possible through an external logic level input.

I²C Programmable Logarithmic or Linear Brightness

Control

■

External PWM Input for Simple Brightness Adjustment

■

True Shutdown Isolation for LED's and Ambient Light

Sensors

The device also features two Ambient Light Sensor inputs.

These are designed to monitor analog output ambient light

sensors and provide programmable adjustment of the LED

current with changes in ambient light. Each ambient light sen-

sor input has independently programmable internal voltage

setting resistors which can be made high impedance to re-

duce power during shutdown. The LM3530's 500kHz switch-

ing frequency allows for high converter efficiency over a wide

output voltage range accommodating from 2 to 11 series

LEDs. Finally, the support of Content Adjusted Backlighting

maximizes battery life while maintaining display image quali-

ty.

Internal Soft-Start Limits Inrush Current

■

Wide 2.7V to 5.5V Input Voltage Range

40V and 25V Over-Voltage Protection Options

500kHz Fixed Frequency Operation

839mA Peak Current Limit

Low-Profile 12-bump micro SMD Package

Applications

Smartphone LCD Backlighting

■

Personal Navigation LCD Backlighting

The LM3530 is available in a tiny 12-bump (1.6mm × 1.2mm

× 0.425mm) micro SMD package and operates over the −40°

C to +85°C temperature range.

2 to 11 series White LED Backlit Display Power Source

Typical Application Circuit

30086601

300866

www.national.com

LM3530 Layout Example

30086683

Connection Diagram

12-Bump (1.215mm × 1.615mm x XXXmm) UMD12AAA (X³X⁰⁰X⁸⁶⁶=⁰²0.425mm), TMD12AAA (XXX = 0.625mm)

Ordering Information

Order Number

Package

Type

Supplied As

Lead

Top Mark

Description

Free? (2 lines: first line (XX) is date code

and die run code, second line is

voltage option)

LM3530UME-25A

NOPB

12-Bump 250 units, Tape-and-

micro SMD Reel, No Lead

(UMD12)

Yes

XX

DS

25V OVP,

I²C Address 0x36

LM3530UMX-25A

NOPB

12-Bump 3000 units, Tape-and- Yes

micro SMD Reel, No Lead

(UMD12)

XX

DS

25V OVP

I²C Address 0x36

LM3530UME-40

NOPB

12-Bump 250 units, Tape-and-

micro SMD Reel, No Lead

(UMD12)

Yes

XX

40

40V OVP

I²C Address. 0x38

LM3530UMX-40

NOPB

12-Bump 3000 units, Tape-and- Yes

micro SMD Reel, No Lead

(UMD12)

XX

40

40V OVP

I²C Address 0x38

LM3530UME-40B

NOPB

12-Bump 250 units, Tape-and-

micro SMD Reel, No Lead

(UMD12)

Yes

XX

DT

40V OVP

I²C Address 0x39

www.national.com

2

Order Number

Package

Type

Supplied As

Lead

Top Mark

Description

Free? (2 lines: first line (XX) is date code

and die run code, second line is

voltage option)

LM3530UMX-40B

NOPB

12-Bump 3000 units, Tape-and- Yes

micro SMD Reel, No Lead

(UMD12)

XX

DT

40V OVP

I²C Address 0x39

LM3530TME-40

NOPB

12-Bump 250 units, Tape-and-

micro SMD Reel, No Lead

(TMD12)

Yes

XX

DX

40V OVP

I²C Address 0x38

LM3530TMX-40

NOPB

12-Bump 3000 units, Tape-and- Yes

micro SMD Reel, No Lead

(TMD12)

XX

DX

40V OVP

I²C Address 0x38

Pin Descriptions/Functions

Name

Description

C3

IN

Input Voltage Connection. Connect a 2.7V to 5.5V supply to IN and bypass to GND with a 2.2µF

or greater ceramic capacitor.

D2

A3

OVP

SW

Output Voltage Sense Connection for Over-Voltage Sensing. Connect OVP to the positive

terminal of the output capacitor.

Inductor Connection, Diode Anode Connection, and Drain Connection for Internal NFET.

Connect the inductor and diode as close as possible to SW to reduce parasitic inductance and

capacitive coupling to nearby traces.

D3

D1

A1

A2

B3

C1

B1

B2

C2

ILED

ALS1

SDA

Input Terminal to Internal Current Sink. The boost converter regulates ILED to 0.4V.

Ambient Light Sensor Input #1 with Programmable Internal Pull-down Resistor.

Serial Data Connection for I²C-Compatible Interface.

SCL

Serial Clock Connection for I²C-Compatible Interface.

GND

ALS2

PWM

INT

Ground

Ambient Light Sensor Input #2 with Programmable Internal Pull-down Resistor.

External PWM Brightness Control Input and Simple Enable Input.

Logic Interrupt Output Signaling the ALS Zone Has Changed.

Active High Hardware Enable (Active Low Reset). Pull this pin high to enable the LM3530.

HWEN

3

www.national.com

Absolute Maximum Ratings (Note 1, Note

2)

Operating Ratings (Note 1, Note 2)

V_INto GND

2.7V to 5.5V

V_SW, V_OVP, V_ILED, to GND

0 to +40V

−40°C to +125°C

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales Office/

Distributors for availability and specifications.

Junction Temperature Range

(T_J) (Note 4)

Ambient Temperature Range

(T_A) (Note 5)

−40°C to +85°C

V_INto GND

−0.3V to +6V

−0.3V to 45V

V_SW, V_OVP, V_ILEDto GND

V_SCL, V_SDA, V_ALS1, V_PWM, V_INT

V_HWENto GND

,

Thermal Properties

−0.3V to +6V

-0.3V to V_IN+ 0.3V

Internally Limited

+150°C

Junction to Ambient Thermal

61.7°C/W

V_ALS2to GND

Resistance (T_JA)(Note 6)

Continuous Power Dissipation

Junction Temperature (T_J-MAX

)

ESD Caution Notice

Storage Temperature Range

−65°C to +150°C

National Semiconductor recommends that all integrated cir-

cuits be handled with appropriate ESD precautions. Failure to

observe proper ESD handling techniques can result in dam-

age to the device.

Maximum Lead Temperature

(Soldering, 10s)

ESD Rating (Note 9) Human

(Note 3)

Body Model

2.0kV

Electrical Characteristics (Note 2, Note 7)

Limits in standard type face are for T_A= +25°C and those in boldface type apply over the full operating ambient temperature range

(−40°C ≤ T_A≤ +85°C). Unless otherwise specified V_IN= 3.6V.

Symbol

I_LED

Parameter

Conditions

Min

Typ

Max

Units

Output Current Regulation

17.11

18.6

20.08

mA

2.7V ≥ V_IN≥ 5.5V, Full-Scale

Current = 19mA, BRT Code =

0x7F, ALS Select Bit = 0, I2C

Enable = 1

V_{REG_CS}

V_HR

R_DSON

I_CL

Regulated Current Sink

Headroom Voltage

400

200

0.25

mV

Ω

Current Sink Minimum

Headroom Voltage

I_LED= 95% of nominal

I_SW= 100 mA

NMOS Switch On

Resistance

NMOS Switch Current Limit

2.7V ≤ V_IN≤ 5.5V

Note: (Note 10)

739

40

839

41

936

42

mA

ON Threshold, 40V version

2.7V ≤ V_IN≤

5.5V

25V version

Output Over-Voltage

Protection

V_OVP

23.6

24

24.6

V

Hysteresis

1

f_SW

Switching Frequency

450

500

94

550

kHz

%

2.7V ≤ V_IN≤ 5.5V

D_MAX

D_MIN

I_Q

Maximum Duty Cycle

Minimum Duty Cycle

10

%

Quiescent Current, Device V_HWEN= V_IN

Not Switching

490

1.35

1

600

2

µA

mA

µA

I_{Q_SW}

I_SHDN

Switching Supply Current

Shutdown Current

I_LED= 19mA, V_OUT= 36V

V_HWEN= GND, 2.7V ≥ V_IN≥

5.5V

I_{LED_MIN}

Minimum LED Current

Full-Scale Current = 19mA

setting

9.5

1

µA

V

BRT = 0x01

V_ALS

Ambient Light Sensor

Reference Voltage

2.7V ≥ V_IN≥ 5.5V (Note 11)

0.97

1.03

www.national.com

4

Symbol

Parameter

Conditions

Min

0

Typ

Max

0.4

Units

Logic Thresholds - Logic

Low

V_HWEN

V

Logic Thresholds - Logic

High

V_IN

1.2

T_SD

Thermal Shutdown

Hysteresis

+140

15

°C

12.77

8.504

5.107

2.143

1.836

1.713

1.510

1.074

0.991

0.954

0.888

0.717

0.679

0.661

0.629

13.531

9.011

5.411

2.271

1.946

1.815

1.6

14.29

9.518

5.715

2.399

2.055

1.917

1.69

RALS1,

RALS2

ALS Input Internal Pull-down

Resistors

1.138

1.050

1.011

0.941

0.759

0.719

0.700

0.666

1.202

1.109

1.068

0.994

0.802

0.760

0.740

0.704

2.7V ≥ V_IN≥ 5.5V

kΩ

Logic Voltage Specifications (SCL, SDA, PWM, INT)

V_IL

Input Logic Low

Input Logic High

0

0.54

V_IN

V

2.7V ≤ V_IN≤ 5.5V

V_IH

1.26

V_OL

Output Logic Low (SDA, INT) I_LOAD= 3 mA

400

mV

I²C-Compatible Timing Specifications (SCL, SDA) (Note 8)

t₁

t₂

SCL (Clock Period)

2.5

µs

ns

Data In Setup Time to SCL

High

100

t₃

Data Out Stable After SCL

Low

0

ns

SDA Low Setup Time to SCL

Low (Start)

t₄

100

t₅

SDA High Hold Time After

SCL High (Stop)

Simple Interface (PWM pin)

t_{PWM_HIGH}Enable time, PWM pin must

1.5

2

2.6

be held high

ms

t_{PWM_LOW}

Disable time, PWM pin must

be held low

1.48

2.69

5

www.national.com

Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions for which the device is intended

to be functional, but device parameter specifications may not be guaranteed. For guaranteed specifications and test conditions, see the Electrical Characteristics

table.

Note 2: All voltages are with respect to the potential at the GND pin.

Note 3: For detailed soldering specifications and information, please refer to National Semiconductor Application Note 1112: Micro SMD Wafer Level Chip Scale

Package (AN-1112), available at www.national.com.

Note 4: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at T_J=+140°C (typ.) and disengages at

T_J=+125°C (typ.).

Note 5: In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be

derated. Maximum ambient temperature (T_A-MAX) is dependent on the maximum operating junction temperature (T_J-MAX-OP= +125°C), the maximum power

dissipation of the device in the application (P_D-MAX), and the junction-to ambient thermal resistance of the part/package in the application (θ_JA), as given by the

following equation: T_A-MAX= T_J-MAX-OP– (θ_JA× P_D-MAX).

Note 6: Junction-to-ambient thermal resistance (θ_JA) is taken from a thermal modeling result, performed under the conditions and guidelines set forth in the

JEDEC standard JESD51-7. The test board is a 4-layer FR-4 board measuring 102mm x 76mm x 1.6mm with a 2 x 1 array of thermal vias. The ground plane on

the board is 50mm x 50mm. Thickness of copper layers are 36µm/18µm/18µm/36µm (1.5oz/1oz/1oz/1.5oz). Ambient temperature in simulation is 22°C in still air.

Power dissipation is 1W. The value of θ_JAof this product in the micro SMD package could fall in a range as wide as 60ºC/W to 110ºC/W (if not wider), depending

on PCB material, layout, and environmental conditions. In applications where high maximum power dissipation exists special care must be paid to thermal

dissipation issues.

Note 7: Min and Max limits are guaranteed by design, test, or statistical analysis. Typical (typ.) numbers are not guaranteed, but represent the most likely norm.

Note 8: SCL and SDA must be glitch-free in order for proper brightness control to be realized.

Note 9: The human body model is a 100pF capacitor discharged through 1.5kΩ resistor into each pin. (MIL-STD-883 3015.7).

Note 10: The value for current limit given in the Electrical Table is measured in an open loop test by forcing current into SW until the current limit comparator

threshold is reached. The typical curve for current limit is measured in closed loop using the typical application circuit by increasing IOUT until the peak inductor

current stops increasing. Closed loop data appears higher due to the delay between the comparator trip point and the NFET turning off. This delay allows the

closed loop inductor current to ramp higher after the trip point by approximately 100ns × VIN/L

Note 11: The ALS voltage specification is the maximum trip threshold for the ALS zone boundary (Code 0xFF). Due to random offsets and the mechanism for

which the hysteresis voltage varies, it is recommended that only Codes 0x04 and above be used for Zone Boundary Thresholds. See Zone Boundary Trip Points

and Hysteresis and Minimum Zone Boundary Settings sections.

www.national.com

6

Timing Diagrams

30086603

FIGURE 1. I²C-Compatible Timing

30086604

FIGURE 2. Simple Enable/Disable Timing

7

www.national.com

Typical Performance Characteristics V_IN= 3.6V, LEDs are OVSRWAC1R6 from OPTEK Technology,

C_OUT= 1µF, C_IN= 1µF, L = TDK VLF5012ST-100M1R0, (R_L= 0.24Ω), I_LED= 19mA, T_A= +25°C unless otherwise specified.

Efficiency vs V_IN(I_{FULL_SCALE}= 19mA)

30086651

30086652

Efficiency vs V_IN(I_{FULL_SCALE}= 19mA)

Efficiency vs I_LED(V_IN= 3.6V)

30086653

30086654

Efficiency vs I_LED(V_IN= 3.6V)

30086654

30086655

www.national.com

8

LED Current vs V_IN(19mA Full-Scale Setting)

Shutdown Current vs V_IN

30086675

30086679

Internal ALS Resistor vs V_IN(T_A= +25°C)

ALS Resistor Select Register = 0x44

Internal ALS Resistor vs V_IN(T_A= +85°C)

ALS Resistor Select Register = 0x44

30086657

30086658

Internal ALS Resistor vs V_IN(T_A= −40°C)

ALS Resistor Select Register = 0x44

Current Limit vs V_IN(Closed Loop, L = 22µH (Note 10))

30086673

30086659

9

www.national.com

Over Voltage Protection vs V_IN(V_OUTRising)

Max Duty Cycle vs V_IN

Switching Frequency vs V_IN

Simple Disable Time vs V_IN

30086660

30086676

30086677

30086682

NFET Switch On-Resistance vs V_IN

30086678

Simple Enable Time vs V_IN

30086680

www.national.com

10

I_LEDvs f_PWM

(50% duty cycle, I_LEDFull Scale = 19mA)

Ramp Rate (Exponential)

(1.024ms/step up and down)

30086689

Channel 2: SDA (5V/div)

Channel 3: ILED (10mA/div)

Time Base (40ms/div)

30086699

Ramp Rate (Exponential)

(2.048ms/step up and down)

Ramp Rate (Exponential)

(4.096ms/step up and down)

30086690

30086691

Channel 2: SDA (5V/div)

Channel 3: ILED (10mA/div)

Time Base (100ms/div)

Channel 3: ILED (10mA/div)

Time Base (200ms/div)

Ramp Rate (Exponential)

(8.192ms/step up and down)

Ramp Rate (Exponential)

(16.384ms/step up and down)

30086693

30086692

Channel 2: SDA (5V/div)

Channel 3: ILED (10mA/div)

Time Base (1s/div)

Channel 3: ILED (10mA/div)

Time Base (400ms/div)

11

www.national.com

Ramp Rate (Exponential)

(32.768ms/step up and down)

Ramp Rate (Exponential)

(65.538ms/step up and down)

30086695

30086694

Channel 2: SDA (5V/div)

Channel 3: ILED (10mA/div)

Time Base (4s/div)

Channel 3: ILED (10mA/div)

Time Base (2s/div)

Startup Plot

Line Step Response

(V_INfrom 3.6V to 3.2V, ILED = 19mA, L = 22µH)

(V_IN= 3.6V, ILED = 19mA, L = 22µH, Ramp Rate = 8µs/step)

30086696

30086697

Channel 1: IIN (200mA/div)

Channel 1: VIN (500mV/div)

Channel 3: VOUT (20V/div)

Channel 4 (10mA/div)

Time Base (2ms/div)

Channel 2: VOUT (500mV/div)

Channel 3: ILED (500µA/div)

Time Base (400µs/div)

I_LEDResponse to Step Change in PWM Duty Cycle

(D_PWMfrom 30% to 70%, I_LEDFull Scale = 19mA, f_PWM= 5kHz)

30086698

Channel 4: ILED (5mA/div)

Channel 2: PWM (5V/div)

Time Base (2ms/div)

www.national.com

12

to maintain regulation at the output. Light load operation pro-

vides for improved efficiency at lighter LED currents com-

pared to continuous and discontinuous conduction. This is

due to the pulsed frequency operation resulting in decreased

switching losses in the boost converter.

Operational Description

The LM3530 utilizes an asynchronous step-up, current mode,

PWM controller and regulated current sink to provide an effi-

cient and accurate LED current for white LED bias. The device

powers a single series string of LEDs with output voltages of

up to 40V and a peak inductor current of typically 839mA. The

input active voltage range is from 2.7V to 5.5V.

AMBIENT LIGHT SENSOR

The LM3530 incorporates a dual input Ambient Light Sensing

interface (ALS1 and ALS2) which translates an analog output

ambient light sensor to a user-specified brightness level. The

ambient light sensing circuit has 4 programmable boundaries

(ZB0 – ZB3) which define 5 ambient brightness zones. Each

ambient brightness zone corresponds to a programmable

brightness threshold (Z0T – Z4T). The ALS interface is pro-

grammable to accept the ambient light information from either

the highest voltage of ALS1 or ALS2, the average voltage of

ALS1 or ALS2, or selectable from either ALS1 or ALS2.

STARTUP

An internal soft-start prevents large inrush currents during

startup that can cause excessive current spikes at the input.

For the typical application circuit (using a 10µH inductor, a

2.2µF input capacitor, and a 1µF output capacitor) the aver-

age input current during startup ramps from 0 to 300mA in

3ms. See Start Up Plots in the Typical Performance Charac-

teristics.

Furthermore, each ambient light sensing input (ALS1 or

ALS2) features 15 internal software selectable voltage setting

resistors. This allows the LM3530 the capability of interfacing

with a wide selection of ambient light sensors. Additionally,

the ALS inputs can be configured as high impedance, thus

providing for a true shutdown during low power modes. The

ALS resistors are selectable through the ALS Resistor Select

Register (see Table 9). Figure 3 shows a functional block di-

agram of the ambient light sensor input. VSNS represents the

active input as described in Table 6 bits [6:5].

LIGHT LOAD OPERATION

The LM3530's boost converter operates in three modes: con-

tinuous conduction, discontinuous conduction, and skip

mode. Under heavy loads when the inductor current does not

reach zero before the end of the switching period, the device

switches at a constant frequency (500kHz typical). As the

output current decreases and the inductor current reaches

zero before the end of the switching period, the device oper-

ates in discontinuous conduction. At very light loads the

LM3530 will enter skip mode operation causing the switching

period to lengthen and the device to only switch as required

30086607

FIGURE 3. Ambient Light Sensor Functional Block Diagram

ALS OPERATION

the LED current to the new 7 bit brightness level as pro-

grammed into the appropriate Zone Target Register (Z0T –

Z4T) (see Figure 4).

The ambient light sensor input has a 0 to 1V operational input

voltage range. The Typical Application Circuit shows the

LM3530 with dual ambient light sensors (AVAGO,

APDS-9005) and the internal ALS Resistor Select Register

set to 0x44 (2.27kΩ). This circuit converts 0 to 1000 LUX light

into approximately a 0 to 850mV linear output voltage. The

voltage at the active ambient light sensor input (ALS1 or

ALS2) is compared against the 8 bit values programmed into

the Zone Boundary Registers (ZB0-ZB3). When the ambient

light sensor output crosses one of the ZB0 – ZB3 programmed

thresholds the internal ALS circuitry will smoothly transition

The ALS Configuration Register bits [6:5] programs which in-

put is the active input, bits [4:3] control the on/off state of the

ALS circuitry, and bits [2:0] control the ALS input averaging

time. Additionally, the ALS Information Register is a read-only

register which contains a flag (bit 3) which is set each time the

active ALS input changes to a new zone. This flag is reset

when the register is read back. Bits [2:0] of this register con-

tain the current active zone information.

13

www.national.com

30086608

FIGURE 4. Ambient Light Input to Backlight Mapping

ALS AVERAGING TIME

if during an averaging period the ALS input transitions

between zone's 1 and 2 resulting in an averager output

of 1.75, then the averager output will round down to 1

(see Figure 5).

The ALS Averaging Time is the time over which the Averager

block collects samples from the A/D converter and then av-

erages them to pass to the discriminator block (see Figure

3). Ambient light sensor samples are averaged and then fur-

ther processed by the discriminator block to provide rejection

of noise and transient signals. The averager is configurable

with 8 different averaging times to provide varying amounts

of noise and transient rejection (see Table 5). The discrimi-

nator block algorithm has a maximum latency of two averag-

ing cycles; therefore, the averaging time selection determines

the amount of delay that will exist between a steady-state

change in the ambient light conditions and the associated

change of the backlight illumination. For example, the A/D

converter samples the ALS inputs at 16kHz. If the averaging

time is set to 1024ms then the Averager will send the updated

zone information to the discriminator every 1024ms. This

zone information contains the average of 16384 samples

(1024ms × 16kHz). Due to the latency of 2 averaging cycles,

the LED current will not change until there has been a steady-

state change in the ambient light for at least 2 averaging

periods.

3. The two most current averaging samples are used to

make zone change decisions.

4. To make a zone change, data from three averaging

cycles are needed. (Starting Value, First Transition,

Second Transition or Rest).

5. To Increase the brightness zone, the Averager output

must have increased for at least 2 averaging periods or

increased and remained at the new level for at least two

averaging periods ('+' to '+' or '+' to 'Rest' in Figure 6).

6. To decrease the brightness zone, the Averager output

must have decreased for at least 2 averaging periods or

decreased and remained at the new level for at least two

averaging periods ('-' to '-' or '-' to 'Rest' in Figure 6).

In the case of two consecutive increases or decreases in the

Averager output, the LM3530 will transition to zone equal to

the last averager output (Figure 6).

Using the diagram for the ALS block (Figure 3), the flow of

information is shown in (Figure 7). This starts with the ALS

input into the A/D, into the Averager, and then into the Dis-

criminator. Each state filters the previous output to help pre-

vent unwanted zone to zone transitions.

Averager Operation

The magnitude and direction (either increasing or decreasing)

of the Averager output is used to determine whether the

LM3530 should change brightness zones. The Averager

block functions as follows:

When using the ALS averaging function, it is important to re-

member that the averaging cycle is free running and is not

synchronized with changing ambient lighting conditions. Due

to the nature of the averager round down, an increase in

brightness can take between 2 and 3 averaging cycles to

change zones, while a decrease in brightness can take be-

tween 1 and 2 averaging cycles. See Table 6 for a list of

possible Averager periods. Figure 8 shows an example of

how the perceived brightness change time can vary.

1. First, the Averager always begins with a Zone 0 reading

stored at startup. If the main display LEDs are active

before the ALS block is enabled, it is recommended that

the ALS Enable 1 bit is set to '1' at least 3 averaging

periods before the ALS Enable 2 bit is set.

2. The Averager will always round down to the lower zone

in the event of a non-integer zone average. For example,

www.national.com

14

30086685

FIGURE 5. Averager Calculation

30086686

FIGURE 6. Brightness Zone Change Examples

15

www.national.com

30086687

FIGURE 7. Ambient Light Input to Backlight Transition

30086688

FIGURE 8. Perceived Brightness Change Time

ZONE BOUNDARY SETTINGS

ZONE BOUNDARY TRIP POINTS AND HYSTERESIS

Registers 0x60, 0x61, 0x62, and 0x63 set the 4 zone bound-

aries (thresholds) for the ALS inputs. These 4 zone bound-

aries create 5 brightness zones which map over to 5 separate

brightness zone targets (see Figure 4). Each 8–bit zone

boundary register can set a threshold from typically 0 to 1V

with linear step sizes of approximately 1/255 = 3.92mV. Ad-

ditionally, each zone boundary has built in hysteresis which

can be either lower or higher then the programmed Zone

Boundary depending on the last direction (either up or down)

of the ALS input voltage.

For each zone boundary setting, the trip point will vary above

or below the nominal set point depending on the direction (ei-

ther up or down) of the ALS input voltage. This is designed to

keep the ALS input from oscillating back and forth between

zones in the event that the ALS voltage is residing near to the

programmed zone boundary threshold. The Zone Boundary

Hysteresis will follow these 2 rules:

1. If the last zone transition was from low to high, then the

trip point (V_TRIP) will be V_{ZONE_BOUNDARY}- V_HYST/2, where

V_{ZONE_BOUNDARY}is the zone boundary set point as

www.national.com

16

programmed into the Zone Boundary registers, and

V_HYSTis typically 7mV.

Referring to Figure 9, each numbered trip point shown is de-

termined from the direction of the previous ALS zone transi-

tion.

2. If the last zone transition was from high to low then the

trip point (V_TRIP) will be V_{ZONE_BOUNDARY}+ V_HYST/2.

Figure 9 details how the LM3530's ALS Input Zone Boundary

Thresholds vary depending on the direction of the ALS input

voltage.

30086636

FIGURE 9. Zone Boundaries With Hysteresis

MINIMUM ZONE BOUNDARY SETTINGS

of offset voltage is necessary to prevent random offsets and

noise on the ALS inputs from creating threshold levels that

are below GND. This essentially guarantees that any Zone

Boundary threshold selected is achievable with positive ALS

voltages.

The actual minimum zone boundary setting is code 0x03.

Codes of 0x00, 0x01, and 0x02 are all mapped to code 0x03.

Table 1 shows the: Zone Boundary codes 0x00 through 0x04,

the typical thresholds, and the high and low hysteresis values.

The remapping of codes 0x00 - 0x02 plus the additional 4mV

17

www.national.com

TABLE 1. Ideal Zone Boundary Settings with Hysteresis (Lower 5 Codes)

Zone Boundary Code

Typical Zone Boundary

Threshold

Typical Threshold +

Hysteresis

Typical Threshold -

Hysteresis

0x00

0x01

0x02

0x03

0x04

15.8mV

19.7mV

19.3mV

23.2mV

12.3mV

16.2mV

ness Code can either come from the BRT Register (0xA0) in

I2C Compatible Current Control, or from the ALS Zone Target

Registers (Address 0x70-0x74) in Ambient Light Current Con-

trol. Figure 10 shows the current control block diagram.

LED CURRENT CONTROL

The LED current is is a function of the Full Scale Current, the

Brightness Code, and the PWM input duty cycle. The Bright-

30086625

FIGURE 10. Current Control Block Diagram

The following sections describe each of these LED current

control methods.

Control Register. The LED current using PWM + I²C-Com-

patible Control is given by the following equation:

PWM + I²C-COMPATIBLE CURRENT CONTROL

PWM + I²C-compatible current control is enabled by writing a

‘1’ to the Enable PWM bit (General Configuration Register bit

[5]) and writing a ‘1’ to the I²C Device Enable bit (General

Configuration Register bit 0). This makes the LED current a

function of the PWM input duty cycle (D), the Full-Scale LED

current (I_{LED_FS}), and the % of full-scale LED current . The %

of Full-Scale LED current is set by the code in the Brightness

BRT is the percentage of Full Scale Current as set in the

Brightness Control Register. The Brightness Control Register

can have either exponential or linear brightness mapping de-

pending on the setting of the BMM bit (bit [1] in General

Configuration Register).

www.national.com

18

EXPONENTIAL OR LINEAR BRIGHTNESS MAPPING

MODES

ter), a '0' to the Simple Enable bit (bit 7), and a '0' to the PWM

Enable bit (bit 5). With bit 5 = 0, the duty cycle information at

the PWM input is not used in setting the LED current.

With bit [1] of the General Configuration Register set to 0 (de-

fault) exponential mapping is selected and the code in the

Brightness Control Register corresponds to the Full-Scale

LED current percentages in Table 1 and Figure 11. With bit

[1] set to 1 linear mapping is selected and the code in the

Brightness Control Register corresponds to the Full-Scale

LED current percentages in Table 2 and Figure 12.

In this mode the LED current is a function of the Full-Scale

LED current bits (bits [4:2] of the General Configuration Reg-

ister) and the code in the Brightness Control Register. The

LED current mapping for the Brightness Control Register can

be linear or exponential depending on bit [1] in the General

Configuration Register (see Exponential or Linear Brightness

Mapping Modes section). Using I²C-Compatible Control Only,

the Full-Scale LED Current bits and the Brightness Control

Register code provides nearly 1016 possible current levels

selectable over the I²C-compatible interface.

PWM INPUT POLARITY

Bit [6] of the General Configuration Register controls the

PWM input polarity. Setting this bit to 0 (default) selects pos-

itive polarity and makes the LED current (with PWM mode

enabled) a function of the positive duty cycle at PWM. With

this bit set to ‘0’ the LED current (with PWM mode enabled)

becomes a function of the negative duty cycle at PWM.

Example: I²C-Compatible Current Control Only

As an example, assume the General Configuration Register

is loaded with 0x15. From this sets up the LM3530 with:

Simple Enable OFF (bit 7 = 0)

The PWM input is a logic level input with a frequency range

of 400Hz to 50kHz. Internal filtering of the PWM input signal

converts the duty cycle information to an average (analog)

control signal which directly controls the LED current.

Positive PWM Polarity (bit 6 = 0)

PWM Disabled (bit 5 = 0)

Full-Scale Current set at 22.5mA (bits [4:2] = 101)

Brightness Mapping set for Exponential (bit 1 = 0)

Device Enabled via I2C (bit 0 = 1)

Example: PWM + I²C-Compatible Current Control

As an example, assume the the General Configuration Reg-

ister is loaded with (0x2D). From Table 4, this sets up the

LM3530 with:

The Brightness Control Register is then loaded with 0x72

(48.438% of full-scale current from ). The LED current with

this configuration becomes:

Simple Enable OFF (bit 7 = 0)

Positive PWM Polarity (bit 6 = 0)

PWM Enabled (bit 5 = 1)

Full-Scale Current set at 15.5mA (bits [4:2] = 100)

Brightness Mapping set for Exponential (bit 1 = 0)

Device Enabled via I²C (bit 0 = 1)

Where BRT is the % of I_{LED_FS}as set in the Brightness Control

Register.

Next, the brightness mapping is set to linear mapping mode

(bit [1] in General Configuration Register set to 1). Using the

same Full-Scale current settings and Brightness Control Reg-

ister settings as before, the LED current becomes:

Next, the Brightness Control Register is loaded with 0x73.

This sets the LED current to 51.406% of full scale (see ). Fi-

nally, the PWM input is driven with a 0 to 2V pulse waveform

at 70% duty cycle. The LED current under these conditions

will be:

Where BRT is the percentage of I_{LED_FS}as set in the Bright-

ness Control Register,

Which is higher now since the code in the Brightness Control

Register (0x72) corresponds to 89.76% of Full-Scale LED

Current due to the different mapping mode given in .

I²C-COMPATIBLE CURRENT CONTROL ONLY

I²C-Compatible Control is enabled by writing a '1' to the I²C

Device Enable bit (bit [0] of the General Configuration Regis-

19

www.national.com

30086618

FIGURE 11. Exponential Brightness Mapping

TABLE 2. I_LEDvs. Brightness Register Data (Exponential Mapping)

BRT Data

(Hex)

% Full-Scale

Current

BRT Data

(Hex)

% of Full-

Scale

BRT Data % of Full-Scale BRT Data

% of Full-Scale

Current

(Hex)

Current

(Hex)

Current

0x00

0x01

0x02

0x03

0x04

0x05

0x06

0x07

0x08

0x09

0x0A

0x0B

0x0C

0x0D

0x0E

0x0F

0x10

0x11

0x12

0x13

0x14

0x15

0x16

0x17

0x18

0x19

0x1A

0x1B

0x1C

0.00%

0.080%

0.086%

0.094%

0.102%

0.109%

0.117%

0.125%

0.133%

0.141%

0.148%

0.156%

0.164%

0.172%

0.180%

0.188%

0.203%

0.211%

0.227%

0.242%

0.250%

0.266%

0.281%

0.297%

0.320%

0.336%

0.352%

0.375%

0.398%

0x20

0x21

0x22

0x23

0x24

0x25

0x26

0x27

0x28

0x29

0x2A

0x2B

0x2C

0x2D

0x2E

0x2F

0x30

0x31

0x32

0x33

0x34

0x35

0x36

0x37

0x38

0x39

0x3A

0x3B

0x3C

0.500%

0.523%

0.555%

0.586%

0.617%

0.656%

0.695%

0.734%

0.773%

0.820%

0.867%

0.914%

0.969%

1.031%

1.078%

1.148%

1.219%

1.281%

1.359%

1.430%

1.523%

1.594%

1.688%

1.781%

1.898%

2.016%

2.109%

2.250%

2.367%

0x40

0x41

0x42

0x43

0x44

0x45

0x46

0x47

0x48

0x49

0x4A

0x4B

0x4C

0x4D

0x4E

0x4F

0x50

0x51

0x52

0x53

0x54

0x55

0x56

0x57

0x58

0x59

0x5A

0x5B

0x5C

2.953%

3.125%

3.336%

3.500%

3.719%

3.906%

4.141%

4.375%

4.648%

4.922%

5.195%

5.469%

5.781%

6.125%

6.484%

6.875%

7.266%

7.656%

8.047%

8.594%

9.063%

9.609%

10.078%

10.781%

11.250%

11.953%

12.656%

13.359%

14.219%

0x60

0x61

0x62

0x63

0x64

0x65

0x66

0x67

0x68

0x69

0x6A

0x6B

0x6C

0x6D

0x6E

0x6F

0x70

0x71

0x72

0x73

0x74

0x75

0x76

0x77

0x78

0x79

0x7A

0x7B

0x7C

17.813%

18.750%

19.922%

20.859%

22.266%

23.438%

24.844%

26.250%

27.656%

29.297%

31.172%

32.813%

34.453%

35.547%

38.828%

41.016%

43.203%

45.938%

48.438%

51.406%

54.141%

57.031%

60.703%

63.984%

67.813%

71.875%

75.781%

79.688%

84.375%

www.national.com

20

BRT Data

(Hex)

% Full-Scale

Current

BRT Data

(Hex)

% of Full-

Scale

BRT Data % of Full-Scale BRT Data

% of Full-Scale

Current

(Hex)

Current

(Hex)

Current

0x1D

0x1E

0x1F

0.422%

0.445%

0.469%

0x3D

0x3E

0x3F

2.508%

2.648%

2.789%

0x5D

0x5E

0x5F

15.000%

15.859%

16.875%

0x7D

0x7E

0x7F

89.844%

94.531%

100.00%

30086619

FIGURE 12. Linear Brightness Mapping

TABLE 3. I_LEDvs. Brightness Register Data (Linear Mapping)

BRT Data

(Hex)

% Full-Scale

Current

(Linear)

BRT Data

(Hex)

% of Full-

Scale

Current

(Linear)

BRT Data % of Full-Scale

BRT Data

(Hex)

% of Full-

Scale Current

(Linear)

(Hex)

Current

(Linear)

0x00

0x01

0x02

0x03

0x04

0x05

0x06

0x07

0x08

0x09

0x0A

0x0B

0x0C

0x0D

0x0E

0x0F

0x10

0x11

0x12

0x13

0x14

0x15

0.00%

0.79%

1.57%

2.36%

3.15%

3.94%

4.72%

5.51%

6.30%

7.09%

7.87%

8.66%

9.45%

10.24%

11.02%

11.81%

12.60%

13.39%

14.17%

14.96%

15.75%

16.54%

0x20

0x21

0x22

0x23

0x24

0x25

0x26

0x27

0x28

0x29

0x2A

0x2B

0x2C

0x2D

0x2E

0x2F

0x30

0x31

0x32

0x33

0x34

0x35

25.20%

25.98%

26.77%

27.56%

28.35%

29.13%

29.92%

30.71%

31.50%

32.28%

33.07%

33.86%

34.65%

35.43%

36.22%

37.01%

37.80%

38.58%

39.37%

40.16%

40.94%

41.73%

0x40

0x41

0x42

0x43

0x44

0x45

0x46

0x47

0x48

0x49

0x4A

0x4B

0x4C

0x4D

0x4E

0x4F

0x50

0x51

0x52

0x53

0x54

0x55

50.39%

0x60

0x61

0x62

0x63

0x64

0x65

0x66

0x67

0x68

0x69

0x6A

0x6B

0x6C

0x6D

0x6E

0x6F

0x70

0x71

0x72

0x73

0x74

0x75

75.59%

76.38%

77.17%

77.95%

78.74%

79.53%

80.31%

81.10%

81.89%

82.68%

83.46%

84.25%

85.04%

85.83%

86.61%

87.40%

88.19%

88.98%

89.76%

90.55%

91.34%

92.13%

51.18%

51.97%

52.76%

53.54%

54.33%

55.12%

55.91%

56.69%

57.48%

58.27%

59.06%

59.84%

60.63%

61.42%

62.20%

62.99%

63.78%

64.57%

65.35%

66.14%

66.93%

21

www.national.com

BRT Data

(Hex)

% Full-Scale

Current

(Linear)

BRT Data

(Hex)

% of Full-

Scale

Current

(Linear)

BRT Data % of Full-Scale

BRT Data

(Hex)

% of Full-

Scale Current

(Linear)

(Hex)

Current

(Linear)

0x16

0x17

0x18

0x19

0x1A

0x1B

0x1C

0x1D

0x1E

0x1F

17.32%

18.11%

18.90%

19.69%

20.47%

21.26%

22.05%

22.83%

23.62%

24.41%

0x36

0x37

0x38

0x39

0x3A

0x3B

0x3C

0x3D

0x3E

0x3F

42.52%

43.31%

44.09%

44.88%

45.67%

46.46%

47.24%

48.03%

48.82%

49.61%

0x56

0x57

0x58

0x59

0x5A

0x5B

0x5C

0x5D

0x5E

0x5F

67.72%

0x76

0x77

0x78

0x79

0x7A

0x7B

0x7C

0x7D

0x7E

0x7F

92.91%

93.70%

94.49%

95.28%

96.06%

96.85%

97.64%

98.43%

99.21%

100.00%

68.50%

69.29%

70.08%

70.87%

71.65%

72.44%

73.23%

74.02%

74.80%

SIMPLE ENABLE DISABLE WITH PWM CURRENT

CONTROL

Driving the PWM input with a pulsed waveform at a variable

duty cycle is also possible in simple enable/Disable mode, so

long as the low pulse width is < 2ms. When a PWM signal is

used in this mode the input duty cycle information is internally

filtered, and an analog voltage is used to control the LED cur-

rent. This type of PWM control (PWM to Analog current

control) prevents large voltage excursions across the output

capacitor that can result in audible noise. Simple Enable/Dis-

able mode can be useful since the default bit setting for the

General Configuration Register is 0xCC (Simple Enable bit =

1, PWM Enable = 1, and Full-Scale Current = 19mA). Addi-

tionally, the default Brightness Register setting is 0x7F (100%

of Full-Scale current). This gives the LM3530 the ability to turn

on after power up (or after reset) without having to do any

writes to the I²C-compatible bus.

With bits [7 and 5] of the General Configuration Register set

to ‘1’ the PWM input is enabled as a simple enable/disable.

The simple enable/disable feature operates as described in

Figure 13. In this mode, when the PWM input is held high

(PWM Polarity bit = 0) for > 2ms the LM3530 will turn on the

LED current at the programmed Full-Scale Current × % of

Full-Scale Current as set by the code in the Brightness Con-

trol Register. When the PWM input is held low for > 2ms the

device will shut down. With the PWM Polarity bit = 1 the PWM

input is configured for active low operation. In this configura-

tion holding PWM low for > 2ms will turn on the device at the

programmed Full-Scale Current × % of Full-Scale Current as

set by the code in the Brightness Control Register. Likewise,

holding PWM high for > 2ms will put the device in shutdown.

30086604

FIGURE 13. Simple Enable/Disable Timing

Example: Simple Enable Disable with PWM Current Con-

trol)

As an example, assume that the HWEN input is toggled low

then high. This resets the LM3530 and sets all the registers

to their default value. When the PWM input is then pulled high

for > 2ms the LED current becomes:

Then, if the Brightness Control Register is loaded with 0x55

(9.6% of Full-Scale Current) the LED current becomes:

AMBIENT LIGHT CURRENT CONTROL

With bits [4:3] of the ALS Configuration Register both set to

1, the LM3530 is configured for Ambient Light Current Con-

trol. In this mode the ambient light sensing inputs (ALS1, and/

or ALS2) monitor the outputs of analog output ambient light

sensing photo diodes and adjust the LED current depending

on the ambient light. The ambient light sensing circuit has 4

where BRT is the % of I_{LED_FS}as set in the Brightness Control

Register.

If then the PWM input is fed with a 5kHz pulsed waveform at

40% duty cycle the LED current becomes:

www.national.com

22

configurable Ambient Light Boundaries (ZB0 – ZB3) pro-

grammed through the four (8-bit) Zone Boundary Registers.

These zone boundaries define 5 ambient brightness zones

(Figure 4). Each zone corresponds to a programmable bright-

ness setting which is programmable through the 5 Zone Tar-

get Registers (Z0T – Z4T). When the ALS1, and/or ALS2 input

(depending on the bit settings of the ALS Input Select bits)

detects that the ambient light has crossed to a new zone (as

defined by one of the Zone Boundary Registers) the LED cur-

rent becomes a function of the Brightness Code loaded in the

Zone Target Register which corresponds to the new ambient

light brightness zone.

Ambient Light Current Control Enabled (bit 4 = 1)

ALS circuitry Enabled (bit 3 = 1)

Sets the ALS Averaging Time to 512ms (bits [2:0] = 100)

Next, the General Configuration Register is programmed with

0x19 which sets the Full-Scale Current to 26mA, selects Ex-

ponential Brightness Mapping, and enables the device via the

I²C-compatible interface.

Now assume that the APDS-9005 ambient light sensor de-

tects a 100 LUX ambient light at its input. This forces the

ambient light sensors output (and the ALS1 input) to 87.5mV

corresponding to Zone 0. Since Zone 0 points to the bright-

ness code programmed in Zone Target Register 0 (loaded

with code 0x19), the LED current becomes:

On startup the 4 Zone Boundary Registers are pre-loaded

with 0x33 (51d), 0x66 (102d), 0x99 (153d), and 0xCC (204d).

Each ALS input has a 1V active input voltage range with a

4mV offset voltage which makes the default Zone Boundaries

set at:

Zone Boundary 0 = 1V × 51/255 + 4mV = 204mV

Zone Boundary 1 = 1V × 102/255 + 4mV = 404mV

Zone Boundary 2 = 1V × 153/255 + 4mV = 604mV

Zone Boundary 3 = 1V × 204/255 + 4mV = 804mV

Where the code in Zone Target Register 0 points to the % of

ILED_FS as given by Table 2 or Table 3, depending on

whether Exponential or Linear Mapping are selected.

Next, assume that the ambient light changes to 500 LUX (cor-

responding to an ALS1 voltage of 454mV). This moves the

ambient light into Zone 2 which corresponds to Zone Target

Register 2 (loaded with code 0x4C) the LED current then be-

comes:

These Zone Boundary Registers are all 8-bit (readable and

writable) registers. The first zone (Z0) is defined between 0

and 204mV, Z1’s default is defined between 204mV and

404mV, Z2’s default is defined between 404mV and 604mV,

Z3’s default is defined between 604mV and 804mV, and Z4’s

default is defined between 804mV and 1.004V. The default

settings for the 5 Zone Target Registers are 0x19, 0x33,

0x4C, 0x66, and 0x7F. This corresponds to LED brightness

settings of 0.336%, 1.43%, 5.781%, 24.844%, and 100% of

full-scale current respectively (assuming exponential back-

light mapping).

AMBIENT LIGHT CURRENT CONTROL + PWM

The Ambient Light Current Control can also be a function of

the PWM input duty cycle. Assume the LM3530 is configured

as described in the above Ambient Light Current Control ex-

ample, but this time the Enable PWM bit set to ‘1’ (General

Configuration Register bit [5]).

Example: Ambient Light Control Current

As an example, assume that the APDS-9005 is used as the

ambient light sensing photo diode with its output connected

to the ALS1 input. The ALS Resistor Select Register is loaded

with 0x04 which configures the ALS1 input for a 2.27kΩ in-

ternal pull-down resistor (see Table 9). The APDS-9005 has

a typical 400nA/LUX response. With a 2.27kΩ resistor the

sensor output would see a 0 to 908mV swing with a 0 to 1000

LUX change in ambient light. Next, the ALS Configuration

Register is programmed with 0x3C. From Table 6, this con-

figures the LM3530’s ambient light sensing interface for:

Example: Ambient Light Current Control + PWM

In this example, the APDS-9005 detects that the ambient light

has changed to 1 kLUX. The voltage at ALS1 is now around

908mV and the ambient light falls within Zone 5. This causes

the LED brightness to be a function of Zone Target Register

5 (loaded with 0x7F). Now assume the PWM input is also

driven with a 50% duty cycle pulsed waveform. The LED cur-

rent now becomes:

ALS1 as the active ALS input (bits [6:5] = 01)

30086626

Example: ALS Averaging

As an example, suppose the LM3530’s ALS Configuration

Register is loaded with 0x3B. This configures the device for:

Configuration Register is loaded with 0x15. This sets up the

device with:

Simple Enable OFF (bit 7 = 0)

ALS1 as the active ALS input (bits [6:5] = 01)

Enables Ambient Light Current Control (bit 4 = 1)

Enables the ALS circuitry (bit 3 = 1)

PWM Polarity High (bit 6 = 0)

PWM Input Disabled (bit 5 = 0)

Full-Scale Current = 22.5mA (bits [4:2] = 101)

Brightness Mapping Mode as Exponential (bit 1 = 0)

Device Enabled via I²C (bit 0 = 1)

Sets the ALS Averaging Time to 256ms (bits [2:0] = 011)

Next, the ALS Resistor Select Register is loaded with 0x04.

This configures the ALS2 input as high impedance and con-

figures the ALS1 input with a 2.27kΩ internal pull-down re-

sistor. The Zone Boundary Registers and Zone Target

Registers are left with their default values. The Brightness

Ramp Rate Register is loaded with 0x2D. This sets up the

LED current ramp rate at 16.384ms/step. Finally, the General

As the device starts up the APDS-9005 ambient light sensor

(connected to the ALS1 input) detects 500 LUX. This puts

approximately 437.5mV at ALS1 (see Figure 14). This places

the measured ambient light between Zone Boundary Regis-

ters 1 and 2, thus corresponding to Zone Target Register 2.

The default value for this register is 0x4C. The LED current is

programmed to:

23

www.national.com

then during period #11, goes to 4. Since there have been 2

increases in the average during #10 and #11, the beginning

of average period #12 shows a change in the brightness zone

to Zone 4. This results in the LED current ramping to the new

value of 22.5mA (Zone 4's target). During period #12 the am-

bient light steps back to 500 LUX and forces ALS1 to 437.5mV

(corresponding to Zone 2). After average periods #12 and #13

have shown that the averager transitioned lower two times,

the brightness zone changes to the new target at the begin-

ning of period #14. This signals the LED current to ramp down

to the zone 2 target of 1.3mA. Looking back at average peri-

ods #12 and #13, the LED current was only able to ramp up

to 7.38mA due to the ramp rate of 16.384ms/step (2 average

periods of 256ms each) before it was instructed to ramp back

to Zone 2's target at the start of period #14. This example

demonstrates not only the averaging feature, but how addi-

tional filtering of transient events on the ALS inputs can be

accomplished by using the LED current ramp rates.

Referring to Figure 14, initially the Averager is loaded with

Zone 0 so it takes 2 averaging periods for the LM3530 to

change to the new zone. After the ALS1 voltage remains at

437.5mV for two averaging periods (end of period #2) the

LM3530 sees a repeat of Zone 2 and signals the LED current

to begin ramping to Zone 2's target beginning at average pe-

riod #3. Since the ramp rate is set at 16.384ms/step the LED

current goes from 0 to 1.3mA in 76 × 16.384ms = 1.245s (ap-

proximately 5 average periods).

After the LED current has been at its steady state of 1.3mA

for a while, the ambient light suddenly steps to 900 LUX for

500ms and then steps back to 500 LUX. In this case the 900

LUX will place the ALS1 voltage at approximately 979mV cor-

responding to Zone 4 somewhere during average period #10

and fall back to 437.5mV somewhere during average period

#12. The averager output during period #10 goes to 3, and

30086684

FIGURE 14. ALS Averaging Example

www.national.com

24

INTERRUPT OUTPUT

LED + 400mV headroom voltage for the current sink = 21.4V).

The 25V OVP option allows for the use of lower voltage and

smaller sized (25V) output capacitors. The 40V device would

typically require a 50V output capacitor.

INT is an open-drain output which pulls low when the Ambient

Light Sensing circuit has transitioned to a new ambient bright-

ness zone. When a read-back of the ALS Information Register

is done INT is reset to the open drain state.

HARDWARE ENABLE

OVER-VOLTAGE PROTECTION

The HWEN input is an active high hardware enable which

must be pulled high to enable the device. Pulling this pin low

disables the I²C-compatible interface, the simple enable/dis-

able input, the PWM input, and resets all registers to their

default state (see Table 4).

Over-voltage protection is set at 40V (minimum) for the

LM3530-40 and 23.6V minimum for the LM3530-25. The 40V

version allows typically up to 11 series white LEDs (assuming

3.5V per LED + 400mV headroom voltage for the current sink

= 38.9V). When the OVP threshold is reached the LM3530’s

switching converter stops switching, allowing the output volt-

age to discharge. Switching will resume when the output

voltage falls to typically 1V below the OVP threshold. In the

event of an LED open circuit the output will be limited to

around 40V with a small amount of voltage ripple. The 25V

version allows up to 6 series white LEDs (assuming 3.5V per

THERMAL SHUTDOWN

In the event the die temperature reaches +140°C, the LM3530

will stop switching until the die temperature cools by 15°C. In

a thermal shutdown event the device is not placed in reset;

therefore, the contents of the registers are left in their current

state.

25

www.national.com

START and STOP conditions. The I²C bus is considered busy

after a START condition and free after a STOP condition.

During data transmission, the I²C master can generate re-

peated START conditions. A START and a repeated START

conditions are equivalent function-wise. The data on SDA

must be stable during the HIGH period of the clock signal

(SCL). In other words, the state of SDA can only be changed

when SCL is LOW.

I²C-Compatible Interface

START AND STOP CONDITION

The LM3530 is controlled via an I²C-compatible interface.

START and STOP conditions classify the beginning and the

end of the I²C session. A START condition is defined as SDA

transitioning from HIGH to LOW while SCL is HIGH. A STOP

condition is defined as SDA transitioning from LOW to HIGH

while SCL is HIGH. The I²C master always generates the

30086637

FIGURE 15. Start and Stop Sequences

I²C-COMPATIBLE ADDRESS

indicates a WRITE and R/W = 1 indicates a READ. The sec-

ond byte following the chip address selects the register ad-

dress to which the data will be written. The third byte contains

the data for the selected register.

The 7bit chip address for the LM3530 is (0x38, or 0x39) for

the 40V version and (0x36) for the 25V version. After the

START condition, the I²C master sends the 7-bit chip address

followed by an eighth bit (LSB) read or write (R/W). R/W= 0

30086638

FIGURE 16. I²C-Compatible Chip Address (0x38)

30086639

FIGURE 17. I²C-Compatible Chip Address (0x36)

TRANSFERRING DATA

clock pulse. The LM3530 pulls down SDA during the 9th clock

pulse, signifying an acknowledge. An acknowledge is gener-

ated after each byte has been received.

Every byte on the SDA line must be eight bits long, with the

most significant bit (MSB) transferred first. Each byte of data

must be followed by an acknowledge bit (ACK). The acknowl-

edge related clock pulse (9th clock pulse) is generated by the

master. The master then releases SDA (HIGH) during the 9th

There are fourteen 8-bit registers within the LM3530 as de-

tailed in Table 4.

www.national.com

26

Register Descriptions

TABLE 4. LM3530 Register Definition

Register Name

Function

Address

POR Value

1. Simple Interface Enable

2. PWM Polarity

3. PWM enable

General

Configuration

0x10

0xB0

4. Full-Scale Current Selection

5. Brightness Mapping Mode Select

6. I²C Device Enable

1. ALS Current Control Enable

2. ALS Input Enable

3. ALS Input Select

ALS Configuration

0x20

0x2C

4. ALS Averaging Times

Brightness Ramp Programs the rate of rise and fall of the LED current

Rate

0x30

0x40

0x41

0xA0

0x60

0x61

0x62

0x63

0x70

0x00

0x7F

0x33

0x66

0x99

0xCC

0x19

ALS Zone

Information

1. Zone Boundary Change Flag

2. Zone Brightness Information

ALS Resistor

Select

Internal ALS1 and ALS2 Resistances

Brightness Control Holds the 7 bit Brightness Data

(BRT)

Zone Boundary 0 ALS Zone Boundary #0

(ZB0)

Zone Boundary 1 ALS Zone Boundary #1

(ZB1)

Zone Boundary 2 ALS Zone Boundary #2

(ZB2)

Zone Boundary 3 ALS Zone Boundary #3

(ZB3)

Zone Target 0

(Z0T)

Zone 0 LED Current Data. The LED Current Source transitions to the

brightness code in Z0T when the ALS_ input is less than the zone

boundary programmed in ZB0.

Zone Target 1

(Z1T)

Zone 1 LED Current Data. The LED Current Source transitions to the

brightness code in Z1T when the ALS_ input is between the zone

boundaries programmed in ZB1 and ZB0.

0x71

0x72

0x73

0x74

0x33

0x4C

0x66

0x7F

Zone Target 2

(Z2T)

Zone 2 LED Current Data. The LED Current Source transitions to the

brightness code in Z2T when the ALS_ input is between the zone

boundaries programmed in ZB2 and ZB1.

Zone Target 3

(Z3T)

Zone 3 LED Current Data. The LED Current Source transitions to the

brightness code in Z3T when the ALS_ input is between the zone

boundaries programmed in ZB3 and ZB2.

Zone Target 4

(Z4T)

Zone 4 LED Current Data. The LED Current Source transitions to the

brightness code in Z4T when the ALS_ input is between the zone

boundaries programmed in ZB4 and ZB3.

*Note: Unused bits in the LM3530's Registers default to a logic '1'.

27

www.national.com

GENERAL CONFIGURATION REGISTER (GP)

The General Configuration Register (address 0x10) is de-

scribed in Figure 18 and Table 5.

30086609

FIGURE 18. General Configuration Register

TABLE 5. General Configuration Register Description (0x10)

Bit 7

Bit 6

Bit 5

(EN_PWM)

see Figure 8

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

(I²C Device

Enable)

(PWM Simple (PWM

Enable

(Full-Scale (Full-Scale (Full-Scale (Mapping

Current

Select)

Polarity)

Current

Select)

Current

Select)

Mode Select)

0 = Simple

Interface at

PWM Input is 1 = PWM

0 = PWM

active high

0 = LED current 000 = 5 mA full-scale current

is not a function 001 = 8.5 mA full-scale current

0 =

0 = Device

Disabled

1 = Device

Enabled

exponential

mapping

1 = linear

mapping

of PWM duty

cycle

010 = 12 mA full-scale current

011 = 15.5 mA full-scale current

Disabled

active low

1 = Simple

Interface at

PWM Input is

Enabled

1 = LED current 100 = 19 mA full-scale current

is a function of 101 = 22.5 mA full-scale current

duty cycle

110 = 26 mA full-scale current

111 = 29.5 mA full-scale current

ALS CONFIGURATION REGISTER

The ALS Configuration Register controls the Ambient Light

Sensing input functions and is described in Figure 19 and

Table 6.

30086610

FIGURE 19. ALS Configuration Register

www.national.com

28

TABLE 6. ALS Configuration Register Description (0x20)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

ALS Input

Select

ALS Input

Select

ALS Enable

ALS

Averaging

Time

ALS

Averaging

Time

ALS

Averaging

Time

N/A

00 = The Average of ALS1 and 00 or 10 = ALS is disabled. The 000 = 32 ms

ALS2 is used to control the LED Brightness Register is used to 001 = 64 ms

brightness

01 = ALS1 is used to control the 01 = ALS is enabled. The

LED brightness

10 = ALS2 is used to control the determine the LED Current.

determine the LED current.

010 = 128 ms

011 = 256 ms

Brightness Register is used to 100 = 512 ms

101 = 1024 ms

11 = ALS inputs are enabled. 110 = 2048 ms

LED brightness

11 = The ALS input with the

highest voltage is used to

control the LED brightness

Ambient light determines the

LED current.

111 = 4096 ms

BRIGHTNESS RAMP RATE REGISTER

are independently adjustable Figure 20 and Table 7 describe

the bit settings.

The Brightness Ramp Rate Register controls the rate of rise

or fall of the LED current. Both the rising rate and falling rate

30086611

FIGURE 20. Brightness Ramp Rate Register

TABLE 7. Brightness Ramp Rate Register Description (0x30)

Bit 7

Bit 6

N/A

Bit 5

(BRRI2)

Bit 4

(BRRI1)

Bit 3

(BRRI0)

Bit 2

(BRRD2)

Bit 1

(BRRD1)

Bit 0

(BRRD0)

N/A

000 = 8 µs/step (1.106ms from 0 to Full Scale)

000 = 8 µs/step (1.106ms from Full Scale to 0)

001 = 1.024 ms/step (130ms from 0 to Full Scale) 001 = 1.024 ms/step (130ms from Full Scale to 0)

010 = 2.048 ms/step (260ms from 0 to Full Scale) 010 = 2.048 ms/step (260ms from Full Scale to 0)

011 = 4.096 ms/step (520ms from 0 to Full Scale) 011 = 4.096 ms/step (520ms from Full Scale to 0)

100 = 8.192 ms/step (1.04s from 0 to Full Scale) 100 = 8.192 ms/step (1.04s from Full Scale to 0)

101 = 16.384 ms/step (2.08s from 0 to Full Scale) 101 = 16.384 ms/step (2.08s from Full Scale to 0)

110 = 32.768 ms/step (4.16s from 0 to Full Scale) 110 = 32.768 ms/step (4.16s from Full Scale to 0)

111 = 65.538 ms/step (8.32s from 0 to Full Scale) 111 = 65.538 ms/step (8.32s from Full Scale to 0)

ALS ZONE INFORMATION REGISTER

Register is signaled by the INT output going from high to low.

A read-back of the ALS Zone Information Register will cause

the INT output to go open-drain again. The Zone Change Flag

(bit 3) is also updated on a Zone change and cleared on a

read back of the ALS Zone Information Register. Figure 21

and Table 8 detail the ALS Zone Information Register.

The ALS Zone Information Register is a read-only register

that is updated every time the active ALS input(s) detect that

the ambient light has changed to a new zone as programmed

in the Zone Boundary Registers. See Zone Boundary Regis-

ters description. A new update to the ALS Zone Information

30086612

FIGURE 21. ALS Zone Information Register

29

www.national.com

TABLE 8. ALS Zone Information Register Description (0x40)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

(Z2)

Bit 1

(Z1)

Bit 0

(Z0)

(Zone Boundary Change

Flag)

N/A

1 = the active ALS input has 000 = Zone 0

changed to a new ambient 001 = Zone 1

light zone as a programmed in 010 = Zone 2

the Zone Boundary Registers 011 = Zone 3

(ZB0 -ZB3)

100 = Zone 4

0 = no zone change

ALS RESISTOR SELECT REGISTER

program the input resistance at the ALS2 input. With bits [3:0]

set to all zeroes the ALS1 input is high impedance. With bits

[7:4] set to all zeroes the ALS2 input is high impedance.

The ALS Resistor Select Register configures the internal re-

sistance from either the ALS1 or ALS2 input to GND. Bits [3:0]

program the input resistance at the ALS1 input and bits [7:4]

30086634

FIGURE 22. ALS Resistor Select Register

TABLE 9. ALS Resistor Select Register Description (0x41)

Bit 5 Bit 4 Bit 3 Bit 2

Bit 7

Bit 6

Bit 1

Bit 0

(ALSR2A)

(ALSR2B (ALSR2C)

)

(ALSR2D) (ALSR1A) (ALSR1B) (ALSR1C) (ALSR1D)

0000 = ALS2 is high impedance

0001 = 13.531kΩ (73.9µA at 1V)

0010 =9.011kΩ (111µA at 1V)

0011 = 5.4116kΩ (185µA at 1V)

0100 = 2.271kΩ (440µA at 1V)

0101 = 1.946kΩ (514µA at 1V)

0110 = 1.815kΩ (551µA at 1V)

0111 = 1.6kΩ (625µA at 1V)

1000 = 1.138kΩ (879µA at 1V)

1001 = 1.05kΩ (952µA at 1V)

1010 = 1.011kΩ (989µA at 1V)

1011 = 941Ω (1.063mA at 1V)

1100 = 759Ω (1.318mA at 1V)

1101 = 719Ω (1.391mA at 1V)

1110 =700Ω (1.429mA at 1V)

1111 = 667Ω (1.499mA at 1V)

0000 = ALS2 is high impedance

0001 = 13.531kΩ (73.9µA at 1V)

0010 =9.011kΩ (111µA at 1V)

0011 = 5.4116kΩ (185µA at 1V)

0100 = 2.271kΩ (440µA at 1V)

0101 = 1.946kΩ (514µA at 1V)

0110 = 1.815kΩ (551µA at 1V)

0111 = 1.6kΩ (625µA at 1V)

1000 = 1.138kΩ (879µA at 1V)

1001 = 1.05kΩ (952µA at 1V)

1010 = 1.011kΩ (989µA at 1V)

1011 = 941Ω (1.063mA at 1V)

1100 = 759Ω (1.318mA at 1V)

1101 = 719Ω (1.391mA at 1V)

1110 =700Ω (1.429mA at 1V)

1111 = 667Ω (1.499mA at 1V)

BRIGHTNESS CONTROL REGISTER

There are two selectable LED current profiles. Setting the

General Configuration Register bit 1 to 0 selects the expo-

nentially weighted LED current response (see Figure 11).

Setting this bit to '1' selects the linear weighted curve (see

Figure 12). Table 2 and Table 3 show the percentage Full-

Scale LED Current at a given Brightness Register Code for

both the Exponential and Linear current response.

The Brightness Register (BRT) is an 8-bit register that pro-

grams the 127 different LED current levels (Bits [6:0]). The

code written to BRT is translated into an LED current as a

percentage of I_{LED_FULLSCALE}as set via the Full-Scale Current

Select bits (General Configuration Register bits [4:2]). The

LED current response has a typical 1000:1 dimming ratio at

the maximum full-scale current (General Configuration Reg-

ister bits [4:2] = (111) and using the exponential weighted

dimming curve.

www.national.com

30

30086633

FIGURE 23. Brightness Control Register

TABLE 10. Brightness Control Register Description (0xA0)

Bit 7

N/A

Bit 6

Data (MSB)

Bit 5

Data

Bit 4

Data

Bit 3

Data

Bit 2

Data

Bit 1

Data

Bit 0

Data

LED Brightness Data (Bits [6:0]

Exponential Mapping (see FIX)

Linear Mapping (see FIX)

0000000 = LEDs Off

0000001 = 0.08% of Full Scale

0000001 = 0.79% of Full Scale

:

1111111 = 100% of Full Scale

31

www.national.com

ZONE BOUNDARY REGISTER

(800mV) of the full-scale ALS input voltage range (1V). The

necessary conditions for proper ALS operation are that the

data in ZB0 < data in ZB1 < data in ZB2 < data in ZB3.

The Zone Boundary Registers are programmed with the am-

bient light sensing zone boundaries. The default values are

set at 20% (200mV), 40% (400mV), 60% (600mV), and 80%

30086613

FIGURE 24. Zone Boundary Registers

www.national.com

32

ZONE TARGET REGISTERS

values for these registers and their corresponding percentage

of full-scale current for both linear and exponential brightness

is shown in Figure 25 and Table 11.

The Zone Target Registers contain the LED brightness data

that corresponds to the current active ALS zone. The default

30086614

FIGURE 25. Zone Target Registers

33

www.national.com

TABLE 11. Zone Boundary and Zone Target Default Mapping

Zone Boundary

(Default)

Zone Target

Register

(Default)

Full-Scale

Current (Default) (Default)

Linear Mapping Exponential

Mapping

(Default)

Boundary 0,

Active ALS input is less than 200

mV

0x19

0x33

0x4C

0x66

0x7F

19 mA

19.69% (3.74 µA) 0.336% (68.4 µA)

40.16% (7.63 µA) 1.43% (272 µA)

Boundary 1,

Active ALS input is between 200 mV

and 400 mV

Boundary 2,

Active ALS input is between 400 mV

and 600 mV

59.84% (11.37

mA)

5.78% (1.098 mA)

24.84% (4.72 mA)

100% (19 mA)

Boundary 3,

Active ALS input is between 600 mV

and 800 mV

80.31% (15.26

mA)

Boundary 4,

100% (19 mA)

Active ALS input is greater than

800mV

www.national.com

34

where ƒ_SW= 500 kHz,and η and I_PEAKcan be found in the

efficiency and I_PEAKcurves in the Typical Performance Char-

acteristics.

Applications Information

LED CURRENT SETTING/MAXIMUM LED CURRENT

The maximum LED current is restricted by the following fac-

tors: the maximum duty cycle that the boost converter can

achieve, the peak current limitations, and the maximum out-

put voltage.

OUTPUT VOLTAGE LIMITATIONS

The LM3530 has a maximum output voltage of 41V typical

(40V minimum) for the LM3530-40 version and 24V typical

(23.6V minimum) for the 25V version. When the output volt-

age rises above this threshold (V_OVP) the over-voltage pro-

tection feature is activated and the duty cycle is terminated.

Switching will cease until V_OUTdrops below the hysteresis

level (typically 1V below V_OVP). For larger numbers of series

connected LEDs the output voltage can reach the OVP

threshold at larger LED currents and colder ambient temper-

atures. Typically white LEDs have a -3mV/°C temperature

coefficient.

MAXIMUM DUTY CYCLE

The LM3530 can achieve up to typically 94% maximum duty

cycle. Two factors can cause the duty cycle to increase: an

increase in the difference between V_OUTand V_INand a de-

crease in efficiency. This is shown by the following equation:

OUTPUT CAPACITOR SELECTION

The LM3530’s output capacitor has two functions: filtering of

the boost converters switching ripple, and to ensure feedback

loop stability. As a filter, the output capacitor supplies the LED

current during the boost converters on time and absorbs the

inductor's energy during the switch off time. This causes a sag

in the output voltage during the on time and a rise in the output

voltage during the off time. Because of this, the output ca-

pacitor must be sized large enough to filter the inductor cur-

rent ripple that could cause the output voltage ripple to

become excessive. As a feedback loop component, the out-

put capacitor must be at least 1µF and have low ESR other-

wise the LM3530's boost converter can become unstable.

This requires the use of ceramic output capacitors. Table 12

lists part numbers and voltage ratings for different output ca-

pacitors that can be used with the LM3530.

For a 9-LED configuration V_OUT= (3.6V x 9LED + VHR) = 33V

operating with η = 70% from a 3V battery, the duty cycle re-

quirement would be around 93.6%. Lower efficiency or larger

V_OUTto V_INdifferentials can push the duty cycle requirement

beyond 94%.

PEAK CURRENT LIMIT

The LM3530’s boost converter has a peak current limit for the

internal power switch of 839mA typical (739mA minimum).

When the peak switch current reaches the current limit, the

duty cycle is terminated resulting in a limit on the maximum

output current and thus the maximum output power the

LM3530 can deliver. Calculate the maximum LED current as

a function of V_IN, V_OUT, L, efficiency (η) and I_PEAKas:

TABLE 12. Recommended Input/Output Capacitors

Part Number Value Size

1µF 0805

Manufacturer

Murata

Rating

50V

Description

COUT

CIN

GRM21BR71H105KA12

GRM188B31A225KE33

C1608X5R0J225

Murata

2.2µF

0805

0603

10V

TDK

6.3V

CIN

INDUCTOR SELECTION

When choosing L, the inductance value must also be large

enough so that the peak inductor current is kept below the

LM3530's switch current limit. This forces a lower limit on L

given by the following equation.

The LM3530 is designed to work with a 10µH to 22µH induc-

tor. When selecting the inductor, ensure that the saturation

rating for the inductor is high enough to accommodate the

peak inductor current . The following equation calculates the

peak inductor current based upon LED current, V_IN, V_OUT, and

Efficiency.

where:

I_{SW_MAX}is given in the Electrical Table, efficiency (η) is shown

in the Typical Performance Characteristics, and f_SWis typi-

cally 500kHz.

35

www.national.com

TABLE 13. Suggested Inductors

Manufacturer Part Number

Value

10µH

22µH

10µH

Size

Rating

820mA

340mA

530mA

800mA

650mA

520mA

DC Resistance

0.25Ω

TDK

VLF3014ST-100MR82

2.8mm × 3mm × 1.4mm

2.8mm × 3mm × 1mm

2.5mm × 2mm × 1mm

VLF3010ST-220MR34

VLF3010ST-100MR53

VLF4010ST-100MR80

VLS252010T-100M

LPS3008-103ML

0.81Ω

TDK

0.41Ω

TDK

0.25Ω

TDK

0.71Ω

Coilcraft

2.95mm × 2.95mm ×

0.8mm

0.65Ω

Coilcraft

LPS3008-223ML

LPS3010-103ML

LPS3010-223ML

22µH

10µH

22µH

2.95mm × 2.95mm ×

0.8mm

340mA

550mA

360mA

1.5Ω

0.54Ω

1.2Ω

2.95mm × 2.95mm ×

0.9mm

2.95mm × 2.95mm ×

0.9mm

Coilcraft

TOKO

XPL2010-103ML

10µH

1.9mm × 2mm × 1mm

2mm × 2mm × 1mm

3mm × 3.2mm × 1mm

610mA

470mA

600mA

0.56Ω

0.91Ω

0.46Ω

EPL2010-103ML

DE2810C-1117AS-100M

DIODE SELECTION

ble 14 lists various diodes that can be used with the LM3530.

For 25V OVP devices a 30V Schottky is adequate. For 40V

OVP devices, a 40V Schottky diode should be used.

The diode connected between SW and OUT must be a Schot-

tky diode and have a reverse breakdown voltage high enough

to handle the maximum output voltage in the application. Ta-

TABLE 14. Suggested Diodes

Manufacturer

Diodes Inc

Part Number

B0540WS

Value

Size

Rating

Schottky

SOD-323 () 40V/500mA

Diodes Inc

SDM20U40

SOD-523

(1.2mm ×

0.8mm ×

0.6mm)

40V/200mA

40V/250mA

On Semiconductor

NSR0340V2T1G

NSR0240V2T1G

Schottky

SOD-523

(1.2mm ×

0.8mm ×

0.6mm)

SOD-523

(1.2mm ×

0.8mm ×

0.6mm)

BOARD LAYOUT GUIDELINES

through the diode and the output capacitor can cause a large

voltage spike at the SW pin and the OVP pin due to parasitic

inductance in the step current conducting path (V = Ldi/dt).

Board layout guidelines are geared towards minimizing this

electric field coupling and conducted noise. Figure 26 high-

lights these two noise generating components.

The LM3530 contains an inductive boost converter which

sees a high switched voltage (up to 40V) at the SW pin, and

a step current (up to 900mA) through the Schottky diode and

output capacitor each switching cycle. The high switching

voltage can create interference into nearby nodes due to

electric field coupling (I = CdV/dt). The large step current

www.national.com

36

300866100

FIGURE 26. LM3530's Boost Converter Showing Pulsed Voltage at SW (High dV/dt) and

Current Through Schottky and C_OUT(High dI/dt)

The following lists the main (layout sensitive) areas of the

Output Capacitor Placement

LM3530 in order of decreasing importance:

The output capacitor is in the path of the inductor current dis-

charge path. As a result C_OUTsees a high current step from

0 to I_PEAKeach time the switch turns off and the Schottky diode

turns on. Any inductance along this series path from the cath-

ode of the diode through C_OUTand back into the LM3530's

GND pin will contribute to voltage spikes (V_SPIKE= L_{P_}× dI/

dt) at SW and OUT which can potentially over-voltage the SW

pin, or feed through to GND. To avoid this, C_OUT+ must be

connected as close as possible to the Cathode of the Schottky

diode and C_OUT- must be connected as close as possible to

the LM3530's GND bump. The best placement for C_OUTis on

the same layer as the LM3530 so as to avoid any vias that

can add excessive series inductance (see Figure 28, Figure

29, and Figure 30).

Output Capacitor

•

Schottky Cathode to C_OUT

C_OUT- to GND

+

Schottky Diode

•

SW Pin to Schottky Anode

Schottky Cathode to _COUT

+

Inductor

SW Node PCB capacitance to other traces

•

Input Capacitor

•

CIN+ to IN pin

CIN- to GND

37

www.national.com

Schottky Diode Placement

coming from the input capacitor each time the switch turns on.

Close placement of the input capacitor to the IN pin and to the

GND pin is critical since any series inductance between IN

and C_IN+ or C_IN- and GND can create voltage spikes that

could appear on the V_INsupply line and in the GND plane.

The Schottky diode is in the path of the inductor current dis-

charge. As a result the Schottky diode sees a high current

step from 0 to I_PEAKeach time the switch turns off and the

diode turns on. Any inductance in series with the diode will

cause a voltage spike (V_SPIKE= L_{P_}× dI/dt) at SW and OUT

which can potentially over-voltage the SW pin, or feed through

to V_OUTand through the output capacitor and into GND. Con-

necting the anode of the diode as close as possible to the SW

pin and the cathode of the diode as close as possible to C_OUT

+ will reduce the inductance (L_{P_}) and minimize these voltage

spikes (see Figure 28, Figure 29 , andFigure 30 ).

Close placement of the input bypass capacitor at the input

side of the inductor is also critical. The source impedance (in-

ductance and resistance) from the input supply, along with the

input capacitor of the LM3530, form a series RLC circuit. If the

output resistance from the source (R_S) is low enough the cir-

cuit will be underdamped and will have a resonant frequency

(typically the case). Depending on the size of L_Sthe resonant

frequency could occur below, close to, or above the LM3530's

switching frequency. This can cause the supply current ripple

to be:

Inductor Placement

The node where the inductor connects to the LM3530’s SW

bump has 2 issues. First, a large switched voltage (0 to

V_OUT+ V_{F_SCHOTTKY}) appears on this node every switching

cycle. This switched voltage can be capacitively coupled into

nearby nodes. Second, there is a relatively large current (in-

put current) on the traces connecting the input supply to the

inductor and connecting the inductor to the SW bump. Any

resistance in this path can cause large voltage drops that will

negatively affect efficiency.

1. Approximately equal to the inductor current ripple when

the resonant frequency occurs well above the LM3530's

switching frequency;

2. Greater then the inductor current ripple when the

resonant frequency occurs near the switching frequency;

and

3. Less then the inductor current ripple when the resonant

frequency occurs well below the switching frequency.

Figure 27 shows the series RLC circuit formed from the

output impedance of the supply and the input capacitor.

The circuit is re-drawn for the AC case where the V_IN

supply is replaced with a short to GND and the LM3530

+ Inductor is replaced with a current source (ΔI_L).

Equation 1is the criteria for an underdamped response. Equa-

tion 2 is the resonant frequency. Equation 3 is the approxi-

mated supply current ripple as a function of L_S, R_S, and C_IN.

To reduce the capacitively coupled signal from SW into near-

by traces, the SW bump to inductor connection must be

minimized in area. This limits the PCB capacitance from SW

to other traces. Additionally, the other traces need to be rout-

ed away from SW and not directly beneath. This is especially

true for high impedance nodes that are more susceptible to

capacitive coupling such as (SCL, SDA, HWEN, PWM, and

possibly ASL1 and ALS2). A GND plane placed directly below

SW will dramatically reduce the capacitance from SW into

nearby traces

As an example, consider a 3.6V supply with 0.1Ω of series

resistance connected to C_INthrough 50nH of connecting

traces. This results in an underdamped input filter circuit with

a resonant frequency of 712kHz. Since the switching fre-

quency lies near to the resonant frequency of the input RLC

network, the supply current is probably larger then the induc-

tor current ripple. In this case using equation 3 from Figure

27 the supply current ripple can be approximated as 1.68×'s

the inductor current ripple. Increasing the series inductance

(L_S) to 500nH causes the resonant frequency to move to

around 225kHz and the supple current ripple to be approxi-

mately 0.25×'s the inductor current ripple.

To limit the trace resistance of the VBATT to inductor con-

nection and from the inductor to SW connection, use short,

wide traces (see Figure 28, Figure 29 , and Figure 30).

Input Capacitor Selection and Placement

The input bypass capacitor filters the inductor current ripple,

and the internal MOSFET driver currents during turn on of the

power switch.

The driver current requirement can range from 50mA at 2.7V

to over 200mA at 5.5V with fast durations of approximately

10ns to 20ns. This will appear as high di/dt current pulses

www.national.com

38

30086628

FIGURE 27. Input RLC Network

39

www.national.com

Example Layouts

The following three figures show example layouts which apply

the required proper layout guidelines. These figures should

be used as guides for laying out the LM3530's circuit.

300866a1

FIGURE 28. Layout Example #1

300866a2

FIGURE 29. Layout Example #2

www.national.com

40

300866a3

FIGURE 30. Layout Example #3

TABLE 15. Application Circuit Component List

Compon-

ent

Manufact-

urer

Part Number

Value

10 µH

Size

Current/Voltage

Rating

L

TDK

VLF3014ST-

100MR82

3mm × 3mm × I_SAT= 820mA

1.4mm

COUT

CIN

Murata

GRM21BR71

H105KA12

1 µF

0805

50V

GRM188B31

A225KE33

2.2 µF

0603

10V

D1

Diodes Inc.

Avago

B0540WS

Schottky

SOD-323

40V/500mA

ALS1

APDS-9005

Ambient

Light

Sensor

1.6mm x

1.5mm ×

0.6mm

0 to 1100 Lux

ALS2

Avago

APDS-9005

Ambient

Light

Sensor

1.6mm x

1.5mm ×

0.6mm

0 to 1100 Lux

41

www.national.com

Physical Dimensions inches (millimeters) unless otherwise noted

12-Bump Ultra Thin Micro SMD Package

For Ordering, Refer to Ordering Information Table

NS Package Number UMD12

X1 = 1.215 mm (±0.1 mm), X2 = 1.615 mm (±0.1 mm), X3 = 0.425 mm

12-Bump Thin Micro SMD Package

For Ordering, Refer to Ordering Information Table

NS Package Number TMD12

X1 = 1.215 mm (±0.1 mm), X2 = 1.615 mm (±0.1 mm), X3 = 0.625 mm

www.national.com

42

Notes

43

www.national.com

Notes

For more National Semiconductor product information and proven design tools, visit the following Web sites at:

www.national.com

Products

www.national.com/amplifiers

Design Support

www.national.com/webench

Amplifiers

WEBENCH® Tools

App Notes

Audio

www.national.com/audio

www.national.com/timing

www.national.com/adc

www.national.com/interface

www.national.com/lvds

www.national.com/power

www.national.com/appnotes

www.national.com/refdesigns

www.national.com/samples

www.national.com/evalboards

www.national.com/packaging

www.national.com/quality/green

www.national.com/contacts

www.national.com/quality

www.national.com/feedback

www.national.com/easy

Clock and Timing

Data Converters

Interface

Reference Designs

Samples

Eval Boards

LVDS

Packaging

Power Management

Green Compliance

Distributors

Switching Regulators www.national.com/switchers

LDOs

www.national.com/ldo

www.national.com/led

www.national.com/vref

www.national.com/powerwise

Quality and Reliability

Feedback/Support

Design Made Easy

Applications & Markets

Mil/Aero

LED Lighting

Voltage References

PowerWise® Solutions

www.national.com/solutions

www.national.com/milaero

www.national.com/solarmagic

www.national.com/training

Serial Digital Interface (SDI) www.national.com/sdi

Temperature Sensors

PLL/VCO

www.national.com/tempsensors SolarMagic™

www.national.com/wireless

PowerWise® Design

University

THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION

(“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY

OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO

SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS,

IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS

DOCUMENT.

TESTING AND OTHER QUALITY CONTROLS ARE USED TO THE EXTENT NATIONAL DEEMS NECESSARY TO SUPPORT

NATIONAL’S PRODUCT WARRANTY. EXCEPT WHERE MANDATED BY GOVERNMENT REQUIREMENTS, TESTING OF ALL

PARAMETERS OF EACH PRODUCT IS NOT NECESSARILY PERFORMED. NATIONAL ASSUMES NO LIABILITY FOR

APPLICATIONS ASSISTANCE OR BUYER PRODUCT DESIGN. BUYERS ARE RESPONSIBLE FOR THEIR PRODUCTS AND

APPLICATIONS USING NATIONAL COMPONENTS. PRIOR TO USING OR DISTRIBUTING ANY PRODUCTS THAT INCLUDE

NATIONAL COMPONENTS, BUYERS SHOULD PROVIDE ADEQUATE DESIGN, TESTING AND OPERATING SAFEGUARDS.

EXCEPT AS PROVIDED IN NATIONAL’S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS, NATIONAL ASSUMES NO

LIABILITY WHATSOEVER, AND NATIONAL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY RELATING TO THE SALE

AND/OR USE OF NATIONAL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR

PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY

RIGHT.

LIFE SUPPORT POLICY

NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR

SYSTEMS WITHOUT THE EXPRESS PRIOR WRITTEN APPROVAL OF THE CHIEF EXECUTIVE OFFICER AND GENERAL

COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:

Life support devices or systems are devices which (a) are intended for surgical implant into the body, or (b) support or sustain life and

whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected

to result in a significant injury to the user. A critical component is any component in a life support device or system whose failure to perform

can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness.

National Semiconductor and the National Semiconductor logo are registered trademarks of National Semiconductor Corporation. All other

brand or product names may be trademarks or registered trademarks of their respective holders.

For the most current product information visit us at www.national.com

National Semiconductor

Americas Technical

Support Center

National Semiconductor Europe

Technical Support Center

Email: europe.support@nsc.com

National Semiconductor Asia

Pacific Technical Support Center

Email: ap.support@nsc.com

National Semiconductor Japan

Technical Support Center

Email: jpn.feedback@nsc.com

Email: support@nsc.com

Tel: 1-800-272-9959

www.national.com


型号：	LM3530UMX-40NOPB
厂家：	National Semiconductor
描述：	IC LED DISPLAY DRIVER, PBGA12, 1.215 X 1.615 MM, 0.425 MM HEIGHT, USMD-12, Display Driver 驱动接口集成电路
文件：	总45页 (文件大小：3101K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LM3530UMX-40NOPB [NSC]

相关型号：

LM3532

LM3532TME-40A/NOPB

LM3532TME-40ANOPB

LM3532TMX-40A/NOPB

LM3532TMX-40ANOPB

LM3532_13

LM3533

LM3533TME-40

LM3533TME-40/NOPB

LM3533TME-40A

LM3533TME-40A/NOPB

LM3533TMX-40