LM3532_技术文档

LM3532

High Efficiency White LED Driver with Programmable Ambient Light

Sensing Capability and I2C-Compatible Interface

General Description

Features

The LM3532 is a 500 kHz fixed frequency asynchronous

boost converter which provides the power for 3 high-voltage,

low-side current sinks. The device is programmable over an

I²C-compatible interface and has independent current control

for all three channels. The adaptive current regulation method

allows for different LED currents in each current sink thus al-

lowing for a wide variety of backlight + keypad applications.

Drives up to 3 Parallel High-Voltage LED Strings at 40V

●

each with up to 90% efficiency

0.4% Typical Current Matching Between Strings

●

256 Level Logarithmic and Linear Brightness Control with

14-Bit Equivalent Dimming

I²C-compatible Interface

●

Direct Read Back of Ambient Light Sensor via 8-bit ADC

The main features of the LM3532 include dual ambient light

sensor inputs each with 32 internal voltage setting resistors,

8-bit logarithmic and linear brightness control, dual external

PWM brightness control inputs, and up to 1000:1 dimming

ratio with programmable fade in and fade out settings.

Programmable Dual Ambient Light Sensor Inputs with

Internal Sensor Gain Selection

Dual External PWM Inputs for LED Brightness Adjustment

●

Independent Current String Brightness Control

The LM3532 is available in a 16-bump, 0.4mm pitch thin micro

SMD (1.745 mm x 1.845 mm x 0.6 mm). The device operates

over a 2.7V to 5.5V input voltage range and the −40°C to +85°

C temperature range.

Programmable LED Current Ramp Rates

40V Over-Voltage Protection

1A Typical Current Limit

●

Applications

Power Source for White LED Backlit LCD Displays

●

Programmable Keypad Backlight

Typical Application Circuit

301154100

PRODUCTION DATA information is current as of

publication date. Products conform to specifications per

the terms of the Texas Instruments standard warranty.

Production processing does not necessarily include

testing of all parameters.

301154 SNVS653B

LM3532

Application Circuit Component List

Current/Voltage

Rating

(Resistance)

Package

Designator

Component Manufacturer's Part Number Value

Size (mm)

1.745 mm x 1.845 mm x 0.6 mm

3.9 mm x 3.9 mm x 1.7 mm

0805

White LED

Driver

National Semiconductor

LM3532

TMD16FKA

L

COILCRAFT

LPS4018-103ML

10 µH

1µF

1A (R_DC= 0.2Ω)

COUT

CIN

Murata

GRM21BR71H105KA12L

0805

0603

50V

10V

Murata

2.2 µF

0603

GRM188R71A225KE15D

Connection Diagram

30115402

16-Bump (1.745 mm × 1.845 mm × 0.6 mm)

micro SMD Package TMD16FKA

Ordering Information

Top Mark

Lead

Supplied As

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

and die run code, second line is

voltage option)

Order Number

Package Type

Free?

LM3532TME-40A NOPB 16-Bump micro SMD 250 units, Tape-and-

Reel, No Lead

Yes

XX

D34

LM3532TMX-40A NOPB 16-Bump micro SMD 3000 units, Tape-and-

Reel, No Lead

XX

D34

2

LM3532

Pin Descriptions/Functions

Name

Description

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

terminal of the output capacitor.

A1

OVP

Input Terminal to High Voltage Current Sink #3 (40V max). The boost converter regulates the

minimum of ILED1, ILED2, or ILED3 to 0.4V.

A2

A3

A4

ILED3

ILED2

ILED1

Input Terminal to High Voltage Current Sink #2 (40V max). The boost converter regulates the

minimum of ILED1, ILED2, or ILED3 to 0.4V.

Input Terminal to High Voltage Current Sink #1 (40V max). The boost converter regulates the

minimum of ILED1, ILED2, or ILED3 to 0.4V.

B1

B2

ALS1

ALS2

Ambient Light Sensor Input 1.

Ambient Light Sensor Input 2.

Active High Hardware Enable. Pull this pin high to enable the LM3532. HWEN is a high

impedance input.

B3

HWEN

B4

C1

C2

IN

Input Voltage Connection. Bypass IN to GND with a minimum 2.2 µF ceramic capacitor.

External PWM Brightness Control Input 2.

PWM2

PWM1

External PWM Brightness Control Input 1.

Programmable Interrupt Pin. INT is an open drain output that pulls low when the ALS changes

zones.

C3

INT

C4

D1

D2

D3

D4

GND

SDA

SCL

T0

Ground

Serial Data Connection for I²C-Compatible Interface

Serial Clock Connection for I²C-Compatible Interface

Unused test input. This pin must be tied externally to GND for proper operation.

Drain Connection for boost converters internal NFET

SW

3

LM3532

Absolute Maximum Ratings (Note 1, Note 2)

If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for

availability and specifications.

V_INto GND

−0.3V to +6V

V_SW, V_OVP, V_ILED1, V_ILED2, V_ILED3

to GND

−0.3V to +45V

V_SCL, V_SDA, V_ALS1, V_ALS2, V_PWM1

,

V_PWM2, V_INT, V_HWEN, V_T0to GND

−0.3V to +6V

Internally Limited

+150°C

Continuous Power Dissipation

Junction Temperature (T_J-MAX

Storage Temperature Range

)

−65°C to +150°C

Maximum Lead Temperature

(Soldering, 10s) (Note 3)

ESD Rating

+300°C

2.0 kV

Human Body Model (Note

9)

Operating Ratings (Note 1, Note 2)

V_INto GND

2.7V to 5.5V

V_SW, V_OVP, V_ILED1, V_ILED2

V_ILED3to GND

,

0 to +40V

Junction Temperature Range

−40°C to +125°C

(T_J)(Note 4, Note 5)

Thermal Properties

ESD Caution Notice

Thermal Resistance Junction

to Ambient (T_JA)(Note 6)

61.3°C/W

National Semiconductor recommends that all integrated circuits be handled with appropriate ESD precautions. Failure to observe

proper ESD handling techniques can result in damage to the device.

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

(−30°C ≤ T_A≤ +85°C). Unless otherwise specified V_IN= 3.6V.

Symbol

I_LED(1/2/3)

Parameter

Conditions

Min

Typ

Max

21.8

Units

Output Current Regulation

Accuracy (ILED1, ILED2 or

ILED3)

2.7V ≤ V_IN≤ 5.5V, ControlX Full-

Scale Current Register = 0xF3,

Brightness Code = 0xFF

18.68

20.2

mA

I_{MATCH (Note 10),}

ILED2 to ILED3 Current Matching

−2

0.3

400

200

2

%

2.7V ≤ V_IN≤ 5.5V

(Note 11)

Regulated Current Sink

Headroom Voltage

V_{REG_CS}

mV

I_LED= 95% of nominal, I_LED= 20.2

Current Sink Minimum

Headroom Voltage

V_HR

240

mA

R_DSON

I_CL

I_SW= 100 mA

NMOS Switch On Resistance

NMOS Switch Current Limit

0.25

Ω

880

40

1000

1120

42

mA

2.7V ≤ V_IN≤ 5.5V

41

1

ON Threshold, 2.7V ≤ V_IN≤ 5.5V

Hysteresis

V_OVP

Output Over-Voltage Protection

V

f_SW

Switching Frequency

Maximum Duty Cycle

Minimum Duty Cycle

450

500

94

10

550

kHz

%

2.7V ≤ V_IN≤ 5.5V

D_MAX

D_MIN

%

Quiescent Current into IN, Device ILED1 = ILED2 = ILED3 = 20.2

Not Switching mA, feedback disabled.

I_Q

490

µA

4

LM3532

Symbol

I_{Q_SW}

Parameter

Switching Supply Current

Shutdown Current

Conditions

I_LED1= I_LED2= I_LED3= 20 mA,

V_OUT= 32V

Min

Typ

1.35

1

Max

2

Units

mA

I_SHDN

µA

2.7V ≤ V_IN≤ 5.5V, HWEN = GND

Full-Scale Current =20.2 mA

Brightness code = 0x01, Mapping

= Exponential

Minimum LED Current in ILED1,

ILED2 or ILED3

I_{LED_MIN}

9.5

µA

°C

Thermal Shutdown

Hysteresis

+140

15

T_SD

LOGIC INPUTS/OUTPUTS (PWM1, PWM2, HWEN, SCL, SDA, INT)

V_IL

Input Logic Low

0

0.4

V_IN

0.4

2.7V ≤ V_IN≤ 5.5V

V

V_IH

V_OL

Input Logic High

1.2

Output Logic Low (SCL, INT)

V

2.7V ≤ V_IN≤ 5.5V, I_LOAD= 3mA

PWM Input Internal Pulldown

Resistance (PWM1, PWM2)

R_PWM

100

kΩ

I²C-COMPATIBLE TIMING SPECIFICATIONS (SCL, SDA, see )

t₁

t₂

t₃

SCL (Clock Period)

2.5

100

0

µs

ns

Data In Setup Time to SCL High

Data Out Stable After SCL Low

SDA Low Setup Time to SCL Low

(Start)

100

ns

t₄

SDA High Hold Time After SCL

High (Stop)

t₅

AMBIENT LIGHT SENSOR INPUTS (ALS1, ALS2)

ALS1, ALS2 Resistor Select

Register = 0x0F,

ALS Pin Internal Pulldown

R_ALS1, R_ALS2

Resistors

2.29

2.44

2.59

2.06

kΩ

2.7V ≤ V_IN≤ 5.5V

Ambient Light Sensor Reference

V_{ALS_REF}

Voltage

1.94

0.8

2

V

ALS Input Offset Voltage

V_OS

2.5

4.2

mV

2.7V ≤ V_IN≤ 5.5V

(Code 0 to 1 transition - V_LSB

Conversion Time

)

t_CONV

LSB

154

µs

ADC Resolution

7.84

mV

5

LM3532

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 Texas Instruments 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 102 mm x 76 mm x 1.6 mm with a 2 x 1 array of thermal vias. The ground plane on the

board is 50 mm x 50 mm. Thickness of copper layers are 36 µm/18 µm/18 µm/36 µm (1.5 oz/1oz/1oz/1.5 oz). 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 60°C/W to 110°C/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 numbers are not guaranteed, but do represent the most likely norm.

Unless otherwise specified, conditions for typical specifications are: V_IN= 3.6V and T_A= +25°C.

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 100 pF capacitor discharged through 1.5 kΩ resistor into each pin. (MIL-STD-883 3015.7).

Note 10: All Current sinks for the matching spec are assigned to the same Control Bank.

Note 11: LED current sink matching between ILED2 and ILED3 is given by taking the difference between either (ILED2 or ILED3) and the average current between

the two, and dividing by the average current between the two (ILED2/3 – ILED(AVE))/ILED(AVE). This simplifies to (ILED2 – ILED3)/(ILED2 + ILED3). In this test,

both ILED2 and ILED3 are assigned to Bank A.

6

LM3532

Typical Performance Characteristics V_IN= 3.6V, LEDs (VF = 3.2V@20 mA, T_A= 25°C), C_OUT= 1µF,

C_IN= 2.2 µF, L = Coilcraft LPS4018 (10 µH or 22 µH), T_A= +25°C unless otherwise specified.

Efficiency vs V_IN

Single String, ILED = 20.2mA

L = LPS4018-103ML (10µH)

30115451

30115452

Efficiency vs V_IN

Dual String, ILED = 20.2mA per string

L = LPS4018-103ML (10µH)

30115454

30115453

Efficiency vs V_IN

Triple String, ILED = 20.2mA per string

L = LPS4018-103ML (10µH)

30115455

30115456

7

LM3532

Efficiency vs V_IN

Single String, ILED = 20.2mA per string

L = LPS4018-223ML (22µH)

30115457

30115458

Efficiency vs V_IN

Dual String, ILED = 20.2mA per string

L = LPS4018-223ML (22µH)

30115459

30115460

Efficiency vs V_IN

Triple String, ILED = 20.2mA per string

L = LPS4018-223ML (22µH)

30115461

30115462

8

LM3532

Efficiency vs I_LED

Triple String, VIN = 3.6V

L = LPS4018-103ML (10µH)

30115463

30115464

Efficiency vs I_LED

Triple String, VIN = 3.6V

L = LPS4018-223ML (22µH)

30115465

30115466

Shutdown Current vs VIN

HWEN = GND

Current Sink Matching vs VIN

ILED2 to ILED3

30115489

30115479

9

LM3532

Current Sink Matching vs VIN

ILED1 to ILED2 to ILED3

(ΔILED is worst case difference between all three strings)

ALS Resistance vs VIN

R_ALS1, (2.44kΩ setting)

30115478

30115482

ALS Resistor Matching vs VIN

Integral Non Linearity vs Code

(Endpoint Method)

(2.44kΩ setting)

30115476

30115480

Differential Non Linearity vs Code

Peak to Peak LED Current Ripple vs f_PWM

30115490

30115477

10

LM3532

LED Current vs Headroom Voltage

30115473

Operational Description

40V BOOST CONVERTER

The LM3532 contains a 40V maximum output voltage, asynchronous boost converter with an integrated 250 mΩ switch and three

low-side current sinks. Each low-side current sink is independently programmable from 0 to 30 mA.

HARDWARE ENABLE INPUT

HWEN is the LM3532's global hardware enable input. This pin must be driven high to enable the device. HWEN is a high-impedance

input so cannot be left floating. Typically HWEN would be connected through a pullup resistor to the logic supply voltage or driven

high from a micro controller. Driving HWEN low will place the LM3532 into a low-current shutdown state and force all the internal

registers to their power on reset (POR) states.

FEEDBACK ENABLE

Each current sink can be set for feedback enable or feedback disable. When feedback is enabled, the boost converter maintains

at least 400 mV across each active current sink. This causes the boost output voltage (VOUT) to raise up or down depending on

how many LEDs are placed in series in the highest voltage string. This ensures there is a minimum headroom voltage across each

current sink. The potential drawback is that for large differentials in LED counts between strings, the LED voltage can be drastically

different causing the excess voltage in the lower LED string to be dropped across its current sink. In situations where there are

other voltage sources available, or where the LED count is low enough to use VIN as the power source, the feedback can be

disabled on the specific current sink. This allows for the current sink to be active, but eliminates its control over the boost output

voltage (see Figure 1). In this situation care must be taken to ensure there is always at least 400 mV of headroom voltage across

each active current sink to avoid the current from going out of regulation. Control over the feedback enable/disable is programmable

via the Feedback Enable Register (see Table 13) .

11

LM3532

30115437

FIGURE 1. LM3532 Feedback Enable/Disable

LM3532 CURRENT SINK CONFIGURATION

Control of the LM3532’s three current sinks is done by configuring the three internal control banks (Control A, Control B, and Control

C) (see Figure 2). Any of the current sinks (ILED1, ILED2, or ILED3) can be mapped to any of the three control banks. Configuration

of the control banks is done via the Output Configuration register.

30115414

FIGURE 2. LM3532 Functional Control Diagram

12

LM3532

PWM INPUTS

The LM3532 provides two PWM inputs (PWM1 and PWM2) which can be mapped to any of the three Control Banks. PWM input

mapping is done through the Control A PWM Configuration register, the Control B PWM Configuration register, and the Control C

PWM Configuration register.

Both PWM inputs (PWM1 and PWM2) feed into internal level shifters and lowpass filters. This allows the PWM inputs to accept

logic level signals and convert them to analog control signals which can control the assigned Control Banks LED current. The

internal lowpass filter at each PWM input has a typical corner frequency of 540 Hz with a Q of 0.5. This gives a low end useful

PWM frequency of around 2kHz. Frequencies lower then this will cause the LED current to show larger ripple and result in non-

linear behavior vs. duty cycle due to the response time of the boost circuit. The upper boundary of the PWM frequency is greater

than 100 kHz. Frequencies above 200 kHz will begin to show non linear behavior due to propagation delays through the PWM

input circuitry.

FULL-SCALE LED CURRENT

There are 32 programmable full-scale current settings for each of the three control banks (Control A, Control B, and Control C).

Each control bank has its own independent full-scale current setting (I_{LED_FULL_SCALE}). Full-scale current for the respective Control

Bank is set via the Control A Full-Scale Current Register, the Control B Full-Scale Current Register, and the Control C Full-Scale

Current Register (see Table 12).

LED CURRENT RAMPING

The LM3532 provides 4 methods to control the rate of rise or fall of the LED current during these events:

1. Startup from 0 to the initial target

2. Shutdown

3. Ramp up from one brightness level to the next

4. Ramp down from one brightness level to the next

See Table 4 and Table 5.

STARTUP AND SHUTDOWN CURRENT RAMPING

The startup and shutdown ramp rates are independently programmable in the startup/Shutdown Ramp Rate Register (see Table

4). There are 8 different startup and 8 different shutdown ramp rates. The startup ramp rates are independently programmable

from the shutdown ramp rates, but not independently programmable for each Control Bank. For example, programming a startup

or shutdown ramp rate, programs the same ramp rate for each Control Bank.

RUN TIME RAMP RATES

Current ramping from one brightness level to the next is programmed via the Run Time Ramp Rate Register (see Table 5). There

are 8 different ramp-up and 8 different ramp-down rates. The ramp-up rate is independently programmable from the ramp-down

rate, but not independently programmable for each Control Bank. For example, programming a ramp-up or a ramp-down rate

programs the same rate for each Control Bank.

LED CURRENT MAPPING MODES

All LED current brightness codes are 8 bits (256 different levels), where each bit represents a percentage of the programmed full-

scale current setting for that particular Control Bank. The percentage of the full-scale current is different depending on which

mapping mode is selected. The mapping mode can be either exponential or linear. Mapping mode is selected via bit [1] of the

Control A, B, or C Brightness Configuration Registers.

EXPONENTIAL CURRENT MAPPING MODE

In exponential mapping mode, the backlight code to LED current approximates the following equation:

where Code is the 8-bit code in the programmed brightness register and D_PWMis the duty cycle of the PWM input that is assigned

to the particular control bank. For the exponential mapped mode (Figure 3) shows the typical response of % full-scale current setting

vs 8-bit brightness code.

13

LM3532

30115493

FIGURE 3. Exponential Mapping Response

LINEAR CURRENT MAPPING

In linear mapping mode the backlight code to LED current approximates the following equation:

where Code is the 8-bit code in the programmed brightness register and DPWM is the duty cycle of the PWM input that is assigned

to the particular control bank. For the linear mapped mode (Figure 4) shows the typical response of % full-scale current setting vs

8-bit brightness code.

30115494

FIGURE 4. Linear Mapping Response

LED CURRENT CONTROL

Once the Full-Scale Current is set, control of the LM3532’s LED current can be done via 2 methods:

1. I²C Current Control

2. Ambient Light Sensor Current Control

I²C current control allows for the direct control of the LED current by writing directly to the specific brightness register. In ambient

light sensor current control the LED current is automatically set by the ambient light sensor interface.

I²C CURRENT CONTROL

I²C Current Control is accomplished by using one of the Zone Target Registers (for the respective Control Bank) as the brightness

register. This is done via bits[4:2] of the Control (A, B, or C) Brightness Registers (see Table 9, Table 10, and Table 11). For

14

LM3532

example, programming bits[4:2] of the Control A Brightness Register with (000) makes the brightness register for Bank A (in I²C

Current Control) the Control A Zone Target 0 Register.

I²C CURRENT CONTROL WITH PWM

I²C Current Control can also incorporate the PWM duty cycle at one of the PWM inputs (PWM1 or PWM2). In this situation the LED

current is then a function of both the code in the programmed brightness register and the duty cycle input into the assigned PWM

inputs (PWM1 or PWM2).

ASSIGNING and ENABLING A PWM INPUT

To make the backlight current a function of the PWM input duty cycle, one of the PWM inputs must first be assigned to a particular

Control Bank. This is done via bit [0] of the Control A, B, or C PWM Registers (see Table 6, Table 7, or Table 8). After assigning a

PWM input to a Control Bank, the PWM input is then enabled via bits [6:2] of the Control A/B/C PWM Enable Registers. Each

enable bit is associated with a specific Zone Target Register in I²C Current Control. For example, if Control A Zone Target 0 Register

is configured as the brightness register, then to enable PWM for that brightness register, Control A PWM bit [2] would be set to 1.

ENABLING A CURRENT SINK

Once the brightness register and PWM inputs are configured in I²C Current Control, the current sinks assigned to the specific

control bank are enabled via the Control Enable Register (see Table 14). Table 1 below shows the possible configurations for

Control Bank A in I²C Current Control. This table would also apply to Control Bank B and Control Bank C.

TABLE 1. I²C Current Control + PWM Bit Settings (For Control Bank A)

Current Sink

Brightness Register

PWM Select

PWM Enable

Current Sink Enable

Assignment

Output Configuration Control A Brightness Control A PWM

Register

Bits[1:0] = 00, assigns Register Bits [4:2]

ILED1 to Control Bank A 000 selects Control A

Control A PWM Register

Bit[2] is PWM enable when

Control A Zone Target 0 is

configured as the brightness

register

Control Enable

Register Bit [0]

0 = Bank A Disabled

1 = Bank A Enabled

Configuration

Register Bit[0]

0 selects PWM1

1 selects PWM2

Bits[3:2] = 00 assigns

Zone Target 0 as

ILED2 to Control Bank A brightness register

Bits[5:4] = 00, assigns 001 selects Control A

ILED3 to Control Bank A Zone Target 1

brightness register

Bit[3] is PWM enable when

Control A Zone Target 1 is

configured as the brightness

register

010 selects Control A

Zone Target 2

brightness register

011 selects Control A

Bit[4] is PWM enable when

Control A Zone Target 2 is

configured as the brightness

register

Zone Target 3

brightness register

1XX selects Control A

Zone Target 4

Bit[5] is PWM enable when

Control A Zone Target 3 is

configured as the brightness

register

brightness register

Bit[6] is PWM enable when

Control A Zone Target 4 is

configured as the brightness

register

AMBIENT LIGHT SENSOR CURRENT CONTROL

In Ambient Light Sensor (ALS) Current Control the LM3532’s backlight current is automatically set based upon the voltage at the

ambient light sensor inputs (ALS1 and/or ALS2). These inputs are designed to connect to the outputs of analog ambient light

sensors. Each ALS input has an active input voltage range of 0 to 2V.

ALS LIGHT SENSOR RESISTORS

The LM3532 offers 32 separate programmable internal resistors at the ALS1 and ALS2 inputs. These resistors take the ambient

light sensor's output current and convert it into a voltage. The value of the resistor selected is typically chosen such that the ambient

light sensors output voltage swing goes from 0 to 2V across the intended measured ambient light (LUX) range. The ALS resistor

values are programmed via the ALS1 and ALS2 Resistor select registers (see Table 15). The code to resistor selection (assuming

a 2V full-scale voltage range) is shown in the following equation:

Each higher code in the specific ALS Resistor Select Register increases the allowed ALS sensor current by 54 µA ( for a 2V full-

scale). When the ALS is disabled (ALS Configuration Register bit [3] = 0) the ALS inputs are set to a high impedance mode no

15

LM3532

matter what the ALS resistor selection is. Alternatively, ALS Resistor Select Register Code 00000 will set the specific ALS input to

high impedance.

AMBIENT LIGHT ZONE BOUNDARIES

The LM3532 provides 5 ambient light brightness zones which are defined by 4 Zone Boundary Registers. The LM3532 has one

set of zone boundary registers that is shared globally by all Control Banks. As the voltage at the ALS input changes in response

to the ambient light sensors received light, the ALS voltage transitions through the 5 defined brightness zones. Each brightness

zone can be assigned a brightness target via the 5 Zone Target registers. Each Control Bank has its own set of Zone Target

registers. Therefore, in response to changes in a Brightness Zone at the ALS input, the LED current can transition to a new

brightness level. This allows for backlit LCD displays to reduce the LED Current when the ambient light is dim or increase the LED

current when the ambient light increases. Each Zone Boundary register is 8 bits with a full-scale voltage of 2V. This gives a 2V/

255 = 7.8 mV per bit. Figure 5 describes the ambient light to brightness mapping.

30115408

FIGURE 5. Ambient Light Input to Backlight Mapping

AMBIENT LIGHT ZONE HYSTERESIS

For each Zone Boundary there are two Zone Boundary Registers: a Zone Boundary High Register and a Zone Boundary Low

Register. The difference between the Zone Boundary High and Zone Boundary Low Register set points (for a specific zone) creates

the hysteresis that is required to transition between two adjacent zones. This hysteresis prevents the backlight current from oscil-

lating between zones when the ALS voltage is close to a Zone Boundary Threshold. Figure 6 describes this Zone Boundary

Hysteresis. The arrows indicate the direction of the ALS input voltage. The black dots indicate the threshold used when transitioning

to a new zone.

16

LM3532

30115410

FIGURE 6. ALS Zone Boundaries + Hysteresis

PWM ENABLED FOR A PARTICULAR ZONE

The active PWM input for a specified Control Bank can be enabled/disabled for each ALS Brightness Zone. This is done via bits

[6:2] of the corresponding Control A, B, or C PWM Registers (see Table 6, Table 7, and Table 8). For example, assuming Control

Bank A is being used, then to make the PWM input active in Zones 0, 2, and 4, but not active in Zones 1, and 3, bits[6:2] of the

Control A PWM Register would be set to (1, 0, 1, 0, 1).

ALS OPERATION

Figure 7 shows a functional block diagram of the LM3532's ambient light sensor interface.

30115425

FIGURE 7. ALS Functional Block Diagram

17

LM3532

ALS INPUT SELECT and ALS ADC INPUT

The internal 8-bit ADC digitizes the active ambient light sensor inputs (ALS1 or ALS2). The active ALS input is determined by the

bit settings of the ALS input select bits, bits [7:6] in the ALS Configuration register. The active ALS input can be the average of

ALS1 and ALS2, the maximum of ALS1 and ALS2, ALS1 only, or ALS2 only. Once the ALS input select stage selects the active

ALS input, the result is sent to the internal 8-bit ADC. For example, if the active ALS input select is set to be the average of ALS1

and ALS2, then the voltage at ALS1 and ALS2 is first averaged, then applied to the ADC. The output of the ADC (ADC Register)

will be the digitized average value of ALS1 and ALS2.

The LM3532's internal ADC samples at 7.143 ksps. ADC timing is shown in Figure 8. When the ALS is Enabled (ALS Configuration

Register bit [3] = 1) the ADC begins sampling and converting the active ALS input. Each conversion takes 140 µs. After each

conversion the ADC register is updated with new data.

30115488

FIGURE 8. ADC Timing

ALS ADC READBACK

The digitized value of the LM3532's ADC is read back from the ADC Readback Register. Once the ALS is enabled the ADC begins

converting the active ALS input and updating the ALS Readback Register every 140 µs. The ADC Readback register contains the

updated data after each conversion.

ALS AVERAGING

ALS averaging is used to filter out any fast changes in the ambient light sensor inputs. This prevents the backlight current from

constantly changing due to rapid fluctuations in the ambient light. There are 8 separate averaging periods available for the ALS

inputs (see Table 17). During an average period the ADC continually samples at 7.143 ksps. Therefore, during an average period,

the ALS Averager output will be the average of 7143/t_AVE

.

ALS ADC AVERAGE READBACK

The output of the LM3532's averager is read back via the Average ADC Register. This data is the ADC register data, averaged

over the programmed ALS average time.

INITIALIZING THE ALS

On initial startup of the ALS Block, the Ambient Light Zone will default to Zone 0. This allows the ALS to start off in a predictable

state. The drawback is that Zone 0 is often not representative of the true ALS Brightness Zone since the ALS inputs can get to their

ambient light representative voltage much faster then the backlight is allowed to change. In order to avoid a multiple average time

wait for the backlight current to get to its correct state, the LM3532 switches over to a fast average period (1.1 ms) on ALS startup.

This will quickly bring the ALS Brightness Zone (and the backlight current) to its correct setting (see Figure 9).

18

LM3532

30115413

FIGURE 9. ALS Startup Sequence

ASL OPERATION

The LM3532's Ambient Light Sensor Interface has 3 different algorithms that can be used to control the ambient light to backlight

current response.

ALS Algorithms

1. Direct ALS Control

2. Down Delay

For each algorithm, the ALS follows these basic rules:

ALS Rules

1. For the ALS Interface to force a change in the backlight current (to a higher zone target), the averager output must have shown

an increase for 3 consecutive average periods, or an increase and a remain at the new zone for 3 consecutive average periods.

2. For the ALS Interface to force a change in the backlight current (to a lower zone target), the averager output must have shown

a decrease for 3 consecutive average periods, or a decrease and remain at the new zone for 3 consecutive average periods.

3. If condition #1 or #2 is satisfied, and during the next average period, the averager output changes again in the same direction

as the last change, the LED current will immediately change at the beginning of the next average period.

4. If condition #1 or #2 is satisfied and the next average period shows no change in the average zone, or shows a change in the

opposite direction, then the criteria in step #1 or #2 must be satisfied again before the ALS interface can force a change in the

backlight current.

5. The Averager Output (see Figure 7) contains the zone that is determined from the most recent full average period.

6. The ALS Interface only forces a change in the backlight current at the beginning of an average period.

7. When the ALS forces a change in the backlight current the change will be to the brightness target pointed to by the zone in

the Averager Output.

DIRECT ALS CONTROL

In direct ALS control the LM3532’s ALS Interface can force the backlight current to either a higher zone target or a lower zone

target using the rules described in the ALS Rules section.

In the example of Figure 10 the plot shows the ALS voltage, the current average zone which is the zone determined by averaging

the ALS voltage in the current average period, the Averager Output which is the zone determined from the previous full average

period, and the target backlight current that is controlled by the ALS Interface. The following steps detail the Direct ALS algorithm:

1. When the ALS is enabled the ALS fast startup (1.1ms average period) quickly brings the Averager Output to the correct zone.

This takes 3 fast average periods or approximately 3.3ms.

2. The 1st average period the ALS voltage averages to Zone 4.

19

LM3532

3. The 2nd average period the ALS voltage averages to Zone 3.

4. The 3rd average period the ALS voltage averages to Zone 3 and the Averager Output shows a change from Zone 4 to Zone

3.

5. The 4th average period the ALS voltage averages to Zone 2 and the Averager Output remains at its changed state of Zone 3.

6. The 5th average period the ALS voltage averages to Zone 1. The Averager Output shows a change from Zone 3 to Zone 2.

Since this is the 3rd average period that the Averager Output has shown a change in the decreasing direction from the initial

Zone 4, the backlight current is forced to change to the current Averager Output (Zone 2's) target current.

7. The 6th average period the ALS voltage averages to Zone 2. The Averager Output changes from Zone 2 to Zone 1. Since this

is in the same direction as the previous change, the backlight current is forced to change to the current Averager Output (Zone

1's) target current.

8. The 7th average period the ALS voltage averages to Zone 3. The Averager Output changes from Zone 1 to Zone 2. Since this

change is in the opposite direction from the previous change, the backlight current remains at Zone 1's target.

9. The 8th average period the ALS voltage averages to Zone 3. The Averager Output changes from Zone 2 to Zone 3.

10. The 9th average period the ALS voltage averages to Zone 3. The Averager Output remains at Zone 3. Since this is the 3rd

average period that the Averager Output has shown a change in the increasing direction from the initial Zone 1, the backlight

current is forced to change to the current Averager Output (Zone 3's) target current.

11. The 10th average period the ALS voltage averages to Zone 4. The Averager Output remains at Zone 3.

12. The 11th average period the ALS voltage averages to Zone 4. The Averager Output changes to Zone 4.

13. The 12th average period the ALS voltage averages to Zone 4. The Averager Output remains at Zone 4.

14. The 13th average period the ALS voltage averages to Zone 4. The Averager Output remains at Zone 4. Since this is the 3rd

average period that the Averager Output has shown a change in the increasing direction from the initial Zone 3, the backlight

current is forced to change to the current Averager Output (Zone 4's) target current.

30115434

FIGURE 10. Direct ALS Control

20

LM3532

DOWN DELAY

The Down-Delay algorithm uses all the same rules from the ALS Rules section, except it provides for adding additional average

period delays required for decreasing transitions of the Averager Output, before the LED current is programmed to a lower zone

target current. The additional average period delays are programmed via the ALS Down Delay register. The register provides 32

settings for increasing the down delay from 3 extra (code 00000) up to 34 extra (code 11111). For example, if the down delay

algorithm is enabled, and the ALS Down Delay register were programmed with 0x00 (3 extra delays), then the Averager Output

would need to see 6 consecutive changes in decreasing Zones (or 6 consecutive average periods that changed and remained

lower), before the backlight current was programmed to the lower zones target current. Referring to Figure 11, assume that Down

Delay is enabled and the ALS Down Delay register is programmed with 0x02 (5 extra delays, 8 average period total delay for

downward changes in the backlight target current):

1. When the ALS is enabled the ALS fast startup (1.1 ms average period) quickly brings the Averager Output to the correct zone.

This takes 3 fast average periods or approximately 3.3 ms.

2. The first average period the ALS averages to Zone 3.

3. The second average period the ALS averages to Zone 2. The Averager Output remains at Zone 3.

4. The 3rd through 7th average period the ALS input averages to Zone 2, and the Averager Output stays at Zone 2.

5. The 8th average period the ALS input averages to Zone 4. The Averager Output remains at Zone 2.

6. The 9th and 10th average periods the ALS input averages to Zone 4. The Averager Output is at Zone 4. Since the Averager

Output increased from Zone 2 to Zone 4 and the required Down Delay time was not met (8 average periods), the backlight

current was never changed to the Zone 2's target current.

7. The 11th average period the ALS input averages to Zone 2. The Averager Output remains at Zone 4. Since this is the 3rd

consecutive average period where the Averager Output has shown a change since the change from Zone 2, the backlight

current transitions to Zone 4's target current.

8. The 12th through 26th average periods the ALS input averages to Zone 2. The Averager Output remains at Zone 2. At the

start of average period #20 the Down Delay algorithm has shown the required 8 average period delay from the initial change

from Zone 4 to Zone 2. As a result the backlight current is programmed to Zone 2's target current.

21

LM3532

30115409

FIGURE 11. ALS Down-Delay Control

INTERRUPT OUTPUT

INT is an open drain output that pulls low when the ALS is enabled and when one of the ALS inputs transitions into a new zone.

At the same time, the ALS Zone Information register is updated with the current ALS zone, and the software flag (bit 3 of the ALS

Zone Information register) is written high. A readback of the Zone Information Register will clear the software interrupt flag and

reset the INT output to the open drain state. The active pulldown at INT is typically 125Ω.

22

LM3532

Protection Features

OVERVOLTAGE PROTECTION

The LM3532’s boost converter provides open-load protection, by monitoring the OVP pin. The OVP pin is designed to connect as

close as possible to the positive terminal of the output capacitor. In the event of a disconnected load (LED current string with

feedback enabled), the output voltage will rise in order to try and maintain the correct headroom across the feedback enabled

current sinks (see Table 13). Once VOUT climbs to the OVP threshold (V_OVP) the boost converter is turned off, and switching will

stop until VOUT falls below the OVP hysteresis (V_OVP– 1V). Once the OVP hysteresis is crossed the LM3532’s boost converter

begins switching again. In open load conditions this would result in a pulsed on/off operation.

CURRENT LIMIT

The LM3532’s peak current limit in the NFET is set at typically 1A (880 mA min.). During the positive portion of the switching cycle,

if the NFET's current rises up to the current limit threshold, the NFET turns off for the rest of the switching cycle. At the start of the

next switching cycle the NFET turns on again. For loads that cause the LM3532 to hit current limit each switching cycle, the output

power can become clamped since the headroom across the feedback enabled current sinks is no longer being regulated when the

device is in current limit. See MAXIMUM OUTPUT POWER below for guidelines on how peak current affects the LM3532's max-

imum output power.

MAXIMUM OUTPUT POWER

The LM3532's maximum output power is governed by two factors: the peak current limit (I_CL= 880 mA min.), and the maximum

output voltage (V_OVP= 40V min.). When the application causes either of these limits to be reached it is possible that the proper

current regulation and matching between LED current strings will not be met.

Peak Current Limited

In the case of a peak current limited situation, when the peak of the inductor current hits the LM3532's current limit the NFET switch

turns off for the remainder of the switching period. If this happens, each switching cycle the LM3532 begins to regulate the peak

of the inductor current instead of the headroom across the current sinks. This can result in the dropout of the feedback-enabled

current sinks and the current dropping below its programmed level.

The peak current in a boost converter is dependent on the value of the inductor, total LED current (IOUT), the output voltage (VOUT)

(which is the highest voltage LED string + 0.4V regulated headroom voltage), the input voltage VIN, and the efficiency (Output

Power/Input Power). Additionally, the peak current is different depending on whether the inductor current is continuous during the

entire switching period (CCM) or discontinuous (DCM) where it goes to 0 before the switching period ends.

For Continuous Conduction Mode the peak inductor current is given by:

For Discontinuous Conduction Mode the peak inductor current is given by:

To determine which mode the circuit is operating in (CCM or DCM) it is necessary to perform a calculation to test whether the

inductor current ripple is less than the anticipated input current (IIN). If ΔIL is < then IIN then the device will be operating in CCM.

If ΔIL is > IIN then the device is operating in DCM.

Typically at currents high enough to reach the LM3532's peak current limit, the device will be operating in CCM.

The following figures show the output current and voltage derating for a 10 µH and a 22 µH inductor. These plots take equations

(1) and (2) from above and plot VOUT and IOUT with varying VIN, a constant peak current of 880 mA (ICL min), and a constant

efficiency of 85%. Using these curves can give a good design guideline on selecting the correct inductor for a given output power

requirement. A 10 µH will typically be a smaller device with lower on resistance, but the peak currents will be higher. A 22 µH

provides for lower peak currents, but to match the DC resistance of a 10 µH requires a larger sized device.

23

LM3532

30115475

30115483

FIGURE 12. Maximum Output Power (22 µH)

30115427

30115433

FIGURE 13. Maximum Output Power (10 µH)

Output Voltage Limited

When the LM3532's output voltage (highest voltage LED string + 400 mV headroom voltage) reaches 40V, the OVP threshold is

hit, and the NFET turns off and remains off until the output voltage drops 1V below the OVP threshold. Once VOUT falls below this

hysteresis, the boost converter will turn on again. In high output voltage situations the LM3532 will begin to regulate the output

voltage to the VOVP level instead of the current sink headroom voltage. This can result in a loss of headroom voltage across the

feedback enabled current sinks resulting in the LED current dropping below its programmed level.

24

LM3532

I²C-Compatible Interface

START AND STOP CONDITION

The LM3532 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 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 repeated 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.

30115403

FIGURE 14. Start and Stop Sequences

I²C-Compatible Address

The 7-bit chip address for the LM3532 is (0x38) . 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 indicates a WRITE and R/W = 1 indicates a READ. The second byte following

the chip address selects the register address to which the data will be written. The third byte contains the data for the selected

register.

30115438

FIGURE 15. I²C-Compatible Chip Address (0x38)

Transferring Data

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 acknowledge related clock pulse (9th clock pulse) is generated by the master. The

master then releases SDA (HIGH) during the 9th clock pulse. The LM3532 pulls down SDA during the 9th clock pulse, signifying

an acknowledge. An acknowledge is generated after each byte has been received.

25

LM3532

LM3532 Register Descriptions

TABLE 2. LM3532 Register Descriptions

Name

Address

Power On Reset

I²C Address

0x38 (7 bit), 0x70 for Write and 0x71 for Read

Output Configuration

Startup/Shutdown Ramp Rate

Run Time Ramp Rate

Control A PWM

0x10

0x11

0x12

0x13

0x14

0x15

0x16

0x17

0x18

0x19

0x1A

0x1B

0x1C

0x1D

0x20

0x21

0x22

0x23

0x24

0x25

0x27

0x28

0x60

0x61

0x62

0x63

0x64

0x65

0x66

0x67

0x70

0x71

0x72

0x73

0x74

0x75

0x76

0x77

0x78

0x79

0x7A

0x7B

0x7C

0x7D

0x7E

0xE4

0xC0

0x82

0xF1

0xF3

0xF1

0xF3

0xF1

0xF3

0xFF

0xF8

0xE0

0x44

0xF0

0xF8

0x00

0x35

0x33

0x6A

0x66

0xA1

0x99

0xDC

0xCC

0x33

0x66

0x99

0xCC

0xFF

0x33

0x66

0x99

0xCC

0xFF

0x33

0x66

0x99

0xCC

0xFF

Control B PWM

Control C PWM

Control A Brightness

Control A Full-Scale Current

Control B Brightness

Control B Full-Scale Current

Control C Brightness

Control C Full-Scale Current

Feedback Enable

Control Enable

ALS1 Resistor Select

ALS2 Resistor Select

ALS Down Delay

ALS Configuration

ALS Zone Information

ALS Brightness Zone

ADC

ADC Average

ALS Zone Boundary 0 High

ALS Zone Boundary 0 Low

ALS Zone Boundary 1 High

ALS Zone Boundary 1 Low

ALS Zone Boundary 2 High

ALS Zone Boundary 2 Low

ALS Zone Boundary 3 High

ALS Zone Boundary 3 Low

Control A Zone Target 0

Control A Zone Target 1

Control A Zone Target 2

Control A Zone Target 3

Control A Zone Target 4

Control B Zone Target 0

Control B Zone Target 1

Control B Zone Target 2

Control B Zone Target 3

Control B Zone Target 4

Control C Zone Target 0

Control C Zone Target 1

Control C Zone Target 2

Control C Zone Target 3

Control C Zone Target 4

26

LM3532

OUTPUT CONFIGURATION

This register configures how the three control banks are routed to the current sinks (ILED1, ILED2, ILED3)

TABLE 3. Output Configuration Register Description (Address 0x10)

Bits [5:4]

ILED3 Control

Bits [3:2]

ILED2 Control

Bits [1:0]

ILED1 Control

Bit [7:6]

Not Used

00 = ILED3 is controlled by Control 00 = ILED2 is controlled by Control A 00 = ILED1 is controlled by Control A

A PWM and Control A Brightness PWM and Control A Brightness

Registers (default) Registers (default)

PWM and Control A Brightness

Registers (default)

01 = ILED3 is controlled by Control 01 = ILED2 is controlled by Control B 01 = ILED1 is controlled by Control B

B PWM and Control B Brightness PWM and Control B Brightness

Registers Registers

PWM and Control B Brightness

Registers

1X = ILED3 is controlled by Control 1X = ILED2 is controlled by Control C 1X = ILED1 is controlled by Control

C PWM and Control C Brightness PWM and Control C Brightness

Registers Registers

C PWM and Control C Brightness

Registers

STARTUP/SHUTDOWN RAMP RATE

This register controls the ramping of the LED current in current sinks ILED1, ILED2, and ILED3 during startup and shutdown. The

startup ramp rates/step are from when the device is enabled via I²C to when the target current is reached. The Shutdown ramp

rates/step are from when the device is shut down via I²C until the LED current is 0. To start up and shut down the current sinks via

I²C, see the Control Enable Register.

TABLE 4. Startup/Shutdown Ramp Rate Register Description (Address 0x11)

Bits [7:6]

Bits [5:3]

Bits [2:0]

Shutdown Ramp

Startup Ramp

Not Used

000 = 8µs/step (2.048ms from Full-Scale to 0)

(default)

000 = 8µs/step (2.048ms from Full-Scale to 0)

(default)

001 = 1.024 ms/step (261 ms)

010 = 2.048 ms/step (522 ms)

011 = 4.096 ms/step (1.044s)

100 = 8.192 ms/step (2.088s)

101 = 16.384 ms/step (4.178s)

110 = 32.768 ms/step (8.356s)

111 = 65.536 ms/step (16.711s)

001 = 1.024 ms/step (261ms)

010 = 2.048 ms/step (522ms)

011 = 4.096 ms/step (1.044s)

100 = 8.192 ms/step (2.088s)

101 = 16.384 ms/step (4.178s)

110 = 32.768 ms/step (8.356s)

111 = 65.536 ms/step (16.711s)

RUN TIME RAMP RATE

This register controls the ramping of the current in current sinks ILED1, ILED2, and ILED3. The Run Time ramp rates/step are from

one current set-point to another after the device has reached its initial target set point from turn-on.

TABLE 5. Run Time Ramp Rate Register Description (Address 0x12)

Bits [7:6]

Bits [5:3]

Ramp Down

Bits [2:0]

Ramp Up

Not Used

000 = 8µs/step (default)

001 = 1.024 ms/step

010 = 2.048 ms/step

011 = 4.096 ms/step

100 = 8.192 ms/step

101 = 16.384 ms/step

110 = 32.768 ms/step

111 = 65.536 ms/step

001 = 1.024 ms/step

010 = 2.048 ms/step

011 = 4.096 ms/step

100 = 8.192 ms/step

101 = 16.384 ms/step

110 = 32.768 ms/step

111 = 65.536 ms/step

27

LM3532

CONTROL A PWM

This register configures which PWM input (PWM1 or PWM2) is mapped to Control Bank A and which zones the selected PWM

input is active in.

TABLE 6. Control A PWM Register Description (Address 0x13)

Bit 7

N/A

Bit 6

Bit 5

Bit 2

Bit 1

PWM Input

Polarity

Bit 0

PWM Select

Zone 4 PWM Zone 3 PWM

Enable

Zone 2 PWM Zone 1 PWM Zone 0 PWM

Enable

0 = Active

0 = Active PWM 0 = Active

0 = Active

0 = Active PWM 0 = active low 0 = PWM1

PWM input is input is disabled PWM input is PWM input is input is

polarity

input is

disabled in

Zone 4

(default)

1 = Active

in Zone 3

(default)

disabled in

Zone 2

(default)

disabled in

Zone 1

(default)

1 = Active

disabled in

Zone 0

(default)

mapped to

Control Bank

A (default)

Not Used

1 = Active PWM 1 = Active

1 = Active PWM 1 = active high 1 = PWM2 is

PWM input is input is enabled PWM input is PWM input is input is enabled polarity

mapped to

Control Bank

A

enabled in

Zone 4

in Zone 3

enabled in

Zone 2

enabled in

Zone 1

in Zone 0

(default)

CONTROL B PWM

This register configures which PWM input (PWM1 or PWM2) is mapped to Control Bank B and which zones the selected PWM

input is active in.

TABLE 7. Control B PWM Register Description (Address 0x14)

Bit 7

N/A

Bit 6

Zone 4 PWM

Enable

Bit 5

Zone 3 PWM

Enable

Bit 2

Bit 1

PWM Input

Polarity

Bit 0

PWM Select

Zone 2 PWM Zone 1 PWM Zone 0 PWM

Enable

0 = Active PWM 0 = Active PWM 0 = Active

0 = Active

0 = Active PWM 0 = active low 0 = PWM1

input is

input is disabled PWM input is PWM input is input is

polarity

input is

disabled in

Zone 4

(default)

in Zone 3

(default)

disabled in

Zone 2

(default)

disabled in

Zone 1

(default)

1 = Active

disabled in

Zone 0

(default)

mapped to

Control Bank

B (default)

Not Used

1 = Active PWM 1 = Active PWM 1 = Active

1 = Active PWM 1 = active high 1 = PWM2 is

input is enabled input is enabled PWM input is PWM input is input is enabled polarity

mapped to

Control Bank

B

in Zone 4

in Zone 3

enabled in

Zone 2

enabled in

Zone 1

in Zone 0

(default)

CONTROL C PWM

This register configures which PWM input (PWM1 or PWM2) is mapped to Control Bank C and which zones the selected PWM

input is active in.

TABLE 8. Control C PWM Register Description (Address 0x15)

Bit 7

N/A

Bit 6

Zone 4 PWM

Enable

Bit 5

Zone 3 PWM

Enable

Bit 2

Bit 1

PWM Input

Polarity

Bit 0

PWM Select

Zone 2 PWM Zone 1 PWM Zone 0 PWM

Enable

0 = Active PWM 0 = Active PWM 0 = Active

0 = Active

0 = Active PWM 0 = active low 0 = PWM1

input is

input is disabled PWM input is PWM input is input is

polarity

input is

disabled in

Zone 4

(default)

in Zone 3

(default)

disabled in

Zone 2

(default)

disabled in

Zone 1

(default)

1 = Active

disabled in

Zone 0

(default)

mapped to

Control Bank

C (default)

Not Used

1 = Active PWM 1 = Active PWM 1 = Active

1 = Active PWM 1 = active high 1 = PWM2 is

input is enabled input is enabled PWM input is PWM input is input is enabled polarity

mapped to

Control Bank

C

in Zone 4

in Zone 3

enabled in

Zone 2

enabled in

Zone 1

in Zone 0

(default)

28

LM3532

CONTROL A BRIGHTNESS CONFIGURATION

The Control A Brightness Configuration Register has 3 functions:

1. Selects how the LED current sink which is mapped to Control Bank A is controlled (either directly through the I²C or via the

ALS interface)

2. Programs the LED current mapping mode for Control Bank A (Linear or Exponential)

3. Programs which Control A Zone Target Register is the Brightness Register for Bank A in I²C Current Control

TABLE 9. Control A Brightness Configuration Register Description (Address 0x16)

Bits [7:5]

Not Used

Bits [4:2]

Control A Brightness Pointer (I²C

Bit 1

Bit 0

LED Current Mapping Mode

Bank A Current Control

Current Control Only)

N/A

000 = Control A Zone Target 0

001 = Control A Zone Target 1

010 = Control A Zone Target 2

011 = Control A Zone Target 3

1XX = Control A Zone Target 4

(default)

0 = Exponential Mapping

(default)

1 = Linear Mapping

0 = ALS Current Control

1 = I²C Current Control (default)

CONTROL B BRIGHTNESS CONFIGURATION

The Control B Brightness Configuration Register has 3 functions:

1. Selects how the LED current sink which is mapped to Control Bank B is controlled (either directly through the I²C or via the

ALS interface)

2. Programs the LED current mapping mode for Control Bank B (Linear or Exponential)

3. Programs which Control B Zone Target Register is the Brightness Register for Bank B in I²C Current Control

TABLE 10. Control B Brightness Configuration Register Description (Address 0x18)

Bits [7:5]

Not Used

Bits [4:2]

Control A Brightness Pointer (I²C

Bit 1

Bit 0

LED Current Mapping Mode

Bank B Current Control

Current Control Only)

N/A

000 = Control B Zone Target 0

001 = Control B Zone Target 1

010 = Control B Zone Target 2

011 = Control B Zone Target 3

1XX = Control B Zone Target 4

(default)

0 = Exponential Mapping

(default)

1 = Linear Mapping

0 = ALS Current Control

1 = I²C Current Control (default)

CONTROL C BRIGHTNESS CONFIGURATION

The Control C Brightness Configuration Register has 3 functions:

1. Selects how the LED current sink which is mapped to Control Bank C is controlled (either directly through the I²C or via the

ALS interface)

2. Programs the LED current mapping mode for Control Bank C (Linear or Exponential)

3. Programs which Control C Zone Target Register is the Brightness Register for Bank C in I²C Current Control

TABLE 11. Control C Brightness Configuration Register Description (Address 0x1A)

Bits [7:5]

Not Used

Bits [4:2]

Control C Brightness Pointer (I²C

Bit 1

Bit 0

LED Current Mapping Mode

Bank C Current Control

Current Control Only)

N/A

000 = Control C Zone Target 0

001 = Control C Zone Target 1

010 = Control C Zone Target 2

011 = Control C Zone Target 3

1XX = Control C Zone Target 4

(default)

0 = Exponential Mapping

(default)

1 = Linear Mapping

0 = ALS Current Control

1 = I²C Current Control (default)

29

LM3532

CONTROL A/B/C FULL-SCALE CURRENT

These registers program the full-scale current setting for the current sink(s) assigned to Control Bank A/B/C. Each Control Bank

has its own full-scale current setting (Control Bank A, Address 0x17), (Control Bank B, address 0x19), (Control Bank C, address

0x1B).

TABLE 12. Control A/B/C Full-Scale Current Registers Descriptions (Address 0x17, 0x19, 0x1B)

Bits [7:5]

Not Used

Bits [4:0]

Control A/B/C Full-Scale Current Select Bits

00000 = 5 mA

00001 = 5.8 mA

00010 = 6.6 mA

00011 = 7.4 mA

00100 = 8.2 mA

00101 = 9 mA

00110 = 9.8 mA

00111 = 10.6 mA

01000 = 11.4 mA

01001 = 12.2 mA

01010 = 13 mA

01011 = 13.8 mA

01100 = 14.6 mA

01101 = 15.4 mA

01110 = 16.2 mA

01111 = 17 mA

10000 = 17.8 mA

10001 = 18.6mA

10010 = 19.4 mA

10011 = 20.2 mA (default)

10100 = 21 mA

10101 = 21.8 mA

10110 = 22.6 mA

10111 = 23.4 ma

11000 = 24.2 mA

11001 = 25 mA

11010 = 25.8 mA

11011 = 26.6 mA

11100 = 27.4 mA

11101 = 28.2 mA

11110 = 29 mA

11111 = 29.8 mA

N/A

30

LM3532

FEEDBACK ENABLE

The Feedback Enable Register configures which current sinks are or are not part of the boost control loop.

TABLE 13. Feedback Enable Register Description (Address 0x1C)

Bits [7:3]

Not Used

Bit 2

Bit 1

Bit 0

ILED3 Feedback Enable

ILED2 Feedback Enable ILED1 Feedback Enable

N/A

0 = ILED3 is not part of the

boost control loop

0 = ILED2 is not part of the 0 = ILED1 is not part of the

boost control loop

1 = ILED3 is part of the boost 1 = ILED2 is part of the

control loop (default)

1 = ILED1 is part of the

boost control loop (default) boost control loop (default)

CONTROL ENABLE

The Control Enable register contains the bits to turn on/off the individual Control Banks (A, B, or C). Once one of these bits is

programmed high, the current sink(s) assigned to the selected control banks are enabled.

TABLE 14. Control Enable Register Description (Address 0x1D)

Bits (7:3)

(Not Used)

Bit 2

Control C Enable

Bit 1

Control B Enable Control A Enable

0 = Control B is 0 = Control A is

disabled (default) disabled (default)

Bit 0

N/A

0 = Control C is

disabled (default)

1 = Control C is

enabled

1 = Control B is

enabled

1 = Control A is

enabled

31

LM3532

ALS1 & 2 RESISTOR SELECT

The ALS Resistor Select Registers program the internal pulldown resistor at the ALS1/ALS2 input. Each ALS input has its own

resistor select register (ALS1 Resistor Select Register, Address 0x20) and (ALS2 Resistor Select Register, Address 0x21). Each

ALS input can be set independent of the other. There are 32 available resistors including a high impedance setting. The full-scale

input voltage range at either ALS input is 2V.

TABLE 15. ALS Resistor Select Register Description (Address 0x20, Address 0x21)

Bit [7:5]

Bit [4:0]

Not Used

ALS1/ALS2 Resistor Select Bits

00000 = High Impedance (default)

00001 = 37 kΩ

00010 = 18.5 kΩ

00011 = 12.33 kΩ

00100 = 9.25 kΩ

00101 = 7.4 kΩ

00110 = 6.17 kΩ

00111 = 5.29 kΩ

01000 = 4.63 kΩ

01001 = 4.11 kΩ

01010 = 3.7 kΩ

01011 = 3.36 kΩ

01100 = 3.08 kΩ

01101 = 2.85 kΩ

01110 = 2.64 kΩ

01111 = 2.44 kΩ

10000 = 2.31 kΩ

10001 = 2.18 kΩ

10010 = 2.06 kΩ

10011 = 1.95 kΩ

10100 = 1.85 kΩ

10101 = 1.76 kΩ

10110 = 1.68 kΩ

10111 = 1.61 kΩ

11000 = 1.54 kΩ

11001 = 1.48 kΩ

11010 = 1.42 kΩ

11011 = 1.37 kΩ

11100 = 1.32 kΩ

11101 = 1.28 kΩ

11110 = 1.23 kΩ

11111 = 1.19 kΩ

N/A

32

LM3532

ALS DOWN DELAY

The ALS Down Delay Register adds additional average time delays for ALS changes in the backlight current during falling ALS

input voltages. Code 00000 adds 3 extra average period delays on top of the 3 default delays (6 total). Code 11111 adds 34 extra

average period delays.

TABLE 16. ALS Down Delay Register Description (Address 0x22)

Bits [7:6]

Not Used

Bit [5]

Bits [4:0]

Down Delay

ALS Fast startup Enable

00000 = 6 total Average Period delay for Down

Delay Control (default)

:

0 = ALS Fast startup is Disabled

1 = ALS Fast startup is Enabled (default)

N/A

11111 = 34 total Average Periods of Delay for

Down Delay Control

ALS CONFIGURATION

The ALS Configuration register controls the ALS average times, the ALS enable bit, and the ALS input select.

TABLE 17. ALS Configuration Register Description (Address 0x23)

Bits [7:6]

Bit [5:4]

Bit 3

Bits [2:0]

ALS Input Select

ALS Control

ALS Enable

ALS Average Time

00 = Average of ALS1 and 00 = Direct ALS Control. ALS

ALS2 is used to determine inputs respond to up and down

0 = ALS is disabled

(default)

000 = 17.92 ms

001 = 35.84 ms

backlight current

transitions (default)

1 = ALS is enabled

010 = 71.68 ms

01 = Only the ALS1 input is 01 = This setting is for a future

used to determine backlight mode.

011 = 143.36 ms

100 = 286.72 ms (default)

101 = 573.44 ms

110 = 1146.88 ms

111 = 2293.76 ms

current (default)

1X = Down Delay Control. Extra

10 = Only the ALS2 input is delays of 3 x t_AVEto 34 x t_AVEare

used to determine the

backlight current

11 = The maximum of ALS1

and ALS2 is used to

determine the backlight

current

added for down transitions, before

the new backlight target is

programmed. (see DOWN

DELAY section).

33

LM3532

ALS ZONE READBACK / INFORMATION

The ALS Zone Readback and ALS Zone Information Readback registers each contain information on the current ambient light

brightness zone. The ALS Zone Readback register contains the ALS Zone after the averager and discriminator block and reflects

both up and down changes in the ambient light brightness zone. The ALS Zone Information register reflects the contents of either

the ALS Zone Readback register (with up and down transition). This register also includes a Zone Change bit (bit 3) which is written

with a 1 each time the ALS zone changes. This bit is cleared upon read back of the ALS Zone Information register.

TABLE 18. ALS Zone Information Register Description (Address 0x24)

Bits [7:4]

Not Used

Bit 3

Zone Change Bit

Bits [2:0]

Brightness Zone

N/A

0 = No change in ALS Zone (default)

000 = Zone 0 (default)

1 = There was a change in the ALS Zone 001 = Zone 1

since the last read of this register. This bit 010 = Zone 2

is cleared on read back.

011 = Zone 3

1XX = Zone 4

TABLE 19. ALS Zone Readback Register Description (Address 0x25)

Bits [7:3]

Not Used

Bits [2:0]

Brightness Zone

N/A

000 = Zone 0 (default)

001 = Zone 1

010 = Zone 2

011 = Zone 3

1XX = Zone 4

34

LM3532

ALS ZONE BOUNDARIES

There are 4 ALS Zone Boundary registers which form the boundaries for the 5 Ambient Light Zones. Each Zone Boundary register

is 8 bits with a maximum voltage of 2V. This gives a step size for each Zone Boundary Register bit of:

ALS Zone Boundary 0 High (Address 0x60), default = 0x35 (415.7 mV)

ALS Zone Boundary 0 Low (Address 0x61), default = 0x33 (400 mV)

ALS Zone Boundary 1 High (Address 0x62), default = 0x6A (831.4 mV)

ALS Zone Boundary 1 Low (Address 0x63), default = 0x66 (800 mV)

ALS Zone Boundary 2 High (Address 0x64), default = 0xA1 (1262.7 mV)

ALS Zone Boundary 2 Low (Address 0x65), default = 0x99 (1200 mV)

ALS Zone Boundary 3 High (Address 0x66), default = 0xDC (1725.5 mV)

ALS Zone Boundary 3 Low (Address 0x67), default = 0xCC (1600 mV)

(See ALS Zone Boundaries + Hysteresis Figure 6)

ZONE TARGET REGISTERS

There are 3 groups of Zone Target Registers (Control A, Control B, and Control C). The Zone Target registers have 2 functions.

In Ambient Light Current control, they map directly to the corresponding ALS Zone. When the active ALS input lands within the

programmed Zone, the backlight current is programmed to the corresponding zone target registers set point (see below).

Control A Zone Target Register 0 maps directly to Zone 0 (Address 0x70)

Control A Zone Target Register 1 maps directly to Zone 1 (Address 0x71)

Control A Zone Target Register 2 maps directly to Zone 2 (Address 0x72)

Control A Zone Target Register 3 maps directly to Zone 3 (Address 0x73)

Control A Zone Target Register 4 maps directly to Zone 4 (Address 0x74)

Control B Zone Target Register 0 maps directly to Zone 0 (Address 0x75)

Control B Zone Target Register 1 maps directly to Zone 1 (Address 0x76)

Control B Zone Target Register 2 maps directly to Zone 2 (Address 0x77)

Control B Zone Target Register 3 maps directly to Zone 3 (Address 0x78)

Control B Zone Target Register 4 maps directly to Zone 4 (Address 0x79)

Control C Zone Target Register 0 maps directly to Zone 0 (Address 0x7A)

Control C Zone Target Register 1 maps directly to Zone 1 (Address 0x7B)

Control C Zone Target Register 2 maps directly to Zone 2 (Address 0x7C)

Control C Zone Target Register 3 maps directly to Zone 3 (Address 0x7D)

Control C Zone Target Register 4 maps directly to Zone 4 (Address 0x7E)

(See Ambient Light Input to Backlight Mapping, Figure 5)

In I²C Current Control, any of the 5 Zone Target Registers for the particular Control Bank can be the LED brightness registers. This

is set according to Control A, B, or C Brightness Configuration Registers (Bits [4:2]).

35

LM3532

Applications Information

INDUCTOR SELECTION

The LM3532 is designed to work with a 10 µH to 22 µH inductor. When selecting the inductor, ensure that the saturation rating is

high enough to accommodate the applications peak inductor current . The inductance value must also be large enough so that the

peak inductor current is kept below the LM3532's switch current limit. See the MAXIMUM OUTPUT POWER Section for more

details. Table 20 lists various inductors that can be used with the LM3532. The inductors with higher saturation currents are more

suitable for applications with higher output currents or voltages (multiple strings). The smaller devices are geared toward single

string applications with lower series LED counts.

TABLE 20. Inductors

Manufacturer

TDK

Part Number

Value

10 µH

Size

Current

Rating

DC Resistance

0.712Ω

0.47Ω

VLS252010T-100M

VLS2012ET-100M

VLF301512MT-100M

VLF4010ST-100MR80

VLS252012T-100M

VLF3014ST-100MR82

VLF4014ST-100M1R0

XPL2010-103ML

2.5 mm × 2

mm × 1 mm

590 mA

695 mA

690 mA

800 mA

810 mA

820 mA

1000 mA

610 mA

550 mA

TDK

2 mm × 2 mm

× 1.2 mm

TDK

3.0 mm × 2.5

mm × 1.2mm

0.25Ω

TDK

2.8 mm × 3

mm × 1 mm

0.25Ω

TDK

2.5 mm × 2

mm × 1.2mm

0.63Ω

TDK

2.8 mm × 3

mm × 1.4mm

0.25Ω

TDK

3.8 mm × 3.6

mm × 1.4 mm

0.22Ω

Coilcraft

1.9 mm × 2

mm × 1 mm

0.56Ω

LPS3010-103ML

2.95 mm ×

2.95 mm × 0.9

mm

0.54Ω

Coilcraft

LPS4012-103ML

10 µH

3.9mm ×

1.1mm

1000 mA

0.35Ω

Coilcraft

LPS4012-223ML

LPS4018-103ML

LPS4018-223ML

22 µH

10 µH

22 µH

3.9 mm × 3.9

mm × 1.1 mm

780 mA

1100 mA

700 mA

0.6Ω

0.2Ω

3.9 mm × 3.9

mm × 1.7 mm

3.9 mm × 3.9

mm × 1.7 mm

0.36Ω

CAPACITOR SELECTION

The LM3532’s output capacitor has two functions: filtering of the boost converter's switching ripple, and to ensure feedback loop

stability. As a filter, the output capacitor supplies the LED current during the boost converter's on time and absorbs the inductor's

energy during the switch's 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 capacitor must be sized large enough to filter the inductor current ripple that could cause

the output voltage ripple to become excessive. As a feedback loop component, the output capacitor must be at least 1µF and have

low ESR; otherwise, the LM3532's boost converter can become unstable. This requires the use of ceramic output capacitors. Table

21 lists part numbers and voltage ratings for different output capacitors that can be used with the LM3532.

TABLE 21. Input/Output Capacitors

Manufacturer

Murata

Part Number

Value

1 µF

Size

0805

0603

Rating

50V

Description

COUT

CIN

GRM21BR71H105KA12

GRM188B31A225KE33

C1608X5R0J225

Murata

2.2 µF

10V

TDK

6.3V

CIN

36

LM3532

DIODE SELECTION

The diode connected between SW and OUT must be a Schottky diode and have a reverse breakdown voltage high enough to

handle the maximum output voltage in the application. Table 22 lists various diodes that can be used with the LM3532.

TABLE 22. Diodes

Manufacturer

Diodes Inc.

Part Number

B0540WS

Value

Size

Rating

Schottky

SOD-323

40V/500 mA

40V/200 mA

SDM20U40

SOD-523 (1.2 mm × 0.8

mm × 0.6 mm)

On Semiconductor

NSR0340V2T1G

NSR0240V2T1G

Schottky

SOD-523 (1.2 mm × 0.8

mm × 0.6 mm)

40V/250 mA

SOD-523 (1.2 mm × 0.8

mm × 0.6 mm)

LAYOUT GUIDELINES

The LM3532 contains an inductive boost converter which sees a high switched voltage (up to 40V) at the SW pin, and a step current

(up to 1A) 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 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 16 highlights

these two noise generating components.

37

LM3532

301154101

FIGURE 16. LM3532's Boost Converter Showing Pulsed Voltage at SW (High dV/dt) and

Current Through Schottky and COUT (High dI/dt)

38

LM3532

The following lists the main (layout sensitive) areas of the LM3532 in order of decreasing importance:

Output Capacitor

•

Schottky Cathode to COUT+

COUT− 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

Output Capacitor Placement

The output capacitor is in the path of the inductor current discharge current. 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. Typical turn-off/turn-on times are around 5ns. Any inductance

along this series path from the cathode of the diode through C_OUTand back into the LM3532's GND pin will contribute to voltage

spikes (V_SPIKE= L_PX× 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 LM3532's GND bump. The best placement for C_OUTis on the same layer as the LM3532 so as to avoid any vias

that will add extra series inductance (see Layout Examples).

Schottky Diode Placement

The Schottky diode is in the path of the inductor current discharge. 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_PX× dI/dt) at SW and OUT which can potentially over-voltage the SW pin, or feed through to VOUT and through the

output capacitor and into GND. Connecting the anode of the diode as close as possible to the SW pin and the cathode of the diode

as close as possible to COUT+ will reduce the inductance (L_PX) and minimize these voltage spikes (Layout Examples).

Inductor Placement

The node where the inductor connects to the LM3532’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 (input 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.

To reduce the capacitively coupled signal from SW into nearby traces, the SW bump to inductor connection must be minimized in

area. This limits the PCB capacitance from SW to other traces. Additionally, other nodes need to be routed 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 help isolate SW and dramatically

reduce the capacitance from SW into nearby traces.

To limit the trace resistance of the VBATT to inductor connection and from the inductor to SW connection, use short, wide traces

(see Layout Examples).

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 be a few hundred mA's with 5ns rise and fall times. This will appear as high dI/dt current pulses

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.

Close placement of the input bypass capacitor at the input side of the inductor is also critical. The source impedance (inductance

and resistance) from the input supply, along with the input capacitor of the LM3532, form a series RLC circuit. If the output resistance

from the source (R_S) is low enough the circuit will be underdamped and will have a resonant frequency (typically the case). De-

pending on the size of L_Sthe resonant frequency could occur below, close to, or above the LM3532's switching frequency. This

can cause the supply current ripple to be:

•

approximately equal to the inductor current ripple when the resonant frequency occurs well above the LM3532's switching

frequency;

•

greater then the inductor current ripple when the resonant frequency occurs near the switching frequency; or

less then the inductor current ripple when the resonant frequency occurs well below the switching frequency.

39

LM3532

Figure 17 shows this 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_INsupply is replaced with a short to GND and the LM3532 + Inductor is replaced with a current

source (ΔI_L).

Equation 1 is the criteria for an underdamped response. Equation 2 is the resonant frequency. Equation 3 is the approximated

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

As an example, consider a 3.6V supply with 0.1Ω of series resistance connected to C_INthrough 50 nH of connecting traces. This

results in an underdamped input filter circuit with a resonant frequency of 712 kHz. Since the switching frequency lies near to the

resonant frequency of the input RLC network, the supply current is probably larger then the inductor current ripple. In this case,

using equation 3 from Figure 17, the supply current ripple can be approximated as 1.68 times the inductor current ripple. Increasing

the series inductance (L_S) to 500 nH causes the resonant frequency to move to around 225 kHz and the supply current ripple to

be approximately 0.25 times the inductor current ripple.

301154102

FIGURE 17. Input RLC Network

40

LM3532

Example Layouts

The following figures show example layouts which apply the required (proper) layout guidelines. These figures should be used as

guides for laying out the LM3532's boost circuit.

30115485

FIGURE 18. Layout Example #1

30115486

FIGURE 19. Layout Example #2

41

LM3532

Physical Dimensions inches (millimeters) unless otherwise noted

16-Bump Thin Micro SMD Package

For Ordering, Refer to Ordering Information Table

NS Package Number TMD16

X1 = 1.745 mm (±0.1 mm), X2 = 1.845 mm (±0.1 mm), X3 = 0.600 mm

42

LM3532

Notes

43

Notes

Incorporated


型号：	LM3532
厂家：	TEXAS INSTRUMENTS
描述：	High Efficiency White LED Driver with Programmable Ambient Light Sensing Capability and I2C-Compatible Interface 高效率白光LED驱动器，具有可编程环境光感应功能和I2C兼容接口驱动器
文件：	总45页 (文件大小：1627K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LM3532 [TI]

相关型号：

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

LM3533TMX-40/NOPB