LM3532TME-40A/NOPB_技术文档

LM3532

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SNVS653D –JULY 2011–REVISED JUNE 2013

LM3532 High Efficiency White LED Driver with Programmable Ambient Light Sensing

Capability and I²C-Compatible Interface

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1

FEATURES

APPLICATIONS

2

•

Drives up to 3 Parallel High-Voltage LED

Strings at 40V Each with up to 90% Efficiency

•

Power Source for White LED Backlit LCD

Displays

•

0.4% Typical Current Matching Between

Strings

•

Programmable Keypad Backlight

DESCRIPTION

The LM3532 is

256 Level Logarithmic and Linear Brightness

Control with 14-Bit Equivalent Dimming

I²C-compatible Interface

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 allowing for a wide variety of

backlight + keypad applications.

•

Direct Read Back of Ambient Light Sensor via

8-bit ADC

•

Programmable Dual Ambient Light Sensor

Inputs with Internal Sensor Gain Selection

Dual External PWM Inputs for LED Brightness

Adjustment

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.

•

Independent Current String Brightness Control

Programmable LED Current Ramp Rates

40V Over-Voltage Protection

1A Typical Current Limit

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

thin DSBGA (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.

Typical Application Circuit

L

D1

VOUT up to 40V

V_IN

CIN

COUT

IN

SW

OVP

V_ALS

Ambient Light

Sensor 2

Ambient Light

Sensor 1

ALS1

ALS2

V_IN

LM3532

SDA

SCL

ILED1

ILED2

ILED3

PWM1

HWEN

INT

PWM2

T0

PGND

1

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

All trademarks are the property of their respective owners.

2

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.

LM3532

SNVS653D –JULY 2011–REVISED JUNE 2013

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Application Circuit Component List

Current/Voltage

Rating (Resistance)

Component

Manufacturer's Part Number

Value

Size (mm)

White LED

Driver

LM3532

1.745 mm x 1.845 mm x 0.6 mm

L

COILCRAFT

LPS4018-103ML

10 µH

1µF

3.9 mm x 3.9 mm x 1.7 mm

1A (R_DC= 0.2Ω)

COUT

CIN

Murata

GRM21BR71H105KA12L

0805

0603

50V

10V

Murata

2.2 µF

GRM188R71A225KE15D

Connection Diagram

Top View

A1

B1

A2

B2

A3

A4

B4

B3

C2

D2

C3

D3

C4

D4

C1

D1

Figure 1. 16-Bump (1.745 mm × 1.845 mm × 0.6 mm)

DSBGA Package YFQ0016

PIN DESCRIPTIONS

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

2

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SNVS653D –JULY 2011–REVISED JUNE 2013

This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with

appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.

ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more

susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.

(1)(2)(3)

ABSOLUTE MAXIMUM RATINGS

V_INto GND

−0.3V to +6V

−0.3V to +45V

−0.3V to +6V

Internally Limited

+150°C

V_SW, V_OVP, V_ILED1, V_ILED2, V_ILED3to GND

V_SCL, V_SDA, V_ALS1, V_ALS2, V_PWM1, V_PWM2, V_INT, V_HWEN, V_T0to GND

Continuous Power Dissipation

Junction Temperature (T_J-MAX

Storage Temperature Range

)

−65°C to +150°C

+300°C

(4)

Maximum Lead Temperature (Soldering, 10s)

ESD Rating

Human Body Model

(5)

2.0 kV

(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 verified. For verified specifications and test

conditions, see the Electrical Characteristics table.

(2) All voltages are with respect to the potential at the GND pin.

(3) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and

specifications

(4) For detailed soldering specifications and information, please refer to Application Note AN-1112: DSBGA Wafer Level Chip Scale

Package (SNVA009).

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

(1)(2)

OPERATING RATINGS

V_INto GND

2.7V to 5.5V

0 to +40V

V_SW, V_OVP, V_ILED1, V_ILED2, V_ILED3to GND

Junction Temperature Range (T_J)^{(3) (4)}

−40°C to +125°C

(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 verified. For verified specifications and test

conditions, see the Electrical Characteristics table.

(2) All voltages are with respect to the potential at the GND pin.

(3) 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.).

(4) 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).

THERMAL PROPERTIES

Thermal Resistance Junction to Ambient (T_JA

(1)

)

61.3°C/W

(1) 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

DSBGA 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.

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(1)(2)

ELECTRICAL CHARACTERISTICS

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

Parameter

Conditions

Min

Typ

Max

Units

2.7V ≤ V_IN≤ 5.5V, ControlX Full-Scale

Current Register = 0xF3, Brightness

Code = 0xFF

Output Current Regulation Accuracy

(ILED1, ILED2 or ILED3)

I_LED(1/2/3)

18.68

20.2

21.8

mA

2.7V ≤ V_IN≤ 5.5V, I_{FULL_SCALE}

20.2mA, Brightness Code = 0xFF

=

(3) (4)

I_MATCH

V_{REG_CS}

V_HR

,

ILED2 to ILED3 Current Matching

−2

0.3

400

200

2

%

Regulated Current Sink Headroom

Voltage

mV

Current Sink Minimum Headroom

Voltage

I_LED= 95% of nominal, I_LED= 20.2

mA

240

R_DSON

I_CL

NMOS Switch On Resistance

NMOS Switch Current Limit

I_SW= 100 mA

0.25

1000

41

Ω

2.7V ≤ V_IN≤ 5.5V

ON Threshold, 2.7V ≤ V_IN≤ 5.5V

Hysteresis

880

40

1120

42

mA

V_OVP

Output Over-Voltage Protection

V

1

f_SW

Switching Frequency

Maximum Duty Cycle

Minimum Duty Cycle

2.7V ≤ V_IN≤ 5.5V

450

500

94

550

kHz

%

D_MAX

D_MIN

10

%

Quiescent Current into IN, Device

Not Switching

ILED1 = ILED2 = ILED3 = 20.2 mA,

feedback disabled.

I_Q

490

µA

I_LED1= I_LED2= I_LED3= 20.2 mA, V_OUT

= 32V

I_{Q_SW}

I_SHDN

I_{LED_MIN}

Switching Supply Current

Shutdown Current

1.35

1

mA

µA

2.7V ≤ V_IN≤ 5.5V, HWEN = GND

2

Full-Scale Current =20.2 mA

Brightness code = 0x01, Mapping =

Exponential

Minimum LED Current in ILED1,

ILED2 or ILED3

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

2.7V ≤ V_IN≤ 5.5V

0

0.4

V_IN

0.4

V

V_IH

V_OL

Input Logic High

2.7V ≤ V_IN≤ 5.5V

1.2

Output Logic Low (SCL, INT)

2.7V ≤ V_IN≤ 5.5V, I_LOAD= 3mA

V

PWM Input Internal Pulldown

Resistance (PWM1, PWM2)

R_PWM

100

kΩ

I²C-COMPATIBLE TIMING SPECIFICATIONS (SCL, SDA, )⁽⁵⁾

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

4

t

SDA High Hold Time After SCL High

(Stop)

t₅

AMBIENT LIGHT SENSOR INPUTS (ALS1, ALS2)

ALS1, ALS2 Resistor Select Register

R_ALS1, R_ALS2

ALS Pin Internal Pulldown Resistors = 0x0F,

2.29

2.44

2.59

kΩ

2.7V ≤ V_IN≤ 5.5V

(1) All voltages are with respect to the potential at the GND pin.

(2) Min and Max limits are verified by design, test, or statistical analysis. Typical numbers are not verified, but do represent the most likely

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

(3) All Current sinks for the matching spec are assigned to the same Control Bank.

(4) 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.

(5) SCL and SDA must be glitch-free in order for proper brightness control to be realized.

4

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ELECTRICAL CHARACTERISTICS ⁽¹⁾⁽²⁾(continued)

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

Parameter

Conditions

Min

Typ

Max

Units

Ambient Light Sensor Reference

Voltage

V_{ALS_REF}

2.7V ≤ V_IN≤ 5.5V

1.94

2

2.06

V

ALS Input Offset Voltage

(Code 0 to 1 transition - V_LSB

V_OS

2.7V ≤ V_IN≤ 5.5V

0.8

2.5

4.2

mV

)

t_CONV

LSB

Conversion Time

154

µs

ADC Resolution

7.84

mV

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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)

Efficiency vs V_IN

Single String, ILED = 20.2mA

L = LPS4018-103ML (10µH)

94

92

90

88

86

84

82

80

78

76

74

72

92

90

88

86

84

82

80

78

76

74

3 LEDs

4 LEDs

8 LEDs

10 LEDs

9 LEDs

7 LEDs

5 LEDs

6 LEDs

3.5

2.5

3.0

4.0

4.5

5.0

5.5

2.5

3.0

3.5

4.0

4.5

5.0

5.5

VIN (V)

Figure 2.

Figure 3.

Efficiency vs V_IN

Dual String, ILED = 20.2mA per string

L = LPS4018-103ML (10µH)

Efficiency vs V_IN

Dual String, ILED = 20.2mA per string

L = LPS4018-103ML (10µH)

92

93

91

90

3 LEDs

4 LEDs

89

87

85

83

81

79

77

75

73

71

69

67

65

88

86

84

82

10 LEDs

8 LEDs

9 LEDs

7 LEDs

6 LEDs

80

78

5 LEDs

76

74

2.5

3.0

3.5

4.0

4.5

5.0

5.5

2.5

3.0

3.5

4.0

VIN (V)

4.5

5.0

5.5

VIN (V)

Figure 4.

Figure 5.

Efficiency vs V_IN

Triple String, ILED = 20.2mA per string

L = LPS4018-103ML (10µH)

Efficiency vs V_IN

Triple String, ILED = 20.2mA per string

L = LPS4018-103ML (10µH)

92

94

3 LEDs

90

88

86

84

82

80

78

76

74

72

92

90

4 LEDs

88

86

84

9 LEDs

7 LEDs

82

10 LEDs

80

8 LEDs

6 LEDs

78

5 LEDs

76

74

72

2.5

3.0

3.5

4.0

4.5

5.0

5.5

2.5

3.0

3.5

4.0

4.5

5.0

5.5

VIN (V)

Figure 6.

Figure 7.

6

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TYPICAL PERFORMANCE CHARACTERISTICS (continued)

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 per string

L = LPS4018-223ML (22µH)

Efficiency vs V_IN

Single String, ILED = 20.2mA per string

L = LPS4018-223ML (22µH)

92

90

3 LEDs

4 LEDs

88

86

84

82

88

86

84

8 LEDs

82

9 LEDs

7 LEDs

6 LEDs

10 LEDs

80

78

76

74

5 LEDs

80

78

76

2.5

3.0

3.5

4.0

4.5

5.0

5.5

2.5

3.0

3.5

4.0

4.5

5.0

5.5

VIN (V)

Figure 8.

Figure 9.

Efficiency vs V_IN

Dual String, ILED = 20.2mA per string

L = LPS4018-223ML (22µH)

Efficiency vs V_IN

Dual String, ILED = 20.2mA per string

L = LPS4018-223ML (22µH)

94

92

90

88

86

84

82

80

78

76

74

72

70

68

66

4 LEDs

92

3 LEDs

90

88

9 LEDs

86

8 LEDs

84

10 LEDs

7 LEDs

82

6 LEDs

80

78

76

74

72

5 LEDs

2.5

3.0

3.5

4.0

VIN (V)

4.5

5.0

5.5

2.5

3.0

3.5

4.0

VIN (V)

4.5

5.0

5.5

Figure 10.

Figure 11.

Efficiency vs V_IN

Triple String, ILED = 20.2mA per string

L = LPS4018-223ML (22µH)

Efficiency vs V_IN

Triple String, ILED = 20.2mA per string

L = LPS4018-223ML (22µH)

94

92

90

88

86

84

82

80

78

76

74

72

70

4 LEDs

3 LEDs

90

88

86

84

9 LEDs

7 LEDs

10 LEDs

8 LEDs

82

80

78

76

74

72

5 LEDs

6 LEDs

2.3

2.9

3.6

4.2

4.9

5.5

2.5

3.0

3.5

4.0

4.5

5.0

5.5

VIN (V)

Figure 12.

Figure 13.

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TYPICAL PERFORMANCE CHARACTERISTICS (continued)

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 I_LED

Efficiency vs I_LEDTriple String, VIN = 3.6V

L = LPS4018-103ML (10µH)

Triple String, VIN = 3.6V

L = LPS4018-103ML (10µH)

91

90

89

88

87

86

85

84

83

82

81

80

79

91

90

89

88

87

86

85

84

83

82

81

80

79

3 LEDs

4 LEDs

5 LEDs

6 LEDs

8 LEDs

7 LEDs

9 LEDs

10 LEDs

0

6 12 18 24 30 36 42 48 54 60 66 72 78 84 90

ILED (mA)

0

6 12 18 24 30 36 42 48 54 60 66 72 78 84 90

ILED (mA)

Figure 14.

Figure 15.

Efficiency vs I_LED

Triple String, VIN = 3.6V

L = LPS4018-223ML (22µH)

Efficiency vs I_LED

Triple String, VIN = 3.6V

L = LPS4018-223ML (22µH)

91

90

89

88

87

86

85

84

83

82

81

80

79

3 LEDs

5 LEDs

90

89

88

87

86

85

84

83

82

81

80

79

4 LEDs

6 LEDs

7 LEDs

9 LEDs

8 LEDs

10 LEDs

0

9

18 27 36 45 54 63 72 81 90

ILED (mA)

0

9

18 27 36 45 54 63 72 81 90

ILED (mA)

Figure 16.

Figure 17.

Shutdown Current vs VIN

HWEN = GND

Current Sink Matching vs VIN

ILED2 to ILED3

240.0

220.0

200.0

1.6

1.4

1.2

0.9

0.7

0.5

-40°C

180.0

240.0

85C

220.0

160.0

200.0

180.0

160.0

140.0

120.0

-40C

25C

120.0

100.0

80.0

60.0

100.0

40.0

20.0

80.0

25°C

85°C

60.0

40.0

20.0

0.0

2.5

3.1

3.7

4.3

4.9

5.5

2.5

3.1

3.7

4.3

4.9

5.5

VIN (V)

Figure 18.

Figure 19.

8

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TYPICAL PERFORMANCE CHARACTERISTICS (continued)

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.

Current Sink Matching vs VIN

ILED1 to ILED2 to ILED3

ALS Resistance vs VIN

R_ALS1, (2.44kΩ setting)

(ΔILED is worst case difference between all three strings)

500

450

400

350

300

250

200

150

100

50

TA = -40°C

TA = +85°C

2.450k

2.448k

2.446k

2.444k

2.442k

2.440k

2.438k

2.436k

85°C

25°C

TA = +25°C

-40°C

2.5

3.0

3.5

4.0

4.5

5.0

5.5

2.5

3.1

3.7

4.3

4.9

5.5

VIN (V)

Figure 20.

Figure 21.

ALS Resistor Matching vs VIN

Integral Non Linearity vs Code

(Endpoint Method)

(2.44kΩ setting)

10.000

8.000

1.00

0.75

0.50

0.25

0.00

-0.25

-0.50

-0.75

-1.00

6.000

4.000

85°C

25°C

2.000

0.000

-2.000

-4.000

-6.000

-8.000

-10.000

-40°C

2.5

3.0

3.5

4.0

4.5

5.0

5.5

0

32 64 96 128 160 192 224 256

Code (D)

VIN (V)

Figure 22.

Figure 23.

Differential Non Linearity vs Code

Peak to Peak LED Current Ripple vs f_PWM

1.00

0.90

0.80

0.70

0.60

0.50

0.40

0.30

0.20

0.10

0.00

-0.10

22.0

20.0

18.0

16.0

14.0

12.0

10.0

8.0

6.0

4.0

2.0

0.0

0.01

0

32 64 96 128 160 192 224 256

Code (D)

0.1

1

10

100

fPWM (kHz)

Figure 24.

Figure 25.

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TYPICAL PERFORMANCE CHARACTERISTICS (continued)

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.

LED Current vs Headroom Voltage

31

30

29

-40°C

28

27

26

25

24

23

22

21

20

19

25°C

85°C

0.10 0.15 0.20 0.25 0.30 0.35 0.40

VHR (V)

Figure 26.

10

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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 27). 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).

V

IN

SW

C

OUT

OVP

Error Amplifier

400 mV

IN

+

-

Boost

Controller

C

250 mW

IN

ILED1

ILED2

ILED3

V

HR

Min

Feedback

Enable

GND

Figure 27. 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 28). 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.

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Environmental

Stimulus

Controls

(Masters: Output configuration)

(Ramp rates, brightness management)

(ALS processor select, enable)

Outputs

(Slaves)

ALS

Processor

ALS1

ALS2

ALSP_1

Bank_A

Bank_B

Bank_C

ILED1

ILED2

ILED3

PWM

Filters

CABC1

PWM_0

PWM_1

CABC2

Figure 28. LM3532 Functional Control Diagram

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

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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:

1

’ÿ

+

»

≈

Code

I_LED= I_{LED_ FULLSCALE}x 0.85^…^40-

x D_PWM

∆

«

÷

Ÿ

6.4

◊

⁄

(1)

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 29) shows the typical

response of % full-scale current setting vs 8-bit brightness code.

100

10

1

0.1

0

16 32 48 64 80 96 112 128 144 160 176 192 208 224 240 256

BRIGHTNESS CODE (D)

Figure 29. Exponential Mapping Response

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Linear Current Mapping

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

1

255

I_LED= I_{LED_FULLSCALE}

x

x Code x D_PWM

(2)

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 30) shows the typical

response of % full-scale current setting vs 8-bit brightness code.

100

90

80

70

60

50

40

30

20

10

0

16 32 48 64 80 96 112 128 144 160 176 192 208 224 240 256

BRIGHTNESS CODE (D)

Figure 30. 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 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.

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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

Assignment

Brightness Register

PWM Select

PWM Enable

Current Sink Enable

Output Configuration

Register

Control A Brightness

Configuration Register Register Bit[0]

Control A PWM

Control A PWM Register

Bit[2] is PWM enable when Control Register Bit [0]

Control Enable

Bits[1:0] = 00, assigns

Bits [4:2]

0 selects PWM1

1 selects PWM2

A Zone Target 0 is configured as

the brightness register

Bit[3] is PWM enable when Control

A Zone Target 1 is configured as

the brightness register

0 = Bank A Disabled

1 = Bank A Enabled

ILED1 to Control Bank A 000 selects Control A

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

010 selects Control A

Zone Target 2

Bit[4] is PWM enable when Control

A Zone Target 2 is configured as

the brightness register

Bit[5] is PWM enable when Control

A Zone Target 3 is configured as

the brightness register

Bit[6] is PWM enable when Control

A Zone Target 4 is configured as

the brightness register

brightness register

011 selects Control A

Zone Target 3

brightness register

1XX selects Control A

Zone Target 4

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:

2V

ì Code

R_{ALS_}

=

54 mA

(3)

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 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 31 describes the ambient light to brightness mapping.

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Full

Scale

V

= 2V

Zone

ALS_REF

Zone 4

Boundary 3_

Zone 3

Zone

Boundary 2_

Zone

Boundary 1_

Zone 2

Zone

Boundary 0_

Zone 1

Zone 0

Zone

Target 0 Target 1

Zone

Target 2

Zone

Target 4

Zone

Target 3

Ambient Light (lux)

LED Driver Input Code (0x00 - 0xFF)

Figure 31. 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 oscillating between zones when the ALS voltage is close to a Zone

Boundary Threshold. Figure 32 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.

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Zone 4

Zone 3

Zone 2

Zone 4

Zone Boundary 3 High

Zone Boundary 3 Low

Zone 3

Zone Boundary 2 High

Zone Boundary 2 Low

Zone 2

Zone Boundary 1 High

Zone Boundary 1 Low

Zone 1

Zone Boundary 0 High

Zone Boundary 0 Low

Zone 0

Figure 32. 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 33 shows a functional block diagram of the LM3532's ambient light sensor interface.

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Read Back UP

Only Register

ADC Average

Register

ADC Register

Up Only Control

(Up Delay = 3 x t

)

Read Back

Brightness Zone

Register

AVE

Read Back

Ambient Light

Zone Register

ALS1

Direct ALS Control

(Up and Down Delay

Averager

Output

ADC

(7.142ksps)

ALS Brightness

Control Target

Averager

= 3 x t

AVE

)

ALS2

Down Delay Control

(Down Delay =

ALS Input Select

(ALS Configuration

Register Bits[7:6])

ALS Average Time

(ALS Configuration

Register Bits [2:0])

4 x t

to 35 x t

)

AVE

ALS Configuration

Register Bits [5:4]

Up Delay = 3 x t

AVE

Figure 33. ALS Functional Block Diagram

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 34. 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.

t

AVERAGE

(set via bits [2:0] of the ALS

Configuration Register)

t

= 140 ms

CONV

Con-

version version version

version version

I2C Write

ALS Enabled

1

2

3

n

n + 1

V

ALS

(active input is sampled)

ADC Register

(Read Only, Updated every t

Sample Sample Sample

Sample

n

1

2

3

)

CONV

Average Period #2

Average Period #1

0x00

ADC Average Register

(Read Only, Updated every t

Sample 1 + Sample 2 + Sample 3 + … Sample n

=

)

n

AVERAGE

Figure 34. ADC Timing

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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 35).

ALS Start-Up Fast

Normal ALS

Average Period

(1.1 ms)

ALS Enable

I2C

V

ALS_Y

V

ALS_X

Zone 0 Zone 0 Zone 0

Zone 0

Zone Y

Zone X

ALS Zone

Zone Target y

Zone Target x

Run Time

Ramp Rate

I

LED_

Start-Up

Ramp Rate

Figure 35. ALS Startup Sequence

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ALS 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 33) 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 36 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.

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.

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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.

Enable ALS

Average

Period #

1

2

3

4

5

6

7

8

9

12

13

10

11

2V

Zone 4

Zone 3

Zone 2

Zone 1

Zone 0

V_{ALS_}

4

3

2

1

2

3

4

Current Average Zone

Averager Ouput

0

4

3

2

1

2

3

4

*Note:it takes a full

average period to

generate an averager

output value

Zone 4 Brightness Target

LED Current Run Time

Ramp Down

Zone 3 Brightness Target

I_LED

LED Current Run

Time Ramp Up

Zone 2 Brightness Target

Zone 1 Brightness Target

ALS Fast Start-Up

Figure 36. Direct ALS Control

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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 37, 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.

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Enable ALS

Average

Period #

1

2

3

4

5

6

7

8

9

12

13 14

15 16 17

18 19 20

21

22

25

26

10 11

23 24

2V

Zone 4

Zone 3

Zone 2

Zone 1

Zone 0

V_{ALS_}

Current Average

Zone

0

3

2

4

2

4

2

Averager Ouput

4

2

0

3

2

4

2

*Note:it takes a

full average

period to

generate an

averager

output value

Zone 4 Brightness Target

Zone 3 Brightness Target

I_LED

Zone 2 Brightness Target

ALS Fast

Start-Up

Figure 37. 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.

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Protection Features

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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 maximum 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:

efficiency

VIN x

IOUT x VOUT

VIN

x 1 -

+

IPEAK =

VIN x efficiency

2 x fsw x L

VOUT

(4)

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

2 x

IOUT

x

VOUT - VIN x efficiency

IPEAK =

fsw x L x

efficiency

(5)

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.

efficiency

VIN x

IOUT x VOUT

VIN

1 -

x

>

VIN x efficiency fsw x L

VOUT

(6)

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

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

take Equation 4 and Equation 5 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.

0.1

0.095

0.09

44

42

40

38

36

34

32

30

28

26

24

22

20

0.085

0.08

0.075

0.07

0.065

0.06

0.055

0.05

VOUT = 22V

VOUT = 24V

VOUT = 26V

VOUT = 30V

VOUT = 34V

VOUT = 38V

IOUT = 45 mA

IOUT = 50 mA

IOUT = 60 mA

IOUT = 70 mA

IOUT = 80 mA

0.045

0.04

2.5 2.8 3.1 3.4 3.7

4

4.3 4.6 4.9 5.2 5.5

2.5 2.8 3.1 3.4 3.7

4

4.3 4.6 4.9 5.2 5.5

VIN (V)

Figure 38. Maximum Output Power (22 µH)

Figure 39. Maximum Output Power (22 µH)

44

42

40

38

36

34

32

30

28

26

0.1

VOUT = 22V

VOUT = 24V

VOUT = 26V

VOUT = 30V

VOUT = 34V

VOUT = 38V

0.095

0.09

0.085

0.08

0.075

0.07

0.065

0.06

0.055

0.05

24

IOUT = 40 mA

IOUT = 50 mA

22

0.045

0.04

IOUT = 60 mA

IOUT = 70 mA

20

IOUT = 80 mA

IOUT = 45 mA

18

0.035

16

0.03

2.5 2.8 3.1 3.4 3.7

4

4.3 4.6 4.9 5.2 5.5

2.5 2.75

3

3.25 3.5 3.75

4 4.25 4.5 4.75 5 5.25 5.5

VIN (V)

Figure 40. Maximum Output Power (10 µH)

Figure 41. 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.

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I²C-Compatible Interface

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START AND STOP Conditions

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.

t

1

SCL

t

5

4

SDIO

Data In

t

2

SDIO

Data Out

t

3

Figure 42. 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.

I2C Compatible Address

MSB

LSB

0

Bit 2

0

Bit 7

1

Bit 6

1

Bit 5

0

Bit 3

0

Bit 1

R/W

Bit 0

1

Bit 4

Figure 43. 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.

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LM3532 Register Descriptions

Table 2. LM3532 Register Descriptions

Name

I²C Address

Address

Power On Reset

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

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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 A 00 = ILED2 is controlled by Control A

00 = ILED1 is controlled by Control A

PWM and Control A Brightness

Registers

PWM and Control A Brightness Registers PWM and Control A Brightness

01 = ILED2 is controlled by Control B Registers (default)

01 = ILED3 is controlled by Control B PWM and Control B Brightness Registers 01 = ILED1 is controlled by Control B

PWM and Control B Brightness

Registers

(default)

PWM and Control B Brightness

Registers

1X = ILED2 is controlled by Control C

1X = ILED3 is controlled by Control C PWM and Control C Brightness Registers 1X = ILED1 is controlled by Control C

PWM and Control C Brightness

Registers (default)

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 Equation 5.

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)

001 = 1.024 ms/step (261 ms)

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

001 = 1.024 ms/step (261ms)

010 = 2.048 ms/step (522 ms)

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)

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

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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

Zone 4 PWM

Enable

Bit 5

Zone 3 PWM

Enable

Bit 2

Zone 0 PWM

Enable

Bit 1

PWM Input

Polarity

Bit 0

PWM Select

Zone 2 PWM Zone 1 PWM

Enable

0 = Active PWM 0 = Active PWM

0 = Active

0 = Active PWM 0 = Active PWM 0 = active low 0 = PWM1 input

input is disabled input is disabled in PWM input is

input is disabled input is disabled polarity

is mapped to

Control Bank A

(default)

in Zone 4

Zone 3 (default)

disabled in

Zone 2

in Zone 1

in Zone 0

(default)

Not Used

1 = Active PWM 1 = Active PWM

1 = Active

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

input is enabled input is enabled in PWM input is

input is enabled input is enabled polarity

in Zone 1 in Zone 0 (default)

mapped to

Control Bank A

in Zone 4

Zone 3

enabled in

Zone 2

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

Zone 2 PWM

Enable

Bit 2

Zone 1 PWM

Enable

Bit 2

Zone 0 PWM

Enable

Bit 1

PWM Input

Polarity

Bit 0

PWM Select

0 = Active PWM 0 = Active PWM

input is disabled input is disabled

0 = Active

PWM input is

disabled in

Zone 2

0 = Active PWM 0 = Active PWM 0 = active low 0 = PWM1

input is disabled input is disabled polarity

input is

in Zone 4

in Zone 3

in Zone 1

(default)

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 PWM 1 = active high 1 = PWM2 is

input is enabled input is enabled in PWM input is

input is enabled input is enabled polarity

in Zone 1 in Zone 0 (default)

mapped to

Control Bank B

in Zone 4

Zone 3

enabled in

Zone 2

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

Zone 2 PWM

Enable

Bit 2

Zone 1 PWM

Enable

Bit 2

Zone 0 PWM

Enable

Bit 1

PWM Input

Polarity

Bit 0

PWM Select

0 = Active PWM 0 = Active PWM

input is disabled input is disabled

0 = Active

PWM input is

disabled in

Zone 2

0 = Active PWM 0 = Active PWM 0 = active low 0 = PWM1

input is disabled input is disabled polarity

input is

in Zone 4

in Zone 3

in Zone 1

(default)

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 PWM 1 = active high 1 = PWM2 is

input is enabled input is enabled in PWM input is

input is enabled input is enabled polarity

in Zone 1 in Zone 0 (default)

mapped to

Control Bank C

in Zone 4

Zone 3

enabled in

Zone 2

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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]

Bit 1

Bit 0

Control A Brightness Pointer (I²C

Current Control Only)

LED Current Mapping Mode

Bank A Current Control

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]

Bit 1

Bit 0

Control A Brightness Pointer (I²C

Current Control Only)

LED Current Mapping Mode

Bank B Current Control

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]

Bit 1

Bit 0

Control C Brightness Pointer (I²C

Current Control Only)

LED Current Mapping Mode

Bank C Current Control

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)

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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

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

boost control loop

0 = ILED1 is not part of the

boost control loop

1 = ILED3 is part of the boost

control loop (default)

1 = ILED2 is part of the

boost control loop (default)

1 = ILED1 is part of the

boost control loop (default)

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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)

Bit 2

Bit 1

Bit 0

(Not Used)

Control C Enable

Control B Enable

Control A Enable

N/A

0 = Control C is

disabled (default)

1 = Control C is

enabled

0 = Control B is

disabled (default)

1 = Control B is

enabled

0 = Control A is

disabled (default)

1 = Control A is

enabled

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.

32

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

Bit [7:5]

Not Used

Bit [4:0]

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

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

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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

ALS2 is used to determine

backlight current

00 = Direct ALS Control. ALS inputs 0 = ALS is disabled (default) 000 = 17.92 ms

respond to up and down transitions 1 = ALS is enabled

(default)

001 = 35.84 ms

010 = 71.68 ms

01 = Only the ALS1 input is

used to determine backlight

current (default)

10 = Only the ALS2 input is

used to determine the

backlight current

11 = The maximum of ALS1

and ALS2 is used to

determine the backlight

current

01 = This setting is for a future

mode.

011 = 143.36 ms

100 = 286.72 ms (default)

101 = 573.44 ms

110 = 1146.88 ms

111 = 2293.76 ms

1X = Down Delay Control. Extra

delays of 3 x t_AVEto 34 x t_AVEare

added for down transitions, before

the new backlight target is

programmed. (see Down Delay

section).

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 is 010 = Zone 2

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

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:

2V

255

7.8 mV

=

ZoneBoundaryLSB =

(7)

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

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

Line-Break

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

34

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

Line-Break

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

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

Line-Break

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

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

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)

Line-Break

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)

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]).

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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

Part Number

Value

Size

Current Rating

DC Resistance

TDK

VLS252010T-100M

10 µH

2.5 mm × 2

mm × 1 mm

590 mA

0.712Ω

TDK

VLS2012ET-100M

VLF301512MT-100M

VLF4010ST-100MR80

VLS252012T-100M

VLF3014ST-100MR82

VLF4014ST-100M1R0

XPL2010-103ML

10 µH

2 mm × 2 mm

× 1.2 mm

695 mA

690 mA

800 mA

810 mA

820 mA

1000 mA

610 mA

550 mA

0.47Ω

0.25Ω

0.63Ω

0.25Ω

0.22Ω

0.56Ω

0.54Ω

3.0 mm × 2.5

mm × 1.2mm

TDK

2.8 mm × 3

mm × 1 mm

TDK

2.5 mm × 2

mm × 1.2mm

TDK

2.8 mm × 3

mm × 1.4mm

TDK

3.8 mm × 3.6

mm × 1.4 mm

Coilcraft

1.9 mm × 2

mm × 1 mm

LPS3010-103ML

2.95 mm ×

2.95 mm × 0.9

mm

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

36

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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

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 44 highlights these two noise

generating components.

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Voltage Spike

V_OUT+ V_FSchottky

Pulsed voltage at SW

Current through

I

Schottky Diode and C_OUT

PEAK

I

= I

IN

AVE

Paracitic

Current through

inductor

Circuit Board

Inductances

Affected Node

due to capacitive

coupling

Cp1

L

Lp1

Lp2

D1

Up to 40V

C_OUT

2.7V to 5.5V

SW

V_LOGIC

IN

Lp3

10 kW

SCL

SDA

OVP

LM3532

LCD Display

ILED1

ILED2

ILED3

GND

Figure 44. LM3532's Boost Converter Showing Pulsed Voltage at SW (High dV/dt) and

Current Through Schottky and COUT (High dI/dt)

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

•

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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 Example Layouts).

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 (See Example Layouts).

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 Example Layouts).

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). Depending 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.

Figure 45 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).

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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 45, 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.

I

SUPPLY

DI

L

R

S

L

S

SW

IN

V

IN

LM3532

Supply

C

IN

I

SUPPLY

R

S

L

S

C

DI

IN

L

2

R_S

4 x L_S²

1

>

1.

L_Sx C_IN

1

2.

3.

f_RESONANT

=

2p L_Sx C_IN

1

2p x 500 kHz x C_IN

D

_Lx

I_SUPPLYRIPPLEö I

2

≈

’

÷

◊

1

2

∆

R_S+ 2p x 500kHz x L_S-

∆

x

2p 500 kHz C_IN

«

Figure 45. Input RLC Network

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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.

CIN

IN

LM3532

GND

L

Schottky

SW

Diode

OUT

COUT

Figure 46. Layout Example #1

Schottky

Diode

CIN

GND

IN

COUT

OUT

LM3532

L

SW

Figure 47. Layout Example #2

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REVISION HISTORY

Changes from Revision B (July 2012) to Revision C

Page

•

added "I_{FULL_SCALE}= 20.2mA, Brightness Code = 0xFF" to 2.7V ≤ V_IN≤ 5.5V in conditions for Imatch ............................... 4

Changed layout of National Data Sheet to TI format .......................................................................................................... 41

Changes from Revision C (March 2013) to Revision D

Page

•

Updated Output Configuration Register defaults: in col. 2 from "00" to "1X"; in col. 3 from "00" to "01". .......................... 28

42

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PACKAGE MATERIALS INFORMATION

www.ti.com

3-Jun-2013

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device

Package Package Pins

Type Drawing

SPQ

Reel

A0

B0

K0

P1

W

Pin1

Diameter Width (mm) (mm) (mm) (mm) (mm) Quadrant

(mm) W1 (mm)

LM3532TME-40A/NOPB DSBGA

LM3532TMX-40A/NOPB DSBGA

YFQ

16

250

178.0

8.4

1.85

2.01

0.76

4.0

8.0

Q1

3000

Pack Materials-Page 1

PACKAGE MATERIALS INFORMATION

www.ti.com

3-Jun-2013

*All dimensions are nominal

Device

Package Type Package Drawing Pins

SPQ

Length (mm) Width (mm) Height (mm)

LM3532TME-40A/NOPB

LM3532TMX-40A/NOPB

DSBGA

YFQ

16

250

210.0

185.0

35.0

3000

Pack Materials-Page 2

MECHANICAL DATA

YFQ0016xxx

D

0.600±0.075

E

TMD16XXX (Rev A)

D: Max = 1.87 mm, Min = 1.81 mm

E: Max = 1.77 mm, Min = 1.71 mm

4215081/A

12/12

A. All linear dimensions are in millimeters. Dimensioning and tolerancing per ASME Y14.5M-1994.

B. This drawing is subject to change without notice.

NOTES:

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TI E2E Community

e2e.ti.com

www.ti.com/wirelessconnectivity

Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265


型号：	LM3532TME-40A/NOPB
厂家：	TEXAS INSTRUMENTS
描述：	LM3532 High Efficiency White LED Driver with Programmable Ambient Light Sensing Capability and I2C-Compatible Interface LM3532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47页 (文件大小：1063K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LM3532TME-40A/NOPB [TI]

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