TI1 LM3532 Lm3532 high efficiency white led driver with programmable ambient light sensing capability and i2c-compatible interface Datasheet

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
Check for Samples: LM3532
FEATURES
APPLICATIONS
•
•
1
2
•
•
•
•
•
•
•
•
•
•
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
Programmable Dual Ambient Light Sensor
Inputs with Internal Sensor Gain Selection
Dual External PWM Inputs for LED Brightness
Adjustment
Independent Current String Brightness Control
Programmable LED Current Ramp Rates
40V Over-Voltage Protection
1A Typical Current Limit
•
Power Source for White LED Backlit LCD
Displays
Programmable Keypad Backlight
DESCRIPTION
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 allowing for a wide variety of
backlight + keypad applications.
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.
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
VOUT up to 40V
D1
VIN
CIN
COUT
IN
SW
OVP
VALS
Ambient Light
Sensor 1
Ambient Light
Sensor 2
VIN
ALS1
ALS2
LM3532
SDA
SCL
INT
ILED1
ILED2
ILED3
PWM1
T0
PWM2
HWEN
PGND
1
2
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.
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.
Copyright © 2011–2013, Texas Instruments Incorporated
LM3532
SNVS653D – JULY 2011 – REVISED JUNE 2013
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Application Circuit Component List
Value
Size (mm)
Current/Voltage
Rating (Resistance)
Component
Manufacturer's Part Number
White LED
Driver
LM3532
L
COILCRAFT
LPS4018-103ML
10 µH
3.9 mm x 3.9 mm x 1.7 mm
1A (RDC = 0.2Ω)
COUT
Murata
GRM21BR71H105KA12L
1µF
0805
50V
CIN
Murata
GRM188R71A225KE15D
2.2 µF
0603
10V
1.745 mm x 1.845 mm x 0.6 mm
Connection Diagram
Top View
A1
A2
A3
A4
B1
B2
B3
B4
C1
C2
C3
C4
D1
D2
D3
D4
Figure 1. 16-Bump (1.745 mm × 1.845 mm × 0.6 mm)
DSBGA Package YFQ0016
PIN DESCRIPTIONS
2
Pin
Name
Description
A1
OVP
A2
ILED3
Input Terminal to High Voltage Current Sink #3 (40V max). The boost converter regulates the
minimum of ILED1, ILED2, or ILED3 to 0.4V.
A3
ILED2
Input Terminal to High Voltage Current Sink #2 (40V max). The boost converter regulates the
minimum of ILED1, ILED2, or ILED3 to 0.4V.
A4
ILED1
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
ALS1
Ambient Light Sensor Input 1.
B2
ALS2
Ambient Light Sensor Input 2.
B3
HWEN
Active High Hardware Enable. Pull this pin high to enable the LM3532. HWEN is a high
impedance input.
Input Voltage Connection. Bypass IN to GND with a minimum 2.2 µF ceramic capacitor.
Output Voltage Sense Connection for Over Voltage Sensing. Connect OVP to the positive
terminal of the output capacitor.
B4
IN
C1
PWM2
External PWM Brightness Control Input 2.
C2
PWM1
External PWM Brightness Control Input 1.
C3
INT
C4
GND
Ground
D1
SDA
Serial Data Connection for I2C-Compatible Interface
D2
SCL
Serial Clock Connection for I2C-Compatible Interface
D3
T0
Unused test input. This pin must be tied externally to GND for proper operation.
D4
SW
Drain Connection for boost converters internal NFET
Programmable Interrupt Pin. INT is an open drain output that pulls low when the ALS changes
zones.
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LM3532
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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.
ABSOLUTE MAXIMUM RATINGS
(1) (2) (3)
−0.3V to +6V
VIN to GND
−0.3V to +45V
VSW, VOVP, VILED1, VILED2, VILED3 to GND
VSCL, VSDA, VALS1, VALS2, VPWM1, VPWM2, VINT, VHWEN, VT0 to GND
−0.3V to +6V
Continuous Power Dissipation
Internally Limited
Junction Temperature (TJ-MAX)
+150°C
−65°C to +150°C
Storage Temperature Range
Maximum Lead Temperature (Soldering, 10s)
ESD Rating
Human Body Model
(1)
(2)
(3)
(4)
(5)
(4)
+300°C
(5)
2.0 kV
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.
All voltages are with respect to the potential at the GND pin.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications
For detailed soldering specifications and information, please refer to Application Note AN-1112: DSBGA Wafer Level Chip Scale
Package (SNVA009).
The human body model is a 100 pF capacitor discharged through 1.5 kΩ resistor into each pin. (MIL-STD-883 3015.7).
OPERATING RATINGS
(1) (2)
VIN to GND
2.7V to 5.5V
VSW, VOVP, VILED1, VILED2, VILED3 to GND
Junction Temperature Range (TJ) (3)
(1)
(2)
(3)
(4)
0 to +40V
(4)
−40°C to +125°C
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.
All voltages are with respect to the potential at the GND pin.
Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ=+140°C (typ.) and
disengages at TJ=+125°C (typ.).
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 (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP =
+125°C), the maximum power dissipation of the device in the application (PD-MAX), and the junction-to ambient thermal resistance of the
part/package in the application (θJA), as given by the following equation: TA-MAX = TJ-MAX-OP – (θJA × PD-MAX).
THERMAL PROPERTIES
Thermal Resistance Junction to Ambient (TJA) (1)
(1)
61.3°C/W
Junction-to-ambient thermal resistance (θJA) 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 θJA of 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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ELECTRICAL CHARACTERISTICS
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(1) (2)
Limits in standard type face are for TA = +25°C and those in boldface type apply over the full operating ambient temperature
range (−30°C ≤ TA ≤ +85°C). Unless otherwise specified VIN = 3.6V.
Symbol
ILED(1/2/3)
IMATCH
(3) (4)
,
Parameter
Conditions
Min
Typ
Max
Units
Output Current Regulation Accuracy
(ILED1, ILED2 or ILED3)
2.7V ≤ VIN ≤ 5.5V, ControlX Full-Scale
Current Register = 0xF3, Brightness
Code = 0xFF
18.68
20.2
21.8
mA
ILED2 to ILED3 Current Matching
2.7V ≤ VIN ≤ 5.5V, IFULL_SCALE =
20.2mA, Brightness Code = 0xFF
−2
0.3
2
%
VREG_CS
Regulated Current Sink Headroom
Voltage
VHR
Current Sink Minimum Headroom
Voltage
ILED = 95% of nominal, ILED = 20.2
mA
RDSON
NMOS Switch On Resistance
ISW = 100 mA
ICL
NMOS Switch Current Limit
2.7V ≤ VIN ≤ 5.5V
880
VOVP
Output Over-Voltage Protection
ON Threshold, 2.7V ≤ VIN ≤ 5.5V
40
fSW
Switching Frequency
DMAX
Maximum Duty Cycle
DMIN
Minimum Duty Cycle
IQ
Quiescent Current into IN, Device
Not Switching
ILED1 = ILED2 = ILED3 = 20.2 mA,
feedback disabled.
IQ_SW
Switching Supply Current
ILED1 = ILED2 = ILED3 = 20.2 mA, VOUT
= 32V
ISHDN
Shutdown Current
2.7V ≤ VIN ≤ 5.5V, HWEN = GND
Minimum LED Current in ILED1,
ILED2 or ILED3
Full-Scale Current =20.2 mA
Brightness code = 0x01, Mapping =
Exponential
ILED_MIN
400
200
240
mV
1000
1120
mA
41
42
Ω
0.25
Hysteresis
1
2.7V ≤ VIN ≤ 5.5V
450
500
550
kHz
%
10
%
490
µA
1.35
mA
2
9.5
µA
µA
+140
Hysteresis
V
94
1
Thermal Shutdown
TSD
mV
°C
15
LOGIC INPUTS/OUTPUTS (PWM1, PWM2, HWEN, SCL, SDA, INT)
VIL
Input Logic Low
2.7V ≤ VIN ≤ 5.5V
0
0.4
VIH
Input Logic High
2.7V ≤ VIN ≤ 5.5V
1.2
VIN
VOL
Output Logic Low (SCL, INT)
2.7V ≤ VIN ≤ 5.5V, ILOAD = 3mA
RPWM
PWM Input Internal Pulldown
Resistance (PWM1, PWM2)
0.4
100
V
V
kΩ
I2C-COMPATIBLE TIMING SPECIFICATIONS (SCL, SDA, ) (5)
t1
SCL (Clock Period)
2.5
µs
t2
Data In Setup Time to SCL High
100
ns
t3
Data Out Stable After SCL Low
0
ns
t4
SDA Low Setup Time to SCL Low
(Start)
100
ns
t5
SDA High Hold Time After SCL High
(Stop)
100
ns
AMBIENT LIGHT SENSOR INPUTS (ALS1, ALS2)
RALS1, RALS2
(1)
(2)
(3)
(4)
(5)
4
ALS Pin Internal Pulldown Resistors
ALS1, ALS2 Resistor Select Register
= 0x0F,
2.7V ≤ VIN ≤ 5.5V
2.29
2.44
2.59
kΩ
All voltages are with respect to the potential at the GND pin.
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: VIN = 3.6V and TA = +25°C.
All Current sinks for the matching spec are assigned to the same Control Bank.
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.
SCL and SDA must be glitch-free in order for proper brightness control to be realized.
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ELECTRICAL CHARACTERISTICS (1)(2) (continued)
Limits in standard type face are for TA = +25°C and those in boldface type apply over the full operating ambient temperature
range (−30°C ≤ TA ≤ +85°C). Unless otherwise specified VIN = 3.6V.
Symbol
Parameter
VALS_REF
Ambient Light Sensor Reference
Voltage
VOS
ALS Input Offset Voltage
(Code 0 to 1 transition - VLSB)
tCONV
Conversion Time
LSB
ADC Resolution
Conditions
Min
Typ
Max
Units
2.7V ≤ VIN ≤ 5.5V
1.94
2
2.06
V
2.7V ≤ VIN ≤ 5.5V
0.8
2.5
4.2
mV
154
µs
2.7V ≤ VIN ≤ 5.5V
7.84
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TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.6V, LEDs (VF = 3.2V@20 mA, TA = 25°C), COUT = 1µF, CIN = 2.2 µF, L = Coilcraft LPS4018 (10 µH or 22 µH), TA =
+25°C unless otherwise specified.
Efficiency vs VIN
Single String, ILED = 20.2mA
L = LPS4018-103ML (10µH)
Efficiency vs VIN
Single String, ILED = 20.2mA
L = LPS4018-103ML (10µH)
94
92
92
90
3 LEDs
90
88
4 LEDs
86
Efficiency (%)
Efficiency(%)
88
84
82
80
9 LEDs
5 LEDs
7 LEDs
84
82
8 LEDs
6 LEDs
76
76
74
3.0
3.5
4.0
4.5
5.0
72
2.5
5.5
3.0
3.5
5.0
5.5
Figure 3.
Efficiency vs VIN
Dual String, ILED = 20.2mA per string
L = LPS4018-103ML (10µH)
Efficiency vs VIN
Dual String, ILED = 20.2mA per string
L = LPS4018-103ML (10µH)
90
3 LEDs
88
86
Efficiency (%)
Efficiency(%)
4.5
Figure 2.
92
84
82
9 LEDs
7 LEDs
80
78
5 LEDs
76
74
2.5
3.0
3.5
4.0
4.5
5.0
5.5
93
91
89
87
85
83
81
79
77
75
73
71
69
67
65
2.5
4 LEDs
8 LEDs
6 LEDs
3.0
3.5
VIN (V)
4.0
4.5
10 LEDs
5.0
5.5
VIN (V)
Figure 4.
Figure 5.
Efficiency vs VIN
Triple String, ILED = 20.2mA per string
L = LPS4018-103ML (10µH)
Efficiency vs VIN
Triple String, ILED = 20.2mA per string
L = LPS4018-103ML (10µH)
92
90
94
3 LEDs
92
88
90
86
88
Efficiency (%)
Efficiency (%)
4.0
VIN (V)
VIN (V)
84
9 LEDs
7 LEDs
82
80
78
86
84
82
80
6 LEDs
8 LEDs
10 LEDs
76
74
72
2.5
4 LEDs
78
5 LEDs
76
74
3.0
3.5
4.0
4.5
5.0
72
2.5
5.5
VIN (V)
3.0
3.5
4.0
4.5
5.0
5.5
VIN (V)
Figure 6.
6
10 LEDs
80
78
78
74
2.5
86
Figure 7.
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 3.6V, LEDs (VF = 3.2V@20 mA, TA = 25°C), COUT = 1µF, CIN = 2.2 µF, L = Coilcraft LPS4018 (10 µH or 22 µH), TA =
+25°C unless otherwise specified.
Efficiency vs VIN
Single String, ILED = 20.2mA per string
L = LPS4018-223ML (22µH)
Efficiency vs VIN
Single String, ILED = 20.2mA per string
L = LPS4018-223ML (22µH)
92
92
90
90
3 LEDs
86
84
82
80
5 LEDs
9 LEDs
7 LEDs
86
84
8 LEDs
82
6 LEDs
10 LEDs
80
78
78
76
74
2.5
4 LEDs
88
Efficiency (%)
Efficiency(%)
88
3.0
3.5
4.0
4.5
5.0
76
2.5
5.5
3.0
3.5
4.0
5.5
Figure 9.
Efficiency vs VIN
Dual String, ILED = 20.2mA per string
L = LPS4018-223ML (22µH)
Efficiency vs VIN
Dual String, ILED = 20.2mA per string
L = LPS4018-223ML (22µH)
94
94
92
90
88
86
84
82
80
78
76
74
72
70
68
66
2.5
3 LEDs
90
88
9 LEDs
86
84
Efficiency (%)
Efficiency (%)
5.0
Figure 8.
92
7 LEDs
82
80
5 LEDs
78
76
74
72
2.5
3.0
3.5
4.0
4.5
5.0
5.5
4 LEDs
8 LEDs
10 LEDs
6 LEDs
3.0
3.5
4.0
VIN (V)
4.5
5.0
5.5
VIN (V)
Figure 10.
Figure 11.
Efficiency vs VIN
Triple String, ILED = 20.2mA per string
L = LPS4018-223ML (22µH)
Efficiency vs VIN
Triple String, ILED = 20.2mA per string
L = LPS4018-223ML (22µH)
94
92
94
92
3 LEDs
90
90
88
88
86
86
84
9 LEDs
7 LEDs
82
Efficiency (%)
Efficiency (%)
4.5
VIN (V)
VIN (V)
80
78
5 LEDs
84
82
78
76
74
74
72
2.9
3.6
4.2
4.9
70
2.5
5.5
VIN (V)
10 LEDs
8 LEDs
80
76
72
2.3
4 LEDs
6 LEDs
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)
VIN = 3.6V, LEDs (VF = 3.2V@20 mA, TA = 25°C), COUT = 1µF, CIN = 2.2 µF, L = Coilcraft LPS4018 (10 µH or 22 µH), TA =
+25°C unless otherwise specified.
Efficiency vs ILED
Triple String, VIN = 3.6V
L = LPS4018-103ML (10µH)
Efficiency vs ILED Triple String, VIN = 3.6V
L = LPS4018-103ML (10µH)
91
91
90
3 LEDs
89
89
88
88
87
87
Efficiency (%)
Efficiency (%)
90
86
85
5 LEDs
84
83
7 LEDs
86
85
84
6 LEDs
83
8 LEDs
82
82
81
9 LEDs
81
4 LEDs
10 LEDs
80
80
79
0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90
79
0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90
ILED (mA)
ILED (mA)
Figure 14.
Figure 15.
Efficiency vs ILED
Triple String, VIN = 3.6V
L = LPS4018-223ML (22µH)
Efficiency vs ILED
Triple String, VIN = 3.6V
L = LPS4018-223ML (22µH)
91
91
3 LEDs
90
5 LEDs
88
86
7 LEDs
85
84
83
86
85
8 LEDs
84
83
81
81
80
80
9
6 LEDs
87
82
9 LEDs
82
79
0
4 LEDs
88
87
Efficiency (%)
Efficiency (%)
90
89
89
10 LEDs
79
0
18 27 36 45 54 63 72 81 90
9
18 27 36 45 54 63 72 81 90
ILED (mA)
ILED (mA)
Figure 16.
Figure 17.
Shutdown Current vs VIN
HWEN = GND
240.0
1.6
Current Sink Matching vs VIN
ILED2 to ILED3
220.0
-40°C
200.0
85C
1.2
-40C
25C
0.9
'ILED (PA)
Shutdown Current (PA)
1.4
0.7
180.0
240.0
220.0
160.0
200.0
180.0
160.0
140.0
140.0
120.0
120.0
100.0
80.0
60.0
100.0
40.0
20.0
80.0
0.0
60.0
25°C
40.0
85°C
20.0
0.5
2.5
0.0
3.1
3.7
4.3
4.9
5.5
2.5
3.1
3.7
4.3
4.9
5.5
VIN (V)
VIN (V)
Figure 18.
8
Figure 19.
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 3.6V, LEDs (VF = 3.2V@20 mA, TA = 25°C), COUT = 1µF, CIN = 2.2 µF, L = Coilcraft LPS4018 (10 µH or 22 µH), TA =
+25°C unless otherwise specified.
Current Sink Matching vs VIN
ILED1 to ILED2 to ILED3
(ΔILED is worst case difference between all three strings)
ALS Resistance vs VIN
RALS1, (2.44kΩ setting)
500
TA = -40°C
2.450k
400
2.448k
350
2.446k
300
RALS1 (:)
'ILED (PA)
450
TA = +85°C
250
85°C
2.444k
2.442k
25°C
2.440k
200
2.438k
150
2.436k
TA = +25°C
-40°C
100
50
2.5
3.1
3.7
4.3
4.9
2.5
5.5
3.0
3.5
4.5
5.0
5.5
Figure 20.
Figure 21.
ALS Resistor Matching vs VIN
(2.44kΩ setting)
Integral Non Linearity vs Code
(Endpoint Method)
10.000
1.00
8.000
0.75
6.000
0.50
4.000
85°C
0.25
2.000
LSB's
ALS Resistor Matching (:)
VIN (V)
0.000
25°C
-2.000
0.00
-0.25
-4.000
-0.50
-6.000
-40°C
-8.000
-10.000
2.5
3.0
3.5
4.0
-0.75
4.5
5.0
-1.00
0
5.5
32
64
VIN (V)
128 160 192 224 256
Figure 22.
Figure 23.
Differential Non Linearity vs Code
Peak to Peak LED Current Ripple vs fPWM
22.0
0.90
20.0
0.80
LED Current Ripple (mA)
18.0
0.70
0.60
0.50
0.40
0.30
0.20
0.10
16.0
14.0
12.0
10.0
8.0
6.0
4.0
0.00
-0.10
0
96
Code (D)
1.00
LSB's
4.0
VIN (V)
2.0
32
64
96
0.0
0.01
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)
VIN = 3.6V, LEDs (VF = 3.2V@20 mA, TA = 25°C), COUT = 1µF, CIN = 2.2 µF, L = Coilcraft LPS4018 (10 µH or 22 µH), TA =
+25°C unless otherwise specified.
LED Current vs Headroom Voltage
31
30
29
-40°C
28
ILED (mA)
27
26
25°C
25
85°C
24
23
22
21
20
19
0.10
0.15
0.20
0.25
0.30
0.35
0.40
VHR (V)
Figure 26.
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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).
VIN
SW
CIN
400 mV
COUT
OVP
Error Amplifier
+
IN
Boost
Controller
250 m:
ILED1
ILED2
VHR Min
ILED3
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
ALS
Processor
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Controls
Outputs
(Masters: Output configuration)
(Ramp rates, brightness management)
(ALS processor select, enable)
(Slaves)
ALS1
ALSP_1
Bank_A
ILED1
PWM
Filters
Bank_B
ILED2
Bank_C
ILED3
ALS2
CABC1
CABC2
PWM_0
PWM_1
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 (ILED_FULL_SCALE). Full-scale
current for the respective Control Bank is set via the Control A Full-Scale Current Register, the Control B FullScale 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:
ILED = ILED_ FULLSCALE x 0.85
§Code +1·º
ª
«40 - ¨ 6.4 ¸»
©
¹¼
¬
x DPWM
(1)
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 exponential mapped mode (Figure 29) shows the typical
response of % full-scale current setting vs 8-bit brightness code.
% FULL SCALE
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:
ILED = ILED_ FULLSCALE x
1
x Code x DPWM
255
(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
% FULL SCALE
80
70
60
50
40
30
20
10
0
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
Output Configuration
Register
Bits[1:0] = 00, assigns
ILED1 to Control Bank A
Bits[3:2] = 00 assigns
ILED2 to Control Bank A
Bits[5:4] = 00, assigns
ILED3 to Control Bank A
Brightness Register
Control A Brightness
Configuration Register
Bits [4:2]
000 selects Control A
Zone Target 0 as
brightness register
001 selects Control A
Zone Target 1
brightness register
010 selects Control A
Zone Target 2
brightness register
011 selects Control A
Zone Target 3
brightness register
1XX selects Control A
Zone Target 4
brightness register
PWM Select
Control A PWM
Register Bit[0]
0 selects PWM1
1 selects PWM2
PWM Enable
Control A PWM Register
Bit[2] is PWM enable when Control
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
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
Current Sink Enable
Control Enable
Register Bit [0]
0 = Bank A Disabled
1 = Bank A Enabled
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:
RALS_ =
2V
u Code
54 PA
(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
VALS_REF = 2V
Zone 4
Zone 3
Zone
Boundary 2_
Zone
Boundary 1_
Zone 2
Zone
Boundary 0_
LED Current
VALS1 or VALS2
Zone
Boundary 3_
Zone 1
Zone 0
Zone
Target 0
Zone
Target 1
Zone
Target 2
Zone
Zone
Target 3 Target 4
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 4
Zone Boundary 3 High
Zone Boundary 3 Low
Zone 3
Zone 3
Zone 3
Zone Boundary 2 High
Zone Boundary 2 Low
Zone 2
Zone 2
Zone 2
Zone 2
Zone Boundary 1 High
Zone Boundary 1 Low
Zone 1
Zone 1
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 Register
ADC Average
Register
Up Only Control
(Up Delay = 3 x tAVE)
Read Back
Ambient Light
Zone Register
ALS1
ADC
(7.142ksps)
Direct ALS Control
(Up and Down Delay
Averager
Output
Averager
Read Back
Brightness Zone
Register
ALS Brightness
Control Target
= 3 x tAVE)
ALS2
Down Delay Control
ALS Input Select
(ALS Configuration
Register Bits[7:6])
(Down Delay =
4 x tAVE to 35 x tAVE)
ALS Average Time
(ALS Configuration
Register Bits [2:0])
ALS Configuration
Register Bits [5:4]
Up Delay = 3 x tAVE
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.
tAVERAGE
(set via bits [2:0] of the ALS
Configuration Register)
tCONV = 140 Ps
I2C Write
ALS Enabled
ConConConversion version version
1
2
3
ConConversion version
n
n+1
VALS
(active input is sampled)
ADC Register
(Read Only, Updated every tCONV)
Sample Sample Sample
1
2
3
Sample
n
Average Period #2
Average Period #1
ADC Average Register
(Read Only, Updated every tAVERAGE)
0x00
=
Sample 1 + Sample 2 + Sample 3 + « 6DPSOH Q
n
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/tAVE.
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
Average Period
(1.1 ms)
I2C
Normal ALS
Average Period
ALS Enable
VALS_Y
VALS_X
ALS Zone
Zone 0
Zone 0
Zone 0
Zone X
Zone 0
Zone X
Zone X
Zone Y
Zone Target y
Zone Target x
Run Time
Ramp Rate
ILED_
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:
1.
2.
3.
4.
5.
6.
7.
ALS Rules
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.
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.
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.
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.
The Averager Output (see Figure 33) contains the zone that is determined from the most recent full average
period.
The ALS Interface only forces a change in the backlight current at the beginning of an average period.
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
1
2
3
4
5
6
7
8
9
10
11
12
13
2V
Average
Period #
Zone 4
Zone 3
Zone 2
VALS_
Zone 1
Zone 0
Current Average Zone 4
Averager Ouput
0
4
4
3
4
3
2
3
3
1
2
2
1
3
2
3
3
3
3
4
3
4
4
4
4
4
4
*Note:it takes a full
average period to
generate an averager
output value
Zone 4 Brightness Target
Zone 4 Brightness Target
LED Current Run Time
Ramp Down
ILED
Zone 3 Brightness Target
Zone 2 Brightness Target
LED Current Run
Time Ramp Up
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
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
2V
Average
Period #
Zone 4
Zone 3
VALS_
Zone 2
Zone 1
Zone 0
Current Average
Zone
Averager Ouput
*Note:it takes a
full average
period to
generate an
averager
output value
0
3
2
2
2
2
2
2
4
4
4
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
0
3
3
2
2
2
2
2
2
4
4
4
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
Zone 4 Brightness Target
Zone 3 Brightness Target
ILED
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
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 (VOVP) the boost converter is turned off, and switching will stop until VOUT falls below the
OVP hysteresis (VOVP – 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 (ICL = 880 mA min.), and
the maximum output voltage (VOVP = 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:
IPEAK =
VIN x efficiency
VIN
IOUT x VOUT
x 1+
VOUT
2 x fsw x L
VIN x efficiency
(4)
For Discontinuous Conduction Mode the peak inductor current is given by:
IPEAK =
2 x IOUT
fsw x L x efficiency
x VOUT - VIN 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.
VIN x efficiency
VIN
IOUT x VOUT
x 1>
VOUT
VIN x efficiency fsw x L
(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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0.1
44
0.095
42
0.09
40
0.085
38
0.08
36
0.075
VOUT (V)
IOUT (A)
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.
0.07
0.065
0.06
30
28
0.055
26
VOUT = 22V
VOUT = 24V
VOUT = 26V
VOUT = 30V
VOUT = 34V
VOUT = 38V
0.05
0.045
0.04
2.5
34
32
2.8
3.1
3.4
3.7
4
4.3
4.6
4.9
5.2
IOUT = 45 mA
IOUT = 50 mA
IOUT = 60 mA
IOUT = 70 mA
IOUT = 80 mA
24
22
20
2.5
5.5
2.8
3.1
3.4
3.7
VIN (V)
4.3
4.6
4.9
5.2
5.5
VIN (V)
0.1
VOUT = 22V
0.095
VOUT = 24V
VOUT = 26V
0.09
VOUT = 30V
VOUT = 34V
0.085
VOUT = 38V
0.08
0.075
0.07
0.065
0.06
0.055
0.05
0.045
0.04
0.035
0.03
2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5 4.75 5 5.25 5.5
Figure 39. Maximum Output Power (22 µH)
VOUT (V)
Figure 38. Maximum Output Power (22 µH)
IOUT (A)
4
44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
2.5
IOUT = 40 mA
IOUT = 50 mA
IOUT = 60 mA
IOUT = 70 mA
IOUT = 80 mA
IOUT = 45 mA
2.8
3.1
3.4
3.7
4
4.3
4.6
4.9
5.2
5.5
VIN (V)
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
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.
t1
SCL
t5
t4
SDIO
Data In
t2
SDIO
Data Out
t3
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
0
Bit 7
1
Bit 6
1
Bit 5
1
Bit 4
0
Bit 3
LSB
0
Bit 2
0
Bit 1
R/W
Bit 0
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
0x10
0xE4
Startup/Shutdown Ramp Rate
0x11
0xC0
Run Time Ramp Rate
0x12
0xC0
Control A PWM
0x13
0x82
Control B PWM
0x14
0x82
Control C PWM
0x15
0x82
Control A Brightness
0x16
0xF1
Control A Full-Scale Current
0x17
0xF3
Control B Brightness
0x18
0xF1
Control B Full-Scale Current
0x19
0xF3
Control C Brightness
0x1A
0xF1
Control C Full-Scale Current
0x1B
0xF3
Feedback Enable
0x1C
0xFF
Control Enable
0x1D
0xF8
ALS1 Resistor Select
0x20
0xE0
ALS2 Resistor Select
0x21
0xE0
ALS Down Delay
0x22
0xE0
ALS Configuration
0x23
0x44
ALS Zone Information
0x24
0xF0
ALS Brightness Zone
0x25
0xF8
ADC
0x27
0x00
ADC Average
0x28
0x00
ALS Zone Boundary 0 High
0x60
0x35
ALS Zone Boundary 0 Low
0x61
0x33
ALS Zone Boundary 1 High
0x62
0x6A
ALS Zone Boundary 1 Low
0x63
0x66
ALS Zone Boundary 2 High
0x64
0xA1
ALS Zone Boundary 2 Low
0x65
0x99
ALS Zone Boundary 3 High
0x66
0xDC
ALS Zone Boundary 3 Low
0x67
0xCC
Control A Zone Target 0
0x70
0x33
Control A Zone Target 1
0x71
0x66
Control A Zone Target 2
0x72
0x99
Control A Zone Target 3
0x73
0xCC
Control A Zone Target 4
0x74
0xFF
Control B Zone Target 0
0x75
0x33
Control B Zone Target 1
0x76
0x66
Control B Zone Target 2
0x77
0x99
Control B Zone Target 3
0x78
0xCC
Control B Zone Target 4
0x79
0xFF
Control C Zone Target 0
0x7A
0x33
Control C Zone Target 1
0x7B
0x66
Control C Zone Target 2
0x7C
0x99
Control C Zone Target 3
0x7D
0xCC
Control C Zone Target 4
0x7E
0xFF
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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)
Bit [7:6]
Not Used
Bits [5:4]
ILED3 Control
Bits [3:2]
ILED2 Control
Bits [1:0]
ILED1 Control
00 = ILED3 is controlled by Control A
PWM and Control A Brightness
Registers
01 = ILED3 is controlled by Control B
PWM and Control B Brightness
Registers
1X = ILED3 is controlled by Control C
PWM and Control C Brightness
Registers (default)
00 = ILED2 is controlled by Control A
PWM and Control A Brightness Registers
01 = ILED2 is controlled by Control B
PWM and Control B Brightness Registers
(default)
1X = ILED2 is controlled by Control C
PWM and Control C Brightness Registers
00 = ILED1 is controlled by Control A
PWM and Control A Brightness
Registers (default)
01 = ILED1 is controlled by Control B
PWM and Control B Brightness
Registers
1X = ILED1 is controlled by Control 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 Equation 5.
Table 4. Startup/Shutdown Ramp Rate Register Description (Address 0x11)
Bits [7:6]
Not Used
Bits [5:3]
Shutdown Ramp
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)
Bits [2:0]
Startup Ramp
000 = 8µs/step (2.048ms from Full-Scale to 0) (default)
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]
Not Used
28
Bits [5:3]
Ramp Down
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
Bits [2:0]
Ramp Up
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
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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 2 PWM
Enable
Bit 2
Zone 1 PWM
Enable
Bit 2
Zone 0 PWM
Enable
0 = Active PWM 0 = Active PWM
input is disabled input is disabled in
in Zone 4
Zone 3 (default)
(default)
0 = Active
PWM input is
disabled in
Zone 2
(default)
0 = Active PWM
input is disabled
in Zone 1
(default)
0 = Active PWM 0 = active low
input is disabled polarity
in Zone 0
(default)
1 = Active PWM 1 = Active PWM
input is enabled input is enabled in
in Zone 4
Zone 3
1 = Active
PWM input is
enabled in
Zone 2
1 = Active PWM 1 = Active PWM 1 = active high 1 = PWM2 is
input is enabled input is enabled polarity
mapped to
in Zone 1
in Zone 0
(default)
Control Bank A
Not Used
Bit 1
PWM Input
Polarity
Bit 0
PWM Select
0 = PWM1 input
is mapped to
Control Bank A
(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
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
input is disabled
in Zone 4
(default)
0 = Active PWM
input is disabled
in Zone 3
(default)
0 = Active
PWM input is
disabled in
Zone 2
(default)
0 = Active PWM
input is disabled
in Zone 1
(default)
0 = Active PWM
input is disabled
in Zone 0
(default)
0 = active low
polarity
0 = PWM1
input is
mapped to
Control Bank B
(default)
1 = Active PWM
input is enabled
in Zone 4
1 = Active PWM
1 = Active
input is enabled in PWM input is
Zone 3
enabled in
Zone 2
1 = Active PWM
input is enabled
in Zone 1
1 = Active PWM
input is enabled
in Zone 0
1 = active high
polarity
(default)
1 = PWM2 is
mapped to
Control Bank B
Not Used
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
input is disabled
in Zone 4
(default)
0 = Active PWM
input is disabled
in Zone 3
(default)
0 = Active
PWM input is
disabled in
Zone 2
(default)
0 = Active PWM
input is disabled
in Zone 1
(default)
0 = Active PWM
input is disabled
in Zone 0
(default)
0 = active low
polarity
0 = PWM1
input is
mapped to
Control Bank C
(default)
1 = Active PWM
input is enabled
in Zone 4
1 = Active PWM
1 = Active
input is enabled in PWM input is
Zone 3
enabled in
Zone 2
1 = Active PWM
input is enabled
in Zone 1
1 = Active PWM
input is enabled
in Zone 0
1 = active high
polarity
(default)
1 = PWM2 is
mapped to
Control Bank C
Not Used
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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]
Control A Brightness Pointer (I2C
Current Control Only)
Bit 1
LED Current Mapping Mode
Bit 0
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]
Control A Brightness Pointer (I2C
Current Control Only)
Bit 1
LED Current Mapping Mode
Bit 0
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]
Control C Brightness Pointer (I2C
Current Control Only)
Bit 1
LED Current Mapping Mode
Bit 0
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
N/A
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
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
ILED3 Feedback Enable
Bit 1
ILED2 Feedback Enable
Bit 0
ILED1 Feedback Enable
N/A
0 = ILED3 is not part of the
boost control loop
1 = ILED3 is part of the boost
control loop (default)
0 = ILED2 is not part of the
boost control loop
1 = ILED2 is part of the
boost control loop (default)
0 = ILED1 is not part of the
boost control loop
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)
(Not Used)
Bit 2
Control C Enable
Bit 1
Control B Enable
Bit 0
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
N/A
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
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
N/A
Bit [5]
ALS Fast startup Enable
0 = ALS Fast startup is Disabled
1 = ALS Fast startup is Enabled (default)
Bits [4:0]
Down Delay
00000 = 6 total Average Period delay for Down Delay
Control (default)
:
:
:
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]
ALS Input Select
Bit [5:4]
ALS Control
00 = Average of ALS1 and
ALS2 is used to determine
backlight current
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
Bit 3
ALS Enable
Bits [2:0]
ALS Average Time
00 = Direct ALS Control. ALS inputs 0 = ALS is disabled (default)
respond to up and down transitions 1 = ALS is enabled
(default)
01 = This setting is for a future
mode.
1X = Down Delay Control. Extra
delays of 3 x tAVE to 34 x tAVE are
added for down transitions, before
the new backlight target is
programmed. (see Down Delay
section).
000 = 17.92 ms
001 = 35.84 ms
010 = 71.68 ms
011 = 143.36 ms
100 = 286.72 ms (default)
101 = 573.44 ms
110 = 1146.88 ms
111 = 2293.76 ms
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
N/A
Bit 3
Zone Change Bit
Bits [2:0]
Brightness Zone
0 = No change in ALS Zone (default)
1 = There was a change in the ALS Zone
since the last read of this register. This bit is
cleared on read back.
000 = Zone 0 (default)
001 = Zone 1
010 = Zone 2
011 = Zone 3
1XX = Zone 4
Table 19. ALS Zone Readback Register Description (Address 0x25)
Bits [7:3]
Not Used
N/A
Bits [2:0]
Brightness Zone
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:
ZoneBoundaryLSB =
2V
= 7.8 mV
255
(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
36
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
10 µH
2 mm × 2 mm
× 1.2 mm
695 mA
0.47Ω
TDK
VLF301512MT-100M
10 µH
3.0 mm × 2.5
mm × 1.2mm
690 mA
0.25Ω
TDK
VLF4010ST-100MR80
10 µH
2.8 mm × 3
mm × 1 mm
800 mA
0.25Ω
TDK
VLS252012T-100M
10 µH
2.5 mm × 2
mm × 1.2mm
810 mA
0.63Ω
TDK
VLF3014ST-100MR82
10 µH
2.8 mm × 3
mm × 1.4mm
820 mA
0.25Ω
TDK
VLF4014ST-100M1R0
10 µH
3.8 mm × 3.6
mm × 1.4 mm
1000 mA
0.22Ω
Coilcraft
XPL2010-103ML
10 µH
1.9 mm × 2
mm × 1 mm
610 mA
0.56Ω
Coilcraft
LPS3010-103ML
10 µH
2.95 mm ×
2.95 mm × 0.9
mm
550 mA
0.54Ω
Coilcraft
LPS4012-103ML
10 µH
3.9mm ×
3.9mm ×
1.1mm
1000 mA
0.35Ω
Coilcraft
LPS4012-223ML
22 µH
3.9 mm × 3.9
mm × 1.1 mm
780 mA
0.6Ω
Coilcraft
LPS4018-103ML
10 µH
3.9 mm × 3.9
mm × 1.7 mm
1100 mA
0.2Ω
Coilcraft
LPS4018-223ML
22 µH
3.9 mm × 3.9
mm × 1.7 mm
700 mA
0.36Ω
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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
Part Number
Value
Size
Rating
Description
Murata
GRM21BR71H105KA12
1 µF
0805
50V
COUT
Murata
GRM188B31A225KE33
2.2 µF
0805
10V
CIN
TDK
C1608X5R0J225
2.2 µF
0603
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
Part Number
Value
Size
Rating
Diodes Inc.
B0540WS
Schottky
SOD-323
40V/500 mA
Diodes Inc.
SDM20U40
Schottky
SOD-523 (1.2 mm × 0.8
mm × 0.6 mm)
40V/200 mA
On Semiconductor
NSR0340V2T1G
Schottky
SOD-523 (1.2 mm × 0.8
mm × 0.6 mm)
40V/250 mA
On Semiconductor
NSR0240V2T1G
Schottky
SOD-523 (1.2 mm × 0.8
mm × 0.6 mm)
40V/250 mA
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
VOUT + VF Schottky
Pulsed voltage at SW
Current through
Schottky Diode and COUT
IPEAK
IAVE = IIN
Current through
inductor
Paracitic
Circuit Board
Inductances
Affected Node
due to capacitive
coupling
Cp1
L
Lp1
D1
2.7V to 5.5V
Up to 40V
COUT
VLOGIC
SW
IN
10 k:
Lp2
Lp3
10 k:
SCL
OVP
SDA
LM3532
LCD Display
ILED1
ILED2
GND
ILED3
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
38
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Output Capacitor Placement
The output capacitor is in the path of the inductor current discharge current. As a result, COUT sees a high current
step from 0 to IPEAK each 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 COUT and back into
the LM3532's GND pin will contribute to voltage spikes (VSPIKE = LPX × dI/dt) at SW and OUT which can
potentially over-voltage the SW pin, or feed through to GND. To avoid this, COUT+ must be connected as close as
possible to the Cathode of the Schottky diode and COUT− must be connected as close as possible to the
LM3532's GND bump. The best placement for COUT is 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 IPEAK each time the switch turns off and the diode turns on. Any inductance in series with
the diode will cause a voltage spike (VSPIKE = LPX × 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 (LPX) 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 VOUT + VF_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 CIN+ or CIN−
and GND can create voltage spikes that could appear on the VIN supply 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 (RS) is low enough the circuit will be underdamped
and will have a resonant frequency (typically the case). Depending on the size of LS the 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 VIN supply is replaced with a short to GND and the LM3532 +
Inductor is replaced with a current source (ΔIL).
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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 LS, RS, and CIN.
As an example, consider a 3.6V supply with 0.1Ω of series resistance connected to CIN through 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 (LS) 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.
'IL
ISUPPLY
RS
L
LS
SW
IN
+
LM3532
CIN
-
VIN
Supply
ISUPPLY
RS
LS
'IL
CIN
2
1.
RS
1
>
L S x C IN
4 x L S2
2.
f RESONANT =
3.
1
2S
LS x CIN
1
2S x 500 kHz x CIN
I SUPPLYRIPPLE | ' I L x
2
RS
§
·
1
¨2S x 500 kHz x LS ¸
¨
¸
x
x
S
500
kHz
C
2
IN
©
¹
2
Figure 45. Input RLC Network
40
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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
L
GND
Schottky
Diode
SW
OUT
COUT
Figure 46. Layout Example #1
CIN
GND
Schottky
Diode
IN
COUT
LM3532
OUT
SW
L
Figure 47. Layout Example #2
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REVISION HISTORY
Changes from Revision B (July 2012) to Revision C
Page
•
added "IFULL_SCALE = 20.2mA, Brightness Code = 0xFF" to 2.7V ≤ VIN ≤ 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
•
42
Page
Updated Output Configuration Register defaults: in col. 2 from "00" to "1X"; in col. 3 from "00" to "01". .......................... 28
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PACKAGE OPTION ADDENDUM
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3-Jun-2013
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
(2)
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
LM3532TME-40A/NOPB
ACTIVE
DSBGA
YFQ
16
250
Green (RoHS
& no Sb/Br)
SNAGCU
Level-1-260C-UNLIM
D34
LM3532TMX-40A/NOPB
ACTIVE
DSBGA
YFQ
16
3000
Green (RoHS
& no Sb/Br)
SNAGCU
Level-1-260C-UNLIM
D34
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
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In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 1
Samples
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
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
LM3532TME-40A/NOPB
DSBGA
YFQ
16
250
178.0
8.4
LM3532TMX-40A/NOPB
DSBGA
YFQ
16
3000
178.0
8.4
Pack Materials-Page 1
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
1.85
2.01
0.76
4.0
8.0
Q1
1.85
2.01
0.76
4.0
8.0
Q1
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
DSBGA
YFQ
LM3532TMX-40A/NOPB
DSBGA
YFQ
16
250
210.0
185.0
35.0
16
3000
210.0
185.0
35.0
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
NOTES:
A. All linear dimensions are in millimeters. Dimensioning and tolerancing per ASME Y14.5M-1994.
B. This drawing is subject to change without notice.
www.ti.com
12/12
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