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LM3530
SNVS606L – JUNE 2009 – REVISED DECEMBER 2014
LM3530 High-Efficiency White-LED Driver with Programmable Ambient Light Sensing
Capability and I2C-Compatible Interface
1 Features
3 Description
•
•
•
•
The LM3530 current mode boost converter supplies
the power and controls the current in up to 11 series
white LEDs. The 839-mA current limit and 2.7-V to
5.5-V input voltage range make the device a versatile
backlight power source ideal for operation in portable
applications.
1
•
•
•
•
•
•
•
•
Drives up to 11 LEDs in series
1000:1 Dimming Ratio
90% Efficient
Programmable Dual Ambient Light Sensor Inputs
with Internal ALS Voltage Setting Resistors
I2C Programmable Logarithmic or Linear
Brightness Control
External PWM Input for Simple Brightness
Adjustment
True Shutdown Isolation for LEDs and Ambient
Light Sensors
Internal Soft-Start Limits Inrush Current
Wide 2.7-V to 5.5-V Input Voltage Range
40-V and 25-V Overvoltage Protection Options
500-kHz Fixed Frequency Operation
839-mA Peak Current Limit
The LED current is adjustable from 0 mA to 29.5 mA
via an I2C-compatible interface. The 127 different
current steps and 8 different maximum LED current
levels give over 1000 programmable LED current
levels. Additionally, PWM brightness control is
possible through an external logic level input.
The device also features two Ambient Light Sensor
inputs. These are designed to monitor analog output
ambient light sensors and provide programmable
adjustment of the LED current with changes in
ambient light. Each ambient light sensor input has
independently programmable internal voltage setting
resistors which can be made high impedance to
reduce power during shutdown. The 500-kHz
switching frequency allows for high converter
efficiency over a wide output voltage range
accommodating from 2 to 11 series LEDs. Finally, the
support of Content Adjusted Backlighting maximizes
battery life while maintaining display image quality.
2 Applications
•
•
•
Smartphone LCD Backlighting
Personal Navigation LCD Backlighting
2 to 11 Series White-LED Backlit Display Power
Source
space
The LM3530 operates over the −40°C to 85°C
temperature range.
Device Information(1)
PART NUMBER
LM3530
PACKAGE
DSBGA (12)
BODY SIZE (MAX)
1.64 mm x 1.24 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Simplified Schematic
L
D1
Up to 40V
2.7V to 5.5V
C OUT
VLOGIC
10 k:
SW
IN
10 k:
10 k:
10 k:
C IN
LM3530
SCL
OVP
SDA
HWEN
INT
PWM
ILED
VIN
Ambient Light
Sensor
VIN
ALS1
ALS2
Ambient Light
Sensor
GND
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LM3530
SNVS606L – JUNE 2009 – REVISED DECEMBER 2014
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
I2C Device Options ................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
3
4
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
4
4
4
4
5
6
6
7
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics ..........................................
I2C-Compatible Timing Requirements (SCL, SDA) ..
Simple Interface Timing ............................................
Typical Characteristics ..............................................
Detailed Description ............................................ 11
8.1 Overview ................................................................. 11
8.2 Functional Block Diagram ....................................... 11
8.3
8.4
8.5
8.6
9
Feature Description.................................................
Device Functional Modes........................................
Programming ..........................................................
Register Maps .........................................................
12
26
27
28
Application and Implementation ........................ 34
9.1 Application Information............................................ 34
9.2 Typical Application ................................................. 34
10 Power Supply Recommendations ..................... 38
11 Layout................................................................... 38
11.1 Layout Guidelines ................................................. 38
11.2 Layout Example .................................................... 41
12 Device and Documentation Support ................. 43
12.1
12.2
12.3
12.4
12.5
Device Support ....................................................
Documentation Support ........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
43
43
43
43
43
13 Mechanical, Packaging, and Orderable
Information ........................................................... 43
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision K (March 2013) to Revision L
•
Added Device Information and ESD Ratings tables, Detailed Description, Application and Implementation, Power
Supply Recommendations, Layout, Device and Documentation Support and Mechanical, Packaging, and Orderable
Information sections; moved some curves to Application Curves section ............................................................................. 1
Changes from Revision J (March 2013) to Revision K
•
2
Page
Page
Changed layout of National Data Sheet to TI format ........................................................................................................... 34
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SNVS606L – JUNE 2009 – REVISED DECEMBER 2014
5 I2C Device Options
ORDERABLE NUMBER
I2C DEVICE OPTION
LM3530TME-40
0x38
LM3530TMX-40
0x38
LM3530UME-25A
0x36
LM3530UME-40
0x38
LM3530UME-40B
0x39
LM3530UMX-25A
0x36
LM3530UMX-40
0x38
LM3530UMX-40B
0x39
6 Pin Configuration and Functions
DSBGA (YFZ or YFQ) Package
12 Pins
Top View
A1
A2
A3
B1
B2
B3
C1
C2
C3
D1
D2
D3
Pin Functions
PIN
TYPE
DESCRIPTION
NUMBER
NAME
A1
SDA
I/O
Serial data connection for I2C-compatible interface.
A2
SCL
I
Serial data connection for I2C-compatible interface.
A3
SW
PWR
B1
PWM
I
External PWM brightness control input and simple enable input.
B2
INT
O
Logic interrupt output signaling the ALS zone has changed.
B3
GND
C1
ALS2
C2
C3
Inductor connection, diode anode connection, and drain connection for internal NFET. Connect
the inductor and diode as close as possible to SW to reduce parasitic inductance and capacitive
coupling to nearby traces.
Ground
I
Ambient light sensor input 2 with programmable internal pull-down resistor.
HWEN
I
Active high hardware enable (active low reset). pull this pin high to enable the LM3530.
IN
PWR
D1
ALS1
I
Ambient light sensor input 1 with programmable internal pulldown resistor.
D2
OVP
I
Output voltage sense connection for overvoltage sensing. Connect OVP to the positive terminal
of the output capacitor.
D3
ILED
PWR
Input voltage connection. Connect a 2.7-V to 5.5-V supply to IN and bypass to GND with a 2.2µF or greater ceramic capacitor.
Input terminal to internal current sink. The boost converter regulates ILED to 0.4 V.
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7 Specifications
7.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)
(1) (2) (3)
VIN to GND
MIN
MAX
–0.3
6
VSW, VOVP, VILED to GND
45
VSCL, VSDA, VALS1, VPWM, VINT, VHWEN to GND
6
VALS2 to GND
Internally limited
Junction temperature (TJ-MAX)
Storage temperature, Tstg
(3)
(4)
150
°C
150
°C
See (4)
Maximum lead temperature (soldering, 10s)
(2)
V
–0.3 V to VIN + 0.3 V
Continuous power dissipation
(1)
UNIT
–65
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
All voltages are with respect to the potential at the GND pin.
For detailed soldering specifications and information, please refer to Application Note 1112: DSBGA Wafer Level Chip Scale Package
(SNVA009).
7.2 ESD Ratings
V(ESD)
(1)
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
Electrostatic discharge
VALUE
UNIT
±2000
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
7.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
MIN
VIN to GND
NOM
MAX
2.7
5.5
0
40
Junction temperature (TJ) (1)
–40
125
Ambient temperature (TA) (2)
–40
85
VSW, VOVP, VILED, to GND
(1)
(2)
UNIT
V
°C
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 (RθJA), as given by the following equation: TA-MAX = TJ-MAX-OP – (RθJA × PD-MAX).
7.4 Thermal Information
DSBGA
THERMAL METRIC
(1)
YFQ
YFZ
UNIT
12 PINS
RθJA
(1)
(2)
4
Junction-to-ambient thermal resistance (2)
61.7
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
Junction-to-ambient thermal resistance (RθJA) 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/3 6µm
(1.5oz/1oz/1oz/1.5oz). Ambient temperature in simulation is 22°C in still air. Power dissipation is 1W. The value of RθJA of this product in
the DSBGA package could fall in a range as wide as 60ºC/W to 110ºC/W (if not wider), depending on PCB material, layout, and
environmental conditions. In applications where high maximum power dissipation exists special care must be paid to thermal dissipation
issues.
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7.5 Electrical Characteristics
Typical (TYP) limits are for TA = 25°C; minimum (MIN) and maximum (MAX) apply over the full operating ambient
temperature range (−40°C ≤ TA ≤ 85°C); VIN = 3.6 V, unless otherwise specified. (1) (2)
PARAMETER
TEST CONDITIONS
2.7 V ≥ VIN ≥ 5.5 V, Full-scale current = 19
mA, BRT Code = 0x7F, ALS Select Bit = 0,
I2C Enable = 1
ILED
Output current regulation
VREG_CS
Regulated current sink
headroom voltage
VHR
Current sink minimum
headroom voltage
ILED = 95% of nominal
RDSON
NMOS switch on resistance
ISW = 100 mA
ICL
NMOS switch current limit
2.7 V ≤ VIN ≤ 5.5 V
MIN
TYP
MAX
UNIT
17.11
18.6
20.08
mA
400
mV
200
mV
839
936
ON Threshold, 2.7 V ≤ VIN ≤ 5.5 40-V
V
version
40
41
42
25-V
version
23.6
24
24.6
450
500
VOVP
Output overvoltage
protection
fSW
Switching frequency
DMAX
Maximum duty cycle
DMIN
Minimum duty cycle
IQ
Quiescent current, device
not switching
VHWEN = VIN
490
IQ_SW
Switching supply current
ILED = 19 mA, VOUT = 36 V
1.35
ISHDN
Shutdown current
VHWEN = GND, 2.7 V ≥ VIN ≥ 5.5 V
ILED_MIN
Minimum LED current
Full-scale current = 19 mA setting
BRT = 0x01
VALS
Ambient light sensor
reference voltage
2.7 V ≥ VIN ≥ 5.5 V
Hysteresis
VHWEN
TSD
(3)
V
550
kHz
600
µA
94%
10%
1
mA
2
9.5
µA
µA
(3)
Logic thresholds - logic low
Logic thresholds - logic high
0.97
1
1.03
0
0.4
1.2
VIN
140
Hysteresis
(1)
(2)
mA
1
2.7 V ≤ VIN ≤ 5.5 V
Thermal shutdown
RALS1,
RALS2
Ω
0.25
739
V
°C
15
ALS input internal pull-down
2.7 V ≥ VIN ≥ 5.5 V
resistors
V
12.77
13.531
14.29
8.504
9.011
9.518
5.107
5.411
5.715
2.143
2.271
2.399
1.836
1.946
2.055
1.713
1.815
1.917
1.510
1.6
1.69
1.074
1.138
1.202
0.991
1.050
1.109
0.954
1.011
1.068
0.888
0.941
0.994
0.717
0.759
0.802
0.679
0.719
0.760
0.661
0.700
0.740
0.629
0.666
0.704
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 (typ.) numbers are not verified, but represent the most
likely norm.
The ALS voltage specification is the maximum trip threshold for the ALS zone boundary (Code 0xFF). Due to random offsets and the
mechanism for which the hysteresis voltage varies, it is recommended that only Codes 0x04 and above be used for Zone Boundary
Thresholds. See Zone Boundary Trip Points and Hysteresis and Minimum Zone Boundary Settings sections.
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Electrical Characteristics (continued)
Typical (TYP) limits are for TA = 25°C; minimum (MIN) and maximum (MAX) apply over the full operating ambient
temperature range (−40°C ≤ TA ≤ 85°C); VIN = 3.6 V, unless otherwise specified.(1)(2)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
V
LOGIC VOLTAGE SPECIFICATIONS (SCL, SDA, PWM, INT)
VIL
Input logic low
2.7 V ≤ VIN ≤ 5.5 V
0
0.54
VIH
Input logic high
2.7 V ≤ VIN ≤ 5.5 V
1.26
VIN
V
VOL
Output logic low (SDA, INT)
ILOAD = 3 mA
400
mV
7.6 I2C-Compatible Timing Requirements (SCL, SDA) (1)
MIN
NOM
MAX
UNIT
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
(1)
SCL and SDA must be glitch-free in order for proper brightness control to be realized.
7.7 Simple Interface Timing
MIN
NOM
MAX
tPWM_HIGH
Enable time, PWM pin must be held high
1.5
2
2.6
tPWM_LOW
Disable time, PWM pin must be held low
1.48
2
2.69
UNIT
ms
t1
SCL
t5
t4
SDIO
Data In
t2
SDIO
Data Out
t3
2
Figure 1. I C-Compatible Timing
t > tPWM_HIGH(MAX)
t < tPWM_HIGH(MIN)
t > tPWM_LOW(MAX)
t < tPWM_LOW(MIN)
Figure 2. Simple Enable/Disable Timing
6
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7.8 Typical Characteristics
VIN = 3.6 V, LEDs are OVSRWAC1R6 from OPTEK Technology, COUT = 1 µF, CIN = 1 µF, L = TDK VLF5012ST-100M1R0,
(RL = 0.24 Ω), ILED = 19 mA, TA = 25°C, unless otherwise specified.
IFULL_SCALE = 19 mA
Figure 3. LED Current vs VIN
Figure 4. Shutdown Current vs VIN
ALS Resistor Select Register = 0x44
TA = 85°C
Figure 5. Internal ALS Resistor vs VIN
TA = −40°C
ALS Resistor Select Register = 0x44
ALS Resistor Select Register = 0x44
Figure 6. Internal ALS Resistor vs VIN
VOUT Rising
Figure 7. Internal ALS Resistor vs VIN
Figure 8. Overvoltage Protection vs VIN
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Typical Characteristics (continued)
VIN = 3.6 V, LEDs are OVSRWAC1R6 from OPTEK Technology, COUT = 1 µF, CIN = 1 µF, L = TDK VLF5012ST-100M1R0,
(RL = 0.24 Ω), ILED = 19 mA, TA = 25°C, unless otherwise specified.
Figure 9. Max Duty Cycle vs VIN
Figure 10. NFET Switch On-Resistance vs VIN
Figure 11. Switching Frequency vs VIN
Figure 12. Simple Enable Time vs VIN
ILED Full Scale = 19 mA
Figure 13. Simple Disable Time vs VIN
8
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50% Duty Cycle
Figure 14. ILED vs FPWM
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Typical Characteristics (continued)
VIN = 3.6 V, LEDs are OVSRWAC1R6 from OPTEK Technology, COUT = 1 µF, CIN = 1 µF, L = TDK VLF5012ST-100M1R0,
(RL = 0.24 Ω), ILED = 19 mA, TA = 25°C, unless otherwise specified.
Channel 2: SDA (5V/div)
Channel 3: ILED (10mA/div)
1.024ms/Step Up And Down
Time Base (40ms/div)
Channel 2: SDA (5V/div)
Channel 3: ILED (10mA/div)
2.048ms/Step Up And Down
Figure 15. Ramp Rate (Exponential)
Channel 2: SDA (5V/div)
Channel 3: ILED (10mA/div)
4.096ms/Step Up And Down
Time Base (200ms/div)
Figure 16. Ramp Rate (Exponential)
Channel 2: SDA (5V/div)
Channel 3: ILED (10mA/div)
8.192ms/Step Up And Down
Time Base (1s/div)
Time Base (400ms/div)
Figure 18. Ramp Rate (Exponential)
Figure 17. Ramp Rate (Exponential)
Channel 2: SDA (5V/div)
Channel 3: ILED (10mA/div)
16.384ms/Step Up And Down
Time Base (100ms/div)
Channel 2: SDA (5V/div)
Channel 3: ILED (10mA/div)
32.768ms/Step Up And Down
Figure 19. Ramp Rate (Exponential)
Time Base (2s/div)
Figure 20. Ramp Rate (Exponential)
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Typical Characteristics (continued)
VIN = 3.6 V, LEDs are OVSRWAC1R6 from OPTEK Technology, COUT = 1 µF, CIN = 1 µF, L = TDK VLF5012ST-100M1R0,
(RL = 0.24 Ω), ILED = 19 mA, TA = 25°C, unless otherwise specified.
Channel 2: SDA (5V/div)
Channel 3: ILED (10mA/div)
65.538ms/Step Up And Down
Time Base (4s/div)
Channel 1: IIN (200mA/div)
Channel 3: VOUT (20V/div)
Channel 4 (10mA/div)
L = 22 µH
VIN = 3.6V
Figure 21. Ramp Rate (Exponential)
Channel 1: VIN (500mV/div)
Channel 2: VOUT (500mV/div)
Channel 3: ILED (500µA/div)
VIN From 3.6 V To 3.2 V
Figure 22. Start-up Plot
Time Base (400µs/div)
L = 22 µH
ILED = 19 mA
Figure 23. Line Step Response
Time Base (2ms/div)
Ramp Rate = 8µs/Step
ILED = 19mA
Channel 2: PWM (5V/div)
Channel 4: ILED (5mA/div)
DPWM From 30% To 70%
Time Base (2ms/div)
ILED Full Scale = 19 mA
FPWM = 5 kHz
Figure 24. ILED Response To Step Change In PWM Duty
Cycle
Closed Loop
L = 22 µH
The value for current limit given in the Electrical Characteristics is measured in an open loop test by forcing current into SW until the
current limit comparator threshold is reached. The typical curve for current limit is measured in closed loop using the typical application
circuit by increasing IOUT until the peak inductor current stops increasing. Closed loop data appears higher due to the delay between the
comparator trip point and the NFET turning off. This delay allows the closed loop inductor current to ramp higher after the trip point by
approximately 100 ns × VIN/L.
Figure 25. Current Limit vs VIN
10
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8 Detailed Description
8.1 Overview
The LM3530 utilizes an asynchronous step-up, current mode, PWM controller and regulated current sink to
provide an efficient and accurate LED current for white LED bias. The device powers a single series string of
LEDs with output voltages of up to 40 V and a peak inductor current of typically 839 mA. The input active voltage
range is from 2.7 V to 5.5 V.
8.2 Functional Block Diagram
IN
OVP
Boost Control
40V
Thermal
shutdown
400mV
SOFT START
SW
Light
Load
OVP
140C
ERROR
AMP
+
-
R
RZ
R
R
R
250m:
S
HWEN
R
Driver
CC
Osc/
Ramp
SCL
Over
Current
Protection
I2C/CONTROL
SDA
¦
GND
gm
INT
Zone Change
Flag
Current Control
Mapping Mode Select Bit
(0 = Exponental, 1 = Linear)
1bit
Dig Code
Active Zone
Target
Register
7 bits
1
Zone Targets X 5
BRT
Register
Note 1
7 bits
A
3 bits
ALS Input Select
DAC
7 bits
0
7 bits
7 bits
LED Ramp
Rate Control
Averager/
Discriminator
ALS Select
Ramp Rate
Increasing
3 bits
Ramp Rate
Decreasing
Zone Change
Flag
Full Scale Current
Select Bits
ALS2
8 bits
ALS1 Resistor
Select (4 Bits)
Zone Boundaries
X4
ALS2 Resistor
Select (4 Bits)
PWM Polarity Bit
(0 = active high, 1 =
active low)
I FS
ILED
( 5 mA - 30 mA )
ALS1
ADC
CODE
Full Scale
Current
Note 3
EN_PWM bit
LPF
Note 2
D PWM
PWM
Note 1:
ACODE Is a Scaler between 0 and 1 based on the Brightness Data or Zone Target Data Depending on the ALS Select Bit
Note 2:
DPWM Is a Scaler between 0 and 1 and corresponds to the duty cycle of the PWM input signal
Note 3: For EN_PWM bit = 1
ILED = IFS x ACODE x DPWM
For EN_PWM bit = 0
ILED = IFS x ACODE
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8.3 Feature Description
8.3.1 Start-Up
An internal soft-start prevents large inrush currents during start-up that can cause excessive current spikes at the
input. For the typical application circuit (using a 10-µH inductor, a 2.2-µF input capacitor, and a 1-µF output
capacitor) the average input current during start-up ramps from 0 to 300 mA in 3 ms. See Figure 22 in the
Typical Characteristics.
8.3.2 Light Load Operation
The LM3530 boost converter operates in three modes: continuous conduction, discontinuous conduction, and
skip mode. Under heavy loads when the inductor current does not reach zero before the end of the switching
period, the device switches at a constant frequency (500 kHz typical). As the output current decreases and the
inductor current reaches zero before the end of the switching period, the device operates in discontinuous
conduction. At very light loads the LM3530 will enter skip mode operation causing the switching period to
lengthen and the device to only switch as required to maintain regulation at the output. Light load operation
provides for improved efficiency at lighter LED currents compared to continuous and discontinuous conduction.
This is due to the pulsed frequency operation resulting in decreased switching losses in the boost converter.
8.3.3 Ambient Light Sensor
The LM3530 incorporates a dual input Ambient Light Sensing interface (ALS1 and ALS2) which translates an
analog output ambient light sensor to a user-specified brightness level. The ambient light sensing circuit has 4
programmable boundaries (ZB0 – ZB3) which define 5 ambient brightness zones. Each ambient brightness zone
corresponds to a programmable brightness threshold (Z0T – Z4T). The ALS interface is programmable to accept
the ambient light information from either the highest voltage of ALS1 or ALS2, the average voltage of ALS1 or
ALS2, or selectable from either ALS1 or ALS2.
Furthermore, each ambient light sensing input (ALS1 or ALS2) features 15 internal software selectable voltage
setting resistors. This allows the LM3530 the capability of interfacing with a wide selection of ambient light
sensors. Additionally, the ALS inputs can be configured as high impedance, thus providing for a true shutdown
during low power modes. The ALS resistors are selectable through the ALS Resistor Select Register (see
Table 9). Figure 26 shows a functional block diagram of the ambient light sensor input. VSNS represents the
active input as described in Table 6 bits [6:5].
Vdd
ALS Path Functional Diagram
Vsns
VOUT
Zone
Averager
(LPF)
0
Zline
1
Zline
2
Zline
3
Zline
Input
Light
Zone
Definiton
Registers
A/D
Discriminator
7 bits
ALS Resistor
Select Register
8 bits
ALSRS
User Selectable w/
Typical Defaults
Light output
Targets for
Each of 5
Ambient
Light zones
Z0 target light
7 bits
Z1 target light
Z 2 target light
Z 3 target light
Z 4 target light
0
1
2
3
4
7 bits
Brightness
User Selectable w/
Typical Defaults
1
0
7 bits
Ramp
control
7 bits
LED Driver
3 bits
ALS Select
Ramp Rate
Selection
Figure 26. Ambient Light Sensor Functional Block Diagram
12
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Feature Description (continued)
8.3.4 ALS Operation
The ambient light sensor input has a 0-V to 1-V operational input voltage range. LM3530 Typical Application
shows the LM3530 with dual ambient light sensors (AVAGO, APDS-9005) and the internal ALS Resistor Select
Register set to 0x44 (2.27 kΩ). This circuit converts 0 to 1000 LUX light into approximately a 0-mV to 850-mV
linear output voltage. The voltage at the active ambient light sensor input (ALS1 or ALS2) is compared against
the 8 bit values programmed into the Zone Boundary Registers (ZB0-ZB3). When the ambient light sensor output
crosses one of the ZB0 – ZB3 programmed thresholds the internal ALS circuitry will smoothly transition the LED
current to the new 7 bit brightness level as programmed into the appropriate Zone Target Register (Z0T – Z4T)
(see Figure 27).
The ALS Configuration Register bits [6:5] programs which input is the active input, bits [4:3] control the on/off
state of the ALS circuitry, and bits [2:0] control the ALS input averaging time. Additionally, the ALS Information
Register is a read-only register which contains a flag (bit 3) which is set each time the active ALS input changes
to a new zone. This flag is reset when the register is read back. Bits [2:0] of this register contain the current
active zone information.
Vals_ref =
1V
Full
Scale
Zone 4
ZB3
ZB1
Zone 2
LED Current
Vsense
Zone 3
ZB2
Zone 1
ZB0
Zone 0
Z0T
Ambient Light (lux)
Z1T
Z2T
Z3T
Z4T
LED Driver Input Code (0-127)
Figure 27. Ambient Light Input To Backlight Mapping
8.3.5 ALS Averaging Time
The ALS Averaging Time is the time over which the Averager block collects samples from the A/D converter and
then averages them to pass to the discriminator block (see Figure 26). Ambient light sensor samples are
averaged and then further processed by the discriminator block to provide rejection of noise and transient
signals. The averager is configurable with 8 different averaging times to provide varying amounts of noise and
transient rejection (see Table 5). The discriminator block algorithm has a maximum latency of two averaging
cycles; therefore, the averaging time selection determines the amount of delay that will exist between a steadystate change in the ambient light conditions and the associated change of the backlight illumination. For
example, the A/D converter samples the ALS inputs at 16 kHz. If the averaging time is set to 1024 ms then the
Averager will send the updated zone information to the discriminator every 1024 ms. This zone information
contains the average of 16384 samples (1024 ms × 16 kHz). Due to the latency of 2 averaging cycles, the LED
current will not change until there has been a steady-state change in the ambient light for at least 2 averaging
periods.
8.3.5.1 Averager Operation
The magnitude and direction (either increasing or decreasing) of the Averager output is used to determine
whether the LM3530 should change brightness zones. The Averager block functions as follows:
1. First, the Averager always begins with a Zone 0 reading stored at start-up. If the main display LEDs are
active before the ALS block is enabled, it is recommended that the ALS Enable 1 bit is set to '1' at least 3
averaging periods before the ALS Enable 2 bit is set.
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Feature Description (continued)
2. The Averager will always round down to the lower zone in the event of a non-integer zone average. For
example, if during an averaging period the ALS input transitions between zones 1 and 2 resulting in an
averager output of 1.75, then the averager output will round down to 1 (see Figure 28).
3. The two most current averaging samples are used to make zone change decisions.
4. To make a zone change, data from three averaging cycles are needed. (Starting Value, First Transition,
Second Transition or Rest).
5. To Increase the brightness zone, the Averager output must have increased for at least 2 averaging periods
or increased and remained at the new level for at least two averaging periods ('+' to '+' or '+' to 'Rest' in
Figure 29).
6. To decrease the brightness zone, the Averager output must have decreased for at least 2 averaging periods
or decreased and remained at the new level for at least two averaging periods ('-' to '-' or '-' to 'Rest' in
Figure 29).
In the case of two consecutive increases or decreases in the Averager output, the LM3530 will transition to zone
equal to the last averager output (Figure 29).
Using the diagram for the ALS block (Figure 26), the flow of information is shown in (Figure 30). This starts with
the ALS input into the A/D, into the Averager, and then into the Discriminator. Each state filters the previous
output to help prevent unwanted zone to zone transitions.
When using the ALS averaging function, it is important to remember that the averaging cycle is free running and
is not synchronized with changing ambient lighting conditions. Due to the nature of the averager round down, an
increase in brightness can take between 2 and 3 averaging cycles to change zones, while a decrease in
brightness can take between 1 and 2 averaging cycles. See Table 6 for a list of possible Averager periods.
Figure 31 shows an example of how the perceived brightness change time can vary.
Zone 4
Zone 3
Averager Output
Zone 2
µ5¶= Rest, µ+¶= Increase, µ-µ= Decrease
Zone 1
Zone 4
Zone 0
Zone
Average
Averager
Output
Zone 3
1.0
1.75
3.5
4.0
2.25
2.25
1.5
1
1
3
4
2
2
1
Zone 2
Zone 1
Zone 0
R
Figure 28. Averager Calculation
Brightness
Zone
+
0
R
0
+
1
+
1
+
3
R
4
R
4
4
Zone 4
Zone 3
Zone 2
Zone 1
Zone 0
R
Brightness
Zone
4
R
4
3
3
1
R
0
R
0
0
Zone 4
Zone 3
Zone 2
Zone 1
Zone 0
R
Brightness
Zone
+
0
+
0
4
+
4
4
4
R
1
1
Figure 29. Brightness Zone Change Examples
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1 Ave
Period
1 Ave
Period
Zone4
Zone3
ALS Input
Zone2
Zone4
Zone1
Zone3
Zone0
Averager
Output
Zone2
1
1
3
4
2
2
Zone1
1
Zone0
tBRGT-CHANGE =
2.75 Average
Time
Averager Output
Zone4
tBRGT-CHANGE =
1.75 Average Time
Zone3
Zone2
Figure 30. Ambient Light Input To Backlight
Transition
Zone1
Zone0
LED Brightness
Zone
Zone4
Zone3
Zone2
Zone1
Zone0
Figure 31. Perceived Brightness Change Time
8.3.6
Zone Boundary Settings
Registers 0x60, 0x61, 0x62, and 0x63 set the 4 zone boundaries (thresholds) for the ALS inputs. These 4 zone
boundaries create 5 brightness zones which map over to 5 separate brightness zone targets (see Figure 27).
Each 8-bit zone boundary register can set a threshold from typically 0 to 1 V with linear step sizes of
approximately 1/255 = 3.92 mV. Additionally, each zone boundary has built in hysteresis which can be either
lower or higher then the programmed Zone Boundary depending on the last direction (either up or down) of the
ALS input voltage.
8.3.7
Zone Boundary Trip Points and Hysteresis
For each zone boundary setting, the trip point will vary above or below the nominal set point depending on the
direction (either up or down) of the ALS input voltage. This is designed to keep the ALS input from oscillating
back and forth between zones in the event that the ALS voltage is residing near to the programmed zone
boundary threshold. The Zone Boundary Hysteresis will follow these 2 rules:
1. If the last zone transition was from low to high, then the trip point (VTRIP) will be VZONE_BOUNDARY - VHYST/2,
where VZONE_BOUNDARY is the zone boundary set point as programmed into the Zone Boundary registers, and
VHYST is typically 7 mV.
2. If the last zone transition was from high to low then the trip point (VTRIP) will be VZONE_BOUNDARY + VHYST/2.
Figure 32 details how the LM3530 ALS Input Zone Boundary Thresholds vary depending on the direction of the
ALS input voltage.
Referring to Figure 32, each numbered trip point shown is determined from the direction of the previous ALS
zone transition.
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1V
Zone 4
VHYST
2
VZB3 +
Zone Boundary 3
VZB3 -
VHYST
2
Zone 3
ALS Input Voltage
#1
VHYST
VZB2 + 2
Zone Boundary 2
VZB2 -
VHYST
2
#8
#3
Zone 2
#2
VHYST
VZB1 +
2
Zone Boundary 1
VZB1 -
VHYST
2
#4
#7
Zone 1
#5
#6
VHYST
VZB0 +
2
Zone Boundary 0
VZB0 -
VHYST
2
Zone 0
Figure 32. Zone Boundaries With Hysteresis
8.3.8
Minimum Zone Boundary Settings
The actual minimum zone boundary setting is code 0x03. Codes of 0x00, 0x01, and 0x02 are all mapped to code
0x03. Table 1 shows the Zone Boundary codes 0x00 through 0x04, the typical thresholds, and the high and low
hysteresis values. The remapping of codes 0x00 - 0x02 plus the additional 4mV of offset voltage is necessary to
prevent random offsets and noise on the ALS inputs from creating threshold levels that are below GND. This
essentially guarantees that any Zone Boundary threshold selected is achievable with positive ALS voltages.
Table 1. Ideal Zone Boundary Settings with Hysteresis (Lower 5 Codes)
16
ZONE BOUNDARY CODE
TYPICAL ZONE BOUNDARY
THRESHOLD (mV)
TYPICAL THRESHOLD +
HYSTERESIS (mV)
TYPICAL THRESHOLD HYSTERESIS (mV)
0x00
15.8
19.3
12.3
0x01
15.8
19.3
12.3
0x02
15.8
19.3
12.3
0x03
15.8
19.3
12.3
0x04
19.7
23.2
16.2
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8.3.9 LED Current Control
The LED current is is a function of the Full Scale Current, the Brightness Code, and the PWM input duty cycle.
The Brightness Code can either come from the BRT Register (0xA0) in I2C-Compatible Current Control, or from
the ALS Zone Target Registers (Address 0x70-0x74) in Ambient Light Current Control. Figure 33 shows the
current control block diagram.
VOUT
Mapping Mode Select Bit
(0 = Exponental, 1 = Linear)
Active Zone
Target
Register
BRT
Register
Dig Code
7 bits
1
1bit
7 bits
LED Ramp
Rate Control
DAC
7 bits
0
7 bits
Note 1
3 bits
ALS Select
Ramp Rate
Increasing
Full Scale Current Select Bits 3 bits
A CODE
3 bits
Ramp Rate
Decreasing
IFS
( 5 mA - 30 mA)
Full Scale
Current
LED Driver
I LED
PWM Polarity Bit
(0 = active high,
1 = active low)
EN_PWM bit
Note 3
LPF
PWM
Note 2
DPWM
Note 1: ACODE Is a Scaler between 0 and 1 based on the Brightness Data or Zone Target Data Depending on the ALS Select Bit
Note 2: DPWM Is a Scaler between 0 and 1 and corresponds to the duty cycle of the PWM input signal
Note 3: For EN_PWM bit = 1
ILED = IFS x ACODE x DPWM
For EN_PWM bit = 0
ILED = IFS x ACODE
Figure 33. Current Control Block Diagram
8.3.10 Exponential or Linear Brightness Mapping Modes
With bit [1] of the General Configuration Register set to 0 (default) exponential mapping is selected and the code
in the Brightness Control Register corresponds to the Full-Scale LED current percentages in Table 2 and
Figure 34. With bit [1] set to 1 linear mapping is selected and the code in the Brightness Control Register
corresponds to the Full-Scale LED current percentages in Table 3 and Figure 35.
8.3.11 PWM Input Polarity
Bit [6] of the General Configuration Register controls the PWM input polarity. Setting this bit to 0 (default) selects
positive polarity and makes the LED current (with PWM mode enabled) a function of the positive duty cycle at
PWM. With this bit set to ‘0’ the LED current (with PWM mode enabled) becomes a function of the negative duty
cycle at PWM.
The PWM input is a logic level input with a frequency range of 400 Hz to 50 kHz. Internal filtering of the PWM
input signal converts the duty cycle information to an average (analog) control signal which directly controls the
LED current.
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Example: PWM + I2C-Compatible Current Control:
As an example, assume the the General Configuration Register is loaded with (0x2D). From Table 5, this sets up
the LM3530 with:
Simple Enable OFF (bit 7 = 0)
Positive PWM Polarity (bit 6 = 0)
PWM Enabled (bit 5 = 1)
Full-Scale Current set at 15.5 mA (bits [4:2] = 100)
Brightness Mapping set for Exponential (bit 1 = 0)
Device Enabled via I2C (bit 0 = 1)
Next, the Brightness Control Register is loaded with 0x73. This sets the LED current to 51.406% of full scale (see
Equation 1). Finally, the PWM input is driven with a 0-V to 2-V pulse waveform at 70% duty cycle. The LED
current under these conditions will be:
ILED = ILED _ FS x BRT x D = 15. 5 mA x 51. 4% x 70% | 5. 58 mA.
where
•
BRT is the percentage of ILED_FS as set in the Brightness Control Register
(1)
8.3.12 I2C-Compatible Current Control Only
I2C-Compatible Control is enabled by writing a '1' to the I2C Device Enable bit (bit [0] of the General
Configuration Register), a '0' to the Simple Enable bit (bit 7), and a '0' to the PWM Enable bit (bit 5). With bit 5 =
0, the duty cycle information at the PWM input is not used in setting the LED current.
In this mode the LED current is a function of the Full-Scale LED current bits (bits [4:2] of the General
Configuration Register) and the code in the Brightness Control Register. The LED current mapping for the
Brightness Control Register can be linear or exponential depending on bit [1] in the General Configuration
Register (see Exponential or Linear Brightness Mapping Modes section). Using I2C-Compatible Control Only, the
Full-Scale LED Current bits and the Brightness Control Register code provides nearly 1016 possible current
levels selectable over the I2C-compatible interface.
Example: I2C-Compatible Current Control Only:
As an example, assume the General Configuration Register is loaded with 0x15. From Table 5 this sets up the
LM3530 with:
Simple Enable OFF (bit 7 = 0)
Positive PWM Polarity (bit 6 = 0)
PWM Disabled (bit 5 = 0)
Full-Scale Current set at 22.5mA (bits [4:2] = 101)
Brightness Mapping set for Exponential (bit 1 = 0)
Device Enabled via I2C (bit 0 = 1)
The Brightness Control Register is then loaded with 0x72 (48.438% of full-scale current from Equation 2). The
LED current with this configuration becomes:
ILED = ILED _ FS x BRT = 22 . 5 mA x 0.48438 | 10.9 mA.
where
•
BRT is the % of ILED_FS as set in the Brightness Control Register.
(2)
Next, the brightness mapping is set to linear mapping mode (bit [1] in General Configuration Register set to 1).
Using the same Full-Scale current settings and Brightness Control Register settings as before, the LED current
becomes:
ILED = ILED _ FS x BRT = 22 . 5 mA x 0.8976 | 20.2 mA.
(3)
Which is higher now since the code in the Brightness Control Register (0x72) corresponds to 89.76% of FullScale LED Current due to the different mapping mode given in Figure 34.
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LED CURRENT (% of ILED_MAX SETTING)
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100
10
1
0.1
0.01
1
8
15
22
29
36 43
50 57
64
71
78
85
92 99
106 113 120 127
CODE (DECMIL)
Figure 34. Exponential Brightness Mapping
Table 2. ILED vs. Brightness Register Data (Exponential Mapping)
BRT DATA
(HEX)
% FULL-SCALE
CURRENT
BRT DATA (HEX)
% OF FULLSCALE
CURRENT
BRT DATA
(HEX)
% OF FULLSCALE
CURRENT
BRT
DATA
(HEX)
% OF FULLSCALE
CURRENT
0x00
0.00%
0x20
0.500%
0x40
2.953%
0x60
17.813%
0x01
0.080%
0x21
0.523%
0x41
3.125%
0x61
18.750%
0x02
0.086%
0x22
0.555%
0x42
3.336%
0x62
19.922%
0x03
0.094%
0x23
0.586%
0x43
3.500%
0x63
20.859%
0x04
0.102%
0x24
0.617%
0x44
3.719%
0x64
22.266%
0x05
0.109%
0x25
0.656%
0x45
3.906%
0x65
23.438%
0x06
0.117%
0x26
0.695%
0x46
4.141%
0x66
24.844%
0x07
0.125%
0x27
0.734%
0x47
4.375%
0x67
26.250%
0x08
0.133%
0x28
0.773%
0x48
4.648%
0x68
27.656%
0x09
0.141%
0x29
0.820%
0x49
4.922%
0x69
29.297%
0x0A
0.148%
0x2A
0.867%
0x4A
5.195%
0x6A
31.172%
0x0B
0.156%
0x2B
0.914%
0x4B
5.469%
0x6B
32.813%
0x0C
0.164%
0x2C
0.969%
0x4C
5.781%
0x6C
34.453%
0x0D
0.172%
0x2D
1.031%
0x4D
6.125%
0x6D
35.547%
0x0E
0.180%
0x2E
1.078%
0x4E
6.484%
0x6E
38.828%
0x0F
0.188%
0x2F
1.148%
0x4F
6.875%
0x6F
41.016%
0x10
0.203%
0x30
1.219%
0x50
7.266%
0x70
43.203%
0x11
0.211%
0x31
1.281%
0x51
7.656%
0x71
45.938%
0x12
0.227%
0x32
1.359%
0x52
8.047%
0x72
48.438%
0x13
0.242%
0x33
1.430%
0x53
8.594%
0x73
51.406%
0x14
0.250%
0x34
1.523%
0x54
9.063%
0x74
54.141%
0x15
0.266%
0x35
1.594%
0x55
9.609%
0x75
57.031%
0x16
0.281%
0x36
1.688%
0x56
10.078%
0x76
60.703%
0x17
0.297%
0x37
1.781%
0x57
10.781%
0x77
63.984%
0x18
0.320%
0x38
1.898%
0x58
11.250%
0x78
67.813%
0x19
0.336%
0x39
2.016%
0x59
11.953%
0x79
71.875%
0x1A
0.352%
0x3A
2.109%
0x5A
12.656%
0x7A
75.781%
0x1B
0.375%
0x3B
2.250%
0x5B
13.359%
0x7B
79.688%
0x1C
0.398%
0x3C
2.367%
0x5C
14.219%
0x7C
84.375%
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Table 2. ILED vs. Brightness Register Data (Exponential Mapping) (continued)
% FULL-SCALE
CURRENT
BRT DATA (HEX)
% OF FULLSCALE
CURRENT
BRT DATA
(HEX)
% OF FULLSCALE
CURRENT
BRT
DATA
(HEX)
% OF FULLSCALE
CURRENT
0x1D
0.422%
0x3D
2.508%
0x5D
15.000%
0x7D
89.844%
0x1E
0.445%
0x3E
2.648%
0x5E
15.859%
0x7E
94.531%
0x1F
0.469%
0x3F
2.789%
0x5F
16.875%
0x7F
100.00%
LED CURRENT (% of ILED_MAX SETTING)
BRT DATA
(HEX)
100
90
80
70
60
50
40
30
20
10
0
1
8
15
22
29
36 43
50 57
64
71
78
85
92 99
106 113 120 127
CODE (DECMIL)
Figure 35. Linear Brightness Mapping
Table 3. ILED vs. Brightness Register Data (Linear Mapping)
20
BRT DATA
(HEX)
% FULLSCALE
CURREN
T
(LINEAR)
BRT DATA
(HEX)
% OF FULLSCALE
CURRENT
(LINEAR)
BRT DATA
(HEX)
% OF
FULLSCALE
CURRE
NT
(LINEA
R)
BRT DATA (HEX)
% OF FULL-SCALE
CURRENT (LINEAR)
0x00
0.00%
0x20
25.79%
0x40
50.78%
0x60
75.78%
0x01
1.57%
0x21
26.57%
0x41
51.57%
0x61
76.56%
0x02
2.35%
0x22
27.35%
0x42
52.35%
0x62
77.35%
0x03
3.13%
0x23
28.13%
0x43
53.13%
0x63
78.13%
0x04
3.91%
0x24
28.91%
0x44
53.91%
0x64
78.91%
0x05
4.69%
0x25
29.69%
0x45
54.69%
0x65
79.69%
0x06
5.48%
0x26
30.47%
0x46
55.47%
0x66
80.47%
0x07
6.26%
0x27
31.25%
0x47
56.25%
0x67
81.25%
0x08
7.04%
0x28
32.04%
0x48
57.03%
0x68
82.03%
0x09
7.82%
0x29
32.82%
0x49
57.82%
0x69
82.81%
0x0A
8.60%
0x2A
33.60%
0x4A
58.60%
0x6A
83.59%
0x0B
9.38%
0x2B
34.38%
0x4B
59.38%
0x6B
84.38%
0x0C
10.16%
0x2C
35.16%
0x4C
60.16%
0x6C
85.16%
0x0D
10.94%
0x2D
35.94%
0x4D
60.94%
0x6D
85.94%
0x0E
11.72%
0x2E
36.72%
0x4E
61.72%
0x6E
86.72%
0x0F
12.51%
0x2F
37.50%
0x4F
62.50%
0x6F
87.50%
0x10
13.29%
0x30
38.29%
0x50
63.28%
0x70
88.28%
0x11
14.07%
0x31
39.07%
0x51
64.06%
0x71
89.06%
0x12
14.85%
0x32
39.85%
0x52
64.85%
0x72
89.84%
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Table 3. ILED vs. Brightness Register Data (Linear Mapping) (continued)
BRT DATA
(HEX)
% FULLSCALE
CURREN
T
(LINEAR)
BRT DATA
(HEX)
% OF FULLSCALE
CURRENT
(LINEAR)
BRT DATA
(HEX)
% OF
FULLSCALE
CURRE
NT
(LINEA
R)
BRT DATA (HEX)
% OF FULL-SCALE
CURRENT (LINEAR)
0x13
15.63%
0x33
40.63%
0x53
65.63%
0x73
90.63%
0x14
16.41%
0x34
41.41%
0x54
66.41%
0x74
91.41%
0x15
17.19%
0x35
42.19%
0x55
67.19%
0x75
92.19%
0x16
17.97%
0x36
42.97%
0x56
67.97%
0x76
92.97%
0x17
18.76%
0x37
43.75%
0x57
68.75%
0x77
93.75%
0x18
19.54%
0x38
44.53%
0x58
69.53%
0x78
94.53%
0x19
20.32%
0x39
45.32%
0x59
70.39%
0x79
95.31%
0x1A
21.10%
0x3A
46.10%
0x5A
71.10%
0x7A
96.09%
0x1B
21.88%
0x3B
46.88%
0x5B
71.88%
0x7B
96.88%
0x1C
22.66%
0x3C
47.66%
0x5C
72.66%
0x7C
97.66%
0x1D
23.44%
0x3D
48.44%
0x5D
73.44%
0x7D
98.44%
0x1E
24.22%
0x3E
49.22%
0x5E
74.22%
0x7E
99.22%
0x1F
25.00%
0x3F
50.00%
0x5F
75.00%
0x7F
100.00%
NOTE
When determining the LED current from (Table 2 and Table 3 ) there is a typical offset of
113 µA with a ±300-µA variation that must be added to the calculated value for codes
0x0A and below. For example, in linear mode with IFULL_SCALE = 19 mA and brightness
code 0x09 chosen, the nominal current setting is 0.0782 × 19 mA = 1.4858 mA. Adding in
the 113-µA typical offset gives 1.4858 mA + 0.113 mA = 1.5988 mA. With the typical
±300-µA range, the high and low currents can be ILOW = 1.2988 mA, IHIGH = 1.8988 mA.
For exponential mode with codes 0x0A and below, this offset and variation error gets
divided down by 10 (11.3 µA offset with ±30-µA typical range).
8.3.13 Simple Enable Disable With PWM Current Control
With bits [7 and 5] of the General Configuration Register set to ‘1’ the PWM input is enabled as a simple
enable/disable. The simple enable/disable feature operates as described in Figure 36. In this mode, when the
PWM input is held high (PWM Polarity bit = 0) for > 2 ms the LM3530 will turn on the LED current at the
programmed Full-Scale Current × % of Full-Scale Current as set by the code in the Brightness Control Register.
When the PWM input is held low for > 2 ms the device will shut down. With the PWM Polarity bit = 1 the PWM
input is configured for active low operation. In this configuration holding PWM low for > 2 ms will turn on the
device at the programmed Full-Scale Current × % of Full-Scale Current as set by the code in the Brightness
Control Register. Likewise, holding PWM high for > 2 ms will put the device in shutdown.
Driving the PWM input with a pulsed waveform at a variable duty cycle is also possible in simple enable/Disable
mode, so long as the low pulse width is < 2 ms. When a PWM signal is used in this mode the input duty cycle
information is internally filtered, and an analog voltage is used to control the LED current. This type of PWM
control (PWM to Analog current control) prevents large voltage excursions across the output capacitor that can
result in audible noise. Simple Enable/Disable mode can be useful since the default bit setting for the General
Configuration Register is 0xCC (Simple Enable bit = 1, PWM Enable = 1, and Full-Scale Current = 19mA).
Additionally, the default Brightness Register setting is 0x7F (100% of Full-Scale current). This gives the LM3530
the ability to turn on after power up (or after reset) without having to do any writes to the I2C-compatible bus.
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t > tPWM_HIGH(MAX)
t < tPWM_HIGH(MIN)
t > tPWM_LOW(MAX)
t < tPWM_LOW(MIN)
Figure 36. Simple Enable/Disable Timing
Example: Simple Enable Disable with PWM Current Control):
As an example, assume that the HWEN input is toggled low then high. This resets the LM3530 and sets all the
registers to their default value. When the PWM input is then pulled high for > 2 ms the LED current becomes:
ILED = ILED _ FS x BRT x D = 19 mA x 1.00 x 100 % | 19 mA.
where
•
BRT is the % of ILED_FS as set in the Brightness Control Register.
(4)
If then the PWM input is fed with a 5-kHz pulsed waveform at 40% duty cycle the LED current becomes:
ILED = ILED _ FS x BRT x D = 19 mA x 1.00 x 0.4 | 7.6 mA.
(5)
Then, if the Brightness Control Register is loaded with 0x55 (9.6% of Full-Scale Current) the LED current
becomes:
ILED = ILED _ FS x BRT x D = 19 mA x 9.65 x 0.4 | 0.73 mA.
(6)
8.3.14 Ambient Light Current Control
With bits [4:3] of the ALS Configuration Register both set to 1, the LM3530 is configured for Ambient Light
Current Control. In this mode the ambient light sensing inputs (ALS1, and/or ALS2) monitor the outputs of analog
output ambient light sensing photo diodes and adjust the LED current depending on the ambient light. The
ambient light sensing circuit has 4 configurable Ambient Light Boundaries (ZB0 – ZB3) programmed through the
four (8-bit) Zone Boundary Registers. These zone boundaries define 5 ambient brightness zones (Figure 27).
Each zone corresponds to a programmable brightness setting which is programmable through the 5 Zone Target
Registers (Z0T – Z4T). When the ALS1, and/or ALS2 input (depending on the bit settings of the ALS Input Select
bits) detects that the ambient light has crossed to a new zone (as defined by one of the Zone Boundary
Registers) the LED current becomes a function of the Brightness Code loaded in the Zone Target Register which
corresponds to the new ambient light brightness zone.
On start-up the 4 Zone Boundary Registers are pre-loaded with 0x33 (51d), 0x66 (102d), 0x99 (153d), and 0xCC
(204d). Each ALS input has a 1-V active input voltage range with a 4mV offset voltage which makes the default
Zone Boundaries set at:
Zone Boundary 0 = 1V × 51/255 + 4 mV = 204 mV
Zone Boundary 1 = 1V × 102/255 + 4 mV = 404 mV
Zone Boundary 2 = 1V × 153/255 + 4 mV = 604 mV
Zone Boundary 3 = 1V × 204/255 + 4 mV = 804 mV
These Zone Boundary Registers are all 8-bit (readable and writable) registers. The first zone (Z0) is defined
between 0 and 204 mV, the Z1 default is defined between 204 mV and 404 mV, the Z2 default is defined
between 404 mV and 604 mV, the Z3 default is defined between 604 mV and 804 mV, and the Z4 default is
defined between 804 mV and 1.004 V. The default settings for the 5 Zone Target Registers are 0x19, 0x33,
0x4C, 0x66, and 0x7F. This corresponds to LED brightness settings of 0.336%, 1.43%, 5.781%, 24.844%, and
100% of full-scale current respectively (assuming exponential backlight mapping).
Example: Ambient Light Control Current:
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As an example, assume that the APDS-9005 is used as the ambient light sensing photo diode with its output
connected to the ALS1 input. The ALS Resistor Select Register is loaded with 0x04 which configures the ALS1
input for a 2.27-kΩ internal pull-down resistor (see Table 9). The APDS-9005 has a typical 400nA/LUX response.
With a 2.27-kΩ resistor the sensor output would see a 0-mV to 908-mV swing with a 0 to 1000 LUX change in
ambient light. Next, the ALS Configuration Register is programmed with 0x3C. From Table 6, this configures the
LM3530’s ambient light sensing interface for:
ALS1 as the active ALS input (bits [6:5] = 01)
Ambient Light Current Control Enabled (bit 4 = 1)
ALS circuitry Enabled (bit 3 = 1)
Sets the ALS Averaging Time to 512 ms (bits [2:0] = 100)
Next, the General Configuration Register is programmed with 0x19 which sets the Full-Scale Current to 26 mA,
selects Exponential Brightness Mapping, and enables the device via the I2C-compatible interface.
Now assume that the APDS-9005 ambient light sensor detects a 100 LUX ambient light at its input. This forces
the ambient light sensors output (and the ALS1 input) to 87.5mV corresponding to Zone 0. Since Zone 0 points
to the brightness code programmed in Zone Target Register 0 (loaded with code 0x19), the LED current
becomes:
ILED = ILED_FS u ZoneTarget0 = 26 mA u 0.336% | 87 PA.
(7)
Where the code in Zone Target Register 0 points to the % of ILED_FS as given by Table 2 or Table 3,
depending on whether Exponential or Linear Mapping are selected.
Next, assume that the ambient light changes to 500 LUX (corresponding to an ALS1 voltage of 454 mV). This
moves the ambient light into Zone 2 which corresponds to Zone Target Register 2 (loaded with code 0x4C) the
LED current then becomes:
ILED = ILED _ FS x ZoneTarget2 = 26 mA x 5.781% | 1.5 mA.
(8)
8.3.15 Ambient Light Current Control + PWM
The Ambient Light Current Control can also be a function of the PWM input duty cycle. Assume the LM3530 is
configured as described in the above Ambient Light Current Control example, but this time the Enable PWM bit
set to ‘1’ (General Configuration Register bit [5]).
Example: Ambient Light Current Control + PWM
In this example, the APDS-9005 detects that the ambient light has changed to 1 kLUX. The voltage at ALS1 is
now around 908 mV, and the ambient light falls within Zone 5. This causes the LED brightness to be a function
of Zone Target Register 5 (loaded with 0x7F). Now assume the PWM input is also driven with a 50% duty cycle
pulsed waveform. The LED current now becomes:
ILED = ILED _ FS x ZoneTarget5 x D = 26 mA x 100% x 50% | 13 mA.
(9)
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Example: ALS Averaging:
As an example, suppose the LM3530 ALS Configuration Register is loaded with 0x3B. This configures the device
for:
ALS1 as the active ALS input (bits [6:5] = 01)
Enables Ambient Light Current Control (bit 4 = 1)
Enables the ALS circuitry (bit 3 = 1)
Sets the ALS Averaging Time to 256 ms (bits [2:0] = 011)
Next, the ALS Resistor Select Register is loaded with 0x04. This configures the ALS2 input as high impedance
and configures the ALS1 input with a 2.27-kΩ internal pull-down resistor. The Zone Boundary Registers and
Zone Target Registers are left with their default values. The Brightness Ramp Rate Register is loaded with 0x2D.
This sets up the LED current ramp rate at 16.384 ms/step. Finally, the General Configuration Register is loaded
with 0x15. This sets up the device with:
Simple Enable OFF (bit 7 = 0)
PWM Polarity High (bit 6 = 0)
PWM Input Disabled (bit 5 = 0)
Full-Scale Current = 22.5mA (bits [4:2] = 101)
Brightness Mapping Mode as Exponential (bit 1 = 0)
Device Enabled via I2C (bit 0 = 1)
As the device starts up the APDS-9005 ambient light sensor (connected to the ALS1 input) detects 500 LUX.
This puts approximately 437.5 mV at ALS1 (see Figure 37). This places the measured ambient light between
Zone Boundary Registers 1 and 2, thus corresponding to Zone Target Register 2. The default value for this
register is 0x4C. The LED current is programmed to:
ILED = ILED _ FS x ZoneTarget2 = 22.5 mA x 5.781% | 1.3 mA .
(10)
Referring to Figure 37, initially the Averager is loaded with Zone 0 so it takes 2 averaging periods for the LM3530
to change to the new zone. After the ALS1 voltage remains at 437.5 mV for two averaging periods (end of period
2) the LM3530 repeats Zone 2 and signals the LED current to begin ramping to the Zone 2 target beginning at
average period 3. Since the ramp rate is set at 16.384 ms/step the LED current goes from 0 to 1.3 mA in 76 ×
16.384 ms = 1.245s (approximately 5 average periods).
After the LED current has been at its steady state of 1.3 mA for a while, the ambient light suddenly steps to 900
LUX for 500 ms and then steps back to 500 LUX. In this case the 900 LUX will place the ALS1 voltage at
approximately 979 mV corresponding to Zone 4 somewhere during average period 10 and fall back to 437.5 mV
somewhere during average period 12. The averager output during period #10 goes to 3, and then during period
11, goes to 4. Since there have been 2 increases in the average during period 10 and period 11, the beginning of
average period #12 shows a change in the brightness zone to Zone 4. This results in the LED current ramping to
the new value of 22.5 mA (the Zone 4 target). During period #12 the ambient light steps back to 500 LUX and
forces ALS1 to 437.5 mV (corresponding to Zone 2). After average period 12 and period 13 have shown that the
averager transitioned lower two times, the brightness zone changes to the new target at the beginning of period
14. This signals the LED current to ramp down to the zone 2 target of 1.3 mA. Looking back at average period 12
and period 13, the LED current was only able to ramp up to 7.38 mA due to the ramp rate of 16.384 ms/step (2
average periods of 256 ms each) before it was instructed to ramp back to the Zone 2 target at the start of period
14. This example demonstrates not only the averaging feature, but how additional filtering of transient events on
the ALS inputs can be accomplished by using the LED current ramp rates.
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LM3530 turns on
and averaging
begins
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
979 mV (900 LUX)
VALS1
437.5 mV
(500 LUX)
0 mV
4
3
3
2
2
ALS
Average
Zone 4
Zone 2
Zone 2
Brightness
Zone
Zone 0
7.38 mA
LED
Current
1.3 mA
0
Figure 37. ALS Averaging Example
8.3.16 Interrupt Output
INT is an open-drain output which pulls low when the Ambient Light Sensing circuit has transitioned to a new
ambient brightness zone. When a read-back of the ALS Information Register is done INT is reset to the open
drain state.
8.3.17 Overvoltage Protection
Overvoltage protection is set at 40 V (minimum) for the LM3530-40 and 23.6 V minimum for the LM3530-25. The
40-V version allows typically up to 11 series white LEDs (assuming 3.5 V per LED + 400 mV headroom voltage
for the current sink = 38.9 V). When the OVP threshold is reached the LM3530 switching converter stops
switching, allowing the output voltage to discharge. Switching will resume when the output voltage falls to
typically 1 V below the OVP threshold. In the event of an LED open circuit the output will be limited to around 40
V with a small amount of voltage ripple. The 25-V version allows up to 6 series white LEDs (assuming 3.5-V per
LED + 400 mV headroom voltage for the current sink = 21.4 V). The 25-V OVP option allows for the use of lower
voltage and smaller sized (25 V) output capacitors. The 40-V device would typically require a 50-V output
capacitor.
8.3.18 Hardware Enable
The HWEN input is an active high hardware enable which must be pulled high to enable the device. Pulling this
pin low disables the I2C-compatible interface, the simple enable/disable input, the PWM input, and resets all
registers to their default state (see Table 4).
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8.3.19 Thermal Shutdown
In the event the die temperature reaches 140°C, the LM3530 will stop switching until the die temperature cools
by 15°C. In a thermal shutdown event the device is not placed in reset; therefore, the contents of the registers
are left in their current state.
8.4 Device Functional Modes
8.4.1 Shutdown
With HWEN Low, or bit 0 in register 0x10 set to 0, the device is in shutdown. In this mode the boost converter
and the current sink are both off and the supply current into IN is reduced to typically 1 µA.
8.4.2 I2C Mode
I2C-Compatible Control Mode is enabled by writing a '1' to the I2C Device Enable bit (bit [0] of the General
Configuration Register), a '0' to the Simple Enable bit (bit 7), and a '0' to the PWM Enable bit (bit 5). With bit 5 =
0, the duty cycle information at the PWM input is not used in setting the LED current. In this mode the LED
current is a function of the Full-Scale LED current bits (bits [4:2] of the General Configuration Register) and the
code in the Brightness Control Register. The LED current mapping for the Brightness Control Register can be
linear or exponential depending on bit [1] in the General Configuration Register (see Exponential or Linear
Brightness Mapping Modes section). Using I2C-Compatible Control Only, the Full-Scale LED Current bits and the
Brightness Control Register code provides nearly 1016 possible current levels selectable over the I2C-compatible
interface.
8.4.3 PWM + I2C Mode
PWM + I2C-compatible current control mode is enabled by writing a ‘1’ to the Enable PWM bit (General
Configuration Register bit [5]) and writing a ‘1’ to the I2C Device Enable bit (General Configuration Register bit 0).
This makes the LED current a function of the PWM input duty cycle (D), the Full-Scale LED current (ILED_FS), and
the % of full-scale LED current . The % of Full-Scale LED current is set by the code in the Brightness Control
Register. The LED current using PWM + I2C-Compatible Control is given by Equation 11:
ILED = I LED_ FS x BRT x D
(11)
BRT is the percentage of Full Scale Current as set in the Brightness Control Register. The Brightness Control
Register can have either exponential or linear brightness mapping depending on the setting of the BMM bit (bit
[1] in General Configuration Register).
8.4.4 ALS Mode
With bits [4:3] of the ALS Configuration Register both set to 1, the LM3530 is configured for Ambient Light
Current Control. In this mode the ambient light sensing inputs (ALS1, and/or ALS2) monitor the outputs of analog
output ambient light sensing photo diodes and adjust the LED current depending on the ambient light.
8.4.5 Simple Enable Mode
Simple Enable Mode With bits [7 and 5] of the General Configuration Register set to ‘1’ the PWM input is
enabled as a simple enable/disable. The simple enable/disable feature operates as described in Figure 36. In
this mode, when the PWM input is held high (PWM Polarity bit = 0) for > 2 ms the LM3530 will turn on the LED
current at the programmed Full-Scale Current × % of Full-Scale Current as set by the code in the Brightness
Control Register. When the PWM input is held low for > 2 ms the device will shut down.
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8.5 Programming
8.5.1 I2C-Compatible Interface
8.5.1.1 Start and Stop Condition
The LM3530 is controlled via an I2C-compatible interface. START and STOP conditions classify the beginning
and the end of the I2C session. A START condition is defined as SDA transitioning from HIGH to LOW while SCL
is HIGH. A STOP condition is defined as SDA transitioning from LOW to HIGH while SCL is HIGH. The I2C
master always generates the 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.
SDA
SCL
S
P
Start Condition
Stop Condition
Figure 38. Start and Stop Sequences
8.5.1.2 I2C-Compatible Address
The 7bit chip address for the LM3530 is (0x38, or 0x39) for the 40-V version and (0x36) for the 25-V version.
After the START condition, the IC 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 READ2. 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 39. I2C-Compatible Chip Address (0x38)
I2C Compatible Address
MSB
0
Bit 7
LSB
1
Bit 6
1
Bit 5
0
Bit 4
1
Bit 3
1
Bit 2
0
Bit 1
R/W
Bit 0
Figure 40. I2C-Compatible Chip Address (0x36)
8.5.1.3 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 LM3530 pulls
down SDA during the 9th clock pulse, signifying an acknowledge. An acknowledge is generated after each byte
has been received.
There are fourteen 8-bit registers within the LM3530 as detailed in Table 4.
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8.6 Register Maps
8.6.1 Register Descriptions
Table 4. LM3530 Register Definition
REGISTER NAME
ADDRESS
POR VALUE
General Configuration
1. Simple Interface Enable
2. PWM Polarity
3. PWM enable
4. Full-Scale Current Selection
5. Brightness Mapping Mode
Select
6. I2C Device Enable
FUNCTION
0x10
0xB0
ALS Configuration
1. ALS Current Control Enable
2. ALS Input Enable
3. ALS Input Select
4. ALS Averaging Times
0x20
0x2C
Brightness Ramp Rate
Programs the rate of rise and fall
of the LED current
0x30
0x00
ALS Zone Information
1. Zone Boundary Change Flag
2. Zone Brightness Information
0x40
0x00
ALS Resistor Select
Internal ALS1 and ALS2
Resistances
0x41
0x00
Brightness Control (BRT)
Holds the 7 bit Brightness Data
0xA0
0x7F
Zone Boundary 0 (ZB0)
ALS Zone Boundary #0
0x60
0x33
Zone Boundary 1 (ZB1)
ALS Zone Boundary #1
0x61
0x66
Zone Boundary 2 (ZB2)
ALS Zone Boundary #2
0x62
0x99
Zone Boundary 3 (ZB3)
ALS Zone Boundary #3
0x63
0xCC
Zone Target 0 (Z0T)
Zone 0 LED Current Data. The
LED Current Source transitions to
the brightness code in Z0T when
the ALS_ input is less than the
zone boundary programmed in
ZB0.
0x70
0x19
Zone Target 1 (Z1T)
Zone 1 LED Current Data. The
LED Current Source transitions to
the brightness code in Z1T when
the ALS_ input is between the
zone boundaries programmed in
ZB1 and ZB0.
0x71
0x33
Zone Target 2 (Z2T)
Zone 2 LED Current Data. The
LED Current Source transitions to
the brightness code in Z2T when
the ALS_ input is between the
zone boundaries programmed in
ZB2 and ZB1.
0x72
0x4C
Zone Target 3 (Z3T)
Zone 3 LED Current Data. The
LED Current Source transitions to
the brightness code in Z3T when
the ALS_ input is between the
zone boundaries programmed in
ZB3 and ZB2.
0x73
0x66
Zone Target 4 (Z4T)
Zone 4 LED Current Data. The
LED Current Source transitions to
the brightness code in Z4T when
the ALS_ input is between the
zone boundaries programmed in
ZB4 and ZB3.
0x74
0x7F
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*Note: Unused bits in the LM3530 Registers default to a logic '1'.
8.6.1.1 General Configuration Register (GP)
The General Configuration Register (address 0x10) is described in Figure 41 and Table 5.
General Configuration Register
Address 0x10, Default Value 0xB0
MSB
Bit 7
Simple
Interface
Enable
Bit 6
PWM
Polarity
Bit 5
PWM
Enable
Bit 4
Full
Scale
Current
Select
Bit 3
Full
Scale
Current
Select
LSB
Bit 2
Full
Scale
Current
Select
Bit 1
Brightness
Mapping
Mode
Select
Bit 0
I2C
Interface
Enable
Figure 41. General Configuration Register
Table 5. General Configuration Register Description (0x10)
Bit 7
(PWM Simple
Enable
0 = Simple
Interface at
PWM Input is
Disabled
1 = Simple
Interface at
PWM Input is
Enabled
Bit 6
(PWM Polarity)
Bit 5
(EN_PWM)
see Figure 31
0 = PWM active
high
1 = PWM active
low
0 = LED current
is not a function
of PWM duty
cycle
1 = LED current
is a function of
duty cycle
Bit 4
(Full-Scale
Current
Select)
Bit 3
(Full-Scale
Current
Select)
Bit 2
(Full-Scale
Current
Select)
Bit 1
(Mapping Mode
Select)
000 = 5 mA full-scale current
001 = 8.5 mA full-scale current
010 = 12 mA full-scale current
011 = 15.5 mA full-scale current
100 = 19 mA full-scale current
101 = 22.5 mA full-scale current
110 = 26 mA full-scale current
111 = 29.5 mA full-scale current
0 = exponential
mapping
1 = linear
mapping
Bit 0
(I2C Device
Enable)
0 = Device
Disabled
1 = Device
Enabled
8.6.1.2 ALS Configuration Register
The ALS Configuration Register controls the Ambient Light Sensing input functions and is described in Figure 42
and Table 6.
ALS Configuration Register
Address 0x20, Default Value 0x2C
MSB
Bit 7
(Not Used)
Bit 6
ALS Input
Select 2
Bit 5
ALS Input
Select 1
Bit 4
ALS Mode
Bit 3
ALS
Enable
LSB
Bit 2
ALS
Averaging
Time
Bit 1
ALS
Averaging
Time
Bit 0
ALS
Averaging
Time
Figure 42. ALS Configuration Register
Table 6. ALS Configuration Register Description (0x20)
Bit 7
N/A
Bit 6
ALS Input
Select
Bit 5
ALS Input
Select
00 = The Average of ALS1 and
ALS2 is used to control the LED
brightness
01 = ALS1 is used to control the
LED brightness
10 = ALS2 is used to control the
LED brightness
11 = The ALS input with the
highest voltage is used to control
the LED brightness
Bit 4
ALS Enable
Bit 3
ALS Enable
00 or 10 = ALS is disabled. The
Brightness Register is used to
determine the LED current.
01 = ALS is enabled. The
Brightness Register is used to
determine the LED Current.
11 = ALS inputs are enabled.
Ambient light determines the LED
current.
Bit 2
ALS
Averaging
Time
Bit 1
ALS
Averaging
Time
Bit 0
ALS
Averaging
Time
000 = 32 ms
001 = 64 ms
010 = 128 ms
011 = 256 ms
100 = 512 ms
101 = 1024 ms
110 = 2048 ms
111 = 4096 ms
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8.6.1.3 Brightness Ramp Rate Register
The Brightness Ramp Rate Register controls the rate of rise or fall of the LED current. Both the rising rate and
falling rate are independently adjustable Figure 43 and Table 7 describe the bit settings.
Brightness Ramp Rate Register
Address 0x30, Default Value 0x00
MSB
Bit 7
Not Used
Bit 6
Not Used
Bit 5
BRRI2
Bit 4
BRRI1
LSB
Bit 2
BRRD2
Bit 3
BRRI0
Bit 1
BRRD1
Bit 0
BRRD0
Figure 43. Brightness Ramp Rate Register
Table 7. Brightness Ramp Rate Register Description (0x30)
Bit 7
Bit 6
N/A
N/A
Bit 5
(BRRI2)
Bit 4
(BRRI1)
Bit 3
(BRRI0)
000 = 8 µs/step (1.106 ms from 0 to Full Scale)
001 = 1.024 ms/step (130 ms from 0 to Full Scale)
010 = 2.048 ms/step (260 ms from 0 to Full Scale)
011 = 4.096 ms/step (520 ms from 0 to Full Scale)
100 = 8.192 ms/step (1.04 s from 0 to Full Scale)
101 = 16.384 ms/step (2.08 s from 0 to Full Scale)
110 = 32.768 ms/step (4.16 s from 0 to Full Scale)
111 = 65.538 ms/step (8.32 s from 0 to Full Scale)
Bit 2
(BRRD2)
Bit 1
(BRRD1)
Bit 0
(BRRD0)
000 = 8 µs/step (1.106 ms from Full Scale to 0)
001 = 1.024 ms/step (130 ms from Full Scale to 0)
010 = 2.048 ms/step (260 ms from Full Scale to 0)
011 = 4.096 ms/step (520 ms from Full Scale to 0)
100 = 8.192 ms/step (1.04 s from Full Scale to 0)
101 = 16.384 ms/step (2.08 s from Full Scale to 0)
110 = 32.768 ms/step (4.16 s from Full Scale to 0)
111 = 65.538 ms/step (8.32 s from Full Scale to 0)
8.6.1.4 ALS Zone Information Register
The ALS Zone Information Register is a read-only register that is updated every time the active ALS input(s)
detect that the ambient light has changed to a new zone as programmed in the Zone Boundary Registers. See
Zone Boundary Register description. A new update to the ALS Zone Information Register is signaled by the INT
output going from high to low. A read-back of the ALS Zone Information Register will cause the INT output to go
open-drain again. The Zone Change Flag (bit 3) is also updated on a Zone change and cleared on a read back
of the ALS Zone Information Register. Figure 44 and Table 8 detail the ALS Zone Information Register.
ALS Zone Information Register
Address 0x40, Default Value 0x00
MSB
Bit 7
(Not Used)
Bit 6
Bit 5
(Not Used) (Not Used)
Bit 4
(Not Used)
Bit 3
Zone
Boundry
Change
Flag
LSB
Bit 2
Z2
Zone Data
Bit 1
Z1
Zone Data
Bit 0
Z0
Zone Data
Figure 44. ALS Zone Information Register
Table 8. ALS Zone Information Register Description (0x40)
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
(Zone Boundary Change Flag)
N/A
N/A
N/A
N/A
1 = the active ALS input has
changed to a new ambient light
zone as programmed in the
Zone Boundary Registers (ZB0
-ZB3)
0 = no zone change
Bit 2
(Z2)
Bit 1
(Z1)
Bit 0
(Z0)
000 = Zone 0
001 = Zone 1
010 = Zone 2
011 = Zone 3
100 = Zone 4
8.6.1.5 ALS Resistor Select Register
The ALS Resistor Select Register configures the internal resistance from either the ALS1 or ALS2 input to GND.
Bits [3:0] program the input resistance at the ALS1 input and bits [7:4] program the input resistance at the ALS2
input. With bits [3:0] set to all zeroes the ALS1 input is high impedance. With bits [7:4] set to all zeroes the ALS2
input is high impedance.
30
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ALS Resistor Select Register
Address 0x41, Default Value 0x00
MSB
Bit 7
ALSR2A
Bit 6
ALSR2B
Bit 5
ALSR2C
Bit 4
ALSR2D
Bit 3
ALSR1A
LSB
Bit 2
ALSR1B
Bit 1
ALSR1C
Bit 0
ALSR1D
Figure 45. ALS Resistor Select Register
Table 9. ALS Resistor Select Register Description (0x41)
Bit 7
(ALSR2A)
Bit 6
(ALSR2B)
Bit 5
(ALSR2C)
Bit 4
(ALSR2D)
Bit 3
(ALSR1A)
0000 = ALS2 is high impedance
0001 = 13.531 kΩ (73.9 µA at 1 V)
0010 = 9.011 kΩ (111 µA at 1 V)
0011 = 5.4116 kΩ (185 µA at 1 V)
0100 = 2.271 kΩ (440 µA at 1 V)
0101 = 1.946 kΩ (514 µA at 1 V)
0110 = 1.815 kΩ (551 µA at 1 V)
0111 = 1.6 kΩ (625 µA at 1 V)
1000 = 1.138 kΩ (879 µA at 1 V)
1001 = 1.05 kΩ (952 µA at 1 V)
1010 = 1.011 kΩ (989 µA at 1 V)
1011 = 941 Ω (1.063 mA at 1 V)
1100 = 759 Ω (1.318 mA at 1 V)
1101 = 719 Ω (1.391 mA at 1 V)
1110 = 700 Ω (1.429 mA at 1 V)
1111 = 667 Ω (1.499 mA at 1 V)
Bit 2
(ALSR1B)
Bit 1
(ALSR1C)
Bit 0
(ALSR1D)
0000 = ALS2 is high impedance
0001 = 13.531 kΩ (73.9 µA at 1 V)
0010 =9.011 kΩ (111 µA at 1 V)
0011 = 5.4116 kΩ (185 µA at 1 V)
0100 = 2.271 kΩ (440 µA at 1 V)
0101 = 1.946 kΩ (514 µA at 1 V)
0110 = 1.815 kΩ (551 µA at 1 V)
0111 = 1.6 kΩ (625 µA at 1 V)
1000 = 1.138 kΩ (879µA at 1 V)
1001 = 1.05 kΩ (952 µA at 1 V)
1010 = 1.011 kΩ (989 µA at 1 V)
1011 = 941 Ω (1.063 mA at 1 V)
1100 = 759 Ω (1.318 mA at 1 V)
1101 = 719 Ω (1.391 mA at 1 V)
1110 = 700 Ω (1.429 mA at 1 V)
1111 = 667 Ω (1.499 mA at 1 V)
8.6.1.6 Brightness Control Register
The Brightness Register (BRT) is an 8-bit register that programs the 127 different LED current levels (Bits [6:0]).
The code written to BRT is translated into an LED current as a percentage of ILED_FULLSCALE as set via the FullScale Current Select bits (General Configuration Register bits [4:2]). The LED current response has a typical
1000:1 dimming ratio at the maximum full-scale current (General Configuration Register bits [4:2] = (111) and
using the exponential weighted dimming curve.
There are two selectable LED current profiles. Setting the General Configuration Register bit 1 to 0 selects the
exponentially weighted LED current response (see Figure 34). Setting this bit to '1' selects the linear weighted
curve (see Figure 35). Table 2 and Table 3 show the percentage Full-Scale LED Current at a given Brightness
Register Code for both the Exponential and Linear current response.
Brightness Control Register
Address 0xA0, Default Value 0x7F
MSB
Bit 7
(Not Used)
Bit 6
Data
Bit 5
Data
Bit 4
Data
Bit 3
Data
LSB
Bit 2
Data
Bit 1
Data
Bit 0
Data
Figure 46. Brightness Control Register
Table 10. Brightness Control Register Description (0xA0)
Bit 7
N/A
Bit 6
Data (MSB)
Bit 5
Data
Bit 4
Data
Bit 3
Data
Bit 2
Data
Bit 1
Data
Bit 0
Data
LED Brightness Data (Bits [6:0]
Exponential Mapping (see Table 2)
0000000 = LEDs Off
0000001 = 0.08% of Full Scale
:
:
:
1111111 = 100% of Full Scale
Linear Mapping (see Table 3)
0000000 = LEDs Off
0000001 = 0.79% of Full Scale
:
:
:
1111111 = 100% of Full Scale
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8.6.1.7 Zone Boundary Register
The Zone Boundary Registers are programmed with the ambient light sensing zone boundaries. The default
values are set at 20% (200 mV), 40% (400 mV), 60% (600 mV), and 80% (800 mV) of the full-scale ALS input
voltage range (1V). The necessary conditions for proper ALS operation are that the data in ZB0 < data in ZB1 <
data in ZB2 < data in ZB3.
Zone Boundary Register 0 (ZB0)
Address 0x60, Default Value 0x33
MSB
Bit 7
Data
Bit 6
Data
Bit 6
Data
Bit 6
Data
Bit 2
Data
Bit 1
Data
Bit 5
Data
Bit 4
Data
Bit 3
Data
Bit 5
Data
Bit 4
Data
Bit 3
Data
Bit 6
Data
Bit 5
Data
Bit 4
Data
Bit 3
Data
Bit 0
Data
LSB
Bit 2
Data
Bit 1
Data
Bit 0
Data
LSB
Bit 2
Data
Bit 1
Data
Zone Boundary Register 3 (ZB3)
Address 0x63, Default Value 0xCC
MSB
Bit 7
Data
Bit 3
Data
Zone Boundary Register 2 (ZB2)
Address 0x62, Default Value 0x99
MSB
Bit 7
Data
Bit 4
Data
Zone Boundary Register 1 (ZB1)
Address 0x61, Default Value 0x66
MSB
Bit 7
Data
Bit 5
Data
LSB
Bit 0
Data
LSB
Bit 2
Data
Bit 1
Data
Bit 0
Data
Figure 47. Zone Boundary Registers
8.6.1.8 Zone Target Registers
The Zone Target Registers contain the LED brightness data that corresponds to the current active ALS zone.
The default values for these registers and their corresponding percentage of full-scale current for both linear and
exponential brightness is shown in Figure 48 and Table 11.
32
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Zone Target Register 0 (ZT0)
Address 0x70, Default Value 0x19
MSB
N/A
Bit 6
Data
Bit 5
Data
Bit 6
Data
Bit 5
Data
Bit 6
Data
Bit 1
Data
Bit 3
Data
Bit 4
Data
Bit 2
Data
Bit 3
Data
Bit 6
Data
Bit 5
Data
Bit 4
Data
Bit 1
Data
Bit 1
Data
Bit 5
Data
Bit 4
Data
Bit 3
Data
Bit 0
Data
LSB
Bit 2
Data
Bit 1
Data
Zone Target Register 4 (ZT4)
Address 0x74, Default Value 0x7F
Bit 6
Data
Bit 0
Data
LSB
Bit 2
Data
Bit 3
Data
Bit 0
Data
LSB
Zone Target Register 3 (ZT3)
Address 0x73, Default Value 0x66
MSB
N/A
Bit 4
Data
Bit 5
Data
MSB
N/A
Bit 2
Data
Zone Target Register 2 (ZT2)
Address 0x72, Default Value 0x4C
MSB
N/A
Bit 3
Data
Zone Target Register 1 (ZT1)
Address 0x71, Default Value 0x33
MSB
N/A
Bit 4
Data
LSB
Bit 0
Data
LSB
Bit 2
Data
Bit 1
Data
Bit 0
Data
Figure 48. Zone Target Registers
Table 11. Zone Boundary and Zone Target Default Mapping
ZONE BOUNDARY
(DEFAULT)
ZONE TARGET
REGISTER
(DEFAULT)
FULL-SCALE
CURRENT
(DEFAULT)
LINEAR MAPPING
(DEFAULT)
EXPONENTIAL
MAPPING
(DEFAULT)
Boundary 0,
Active ALS input is less than 200 mV
0x19
19 mA
19.69% (3.74 µA)
0.336% (68.4 µA)
Boundary 1,
Active ALS input is between 200 mV and
400 mV
0x33
19 mA
40.16% (7.63 µA)
1.43% (272 µA)
Boundary 2,
Active ALS input is between 400 mV and
600 mV
0x4C
19 mA
59.84% (11.37 mA)
5.78% (1.098 mA)
Boundary 3,
Active ALS input is between 600 mV and
800 mV
0x66
19 mA
80.31% (15.26 mA)
24.84% (4.72 mA)
Boundary 4,
Active ALS input is greater than 800mV
0x7F
19 mA
100% (19 mA)
100% (19 mA)
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9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The LM3530 incorporates a 40-V (maximum output) boost, a single current sink, and a dual ambient light sensor
interface. The maximum boost output voltage is 40 V (min) for the LM3530-40 version. The LM3530 boost will
drive the output voltage to whatever voltage necessary to maintain 400mV at the ILED input. The 40-V max
output typically allows the LM3530 to drive from 2 series up to 12 series LEDs (3.2V max voltage per LED). For
applications that do not use one or both of the ALS inputs, the ALS input can be connected to GND or left
floating.
9.2 Typical Application
L
D1
Up to 40V
2.7V to 5.5V
C OUT
VLOGIC
SW
IN
10 k:
10 k:
10 k:
10 k:
C IN
LM3530
SCL
OVP
SDA
HWEN
INT
PWM
ILED
VIN
Ambient Light
Sensor
VIN
ALS1
Ambient Light
Sensor
ALS2
GND
Figure 49. LM3530 Typical Application
9.2.1 Design Requirements
Example requirements for typical voltage inverter applications:
Table 12. Design Parameters
DESIGN PARAMETER
EXAMPLE VALUE
Input voltage range
2.7 V to 5.5 V
Output current
0 mA to 30 mA
Boost switching frequency
500 kHz
Table 13. Application Circuit Component List
COMPONENT
MANUFACTURER
PART NUMBER
VALUE
SIZE
CURRENT/VOLTAGE RATING
L
TDK
VLF3014ST100MR82
10 µH
3 mm × 3 mm × 1.4 mm
ISAT = 820 mA
COUT
Murata
GRM21BR71H105KA12
1 µF
0805
50 V
CIN
Murata
GRM188B31A225KE33
2.2 µF
0603
10 V
D1
Diodes Inc.
B0540WS
Schottky
SOD-323
40 V/500 mA
ALS1
Avago
APDS-9005
Ambient Light Sensor
1.6 mm x 1.5 mm × 0.6 mm
0 to 1100 Lux
ALS2
Avago
APDS-9005
Ambient Light Sensor
1.6 mm x 1.5 mm × 0.6 mm
0 to 1100 Lux
34
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9.2.2 Detailed Design Procedure
9.2.2.1 LED Current Setting/Maximum LED Current
The maximum LED current is restricted by the following factors: the maximum duty cycle that the boost converter
can achieve, the peak current limitations, and the maximum output voltage.
9.2.2.2 Maximum Duty Cycle
The LM3530 can achieve up to typically 94% maximum duty cycle. Two factors can cause the duty cycle to
increase: an increase in the difference between VOUT and VIN and a decrease in efficiency. This is shown by
Equation 12:
D=1-
VIN x ä
VOUT
(12)
For a 9-LED configuration VOUT = (3.6 V x 9LED + VHR) = 33 V operating with η = 70% from a 3-V battery, the
duty cycle requirement would be around 93.6%. Lower efficiency or larger VOUT to VIN differentials can push the
duty cycle requirement beyond 94%.
9.2.2.3 Peak Current Limit
The LM3530 boost converter has a peak current limit for the internal power switch of 839 mA typical (739 mA
minimum). When the peak switch current reaches the current limit, the duty cycle is terminated resulting in a limit
on the maximum output current and thus the maximum output power the LM3530 can deliver. Calculate the
maximum LED current as a function of VIN, VOUT, L, efficiency (η) and IPEAK as:
IOUT_MAX =
(I PEAK - 'I L ) x K x VIN
VOUT
'I L =
where
VIN x (VOUT - VIN)
2 x fSW x L x VOUT
where
•
•
ƒSW = 500 kHz
η and IPEAK can be found in the Efficiency and IPEAK curves in the Specifications and Application Curves.
(13)
9.2.2.4 Output Voltage Limitations
The LM3530 has a maximum output voltage of 41 V typical (40 V minimum) for the LM3530-40 version and 24 V
typical (23.6 V minimum) for the LM3530-25 version. When the output voltage rises above this threshold (VOVP)
the overvoltage protection feature is activated and the duty cycle is terminated. Switching will cease until VOUT
drops below the hysteresis level (typically 1 V below VOVP). For larger numbers of series connected LEDs the
output voltage can reach the OVP threshold at larger LED currents and colder ambient temperatures. Typically
white LEDs have a –3mV/°C temperature coefficient.
9.2.2.5 Output Capacitor Selection
The LM3530’s output capacitor has two functions: filtering of the boost converters switching ripple, and to ensure
feedback loop stability. As a filter, the output capacitor supplies the LED current during the boost converters on
time and absorbs inductor energy during the switch off time. This causes a sag in the output voltage during the
on time and a rise in the output voltage during the off time. Because of this, the output 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 1 µF and have low ESR otherwise the
LM3530 boost converter can become unstable. This requires the use of ceramic output capacitors. Table 14 lists
part numbers and voltage ratings for different output capacitors that can be used with the LM3530.
Table 14. Recommended Input/Output Capacitors
MANUFACTURER
PART NUMBER
VALUE (µF)
SIZE
RATING (V)
DESCRIPTION
Murata
Murata
GRM21BR71H105KA12
1
0805
50
COUT
GRM188B31A225KE33
2.2
0805
10
TDK
CIN
C1608X5R0J225
2.2
0603
6.3
CIN
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9.2.2.6 Inductor Selection
The LM3530 is designed to work with a 10-µH to 22-µH inductor. When selecting the inductor, ensure that the
saturation rating for the inductor is high enough to accommodate the peak inductor current. Equation 14 and
Equation 15 calculate the peak inductor current based upon LED current, VIN, VOUT, and efficiency.
I PEAK =
I LED VOUT
+ 'I L
×
K
VIN
(14)
where:
'IL =
VIN x (VOUT - VIN )
2 x f SW x L x VOUT
(15)
When choosing L, the inductance value must also be large enough so that the peak inductor current is kept
below the LM3530 switch current limit. This forces a lower limit on L given by Equation 16.
VIN x (VOUT - VIN)
L>
§
I LED _ MAX x VOUT
©
K x VIN
2 x f SW x VOUT x ¨
¨I SW_MAX -
·
¸¸
¹
(16)
ISW_MAX is given in , efficiency (η) is shown in the Application Curves, and ƒSW is typically 500 kHz.
Table 15. Suggested Inductors
MANUFACTURER
PART NUMBER
VALUE
(µH)
SIZE (mm)
RATING (mA)
DC RESISTANCE (Ω)
TDK
VLF3014ST-100MR82
10
2.8 × 3 × 1.4
820
0.25
TDK
VLF3010ST-220MR34
22
2.8 × 3 × 1
340
0.81
TDK
VLF3010ST-100MR53
10
2.8 × 3 × 1
530
0.41
TDK
VLF4010ST-100MR80
10
2.8 × 3 × 1
800
0.25
TDK
VLS252010T-100M
10
2.5 × 2 × 1
650
0.71
Coilcraft
LPS3008-103ML
10
2.95 × 2.95 × 0.8
520
0.65
Coilcraft
LPS3008-223ML
22
2.95 × 2.95 × 0.8
340
1.5
Coilcraft
LPS3010-103ML
10
2.95 × 2.95 × 0.9
550
0.54
Coilcraft
LPS3010-223ML
22
2.95 × 2.95 × 0.9
360
1.2
Coilcraft
XPL2010-103ML
10
1.9 × 2 × 1
610
0.56
Coilcraft
EPL2010-103ML
10
2×2×1
470
0.91
TOKO
DE2810C-1117AS-100M
10
3 × 3.2 × 1
600
0.46
9.2.2.7 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 16 lists various diodes that can be
used with the LM3530. For 25-V OVP devices a 30-V Schottky is adequate. For 40-V OVP devices, a 40-V
Schottky diode should be used.
Table 16. Suggested Diodes
MANUFACTURER
PART NUMBER
VALUE
SIZE (mm)
RATING
Diodes Inc
B0540WS
Schottky
SOD-323 (1.7 × 1.3)
40 V/500 mA
36
Diodes Inc
SDM20U40
Schottky
SOD-523 (1.2 × 0.8 × 0.6)
40 V/200 mA
On Semiconductor
NSR0340V2T1G
Schottky
SOD-523 (1.2 × 0.8 × 0.6)
40 V/250 mA
On Semiconductor
NSR0240V2T1G
Schottky
SOD-523 (1.2 × 0.8 × 0.6)
40 V/250 mA
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9.2.3 Application Curves
IFULL_SCALE = 19 mA
IFULL_SCALE = 19 mA
Figure 50. Efficiency vs VIN
Figure 51. Efficiency vs VIN
IFULL_SCALE = 19 mA
Figure 52. Efficiency vs VIN
Figure 53. Efficiency vs ILED
Figure 54. Efficiency vs ILED
Figure 55. Efficiency vs ILED
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10 Power Supply Recommendations
The LM3530 operates from a 2.7-V to 5.5-V input voltage. The 500-kHz switching frequency for the boost can
lead to ripple voltage on the input voltage rail. To minimize this, the input to the inductor should be well bypassed
with a 1-µF (min) ceramic bypass capacitor (see Output Capacitor Selection).
11 Layout
11.1 Layout Guidelines
The LM3530 contains an inductive boost converter which detects a high switched voltage (up to 40 V) at the SW
pin, and a step current (up to 900 mA) 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 56 highlights
these two noise generating components.
Voltage Spike
VOUT + VF Schottky
Pulsed voltage at SW
Current through
Schottky Diode and COUT
IPEAK
IAVE = IIN
Paracitic
Circuit Board
Inductances
Current through
inductor
Affected Node
due to capacitive
coupling
Cp1
L
Lp1
D1
Lp2
2.7V to 5.5V
VLOGIC
IN
10 k:
Up to 40V
COUT
SW
Lp3
10 k:
SCL
OVP
SDA
LM3530
LCD Display
ILED
GND
Figure 56. LM3530 Boost Converter Showing Pulsed Voltage At SW (High Dv/Dt) and
Current Through Schottky and COUT (High Di/Dt)
38
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Layout Guidelines (continued)
The following lists the main (layout sensitive) areas of the LM3530 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
11.1.1 Output Capacitor Placement
The output capacitor is in the path of the inductor current discharge path. As a result COUT detects a high current
step from 0 to IPEAK each time the switch turns off and the Schottky diode turns on. Any inductance along this
series path from the cathode of the diode through COUT and back into the LM3530 GND pin will contribute to
voltage spikes (VSPIKE = LP_ × dI/dt) at SW and OUT which can potentially overvoltage 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 device GND bump. The best placement for COUT
is on the same layer as the LM3530 so as to avoid any vias that can add excessive series inductance (see
Figure 58, Figure 59, and Figure 60).
11.1.2 Schottky Diode Placement
The Schottky diode is in the path of the inductor current discharge. As a result the Schottky diode detects 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 = LP_ × dI/dt) at SW and OUT which can potentially overvoltage 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 (LP_) and minimize these voltage spikes (see Figure 58, Figure 59, and Figure 60 ).
11.1.3 Inductor Placement
The node where the inductor connects to the LM3530 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, the other traces
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 dramatically reduce the capacitive coupling 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 Figure 58, Figure 59, and Figure 60).
11.1.4 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.
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Layout Guidelines (continued)
The driver current requirement can range from 50 mA at 2.7 V to over 200 mA at 5.5 V with fast durations of
approximately 10 ns to 20 ns. 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 LM3530, 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 switching frequency of the device. This can cause the supply current ripple
to be:
1. Approximately equal to the inductor current ripple when the resonant frequency occurs well above the
LM3530 switching frequency;
2. Greater then the inductor current ripple when the resonant frequency occurs near the switching frequency;
and
3. Less then the inductor current ripple when the resonant frequency occurs well below the switching frequency.
Figure 57 shows the series RLC circuit formed from the output impedance of the supply and the input capacitor.
The circuit is re-drawn for the AC case where the VIN supply is replaced with a short to GND and the LM3530 +
Inductor is replaced with a current source (ΔIL). In Figure 57 below,
1. = the criteria for an underdamped response.
2. = the resonant frequency, and
3. = the approximated supply current ripple as a function of LS, RS, and CIN.
As an example, consider a 3.6-V supply with 0.1-Ω 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 2 from Figure 57 the supply current
ripple can be approximated as 1.68 multiplied by the inductor current ripple. Increasing the series inductance (LS)
to 500 nH causes the resonant frequency to move to around 225 kHz and the supple current ripple to be
approximately 0.25 multiplied by the inductor current ripple.
40
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Layout Guidelines (continued)
'IL
ISUPPLY
RS
L
LS
SW
IN
+
LM3530
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 ¨2S x 500 kHz x L S -
·
¸
2S x 500 kHz x CIN ¸¹
1
2
Figure 57. Input RLC Network
11.2 Layout Example
Figure 58, Figure 59, and Figure 60 show example layouts which apply the required proper layout guidelines.
These figures should be used as guides for laying out the LM3530 circuit.
Figure 58. Layout Example 1
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Layout Example (continued)
Figure 59. Layout Example 2
Figure 60. Layout Example 3
42
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12 Device and Documentation Support
12.1 Device Support
12.1.1 Third-Party Products Disclaimer
TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT
CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES
OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER
ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE.
12.2 Documentation Support
12.2.1 Related Documentation
For related documentation, see the following:
Texas Instruments Application Note 1112: DSBGA Wafer Level Chip Scale Package (SNVA009).
12.3 Trademarks
All trademarks are the property of their respective owners.
12.4 Electrostatic Discharge Caution
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.
12.5 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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43
PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
LM3530TME-40/NOPB
ACTIVE
DSBGA
YFQ
12
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
DX
LM3530TMX-40/NOPB
ACTIVE
DSBGA
YFQ
12
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
DX
LM3530UME-25A/NOPB
ACTIVE
DSBGA
YFZ
12
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-30 to 85
DS
LM3530UME-40/NOPB
ACTIVE
DSBGA
YFZ
12
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-30 to 85
40
LM3530UME-40B/NOPB
ACTIVE
DSBGA
YFZ
12
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
LM3530UMX-25A/NOPB
ACTIVE
DSBGA
YFZ
12
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-30 to 85
DS
LM3530UMX-40/NOPB
ACTIVE
DSBGA
YFZ
12
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-30 to 85
40
LM3530UMX-40B/NOPB
ACTIVE
DSBGA
YFZ
12
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
DT
DT
(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)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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