MSL3080 - Complete

5, 6 and 8 String 60mA LED Drivers with Integrated Boost
Controller
______________ General Description
The MSL3050/MSL3060/MSL3080 multi-channel LED drivers with
integrated boost regulator controller offer a complete solution to
drive parallel LED strings at up to 40V. The LED current sinks
control up to 60mA each for up to 19W of LED power. The
MSL3050 has five current sinks, the MSL3060 has six and the
MSL3080 has eight. Parallel connect the current sinks for
increased string current. A single resistor sets LED current, with
string matching and accuracy within ±3%.
The advanced integrated PWM circuitry allows up to 4095:1
dimming, and offers simple PWM dimming control. External PWM
dimming is controlled by a signal at the PWM input, which sets
both the PWM duty cycle and frequency of the dimming signals.
The internal PWM dimming is controlled by registers accessible
through the I2C serial interface.
The MSL3050/60/80 feature integrated fault detection circuitry
that detects and acts upon string open-circuit and LED short
circuit faults, boost regulator over-voltage faults, and die overtemperature faults. A proprietary Efficiency Optimizer maintains
Features:
sufficient boost regulator output voltage to maintain LED current
2
regulation while minimizing power use. A 1MHz I C/SMBus serial
allows
optional
dimmingat
control,
• Drives 8 parallelinterface
60mA
LED
strings
up fault
to inspection and
control of driver configuration; for serial interface information see
40V LED string the
voltage
MSL3050/60/80/50/60/80/86/87/88 Programming Guide.
• Integrated boost controller
The MSL3050/60/80 are offered in the 24-pin VQFN lead-free,
• Offers true 12-bit
LED dimming
at 120Hz
halogen-free,
RoHS compliant
package and operate over -40°C
to +85°C.
• String open circuit
and LED short circuit fault detection
and automatic shut
down
_____________________
Applications
• ±3% current accuracy
and current
balance
Long Life, Efficient
LED Backlighting
for:
Televisionsfor
and all
Desktop
Monitors
• Single resistor sets current
LED
strings
Medical and Industrial Instrumentation
• External PWM dimming
Automotive Audio-Visual Displays
Channel Signs
• Internal PWM dimming
control engine
Architectural Lighting
• Single PWM input sets dimming duty cycle and frequency
_____________
Ordering Information
• Internal PWM dimming
(use optional)
• Synchronizes PWM
LCD panel refresh PKG
rate
PARTdimming to
DESCRIPTION
5-CH LED
driverdimming
with integrated at
boost
• Frequency multiplier allows
PWM
multiples
24 pin
controller and resistor based LED Short
4 x 4 x 0.75mm
MSL3050
Circuit threshold
setting,
with single
of LCD panel refresh
frequency
(see
Programming
Guide)
VQFN
PWM input.
• 1MHz I²C/SMBus interface;
use
optional
6-CH LED driver with integrated boost
24 pin
controller and resistor based LED Short
MSL3060
4 x 4 x 0.75mm
• Resistor programmable
LED short circuit threshold
Circuit threshold setting, with single
VQFN
PWM input.protection
• Die over-temperature cut-off
8-CH LED driver with integrated boost
24 pin
• -40°C to +85°C MSL3080
operating
temperature
range
controller
and resistor based LED
Short
4 x 4 x 0.75mm
Circuit threshold setting, with single
VQFN
• Lead free, halogen free,
RoHS
compliant
package
PWM input.
I²C and SMBus are trademarks of their respective owners.
MSL3050/60/80 preliminary datasheet revision 0.1
Description:
© Atmel Inc., 2011. All rights reserved.

____________________ Key Features
Drives 5/6/8 parallel 60mA LED strings at up to 40V LED
string voltage
Integrated boost controller
Offers true 12-bit LED dimming at 200Hz
String open circuit and LED short circuit fault detection and
automatic shut down
±3% current accuracy and current balance
Single resistor sets current for all LED strings
External PWM dimming
Internal PWM dimming control engine
Single PWM input sets dimming duty cycle and frequency
Internal PWM dimming (use optional)
Synchronizes PWM dimming to LCD panel refresh rate
Frequency multiplier allows PWM dimming at multiples of
LCD panel refresh frequency (see Programming Guide)
1MHz I²C/SMBus interface; use optional
Resistor programmable LED short circuit threshold
Die over-temperature cut-off protection
-40°C to +85°C operating temperature range
Lead free, halogen free, RoHS compliant package



Atmel MSL3080








8 String 60mA LED Drivers
with Integrated Boost Controller
FULL DATASHEET





_______________ Application Circuit
VPWR = 12V
VIN = 5V
10 F
10 H
20 F
60V 3A
VIN
PVIN
GATE
CS
ENABLE
I 2C
INTERFACE
EN
MSL3080
FDC
5612
25m
FB
3.12k
COMP
SDA
VLED
47.5k
2nF 22k
SCL
FAULT
OUTPUT
FLTB
PWM
INPUT
PWM
STR0
STR1
STR2
ILED
STR3
STR4
91.3k
STR5
FBI
STR6
STR7
PGND
GND
EP
APPLICATION CIRCUIT
Page 1 of 24
The MSL3080 8-channel LED drivers with integrated boost regulator controller offers a complete solution
to drive parallel LED strings at up to 40V. The LED current sinks control up to 60mA each for up to 19W
of LED power. The MSL3080 has eight current sinks. Parallel connect the current sinks for increased
string current. A single resistor sets LED current, with string matching and accuracy within ±3%.
The advanced integrated PWM circuitry allows up to 4095:1 dimming, and offers simple PWM dimming
control. External PWM dimming is controlled by a signal at the PWM input, which sets both the PWM
duty cycle and frequency of the dimming signals. The internal PWM dimming is controlled by registers
accessible through the I2C serial interface.
The MSL3080 feature integrated fault detection circuitry that detects and acts upon string open-circuit
and LED short circuit faults, boost regulator over-voltage faults, and die over-temperature faults. A
proprietary Efficiency Optimizer maintains sufficient boost regulator output voltage to maintain LED
current regulation while minimizing power use. A 1MHz I2C/SMBus serial interface allows optional
dimming control, fault inspection and control of driver configuration; for serial interface information see
the “MSL3040/50/60/80/86/87/88 Programming Guide”.
The MSL3080 IS offered in the 24-pin VQFN lead-free, halogen-free, RoHS compliant package and
operate over -40°C to +85°C.
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
1
DBIE-20120814
Table of Contents
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
Packages and Pin Connections.................................................................. 3
Pin Descriptions........................................................................................... 4
Absolute Maximum Ratings........................................................................ 5
Electrical Characteristics............................................................................ 6
Typical Operating Characteristics.............................................................. 7
Block Diagram.............................................................................................. 9
Typical Application Circuits...................................................................... 10
Detailed Description.................................................................................. 13
8.1
LED Driver Comparison..................................................................................................13
8.2
Boost Regulator Overview..............................................................................................14
8.3
Error Amplifier.................................................................................................................14
8.4
Gate Driver.....................................................................................................................15
8.5Soft-Start........................................................................................................................15
8.6
Boost Fault Monitoring and Protection...........................................................................15
8.7
LED Current Regulators and PWM Dimming Modes.....................................................15
8.8
Efficiency Optimizer (EO)...............................................................................................15
8.9
Fault Monitoring and Auto-Handling...............................................................................15
8.10
Internal Supervisory and LDO........................................................................................16
8.11
Internal Oscillator............................................................................................................16
8.12
Over Temperature Shutdown..........................................................................................16
8.13
Power Saving Modes......................................................................................................16
8.14I2C Serial Interface and Driver Control...........................................................................16
9.0 Application Information............................................................................. 17
9.1
Bypassing VIN and PVIN................................................................................................17
9.2
Setting the LED Current.................................................................................................17
9.3
Fault Monitoring and Automatic Fault Handling..............................................................17
9.4
Setting the LED Short-Circuit Threshold.........................................................................17
9.5
Boost Regulator..............................................................................................................18
9.6
The Efficiency Optimizer (EO)........................................................................................19
9.7
Setting the Boost Regulator Output Voltage...................................................................20
9.8
Choosing the Input and output Capacitors.....................................................................20
9.9
Choosing the Inductor....................................................................................................20
9.10 Setting the External MOSFET Current Limit...................................................................21
9.11 Choosing the Switching MOSFET..................................................................................21
9.12 Choosing the Output Rectifier........................................................................................21
9.13 Loop Compensation.......................................................................................................21
10.0 LED Dimming Control................................................................................ 23
11.0 Ordering Information................................................................................. 23
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
2
PHASE SHIFTED LED DIMMING SIGNALS
/MSL3060/MSL3080
1.0 Packages andDatasheet
Pin Connections
Preliminary
By default, string PWM dimming is staggered in time to reduce t
MSL3040/41 automatically determine the stagger times based o
frequency.
FB
1
VIN
2
COMP
CS
EN
FLTB
PVIN
●
GND
PHASE SHIFTED LED DIMMING SIGNALS
1.1 24 pin 4 x 4 x 0.75mm VQFN Package
By default, string PWM dimming is staggered in time to reduce the transient current d
Packagedetermine
Information
MSL3040/41 automatically
the stagger times based on the number of enab
frequency.
24
23
22
21
20
19
18
GATE
Package Information
17 PGND
3
TED LEDSDADIMMING
SIGNALS
MSL3080
16 ILED
4
15 CGND
ng PWM SCL
dimming
is staggered
in time
to reduce the transient current demand on the boost regulator. The
(TOP VIEW)
utomatically
SCTH 5determine the stagger times
14 PWM based on the number of enabled strings and the PWM dimming
9
10
11
12
STR6
STR1
8
STR5
7
nformation
MMING SIGNALS
STR4
13 STR7
STR3
6
STR2
STR0
ming is staggered in time to reduce the transient current demand on the boost regulator. The
determine the stagger times based on the number of enabled strings and the PWM dimming
on
Page 2 of 24
eserved.
Page 22 of 22
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
© Atmel Inc., 2011. All rights reserved.
3
Page 22 of 22
Page 22 of
2.0 Pin Descriptions
Table 2.1 Pin Assignments
Name
MSL3080 Pin Description
VLED Voltage Regulator Feedback Input: Connect a resistive voltage divider from the boost regulator output, VLED, to FB to set the unoptimized boost regulator output voltage. The feedback regulation voltage is 2.5V.
FB
1
VIN
2
Power Supply Input: Power supply input. Apply 4.5V to 5.5V to VIN. Decouple VIN to GND a 1µF or greater capacitor placed close to VIN.
SDA
3
I²C Serial Data I/O: SDA is the I²C serial interface data input/output. Connect SDA to VIN when unused. For interface information see the
“MSL3040/50/60/80/86/87/88 Programming Guide”.
SCL
4
I²C Serial Clock Input: SCL is the I²C serial interface clock input. Connect SCL to VIN when unused. For interface information see the
“MSL3040/50/60/80/86/87/88 Programming Guide”.
SCTH
5
String Short Circuit Threshold Level Setting Input: SCTH programs the LED string short-circuit detection threshold. Connect a resistor from
SCTH to GND to set the short-circuit threshold level to 4.9V (1kΩ), 5.8V (27kΩ), 6.8V (68kΩ) or 7.6V (330kΩ). A short circuit is detected
when the STRn voltage is above the threshold while STRn is on. See the section “Setting the LED Short-Circuit Threshold” on page 17 for
information.
STR0
6
LED String 0 Current Sink: Connect the cathode end of series LED String 0 to STR0. If not used, connect STR0 to GND.
STR1
7
LED String 1 Current Sink: Connect the cathode end of series LED String 1 to STR1. If not used, connect STR1 to GND.
STR2
8
LED String 2 Current Sink: Connect the cathode end of series LED String 2 to STR2. If not used, connect STR2 to GND.
STR3
9
LED String 3 Current Sink: Connect the cathode end of series LED String 3 to STR3. If not used, connect STR3 to GND.
STR4
10
LED String 4 Current Sink: Connect the cathode end of series LED String 4 to STR4. If not used, connect STR4 to GND.
STR5
11
LED String 5 Current Sink: Connect the cathode end of series LED String 5 to STR5. If not used, connect STR5 to GND.
STR6
12
LED String 6 Current Sink: Connect the cathode end of series LED String 6 to STR6. If not used, connect STR6 to GND.
STR7
13
LED String 7 Current Sink: Connect the cathode end of series LED String 7 to STR7. If not used, connect STR7 to GND.
CGND
15
Connect To Ground: Connect CGND to GND close to the driver.
PWM
14
PWM Dimming and Synchronization Input: Drive PWM with a pulse-width modulated signal with duty cycle of 0% to 100% and frequency of
20Hz to 50kHz to control the duty cycle and the frequency of all LED strings. For serial interface controlled PWM dimming connect PWM to
GND and refer to the register definitions section for registers 0x10 through 0x14 in the “MSL3040/50/60/80/86/87/88 Programming Guide”.
ILED
16
Maximum LED Current Control Input: Connect a resistor from ILED to GND to set the full-scale LED current. See the section “Setting the
LED Current” on page 17 for more information.
PGND
17
Power Ground: Ground of the boost regulator gate driver. Connect PGND to GND, EP and CGND as close to the MSL3080 as possible.
GATE
18
Gate Drive Output: Connect GATE to the gate of the boost regulator switching MOSFET
PVIN
19
Boost Regulator Power Supply Input: PVIN is the power supply input for the external MOSFET gate driver. Apply 4.5V to 5.5V to PVIN.
Decouple PVIN with two 1µF capacitors placed close to PVIN.
FLTB
20
Fault Output: FLTB sinks current to GND when a fault is detected. Clear faults by toggling EN low and then high, by cycling input power off
and on, or through the I2C serial interface; see the “MSL3040/50/60/80/86/87/88 Programming Guide” for information.
EN
21
Enable Input: Drive EN high to turn on the device, drive it low to turn it off. For automatic startup connect EN to VIN. Toggle EN low then high
to reset FLTB, or reset it through the I2C serial interface.
CS
22
Boost Regulator Current Sense Input: Connect the current sense resistor from CS and the MOSFET source to GND to set the boost regulator
current limit. The current limit threshold is 100mV. See the section “Setting the External MOSFET Current Limit” beginning on page 21 for
more
COMP
23
Boost Regulator Compensation Node: Connect the compensation network components from COMP to FB to compensate the boost regulator
control loop, as shown in the Typical Applications Circuit on page 10. See the section “Loop Compensation” beginning on page 21 for more
information.
GND
24
Signal Ground: Connect GND to EP, PGND and CGND as close to the device as possible.
EP
Exposed Die-Attach Paddle: Connect EP to GND, CGND, PGND and to the system ground. EP is the return path for the LED current as well
as the primary thermal path to remove heat generated in the MSL3080. Use a large circuit board trace to connect from EP to the boost supply
output capacitor ground and to the input supply ground return. Connect EP to a large copper ground plane for best thermal and electrical
performance.
EP
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
4
3.0 Absolute Maximum Ratings
Voltage (with respect to GND)
VIN, PVIN, EN, SDA, SCL, PWM, FLTB, SCTH, ILED, CS, COMP, FB, GATE................................................................ -0.3V to +5.5V
STR0 to STR7.................................................................................................................................................................... -0.3V to +40V
PVIN to VIN........................................................................................................................................................................................ ±1V
PGND, CGND, EP............................................................................................................................................................ -50mV to 50mV
Current (into pin)
VIN
.................................................................................................................................................................................................. 50mA
GATE, PVIN................................................................................................................................................................................ ±1250mA
STR0 to STR7, CGND...................................................................................................................................................................... 75mA
EP, PGND, GND..........................................................................................................................................................................-1000mA
All other pins......................................................................................................................................................................-20mA to 20mA
Continuous Power Dissipation
24-Pin 4mm x 4mm VQFN (derate 25mW/°C above TA = +70°C)............................................................................................... 1850mW
Ambient Operating Temperature Range TA = TMIN to TMAX........................................................................................................... -40°C to +85°C
Junction to Ambient Thermal Resistance (θJA), 4-Layer (Note 8).............................................................................................................29°C/W
Junction to Ambient Thermal Resistance (θJA), 2-Layer (Note 8).............................................................................................................38°C/W
Junction to Case Thermal Resistance (θJC).............................................................................................................................................8.6°C/W
Junction Temperature .............................................................................................................................................................................. +125°C
Storage Temperature Range...................................................................................................................................................... -65°C to +125°C
Lead Soldering Temperature, 10s............................................................................................................................................................. +300°C
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
5
4.0 Electrical Characteristics
VVIN = 5V, VEN = 5V, Default Register Settings of Table 1, TA = -40°C to 85°C, unless otherwise noted. Typical values are at TA = +25°C
Parameter
DC Electrical Characteristics
VIN Operating Supply Voltage
VIN Operating Supply Current
VIN Shutdown Supply Current
SDA, SCL, PWM, SYNC Input High Voltage
SDA, SCL, PWM, SYNC Input Low Voltage
Minimum PWM On-Time
PWM, SYNC Input Frequency Range
SDA, FLTB Output Low Voltage
EN Threshold
ILED Regulation Voltage
STR0 to STR7 LED Regulation Current
STR0 to STR7 LED Current Load Regulation
STR0 to STR7 LED Current Matching
STR0 to STR7 Minimum Headroom
STR0 to STR7 Short Circuit Fault Threshold
FB Feedback Output Current
FB Feedback Output Current Step Size
FBI Input Disable Threshold
Thermal shutdown temperature
Boost Regulator Electrical Characteristics
Switching Frequency
Gate Voltage Rise/Fall Time
CS Current Limit Threshold Voltage
Maximum Duty Cycle
Minimum On Time
Boost Regulator Leading-Edge Blanking Period
FB Regulation Voltage
I²C Switching Characteristics
SCL Clock Frequency
Bus Timeout Period
STOP to START Condition Bus Free Time
Repeated START condition Hold Time
Repeated START condition Setup Time
STOP Condition Setup Time
SDA Data Hold Time
SDA Data Valid Acknowledge Time
SDA Data Valid Time
SDA Data Set-Up Time
SCL Clock Low Period
SCL Clock High Period
SDA, SCL Fall Time
SDA, SCL Rise Time
SDA, SCL Input Suppression Filter Period
Note 1.
Note 2.
Note 3.
Note 4.
Note 5.
Note 6.
Note 7.
Note 8.
Note 9.
Conditions and Notes
Min
Typ
4.5
All STRn outputs 100% duty
EN = GND
Max
Unit
5.5
18
1
V
mA
µA
V
V
ns
Hz
V
V
V
mA
%/V
%
V
V
µA
µA
mV
°C
1.82
0.72
20
Sinking 6mA
VEN rising
Minimum RILED = 60kΩ
RILED = 100kΩ, TA= 25°C VSTRn = 1V
RILED = 100kΩ VSTRn = 1V to 5V
String to average of all strings
VSTRn = 60mA
RSCTH = 1.0kΩ
FBO DAC = 0xFF, VFB = 0
400
200
50,000
0.4
1.5
58.2
1.25
60.0
0.15
-3
3.98
224
61.8
3
0.5
4.96
350
1.1
50
Temperature Rising, 10°C Hysteresis
135
569
CGATE = 1nF
75
At factory set boost frequency
fBOOST = 350kHz to 1MHz (contact factory for boost frequencies different
from 625kHz)
2.4
1/tSCL
ttimeout
tBUF
tHD:STA
tSU:STA
tSU:STOP
tHD:DAT
tVD:ACK
tVD:DAT
tSU:DAT
tLOW
tHIGH
tf
tr
tSP
Bus timeout disabled (Note 1)
TA = 25°C (Note 7)
(Note 7)
(Note 7)
(Note 7)
(Note 7)
(Note 7)
(Note 2) (Note 7)
(Note 3) (Note 7)
(Note 7)
(Note 7)
(Note 7)
(Note 4) (Note 5) (Note 7)
(Note 7)
(Note 6) (Note 7)
0
29
0.5
0.26
0.26
0.26
0
0.05
0.05
100
0.5
0.26
665
50
111
90.1
762
147
kHz
ns
mV
%
241
300
ns
130
2.5
2.6
ns
V
1000
30
0.55
0.55
120
120
50
kHz
ms
µs
µs
µs
µs
ns
µs
µs
ns
µs
µs
ns
ns
ns
Minimum SCL clock frequency is limited by the bus timeout feature, which resets the serial bus interface if either SDA or SCL is held low for timeout.
tVD:ACK = SCL LOW to SDA (out) LOW acknowledge time.
tVD:DAT = minimum SDA output data-valid time following SCL LOW transition.
A master device must internally provide an SDA hold time of at least 300ns to ensure an SCL low state.
The maximum SDA and SCL rise times is 300ns. The maximum SDA fall time is 250ns. This allows series protection resistors to be connected between SDA and SCL inputs and
the SDA/SCL bus lines without exceeding the maximum allowable rise time.
MSL3080 include input filters on SDA and SCL that suppress input noise less than 50ns
Parameter is guaranteed by design and not production tested.
Per JEDEC specification JESD51-5 and JESD51-12.
Tests performed at TA = 25°C, specifications over temperature guaranteed by design.
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
6
MSL3050/MSL3060/MSL3080 Datasheet
Preliminary
5.0 Typical Operating Characteristics
Typical Operating Characteristics (Typical Operating Circuit, unless otherwise stated)
(Typical Operating Circuit, unless otherwise stated, TA = +25°C, unless otherwise noted)
BOOST REGULATOR EFFICIENCY vs.
OUTPUT CURRENT
100
10000
1000000
90
10000
85
IIN(µA)
(µA)
IIN
80
75
70
10100
VPWR = 12V
60
0.1
fBOOST = 625kHz
50
0
200
400
600
800
10
EN = 1
sleep = slpPwrSv = 1
EN = 0EN = 0
1
VLED  37V
55
EN = 1
sleep = slpPwrSv = 0
BOOST NOT SWITCHING
100
1000
1
65
1,000
0.1
0.010.01
4.5 4.5
4.6 4.6
4.7 4.7
4.8 4.8
4.9
OUTPUT CURRENT (mA)
STRn CURRENT (mA
EN = 1
sleep = slpPwrSv = 0
BOOST NOT SWITCHING
EN = 1
100000 sleep = slpPwrSv = 1
1000
95
EFFICIENCY (%)
SUPPLY
CURRENT
SUPPLY
CURRENT
SUPPLY
VOLTAGE
vs.vs.
SUPPLY
VOLTAGE
10
100
RISET (k )
5.5
START-UP WAVEFORMS
STRn CURRENT vs. RISET
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
5.0 5.1
4.9
5.0 5.2
5.1 5.3
5.2 5.4
5.3 5.5
5.4
VIN (V)
VIN (V)
1000
MSL3050/MSL3060/MSL3080
Datasheet
CH1 = V , CH2 = V , CH3 = V
, CH4 = I
EN
© Atmel Inc., 2011. All rights reserved.
CH1 = VEN, CH2 = VLED, CH3 = VSTRx, CH4 = IPWR
AUTO CALIBRATION
STRx
PWR
Preliminary
BOOST WAVEFORMS
10% LED DUTY CYCLE
START-UP WAVEFORMS (ZOOM)
MSL3050/60/80 preliminary datasheet revision 0.1
LED
Page 6 of 24
CH1 = VLED, CH2 = VGATE, CH3 = IINDUCTOR
BOOST WAVEFORMS
100% LED DUTY CYCLE
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
7
CH1 = V
CH3 = VSTRx, CH4 = IPWR(continued)
5.0 Typical
Operating
EN, CH2 = VLED,Characteristics
CH1 = VLED, CH2 = VGATE, CH3 = IINDUCTOR
(Typical Operating Circuit, unless otherwise stated, TA = +25°C, unless otherwise noted)
BOOST WAVEFORMS
100% LED DUTY CYCLE
AUTO CALIBRATION
CH2 = VLED, CH3 = VSTRx
MSL3050/MSL3060/MSL3080 Datasheet
CH1 = VLED, CH2 = VGATE, CH3 = IINDUCTOR
BOOST REGULATOR WAVEFORMS
10% TO 99.5% LED DUTY CYCLE
MSL3050/60/80 preliminary datasheet revision 0.1
© Atmel Inc., 2011. All rights reserved.
Preliminary
BOOST REGULATOR GATE DRIVE RISE/FALL
WITH 3nF CAPACITIVE LOAD
Page 7 of 24
CH1 = VLED, CH2 = VGATE, CH3 = VPWM, CH4 = IINDUCTOR
DRIVER RISE TIME
CH2 = VGATE
DRIVER FALL TIME
AUTOMATIC PHASE SHIFTED PWM DIMMING
This scope image shows the voltage (VSTR0) and current (ISTR0)
waveforms for string zero, and their turn-on rise times and delay
from PWM rising. Also shown is the string power supply output
CH1
= VSTR0
, CH2
VSTR2
, CH3 = V
, CH4
VSTR6
STR4
(VLED),
which
shows=little
disturbance.
For
this
photo=string
0 is
enabled with all other strings disabled.
This scope image shows the voltage (VSTR0) and current (ISTR0)
waveforms for string zero, and their turn-off fall times. Also shown
is the string power supply output (VLED), which shows very little
disturbance. For this photo string 0 is enabled with all other strings
disabled, and a 220pF capacitor in series with a 11Ω resistor in
series is placed from STR0 to GND at the device.
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
8
MSL3050/MSL3060/MSL3080 Datasheet
Preliminary
6.0 Block
BlockDiagram
Diagram
Figure 6.1. Block Diagram
MSL3080
Figure 1. MSL3050/MSL3060/MSL3080 Block Diagram
MSL3050/60/80 preliminary datasheet revision 0.1
© Atmel Inc., 2011. All rights reserved.
Page 9 of 24
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
9
MSL3050/MSL3060/MSL3080 Datasheet
Preliminary
7.0 Typical Application Circuits
Figure 7.1. Typical Operating Circuit for Eight 60mA Strings of 10 White LEDs each.
Typical Application Circuits
VPWR = 12V
10 F
VIN = 5V
1 F
2
VIN
ENABLE
21
3
I2C
INTERFACE
4
PWM
INPUT
14
FAULT
OUTPUT
20
5
18
GATE
22
CS
VLED
47.5k
SDA
MSL3080
FB
1
22k
PWM
3.12k
2nF
FLTB
COMP
23
SCTH
STR0
STR1
ILED
STR2
STR3
93.1k
STR4
STR5
15
FDC5612
25m
EN
SCL
2x
10 F
B380
19
PVIN
82k
16
10 H
2x 1 F
STR6
CGND
PGND
17
EP
STR7
GND
24
6
7
8
9
10
11
12
13
Figure 2. Typical Operating Circuit for Eight 60mA Strings of 10 White LEDs each.
MSL3050/60/80 preliminary datasheet revision 0.1
© Atmel Inc., 2011. All rights reserved.
Page 10 of 24
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
10
MSL3050/MSL3060/MSL3080 Datasheet
Figure 7.2. Typical Operating Circuit for Four 120mA Strings of 10 White LEDs each.
VPWR = 12V
Preliminary
10 F
VIN = 5V
1 F
2
VIN
ENABLE
21
3
I2C
INTERFACE
4
PWM
INPUT
14
FAULT
OUTPUT
20
5
18
GATE
22
CS
VLED
47.5k
SDA
MSL3080
FB
1
22k
PWM
3.12k
2nF
FLTB
COMP
23
SCTH
STR0
STR1
ILED
STR2
STR3
93.1k
STR4
STR5
15
FDC5612
25m
EN
SCL
2x
10 F
B380
19
PVIN
82k
16
10 H
2x 1 F
STR6
CGND
PGND
17
EP
STR7
GND
24
6
7
8
9
10
11
12
13
Figure 3. Typical Operating Circuit for Four 120mA Strings of 10 White LEDs each.
MSL3050/60/80 preliminary datasheet revision 0.1
© Atmel Inc., 2011. All rights reserved.
Page 11 of 24
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
11
MSL3050/MSL3060/MSL3080 Datasheet
Figure 7.3. Typical Operating Circuit for One 480mA String of 10 White LEDs.
VPWR = 12V
Preliminary
10 F
VIN = 5V
1 F
2
VIN
ENABLE
21
3
I2C
INTERFACE
4
PWM
INPUT
14
FAULT
OUTPUT
20
5
18
GATE
22
CS
VLED
47.5k
SDA
MSL3080
FB
1
22k
PWM
3.12k
2nF
FLTB
COMP
23
SCTH
STR0
STR1
ILED
STR2
STR3
93.1k
STR4
STR5
15
FDC5612
25m
EN
SCL
2x
10 F
B380
19
PVIN
82k
16
10 H
2x 1 F
STR6
CGND
PGND
17
EP
STR7
GND
24
6
7
8
9
10
11
12
13
Figure 4. Typical Operating Circuit for One 480mA String of 10 White LEDs.
Detailed Description
The MSL3050/MSL3060/MSL3080 are LED drivers with five, six and eight internal current regulators respectively, each
capable of driving up to 60mA LED current They feature an integrated boost regulator controller with a proprietary
Efficiency Optimizer voltage control algorithm that lowers power use to the minimum required to assure LED current
regulation. The driver outputs allow parallel connection to increase string current, at the expense of the number of strings,
and a single resistor sets the current for all strings. The drivers support 12-bit PWM LED dimming ratios. The driver
synchronizes LED dimming and controls duty cycle with a single external digital signal at the PWM input.
The MSL3050/60/80 include comprehensive fault monitoring and automatic fault handling. Automatic fault handling allows
the drivers to operate without any microcontroller or FPGA, while optional control via I2C allows customized fault handling
and driver control for more complex applications. All drivers also feature optional register-set PWM dimming, fault
management and other controls via the I2C serial interface; for interface information see the
MSL3050/60/80/50/60/80/86/87/88 Programming Guide.
The small 4x4mm VQFN package allows a small overall LED driver solution, while maintaining high package power
dissipation for high output power capability.
MSL3050/60/80 preliminary datasheet revision 0.1
© Atmel Inc., 2011. All rights reserved.
Page 12 of 24
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
12
8.0 Detailed Description
The MSL3080 is an LED driver with eight internal current regulators, each capable of driving up to 60mA LED current. They feature an integrated
boost regulator controller with a proprietary Efficiency Optimizer voltage control algorithm that lowers power use to the minimum required to
assure LED current regulation. The driver outputs allow parallel connection to increase string current, at the expense of the number of strings,
and a single resistor sets the current for all strings. The drivers support 12-bit PWM LED dimming ratios. The driver synchronizes LED dimming
and controls duty cycle with a single external digital signal at the PWM input.
The MSL3080 includes comprehensive fault monitoring and automatic fault handling. Automatic fault handling allows the drivers to operate
without any microcontroller or FPGA, while optional control via I2C allows customized fault handling and driver control for more complex
applications. All drivers also feature optional register-set PWM dimming, fault management and other controls via the I2C serial interface; for
interface information see the “MSL3040/50/60/80/86/87/88 Programming Guide”.
The small 4x4mm VQFN package allows a small overall LED driver solution, while maintaining high package power dissipation for high output
power capability
8.1 LED Driver Comparison
Table 8.1. LED Driver Comparison with Similar Parts
PART
NUMBER
OF LED
STRINGS
MAX
CURRENT
PER
STRING
PHASE
SHIFTED
STRING
DRIVERS
INTERNAL
BOOST
CONTROLLER
RESISTOR SET
LED SHORT
CIRCUIT
THRESHOLD
SEPARATE
SYNC
INPUT***
MSL3086
8
60mA
YES
YES
YES
NO
MONITOR, INDUSTRIAL PANEL
BEST FOR
MSL3087*
8
60mA
YES
NO
YES
NO
SMALL TV
MSL3088
8
60mA
YES
YES
NO
YES
SMALL TV
8
60mA
NO
YES
YES
NO
MONITOR, INDUSTRIAL PANEL
4**
120mA
NO
YES
YES
NO
MONITOR, INDUSTRIAL PANEL
2**
240mA
NO
YES
YES
NO
MONITOR, INDUSTRIAL PANEL
1**
480mA
NO
YES
YES
NO
MONITOR, INDUSTRIAL PANEL
MSL3040*
4
120mA
YES
YES
YES
NO
MONITOR, AUTOMOTIVE
MSL3041*
4
120mA
YES
YES
YES
YES
MONITOR, AUTOMOTIVE
MSL3080
MSL3050*
MSL3060*
5
60mA
NO
YES
YES
NO
INDUSTRIAL PANEL
1**
300mA
NO
YES
YES
NO
INDUSTRIAL PANEL
6
60mA
NO
YES
YES
NO
MONITOR, INDUSTRIAL PANEL
3**
120mA
NO
YES
YES
NO
MONITOR, INDUSTRIAL PANEL
2**
180mA
NO
YES
YES
NO
MONITOR, INDUSTRIAL PANEL
1**
360mA
NO
YES
YES
NO
MONITOR, INDUSTRIAL PANEL
* Future product, contact factory for information.
** Drivers without phase shift allow parallel connection of string drive outputs for increased string current.
*** Drivers with separate SYNC input expect two control signals, one for dimming duty cycle and one for dimming frequency.
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
13
8.2 Boost Regulator Overview
The MSL3080 boost regulator boosts the input voltage up to the regulated output voltage (for design details see the section “Boost
Regulator” beginning on page 17, the following text presents an overview of the boost regulator controller). The boost regulator uses
an external switching MOSFET, current sense resistor, inductor, rectifier, and input and output capacitors (Figure 8.1). External MOSFET
and current sense resistor allow the boost regulator to operate over wide input and output voltage ranges, and LED currents. It includes
a 2.5V reference voltage, fixed slope compensation and external voltage regulator compensation to optimize the control loop for each
configuration. Because the boost regulator components are external it supports a number of converter topologies, such as SEPIC,
flyback, and single-switch forward. The boost regulator includes soft-start, adjustable cycle-by-cycle current limiting, and output overvoltage fault detection.
Preliminary
Figure 8.1. Power Section of MSL3080
MSL3050/MSL3060/MSL3080 Datasheet
5V
VPWR
PVIN
CIN
L1
D1
GATE DRIVE
GATE
LIMIT
1.1V
SLOPE
COMP
0.4V
CURRENT
0.1 V
Q1
COUT
RESR
RCS
GND
A = 11
SENSE
RTOP
FB
EFFICIENCY
OPTIMIZER
+
1.5V
CS
VLED
RCOMP
SOFT
START
CCOMP2
CCOMP1
RBOTTOM
COMP
COMPENSATION:
CCOMP2 = POLE
CCOMP1, RCOMP = ZERO
REF
DROPOUT DETECT
MSL3080
MSL3050
MSL3060
MSL3080
STRn
LED
CURRENT
SINK
Figure 5. Power section of MSL3050/60/80
RROR AMPLIFIER
8.3 ErrorEAmplifier
The internal error amplifier compares the external divided output voltage at FB to the internal 2.5V reference voltage to set
Thethe
internal
error amplifier
compares
the. external
divided
output
voltage
at FB at
to the
internal
2.5V reference
voltage use
to set
the regulated
The error
amplifier
output
voltage
COMP
is externally
accessible;
it to
regulated
output voltage,
VLED
errorregulator.
amplifier output
voltage
at COMP
is externally
accessible;
use itcomparator
to compensate
voltageif regulator.
FB
output
voltage, VLED
compensate
the. The
voltage
FB also
drives
the integrated
boost
over-voltage
thatthe
detects
the output
alsovoltage
drives the
integrated
over-voltage
thata detects
if the output
exceeds the
regulation
voltage,
generate a
exceeds
the boost
regulation
voltage,comparator
to generate
fault condition.
Thevoltage
error amplifier
internally
controls
thetocurrent
faultmode
condition.
error amplifier internally controls the current mode PWM regulator.
PWMThe
regulator.
GATE DRIVER
The gate driver drives the gate of the external boost regulator switching MOSFET. The drain of the switching MOSFET in
turn drives the boost inductor and rectifier to boost the input voltage to the regulated output voltage. The gate driver
sources and sinks up to 1A allowing fast switching speed and allows the use of MOSFETs with high gate capacitance.
The gate driver power is separated from the internal circuitry power to reduce internal noise and to allow separate gate
driver bypassing for optimal performance.
SOFT-START
The boost regulator includes a built in soft-start to prevent excessive input current overshoot at turn-on. The soft-start
ramps the output regulation voltage from 0V at turn-on to the as-configured regulation output voltage over 1.6ms. Note
that the boost regulator only controls output voltages greater than the input voltage; when the soft-start sets the regulation
voltage below the input voltage, the actual output voltage remains at approximately theAtmel
input MSL3080
voltage. Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
MSL3050/60/80 preliminary datasheet revision 0.1
© Atmel Inc., 2011. All rights reserved.
Page 14 of 24
14
8.4 Gate Driver
The gate driver drives the gate of the external boost regulator switching MOSFET. The drain of the switching MOSFET in turn drives the
boost inductor and rectifier to boost the input voltage to the regulated output voltage. The gate driver sources and sinks up to 1A allowing
fast switching speed and allows the use of MOSFETs with high gate capacitance. The gate driver power is separated from the internal
circuitry power to reduce internal noise and to allow separate gate driver bypassing for optimal performance.
8.5 Soft-Start
The boost regulator includes a built in soft-start to prevent excessive input current overshoot at turn-on. The soft-start ramps the output
regulation voltage from 0V at turn-on to the as-configured regulation output voltage over 1.6ms. Note that the boost regulator only
controls output voltages greater than the input voltage; when the soft-start sets the regulation voltage below the input voltage, the actual
output voltage remains at approximately the input voltage.
8.6 Boost Fault Monitoring and Protection
The boost regulator includes fault monitoring and protection circuits to indicate faults and prevent damage to the boost regulator or other
circuitry. The boost regulator has cycle by cycle current limiting that prevents excessive current through the power MOSFET. The current
limit is has a fixed threshold voltage across the current sense resistor, thus set the current limit by choosing the proper value current
sense resistor.
The boost regulator includes an output over-voltage fault monitor that indicates a fault when the voltage at FB exceeds the 2.8V overvoltage protection (OVP) threshold. When an over-voltage fault occurs FLTB sinks current to GND to indicate that a fault has occurred.
OVP fault is non-latching, the fault clears when the over-voltage condition disappears.
8.7 LED Current Regulators and PWM Dimming Modes
The MSL3080 includes eight open-drain LED current regulators that sink LED current up to 60mA per channel and sustain up to 40V,
allowing them to drive up to 10 white LEDs each. The current regulators inform the Efficiency Optimizers, which in turn control the boost
regulator output voltage to minimize LED voltage while maintaining sufficient headroom for the LED current regulators.
Set the LED regulation current using a single resistor from ILED to GND. LED dimming is by PWM, and is by default controlled through
an external signal, or optionally by internal registers accessed through the I2C compatible serial interface (for interface information see
the “MSL3040/50/60/80/86/87/88 Programming Guide”). The drivers feature synchronized dimming, where all PWM dimming outputs
sink current in unison.
8.8 Efficiency Optimizer (EO)
The Efficiency Optimizer monitors the LED string drivers and controls the boost regulator output voltage to minimize LED current
regulator overhead voltage while maintaining sufficient voltage for accurate current regulation. The Efficiency Optimizer injects a current
into the boost regulator FB input node to reduce the boost regulator output voltage.
The Efficiency Optimizer has two modes of operation, initial calibration and auto calibration. Initial calibration happens at turn-on and
optimizes boost regulator output voltage. Auto calibration happens once per second to re-optimize the boost output voltage in response
to changing LED forward voltage due to aging or temperature effects.
8.9 Fault Monitoring and Auto-handling
The MSL3080 includes comprehensive fault monitoring and corrective action. The LED current regulators are monitored for LED string
open circuit and LED short circuit faults. It also monitors the boost regulator for output over-voltage. Strings with LED Short Circuit or
Open Circuit faults are turned off and ignored by the Efficiency Optimizer.
FLTB sinks current to GND when a fault is detected. The Boost Over-Voltage Fault does not latch, the fault goes away when the fault
condition no longer exists and FLTB is released; all other faults latch. Clear faults by toggling EN low and then high, or by cycling input
power off and on. Additionally, fault control is available through the I2C compatible serial interface; see the “MSL3040/50/60/80/86/87/88
Programming Guide” for information.
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
15
8.10 Internal Supervisory and LDO
The MSL3080 has a Power-On-Reset circuit that monitors VIN and allows operation when VIN exceeds 4.25V. The MSL3080 has built-in
LDOs that generate 2.5V to power the logic and oscillator sections. An integrated supervisor ensures that the LDO and internal oscillator
are stable before enabling the boost controller. The boost controller goes through a soft-start before the LED drivers are enabled.
8.11 Internal Oscillator
The MSL3080 includes a 20MHz internal oscillator that is divided down to drive the boost controller, and the LED PWM engine. The
oscillator is factory trimmed. Contact the factory if required to change the 20MHz default oscillator frequency; available frequencies fall
between 16MHz and 24MHz.
8.12 Over Temperature Shutdown
The MSL3080 includes automatic over-temperature shutdown. When the die temperature exceeds 135°C, the driver turns off, as if EN
is pulled low, and is held off until the die temperature drops below 120°C, at which time it turns back on. While MSL3080 is in overtemperature shutdown the onboard regulators are off, register values reset to their power-on default values, and the serial interface is
disabled.
8.13 Power Saving Modes
The MSL3080 has 3 primary power save modes available through the I2C compatible serial interface. See the
“MSL3040/50/60/80/86/87/88 Programming Guide” for information.
8.14 I2C Serial Interface and Driver Control
The I2C serial interface, whose use is optional, allows control of PWM dimming, fault monitoring, and various other control functions. For
a detailed explanation of interface operation see the “MSL3040/50/60/80/86/87/88 Programming Guide”.
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
16
9.0 Application Information
9.1 Bypassing VIN and PVIN
Bypass VIN with a capacitor of at least 1µF. Bypass PVIN to PGND with at least 2µF. Place all bypass capacitors close to the MSL3080.
9.2 Setting the LED Current
Set the on-current for all LED strings with a resistor from ILED to GND. Choose the resistor using:
where ILED is the LED full-scale current in Amps.
The maximum LED current per-string is 60mA. Driving all eight strings with 60mA at high duty cycles and elevated ambient temperatures
requires proper thermal management to avoid over-temperature shutdown. Connect the exposed pad (EP) to a large copper ground
plane for best thermal and electrical performance.
9.3 Fault Monitoring and Automatic Fault Handling
The MSL3080 monitors the LED strings and boost regulator output voltage to detect LED short-circuit, LED string open-circuit and Boost
Over-voltage faults. String faults latch the open drain fault output FLTB low. A boost over-voltage fault pulls FLTB low but does not latch.
When shorted LEDs are detected in a string, the driver disables and the Efficiency Optimizer stops monitoring it. The MSL3080 flags
these strings as faults in registers 0x05 through 0x08, pulls FLTB low and recalibrates the LED power supply voltage. Set the short circuit
voltage threshold with a resistor between SCTH and GND, as explained in the section “Setting the LED Short-Circuit Threshold”
beginning on page 17. For information about the fault registers and the I2C compatible serial interface see the
“MSL3040/50/60/80/86/87/88 Programming Guide”.
When an open circuit occurs, the Efficiency Optimizer detects a loss of current regulation which must persist for greater than 2 µs to be
detected. The minimum on-time for the strings is 2 µs. In this case the Efficiency Optimizer increases the LED voltage (boost regulator
output voltage), in an attempt to bring the LED current back in to regulation. This continues until the voltage is at the maximum level.
The MSL3080 then determines that any LED strings that are not regulating current are open circuit. It disables those strings, flags them
as faults in registers 0x05 through 0x08, pulls FLTB low and recalibrates the LED power supply voltage. When the boost regulator is at
its maximum value fictitious LED short circuit faults can occur. Toggle EN low and then high to clear all faults and return the MSL3080
to controlling and monitoring all LED strings. Fault conditions that persist re-establish fault responses. For information about the fault
registers and the I2C compatible serial interface see the “MSL3040/50/60/80/86/87/88 Programming Guide”.
9.4 Setting the LED Short-Circuit Threshold
When a given string, STRn, is sinking LED string current, the fault detection circuit monitors the STRn voltage. Typical optimized STRn
on-voltage is 0.5V. When one or more LED’s of a string are shorted, the STRn voltage increases above the nominal. When the voltage
is above the Short-Circuit Threshold the fault circuit generates an LED short circuit fault. In most cases, two LEDs in a string must be
shorted to cause a short circuit fault, but because LED VF differs for different LEDs, the number of shorted LEDs required to generate a
fault varies.Set the LED short-circuit threshold with a resistor from SCTH to GND using:
Table 9.1 Short Circuit Threshold Resistor
RSCTH
Threshold Voltage
1.0kΩ (or GND)
4.9V
27kΩ
5.8V
68kΩ
6.8V
330kΩ (or open)
7.6V
RSCTH is measured only at power up, and when EN is taken high, to set the threshold level. Additionally, register 0x04 holds the Short
Circuit Threshold level, changeable through the I2C compatible serial interface. For information about the Short Circuit Threshold register
and the serial interface see the “MSL3040/50/60/80/86/87/88 Programming Guide”.
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
17
Figure 9.1 Open-Circuit and Short-Circuit Detection Block Diagram
9.5 Boost Regulator
The boost regulator boosts the input voltage to the regulated output voltage that drives the LED anodes. The MSL3080 boost regulator
uses an external MOSFET switch and current sense resistor, allowing a wide variety of input/output voltage combinations and load
currents. The boost regulator switching frequency is 625kHz. Switching frequencies of 350kHz, 500kHz, 750kHz, 875kHz and 1Mhz are
also available; contact the factory for information.
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
18
9.6 The Efficiency Optimizer (EO)
MSL3050/MSL3060/MSL3080 Datashee
Prelimi
A voltage
the boost
regulator
output
voltage to FB
sets the
regulation voltage
(RTOP
8.1 oninto
page
14).
BOTTOM in Figure
power divider
supplyfrom
noise
rejection,
while
minimizing
power
dissipation.
It does
thisand
byRinjecting
a current
the
FB
The EO improves power efficiency by dynamically adjusting the power supply output voltage to the minimum required to power the LEDs.
256
steps
(8-bit
resolution).
This ensures that there is sufficient voltage available for LED current regulation, and good power supply noise rejection, while minimizing
power dissipation. It does this by injecting a current into the FB input over 256 steps (8-bit resolution).
input ov
When turned on, either by applying input voltage to VIN while EN is high, or by driving EN high with voltage applied to
When
on, either
by applying
voltage to cycle
VIN while
is high, or by
high with
voltage applied
VIN,
the EO regulators
begins
VIN,turned
the EO
begins
an initialinput
calibration
by EN
monitoring
thedriving
LED EN
current
regulators.
If alltothe
current
anmaintain
initial calibration
cycle by monitoring
thethe
LED
current
regulators.
current regulators
maintain
LED current
regulation
theAfter
EO the 4ms
LED current
regulation
EO
output
currentIf all
is the
increased
to reduce
the boost
output
voltage.
output current is increased to reduce the boost output voltage. After the 4ms power supply settling time, it rechecks the regulators, and
power supply settling time, it rechecks the regulators, and if they continue to maintain regulation the process repeats u
if they continue to maintain regulation the process repeats until one or more current regulator loses regulation. This step requires that
or more
current
regulation.
This
step requires
thatdecreases
the strings
are turned
for a minimum
of 3 µs
theone
strings
are turned
on forregulator
a minimumlooses
of 2 µs to
detect current
regulation.
The EO then
the output
currenton
to increase
boost
detect
current
regulation.
EOheadroom
then decreases
the
outputwith
current
to power
increase
boost The
output
voltage,
giving the regula
output
voltage,
giving
the regulatorThe
enough
to maintain
regulation
minimal
dissipation.
oscilloscope
picture
1 second, and
at any
time increases
the boost
voltage
Figure
9.2 shows
this procedure.
The EO
automatically
re-calibrates
enough
headroom
to maintain
regulation
with
minimal Vpower
dissipation.
The
oscilloscope
picture
Figure
7 shows this
OUT every
when
detects anThe
LED EO
stringautomatically
with insufficient re-calibrates
current.
procedure.
VOUT every 1 second, and at any time increases the boost voltage when
detects an LED string with insufficient current.
Figure 9.2 Efficiency Optimizer (EO)
Figure 7. Efficiency Optimizer (EO)
SETTING THE BOOST REGULATOR OUTPUT VOLTAGE
Select the voltage divider resistors (RTOP and RBOTTOM in Figure 5 on page 14) to set the boost regulator output voltage
first determining VOUT(MIN) and VOUT(MAX), the required minimum and maximum LED string anode power supply (boost
regulator) voltage, using:
MSL3050/60/80 preliminary datasheet revision 0.1
© Atmel Inc., 2011. All rights reserved.
Page 19 of 24
Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
19
OUT ( in
MAX
MAX total
)
LEDs
a) string,f (the
minimum and maximum voltage drop across a string is 35V and 38V. Adding allowance of 0.
for the current regulator headroom brings VOUT(MIN) to 35.5V and VOUT(MAX) to 38.5. Next determine RTOP using:
where Vf(MIN) and Vf(MAX) are the LED’s minimum and maximum forward voltage drops at the full-scale current set by RI
(page 14).
For( MAX
example,
if the LED minimum forward voltage is Vf(MIN) = 3.5V and maximum is Vf(MAX) = 3.8V, using 10
VOUT
)  VOUT ( MIN )
.
RTOP in a string, the total
LEDs
6 minimum and maximum voltage drop across a string is 35V and 38V. Adding allowance of 0

365
10
for
the
current
regulator
headroom
VOUT(MIN) to 35.5V and VOUT(MAX) to 38.5. Next determine RTOP using:
9.7 Setting the Boost Regulator Outputbrings
Voltage
MSL3050/M
MSL3050/MSL3060/MSL3080 Datash
Pr



Then the
determine
Select
voltage divider
resistors
(RTOP and RBOTTOM in Figure 8.1 on page 14) to set the boost regulator output voltage by first
BOTTOM
VVOUT ( MAXRand
VOUTusing:
VOUT ( MIN
V f ( MIN
# ofLEDs
0.5 , and
) V
( MIN )
anode
supply
regulator)voltage,
determining
) power
)  (boost
OUT(MIN)
OUT(MAX), the required minimum and maximum LED string


.
R
TOP
6
using:
365  10
2.5

V
 .0.5 ,
( MAX ) RV f (
MAX )  # ofLEDs 

ROUT
BOTTOM
TOP

  0.5 , and
VOUT ( MIN)  V OUT

#
ofLEDs

2
.
5
f ( MIN
)
(MAX )



VOUT ( MAX )  V f ( MAX )  # ofLEDs  0.5 ,
and
Then determine RBOTTOM using:
where Vf(MIN) and Vf(MAX) are the LED’s minimum and maximum forward voltage drops at the full-scale current set by RI
and
Vf(MAX)
are
minimum
and max
V=f(MIN)
3.5V
and
maximum
Vf(MAX)
= 17).
3.8V, using
10
(pageVf(MIN)
14).and
ForVf(MAX)
example,
the
minimum
voltage
iswhere
Vf(MIN)at
where
are theifLED’s
and maximum
voltage
drops
the
full-scale
current
set the
byis
RLED’s
(page
ILED
V
 LED
#minimum
ofLEDs
 0forward
.5 , forward
OUT ( MAX )  V f ( MAX2) .5
(page
16).
For
example,
if
the
LED
minimum
forward
volt
=
3.5V
and
maximum
is
V
=
3.8V,
using
10
LEDs
in
a
string,
the
total
For
example,
if
the
LED
minimum
forward
voltage
is
V
f(MIN)
f(MAX)
LEDs
in
a
string,
the
total
minimum
and
maximum
voltage
drop
across
a
string
is
35V
and
38V.
Adding
allowance
of
0
 RTOP 
.
R BOTTOM
minimum
and maximum
voltage
drop across
a string V
is 35V and to
38V.
Addingand
allowance
ofa0.5V
for
the
current
regulator headroom
brings
LEDs
in
string,
the
total
minimum
and
maximum
voltag

2
.
5
V
35.5V
V
to
38.5.
Next
determine
R
using:
for
the
current
regulator
headroom
brings
OUT(MIN)
OUT(MAX)
TOP
OUT AND
(MAX ) OUTPUT CAPACITORS
COUT(MIN)
HOOSING
THE
NPUT
V
to 35.5V
andIV
to 38.5.
RTOP using:and maximum
and
Vf(MAX)
areNext
thedetermine
LED’s minimum
voltage drops
at the brings
full-scale
currenttoset
where
Vf(MIN)
OUT(MAX)
35.b
for the forward
current regulator
headroom
VOUT(MIN)
3.5Vregulator
and maximum
is Vf(MAX)
3.8V,
using
(page
16).
For example,
the LED
forward
voltage
is V
The input
and
output
capacitorsif carry
the minimum
high frequency
current
due
tof(MIN)
the =boost
switching.
The =input
capac
 VOUT
VOUT ( MAX
)frequency
) minimum
a string,
the( MIN
total
maximum
dropvoltage
across
a
string
is
35V and
38V. Adding
prevents
current
travelling
back voltage
to the input
source,
reducing
conducted
andallowance
radiated
VOUT ( MAX
 thisinhigh
 . from and
RTOP LEDs
)  VOUT ( MIN )
6
to 35.5V
and
VOUT(MAX)
to
38.5.
Next
determine
Rprevents
current
regulator
headroom
VOUT(MIN)
noise. for
Thethe
output
prevents
highbrings
frequency
current
to R
the
load,
in
this
case
the
LEDs,
and
also
TOP using:


,
 10
365capacitor
TOP
6
CHOOSINGand
THE
INPUTnoise.
AND O
UTPUT
CAPACITORS
 10boost
conducted
radiated
The
output
capacitors also have a large effect365
on the
regulator loop stability and
-6
Where
350
xresponse,
10 isV
the
maximum
EO
output
current.
transient
and
so
are
critical
to
optimal
boost
regulator
operation.

V
The
and
output
capacitors
carry
the
high
frequency
current
due
to
the
boost
regulator
switching. The input capac
using:
Theninput
determine
R
BOTTOM
OUT ( MAX )
OUT ( MIN )
-6
high frequency current
 , travelling back to theWhere
RTOP
is the reducing
maximumconducted
EO outputand
current.
3.65x10source,
prevents
this
from
input
voltage
radiated
6
Then determine RBOTTOM 365
using: 10
noise. The output capacitor
high frequency current to the load, in this case the LEDs, and also prevents
2.prevents
5
using:
determine
RBOTTOM
 and
 . CAPACITORS
RHOOSING
R
conducted
radiated
output
capacitors also haveThen
a large
effect on
the boost
regulator loop stability and
C
THE
INPUT
AND OThe
UTPUT
-6 noise.
BOTTOM
TOP
is(MAX
the
maximum
outputboost
current.
Where
3.65x10
2.5 toEO
V
transient
response,
and
are
optimal
regulator
operation.
OUTso
) critical
Use ceramic input and output capacitors that keep their rated capacitance values at the expected operating voltages. T



.5
TypicalThen
Application
Circuit
on page
10 shows recommended values
for and
LEDs and2120mA
per
using:
determine
RBOTTOM
 R10
 ,string. Use a bulk
R BOTTOM
TOP 
electrolytic
capacitor
where
power
enters
the
circuit
board.

2
.
5
V
OUT (MAX )
9.8 Choosing the Input and output Capacitors
where 2.5V is the internal reference voltage.
CHOOSING THE INPUT AND OUTPUT CAPACITORS
2.5
CHOOSING
THE
IR
NPUT
ANDthe
Ohigh
UTPUT
Cthat
APACITORS
, keepdue
capacitors
carry

Rand
The
input
output
frequency
current
to the
boostcapacitance
regulator
switching.
input
prevents
this highvoltages. T
Use
ceramic
input
and
capacitors
their
rated
values
at
thecapacitor
expected
operating
BOTTOM
TOP output
where
2.5V
is
theThe
internal
reference
voltage.

2
.
5
V
frequency
current
from
travelling
back
to
the
input
voltage
source,
reducing
conducted
and
radiated
noise.
The
output
capacitor
prevents
OUT
(MAX
)
Typical
Application
Circuit
on
page
10
shows
recommended
values
for
and
10
LEDs
and
120mA
per
string.
Use capac
a bulk
C
HOOSING
THE
I
NDUCTOR
The input and output capacitors carry the high frequency current due to the boost regulator switching. The high
input
frequency current to the load, in this case the LEDs, and also prevents conducted and radiated noise. The output capacitors also have a large
electrolytic
capacitor
where
power
enters
the
circuit
board.
prevents
this
high
frequency
current
from
travelling
back
to
the
input
voltage
source,
reducing
conducted
and
radiated
The boost
regulator
inductor
takes
current
from and
thesoinput
source
and directs
that current
to the load. Using the prop
effect
on the boost
regulator
loop stability
andthe
transient
response,
are critical
to optimal
boost regulator
operation.
Regulator
Components
2.5V to
is
the internal
reference
noise.where
The
output
capacitor
prevents
high voltage.
frequency
toOther
theinductor
load,Boost
inwith
this sufficient
case
the LEDs,
and
also
prevents
inductor
is critical
proper
boost
regulator
operation.current
Choose
an
inductance
to keep
the induct
Use
the
component
values
shown
in
the
Typical
Applicat
conducted
and
radiated
noise.
The
output
capacitors
also
have
a
large
effect
on
the
boost
regulator
loop
stability
and
Use
ceramic
input
and
output
capacitors
that
keep
their
rated
capacitance
values
at
the
expected
operating
voltages.
The
Typical
ripple current within limits, and with sufficient current handling capability for steady-state and transient conditions.
Application
Circuit
onIpage
10so
shows
values for
and 10regulator
LEDs and
60mA
perrequired
string. Useuse
a bulk
electrolytic
capacitor
where in the fol
design
is
the
guidelines
presented
transient
response,
and
arerecommended
critical to optimal
boost
operation.
C
HOOSING
THE
NDUCTOR
Other
Boost
power enters
the circuit
board. Regulator Components
The
causes
current
inductor.
The current
rises during
on-time
The boost
boost regulator
regulator switching
inductor takes
theripple
current
from through
the inputthe
source
and directs
that current
to thethe
load.
Usingand
the falls
prop
Use the component values shown in the Typical Applications
Circuits THE
beginning
page
10. When
custom boost
C
HOOSING
INPUTonAND
OUTPUT
Ckeep
APACITORS
during
the
off
time.toThe
slope
of the
inductoroperation.
current is Choose
a function
of
the voltage
across
the
inductor,
and
so
the
total
inductor
is
critical
proper
boost
regulator
an
inductor
with
sufficient
inductance
to
the
induct
9.9 Choosing
the Inductor
design
is required
use the
guidelines
presented in the following sections.
CHOOSING
THE
INPUT
Owith
UTPUT
CAPACITORS
the
current
slope
multiplied
the time
in input
that phase
(on time,
tON
, ortransient
off time,
thigh
InPrelimina
steadychange
in current,
∆Ilimits,
ripple
current
within
and
sufficient
current by
handling
capability
for steady-state
and
L, is AND
OFF). frequency
The
and
output
capacitors
carry
theconditions.
state,
where
the
load
current,
input
voltage,
and
output
voltage
are
all
constant,
the
inductor
current
does
not
change
The
regulator
inductor
the current
from the
inputkeep
source
and directs
current to
the
load. Using
the expected
proper
inductor
is critical
prevents
this
high
frequency
current
from
travelling
backoT
Useboost
ceramic
input
andtakes
output
capacitors
that
their
rated that
capacitance
values
at the
operating
voltages.
C
HOOSING
THE
I
NPUT
AND
O
UTPUT
C
APACITORS
V

V
to
proper
boost
regulator
operation.
Choose
an
inductor
with
sufficient
inductance
to
keep
the
inductor
ripple
current
within
limits,
and
with
one
cycle,
and
so
the
amount
the
current
rises
during
the
on
time
is
the
same
as
the
amount
the
current
drops
during
The
boost
regulator
switching
causes
ripple
current
through
the
inductor.
The
current
rises
during
the
on-time
and
noise.for
The
output
capacitor
prevents
high
frequency
curr
OUT
IN
Typical
Application
Circuit on page 10 shows recommended values
and
10 LEDs
and 120mA
per
string.
Use a falls
bulkt
, the
D time.
sufficient
current
handling
capability
forof
steady-state
and
transient
conditions.
off
Calculate
duty
cycle
(equal
to
the
on-time
divided
by
the
switching
period)
using:
The
input
and
output
capacitors
carry
the
high
frequency
current
due
to
the
boost
regulator
switching.
The
input
c
during
the
off
time.
The
slope
the
inductor
current
is
a
function
of
the
voltage
across
the
inductor,
and
so
the
total
conducted
and
radiated
noise.
The
output
capacitors
also
electrolytic
VINcapacitor where power enters the circuit board.
prevents
this∆I
high
frequency
current
from
travelling
back
to
the
input
voltage
source,
reducing
conducted
and
radi
,
is
the
current
slope
multiplied
by
the
time
in
that
phase
(on
time,
t
,
or
off
time,
t
).
In
steady
change
in
current,
transient
response,
and
so
are
critical
to
optimal
boost
re
L causes ripple current through the inductor. The current rises during the on-time and falls
ON during the off time.
OFF
The boost regulator switching
noise.
The
output
capacitor
high
frequency
current
toall
the
load,
in the
this
case ΔI
the
LEDs, and
state,
where
the
load
current,
inputprevents
voltage,
and
output
voltage
are
constant,
inductor
current
doesalso
not prevents
change o
V

V
The
slope
of
the
inductor
current
is
a
function
of
the
voltage
across
the
inductor,
and
so
the
total
change
in
current,
L, is the current slope
OUT
IN
output
voltage
and V
the input
voltage.also have a large effect on the boost regulator loop stability
where
VOUT is the,and
IN isoutput
D cycle,
conducted
radiated
noise.
The
capacitors
one
and
so
the
amount
the
current
rises
during
the
on
time
is
the
same
as
the
amount
the
current
drops
during t
,
or
off
time,
t
).
In
steady-state,
where
the
load
current,
input
voltage,
and
output
voltage
multiplied
by
the
time
in
that
phase
(on
time,
t
ON
OFF
CHOOSING
THE INDUCTOR
VIN the
transient
response,
sonot
are
critical
toone
optimal
boost
regulator
operation.
are
constant,
inductor
does
change
cycle, and
so the
amount
current
rises
duringAND
the onO
time
is the same
as
off all
time.
Calculate
the current
dutyand
cycle
(equal
toover
the
on-time
divided
by
the the
switching
period)
using:
C
HOOSING
THE
I
NPUT
UTPUT
C
APACITORS
Calculate
the
on-time
induring
seconds
The
boost
regulator
inductor
takes
theCalculate
currentthe
from
and directs
that
the using:
load. Using the prop
the
amount
the
current
drops
the
offusing:
time.
dutythe
cycleinput
(equalsource
to the on-time
divided by
the current
switching to
period)
ceramicwith
inputsufficient
and output
capacitors
their r
inductor
is critical
to proper
boostand
regulator
operation.
ChooseUse
an inductor
inductance
to that
keepkeep
the induct
is
the
output
voltage
V
is
the
input
voltage.
where
V
OUT
IN
Vcurrent
OUT  Vwithin
IN
Typical
Application
Circuit
on
page
10
shows
recommend
ripple
limits,
and
with
sufficient
current
handling
capability
for
steady-state
and
transient
conditions.
 VININPUT AND OUTPUT CAPACITORS
V , THE
D fD
HOOSING
where
theOUT
boost regulator
switching frequency.
t ON  C
,
SWVis
electrolytic capacitor where power enters the circuit boar
Calculate
the
IN on-time in seconds using:

f
V
f
Use
ceramic
input
and
output
capacitors
that keep
theirthe
rated
capacitance
valuesrises
at the
expected
operating
SW regulator
IN
SW
The
boost
switching
causes
ripple
current
through
inductor.
The
current
during
the on-time
andvoltag
falls
where VOUT is the output voltage and VIN is the input voltage. Calculate the on-time
in seconds
using:
Typical
Application
Circuit
on
page
10
shows
recommended
values
for
and
10
LEDs
and
60mA
per
string.
Use a
Calculate
the
inductor
ripple
current
using:
during
the
off
time.
The
slope
of
the
inductor
current
is
a
function
of
the
voltage
across
the
inductor,
and
so
the
total
thecapacitor
output
and
VIN enters
is the input
voltage.
whereelectrolytic
VD
 V INvoltage
OUT is V
where
power
the circuit
board.
the OUT
boost
switching
frequency.
where
fSW
is the
slope
multiplied
by the
time
in that phase
time, tON, or off time, tOFF). In steady
change
iniscurrent,
∆IL,regulator
CHOOSING
THE(on
INDUCTOR
, current
t ON 

V
t
V
V
V
f
V

f
state,
where
the
load
current,
input
voltage,
and
output
voltage
are
all
constant,
the
inductor
current
notfrom
change
IN
ON
IN
OUT
IN
SW
IN
SW
The boost regulator inductor
takes
the does
current
the ino
Calculate
the on-time in seconds using:
, rises during the on time
I L cycle,the
Calculate
inductor
ripple
current
using:
one
and
so
the
amount
the
current
is
the
same
as
the
amount
the
current
drops
during
inductor
is
critical
to
proper
boost
regulator
operation.
Ch
V INDUCTOR
f SW frequency.
L
where fSW is theLboost regulator
switching
Calculate the inductor ripple current using:
CHOOSING
off time.
Calculate THE
the OUT
duty cycle
(equal to the on-time divided ripple
by thecurrent
switching
period)
using:
within
limits,
and
with
sufficient
current
han
Page 18 of 22
VD

t ONVOUT
VINVVINOUT
The
regulator
inductor
the current from the input source and directs that current to the load. Using the
,  VIN takes
twhere

IN boost
ON
©
Inc.,
2011.
All
rights
reserved.

IAtmel


,
Lf is the
value inboost
Henrys.
Choose
a value for
L thatan
produces
awith
ripple
currentinductance
in the range of
25%the
to in
5
L V
V critical
Vf SWto
inductor
is
regulator
operation.
Choose
inductor
sufficient
keep
 Vinductance
The boost
regulator
switching
causes ripple to
current
throu
SW L
OUT
IN IN DC
 proper
f SW current.
L
ofDthe
state
steadycurrent
state DC
inductor
current is
equal
to the input
current.
Estimate
the
INinductor
 steady
, within
ripple current
limits,
and withThe
sufficient
handling
capability
for
steady-state
and
transient
conditions.
during the off time. The slope of the inductor current is a
where
L is the
in Henrys.
Choose a value for L that produces a ripple current in the range of 25% to 50% of the steady
VINinductance
steady-state
DC inputvalue
current
using:
is the current
slope
multiplied by t
change
in current,
∆I
L,steady-state
state
DC
inductor
current.
The
steady
state
DC
inductor
current
is
equal
to
the
current.
Estimate
the
input
current
where L is the inductance value in Henrys. Choose a value
Linput
that
a ripple
current inDC
the
range
ofon-time
25% toand
50
Pagefor
18 of
22theproduces
inductor.
theand
state,
where
the The
load current
current,rises
inputduring
voltage,
output v
using: The boost regulator switching causes ripple current through
©
Atmel
Inc.,
2011.
All
rights
reserved.
of
the
steady
state
DC
inductor
current.
The
steady
state
DC
inductor
current
is
equal
to
the
input
current.
Estimate
the
the
output
andofVthe
the input
voltage.
whereduring
VOUT isthe
time. voltage
The slope
current
is a one
function
of and
the voltage
across the current
inductor,rises
andduring
so thethe
to
IN isinductor
Voff
cycle,
so the amount
OUT 
steady-state
, ∆IL, isusing:
in input
I IN  change
I LOAD DC
the current slope multiplied by the
time in
that phase
time,
tON(equal
, or offtotime,
tOFF). In st
current,
current
off time.
Calculate
the(on
duty
cycle
the on-time
di
 V INtheinload
Calculate
thewhere
on-time
seconds
using:
state,
current,
input voltage, and output voltage are all constant, the inductor current does not cha
where ILOAD is the sum of all strings steady-state LED currents with all LEDs on simultaneously, VOUT is the maximum (un-optimized)
one cycle,Vand
so the amount the current rises during the on time is the same as the amount the current drops du
OUT
boost regulator output
voltage, and VIN is the minimum boost regulator input voltage.
, the
I IN off
IILOAD
time.
Calculate
duty cycle
(equal to the
divided
byLEDs
the switching
period)
is
the
sum
all strings
steady-state
LEDon-time
currents
with all
on simultaneously,
VOUT0.1
is the maximumPa(
where
LOAD
VOUT
 Vof
D
MSL3050/60/80
preliminary
datasheetusing:
revision
IN
Vregulator
IN
,
t ON 

Atmel
MSL3080
Datasheet
boost
regulator
input
voltage.
optimized)
boost
output
voltage, and VIN is the minimum
© Atmel Inc., 2011. All rights reserved.
20
MSL3050/MSL3060/MSL3080 Datashee

f SW
V IN  f SW

8 String 60mA LED Driver with Integrated Boost Controller
is the
sum
of all
steady-state
LED currents
with20all
LEDs
on simultaneously,
VOUT
is the
where
ILOAD
Inductors
have
two
types
of strings
maximum
current
RMS Page
current
and
current. Make
sure
thatmaximum
the peak (un
MSL3050/60/80
preliminary
datasheet
revision
0.1 ratings,
of
24 saturation
minimum
boost
regulator
input
voltage,
and n iswhich
the boost
regulator
optimized)
boost
voltage, Vcurrent
© Atmel
Inc.,
2011.
All output
rights
reserved.
inductor
current
isregulator
less than
the saturation
Note
that
during
load
current
transients,
occur
whenev
IN is therating.
Page 18 of 22
Inductors have two types of maximum current ratings, RMS current and saturation current. Make sure that the peak inductor current is
less than the saturation current rating. Note that during load current transients, which occur whenever the LEDs are turned on or off (due
to PWM dimming), the inductor current may overshoot its steady state value. How much it overshoots depends on the boost regulator
loop dynamics. If unsure of the loop dynamics, a typical value to use for the overshoot is 50% of the steady-state current. Add half of the
inductor ripple current to this value to determine the peak inductor current. With inductor ripple current in the 25% to 50% range, estimate
the inductor RMS current as 115% of the DC steady state inductor current.
9.10 Setting the External MOSFET Current Limit
The current sense resistor, connected from the switching MOSFET source to GND, sets the boost regulator current limit. The cycle-bycycle current limit turns-off the boost regulator switching MOSFET when the current sense input detects instantaneous current above the
current limit threshold. This causes the current to drop until the end of the switching cycle. The current limit threshold is 100mV typical,
and 75mV minimum. Choose the current sense resistor value to set the current limit using:
where IL(MAX) is the maximum inductor current. When RCS is not equal to a standard 1% resistor value use the next lower value.
9.11 Choosing the Switching MOSFET
The MSL3080 uses an external logic level MOSFET to drive the boost converter. Choose a MOSFET that can pass at least twice the
peak inductor current, and that minimizes simultaneously both the MOSFET on-resistance, RDSon, and gate charge for fast switching
speed. Make sure that the MOSFET drain-source voltage rating is above the maximum un-optimized boost output voltage, with some
extra margin for voltage overshoot due to excess circuit board stray inductance and output rectifier recovery artefacts. Assure that the
MOSFET is heat sunk to withstand the worst-case power dissipation while maintaining die temperature within the MOSFET ratings.
9.12 Choosing
Outputand
Rectifier
Place the the
MOSFET
rectifier close together and as close to the output capacitor(s) as possible to reduce circuit boa
radiated
emissions.
The
output
passesand
the inductor
the outputand
capacitor
and load
during
the switching
off-time.as
Duepossible
to the hightoboost
Place
therectifier
MOSFET
rectifiercurrent
closetotogether
as close
to the
output
capacitor(s)
reduce circuit boa
regulator switching frequency use a Schottky rectifier. Use a Schottky diode that has a current rating sufficient to supply the load
radiated
emissions.
Place
the
and
rectifier
close
together
as close
the output
capacitor(s)
possible
to reduce circuit boa
current,
aMOSFET
voltage rating
higher
than the
maximum
boostand
regulator
outputto
voltage.
Schottky
rectifiers haveas
very
low on voltage
L
OOPand
COMPENSATION
radiated
emissions.
and
fast switching
speed, however at high voltage and temperatures Schottky leakage current can be significant. Make sure that the
Use a power
RC network
from
COMPspecifications.
to FB to compensate
the MSL3040/41
regulation
loop
3 on
page 12). Th
rectifier
dissipation
is within
the rectifier
Place the MOSFET
and rectifier close
together and
as (Figure
close to the
output
LOOPseries
COMPENSATION
regulationas
loop
dynamics
are
sensitive
to output
capacitor and inductor values. To begin, determine the right-half-plan
capacitor(s)
possible
to reduce
circuit
board radiated
emissions.
L
OOP
COMPENSATION
Use
a
series
RC network from COMP to FB to compensate the MSL3040/41 regulation loop (Figure 3 on page 12). Th
zero
frequency:
regulation
loop
are sensitive
output
capacitor and
values.
To begin,
determine
Use Compensation
a series RCdynamics
network from
COMP totoFB
to compensate
theinductor
MSL3040/41
regulation
loop
(Figure 3the
onright-half-plan
page 12). Th
9.13 Loop
zero
frequency:
2
regulation
loop dynamics
are sensitive to output capacitor and inductor values. To begin, determine the right-half-plan
V INnetwork fromRCOMP
Use
RC
LOAD to FB to compensate the MSL3080 regulation loop (Figure 8.1 on page 14). The regulation loop
zero
frequency:
,
f a series
RHPZ are sensitive2to output capacitor and inductor values. To begin, determine the right-half-plane zero frequency:
dynamics
L
VVOUT
R2LOAD
IN
2
,
f RHPZ
R2LOAD
IN
L ,
VVOUT
f
x
RHPZ R
is the minimum equivalent load resistor, or
where
=LOAD
2L
VOUT
is the minimum equivalent load resistor, or
where R
equivalent load resistor, or
where
.
R LOAD RLOAD is the minimum
LOAD
where RLOAD
is V
the
minimum equivalent load resistor, or
OUT
I OUT
V (MAX )
R LOAD  VOUT .
OUT
(MAX ) .
 I OUT
R LOAD
The
output
capacitance
and type of capacitor affect the regulation loop and method of compensation. In the case of
I
OUT
(MAX )the zero caused by the equivalent series resistance (ESR) is at such a high frequency that it is not
ceramic capacitors
The output capacitance and type of capacitor affect the regulation loop and method of compensation. In the case of ceramic capacitors
The
output
capacitance
and
type
of capacitor
affect
thearegulation
method
ofso
compensation.
In the case
the
zero
caused
byIn
the
equivalent
resistance
is at such
high frequency
thatand
it issignificant,
not
of consequence.
In be
the considered
case of
consequence.
the
case
ofseries
electrolytic
or(ESR)
tantalum
capacitors
the loop
ESR
is
must
whenof
electrolytic
or
tantalum
capacitors
the
ESR
is
significant,
so
must
be
considered
when
compensating
the
regulation
loop.
Determine
the
ceramic
capacitors
the
zero
caused
by
the
equivalent
series
resistance
(ESR)
is
at
such
a
high
frequency
that
it isofnot
The output capacitance
and type
capacitor the
affect
thezero
regulation
loopby
and
of compensation. In the case
compensating
the regulation
loop.ofDetermine
ESR
frequency
themethod
equation:
ESR
zero frequency
the
equation:
consequence.
Inbythe
case
ofcaused
electrolytic
or tantalum
capacitors
the ESR(ESR)
is significant,
so amust
considered
ceramic
capacitors
the
zero
by the
equivalent
series resistance
is at such
highbe
frequency
thatwhen
it is not
compensating In
thethe
loop. Determine
the ESR
zero frequency
byisthe
equation:so must be considered when
consequence.
case of electrolytic
or tantalum
capacitors
the ESR
significant,
1regulation
f ESRZ 
compensating
the regulation loop. Determine the ESR zero frequency by the equation:
2  ESR
1  C OUT
f ESRZ 
1 ofthe
2isthevalue
ESR
C OUT
where
output capacitor, and ESR is the Equivalent Series Resistance of the output capacitor. Assure that the loop
f ESRZCOUT
OUT
is the value
of
the output capacitor, and ESR is the Equivalent Series Resistance of the output capacitor.
where
C
crossover frequency
is at 
least
1/5th of the ESR zero frequency.
2


ESR
C
OUT
Assure that the loop crossover frequency is at least 1/5th of the ESR zero frequency.
where COUT is the value of the output capacitor, and ESR is the Equivalent Series Resistance of the output capacitor.
th
th
of
the
ESR
zero
Assure
loop
crossover
frequency
is at least
1/5
is the
value
of the
output
capacitor,
and
ESR
isthe
thelower
Equivalent
Series
Resistance
the output capacitor.
where
Cthat
OUT the
of
of thefrequency.
ESR zero
fESRZ, theofright-half-plane
zero fRH
Next
determine
the
desired
crossover
frequency
as 1/5
th
of
the
ESR
zero
frequency.
Assure
that
the
loop
crossover
frequency
is
at
least
1/5
or the switching frequency fSW. The crossover frequencyth equation is:
Next determine the desired crossover frequency as 1/5 of the lower of the ESR zero fESRZ, the right-half-plane zero fR
. The crossover
frequency
is: of the ESR zero fESRZ, the right-half-plane zero fR
or
thedetermine
switching the
frequency
of the lower
Next
desiredfSW
crossover
frequency
as 1/5th equation





 equation
R
R
1
COMP
LOAD
.
The
crossover
frequency
is:
or
the
switching
frequency
f
Atmel MSL3080 Datasheet
SW
fC  


,
21
8 String 60mA LED Driver with Integrated Boost Controller
RCS  2  RLOAD
RLOAD
TOP  11
 RRCOMP
1  C OUT 
f C   R
   RLOAD   
 ,
1 C
RCOMP
11  RCS    2  RLOAD
TOP
OUT



 , voltage divider resistor (from the output voltage to FB), RCOMP


f
C
fC is the crossover

  RTOP is the top side
frequency,
where
crossover
is: zero frequency.
or
the switching
frequency
fSW. The
of the ESR
Assure
that the loop
crossover
frequency
is at frequency
least 1/5thth equation
of
the
lower
of the ESR
zero
fESRZ, theof
right-half-plane
zero fRH
Next
determine
the
desired
crossover
frequency
as
1/5
Series
Resistance
the output capacitor.
where COUT is the value of the output capacitor, and ESR is the Equivalent
th
.
The
crossover
frequency
equation
is:
orAssure
the switching
frequency
f
SW
thelower
ESR of
zero
the
1/5
 Rthat
 loop
 Rcrossover
 frequency
 th ofofthe
thefrequency.
ESR zero fESRZ, the right-half-plane zero fRH
Next determine
frequency
as 1/5
1is at least
COMP the desired
LOAD crossover
,



f

 . The
 crossover frequency
 thequation is:
orCthe switching frequency
fSW
 RCS crossover
TOP 
LOAD
 RRCOMP
11R
 2  Rfrequency
 of the lower of the ESR zero fESRZ, the right-half-plane zero fR
 the
Next determine
desired
as 1/5
1  C OUT
LOAD



f
Next
determine
the desired
as 1/5th offrequency
the lower
the ESR zero
C the
switching
 crossover
 , of equation
. The crossover
is:fESRZ, the right-half-plane zero fRHPZ or the
or
frequency
fSWfrequency
 Rfrequency
 fSW.11
LOAD
 Cis:OUT 
RCOMP
RCS  frequency
2  RLOAD
R
1
switching
The
crossover
equation
TOP

is
the
crossover
frequency,
R
is
the
top
side
voltage
divider
resistor (from the output voltage to FB), RCOMP
where
f
C
TOP
fC  


,
the resistor
of
the
series
RC
compensation
network.
Rearranging
the
factors
of this equation yields the solution for RCO



R
11
R
2

R
C
CS  
LOAD
OUT 
 RTOP   RLOAD
1
the crossover
frequency,
RTOP is the top side, voltage divider resistor (from the output voltage to FB), RCOMP
where
as:


f C  fC isCOMP
 
 

the resistor
network.
the factors of this equation yields the solution for RCO
 C OUTRearranging
R of the
RCS compensation
RLOAD
 series
11  RC
  2RTOP
 voltage divider
the crossover
frequency,
is the top
side
resistor (from the output voltage to FB), RCOMP
where fC is TOP
as:

RCOMP
R ofcrossover
 11
frequency,
RCSRC
 2compensation
RTOP
 isf Cthe top
C OUT
. voltage divider
the
resistor
the
series
network.
Rearranging
the the
factors
this equation
yields
solution
for RCO
side
resistor (from
outputof
voltage
to FB), RCOMP
is thethe
resistor
of
where
fC is theTOP
iscompensation
the crossover
frequency,
RTOP
the top
side
voltage
divider
resistor
the output voltage to FB), RCOMP
where
as:
the
seriesfC
RC
network.
Rearranging
theisfactors
of this
equation
yields
the solution
for R(from
COMP as:

Rthe
RTOP
 11
accurate
RCS RC
 2compensation
 f  C OUT network.
.
resistor
of the
series
Rearranging
of this equation
yields the
solution for RC
COMP
These
equations
are
if theCcompensation
zero
(formed bythe
thefactors
compensation
resistor R
COMP and the
as:
at a. lower frequency than crossover. Therefore the next step is to choose the
compensation

RCOMP RTOP capacitor
 11  RCSCCOMP
 2) happens
f C  C OUT
These
equations
are accurate
if the
compensation
zero
(formed
resistoror:
RCOMP and the
of the
the compensation
crossover frequency,
compensation
capacitor
such that
the
compensation
zero
is 1/5thby
)
happens
at
a
lower
frequency
than
crossover.
Therefore
the
next
step is to choose the
compensation
capacitor
C

R
R

11

R

2


f

C
.
COMP
These
equations
are accurate
if the
compensation
zero
by the(formed
compensation
resistor RCOMP and the
compensation
COMP
TOP
CS
C
OUT(formedzero
and the
These
equations
are accurate
if the compensation
resistor
RCOMPcapacitor
thby the compensation
of
the
crossover
frequency,
or:
compensation
capacitor
such
that
the
compensation
zero
is
1/5
CCOMP) happens
at
a
lower
frequency
than
crossover.
Therefore
the
next
step
is
to
choose
the
compensation
capacitor
such
that the
f C capacitor CCOMP
1
)
happens
at
a
lower
frequency
than
crossover.
Therefore
the
next
step
is to choose the
compensation
compensation
zero is 1/5th of the crossover frequency,
or:
fThese
.
COMPZ equations
are accurate
if the
bythe
thecrossover
compensation
resistor
frequency,
or:RCOMP and the
compensation
capacitor
such that
thecompensation
compensationzero
zero(formed
is 1/5th of
5
2

R
C
COMP
f C capacitorCOMP
1 ) happens
at a lower frequency than crossover. Therefore the next step is to choose th
compensation
CCOMP
fcompensation
.
COMPZ =
=capacitor such that the compensation
zero is 1/5th of the crossover frequency, or:
5
2

R
C
f
x
x
1
COMP
COMP
Solving
for CCCOMP:
fExample:
.
COMPZ
Solving for CCOMP
5 :
2
RCOMP
C COMP
1
C
:5
Solving
for CfCOMP
f COMPZ
.
As
an
example,
set
the
maximum
(un-optimized)
output voltage to 39V, using voltage divider as follows:
Example:
C
.
5
2

R
C
=
COMP
COMP
COMP
Example:
49.9k
RTOP =for
:
Solving
C
COMP
x
x
2 RCOMP
fC
5
= 3.40kset
RBOTTOM
Example:
C
.
As
an example,
the maximum
(un-optimized) output voltage to 39V, using voltage divider as follows:
COMP
As
an example,
(un-optimized) output voltage to 39V, using voltage divider as follows:
:5 the maximum
Solving
for
2CCOMP
Rset
fC
RTOP = 49.9k
COMP
Example:
=
49.9k
R
C
.
TOP
Let
theexample,
load current
be 800mA
maximum,
use 10uH
inductor,
output
a 12V as
input
voltage, a 12m R
an
set the
maximum
(un-optimized)
output
voltage
to 39V,
usingcapacitor,
voltage divider
follows:
COMP
Page
20 ofa2220F
RAs
BOTTOM =23.40k
2011.
R Allfrequency
=
3.40k
R
C(un-optimized)
BOTTOM
©
Atmel
5rightsfreserved.
and
the
switching
is 625kHz.
=Inc.,
49.9k
R
TOPexample,
As
an
set theCOMP
maximum
output voltage to 39V, using voltage divider as follows:
CBOTTOM
.
COMP = 3.40k
Page 20 of 22
R
Let
the load2current
be 800mA
maximum, use 10uH inductor,
a 20F output capacitor, a 12V input voltage, a 12m R
R
f
COMP
C
=the
49.9k
RLet
©
Atmel
Inc.,
2011.
All rights
reserved.
load
current
be
800mA
maximum,
use
10uH
inductor,
a 20F output capacitor, a 12V input voltage, a 12m R
TOP
V
V
39
and
the
switching
frequency
is
625kHz.
Page 20 of 22
OUT
=
3.40k
Rand
BOTTOM
the
switching
frequency
is
625kHz.
R


48
.
75

Let
the
load
current
be
800mA
maximum,
use
10uH
inductor,
a 20F output capacitor, a 12V input voltage, a 12m R
LOADInc., 2011. All rights reserved.
© Atmel
I LOAD frequency
0.8 A
and
the
switching
is
625kHz.
Let the load current be 800mA maximum, use 10uH inductor, a 20µF Page
output20
capacitor,
of 22 a 12V input voltage, a 12mΩ RCS, and the
V
39V
RLOAD


2
LOAD
IIVLOAD
AA  48.75 2 
039
..88V
OUT  0

V
48.75

12 
LOAD
IN
Rf LOAD 
 RLOAD
 48.75


 73kHz
RHPZ
I LOAD  0.8 A

6 
  39 
V
2
L

2

10

10

2






2
 OUT 
 V  2 R

48
  12  2 
48..75
75 6   73kHz
ffRHPZ   VININ  2   RLOAD
LOAD    12   
th  2 
39
1/5
RHPZ
 frequency
  73kHz
LL to
fRHPZ
: 2  10.
Set
the crossover
 R22LOAD
12
OUT
VVV



IN
39

10 75
10
10 6   73kHz

 2  48

f RHPZ   OUT   

6 
   
 2L to 1/5th39f  :  2  10  10 
VOUT  frequency
f RHPZ
Set the crossover
th RHPZ
fRHPZ:
Set
crossover
1/5
. fto

f Cthethe
 14frequency
.6kHz
Set
crossover
frequency
to 1/5th
:
RHPZ
5
Set the crossover frequency to 1/5th fRHPZ:
ffRHPZ

ffC calculate
RHPZ  14.6kHz .
Next
resistor value to achieve the 15kHz crossover frequency, or

14.6compensation
kHz .
C
55  the
f RHPZ

fC
 14.6kHz .
Next
calculate
compensation
value
the
15kHz
crossover
frequency,
RCOMP
5Rthe
 11
 RCSresistor
 2 
f C to achieve
Cvalue
.9k 
11the
 .025
 2crossover
 or15k  frequency,
20 F  25or.9k
Next
calculate
the
compensation
resistor
to49
achieve
15kHz
TOP
OUT 
VOUT
V reserved.
switching
frequency
is625kHz.
©
Inc.,
2011.
All39
rights
R Atmel
48.75
OUT






Next calculate the compensation resistor value to achieve the 15kHz crossover frequency, or
Next calculate the compensation resistor value to achieve the 15kHz crossover frequency,
or
the
compensation
zero
of.9the
crossover frequency, o
Then
compensation
R

RRTOP the
11
 RRCS  22  ffcapacitor,
C

49
..9,9kto
set
11
..025
 22 15
kk 
20
to
FF1/5
th25
COMP
COMPcalculate
C 
OUT C
R

11

C

49
k
11
025
15

20

25
.
9kk

COMP
TOP
CS
C
OUT
3kHz
RCOMP
 Rthe
 11  RCS capacitor,
 2  fCCCOMP
C
 49
.9k  11 zero
.025to1/5th
2 of 15
 20 Ffrequency,
th 25.9or
k3kHz
Then
calculate
, toOUT
set the
compensation
the kcrossover
TOPcompensation
Then calculate the compensation capacitor, CCOMP, to set the compensation zero to 1/5 th of the crossover frequency, o
Then calculate the compensation
capacitor,
1
1 CCOMP, to set the compensation zero to 1/5 th of the crossover frequency, o
3kHz
C COMPcalculate

.1nF
3kHz
the. compensation zero to 1/5 of the crossover frequency, o
Then
the compensationcapacitor, CCOMP,to2set
2

R

f
2

25
k

3
k


COMP
COMPZ
3kHz
1
11 resistors and compensation resistor/capacitors as close to the MSL3040/41
When
laying
out the circuit1board, place the
voltage divider
C


 22..11nF
.
COMP
 2 to25
asCpossible
trace
COMP
and
FB. nF .
COMP and
22minimize
 RRCOMP
 lengths
ffCOMPZconnected
k

3
k
1
1
2  the
25kvoltage
 3k divider
COMP
C COMPlaying
 out the
2.1nF resistors
.
When
circuitCOMPZ
board,place
and compensation resistor/capacitors as close to
2 as
 Rpossible
2 trace
25k lengths
 3k connected to COMP and FB.
MSL3040/41
minimize
COMP  fand
COMPZ
When laying out the circuit board, place the voltage divider resistors and compensation resistor/capacitors as close to
When laying out the circuit board, place the voltage divider resistors and compensation resistor/capacitors as close to
MSL3040/41
as possible
and minimize trace lengths connected to COMP and FB.
LED Dimming
Control
MSL3040/41
as possible
and
minimize
lengthsdivider
connected
to COMP
and FB.
When laying out
the circuit
board,
placetrace
the voltage
resistors
and compensation
resistor/capacitors as close to
MSL3040/41 as possible and minimize trace lengths connected to COMP and FB.
2
LED
Dimming
EXTERNAL
AND Control
IControl
C CONTROL OF LED BRIGHTNESS
LED
Dimming
Control
MSL3040 LED
brightness using Pulse Width Modulation (PWM) with a PWM signal applied to the external PW
LED
Dimming
Atmel MSL3080 Datasheet
2Control
input.
The PWM
signalsOF
(outputs)
take the frequency and8duty
cycle
the
signal
but are staggered
in t
22
E
XTERNAL
AND dimming
I
LED BRIGHTNESS
2C CONTROL
String 60mA
LEDof
Driver
withinput
Integrated
Boost Controller
E
XTERNAL AND I C CONTROL OF LED BRIGHTNESS
so
that
they
start
at
evenly
spaced
intervals
relative
to
the
PWM
input
signal.
When
one
or
more
strings
are
disabled
2
Control
MSL3040
LED
brightness
using
Pulse
Width Modulation (PWM) with a PWM signal applied to the external PWb
E
XTERNAL
AND
CC
ONTROL
LED
BRIGHTNESS
Control
MSL3040
brightness
using
Pulse
Width
Modulation
(PWM)
with a enabled
PWM signal
applied to the external PW
fault
response,
theILED
stagger
delaysOF
automatically
re-calculate
for the
remaining
strings.
input. The PWM dimming signals (outputs) take the frequency and duty cycle of the input signal but are staggered in ti
input.
The
PWM dimming
signals (outputs)
takeWidth
the frequency
and
duty cycle
the input
signal
but are
staggered
t
Control
MSL3040
LED brightness
using Pulse
Modulation
(PWM)
with aofPWM
signal
applied
to the
external in
PW
10.0 LED Dimming Control
10.1 External and I2C Control of LED Brightness
Control LED brightness using Pulse Width Modulation (PWM) with a PWM signal applied to the external PWM input. The LED PWM
dimming occurs at the same frequency and duty cycle as the input signal. For all drivers, use PWM input frequency between 20Hz and
50kHz and duty cycle between 0% and 100%. Additionally, internal registers, accessed using the I2C compatible serial interface, allow
control of the PWM dimming frequency and duty cycle. For programming details see the “MSL3040/50/60/80/86/87/88 Programming
Guide”.
11.0 Ordering Information
Table 11.1 Ordering Information
PART
MSL3080-IU
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San Jose, CA 95131
USA
Tel: (+1)(408) 441-0311
Fax: (+1)(408) 487-2600
www.atmel.com
DESCRIPTION
PKG
8-CH LED driver with integrated boost controller and resistor based LED Short Circuit threshold
setting, with single PWM input.
Atmel Asia Limited
Unit 01-5 & 16, 19F
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Fax: (+49) 89-3194621
24 pin
4 x 4 x 0.75mm
VQFN
Atmel Japan
9F, Tonetsu Shinkawa Bldg.
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Chuo-ku, Tokyo 104-0033
JAPAN
Tel: (+81)(3) 3523-3551
Fax: (+81)(3) 3523-7581
© 2012 Atmel Corporation. All rights reserved. / Rev.: MSL3080 Datasheet DBIE-20120814
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Atmel MSL3080 Datasheet
8 String 60mA LED Driver with Integrated Boost Controller
23