ATMEL MSL3085BT

Atmel LED Driver-MSL3085
8-string White and RGB LED Driver with Adaptive Power Control,
EEPROM, and I2C/SMBus Serial Interface
Datasheet Brief
Atmel LED Driver-MSL3085
8-string White and RGB LED Driver with Adaptive Power
Control, EEPROM, and I2C/SMBus Serial Interface
General Description
The Atmel LED DriverMSL3085 compact, highpower 8 LED strings controller
uses external MOSFETs to sink
up to 350mA per string, with
current accuracy and matching
better than ±1.5%. The
MSL3085 drives eight parallel
strings of LEDs, and offers fault
detection and management of
open and short circuit LEDs.
The MSL3085 features a 1MHz I2C serial interface. The interface supports
video frame-by-frame LED string intensity control for up to eight
interconnected devices, allowing active area dimming and phase shifted
PWM timing for video displays. It includes an advanced PWM engine that
synchronizes LED timing with the video signal for reduced motion blur and
waterfall noise.
The MSL3085 adaptively controls the DC-DC converters that power the LED
strings using patented Atmel Adaptive SourcePower™ technology. These
fault monitored efficiency optimizers minimize power use while maintaining
LED current accuracy, and allow up to eight interconnected devices to
automatically negotiate the optimum power supply voltage.
A unique combination of peak current control and pulse width dimming
management offers simple full-screen brightness control, versatile area
dimming, and a consistent white point. LED string current is set for each
string using a current sense (FET source) resistor. LED current is also digitally
controlled for all eight LED strings. Global string drive pulse width is adjusted
with an 8-bit global intensity register, and individual string pulse width is
modulated with 12-bit control.
The MSL3085 monitors for string open circuit, LED short circuit, loss-of-sync
and over temperature faults, and provides a hardware fault output to notify the
MCU. Detailed fault status and control are available through the serial interface.
Additionally, the MSL3085 includes an on-chip EEPROM that allows the
power-up default register settings to be customized via the serial interface.
The MSL3085 is offered in a 6 x 6 x 0.75mm, 40-pin TQFN package, and
operates over a -40°C to +105°C temperature range.
Applications
Long Life, Efficient LED Backlighting for:
• Televisions and Desktop Monitors
• Medical and Industrial Instrumentation
• Automotive Audio-visual Displays
Channel Signs
Architectural Lighting
Ordering Information
EIGHT-CHANNEL LED STRING DRIVER
2
PART
INTERFACE
PACKAGE
MSL3085BT
I2C
40-pin, 6 x 6 x 0.75mm TQFN
Atmel LED Driver-MSL3085
Atmel LED Driver-MSL3085
8-string White and RGB LED Driver with Adaptive Power
Control, EEPROM, and I2C/SMBus Serial Interface
Key Features
• 12-bit PWM String Dimming
• Global Intensity Control via Serial Interface
• Fast, 1MHz I C Serial Interface Supports up to
Eight Devices per Bus
• ±1.5% Current Accuracy and Current Balance
2
• 8-bit Adaptive Power Correction Maximizes
Efficiency of up to Two String Power Supplies
• Multiple MSL3085s Share String Power Supplies
and Automatically Negotiate the Optimum Supply
Voltage
• Video Frame (VSYNC) and Line (HSYNC)
Sync Inputs
• Sync Loss Detectors Optionally Disable LED Strings
• EEPROM Saves Power-on Default Settings
• LED Open Circuit and Short Circuit Fault Detection
• External MOSFETs for high Voltage and/or Current
• Individual Fault Detection Enable for Each String
• Drives up to Eight Parallel LED Strings
• Over-temperature Shut-Off Protection
• Supports Adaptive, Real-time Area Dimming for
Highest Dynamic Range in LCD TVs and Monitors
• Broadcast Write Simplifies Configuration
• -40°C To +105°C Operating Temperature Range
• Programmable String Phase Reduces Motion Blur
and Improves Efficiency
Application Circuit
Atmel LED Driver-MSL3085
3
Atmel LED Driver
MSL3085 Overview
The MSL3085 controls eight strings of series-connected
LEDs at up to 350mA per string. Eight MSL3085s can
share a serial interface. The MSL3085 FET gate drive
output is optimized for FETs requiring no more than
10nC of charge. The MSL3085 PWM engine generates
the PWM signal that drives the strings, or optionally
accepts an external PWM signal.
LED Power Supplies and Efficiency Optimizers
The MSL3085 features two efficiency optimizer outputs
that dynamically adjust the LED string power supplies
to their minimum voltage necessary to drive the LED
strings, while assuring accurate LED current flow. One of
the efficiency optimizers features an input that allows up
to eight devices to be connected in a chain configuration.
When implemented, the chain automatically negotiates,
controls, and optimizes the string power supply for all LED
strings driven by the chain.
The power supplies can use any topology, and are
typically DC-DC boost converters. The efficiency
optimizers rely on close matching of the LEDs
connected to a string supply. The better the matching,
the better the overall efficiency.
Timing, PWM, Intensity Controls
and Synchronization
The PWM LED drive signals synchronize to video frame
timing via the PHI input, and to pixel timing via the GSC
input. Area LED dimming is supported for contrast and
color gamut improvement. With area dimming, motion
blur is reduced by setting each LED string’s PWM
phasing to synchronize string off times with the LCD
update timing. The MSL3085 also includes internal
PWM timing generation for standalone (non-video)
LED lighting applications. Table 1 presents the available
methods of LED intensity control.
Table 1. LED Intensity Controls
LED INTENSITY CONTROL
4
EFFECT
REGISTER
RESOLUTION
Global LED string current
adjust
Reduces string current globally
from maximum set by FET
source resistors
ISTR (0x31)
8 bits
Global LED string PWM
Global PWM scaling
Individual LED string PWM
PWM individual string control
External resistor from FET
source to ground
External PWM input
GINT (0x2F)
and ALTGINT (0x30)
8 bits
PWMn (0x60 thru 0x7D)
and
ALTPWMn (0xA0 thru 0xBD)
12 bits
Sets maximum individual
string current
-
-
Optionally controls all string
PWM drives
-
-
Atmel LED Driver-MSL3085
Atmel LED Driver-MSL3085
8-string White and RGB LED Driver with Adaptive Power
Control, EEPROM, and I2C/SMBus Serial Interface
Package Pin-out
S4
D2
G2
S2
D0
G0
S0
VDD
VIN
EN
40
39
38
37
36
35
34
33
32
31
(TOP VIEW)
G4
1
30
PWM
D4
2
29
GSC
S6
3
28
PHI
G6
4
27
VCC
D6
5
26
D14
NC
6
25
G14
SDA
7
24
S14
SCL
8
23
D12
GND
9
22
G12
FLTB
10
21
S12
12
13
4
14
15
16
17
18
19
20
FBO2
FBI1
S9
G9
D9
S11
G11
D11
FBO1
11
ADDR
MSL3085
Figure 1. Atmel LED Driver-MSL3085
Pin-out, 40-pin TQFN.
Figure 2. Package Dimensions: 40-pin, 6mm x 6mm x 0.75mm TQFN (0.5mm pin pitch) with Exposed Pad.
Atmel LED Driver-MSL3085
5
Pin Descriptions
NOTE: To ensure register compatibility with the 16-string device of the same family (Atmel LED Driver-MSL2161), pin names for gate,
drain and source connections are not sequential.
6
PIN
PIN
NAME
1
G4
Gate output 4
Gate drive output for external MOSFET 4. Connect G4 to the gate of the external MOSFET driving LED string 4.
2
D4
Drain sense input 4
Drain sense input for external MOSFET 4. Connect D4 through a 10MΩ resistor to the drain of the external MOSFET
driving LED string 4.
3
S6
Source sense input 6
Source sense input for external MOSFET 6. Connect S6 to the source of the external MOSFET, and to the current sense
resistor for LED string 6. The full-scale LED current is reached when 500mV is across the current sense resistor.
4
G6
Gate output 6
Gate drive output for external MOSFET 6. Connect G6 to the gate of the external MOSFET driving LED string 6.
5
D6
Drain sense input 6
Drain sense input for external MOSFET 6. Connect D6 through a 10MΩ resistor to the drain of the external MOSFET
driving LED string 6.
6
NC
No connection
Make no connection to NC.
7
SDA
I²C serial data I/O
SDA is the data I/O for the I²C serial interface.
8
SCL
I²C serial clock input
SCL is the clock input for the I²C serial interface.
9
GND
Ground
Connect GND to system ground and to EP with short, wide traces.
10
FLTB
Fault indication output (active low)
Open drain output FLTB sinks current to GND whenever a fault is detected and verified.
FLTB remains low until the fault registers are read, and reasserts if the fault persists.
11
ADDR
Slave ID selection inputs
Connect ADDR to a resistor to GND to set the device address for the serial interface.
12
FBO2
Efficiency Optimizer output 2
Connect FBO2 to the second power supply’s feedback node. If unused, leave FBO2 unconnected.
13
FBI1
Efficiency Optimizer input 1
Connect FBI1 to FBO1 of the next device, when chaining the Efficiency Optimizers
Connect FBI1 to GND if unused.
14
FBO1
Efficiency Optimizer output 1
Connect FBO1 to the first power supply’s feedback node. If unused, leave FBO1 unconnected.
15
S9
Source sense input 9
Source sense input for external MOSFET 9. Connect S9 to the source of the external MOSFET, and to the current sense
resistor for LED string 9. The full-scale LED current is reached when 500mV is across the current sense resistor.
16
G9
Gate output 9
Gate drive output for external MOSFET 9. Connect G9 to the gate of the external MOSFET driving LED string 9.
17
D9
Drain sense input 9
Drain sense input for external MOSFET 9. Connect D9 through a 10MΩ resistor to the drain of the external MOSFET
driving LED string 9.
18
S11
Source sense input 11
Source sense input for external MOSFET 11. Connect S11 to the source of the external MOSFET, and to the current
sense resistor for LED string 11. The full-scale LED current is reached when 500mV is across the current sense resistor.
19
G11
Gate output 11
Gate drive output for external MOSFET 11. Connect G11 to the gate of the external MOSFET driving LED string 11.
20
D11
Drain sense input 11
Drain sense input for external MOSFET 11. Connect D11 through a 10MΩ resistor to the drain of the external MOSFET
driving LED string 11.
PIN DESCRIPTION
Atmel LED Driver-MSL3085
Atmel LED Driver-MSL3085
8-string White and RGB LED Driver with Adaptive Power
Control, EEPROM, and I2C/SMBus Serial Interface
PIN
PIN
NAME
PIN DESCRIPTION
21
S12
Source sense input 12
Source sense input for external MOSFET 12. Connect S12 to the source of the external MOSFET, and to the current
sense resistor for LED string 12. The full-scale LED current is reached when 500mV is across the current sense resistor.
22
G12
Gate output 12
Gate drive output for external MOSFET 12. Connect G12 to the gate of the external MOSFET driving LED string 12.
23
D12
Drain sense input 12
Drain sense input for external MOSFET 12. Connect D12 through a 10MΩ resistor to the drain of the external MOSFET
driving LED string 12.
24
S14
Source sense input 14
Source sense input for external MOSFET 14. Connect S14 to the source of the external MOSFET, and to the current
sense resistor for LED string 14. The full-scale LED current is reached when 500mV is across the current sense resistor.
25
G14
Gate output 14
Gate drive output for external MOSFET 14. Connect G14 to the gate of the external MOSFET driving LED string 14.
26
D14
Drain Sense Input 14
Drain sense input for external MOSFET 14. Connect D14 through a 10MΩ resistor to the drain of the external MOSFET
driving LED string 14.
27
VCC
5V internal LDO regulator output
VCC powers the FBO outputs. Bypass VCC to GND with a 4.7µF ceramic capacitor placed close to VCC.
28
PHI
Phase synchronization input
Drive PHI with an external signal of typically 100Hz to 480Hz to synchronize the MSL3085 LED PWM timing.
29
GSC
Gate shift clock input
Drive GSC with the gate shift clock of the video signal.
30
PWM
PWM input
PWM allows external control of the brightness of all LED strings. Drive PWM with a pulse-width-modulated signal with a
duty cycle of 0% to 100% and a frequency up to 5kHz. When not configured as an input, PWM is high impedance.
31
EN
Enable input (active high)
Drive EN high to turn on the MSL3085, and drive EN low to turn off the MSL3085. For automatic start-up, connect EN to
VIN. When EN is low, the entire device, including the serial interface, is turned off. Driving EN high initiates a boot load
of the EEPROM data into the control registers, simulating a cold start-up.
32
VIN
Supply voltage input
Connect a 12V ±10% supply to VIN. Bypass VIN to GND with a 10µF ceramic capacitor placed close to VIN.
33
VDD
2.5V internal LDO regulator output
VDD powers internal logic. Bypass VDD to GND with a 4.7µF ceramic capacitor placed close to VDD.
34
S0
LED string 0 external MOSFET source input
Source sense input for external MOSFET 0. Connect S0 to the source of the external MOSFET, and to the current sense
resistor for LED string 0. The full-scale LED current is reached when 500mV is across the current sense resistor.
35
G0
Gate output 0
Gate drive output for external MOSFET 0. Connect G0 to the gate of the external MOSFET driving LED string 0.
36
D0
Drain sense input 0
Drain sense input for external MOSFET 0. Connect D0 through a 10MΩ resistor to the drain of the external MOSFET
driving LED string 0.
37
S2
LED string 2 external MOSFET source input
Source sense input for external MOSFET 2. Connect S2 to the source of the external MOSFET, and to the current sense
resistor for LED string 2. The full-scale LED current is reached when 500mV is across the current sense resistor.
38
G2
Gate output 2
Gate drive output for external MOSFET 2. Connect G2 to the gate of the external MOSFET driving LED string 2.
39
D2
Drain sense input 2
Drain sense input for external MOSFET 2. Connect D2 through a 10MΩ resistor to the drain of the external MOSFET
driving LED string 2.
40
S4
LED string 4 external MOSFET source input
Source sense input for external MOSFET 4. Connect S4 to the source of the external MOSFET, and to the current sense
resistor for LED string 4. The full-scale LED current is reached when 500mV is across the current sense resistor.
EP
EP
Exposed pad, power ground
Connect EP to system ground and to GND using short, wide traces. EP provides thermal relief for the die.
Atmel LED Driver-MSL3085
7
Absolute Maximum Ratings
Voltage (With Respect to GND)
VIN, EN, D0 thru D14, G0 thru G14................................................................................................................. -0.3V to +18V
VCC......................................................................................................................................................................................................-0.3V to +6V
VDD, ADDR, S0 thru S14........................................................................................................................................-0.3V to +2.75V
FBO1, FBO2, FLTB............................................................................................................................................................-0.3V to +5.5V
PHI, GSC, PWM................................................................................................................................................-0.3V to (VCC + 0.3V)
SDA, SCL....................................................................................................................................................................................-0.3V to +5.5V
Current (Into Pin)
VIN....................................................................................................................................................................................................................... 50mA
FBO1, FBO2......................................................................................................................................................................+0µA to -800µA
G0 thru G14..........................................................................................................................................................................................±100mA
All other pins................................................................................................................................................................................................20mA
Continuous Power Dissipation
40-Pin 6mm x 6mm QFN (derate 38mW/°C above TA = +70°C).................................................. 2100mW
Ambient Operating Temperature range TA = TMIN to TMAX............................................ -40°C to +105°C
Junction Temperature ................................................................................................................................................................ +125°C
Storage Temperature range........................................................................................................................... -65°C to +125°C
Lead Soldering Temperature, 10s................................................................................................................................... +300°C
Electrical Characteristics
Typical application circuit, VVIN = 12V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VVIN = 12V, TA = +25°C
PARAMETER
SYMBOL
CONDITIONS AND NOTES
MIN
TYP
MAX
UNIT
10.8
12
13.2
V
Normal operation, all LED strings driven
25
32.5
mA
500
DC ELECTRICAL CHARACTERISTICS
VIN operating supply voltage
VIN
VIN operating supply current
IVIN
VIN shutdown supply current
ISLEEP
SLEEP = 1, SDA, SCL, ADDR, PWM,
PHI and GSC at GND or VDD
VCC regulation voltage
VCC
IVCC = -1.0mA
4.5
5.0
5.5
V
VDD regulation voltage
VDD
IVDD = -1.0mA
2.4
2.5
2.6
V
EN input high voltage
8
1.4
µA
V
Atmel LED Driver-MSL3085
Atmel LED Driver-MSL3085
8-string White and RGB LED Driver with Adaptive Power
Control, EEPROM, and I2C/SMBus Serial Interface
PARAMETER
SYMBOL
CONDITIONS AND NOTES
MIN
TYP
EN input low voltage
UNIT
0.9
V
0.7 x
VDD
PWM, PHI, GSC input high voltage
VIH
PWM, PHI, GSC input low voltage
VIL
PHI, GSC output high voltage
VOH
ISOURCE = 5mA
PHI, GSC, FLTB output low voltage
VOL
ISINK = 6mA
FBO feedback output current
MAX
Compliance voltage 3.5V, minimum
V
0.3 x
VDD
V
0.4
V
360
μA
VDD –
0.4
0
FBO feedback output current step size
1.2
μA
D0 thru D7 short circuit fault detection
threshold
8
V
G0 thru G7 open circuit fault detection
threshold
8
V
G0 thru G14 gate drive charge
(Note 2)
S0 thru S7 regulation voltage
492
S0 thru S7 voltage matching
ISTR = 0x7F
-1.5
Thermal shutdown temperature
PARAMETER
500
10
µC
508
mV
1.5
TBD
SYMBOL
CONDITIONS AND NOTES
MIN
TYP
%
°C
MAX
UNIT
I2C LOGIC LEVELS
0.7 x
VDD
SDA, SCL input high voltage
V
SDA, SCL input low voltage
SDA output low voltage
PARAMETER
ISINK = 6mA
SYMBOL
CONDITIONS AND NOTES
0.3 x
VDD
V
0.4
V
MIN
TYP
MAX
UNIT
19.4
20
20.6
MHz
AC ELECTRICAL CHARACTERISTICS
OSC frequency
fOSC
PHI frequency
fPHI
0.04
10
kHz
GSC frequency
fGSC
0
10
MHz
PWM frequency
fPWM
5
kHz
100
%
PWM duty cycle
PHI lock
Atmel LED Driver-MSL3085
fOSC = 20MHz, TA = 25°C
0
4
PHI
cycles
9
PARAMETER
SYMBOL
CONDITIONS AND NOTES
MIN
TYP
MAX
UNIT
1
MHz
31
ms
I²C TIMING CHARACTERISTICS
SCL clock frequency
1/tSCL
Bus timeout disabled (Note 3)
0
Bus time-out period
ttimeout
fOSC = 20MHz, TA = 25°C
29
fOSC = 16MHz to 23MHz
STOP to START condition bus
free time
30
600,000 / fOSC
s
tBUF
0.5
µs
Repeated START condition
hold time
tHD:STA
0.26
µs
Repeated START condition set-up
time
tSU:STA
0.26
µs
STOP condition set-up time
tSU:STOP
0.26
µs
SDA data hold time
tHD:DAT
SDA data valid acknowledge time
tVD:ACK
(Note 4)
0.05
0.45
µs
SDA data valid time
tVD:DAT
(Note 5)
0.05
0.45
µs
SDA data set-up time
tSU:DAT
100
ns
SCL clock low period
tLOW
0.5
µs
SCL clock high period
tHIGH
SDA, SCL fall time
tf
SDA, SCL rise time
tr
SDA, SCL input suppression
filter period
tSP
0
ns
0.26
µs
(Note 6) (Note 7)
(Note 8)
50
120
ns
120
ns
ns
Note 1. Subject to thermal dissipation characteristics of the device.
Note 2. Guaranteed by design, and is not production tested.
Note 3. Minimum SCL clock frequency is limited by the bus time-out feature, which resets the serial bus interface if either SDA or SCL is held low
for ttimeout. Disable bus time-out via the fault enable register 0x03[6].
Note 4. tVD:ACK = SCL low to SDA (out) low acknowledge time.
Note 5. tVD:DAT = minimum SDA output data valid time following SCL low transition.
Note 6. A master device must internally provide an SDA hold time of at least 300ns to ensure an SCL low state.
Note 7. The maximum SDA and SCL rise times are 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.
Note 8. Input filters on SDA, SCL, and ADDR suppress noise less than 50ns.
10
Atmel LED Driver-MSL3085
Atmel LED Driver-MSL3085
8-string White and RGB LED Driver with Adaptive Power
Control, EEPROM, and I2C/SMBus Serial Interface
Typical Application Circuit
Figure 3. Atmel LED Driver-MSL3085 Driving 80 White LEDs in Eight Strings.
Atmel LED Driver-MSL3085
11
Detailed Description
The MSL3085 is a highly integrated, flexible, multi-string
LED driver that uses external MOSFETs to allow high
LED string currents, and includes power supply control
to maximize efficiency. The driver optionally connects
to a video subsystem to offer a simple architecture for
use in LCD TV backlight applications. Up to eight devices
easily connect together to drive a large number of
LED strings in a system. The drivers provide multiple
methods of controlling LED brightness through both
peak current control and pulse width control of the
string drive signals. Peak current control offers excellent
color consistency, while pulse width control allows
brightness management. An on-chip EEPROM holds
all the default control register values. At power-up,
the data in the EEPROM is automatically copied
directly to the control registers, setting up the device
for operation. The factory programmed EEPROM
values are changeable through the serial interface if a
different power-up condition is desired.
The device interfaces to an MCU via the I2C interface.
The robust, 1MHz I2C interface supports up to eight
devices on the bus. While typically the LED drive PWM
signal is internally generated, the device also accepts
an external direct PWM drive signal applied to the
PWM input that sets the PWM duty cycle and the
frequency of the LED drive signals. The MSL3085 also
allows phase spreading of the LED drive signals, which
helps reduce both the transient load on the LED power
supplies and the power supply input capacitor size
requirements.
The MSL3085 is an eight string version of the
MSL2161, squeezed into a smaller package, with
two efficiency optimizer (EO) outputs and one EO
input. (The MSL2161 offers 16 string drives, three EO
outputs, and three EO inputs.) This offers the advantage
of small size, but to ensure register compatibility with
the MSL2161, pin names of the FET drive outputs are
not sequential. The FET drive outputs are named 0, 2,
4, 6, 9, 11, 12, and 14 (not 0 through 7). All control
registers also follow this naming convention. Additionally,
this has a small impact on the automatic phase-shift
feature, whose sequential phase shifts for outputs 9
and 12 are spaced at 1/16th the PWM frame, while the
others are spaced at 1/8th the PWM frame.
synchronized to the internal oscillator for standalone
applications, or set directly by a signal at the PWM input.
Typically, the VSYNC signal from the video system is
used as the PHI input. A frequency multiplier (1x to
32x) processes this signal for use by the PWM engine.
The on time of each string is individually programmed
via the device registers, providing a peak resolution
of 12 bits when using the on-chip PWM generator.
The actual resolution of the PWM frequency depends
on the ratio of the GSC frequency (typically provided
by a system’s HSYNC signal, but can be internally
generated) to the PHI frequency because the on time of
a string is programmed as a 12-bit count of the number
of GSC clock cycles. This count can be further scaled by
an 8-bit global intensity register, when enabled. The
GSC clock is also used to precisely set each string’s
phase delay so that it is synchronized to its physical
position relative to the video frame.
The efficiency optimizers control a wide range of
different external DC-DC and AC/DC converter
architectures. Multiple drivers in a system communicate
in real time among themselves to select an optimized
operating voltage for the LEDs. This allows design of the
power supply for the worst case forward voltage (Vf)
of the LEDs without concern about excessive power
dissipation issues. During the start-up sequence, the
MSL3085 automatically reduces the power supply
voltage to the minimum voltage required to keep the
LEDs in current regulation. The devices are configured
to periodically perform this optimization to compensate
for changes in LED forward voltage, and to assure
continued optimum power savings.
Internal Regulators and Enable Input
The MSL3085 includes two internal linear regulators
that provide VCC (5V) and VDD (2.5V) for internal
circuitry. VIN (12V nominal) supplies the VCC and VDD
regulators. Bypass VIN to GND with a 10µF capacitor
close to the device. Bypass VCC to GND with a 4.7μF
capacitor close to the device. Bypass VDD to GND with a
4.7μF capacitor close to the device.
The PWM frequency of the drivers is easily
synchronized to an external video signal applied to PHI,
12
Atmel LED Driver-MSL3085
Atmel LED Driver-MSL3085
8-string White and RGB LED Driver with Adaptive Power
Control, EEPROM, and I2C/SMBus Serial Interface
The MSL3085 enable input, EN, enables the device.
Drive EN low to enter low power operation, which
lowers quiescent current draw to less than 20µA. With
EN low, the serial interface is ignored, the efficiency
optimizer is disabled, and all strings are turned off. Drive
EN high to turn on the device. When EN is driven high,
the contents of the EEPROM are boot loaded into the
control registers, simulating a cold start-up, and all bits in
the fault registers are cleared to 0.
where Vf(MIN) and Vf(MAX) are the LED minimum and
maximum forward voltage drops at the peak current
set by RS. For example, if the LED data are Vf(MIN) = 3.5V
and Vf(MAX) = 3.8V, and ten LEDs are used in a string,
then the total minimum and maximum voltage drops
across a string are 35V and 38V, respectively. Adding
an allowance of 0.5V for the string drive MOSFET
headroom brings VOUT(MIN) to 35.5V and VOUT(MAX) to
38.5V. Then, determine RTOP using:
Setting the Maximum LED String Current
With a Source Resistor
RTOP =
The maximum string current, ILED, for each string is set
by a resistor, RS, connected to ground from the source
terminal of the external string drive MOSFET. The
feedback threshold is 500mV. Determine the resistor
value using:
where IFBOn(MAX) is the 255µA maximum
output current of the efficiency optimizer
outputs FBOn. Finally, determine RBOTTOM using:
RS =
0 .5
I LED
, where ILED is in amperes and RS is in ohms.
For example, a full-scale LED current of 100mA returns
RS = 5Ω. The current for all LED strings is reduced from
the full-scale value with 8-bit resolution using ISTR, the
string current control register 0x31.
Connecting the Efficiency Optimizer to an LED
String Power Supply and Selecting Resistors
The MSL3085 is designed to control an external LED
string power supply that uses a voltage divider (RTOP
and RBOTTOM in Figure 4) to set output voltage, and
whose regulation feedback voltage is not more than
3.5V. The efficiency optimizer improves power efficiency
by injecting a current of between 0 and 255µA into
the voltage divider of the external power supply,
dynamically adjusting the power supply's output to the
minimum voltage required by the LED strings. To select
the resistors, first determine VOUT(MIN) and VOUT(MAX), the
minimum and maximum string supply voltage limits,
using:
VOUT ( MAX) − VOUT ( MIN)
I FBOn ( MAX)
RBOTTOM = RTOP ∗
.
VFB
VOUT ( MAX) − VFB
,
where VFB is the regulation feedback voltage of the
power supply. Place a diode (1N4148 or similar)
between FBOn and the supply’s feedback node to
protect the MSL3085 against current flow into FBOn.
Assign all strings powered by a common supply to the
proper FBO output using string set registers 0x40 0x5D.
Once configured, determine the change in power
supply output voltage in response to a change in FBOn
output current using:
∆VOUT = ∆I FBO ∗ RTOP
.
VOUT(MIN) = (Vf (MIN) *[#ofLEDs])+ 0.5 ,
and
VOUT(MAX) = (Vf (MAX) *[#ofLEDs])+ 0.5 ,
Atmel LED Driver-MSL3085
Figure 4. FBOn Connects to the Power Supply
Voltage Divider through a Diode.
13
Using Multiple Atmel LED Driver-MSL3085s to Control a Common Power Supply
Cascade multiple MSL3085 devices into a chain configuration (Figure 5), with the FBI1 of one device connected to the
FBO1 of the next. Connect the first FBO1 to the power supply feedback resistor node through a diode, and the unused
FBI1 input to ground as close to the MSL3085 as possible. Assure that all strings powered by the common supply are
assigned to FBO1 using string set registers (STRnSET) 0x20 - 0x3D (FBO1 is the power-up default setting for all
strings). The chained devices work together to ensure that the system operates at optimum efficiency. Note that the
accuracy of the feedback chain can degrade through each link of the FBI1/FBO1 chain by as much as 2%. Determine the
potential worst case maximum FBO1 current, IFBOn(MAX/MIN), using:
IFBO(MAX / MIN) = 255µA* (0.98)N-1 ,
where N is the number of MSL3085s connected in series. Use this result in the above RTOP resistor equation for the term
IFBOn(MAX) instead of using 255µA.
Take care in laying out the traces for the efficiency optimizer connections. Minimize the FBI1/FBO1 trace lengths as much
as possible. Do not route the signals close to traces with large variations in voltage or current because noise may couple into
FBI1. If these traces must be routed near noisy signals, shield them from noise by using ground planes or guard traces.
Figure 5. Example of Cascading Multiple Devices to Optimize a Common String Power Supply.
14
Atmel LED Driver-MSL3085
Atmel LED Driver-MSL3085
8-string White and RGB LED Driver with Adaptive Power
Control, EEPROM, and I2C/SMBus Serial Interface
Direct PWM Control of the LED Strings
An external PWM signal applied to the PWM input allows direct PWM control over the strings when PWMEN and
PWMDIRECT (bits D0 and D1 in PWM control register 0x2D) are set to 1. This configuration bypasses PHI and GSC, but
allows LED string phase delay via the phase delay enable bit, PHADLYEN (bit D0 of register 0x2E). With phase delay
enabled, a progressive delay based on the period of the PWM frame is calculated and applied successively to each string
drive signal. The delay is typically 1/8th the PWM frame, but outputs 9 and 12 have sequential delays of 3/16th and 1/16th
of the PWM frame, respectively.
The PWM input can also be configured as a gate for the output of the PWM engine using PWM global enable (bit D2 of
the PWM control register 0x2D).
Register Map and the EEPROM
Register Map Summary
Control the MSL3085 using the registers in the range 0x00 - 0xBD (Table 2). Two additional registers, 0xC0 and 0xC1,
allow access to, and programming of, the EEPROM. The power-up default values for all control registers are stored within
the on-chip EEPROM, and any of these EEPROM values may be changed through the serial interface
Table 2. Atmel LED Driver-MSL3085 Register Map
ADDRESS AND
FUNCTION
REGISTER NAME
0x00
STRINGEN0
0x01
STRINGEN1
0x02
0x03
0x04
0x05
0x06
CONFIG
FLTEN
STRFLTEN0
STRFLTEN1
FLTSTATUS*
0x07
OCSTAT0*
0x08
OCSTAT1*
0x09
SCSTAT0*
0x0A
SCSTAT1*
LED
string
enables
Configuration
Fault enable
String fault
enable
Fault status
String open
circuit fault
status
String short
circuit fault
status
REGISTER DATA
D7
-
STR6EN
D6
D5
-
STR4EN
D4
D3
-
STR2EN
D2
D1
-
STR0EN
-
STR14EN
-
STR12EN
STR11EN
-
STR9EN
-
SLEEP
FLTBDRV
FEN6
FEN14
-
I2CTOEN
-
PHIMAXFEN
FEN4
FEN12
PHIMAXFLT
-
OC6
-
OC4
-
OC2
-
OC0
-
OC14
-
OC12
OC11
-
OC9
-
-
SC6
-
SC4
-
SC2
-
SC0
-
SC14
-
SC12
SC11
-
SC9
-
0x0B - 0x0E
0x0F
OSCFREQ
0x10
0x11
0x12
FBOCTRL0
FBOCTRL1
FBOCTRL2
0x13
FBODAC1*
0x14
FBODAC2*
FBOSTAT*
Atmel LED Driver-MSL3085
FLDBKEN
STRSCDLY[2:0]
GSCMAXFEN STRSCFEN STROCFEN FBOOCFEN
FEN2
FEN0
FEN11
FEN9
GSCMAXFLT STRSCFLT
STROCFLT FBOOCFLT
UNUSED
Oscillator
frequency
Efficiency
Optimizer
control
Efficiency
Optimizer
DAC
readback
-
-
HDRMSTEP[1:0]
INCRSTEP[1:0]
-
-
-
-
RECALDLY[1:0]
DECRSTEP[1:0]
-
OSCFREQ[2:0]
SETTLE[1:0]
INITPWM
ACAL100
FBO2OCEN
IERRCONF[1:0]
ACALEN
ICHKDIS
FBO1OCEN
FBOEN
FBODAC1[7:0]
FBODAC2[7:0]
0x15
0x16
D0
UNUSED
Efficiency
Optimizer
status
-
FBO2OC
FBO1OC
-
FBO2ACT
FBO1ACT
FBOCAL
FBOINITCAL
15
Table 2. Atmel LED Driver-MSL3085 Register Map
ADDRESS AND
FUNCTION
REGISTER NAME
0x17
- 0x1F
0x20
GSCCTRL
0x21
GSCCNTR
0x22
0x23
GSCMUL
0x24
0x25
GSCDIV
GSCMAX
0x26
0x27
PHICTRL
0x28
PHICNTR
0x29
0x2A
0x2B
0x2C
PHIMUL
PHIMAX
0x2D
PWMCTRL0
0x2E
PWMCTRL1
REGISTER DATA
D7
D6
D5
GINT
0x36 - 0x3F
16
D3
D2
D1
D0
GSCPOL
GSCPHISYNCEN
GSCINTEN
PHIPOL
PHIINTEN
UNUSED
GSC
GSCCHKprocessing
SEL
control
Internal clock
counter for
GSC
GSC
multiplier
GSC divider
Max
oscillator
cycles
between
GSC pulses
PHI
PHICHK
processing
SEL
control
Internal clock
counter for
PHI
PHI multiplier
Max GSC
cycles
between PHI
pulses
PWM control
-
-
-
GSCMAXEN
GSCCNTR[7:0]
GSCCNTR[15:8]
-
-
GSCMUL[4:0]
GSCDIV[7:0]
GSCMAX[7:0]
GSCMAX[15:8]
-
-
-
-
PHIMAXEN
PHICNTR[7:0]
PHICNTR[15:8]
-
-
PHIMUL[4:0]
PHIMAX[7:0]
PHIMAX[15:8]
GINT+1EN
GINTEN
ALTEN
OVRFLOZEN
OVRFLOEN
-
-
-
-
EXTALTEN
Global PWM
scaling
Alternate
0x30
ALTGINT
global PWM
scaling
8-bit global
0x31
ISTR
string current
scaling
PWM and
0x32 PWMSTATUS*
counter
PHIMAXERRCNT[2:0]
status
PHI pulse
PHICNTR0x33 PHIPCNTR* counter and
MAX
status
0x34
GSC pulse
GSCPCNTR*
counter
0x35
-
0x2F
D4
PWM
GLBLEN
PHOVR
FLOZEN
PWMDIRECT
PWMEN
PHOVR
FLOEN
PHADLYEN
GINT[7:0]
ALTGINT[7:0]
ISTR[7:0]
PHIMAX1FLT
PHISIGFLT GSCSIGFLT PHICNTRFLT
GINTMULERR
PHIMULCNTR[0:4]
GSCPULSECNTR[7:0]
GSCPULSECNTR[12:8]
UNUSED
Atmel LED Driver-MSL3085
Atmel LED Driver-MSL3085
8-string White and RGB LED Driver with Adaptive Power
Control, EEPROM, and I2C/SMBus Serial Interface
ADDRESS AND
FUNCTION
REGISTER NAME
0x40
0x41
↓
STR0SET
↓
0x5C
0x5D
STR14SET
Phase delay
and EO
assignment
for string 0
↓
Phase delay
and EO
assignment
for string 14
REGISTER DATA
D7
D6
D5
D4
FBOSET0[1:0]
-
-
0x61
↓
0x7C
0x7D
PWM0
FBOSET14[1:0]
-
-
PHDLY[11:8]
PWM0[7:0]
PWM setting
for string 0
↓
PWM14
PWM setting
for string 14
↓
ALTSTR0SET
D0
PHDLY14[7:0]
-
-
-
-
-
-
-
-
PWM0[11:8]
PWM14[7:0]
0x7E and 0x7F
0x81
D1
UNUSED
↓
0x80
D2
PHDLY[11:8]
0x5E and 0x5F
0x60
D3
PHDLY0[7:0]
PWM14[11:8]
UNUSED
Alternate
phase delay
for
string 0
ALTPHDLY0[7:0]
-
-
-
-
ALTPHDLY[11:8]
↓
0x9C
0x9D
ALTSTR14SET
Alternate
phase delay
for
string 14
ALTPHDLY14[7:0]
-
-
-
-
ALTPHDLY[11:8]
0x9E and 0x9F
0xA0
0xA1
↓
ALTPWM0
UNUSED
Alternate
PWM setting
for string 0
ALTPWM0[7:0]
-
-
-
-
ALTPWM0[11:8]
↓
0xBC
0xBD
ALTPWM14
Alternate
PWM setting
for string 14
ALTPWM14[7:0]
-
-
-
-
0xBE and 0xBF
0xC0
E2ADDR
0xC1
E2CTRLSTA
ALTPWM14[11:8]
UNUSED
EEPROM
read/write
access
Atmel LED Driver-MSL3085
E2BUSY
E2ADDR[6:0]
BLDACT
E2ERR
-
-
RWCTRL[2:0]
17
Register Power-up Defaults
Register power-up default values are shown in Table 3.
Table 3. Atmel LED Driver-MSL3085 Register Power-up Defaults
REGISTER NAME
AND ADDRESS
0x00
STRINGEN0
0x01
STRINGEN1
POWER-UP CONDITION
REGISTERS INITIALIZED FROM EEPROM
LED strings 0, 2, 4, 6, 9, 11, 12, and 14 enabled
REGISTER DATA
D7
D6
D5
D4 D3 D2
D1
D0 HEX
0
1
0
1
0
1
0
1
55
0
1
0
1
1
0
1
0
5A
CONFIG
String short circuit confirmation delay = 256µs
String current fold-back enabled
Device awake
0
0
0
0
1
1
0
1
0D
0x03
FLTEN
FBO open circuit fault detect globally enabled
String open circuit fault detect globally enabled
LED short circuit fault detect globally enabled
GSC max fault detect globally disabled
PHI max fault detect globally disabled
I2C timeout enabled
0
0
1
0
0
1
1
1
27
0x04
STRFLTEN0
1
0
1
0
1
0
1
55
STRFLTEN1
Fault detection individually enabled
For all strings (0, 2, 4, 6, 9, 11, 12, and 14)
0
0x05
0
1
0
1
1
0
1
0
5A
0x0F
OSCFREQ
fosc = 20MHz
0
0
0
0
0
1
0
0
04
0x10
FBOCTRL0
0
1
0
0
1
0
0
1
49
0x11
FBOCTRL1
0
0
0
1
1
0
1
0
1A
0x12
FBOCTRL2
0
0
0
0
0
0
1
1
03
0
0
0
0
0
0
0
0
00
0
1
0
1
0
0
0
0
50
0
0
0
0
0
0
0
0
00
03
0x02
0x20
0x21
0x22
Current sink error confirmation delay = 2µs
FBO power supply correction delay = 4ms
Efficiency Optimizer auto-recalibration delay = 1s
Efficiency Optimizer headroom steps = 3
MOSFET current sink error detection enabled
Efficiency Optimizer auto-recalibration enabled
PWM settings used during auto-recalibration
PWM settings used during initial calibration
Efficiency Optimizer correction step size = 1 LSB (1µA)
Efficiency Optimizer initial calibration step size = 1 LSB
(1µA)
FBO outputs globally enabled
FBO1 open circuit detection enabled
FBO2 open circuit detection disabled
GSCCTRL
External signal at GSC is selected for input to the PWM
engine
GSC not internally synchronized to PHI
PWM drive synchronized to falling edge of external GSC
signal
GSC maximum count fault detect is disabled
although disabled, GSC max fault monitors fpGSC
GSCCNTR
Although disabled, internal GSC
Frequency fGGEN = 20MHz / (80 + 1) = 246kHz
0x23
GSCMUL
GSC multiplexer output is multiplied by 4
(register setting + 1)
0
0
0
0
0
0
1
1
0x24
GSCDIV
GSC multiplier output is divided by 1 (register setting + 1)
0
0
0
0
0
0
0
0
00
GSCMAX
Although disabled, GSC max count is set to 174 clock
cycles
1
0
1
0
1
1
1
0
AE
0
0
0
0
0
0
0
0
00
PHICTRL
External signal at PHI selected for input to PWM engine
PWM engine is synchronized to the falling edge of PHI
PHI maximum count fault detect is disabled
Although disabled, PHI max count monitors fpPHI
0
0
0
0
0
0
0
0
00
0x25
0x26
0x27
18
Atmel LED Driver-MSL3085
Atmel LED Driver-MSL3085
8-string White and RGB LED Driver with Adaptive Power
Control, EEPROM, and I2C/SMBus Serial Interface
REGISTER NAME
AND ADDRESS
0x28
0x29
0x2A
0x2B
0x2C
D6
D5
Although disabled, internal PHI
Frequency fPGEN = 20MHz / (8 * (10416 + 1)) = 240Hz
1
0
1
1
0
0
0
0
B0
0
0
1
0
1
0
0
0
28
PHIMUL
PHI multiplier = 1 (register setting + 1)
0
0
0
0
0
0
0
0
00
PHIMAX
Although disabled, PHI maximum count = 4148
0
0
1
1
0
1
0
0
34
0
0
0
1
0
0
0
0
10
1
0
0
1
1
0
0
1
99
0
0
0
0
0
1
1
1
07
Global intensity set to (127 + 1) / 255 = 50.2%
0
1
1
1
1
1
1
1
7F
Alternate global intensity set to (95 + 1) / 255 = 37.6%
0
1
0
1
1
1
1
1
5F
Strings current set at 50% of RS setting
0
1
1
1
1
1
1
1
7F
0
0
0
0
0
0
0
0
00
0
1
0
0
0
0
0
0
40
0
0
0
0
0
0
0
0
00
0
1
0
0
0
0
0
0
40
0
0
0
0
0
0
0
0
00
0
0
0
0
0
0
1
0
02
0
0
0
0
0
0
0
0
00
0
0
0
0
0
0
1
0
02
0
0
0
0
0
0
0
0
00
0
0
0
0
0
0
0
0
00
0
0
0
0
0
0
0
0
00
0
0
0
0
0
0
0
0
00
0
0
0
0
0
0
0
0
00
0
0
0
0
0
0
1
0
02
0
0
0
0
0
0
0
0
00
0
0
0
0
0
0
1
0
02
PHICNTR
PWMCTRL0
0x2E
PWMCTRL1
0x2F
GINT
0x30
ALTGINT
0x31
ISTR
0x41
↓
0x5C
0x5D
0x60
0x61
↓
0x7C
0x7D
0x80
0x81
↓
0x9C
0x9D
0xA0
0xA1
↓
0xBC
0xBD
REGISTER DATA
D7
0x2D
0x40
POWER-UP CONDITION
REGISTERS INITIALIZED FROM EEPROM
PWM operation enabled
Individual LED string drive pulse widths internally
determined
PWM input does not gate the output of the PWM engine
String on times allowed to extend beyond end of PWM
frame String on times allowed to extend into frame zero
Alternate timing not used
Global intensity (GINT) disabled
Although disabled, (GINT + 1) is provided to the
PWM engine
String drive phasing enabled
Delayed string turn on beginning after PWM
frame allowed
Delayed turn on occurring in frame zero allowed
Alternate timing not selected by PWM input state
STR0SET
↓
All strings phase delay = zero
All strings assigned to FBO1
STR14SET
PWM0
↓
ALTSTR0SET
ALTPWM0
↓
All strings set with alternate PWM value = 512 GSC
cycles
ALTPWM14
D0 HEX
↓
↓
All strings alternate phase delay = zero
ALTSTR14SET
D1
↓
All strings have PWM value = 512 GSC cycles
PWM14
↓
D4 D3 D2
↓
REGISTERS WITH FIXED INITIAL VALUES
0xC0
E2ADDR
0xC1
E2CTRLSTA
Atmel LED Driver-MSL3085
EEPROM 7-bit address = 0x00
0
0
0
0
0
0
0
0
00
EEPROM read/write disabled
0
0
0
0
0
0
0
0
00
19
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© 2011 Atmel Corporation. All rights reserved. / Rev.: MEM-MSL3085DB1-E-US_06-11
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