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Atmel MSL3086/MSL3088 Datasheet

8-String 60mA LED Drivers with Integrated Boost Controller and Phase Shifted Dimming

Atmel MSL3086 / MSL3088

8-String 60mA LED Drivers with Integrated

Boost Controller and Phase Shifted Dimming

FULL DATASHEET

Features:

• Up to 8 parallel 60mA LED strings with up to 10

series white LEDs per string

• Integrated boost controller (MSL3086/88)

• Offers true 4095:1 (12-bit) LED dimming at 120Hz

• String open circuit and LED short circuit fault

detection and automatic correction

• ±3% current accuracy and current balance

• Single resistor sets current for all LED strings

• Simple to use external PWM dimming

• Optional internal PWM dimming

•

Automatic string phasing reduces EMI and supply ripple

•

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

Description

The MSL3086/88 8-channel LED drivers with integrated boost regulator controller offer a complete

solution to drive up to eight parallel LED strings at up to 40V. The LED current sinks control up to 60mA

peak for up to 19W of LED power. 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. The MSL3086 uses a single PWM input to control the LED dimming signals. The MSL3088

has two inputs, one for frequency and the other for duty cycle. Additionally, internal registers, available

through the I

C interface, optionally control PWM dimming frequency and/or duty cycle.

The MSL3086/88 feature phase-shifted PWM dimming to reduce the boost regulator transient response.

The integrated fault detection circuitry detects and acts upon string open-circuit and LED short circuit

faults, boost regulator over-voltage faults, and die over-temperature faults.

A proprietary Efciency Optimizer maintains sufcient boost regulator output voltage for proper LED

current while minimizing power use. A 1MHz I

C/SMBus serial interface allows optional dimming

control, fault inspection and control of device parameters; for serial interface information see the

MSL3040/50/60/80/86/87/88/89 Programming Guide.

The MSL3086/88 are offered in the 24-pin VQFN lead-free, halogen-free, RoHS compliant package and

operate over -40°C to +85°C.

DBIE-20120828

MSL3086/MSL3087/MSL3088 Datasheet

I²C and SMBus are trademarks of their respective owners.

Revision 0, June 2011 Page 1 of 26

8-String 60mA LED Drivers with Integrated Boost Controller and

Phase Shifted Dimming

______________ General Description

The MSL3086/87/88 8-channel LED drivers with integrated boost

regulator controller offer a complete solution to drive up to eight

parallel LED strings at up to 40V. The LED current sinks control

up to 60mA peak for up to 24W of LED power. 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. The MSL3086

and MSL3087 use a single PWM input to control the LED

dimming signals. The MSL3088 has two inputs, one for frequency

and the other for duty cycle. Additionally, internal registers,

available through the I

C interface, optionally control PWM

dimming frequency and/or duty cycle.

The MSL3086/87/88 feature phase-shifted PWM dimming to

reduce the boost regulator transient response. The integrated

fault detection circuitry 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 for proper LED current while minimizing

power use. A 1MHz I

C/SMBus serial interface allows optional

dimming control, fault inspection and control of device

parameters; for serial interface information see the

MSL3040/50/60/86/87/88/89 Programming Guide. Multiple

MSL3086/87/88‘s interconnect to operate more than 8 strings

while maintaining optimum efficiency.

The MSL3086/87/88 are offered in the 24-pin VQFN lead-free,

halogen-free, RoHS compliant package and operate over -40°C

to +85°C.

_____________________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

PART DESCRIPTION PKG

MSL3086

8-CH LED driver with integrated boost

controller and resistor based LED Short

Circuit threshold setting.

MSL3087

8-CH LED driver with power supply

feedback to interface with external

DC/DC converter and resistor based

LED Short Circuit threshold setting.

MSL3088

8-CH LED driver with integrated boost

and SYNC input.

24 pin

4 x 4 x 0.75mm

VQFN

____________________Key Features

 Up to 8 parallel 60mA LED strings with up to 14 series white

LEDs per string

 Integrated boost controller (MSL3086/88)

 Controls external DC/DC (MSL3087)

 Shares DC/DC with other drivers

 Offers true 4095:1 (12-bit) LED dimming at 200Hz

 String open circuit and LED short circuit fault detection and

automatic correction

 ±3% current accuracy and current balance

 Single resistor sets current for all LED strings

 Simple to use external PWM dimming

 Optional internal PWM dimming

 Automatic string phasing reduces EMI and supply ripple

 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

_______________ Application Circuit

APPLICATION CIRCUIT

CGND

Summary of content (23 pages)

PAGE 1
Phase Shifted Dimming ______________ General Description The MSL3086/87/88 8-channel LED drivers with integrated boost regulator controller offer a complete solution to drive up to eight parallel LED strings at up to 40V. The LED current sinks control up to 60mA peak for up to 24W of LED power. A single resistor sets LED current with string matching and accuracy within ±3%.
PAGE 2
Table of Contents 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 Packages and Pin Connections.................................................................. 3 Pin Descriptions........................................................................................... 4 Absolute Maximum Ratings........................................................................ 5 Electrical Characteristics............................................................................ 6 Typical Operating Characteristics............
PAGE 3
7 8 9 10 11 12 STR1 STR2 STR3 STR4 STR5 STR6 1.0 Packages and Pin Connections PHASE SHIFTED LED DIMMING SIGNALS FBO 1 VIN 2 SDA 3 SCL 4 19 By default, string PWM dimming is staggered in time to reduce the transient current demand on Package 24 23 22 21 20 19 MSL3040/41 automatically determine theInformation stagger times based on the number of enabled strings frequency.
PAGE 4
2.0 Pin Descriptions Table 2.1 Pin Assignments Name FB VIN SDA SCL SYNC SCTH STR0 STR1 STR2 STR3 STR4 STR5 STR6 STR7 PWM CGND ILED PGND GATE PVIN FLTB EN CS COMP GND EP MSL 3086 3088 Pin Description VLED Voltage Regulator Feedback Input: Connect a resistive voltage divider from the boost regulator output, VLED, to FB to set the un-optimized 1 1 boost regulator output voltage. The feedback regulation voltage is 2.5V. 2 2 Power Supply Input: Power supply input. Apply 4.5V to 5.5V to VIN.
PAGE 5
3.0 Absolute Maximum Ratings Voltage (with respect to GND) VIN, PVIN, EN, SDA, SCL, PWM, FLTB..................................................... -0.3V to +5.5V SYNC, SCTH, CS, COMP, FB, GATE.........................................................-0.3V to +5.5V ADDR, ILED, SCTH.................................................................................. -0.3V to +2.75V STR0 to STR7............................................................................................. -0.3V to +40V PVIN to VIN..
PAGE 6
4.0 Electrical Characteristics VVIN = 5V, VEN = 5V, Default Register Settings of Table 1, TA = -40°C to 85°C, unless otherwise noted.
PAGE 7
Note 6. Note 7. Note 8. Note 9. to be connected between SDA and SCL inputs and the SDA/SCL bus lines without exceeding the maximum allowable rise time. MSL3086/87/88 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. 5.
PAGE 8
VLED, CH3 = VSTRx, CH4 (continued) = IPWR = VEN, CH2 =Characteristics 5.0 TypicalCH1 Operating CH1 = VLED, CH2 = VGATE, CH3 = IINDUCTOR (Typical Operating Circuit, unless otherwise stated, TA = +25°C, unless otherwise noted) AUTO CALIBRATION CH2 = VLED, CH3 = VSTRx BOOST WAVEFORMS 100% LED DUTY CYCLE MSL3086/MSL3087/MSL3088 Datasheet CH1 = VLED, CH2 = VGATE, CH3 = IINDUCTOR BOOST REGULATOR WAVEFORMS 10% TO 99.5% LED DUTY CYCLE © Atmel Inc., 2011. All rights reserved.
PAGE 9
5.0 Typical Operating Characteristics (continued) MSL3086/MSL3087/MSL3088 (Typical Operating Circuit, unless otherwise stated, TA = +25°C, unless otherwise noted) BOOST REGULATOR GATE DRIVE RISE/FALL WITH 3nF CAPACITIVE LOAD Datasheet DRIVER RISE TIME 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 (VLED), which shows little disturbance.
PAGE 10
MSL3086/MSL3087/MSL3088 Datasheet 6.0 Block Diagram Block Diagram Figure 6.1.
PAGE 11
MSL3086/MSL3087/MSL3088 Datasheet 7.0 Typical Application Circuit Typical Application Circuit Figure 7.1. Typical Application Circuit VPWR = 6.5V TO 16V 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 43.2k SDA MSL3086 FB 1 30k PWM 100nF FLTB COMP 3.12k 220pF 23 SCTH STR0 STR1 ILED STR2 STR3 93.1k STR4 STR5 15 FDC5612 12.
PAGE 12
8.0 Detailed Description The MSL3086/88 are LED drivers with eight internal current regulators capable of driving up to 60mA LED current each. The MSL3086/88 feature an integrated boost regulator controller to power the LED strings. They provide a complete LED driver solution for multi-LED string applications. A single resistor sets the LED current for all strings.
PAGE 13
8.3 Boost Regulator Overview The MSL3086/88 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 for this purpose (Figure 8.1).
PAGE 14
8.5 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.
PAGE 15
8.11 Internal Supervisory and LDO The MSL3086/88 have a Power-On-Reset circuit that monitors VIN and allows operation when VIN exceeds 4.25V. The MSL3086/88 have 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.
PAGE 16
9.0 Application Information 9.1 Bypassing VIN and PVIN Bypass VIN with a capacitor of at least 1µF. Bypass PVIN with at least 2µF. Place all bypass capacitors close to the device. 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 on-current in Amps. The maximum LED current per-string is 60mA.
PAGE 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 MSL3086/88 boost regulators use external MOSFET switches and current sense resistors, allowing a wide variety of input/output voltage combinations and load currents. The boost regulator switching frequency is 625kHz.
PAGE 18
MSL3086/MSL3087/MSL3088 Da required to power the LEDs. This ensures that there is sufficient voltage available for LED current control, 9.6 The Efficiency supply noiseOptimizer rejection,(EO) while minimizing power dissipation. It does this my injecting a small current into the steps (8-bit resolution). A256 voltage divider from the boost regulator output voltage to FB sets the regulation voltage (RTOP and RBOTTOM in Figure 8.1 on page 13).
PAGE 19
for the current regulator headroom brings VOUT(MIN) to 35.5V and VOUT(MAX) to 38.5. Next determine RTOP using:  VOUT ( MIN) V f ( MIN )  # ofLEDs  0.5 , and Figure 5. Efficiency Optimizer (EO) VOUT ( MAX )  VOUT ( MIN ) . RTOP   VOUT ( MAX ) V f ( MAX )  # ofLEDs  0.5 , 365  10 6 9.
PAGE 20
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.
PAGE 21
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. thelower ESR of zero Assure that thethe loop crossover frequency is at least 1/5ththofofthe thefrequency. ESR zero fESRZ, the right-half-plane zero fR Next determine desired crossover frequency as 1/5 or the switching frequency fSW.
PAGE 22
10.0 LED Dimming Control 10.1 External and I2C Control of LED Brightness Control MSL3086 LED brightness using Pulse Width Modulation (PWM) with a PWM signal applied to the external PWM input. The PWM dimming signals (outputs) take the frequency and duty cycle of the input signal but are staggered in time so that they start at evenly spaced intervals relative to the PWM input signal.
PAGE 23
11.0 Ordering Information Table 11.1 Ordering Information PART DESCRIPTION MSL3086-IU 8-CH LED driver with integrated boost controller and resistor based LED Short Circuit threshold setting. MSL3088-IU 8-CH LED driver with integrated boost and SYNC input. Atmel Corporation 2325 Orchard Parkway San Jose, CA 95131 USA Tel: (+1)(408) 441-0311 Fax: (+1)(408) 487-2600 www.atmel.