19-0655; Rev 1; 4/07 KIT ATION EVALU E L B AVAILA Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller Features The MAX16807/MAX16808 are integrated, high-efficiency white or RGB LED drivers. They are designed for LCD backlighting and other LED lighting applications with multiple strings of LEDs. The MAX16807/ MAX16808’s current-mode PWM controller regulates the necessary voltage to the LED array. Depending on the input voltage and LED voltage range, it can be used with boost or buck-boost (SEPIC) topologies. The MAX16807/MAX16808 feature an 8V to 26.5V input voltage range. A wide range of adjustable frequency (20kHz to 1MHz) allows design optimization for efficiency and minimum board space. o Eight Constant-Current Output Channels (Up to 55mA Each) o ±3% Current Matching Among Outputs o Paralleling Channels Allows Higher Current per LED String o Outputs Rated for 36V Continuous Voltage o Output-Enable Pin for PWM Dimming (Up to 30kHz) o One Resistor Sets LED Current for All Channels o Wide Dimming Ratio Up to 5000:1 o Low Current-Sense Reference (300mV) for High Efficiency o 8V to 26.5V Input Voltage or Higher with External Biasing Devices o Open LED Detection (MAX16808) o 4-Wire Serial Interface to Control Individual Output Channels The MAX16807/MAX16808 LED drivers include eight open-drain, constant-current-sinking LED driver outputs rated for 36V continuous operation. The LED currentcontrol circuitry achieves ±3% current matching among strings and enables paralleling of outputs for LED string currents higher than 55mA. The output-enable pin is used for simultaneous PWM dimming of all output channels. Dimming frequency range is 50Hz to 30kHz and dimming ratio is up to 5000:1. The constant-current outputs are single resistor programmable and the LED current can be adjusted up to 55mA per output channel. Applications LCD White or RGB LED Backlighting: LCD TVs, Desktop, and Notebook Panels Automotive Navigation, Heads-Up, and Infotainment Displays Industrial and Medical Displays Ambient, Mood, and Accent Lighting The MAX16807/MAX16808 operate either in stand-alone mode or with a microcontroller (µC) using an industrystandard, 4-wire serial interface. The MAX16808 includes circuitry that automatically detects open-circuit LEDs. The MAX16807/MAX16808 include overtemperature protection, operate over the full -40°C to +125°C temperature range, and are available in a thermally enhanced, 28-pin TSSOP exposed paddle package. Ordering Information TEMP RANGE PART PIN-PACKAGE PKG CODE MAX16807AUI+ -40°C to +125°C 28 TSSOP-EP* U28ME-1 MAX16808AUI+ -40°C to +125°C 28 TSSOP-EP* U28ME-1 +Denotes a lead-free package. *EP = Exposed paddle. Pin Configurations appear at end of data sheet. Typical Operating Circuits VIN VOUT L D COUT Q R1 LEDs CC2 RCS CC1 RC1 R2 OUT CS AGND VCC 3V TO 5.5V COMP CIN FB V+ CBYP PGND OUT0 OUT1 MAX16807 MAX16808 LE DIN OUT2 OUT3 OUT4 CLK DOUT OE OUT5 OUT6 OUT7 SET RTCT REF STAND-ALONE OPERATION RT RSET CREF CT Typical Operating Circuits continued at end of data sheet. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX16807/MAX16808 General Description MAX16807/MAX16808 Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller ABSOLUTE MAXIMUM RATINGS VCC to AGND..........................................................-0.3V to +30V Current into VCC (VCC > 24V)...........................................±30mA V+ to PGND..............................................................-0.3V to +6V OUT to AGND.............................................-0.3V to (VCC + 0.3V) OUT Current (10µs duration) .................................................±1A FB, COMP, CS, RTCT, REF to AGND.......................-0.3V to +6V COMP Sink Current.............................................................10mA OUT0–OUT7 to PGND............................................-0.3V to +40V DIN, CLK, LE, OE, SET to PGND..................-0.3V to (V+ + 0.3V) DOUT Current...................................................................±10mA OUT0–OUT7 Sink Current...................................................60mA Total PGND Current ..........................................................480mA Continuous Power Dissipation (TA = +70°C) 28-Pin TSSOP (derate 27mW/°C* above +70°C) .......2162mW Operating Temperature Range .........................-40°C to +125°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C *Per JEDEC51 Standard (Multilayer Board). Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (PWM CONTROLLER) (VCC = +15V, V+ = +3V to +5.5V referenced to PGND, RT = 10kΩ, CT = 3.3nF, REF = open, COMP = open, CREF = 0.1µF, VFB = 2V, CS = AGND, AGND = PGND = 0V; all voltages are measured with respect to AGND, unless otherwise noted. TJ = TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 5 5.05 V 0.4 4 mV 50 mV REFERENCE IREF = 1mA, TJ = +25°C Output Voltage VREF Line Regulation ΔVLINE 12V< VCC < 25V, IREF = 1mA Load Regulation ΔVLOAD 1mA < IREF < 20mA 4.95 6 Total Output-Voltage Variation VREFT (Note 2) 4.875 Output Noise Voltage VNOISE 10Hz < f < 10kHz Output Short-Circuit Current ISHORT VREF = 0V 30 Initial Accuracy TJ = +25°C 51 Voltage Stability 12V < VCC < 25V 5.125 50 V µV 180 mA 54 57 kHz 0.2 0.5 OSCILLATOR Temperature Stability RTCT Ramp Peak-to-Peak RTCT Ramp Valley % 1.7 V 1.1 Discharge Current IDIS Frequency Range fOSC % 1 V VRTCT = 2V, TJ = +25°C 7.9 8.3 8.7 VRTCT = 2V, -40oC ≤ TJ ≤ +125°C 7.5 8.3 9.0 20 mA 1000 kHz 2.50 2.55 V -0.01 -0.1 ERROR AMPLIFIER FB Input Voltage VFB FB shorted to COMP 2.45 Input Bias Current IB(FB) Open-Loop Gain AVOL Unity-Gain Bandwidth fGBW Power-Supply Rejection Ratio PSRR 12V ≤ VCC ≤ 25V 60 80 dB COMP Sink Current ISINK VFB = 2.7V, VCOMP = 1.1V 2 6 mA 0.5 1.2 COMP Source Current ISOURCE 2V ≤ VCOMP ≤ 4V VFB = 2.3V, VCOMP = 5V COMP Output-Voltage High VOH VFB = 2.3V, RCOMP = 15kΩ to AGND COMP Output-Voltage Low VOL VFB = 2.7V, RCOMP = 15kΩ to VREF 2 5 µA 100 dB 1 MHz 1.8 5.8 0.1 _______________________________________________________________________________________ mA V 1.1 V Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller (VCC = +15V, V+ = +3V to +5.5V referenced to PGND, RT = 10kΩ, CT = 3.3nF, REF = open, COMP = open, CREF = 0.1µF, VFB = 2V, CS = AGND, AGND = PGND = 0V; all voltages are measured with respect to AGND, unless otherwise noted. TJ = TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS CURRENT-SENSE AMPLIFIER Current-Sense Gain ACS Maximum Current-Sense Signal VCS_MAX (Notes 3, 4) 2.85 3.00 3.40 V/V (Note 3) 0.275 0.300 0.325 V 12V ≤ VCC ≤ 25V 70 VCOMP = 0V -1 tPWM 50mV overdrive 60 OUT Low-Side On-Resistance VRDS_ONL ISINK = 200mA OUT High-Side On-Resistance VRDS_ONH ISOURCE = 100mA Power-Supply Rejection Ratio PSRR Current-Sense Input Bias Current ICS Current Sense to OUT Delay dB -2.5 µA ns MOSFET DRIVER Source Current (Peak) ISOURCE CLOAD = 10nF Sink Current (Peak) TJ = -40°C to +85°C (Note 2) 4.5 10 TJ = -40°C to +125°C 4.5 12 TJ = -40°C to +85°C (Note 2) 3.5 7.5 TJ = -40°C to +125°C 3.5 10 2 Ω Ω A ISINK CLOAD = 10nF 1 A Rise Time tR CLOAD = 1nF 15 ns Fall Time tF CLOAD = 1nF 22 ns UNDERVOLTAGE LOCKOUT/STARTUP Startup Voltage Threshold VCC_START 7.98 8.4 8.82 V Minimum Operating Voltage After Turn-On VCC_MIN 7.1 7.6 8.0 V Undervoltage-Lockout Hysteresis UVLOHYST 0.8 V PULSE-WIDTH MODULATION (PWM) Maximum Duty Cycle DMAX Minimum Duty Cycle DMIN 94.5 96 97.5 % 0 % SUPPLY CURRENT Startup Supply Current VCC = 7.5V 32 65 µA Operating Supply Current ISTART ICC VFB = VCS = 0V 3 5 mA VCC Zener Voltage VZ ICC = 25mA 24 26.5 V _______________________________________________________________________________________ 3 MAX16807/MAX16808 ELECTRICAL CHARACTERISTICS (PWM CONTROLLER) (continued) MAX16807/MAX16808 Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller ELECTRICAL CHARACTERISTICS (LED DRIVER) (V+ = +3V to +5.5V, AGND = PGND = 0V; all voltages are measured with respect to PGND, unless otherwise noted. TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL Operating Supply Voltage Output Voltage CONDITIONS V+ MIN TYP 3.0 VOUT_ MAX UNITS 5.5 V 36 V Standby Current (Interface Idle, All Output Ports High Impedance) RSET = 360Ω, DIN, LE, CLK = PGND or V+, OE = V+, DOUT unconnected 3.6 4.5 mA Standby Current (Interface Active, All Output Ports High Impedance) RSET = 360Ω, fCLK = 5MHz, OE = V+, DIN, LE = PGND or V+, DOUT unconnected 3.8 4.8 mA RSET = 360Ω, OE = PGND, DIN, LE = V+, DOUT unconnected 17 30 mA Supply Current (Interface Idle, All Output Ports Active Low) I+ INTERFACE (DIN, CLK, DOUT, LE, OE) Input-Voltage High (DIN, CLK, LE, OE) VIH Input-Voltage Low (DIN, CLK, LE, OE) VIL Hysteresis Voltage (DIN, CLK, LE, OE) VHYST Input Leakage Current (DIN, CLK) ILEAK 0.7 x V+ V 0.3 x V+ 0.8 -1 V V +1 µA OE Pullup Current to V+ IOE V+ = 5.5V, OE = PGND 0.25 1.5 25.0 µA LE Pulldown Current to PGND ILE V+ = 5.5V, LE = V+ 0.25 1.5 25.0 µA Output-Voltage High (DOUT) VOH ISOURCE = 4mA Output-Voltage Low (DOUT) VOL ISINK = 4mA OUT_ Output Current IOUT_ 4 TA = -40°C, VOUT = 1V to 2.5V, RSET = 360Ω V 0.5 46.5 50 VOUTTH V+ = 5.5V, OE = V+ V 53.5 mA 43 57 OE = V+ OUT_ Leakage Current OUT_ Fault Detection Threshold (MAX16808) 0oC ≤ TA ≤ +125°C, VOUT = 1V to 2.5V, RSET = 360Ω V+ - 0.5V 1 0.8 _______________________________________________________________________________________ µA V Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller (V+ = +4.5V to +5.5V, AGND = PGND = 0V; all voltages are measured with respect to PGND, unless otherwise noted. TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 5) PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS INTERFACE TIMING CHARACTERISTICS CLK Clock Period tCP 40 ns CLK Pulse-Width High tCH 19 ns CLK Pulse-Width Low tCL 19 ns DIN Setup Time tDS 4 ns DIN Hold Time tDH 8 ns DOUT Propagation Delay tDO 50 ns DOUT Rise Time tDR CDOUT = 10pF, 20% to 80% 10 ns DOUT Fall Time tDF CDOUT = 10pF, 80% to 20% 10 ns LE Pulse-Width High tLW 20 LE Setup Time tLS 15 LE Rising to OUT_ Rising Delay 12 ns ns tLRR (Note 6) 110 ns LE Rising to OUT_ Falling Delay tLRF (Note 6) 325 ns CLK Rising to OUT_ Rising Delay tCRR (Note 6) 110 ns CLK Rising to OUT_ Falling Delay tCRF (Note 6) 325 ns OE Rising to OUT_ Rising Delay tOER (Note 6) 110 ns OE Falling to OUT_ Falling Delay tOEF (Note 6) 325 ns OUT_ Turn-On Fall Time tF 80% to 20% (Note 6) 210 ns OUT_ Turn-Off Rise Time tR 20% to 80% (Note 6) 130 ns _______________________________________________________________________________________ 5 MAX16807/MAX16808 5V TIMING CHARACTERISTICS MAX16807/MAX16808 Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller 3.3V TIMING CHARACTERISTICS (V+ = +3V to < +4.5V, AGND = PGND = 0V; all voltages are measured with respect to PGND, unless otherwise noted. TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 5) PARAMETERS SYMBOL CONDITIONS MIN TYP MAX UNITS INTERFACE TIMING CHARACTERISTICS CLK Clock Period tCP 52 ns CLK Pulse-Width High tCH 24 ns CLK Pulse-Width Low tCL 24 ns DIN Setup Time tDS 4 ns DIN Hold Time tDH 8 ns DOUT Propagation Delay tDO DOUT Rise Time tDR CDOUT = 10pF, 20% to 80% DOUT Fall Time tDF CDOUT = 10pF, 80% to 20% LE Pulse-Width High tLW 20 ns LE Setup Time tLS 15 ns 12 70 ns 12 ns 12 ns LE Rising to OUT_ Rising Delay tLRR (Note 6) 140 ns LE Rising to OUT_ Falling Delay tLRF (Note 6) 350 ns CLK Rising to OUT_ Rising Delay tCRR (Note 6) 140 ns CLK Rising to OUT_ Falling Delay tCRF (Note 6) 350 ns OE Rising to OUT_ Rising Delay tOER (Note 6) 140 ns OE Falling to OUT_ Falling Delay tOEF (Note 6) 350 ns OUT_ Turn-On Fall Time tF 80% to 20% (Note 6) 275 ns OUT_ Turn-Off Rise Time tR 20% to 80% (Note 6) 150 ns Note 1: Note 2: Note 3: Note 4: Note 5: Note 6: 6 All devices are 100% production tested at TJ = +25°C and +125°C. Limits to -40°C are guaranteed by design. Guaranteed by design, not production tested. Parameter is measured at trip point of latch with VFB = 0V. Gain is defined as A = ΔVCOMP / ΔVCS, 0.05V ≤ VCS ≤ 0.25V. See Figures 3 and 4. A 65Ω pullup resistor is connected from OUT_ to 5.5V. Rising refers to VOUT_ when current through OUT_ is turned off and falling refers to VOUT_ when current through OUT_ is turned on. _______________________________________________________________________________________ Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller VCC FALLING 6 ICC (μA) VCC (V) 7 VCC = 7.5V 39 5 4 5.1 CT = 560pF 4.9 37 4.7 35 4.5 ICC (mA) 8 41 MAX16807 toc02 VCC RISING MAX16807 toc01 9 33 MAX16807 toc03 BOOTSTRAP UVLO vs. TEMPERATURE 10 OPERATING SUPPLY CURRENT vs. TEMPERATURE AFTER STARTUP (fOSC = fSW = 300kHz) STARTUP CURRENT vs. TEMPERATURE 4.3 31 4.1 29 3.9 27 3.7 3 2 HYSTERESIS 1 0 25 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) REFERENCE VOLTAGE vs. TEMPERATURE REFERENCE VOLTAGE vs. REFERENCE LOAD CURRENT REFERENCE VOLTAGE vs. SUPPLY VOLTAGE 5.04 5.00 4.98 4.85 4.992 4.990 4.988 4.986 4.75 4.92 4.70 4.90 4.65 4.984 4.982 4.980 0 10 20 30 40 50 60 IREF (mA) OSCILLATOR FREQUENCY (fOSC) vs. TEMPERATURE OSCILLATOR RT/CT DISCHARGE CURRENT vs. TEMPERATURE 510 500 490 480 470 7.98 7.96 7.94 7.92 7.90 450 7.88 16 18 20 22 24 0.40 0.38 0.36 8.00 460 14 26 CURRENT-SENSE TRIP THRESHOLD vs. TEMPERATURE CS THRESHOLD (V) 520 VRT/CT = 2V 8.02 12 VCC (V) MAX16807 toc08 530 8.04 RT/CT DISCHARGE CURRENT (mA) MAX16807 toc07 TEMPERATURE (°C) RT = 3.65kΩ CT = 560pF 10 70 MAX16807 toc09 4.94 -40 -25 -10 5 20 35 50 65 80 95 110 125 OSCILLATOR FREQUENCY (kHz) 4.994 4.90 4.80 IREF = 20mA 4.96 540 4.996 VREF (V) VREF (V) VREF (V) IREF = 1mA 5.00 IREF = 1mA 4.998 4.95 5.02 MAX16807 toc06 5.06 5.000 MAX16807 toc05 5.05 MAX16807 toc04 5.08 550 3.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 0.34 0.32 0.30 0.28 0.26 0.24 0.22 0.20 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 20 35 50 65 80 95 110 125 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) _______________________________________________________________________________________ 7 MAX16807/MAX16808 Typical Operating Characteristics (VCC = +15V, V+ = 3V to 5.5V, RT = 10kΩ, CT = 3.3nF, VREF = COMP = open, CREF = 0.1µF, VFB = 2V, CS = AGND = PGND = 0V. Typical values are at TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VCC = +15V, V+ = 3V to 5.5V, RT = 10kΩ, CT = 3.3nF, VREF = COMP = open, CREF = 0.1µF, VFB = 2V, CS = AGND = PGND = 0V. Typical values are at TA = +25°C, unless otherwise noted.) CT = 560pF CT = 100pF 10 1 RDS_ON (Ω) CT = 10nF CT = 4.7nF CT = 3.3nF CT = 2.2nF 0.1 10 ISINK = 200mA 9 8 7 6 5 4 3 2 1 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 FREQUENCY (Hz) TEMPERATURE (°C) TEMPERATURE (°C) PROPAGATION DELAY FROM CURRENT-LIMIT COMPARATOR TO OUT vs. TEMPERATURE ERROR-AMPLIFIER OPEN-LOOP GAIN AND PHASE vs. FREQUENCY COMP VOLTAGE LEVEL TO TURN OFF DEVICE vs. TEMPERATURE 1M 10M MAX16807 toc14 80 100 GAIN (dB) 60 50 40 30 20 -65 PHASE 60 1.7 0 -165 1.6 -190 10k 100k 1M 10M 100M 1.5 0.01 1 10 100 1k -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) FREQUENCY (Hz) SUPPLY CURRENT vs. SUPPLY VOLTAGE (INTERFACE IDLE, ALL OUTPUTS OFF, RSET = 720Ω) 2.00 MAX16807 toc16 7.0 CT = 100pF 6.0 5.5 ICC (mA) 1.8 -140 SUPPLY CURRENT vs. OSCILLATOR FREQUENCY 4.0 1.9 20 TEMPERATURE (°C) 4.5 2.0 -115 -20 5.0 -90 2.1 40 -40 -25 -10 5 20 35 50 65 80 95 110 125 6.5 -40 GAIN 80 10 0 VCC = 15V 2.2 -15 120 70 2.3 10 VCOMP (V) 90 140 PHASE (DEGREES) MAX16807 toc13 100 TA = +125°C TA = -40°C 3.5 TA = +125°C MAX16807 toc17 100k TA = +85°C 1.95 TA = +25°C 1.90 TA = -40°C 1.85 3.0 2.5 1.80 2.0 20 120 220 320 420 520 620 720 820 920 1020 FREQUENCY (kHz) 8 3.0 3.5 MAX16807 toc15 -40 -25 -10 5 20 35 50 65 80 95 110 125 10k SUPPLY CURRENT (mA) RT (kΩ) CT = 220pF ISOURCE = 100mA MAX16807 toc12 CT = 1nF 5.0 4.8 4.6 4.4 4.2 4.0 3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4 2.2 2.0 RDS_ON (Ω) MAX16807 toc10 1000 100 OUT IMPEDANCE vs. TEMPERATURE (RDS_ON NMOS DRIVER) OUT IMPEDANCE vs. TEMPERATURE (RDS_ON PMOS DRIVER) MAX16807 toc11 TIMING RESISTANCE vs. OSCILLATOR FREQUENCY PROPAGATION DELAY (ns) MAX16807/MAX16808 Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller MAX16807 toc18 20 TA = +125°C 3.65 TA = +85°C 3.60 TA = +25°C TA =-40°C 3.55 TA = +125°C TA = +85°C 17 SUPPLY CURRENT (mA) 14 11 TA = -40°C 8 3.50 TA = +25°C 5 3.0 3.5 4.0 4.5 5.0 5.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) SUPPLY CURRENT vs. SUPPLY VOLTAGE (INTERFACE IDLE, ALL OUTPUTS ON, RSET = 360Ω) OUT_ CURRENT vs. OUT_ VOLTAGE (RSET = 720Ω, V+ = 3.3V) 19 16 13 25 TA = +25°C TA = -40°C TA = +25°C 20 15 TA = +85°C TA = +125°C 10 5 TA = -40°C 0 10 3.0 3.5 4.0 4.5 5.0 0 5.5 0.5 1.0 1.5 2.0 2.5 SUPPLY VOLTAGE (V) OUT_ VOLTAGE (V) OUT_ CURRENT vs. OUT_ VOLTAGE (RSET = 360Ω, V+ = 3.3V) OUT_ CURRENT vs. OUT_ VOLTAGE (RSET = 720Ω, V+ = 5.0V) 30 MAX16807 toc22 60 40 TA = -40°C TA = +25°C 30 20 TA = +85°C TA = +125°C 10 25 OUT_ CURRENT (mA) 50 OUT_ CURRENT (mA) MAX16807 toc21 TA = +125°C TA = +85°C OUT_ CURRENT (mA) SUPPLY CURRENT (mA) 22 30 MAX16807 toc20 25 5.5 3.0 MAX16807 toc23 SUPPLY CURRENT (mA) 3.70 SUPPLY CURRENT vs. SUPPLY VOLTAGE (INTERFACE IDLE, ALL OUTPUTS ON, RSET = 720Ω) MAX16807 toc19 SUPPLY CURRENT vs. SUPPLY VOLTAGE (INTERFACE IDLE, ALL OUTPUTS OFF, RSET = 360Ω) 20 TA = -40°C TA = +25°C 15 TA = +85°C 10 TA = +125°C 5 0 0 0 0.5 1.0 1.5 2.0 OUT_ VOLTAGE (V) 2.5 3.0 0 0.5 1.0 1.5 2.0 2.5 3.0 OUT_ VOLTAGE (V) _______________________________________________________________________________________ 9 MAX16807/MAX16808 Typical Operating Characteristics (continued) (VCC = +15V, V+ = 3V to 5.5V, RT = 10kΩ, CT = 3.3nF, VREF = COMP = open, CREF = 0.1µF, VFB = 2V, CS = AGND = PGND = 0V. Typical values are at TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VCC = +15V, V+ = 3V to 5.5V, RT = 10kΩ, CT = 3.3nF, VREF = COMP = open, CREF = 0.1µF, VFB = 2V, CS = AGND = PGND = 0V. Typical values are at TA = +25°C, unless otherwise noted.) OUT_ CURRENT vs. SUPPLY VOLTAGE V+ (RSET = 720Ω, VOUT = 2V) OUT_ CURRENT vs. OUT_ VOLTAGE (RSET = 360Ω, V+ = 5.0V) 50 MAX16807 toc25 26.0 MAX16807 toc24 60 40 OUT_ CURRENT (mA) OUT_ CURRENT (mA) 25.5 TA = -40°C TA = +25°C 30 TA = +85°C 20 TA = +125°C TA = +85°C TA = +125°C 25.0 TA = +25°C 24.5 TA = -40°C 10 24.0 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.0 3.5 5.5 TA = +125°C 50 TA = +25°C TA = -40°C MAX16807 toc27 40 OUT_ CURRENT (mA) TA = +85°C 30 20 10 0 48 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 10 5.0 50 MAX16807 toc26 52 49 4.5 OUT_ CURRENT vs. SET RESISTANCE (V+ = 5.0V) OUT_ CURRENT vs. SUPPLY VOLTAGE V+ (RSET = 360Ω, VOUT = 2V) 51 4.0 SUPPLY VOLTAGE (V) OUT_ VOLTAGE (V) OUT_ CURRENT (mA) MAX16807/MAX16808 Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller 5.0 5.5 0 1 2 3 RSET (kΩ) ______________________________________________________________________________________ 4 5 Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller PIN NAME 1, 13, 28 N.C. FUNCTION 2 AGND 3 OUT MOSFET Driver Output OUT. Connects to the gate of the external n-channel MOSFET. 4 VCC Power-Supply Input. Bypass VCC to AGND with a 0.1µF ceramic capacitor or a parallel combination of a 0.1µF and a higher value ceramic capacitor. 5V Reference Output. Bypass REF to AGND with a 0.1µF ceramic capacitor. No Connection. Not internally connected. Leave unconnected. Analog Ground 5 REF 6–9 OUT4–OUT7 10 OE 11 DOUT 12 SET LED Current Setting. Connect RSET from SET to PGND to set the LED current. 14 V+ LED Driver Positive Supply Voltage. Bypass V+ to PGND with a 0.1µF ceramic capacitor. 15, 16 PGND 17 DIN Serial-Data Input 18 CLK Serial-Clock Input 19 LE 20–23 OUT0–OUT3 24 COMP 25 FB Error-Amplifier Inverting Input 26 CS PWM Controller Current-Sense Input 27 RTCT — EP LED Driver Outputs. OUT4–OUT7 are open-drain, constant-current-sinking outputs rated for 36V. Active-Low Output Enable Input. Drive OE low to PGND to enable the OUT0–OUT7. Drive OE high to disable OUT0–OUT7. Serial-Data Output. Data is clocked out of the 8-bit internal shift register to DOUT on CLK’s rising edge. Power Ground Latch-Enable Input. Data is loaded transparently from the internal shift register(s) to the output latch(es) while LE is high. Data is latched into the output latch(es) on LE’s falling edge, and retained while LE is low. LED Driver Outputs. OUT0–OUT3 are open-drain, constant-current-sinking outputs rated for 36V. Error-Amplifier Output PWM Controller Timing Resistor/Capacitor Connection. A resistor RT from RTCT to REF and a capacitor CT from RTCT to AGND set the oscillator frequency. Exposed Paddle. Connect to the ground plane for improved power dissipation. Do not use as the only ground connection for the part. Detailed Description The MAX16807/MAX16808 LED drivers include an internal switch-mode controller that can be used as boost or buck-boost (SEPIC) converters to generate the voltage necessary to drive the multiple strings of LEDs. These devices incorporate an integrated low-side driver, a programmable oscillator (20kHz to 1MHz), an error amplifier, a low-voltage (300mV) current sense for higher efficiency, and a 5V reference to power up external circuitry (see Figures 1a, 1b, and 1c). The MAX16807/MAX16808 LED drivers include a 4-wire serial interface and a current-mode PWM controller to generate the necessary voltage for driving eight opendrain, constant-current-sinking output ports. The drivers use current-sensing feedback circuitry (not simple current mirrors) to ensure very small current variations over the full allowed range of output voltage (see the Typical Operating Characteristics). The 4-wire serial interface comprises an 8-bit shift register and an 8-bit transparent latch. The shift register is written through a clock input, CLK, and a data input, DIN, and the data propagates to a data output, DOUT. The data output allows multiple drivers to be cascaded and operated together. The contents of the 8-bit shift register are loaded into the transparent latch through a latch-enable input, LE. The latch is transparent to the shift register outputs when high and latches the current state on the falling edge of LE. Each driver output is an open-drain, constant-current sink that should be connected to the cath- ______________________________________________________________________________________ 11 MAX16807/MAX16808 Pin Description ode of a string of LEDs connected in series. The constant-current capability is up to 55mA per output, set for all 8 outputs by an external resistor, R SET . The devices can operate in a stand-alone mode (see the Typical Operating Circuits.) The MAX16808 includes circuitry that automatically detects open-circuit LEDs. Fault status is loaded into the serial-interface shift register when LE goes high and is automatically shifted out on DOUT when the next data transmission is shifted in. The number of channels can be expanded by using the MAX6970 and MAX6971 family in conjunction with the MAX16807 and MAX16808. UVLO MAX16807 REFERENCE 2.5V VOLTAGEDIVIDER PREREG 5V VCC 26.5V THERMAL SHUTDOWN EN_REF BG SNS VDD REF 5V REG REG_OK DELAY VOLTAGE DIVIDER AGND VCC 300mV ILIM S R OUT Q CS CPWM 2R VEA CLK FB COMP R OSC Q RTCT CLK SERIAL-TO-PARALLEL SHIFT REGISTER DIN D0 D1 D2 D3 D4 D5 D6 D7 D5 D6 D7 DOUT OUTPUT LATCHES LE D0 D1 D2 D3 D4 POWER-ON RESET V+ OE V+ CONSTANT-CURRENT SINK THERMAL SHUTDOWN D0 D1 D2 D3 D4 D5 D6 D7 CURRENT REFERENCE OUT7 OUT6 OUT5 OUT4 OUT3 OUT2 OUT1 PGND OUT0 MAX16807/MAX16808 Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller Figure 1a. Internal Block Diagram (MAX16807) 12 ______________________________________________________________________________________ SET Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller REFERENCE 2.5V MAX16807/MAX16808 UVLO MAX16808 VOLTAGEDIVIDER PREREG 5V VCC 26.5V THERMAL SHUTDOWN EN_REF BG SNS VDD REF 5V REG REG_OK DELAY VOLTAGE DIVIDER AGND VCC 300mV ILIM S R OUT Q CS CPWM 2R VEA CLK FB COMP R OSC Q RTCT CLK SERIAL-TO-PARALLEL SHIFT REGISTER DIN D0 D1 D2 D3 D4 D5 D6 D7 D5 D6 D7 DOUT OUTPUT LATCHES LE D0 D1 D2 D3 D4 POWER-ON RESET V+ OE V+ CONSTANT-CURRENT SINK THERMAL SHUTDOWN D0 D1 D2 D3 D4 D5 D6 D7 CURRENT REFERENCE SET OPEN LED FAULT DETECTION OUT7 OUT6 OUT5 OUT4 OUT3 OUT2 OUT1 OUT0 PGND Figure 1b. Internal Block Diagram (MAX16808) ______________________________________________________________________________________ 13 MAX16807/MAX16808 Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller V+ 68W/L 1.23V W/L OUT_ 1.23 REST 995R R SET PGND Figure 1c. OUT_ Driver Internal Diagram Switch-Mode Controller Current-Mode Control Loop The advantages of current-mode control over voltagemode control are twofold. First, there is the feed-forward characteristic brought on by the controller’s ability to adjust for variations in the input voltage on a cycleby-cycle basis. Second, the stability requirements of the current-mode controller are reduced to that of a single pole system unlike the double pole in the voltagemode control scheme. The MAX16807/MAX16808 use a current-mode control loop where the output of the error amplifier is compared to the current-sense voltage (VCS). When the current-sense signal is lower than the inverting input of the CPWM comparator, the output of the comparator is low and the switch is turned on at each clock pulse. When the current-sense signal is higher than the inverting input of the CPWM comparator, the output is high and the switch is turned off. Undervoltage Lockout (UVLO) The turn-on supply voltage for the MAX16807/ MAX16808 is 8.4V (typ). Once VCC reaches 8.4V, the reference powers up. There is a 0.8V of hysteresis from the turn-on voltage to the UVLO threshold. Once VCC reaches 8.4V, the MAX16807/MAX16808 operate with VCC down to 7.6V (typ). Once VCC goes below 7.6V, the device is in UVLO. When in UVLO, the quiescent supply current into VCC falls back to 32µA (typ), and OUT and REF are pulled low. MOSFET Driver OUT drives an external n-channel MOSFET and swings from AGND to VCC. Ensure that VCC remains below the absolute maximum VGS rating of the external MOSFET. 14 OUT is a push-pull output with the on-resistance of the pMOS typically 3.5Ω and the on-resistance of the nMOS typically 4.5Ω. The driver can source 2A and sink 1A typically. This allows for the MAX16807/ MAX16808 to quickly turn on and off high gate-charge MOSFETs. Bypass VCC with one or more 0.1µF ceramic capacitors to AGND, placed close to the VCC pin. The average current sourced to drive the external MOSFET depends on the total gate charge (QG) and operating frequency of the converter. The power dissipation in the MAX16807/MAX16808 is a function of the average output drive current (IDRIVE). Use the following equation to calculate the power dissipation in the device due to IDRIVE: IDRIVE = (QG x fSW) PD = (IDRIVE + ICC) x VCC where I CC is the operating supply current. See the Typical Operating Characteristics for the operating supply current at a given frequency. Error Amplifier The MAX16807/MAX16808 include an internal error amplifier. The inverting input is at FB and the noninverting input is internally connected to a 2.5V reference. Set the output voltage using a resistive divider between output of the converter VOUT, FB, and AGND. Use the following formula to set the output voltage: R1 ⎞ ⎛ VOUT = ⎜1 + ⎟ x VFB ⎝ R2 ⎠ where VFB = 2.5V. Oscillator The oscillator frequency is programmable using an external capacitor and a resistor at RTCT (see RT and CT in the Typical Operating Circuits). RT is connected from RTCT to the 5V reference (REF), and CT is connected from RTCT to AGND. REF charges CT through RT until its voltage reaches 2.8V. CT then discharges through an 8.3mA internal current sink until CT’s voltage reaches 1.1V, at which time CT is allowed to charge through RT again. The oscillator’s period is the sum of the charge and discharge times of CT. Calculate the charge time as follows: tC = 0.57 x RT x CT where t C is in seconds, R T in ohms (Ω), and C T in Farads (F). The discharge time is then: tD = (RT x CT x 1000) / [(4.88 x RT) - (1.8 x 1000)] ______________________________________________________________________________________ Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller RCS = The oscillator frequency is then: fOSC = 1 (tC + tD) Reference Output REF is a 5V reference output that can source 20mA. Bypass REF to AGND with a 0.1µF capacitor. IP-P is the peak current that flows through the MOSFET. When the voltage produced by this current (through the current-sense resistor) exceeds the current-limit comparator threshold, the MOSFET driver (OUT) turns the switch off within 60ns. In most cases, a small RC filter is required to filter out the leading-edge spike on the sense waveform. Set the time constant of the RC filter at 50ns. Current Limit The MAX16807/MAX16808 include a fast current-limit comparator to terminate the on cycle during an overload or a fault condition. The current-sense resistor, RCS, connected between the source of the external MOSFET and AGND, sets the current limit. The CS input has a voltage trip level (VCS) of 0.3V. Use the following equation to calculate RCS: VIN C1 L1 VCS IP − P Buck-Boost (SEPIC) Operation Figure 2 shows a buck-boost application circuit using the MAX16807/MAX16808 in a stand-alone mode of operation. SEPIC topology is necessary when the total forward voltage of the LEDs in a string is such that VOUT can be below or above VIN. VOUT D COUT L2 Q R1 LEDs CC2 RCS CC1 RC1 R2 OUT CS AGND COMP VCC FB CIN 3V TO 5.5V V+ CBYP MAX16807 MAX16808 PGND OUT0 OUT1 OUT2 DIN LE OUT3 OUT4 EXTERNAL CLOCK INPUT EXTERNAL DIM INPUT OUT5 CLK DOUT OE SET OUT6 OUT7 RTCT REF RT RSET CREF CT Figure 2. Buck-Boost (SEPIC) Configuration ______________________________________________________________________________________ 15 MAX16807/MAX16808 where t D is in seconds, R T in ohms (Ω), and C T in Farads (F). MAX16807/MAX16808 Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller LED Driver LE is the latch enable input of the MAX16807/ MAX16808 that transfers data from the 8-bit shift register to its 8-bit output latch (transparent latch). The data is latched on the falling edge of LE (Figure 4). The fourth input (OE) provides output-enable control of the output drivers. When OE is driven high, the outputs (OUT0–OUT7) are forced to high impedance without altering the contents of the output latches. Driving OE low enables the outputs to follow the state of the output latches. OE is independent of the operation of the serial interface operation. Data can be shifted into the serialinterface shift register and latched, regardless of the state of OE. DOUT is the serial-data output that shifts data out from the MAX16807/MAX16808’s 8-bit shift register on the rising edge of CLK. Data at DIN propagates through the shift register and appears at DOUT eight clock cycles later. Table 1 shows the 4-wire serial-interface truth table. 4-Wire Interface The MAX16807/MAX16808 also operate in a standalone mode (see the Typical Operating Circuits). For use with a microcontroller, the MAX16807/MAX16808 feature a 4-wire serial interface using DIN, CLK, LE, OE inputs and DOUT as a data output. This interface is used to write the LED channels’ data to the MAX16807/ MAX16808. The serial-interface data word length is 8 bits, D0–D7. See Figure 3. The functions of the five interface pins are as follows: DIN is the serial-data input, and must be stable when it is sampled on the rising edge of CLK. Data is shifted in MSB first. This means that data bit D7 is clocked in first, followed by 7 more data bits, finishing with the LSB, D0. CLK is the serial-clock input that shifts data at DIN into the MAX16807/MAX16808’s 8-bit shift register on its rising edge. Table 1. 4-Wire Serial-Interface Truth Table BLANKING OUTPUT CONTENTS SERIAL CLOCK SHIFT REGISTER CONTENTS LOAD LATCH CONTENTS INPUT INPUT INPUT CURRENT AT OUT_ DATA INPUT CLK D0 D1 D2 … Dn-1 Dn LE D0 D1 D2 … Dn-1 Dn OE D0 D1 D2 … Dn-1 Dn DIN H H R0 R1 … Rn-2 Rn-1 L L R0 R1 … Rn-2 Rn-1 X R0 R1 R2 … Rn-1 X X X … X P0 P1 P2 … Pn-1 Rn X L R0 R1 R2 … Rn-1 Rn Pn H P0 P1 P2 … Pn-1 Pn L P0 X X X … H L X X P1 P2 L L = Low Logic Level H = High Logic Level X = Don’t Care P = Present State (Shift Register) R = Previous State (Latched) 16 ______________________________________________________________________________________ L … Pn-1 Pn … L L Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller MAX16807/MAX16808 LE tLW tCL tCH tLS tCP CLK tDH tDS D0 D7 DIN tDO D7 DOUT tOEW OE tOEF tOER 80% OUT_ 20% tf tr Figure 3. 4-Wire Serial-Interface Timing Diagram LED Fault Detection (MAX16808) LE tLRF OUT_ LE tLRR OUT_ The MAX16808 includes circuitry that detects open-circuit LEDs automatically. An open-circuit fault occurs when an output is sinking current less than approximately 50% of the programmed current flows. Open circuits are checked just after the falling edge of OE. The fault data is latched on the rising edge of LE and is shifted out when new LED data is loaded into the output latches from the shift register. If one or more output ports are detected with an open-circuit fault, the D6 and D5 bits of DOUT go high. If no open-circuit faults are detected, D6 and D5 are set to low. The data in the other 6 bit positions in DOUT are not altered. Fault status is shifted out on DOUT for the first two rising edges of the clock after the falling edge of LE (see Figure 5). LE is normally taken high after all 8 bits of new LED CLK tCRF OUT_ OE LE CLK tCRR CLK DOUT OUT_ D7 D6 D5 D4 FAULT STATUS BITS Figure 4. LE and CLK to OUT_ Timing Figure 5. Fault Timing ______________________________________________________________________________________ 17 MAX16807/MAX16808 Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller data have been clocked into the shift register(s), and then DOUT outputs data bit D7. A typical fault-detecting application tests all the shifted out data. Bits D0–D4 and D7 are checked against the originally transmitted data to check data-link integrity. Bits D5 and D6 are checked first to see that they contain the same data (validating the status), and second, whether faults are reported or not by the actual logic level. Selecting External Component RSET to Set LED Output Current The MAX16807/MAX16808 use an external resistor, RSET, to set the LED current for outputs OUT0–OUT7. The minimum allowed value of RSET is 330Ω, which sets the output currents to 55mA. The maximum allowed value of RSET is 5kΩ (IOUT_ = 3.6mA) and maximum allowed capacitance at SET is 100pF. Use the following formula to set the output current: RSET = 18, 000 IOUT _ where IOUT_ is the desired output current in milliamps and the value for RSET is in ohms. Overtemperature Cutoff The MAX16807/MAX16808 contain an internal temperature sensor that turns off all outputs when the die temperature exceeds +165°C. The outputs are enabled again when the die temperature drops below +140°C. Register contents are not affected, so when a driver is overdissipating, the external symptom is the load LEDs cycling on and off as the driver repeatedly overheats and cools, alternately turning itself off and then back on again. Stand-Alone Operation In stand-alone operation, the MAX16807/MAX16808 does not use the 4-wire interface (see the Typical Operating Circuits). Connect DIN and LE to V+ provide at least 8 external clock pulses to CLK to enable 8 outputs. This startup pulse sequence can be provided either using an external clock or the PWM signal. The external clock can also be generated using the signal at RTCT and an external comparator. 18 LED Dimming PWM Dimming All the output channels can be dimmed simultaneously by applying a PWM signal (50Hz to 30kHz) to OE. This allows for a wide range of dimming up to a 5000:1 ratio. Each channel can be independently turned on and off using a 4-wire serial interface. The dimming is proportional to the PWM duty cycle. LED Current Amplitude Adjustment Using an analog or digital potentiometer as RSET allows for LED current amplitude adjustment and linear dimming. Computing Power Dissipation Use the following equation to estimate the upper limit power dissipation (PD) for the MAX16807/MAX16808: i = 7 ⎡ ⎤ PD = DUTY x ⎢(V + x I+) + ∑ VOUTi x IOUTi⎥ + (VCC x ICC) ⎢⎣ ⎥⎦ i = 0 where: V+ = supply voltage I+ = operating supply current DUTY = PWM duty cycle applied to OE V OUTi = MAX16807/MAX16808 port output voltage when driving load LED(s) IOUTi = LED drive current programmed by RSET PD = power dissipation. PCB Layout Guidelines Careful PCB layout is critical to achieve low switching losses and clean, stable operation. Use a multilayer board whenever possible for better noise immunity. Protect sensitive analog grounds by using a star ground configuration. Minimize ground noise by connecting AGND, PGND, the input bypass-capacitor ground lead, and the output-filter ground lead to a single point (star ground configuration). Also, minimize trace lengths to reduce stray capacitance, trace resistance, and radiated noise. The trace between the output voltage-divider and the FB pin must be kept short, as well as the trace between AGND and PGND. ______________________________________________________________________________________ Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller Chip Information PROCESS: BiCMOS TOP VIEW + N.C. 1 28 N.C. AGND 2 27 RTCT OUT 3 VCC 4 REF 5 26 CS MAX16807 MAX16808 25 FB 24 COMP OUT4 6 23 OUT3 OUT5 7 22 OUT2 OUT6 8 21 OUT1 OUT7 9 20 OUT0 OE 10 19 LE DOUT 11 18 CLK SET 12 17 DIN N.C. 13 16 PGND V+ 14 15 PGND TSSOP-EP ______________________________________________________________________________________ 19 MAX16807/MAX16808 Pin Configuration Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller MAX16807/MAX16808 Typical Operating Circuits (continued) VIN VOUT L D COUT Q R1 LEDs CC2 RCS CC1 RC1 R2 OUT CS AGND VCC 3V TO 5.5V COMP CIN FB V+ CBYP PGND OUT0 OUT1 MAX16807 MAX16808 LE DIN OUT2 OUT3 OUT4 CLK DOUT OE OUT5 OUT6 OUT7 SET RTCT REF RT RSET CREF 20 STAND-ALONE OPERATION CT ______________________________________________________________________________________ Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller TSSOP 4.4mm BODY.EPS XX XX PACKAGE OUTLINE, TSSOP, 4.40 MM BODY, EXPOSED PAD 21-0108 E 1 1 Revision History Pages changed at Rev 1: 1, 21 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 21 © 2007 Maxim Integrated Products Heaney is a registered trademark of Maxim Integrated Products, Inc. MAX16807/MAX16808 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)