19-1054; Rev 0; 1/08 KIT ATION EVALU E L B AVAILA Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming The MAX16816 is a current-mode, high-brightness LED (HB LED) driver designed to control two external n-channel MOSFETs for single-string LED current regulation. The MAX16816 integrates all the building blocks necessary to implement fixed-frequency HB LED drivers with wide-range dimming control and EEPROMprogrammable LED current binning with a factor of up to 1.6. This device is configurable to operate as a stepdown (buck), step-up (boost), or step-up/step-down (buck-boost) current regulator. Current-mode control with adjustable leading-edge blanking simplifies control-loop design. Adjustable slope compensation stabilizes the current loop when operating at duty cycles above 50%. The MAX16816 operates over a wide input voltage range and is capable of withstanding automotive load-dump events. Multiple MAX16816 devices can be synchronized to each other or to an external clock. The MAX16816 includes a floating dimming driver for brightness control with an external n-channel MOSFET in series with the LED string. HB LEDs using the MAX16816 can achieve efficiencies of over 90% in automotive applications. The MAX16816 also includes a 1.4A source and 2A sink gate driver for driving switching MOSFETs in high-power LED driver applications, such as front light assemblies. Dimming control allows for wide PWM dimming range at frequencies up to 5kHz. Higher dimming ratios (up to 1000:1) are achievable at lower dimming frequencies. The MAX16816 provides user-programmable features through on-chip nonvolatile EEPROM registers. Adjustable features include a programmable soft-start, LED current (binning), external MOSFET gate driver supply voltage, slope compensation, leading-edge blanking time, and disabling/enabling of the RT oscillator. The MAX16816 is available in a 32-pin TQFN package with exposed pad and operates over the -40°C to +125°C automotive temperature range. Features o EEPROM-Programmable LED Current Binning o Wide Input Range: 5.9V to 76V with Cold Start Operation to 5.4V o Integrated Floating Differential LED CurrentSense Amplifier o Floating Dimming Driver Capable of Driving an n-Channel MOSFET o 5% or Better LED Current Accuracy o Multiple Topologies: Buck, Boost, Buck-Boost, SEPIC o Resistor-Programmable Switching Frequency (125kHz to 500kHz) and Synchronization Capability o 200Hz On-Board Ramp Allows Analog-Controlled PWM Dimming and External PWM Dimming o Output Overvoltage, Overcurrent, and LED Short Protection o Enable/Shutdown Input with Shutdown Current Below 45µA Ordering Information PART MAX16816ATJ+ -40°C to +125°C 32 TQFN-EP* T3255M-4 *EP = Exposed pad. Pin Configuration appears at end of data sheet. Typical Operating Circuits BUCK-BOOST CONFIGURATION VIN RCS CCLMP RUV2 LO VCC RUV1 CLMP CS- CS+ DGT QS RD UVEN DRV CUVEN LEDs SNS+ DIM RSENSE DIM SNSQGND MAX16816 REG1 CREG1 HI RT CF RTSYNC ROV1 General Illumination FAULT Navigation and Marine Indicators COMP OV CS FB AGND R1 SGND REG2 DRI ROV2 CREG2 Neon Replacement, Emergency Lighting Signage and Beacons PKG CODE +Denotes a lead-free package. Applications Automotive Exterior: Rear Combination Lights (RCL), Daytime Running Lights (DRL), Fog and Front Lighting, High-Beam/Low-Beam/Turn Lights PINPACKAGE TEMP RANGE C2 C1 R2 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 MAX16816 General Description MAX16816 Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming ABSOLUTE MAXIMUM RATINGS VCC, HI, LO, CLMP to QGND .................................-0.3V to +80V CS+, CS-, DGT, UVEN, FAULT to QGND...............-0.3V to +80V UVEN to QGND ..........................................-0.3V to (VCC + 0.3V) DRV to SGND .........................................................-0.3V to +18V DRI, REG2, DIM to AGND ......................................-0.3V to +18V QGND, SGND to AGND ........................................-0.3V to +0.3V SNS+ to SNS- ...........................................................-0.3V to +6V CS, FB, COMP, SNS+, SNS-, OV, REF, RTSYNC to AGND ................................................-0.3V to +6V REG1, CLKOUT to AGND ........................................-0.3V to +6V CS+ to CS- .............................................................-0.3V to +12V HI to LO ..................................................................-0.3V to +36V CS+, CS-, DGT, CLMP to LO .................................-0.3V to +12V CS+, CS-, DGT, CLMP to LO ........................-0.3V to (HI + 0.3V) HI to CLMP .............................................................-0.3V to +28V Continuous Power Dissipation* (TA = +70°C) 32-Pin TQFN (derate 34.5mW/°C above +70°C) .......2758mW Thermal Resistance θJA ................................................................................29°C/W θJC ...............................................................................1.7°C/W Operating Temperature Range .........................-40°C to +125°C Maximum Junction Temperature .....................................+150°C Storage Temperature Range .............................-60°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C *As per JEDEC 51 standard, Multilayer Board (PCB). 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 (VCC = VUVEN = 14V, CREG1 = 1µF, CREG2 = 1µF, CCLMP = 0.1µF, RT = 25kΩ, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical specifications are at TA = +25°C.) PARAMETER Input Voltage Range Supply Current to VCC Supply Current to HI Shutdown Current to VCC Shutdown Current to HI SYMBOL CONDITIONS VCC IQ_VCC MIN TYP 5.5 MAX UNITS 76 V Exclude current to the gate driver, IREG2 2.7 4.5 mA VHI = 14V 0.5 1.0 mA ISHDN_VCC VUVEN ≤ 300mV 25 45 µA ISHDN_HI VUVEN ≤ 300mV 1 10 µA IQ_HI UVEN VCC UVLO Threshold VCC Threshold Hysteresis UVEN Threshold UVEN Input Current VCC_R VCC rising 5.5 6.0 VCC_F VCC falling 5.0 5.5 VUVR VUVEN rising 1.10 1.244 1.36 VUVF VUVEN falling 1.00 1.145 1.26 IUVEN (VUVEN = 0V and VCC = 14V) (VUVEN = 76V and VCC = 77V) -0.2 VCC_HYS 0.4 V V +0.2 V µA REGULATORS REG1 Regulator Output VREG1 REG1 Dropout Voltage REG1 Load Regulation 2 4.75 5.00 5.25 IREG1 = 2mA, VCC = 5.7V 4.00 4.50 5.25 0.5 1.0 V 25 Ω 1.0 V 25 Ω IREG1 = 2mA (Note 1) ΔV/ΔI VCC = 7.5V, IREG1 = 0 to 2mA VCC ≥ 9.5V, REG2 control register is ‘0011’, IREG2 = 20mA (Note 1) REG2 Dropout Voltage REG2 Load Regulation 0 < IREG1 < 2mA, 7.5V < VCC < 76V ΔV/ΔI 0.5 VCC ≥ 9.5V, REG2 control register is ‘0011’, IREG2 = 0 to 20mA _______________________________________________________________________________________ V Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming (VCC = VUVEN = 14V, CREG1 = 1µF, CREG2 = 1µF, CCLMP = 0.1µF, RT = 25kΩ, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical specifications are at TA = +25°C.) PARAMETER SYMBOL REG2 Regulation Voltage CONDITIONS MIN TYP MAX REG2 control register is ‘0000’, VCC ≥ 7.5V, IREG2 = 1mA 4.75 5 5.25 REG2 control register is ‘0011’, VCC ≥ 9.5V, IREG2 = 1mA 6.65 7.0 7.35 REG2 control register is ‘1111’, VCC ≥ 17.5V, IREG2 = 1mA 13.5 15 16.5 REG2 control register is ‘0000’, VCC = 5.7V, 0 ≤ IREG2 ≤ 20mA 4 4.5 5.25 REG2 control register is ‘0000’, VCC = 7.5V, 0 ≤ IREG2 ≤ 20mA 4.75 5 5.25 REG2 control register is ‘1111’, VCC = 17.5V, 0 ≤ IREG2 ≤ 20mA 13.5 15 16.5 2.0 2.5 3.0 UNITS V HIGH-SIDE REGULATOR (CLMP) (All voltages referred to VLO) (Note 2) CLMP UVLO Threshold VCLMP_TH CLMP UVLO Threshold Hysteresis VCLMP_HYS CLMP Regulator Output Voltage VCLMP rising 0.22 8.7V ≤ (VHI - VLO) ≤ 36V, ICLMP = 1mA VCLMP 5.5 8.0 V 10.0 V (VHI - VLO) - 0.7 5.0V ≤ (VHI - VLO) ≤ 8.7V, ICLMP = 250µA V CURRENT-SENSE AMPLIFIER (CSA) Differential Input Voltage Range VCS+ - VCS- Common-Mode Range VCC ≤ 68V CS+ Input Bias Current ICS+ VCS+ = 0.3V, VCS- = 0V CS- Input Bias Current ICS- VCS+ = 0.3V, VCS- = 0V Unity-Gain Bandwidth 0 0.3 V 0 VCC V -250 +250 nA 400 From (CS+ to CS-) to CS 1.0 µA MHz REF OUTPUT BUFFER REF Output Voltage VREF -100µA ≤ IL ≤ +100µA 2.85 3.0 3.15 V 20 40 µs VCLMP - VLO = 4V 5 20 VCLMP - VLO = 8V 30 67 VCLMP - VLO = 4V 10 22 VCLMP - VLO = 8V 40 76 DIM DRIVER Minimal Pulse Width fDIM = 200Hz (Note 3) Source Current Sink Current mA mA GATE DRIVER DRI Voltage Range VDRI DRI UVLO Threshold VUVLO_TH DRI UVLO Threshold Hysteresis VUVLO_HYST VCC ≥ 2.5V above VDRI 5 4.0 4.2 0.3 15 V 4.4 V V _______________________________________________________________________________________ 3 MAX16816 ELECTRICAL CHARACTERISTICS (continued) MAX16816 Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming ELECTRICAL CHARACTERISTICS (continued) (VCC = VUVEN = 14V, CREG1 = 1µF, CREG2 = 1µF, CCLMP = 0.1µF, RT = 25kΩ, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical specifications are at TA = +25°C.) PARAMETER Driver Output Impedance SYMBOL CONDITIONS MIN TYP MAX ZOUT_L VDRI = 7.0V, DRV sinking 250mA 2.8 4 ZOUT_H VDRI = 7.0V, DRV sourcing 250mA 5.0 8 UNITS Ω Peak Sink Current ISK VDRI = 7.0V 2.5 A Peak Source Current ISR VDRI = 7.0V 1.4 A VCOMP - (VSNS+ -VSNS-) 0.8 V PWM, ILIM, AND HICCUP COMPARATOR PWM Comparator Offset Voltage Peak Current-Limit Comparator Trip Threshold 160 Peak Current-Limit Comparator Propagation Delay (Excluding Blanking Time) 50mV overdrive HICCUP Comparator Trip Threshold 200 245 40 235 300 mV ns 385 mV SNS+ Input Bias Current VSNS+ = 0V, VSNS- = 0V -100 -65 µA SNS- Input Bias Current VSNS+ = 0V, VSNS- = 0V -100 -65 µA BLANKING TIME Blanking Time Blanking Time Control Register is ‘00’ 150 Blanking Time Control Register is ‘01’ 125 Blanking Time Control Register is ‘10’ 100 Blanking Time Control Register is ‘11’ 75 ns ERROR AMPLIFIER FB Input Bias Current VFB = 1V EAMP Output Sink Current VFB = 1.735V, VCOMP = 1V 3 7 mA EAMP Output Source Current VFB = 0.735V, VCOMP = 1V 2 7 mA (Note 5) 0 EAMP Input Common-Mode Voltage VCOM EAMP Output Clamp Voltage Voltage Gain Unity-Gain Bandwidth -100 1.3 AV GBW +100 1.6 2.0 2.7 nA V V RCOMP = 100kΩ to AGND 80 dB RCOMP = 100kΩ to AGND, CCOMP = 100pF to AGND 0.5 MHz OSCILLATOR, OSC SYNC, CLK, AND CLKOUT SYNC Frequency Range fSW_MIN RTSYNC Oscillator Frequency SYNC High-Level Voltage VSIHL SYNC Low-Level Voltage VSILL 4 125 500 fSW_MAX RTOF bit set to ‘0’, RT = 100kΩ 106 125 143 RTOF bit set to ‘0’, RT = 25kΩ 475 500 525 2.8 _______________________________________________________________________________________ kHz kHz V 0.4 V Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming (VCC = VUVEN = 14V, CREG1 = 1µF, CREG2 = 1µF, CCLMP = 0.1µF, RT = 25kΩ, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical specifications are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX CLKOUT High Level ISINK = 0.8mA CLKOUT Low Level ISOURCE = 1.6mA 0.4 V fSW = 500kHz 500 pF 240 Hz 2000 Hz 0.4 V CLKOUT Maximum Load Capacitance CCLK_CAP 2.8 UNITS V DIM SYNC, DIM RAMP, AND DIM PWM GEN Internal RAMP Frequency fRAMP 160 External Sync Frequency Range fDIM 80 External Sync Low-Level Voltage VLTH External Sync High-Level Voltage VHTH 3.2 VDIMOS 170 DIM Comparator Offset 200 V 200 300 mV DIGITAL SOFT-START AND BINNING Soft-Start Duration tSS Digital Soft-Start Duration register is ‘000’ 4096 Digital Soft-Start Duration register is ‘001’ 2048 Digital Soft-Start Duration register is ‘010’ 1536 Digital Soft-Start Duration register is ‘011’ 1024 Digital Soft-Start Duration register is ‘100’ 768 Digital Soft-Start Duration register is ‘101’ 512 Digital Soft-Start Duration register is ‘110’ 256 Digital Soft-Start Duration register is ‘111’ Binning Range µs 0 Binning Adjustment register is ‘0000’ 100.00 Binning Adjustment register is ‘0001’ 106.67 Binning Adjustment register is ‘0010’ 113.33 Binning Adjustment register is ‘0011’ 120.00 Binning Adjustment register is ‘0100’ 126.67 Binning Adjustment register is ‘0101’ 133.33 Binning Adjustment register is ‘0110’ 140.00 Binning Adjustment register is ‘0111’ 146.67 Binning Adjustment register is ‘1000’ 153.33 Binning Adjustment register is ‘1001’ 160.00 Binning Adjustment register is ‘1010’ 166.67 mV OVERVOLTAGE COMPARATOR, LOAD OVERCURRENT COMPARATOR OVP Overvoltage Comparator Threshold VOV OVP Overvoltage Comparator Hysteresis VOV_HYST VOV rising 1.20 1.235 63.5 1.27 V mV _______________________________________________________________________________________ 5 MAX16816 ELECTRICAL CHARACTERISTICS (continued) MAX16816 Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming ELECTRICAL CHARACTERISTICS (continued) (VCC = VUVEN = 14V, CREG1 = 1µF, CREG2 = 1µF, CCLMP = 0.1µF, RT = 25kΩ, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical specifications are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS SLOPE COMPENSATION Slope Compensation Peak-toPeak Voltage Per Cycle 6 Slope Compensation register is ‘0000’, clock generated by RT 0 Slope Compensation register is ‘0001’, clock generated by RT 20 Slope Compensation register is ‘0010’, clock generated by RT 40 Slope Compensation register is ‘0011’, clock generated by RT 60 Slope Compensation register is ‘0100’, clock generated by RT 80 Slope Compensation register is ‘0101’, clock generated by RT 100 Slope Compensation register is ‘0110’, clock generated by RT 120 Slope Compensation register is ‘0111’, clock generated by RT 140 Slope Compensation register is ‘1000’, clock generated by RT 160 Slope Compensation register is ‘1001’, clock generated by RT 180 Slope Compensation register is ‘1010’, clock generated by RT 200 Slope Compensation register is ‘1011’, clock generated by RT 220 Slope Compensation register is ‘1100’, clock generated by RT 240 Slope Compensation register is ‘1101’, clock generated by RT 260 Slope Compensation register is ‘1110’, clock generated by RT 280 Slope Compensation register is ‘1111’, clock generated by RT 300 mV/ cycle _______________________________________________________________________________________ Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming (VCC = VUVEN = 14V, CREG1 = 1µF, CREG2 = 1µF, CCLMP = 0.1µF, RT = 25kΩ, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical specifications are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP Slope Compensation register is ‘0000’, external clock applied to RTSYNC 0 Slope Compensation register is ‘0001’, external clock applied to RTSYNC 2 Slope Compensation register is ‘0010’, external clock applied to RTSYNC 4 Slope Compensation register is ‘0011’, external clock applied to RTSYNC 6 Slope Compensation register is ‘0100’, external clock applied to RTSYNC 8 Slope Compensation register is ‘0101’, external clock applied to RTSYNC 10 Slope Compensation register is ‘0110’, external clock applied to RTSYNC 12 Slope Compensation register is ‘0111’, external clock applied to RTSYNC 14 Slope Compensation register is ‘1000’, external clock applied to RTSYNC 16 Slope Compensation register is ‘1001’, external clock applied to RTSYNC 18 Slope Compensation register is ‘1010’, external clock applied to RTSYNC 20 Slope Compensation register is ‘1011’, external clock applied to RTSYNC 22 Slope Compensation register is ‘1100’, external clock applied to RTSYNC 24 Slope Compensation register is ‘1101’, external clock applied to RTSYNC 26 Slope Compensation register is ‘1110’, external clock applied to RTSYNC 28 Slope Compensation register is ‘1111’, external clock applied to RTSYNC 30 Slope Compensation MAX UNITS mV/µs _______________________________________________________________________________________ 7 MAX16816 ELECTRICAL CHARACTERISTICS (continued) MAX16816 Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming ELECTRICAL CHARACTERISTICS (continued) (VCC = VUVEN = 14V, CREG1 = 1µF, CREG2 = 1µF, CCLMP = 0.1µF, RT = 25kΩ, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical specifications are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS +1 µA 1.8 mA 0.4 V 0.4 V FAULT I/O FAULT Leakage Current 5.5V < VFAULT < 76V FAULT Input Low Current VFAULT = 0V FAULT Pulldown Current VFAULT = 2V FAULT Pulldown Input Logic-Low -1 500 0.7 1.2 VIL FAULT Output Logic-High Sourcing 10µA FAULT Output Logic-Low Sinking 10µA Programming Slot at Power-Up VUVEN > 1.244V and VCC > 5.9V (Note 4) µA 2.8 6.4 V 8.0 ms THERMAL SHUTDOWN Thermal Shutdown Temperature Thermal Shutdown Hysteresis TJ_SHDN +165 o C ΔTJ_SHDN 20 o C EEPROM Data Retention EEPROM Write Time tDR tWRA Endurance TA = +125°C (Note 5) 10 years (Note 5) 14 TA = +85°C, read and write (Note 5) 50k ms cycles ELECTRICAL CHARACTERISTICS – 1-Wire® System (CREG1 = 1µF, CREG2 = 1µF, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical specifications are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS I/O GENERAL DATA 1-Wire Time Slot Duration tSLOT Recovery Time tREC (Note 6) 65 µs 5 µs I/O, 1-Wire RESET, PRESENCE DETECT CYCLE Reset Low Time tRSTL 480 640 µs Presence Detect Sample Time tMSP 65 75 µs Write-0 Low Time tW0L 60 Write-1 Low Time tW1L 5 15 µs tRL 5 10 µs tMSR 12 15 µs I/O, 1-Wire WRITE µs I/O, 1-Wire READ Read Low Time Read Sample Time 1-Wire is a registered trademark of Dallas Semiconductor Corp., a wholly owned subsidiary of Maxim Integrated Products, Inc. 8 _______________________________________________________________________________________ Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming Note 1: Dropout voltage is defined as the input to output differential voltage at which the output voltage drops 100mV below its nominal value measured at output. Note 2: VCLMP_TH determines the voltage necessary to operate the current-sense amplifier. The DIM driver requires 2.5V for (VCLMP - VLO) to drive a FET. VHI is typically one diode drop above VCLMP. A large capacitor connected to VCLMP slows the response of the LED current-sense circuitry, resulting in current overshoot. To ensure proper operation, connect a 0.1µF capacitor from CLMP to LO. Note 3: Minimum pulse width required to guarantee proper dimming operation. Note 4: FAULT multiplexes a programming interface and fault indication functionality. At power-up initialization, an internal timer enables FAULT and two programming passcodes must be entered within the programming slot to enter programming mode. If the programming passcodes are not received correctly within the programming slot, FAULT goes back towards fault indication. Cycling power to the device is required to re-attempt entry into programming mode. Note 5: Not production tested. Guaranteed by design. Note 6: Recovery time is the time required for FAULT to be pulled high by the internal 10kΩ resistor. Typical Operating Characteristics (VCC = VUVEN = 14V, CREG1 = 1µF, CREG2 = 10µF, CCLMP = 0.1µF, RCS = 0.1Ω, Binning adjustment register is ‘0000’, TA = +25°C, unless otherwise noted.) 25 3.8 22 LED CURRENT (mA) 23 3.4 3.2 21 3.0 20 DGT AND DRV NOT SWITCHING 2.6 18 -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) RCS = 0.2Ω 450 400 350 RCS = 0.3Ω 300 2.8 19 550 500 3.6 ICC (mA) ISHDN_VCC (μA) 24 600 MAX16816 toc02 4.0 MAX16816 toc01 26 OUTPUT CURRENT vs. TEMPERATURE OPERATING CURRENT vs. TEMPERATURE MAX16816 toc03 SHUTDOWN CURRENT vs. TEMPERATURE 250 200 -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) _______________________________________________________________________________________ 9 MAX16816 ELECTRICAL CHARACTERISTICS Typical Operating Characteristics (continued) (VCC = VUVEN = 14V, CREG1 = 1µF, CREG2 = 10µF, CCLMP = 0.1µF, RCS = 0.1Ω, Binning adjustment register is ‘0000’, TA = +25°C, unless otherwise noted.) OUTPUT CURRENT vs. SUPPLY VOLTAGE 1.4 200 150 100 50 0 800 0.8 0.6 700 600 500 400 300 0.4 200 0.2 100 0 0 0 1 2 3 4 5 6 7 0 9 8 RCS = 0.2Ω 1 2 3 4 5 6 7 8 BIN (DIGITAL CODE) REG2 OUTPUT VOLTAGE vs. TEMPERATURE REG2 OUTPUT VOLTAGE vs. SUPPLY VOLTAGE REG2 OUTPUT VOLTAGE vs. REG2 CONTROL REGISTER REG2 CONTROL REGISTER = '0000' REG2 CONTROL REGISTER = '1111', VCC = 20V 16 14 12 10 8 6 4 REG2 CONTROL REGISTER = '0000' 2 IREG2 = 20mA 0 8 12 11 10 9 8 7 6 5 4 IREG2 = 20mA 0 20 40 60 80 100 120 140 16 15 14 13 16 24 32 40 48 56 64 72 80 IREG2 = 20mA 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 TEMPERATURE (°C) VCC (V) DRPS (DIGITAL CODE) REG1 OUTPUT VOLTAGE vs. TEMPERATURE REG1 OUTPUT VOLTAGE vs. SUPPLY VOLTAGE CLMP OUTPUT VOLTAGE vs. TEMPERATURE 5.2 5.1 5.0 4.9 4.8 4 3 2 1 4.7 IREG1 = 2mA 4.6 -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) MAX16816 toc12 5 8.3 8.2 CLMP OUTPUT VOLTAGE (V) 5.3 6 MAX16816 toc11 MAX16816 toc10 5.4 9 MAX16816 toc09 18 REG2 OUTPUT VOLTAGE (V) REG2 CONTROL REGISTER = '1111', VCC = 20V REG2 OUTPUT VOLTAGE (V) BIN (DIGITAL CODE) MAX16816 toc08 VCC (V) -60 -40 -20 0 10 1.0 16 24 32 40 48 56 64 72 80 REG1 OUTPUT VOLTAGE (V) 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 8 MAX16816 toc07 REG2 OUTPUT VOLTAGE (V) 0 1.2 MAX16816 toc06 1.6 OUTPUT CURRENT (mA) 250 900 MAX16816 toc05 1.8 LED CURRENT (A) LED CURRENT (mA) 300 OUTPUT CURRENT vs. BINNING CODES OUTPUT CURRENT vs. BINNING CODES MAX16816 toc04 350 REG1 OUTPUT VOLTAGE (V) MAX16816 Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming 8.1 8.0 7.9 7.8 7.7 7.6 IREG1 = 2mA 0 VHI - VLO = 9V CLMP VOLTAGE = VCLMP - VLO 7.5 0 10 20 30 40 VCC (V) 50 60 70 80 -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) ______________________________________________________________________________________ Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming REF VOLTAGE (V) 3.06 3.04 3.02 3.00 3.015 3.010 3.005 2.98 IREF = 100μA 3.000 2.96 -10 15 40 65 75 125 175 225 -35 -10 15 40 65 90 115 140 IREF (μA) TEMPERATURE (°C) RT RESISTANCE vs. PWM FREQUENCY 200Hz DIMMING OPERATION LED CURRENT DUTY CYCLE vs. DIM VOLTAGE MAX16816 toc17 MAX16816 toc16 500 450 100 90 400 0A 10% DIMMING 1A/div 0A 50% DIMMING 1A/div 0A 90% DIMMING 1A/div 350 300 250 200 150 80 70 60 50 40 30 20 10 0 0.015 0.025 0.045 0.035 0 2ms/div 1 1/RT RESISTANCE (kΩ-1) 3 2 DIM VOLTAGE (V) DRIVER DRV RISE TIME vs. DRI VOLTAGE DRIVER DRI FALL TIME vs. DRI VOLTAGE 60 40 35 DRV FALL TIME (ns) 50 40 30 20 MAX16816 toc20 45 MAX16816 toc19 70 DRV RISE TIME (ns) 100 0.005 -60 TEMPERATURE (°C) 550 PWM FREQUENCY (kHz) -225 -175 -125 -75 -25 25 115 140 90 RT = 100kΩ MAX16816 toc18 -35 LED CURRENT DUTY CYCLE (%) -60 135 134 133 132 131 130 129 128 127 126 125 124 123 122 121 120 MAX16816 toc15 3.020 3.08 PWM FREQUENCY (kHz) 3.10 MAX16816 toc14 3.025 MAX16816 toc13 3.12 REF VOLTAGE (V) PWM OSCILLATION FREQUENCY vs. TEMPERATURE REF VOLTAGE vs. SINK CURRENT REF VOLTAGE vs. TEMPERATURE 30 25 20 15 10 10 5nF CAPACITOR CONNECTED FROM DRV TO AGND 5nF CAPACITOR CONNECTED FROM DRV TO AGND 5 0 0 5 7 9 11 DRI VOLTAGE (V) 13 15 5 7 9 11 13 15 DRI VOLTAGE (V) ______________________________________________________________________________________ 11 MAX16816 Typical Operating Characteristics (continued) (VCC = VUVEN = 14V, CREG1 = 1µF, CREG2 = 10µF, CCLMP = 0.1µF, RCS = 0.1Ω, Binning adjustment register is ‘0000’, TA = +25°C, unless otherwise noted.) Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming MAX16816 Pin Description PIN NAME 1, 24 N.C. FUNCTION No Connection. Not internally connected. 2 UVEN Undervoltage Lockout (UVLO) Threshold/Enable Input. UVEN is a dual-function adjustable UVLO threshold input with an enable feature. Connect UVEN to VCC through a resistive voltage-divider to program the UVLO threshold. Connect UVEN directly to VCC to use the 5.9V (max) default UVLO threshold. Apply a voltage greater than 1.244V to UVEN to enable the device. 3 REG1 5V Regulator Output. REG1 is an internal low-dropout voltage regulator that generates a 5V (VCC > 6V) output voltage and supplies power to internal circuitry. Bypass REG1 to AGND through a 1µF ceramic capacitor. 4 AGND Analog Ground. Use proper single-point ground design and decoupling to avoid ground impedance loop errors. 5 REF Accurate 3V Buffered Reference Output. Connect REF to DIM through a resistive voltage-divider to apply a DC voltage for analog-controlled dimming functionality. Leave REF unconnected if unused. 6 DIM Dimming Control Input. Connect DIM to an external PWM signal for PWM dimming. For analog-controlled dimming, connect DIM to REF through a resistive voltage-divider. The dimming frequency is 200Hz under these conditions. Connect DIM to AGND to turn off the LEDs. 7 RTSYNC Sync Input/Output. The internal PWM clock is selectable through the RTOF EEPROM bit. Connect an external resistor to RTSYNC and set the RTOF register to ‘0’ to select a clock frequency between 125kHz and 500kHz. Set RTOF register to ‘0’ and connect RTSYNC to an external clock to synchronize the device with external clock. Set RTOF register to ‘1’ to use the fixed 125kHz oscillator. Under these conditions, RTSYNC is powered off and may be left in any state. See the Oscillator, Clock, and Synchronization section. 8 CLKOUT Clock Output. CLKOUT buffers the oscillator/clock. Connect CLKOUT to the SYNC input of another device to operate the MAX16816 in a multichannel configuration. CLKOUT is a logic output. 9, 10, 11 I.C. 12 COMP Error-Amplifier Output. Connect the compensation network from COMP to FB for stable closed-loop control. Use low-leakage ceramic capacitors in the feedback network. 13 CS Current-Sense Voltage Output. CS outputs a voltage proportional to the current sensed through the currentsense amplifier. Connect CS through a passive network to FB as dictated by the chosen compensation scheme. 14 FB Error-Amplifier Inverting Input 15 OV Overvoltage Protection Input. Connect OV to HI through a resistive voltage-divider to set the overvoltage limit for the load. When the voltage at OV exceeds the 1.235V (typ) threshold, an overvoltage fault is generated and the switching MOSFET turns off. The MOSFET is turned on again when the voltage at OV drops below 1.17V (typ). 16, 17 SGND 18 DRV Gate-Driver Output. Connect DRV through a series resistor to the gate of an external n-channel MOSFET to reduce EMI. DRV can sink 1A or source 0.5A. 19 DRI Gate-Driver Supply Input. Connect DRI to REG2 to power the primary switching MOSFET driver. 20 SNS+ 12 Internally Connected. Must be connected to AGND. Switching Ground. SGND is the ground for non-analog and high-current gate-driver circuitry. Positive Peak Current-Sense Input. Connect SNS+ to the positive side of the switch current-sense resistor, RSENSE. ______________________________________________________________________________________ Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming PIN NAME FUNCTION 21 SNS- 22 QGND 23 DGT Dimming Gate-Driver Output. Connect DGT to the gate of an external n-channel MOSFET for dimming. DGT is powered by the internal regulator, CLAMP, and is referenced to LO. 25 LO Low-Voltage Input. LO is the return point for the LED current. When using the MAX16816 in a buck-boost configuration, connect LO to VCC. When using the device in a boost configuration only, connect LO to AGND. Connect LO to the junction of the inductor and LED current-sense resistor, RCS, when using a buck configuration. 26 CS+ Noninverting Current-Sense Amplifier Input. Connect CS+ to the positive side of an external sense resistor, RCS, connected in series with the load (LEDs). 27 CS- Inverting Current-Sense Amplifier Input. Connect CS- to the negative side of an external sense resistor, RCS, connected in series with the load (LEDs). Negative Peak Current-Sense Input. Connect SNS- to the negative side of the switch current-sense resistor, RSENSE. Analog Ground. Ensure a low-impedance connection between QGND and AGND. Internal CLAMP Regulator Bypass. CLAMP supplies an 8V (typ) output when VHI ≥ 9V. If VHI is lower than 9V, VCLMP is one diode drop below VHI. The CLAMP regulator powers the current-sense amplifier and provides the high reference for the dimming driver. VCLMP must be at least 2.5V higher than VLO to enable the current-sense amplifier and dimming MOSFET driver. Bypass CLMP to LO with a 0.1µF ceramic capacitor. 28 CLMP 29 HI 30 REG2 31 VCC 32 FAULT FAULT Input/Output. FAULT is a bidirectional high-voltage logic input/output. FAULT multiplexes a 1-Wire programming interface with a fault indicator. FAULT is internally pulled up to 5V through a 10kΩ resistor and a 1.8mA (max) current pulldown to ground. EP EP Exposed Pad. Connect EP to AGND. EP also functions as a heatsink to maximize thermal dissipation. Do not use as the main ground connection. High-Voltage Input. HI is referred to LO. HI supplies power to the current-sense amplifier and dimming MOSFET gate driver through the CLMP regulator. Internal Regulator Output. REG2 is an internal voltage regulator that generates EEPROM-programmable (5V to 15V) output and supplies power to internal circuitry. Connect REG2 to DRI to power the switching MOSFET driver during normal operation. Bypass REG2 to AGND with a 10µF ceramic capacitor. Supply Voltage Input ______________________________________________________________________________________ 13 MAX16816 Pin Description (continued) Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming MAX16816 Functional Diagram CLMP VCC CS- CS+ HI + - LO CSA UVLO AND EN 15V REG2 5V REG1 CLAMP VLO VCLMP UVEN REG2 D-I REG2 DRIVER THERMAL SHUTDOWN RLS VCLMP QGND SLOPE REG1 UGB SLOPE COMP DDR DGT D-I VBUF 3.0V + REF VLO + CMP 1.3 x V SS - CS 1-Wire INTERFACE RTSYNC OSC OSC FAULT OC CLKOUT DRI POR EN VOV - DRV SGND + + ILIM - 200mV + DIM COMP AGND DRIVER OV OVP OV CONTROL BLOCK - 200mV 200Hz + SNS+ SNS- + HIC 300mV - - D-I BLANKING BLANKING TIME MAX16816 PWM SLOPE 0.926V OS TRIM REGISTERS BLANKING SLOPE COMP BINNING REG2 DRIVER SOFT-START RTOSCSEL + SS VSS X1 EAMP D-I D-I D-I SOFT-START BINNING D-I 14 - 800mV + INDICATES A USER-PROGRAMMABLE EEPROM FEATURE ______________________________________________________________________________________ COMP FB Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming The MAX16816 is a current-mode PWM LED driver for use in driving HB LEDs. An output current accuracy of 5% is achievable using two current regulation loops: one current regulation loop controls the external switching MOSFET peak current through a sense resistor, RSENSE, from SNS+ to SNS- while the other current regulation loop controls the average LED string current through the sense resistor, R CS , in series with the LEDs. The wide operating supply range of 5.9V/5.4V (ON/OFF) to 76V makes the MAX16816 ideal in automotive applications. The MAX16816 provides LED binning through one programmable on-chip nonvolatile EEPROM. The LED current can be scaled up to a factor of 1.6. This feature is used to offset factory LED luminance variations and allows the system to achieve overall luminance accuracy. A programmable undervoltage lockout (UVEN) ensures predictable operation during brownout conditions. The UVEN input circuitry monitors the supply voltage, VCC, and turns the driver off when V CC drops below the UVLO threshold. Connect UVEN to VCC to use the 5.7V (typ) default UVLO threshold. The MAX16816 includes a cycle-by-cycle current limit that turns off the gate drive to the external switching MOSFET (QS) during an overcurrent condition and a programmable oscillator that simplifies and optimizes the design of external magnetics. The MAX16816 is capable of synchronizing to an external clock or operating in a stand-alone mode. A single resistor, RT, can be used to adjust the switching frequency from 125kHz to 500kHz for stand-alone operation. To synchronize the device with an external clock, apply a clock signal directly to the RTSYNC input. A buffered clock output, CLKOUT, is available to configure the MAX16816 for multichannel applications. The external RT oscillator can be disabled by setting EEPROM register RTOF to ‘1’. The MAX16816 provides wide contrast pulsed dimming (up to 1000:1) utilizing a separate dimming input. Apply either a DC level voltage or low-frequency PWM signal to the dimming input. DC level input results in a 200Hz fixed dimming frequency. The MAX16816 provides configurable on-chip nonvolatile EEPROM features including a programmable soft-start, load current, external MOSFET gate-driver supply voltage, blanking time, and slope compensation. Protection features include peak current limiting, HICCUP mode current limiting, output overvoltage protection, short-circuit protection, and thermal shutdown. The HICCUP current-limit circuitry reduces the power deliv- ered to the load during severe fault conditions. A nonlatching overvoltage protection limits the voltage on the external switching MOSFET (QS) under open-circuit conditions in the LED string. During continuous operation at high input voltages, the power dissipation of the MAX16816 could exceed the maximum rating and the internal thermal shutdown circuitry safely turns off the MAX16816 when the device junction temperature exceeds +165°C. When the junction temperature drops below the hysteresis temperature, the MAX16816 automatically reinitiates startup. Undervoltage Lockout/Enable (UVEN) The MAX16816 features a dual-purpose adjustable undervoltage lockout input and enable function (UVEN). Connect UVEN to VCC through a resistive voltage-divider to set the undervoltage lockout (UVLO) threshold. The device is enabled when the voltage at UVEN exceeds the 1.244V (typ) threshold. Drive UVEN to ground to disable the output. Setting the UVLO Threshold Connect UVEN directly to VCC to select the default 5.7V (typ) UVLO threshold. Connect UVEN to VCC through a resistive voltage-divider to select a UVLO threshold (Figure 1). Select the desired UVLO threshold voltage, VUVLO, and calculate resistor values using the following equation: ⎛ ⎞ VUVEN RUV1 = RUV2 x ⎜ ⎟ ⎝ VUVLO - VUVEN ⎠ where RUV1 + RUV2 ≤ 270kΩ. VUVEN is the 1.244V (typ) UVEN threshold voltage. VIN RUV2 VCC UVEN MAX16816 CUVEN RUV1 QGND Figure 1. Setting the UVLO Threshold ______________________________________________________________________________________ 15 MAX16816 Detailed Description MAX16816 Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming The capacitor CUVEN is required to prevent chattering at the UVLO threshold due to line impedance drops during power-up and dimming. If the undervoltage setting is very close to the required minimum operating voltage, there can be large jumps in the voltage at VCC during dimming, which may cause the MAX16816 to turn on and off when the dimming signal transitions from low to high. The capacitor CUVEN should be large enough to limit the ripple on UVEN to less than the 100mV (min) UVEN hysteresis so that the device does not turn off under these circumstances. Soft-Start The MAX16816 features a digitally programmable softstart delay that allows the load current to ramp up in a controlled manner, minimizing output overshoot. Softstart begins once the device is enabled and V CC exceeds the UVLO threshold. Soft-start circuitry slowly increases the internal soft-start voltage, VSS, resulting in a controlled rise of the load current. Signals applied to DIM are ignored until the soft-start duration is complete and a successive delay of 200µs has elapsed. Use the Digital Soft-Start Duration register in the EEPROM to select a soft-start duration from 0 (no delay) to 4.096ms. See the EEPROM and Programming section for more information on using the Digital Soft-Start Duration register. Regulators (REG1, REG2, CLAMP) The MAX16816 includes a fixed 5V voltage regulator, REG1; an EEPROM-adjustable regulator, REG2; and an internal 8V regulator, CLAMP. REG1 and REG2 power up when VCC exceeds the UVLO threshold. REG1 supplies power to internal circuitry and remains on during PWM dimming. REG1 is capable of driving external loads up to 2mA. Use the REG2 Control Register in the EEPROM to select an output voltage from 5V to 15V for REG2. Connect REG2 to DRI to generate the supply voltage for the primary switching MOSFET driver, DRV. REG2 is capable of delivering up to 20mA of current. See the EEPROM and Programming section for more information on configuring the REG2 output voltage. CLAMP is powered by HI and supplies power to the current-sense amplifier (CSA). CSA is enabled when V CLMP goes 2.5V above V LO and is disabled when (VCLMP - VLO) falls below 2.28V. The CLAMP regulator also provides power to the dimming MOSFET control circuitry. CLMP is the output of the CLAMP regulator. Do not use CLMP to power external circuitry. Bypass CLMP to LO with a 0.1µF ceramic capacitor. A larger capacitor will result in overshoot of the load current. 16 Reference Voltage Output (REF) The MAX16816 includes a 5% accurate, 3V (typ) buffered reference output, REF. REF is a push-pull output capable of sourcing/sinking up to 200µA of current and can drive a maximum load capacitance of 100pF. Connect REF to DIM through a resistive voltage-divider to supply an analog signal for dimming. See the Dimming Input (DIM) section for more information. Dimming MOSFET Driver (DDR) The MAX16816 requires an external n-channel MOSFET for PWM dimming. Connect the MOSFET to the output of the DDR dimming driver, DGT, for normal operation. VDGT swings between VLO and VCLMP. The DDR dimming driver is capable of sinking or sourcing up to 20mA of current. The average current required to drive the dimming MOSFET (I DRIVE_DIM) depends on the MOSFET’s total gate charge (QG_DIM) and the dimming frequency of the converter, fDIM. Use the following equation to calculate the supply current for the n-channel dimming FET driver. IDRIVE_DIM = QG_DIM x fDIM n-Channel MOSFET Switch Driver (DRV) The MAX16816 drives an external n-channel MOSFET for switching. Use an external supply or connect REG2 to DRI to power the MOSFET driver. The driver output, VDRV, swings between ground and VDRI. Ensure that VDRI remains below the absolute maximum VGS rating of the external MOSFET. DRV is capable of sinking 2A or sourcing 1.4A of peak current, allowing the MAX16816 to switch MOSFETs in high-power applications. The average current sourced to drive the external MOSFET depends on the total gate charge (QG) and operating frequency of the converter, fSW. The power dissipation in the MAX16816 is a function of the average output drive current (IDRIVE). Use the following equations to calculate the power dissipation in the gate-driver section of the MAX16816 due to IDRIVE: IDRIVE = QG x fSW PD = IDRIVE x VDRI where VDRI is the supply voltage to the gate driver. Dimming Input (DIM) The dimming input, DIM, functions with either analog or PWM control signals. Once the internal pulse detector detects three successive edges of a PWM signal with a frequency between 80Hz and 2kHz, the MAX16816 synchronizes to the external signal and pulse-width modulates the LED current at the external DIM input frequency with the same duty cycle as the DIM input. If ______________________________________________________________________________________ Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming VDIM = (D x 2.6) + 0.2V where VDIM is the voltage applied to DIM in volts. Connect DIM to REF through a resistive voltage-divider to apply a DC DIM control signal (Figure 2). Use the required dimming input voltage, V DIM , calculated above and select appropriate resistor values using the following equation: R4 = R3 x VDIM / (VREF - VDIM) where V REF is the 3V reference output voltage and 15kΩ ≤ R3 + R4 ≤ 150kΩ. A minimum 20µs pulse width is necessary for proper operation during dimming. Oscillator, Clock, and Synchronization The MAX16816 is capable of stand-alone operation, of synchronizing to an external clock, and of driving external devices in SYNC mode. For stand-alone operation, set the EEPROM Oscillator Enable/Disable (RTOF) bit to ‘1’ to use the fixed internal 125kHz oscillator or set RTOF to ‘0’ and program the switching frequency by connecting a single external resistor, R T , between RTSYNC and ground. Select a switching frequency, fSW, between 125kHz and 500kHz and calculate RT using the following formula: RT = 500kHz × 25kΩ fSW where the switching frequency is in kHz and RT is in kΩ. To synchronize the MAX16816 with an external clock signal ranging from 125kHz to 500kHz, set the RTOF bit to ‘0’ and connect the clock signal to the RTSYNC input. The MAX16816 synchronizes to the clock signal after the detection of 5 successive clock edges at RTSYNC. A buffered clock output, CLKOUT, can drive the RTSYNC input of an external PWM controller for multichannel applications. CLKOUT can drive capacitive loads up to 500pF. If the PWM switching frequency is set to 125kHz, the RTSYNC oscillator can be temporarily disabled by setting the EEPROM RTOF bit to ‘1’. In this case, the internal 125kHz frequency-fixed oscillator drives the PWM. See the EEPROM and Programming section for more information on setting the Oscillator Enable/Disable bit in the EEPROM. Multichannel Configuration The MAX16816 is capable of multichannel operation and is configurable as a master or slave in a MasterSlave configuration, or in a Peer-to-Peer configuration. Connect CLKOUT to the SYNC input of an external device to use the MAX16816 as a master clock signal. Connect an external clock signal to RTSYNC to configure the MAX16816 as a slave. To setup two MAX16816 devices in a daisy-chain configuration, drive the RTSYNC input of one MAX16816 with the CLKOUT buffer of another (Figure 3). ILIM and HICCUP Comparator RSENSE sets the peak current through the inductor for switching. The differential voltage across RSENSE is compared to the 200mV voltage-trip limit of the currentlimit comparator, ILIM. Set the current limit 20% higher than the peak switch current at the rated output power and minimum voltage. Use the following equation to calculate RSENSE: RSENSE = VSENSE / (1.2 x IPEAK) REF R3 MASTER/PEER SLAVE/PEER MAX16816 MAX16816 MAX16816 DIM AGND RTSYNC CLKOUT RTSYNC CLKOUT R4 RT Figure 2. Creating DIM Input Signal from REF Figure 3. Master-Slave/Peer-Peer Clock Configuration ______________________________________________________________________________________ 17 MAX16816 an analog control signal is applied to DIM, the MAX16816 compares the DC input to an internally generated 200Hz ramp to pulse-width modulate the LED current (fDIM = 200Hz). The output current duty cycle is linearly adjustable from 0 to 100% (0.2V < VDIM < 2.8V). Use the following formula to calculate voltage, VDIM, necessary for a given output current duty cycle, D: MAX16816 Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming where VSENSE is the 200mV maximum differential voltage between SNS+ and SNS- and IPEAK is the peak inductor current at full load and minimum input voltage. When the voltage drop across RSENSE exceeds the ILIM threshold, the MOSFET driver (DRV) terminates the on-cycle and turns the switch off, reducing the current through the inductor. The FET is turned back on at the beginning of the next switching cycle. When the voltage across RSENSE exceeds the 300mV (typ) HICCUP threshold, the HIC comparator terminates the on-cycle of the device, turning the switching MOSFET off. Following a startup delay of 8ms (typ), the MAX16816 reinitiates soft-start. The device will continue to operate in HICCUP mode until the overcurrent condition is removed. A programmable built-in leading-edge blanking circuit of the current-sense signal prevents these comparators from prematurely terminating the on-cycle of the external switching MOSFET (Q S). Select a blanking time from 75ns to 150ns by configuring the Blanking Time register in the EEPROM. In some cases, the maximum blanking time may not be adequate and an additional RC filter may be required to prevent spurious turn-off. Load Current Sense The load sense resistor, R CS , monitors the current through the LEDs. The internal floating current-sense amplifier, CSA, measures the differential voltage across RCS, and generates a voltage proportional to the load current through R CS at CS. This voltage on CS is referred to AGND. The closed-loop regulates the load current to a value, ILED, given by the following equation: ILED = VSS / RCS where VSS is the binning adjustment voltage. Set the value of VSS in the Binning Adjustment register in the EEPROM between 100mV and 166mV. See the EEPROM and Programming section for more information on adjusting the binning voltage. Slope Compensation The amount of slope compensation required is largely dependent on the down-slope of the inductor current when the switching MOSFET, QS, is off. The inductor down-slope depends on the input-to-output voltage differential of the converter, the inductor value, and the switching frequency. For stability, the compensation slope should be equal to or greater than half of the inductor current down-slope multiplied by the currentsense resistance (RSENSE). 18 See the EEPROM and Programming section for more information on the ESLP register. Internal Voltage-Error Amplifier (EAMP) The MAX16816 includes a built-in voltage amplifier, with three-state output, which can be used to close the feedback loop. The buffered output current-sense signal appears at CS, which is connected to the inverting input, FB, of the error amplifier through resistor R1. The noninverting input is connected to an internally trimmed current reference. The output of the error amplifier is controlled by the signal applied to DIM. When DIM is high, the output of the amplifier is connected to COMP. The amplifier output is open when DIM is low. This enables the integrating capacitor to hold the charge when the DIM signal has turned off the gate drive. When DIM is high again, the voltage on the compensation capacitors, C1 and C2, forces the converter into steady state almost instantaneously. PWM Dimming PWM dimming is achieved by driving DIM with either a PWM signal or a DC signal. The PWM signal is connected internally to the error amplifier, the dimming MOSFET gate driver, and the switching MOSFET gate driver. When the DIM signal is high, the dimming MOSFET and the switching MOSFET drivers are enabled and the output of the voltage-error amplifier is connected to the external compensation network. Also, the buffered current-sense signal is connected to CS. Preventing discharge of the compensation capacitor when the DIM signal is low allows the control loop to return the LED current to its original value almost instantaneously. When the DIM signal goes low, the output of the error amplifier is disconnected from the compensation network and the compensation capacitors, C1 and C2, voltage is preserved. Choose low-leakage capacitors for C1 and C2. The drivers for the external dimming and switching MOSFETs are disabled, and the converter stops switching. The inductor energy is now transferred to the output capacitors. When the DIM signal goes high and the gate drivers are enabled, the additional voltage on the output capacitor may cause a current spike on the LED string. A larger output capacitor will result in a smaller current spike. If the overcurrent spike exceeds 30% of the programmed LED current, the dimming is turned off and the MAX16816 reinitiates soft-start. ______________________________________________________________________________________ Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming Once the programming window has passed, the EEPROM is no longer accessible without cycling power to the device. Under these conditions, FAULT will go low only when a fault (overvoltage, overcurrent, or HICCUP mode) occurs or when the supply voltage drops below the UVLO threshold. EEPROM and Programming Nonvolatile EEPROM is available to configure the MAX16816 through a 1-Wire serial interface. Registers are located in a linear address space as shown in Table 2. All other EEPROM locations are reserved. Configure the six control registers to adjust parameters including the REG2 voltage, soft-start durations, blanking time, LED load current (binning), slope compensation, and to enable/disable the RTOF oscillator. See the 1-Wire Interface section for more information about 1-Wire programming. Table 1. Programming Mode Entry Codes PROGRAMMING MODE ENTRY CODE D7 D6 D5 D4 D3 D2 D1 D0 HEX CODE PASS_CODE_1 0 0 1 0 1 0 0 1 29h PASS_CODE_2 0 0 0 0 1 0 0 1 09h Table 2. EEPROM Memory Map EEPROM ADDRESS RANGE NO. OF BITS TYPE Binning Adjustment (BIN) 24h–27h 4 R/W Adjusts the LED current. REG2 Control (DRPS) 28h–2Bh 4 R/W Sets the output voltage for REG2. Connect REG2 to DRI to supply the high-side voltage for the gate driver, DRV. Blanking Time Adjustment (BLNK) 32h–33h 2 R/W Adjusts the blanking time for debouncing. Digital Soft-Start Duration (SS) 34h–36h 2 R/W Adjusts the soft-start duration to allow the load current to ramp up in a controlled manner, minimizing output overshoot. 37h 1 R/W Enables/disables the internal oscillator for stand-alone operation or to synchronize with an external clock. 38h–3Bh 4 R/W Adjusts the slope compensation for stability. REGISTER Internal Oscillator Enable/Disable (RTOF) Slope Compensation (ESLP) DESCRIPTION ______________________________________________________________________________________ 19 MAX16816 FAULT 1-Wire Interface The MAX16816 features a FAULT output multiplexed with a 1-Wire programming interface. Once the voltage at UVEN exceeds the UVLO threshold, the device is enabled and FAULT will pulse low once, indicating the beginning of the programming window. Two programming mode entry codes must be entered within 8ms after the pulse to enter programming mode (see Table 1). The MAX16816 will register the second entry code only after the first code has been received. Once the MAX16816 successfully enters programming mode, the data and clock for the 1-Wire interface are supplied through FAULT. MAX16816 Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming Binning Adjustment Register (BIN) The MAX16816 uses a feedback loop to control the load current. The differential voltage across the currentsense resistor, R CS , is compared with an internal adjustable reference to regulate the LED current. The voltage across the sense resistor is measured differentially to achieve high immunity to common-mode noise. The MAX16816 includes a factory-set regulation voltage of 133mV ±3% across RCS. Adjust the differential regulation voltage by programming the binning adjustment register (see Table 3). The reference voltage level may not necessarily be equal to the regulation voltage. There are offsets involved that are trimmed at the factory. Read the default register code and step up the code by one to increase the regulation voltage by 6.66mV. Step down the code by one to reduce the regulation voltage by 6.66mV. REG2 Control Register (DRPS) REG2 is EEPROM configurable to supply a voltage ranging from 5V to 15V and is capable of sourcing up to 20mA. Connect REG2 to the primary switching MOSFET gate-driver supply input, DRI, for normal operation. Table 3. Binning Adjustment Register REFERENCE VOLTAGE LEVEL (mV) 27h 26h 25h 24h 100.00 0 0 0 0 106.67 0 0 0 1 113.33 0 0 1 0 120.00 0 0 1 1 126.67 0 1 0 0 133.33 0 1 0 1 140.00 0 1 1 0 146.67 0 1 1 1 153.33 1 0 0 0 160.00 1 0 0 1 Blanking Time Adjustment Register (BLNK) The MAX16816 features a programmable blanking time to mask out the current-sense signal for a short duration to avoid the ILIM and HICCUP comparators from prematurely terminating the on-cycle of the switching MOSFET. This blanking time allows for higher input current during startup without triggering a fault condition. The blanking time is adjustable in the range of 150ns to 75ns by configuring the EEPROM. See Table 5. Table 4. REG2 Control Register REG2 OUTPUT VOLTAGE (V) 2Bh 2Ah 29h 28h 5.000 0 0 0 0 5.667 0 0 0 1 EEPROM ADDRESS 6.333 0 0 1 0 7.000* 0 0 1 1 7.667 0 1 0 0 8.333 0 1 0 1 9.000 0 1 1 0 9.667 0 1 1 1 10.333 1 0 0 0 11.000 1 0 0 1 11.667 1 0 1 0 12.333 1 0 1 1 13.000 1 1 0 0 13.667 1 1 0 1 14.333 1 1 1 0 15.000 1 1 1 1 *Factory default Table 5. Blanking Time 166.67 1 0 1 0 173.33* 1 0 1 1 BLANKING TIME (ns) 33h 32h 180.00* 1 1 0 0 150* 0 0 186.67* 1 1 0 1 125 0 1 193.33* 1 1 1 0 100 200.00* 1 1 1 1 *Not recommended 20 EEPROM ADDRESS Adjust REG2 by programming the REG2 Control Register. See Table 4. 75 *Factory default EEPROM ADDRESS 1 0 1 1 ______________________________________________________________________________________ Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming Oscillator Enable/Disable Register (RTOF) The MAX16816 features a programmable accurate RTSYNC oscillator and resistor synchronized to an external clock. Set the EEPROM bit RTOF to ‘1’ to disable the external sync mode, and the RTSYNC oscillator, and to use the fixed internal frequency of 125kHz as the switching frequency. Set RTOF to ‘0’ to synchronize with an external oscillator or to program the external oscillator frequency with an external resistor, RT. See Table 7. Slope Compensation Register (ESLP) The MAX16816 uses an internally generated ramp to stabilize the current loop when operating at duty cycles above 50%. Set the compensating slope by adjusting the peak ramp voltage through the on-chip EEPROM. See Tables 8 and 9. EEPROM ADDRESS DURATION (µs) 36h 35h 34h 4096* 0 0 0 2048 0 0 1 1860 0 1 0 1024 0 1 1 768 1 0 0 512 1 0 1 256 1 1 0 No SS 1 1 1 *Factory default Table 7. Oscillator Enable/Disable EEPROM ADDRESS 37h RT Oscillator Off 1 RT Oscillator On* 0 *Factory default SLOPE COMPENSATION (mV/clock cycle) 0 20 40 60 80 100 120* 140 160 180 200 220 240 260 280 300 *Factory default EEPROM ADDRESS 3Bh 3Ah 39h 38h 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 Table 9. Slope Compensation with External Clock Applied to RTSYNC or RT Oscillator Off Table 6. Digital Soft-Start Duration RT OSCILLATOR Table 8. Slope Compensation with Clock Generated by RT Oscillator SLOPE COMPENSATION (mV/µs) 3Bh 3Ah 39h 38h 0 2 4 6 8 10 12* 14 16 18 20 22 24 26 28 30 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 EEPROM ADDRESS *Factory default ______________________________________________________________________________________ 21 MAX16816 Digital Soft-Start Duration Register (SS) The MAX16816 programmable soft-start feature allows the load current to ramp up in a controlled manner, eliminating output overshoot during startup. Soft-start begins once the device is enabled and VCC has exceeded the 5.5V (min) rising threshold voltage. Adjust the soft-start duration by configuring the EEPROM. Enter ‘111’ to disable the soft-start feature. See Table 6. MAX16816 Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming Applications Information Fault Protection The MAX16816 features built-in overvoltage protection, overcurrent protection, HICCUP mode current-limit protection, and thermal shutdown. Overvoltage protection is achieved by connecting OV to HI through a resistive voltage-divider. HICCUP mode limits the power dissipation in the external MOSFETs during severe fault conditions. Internal thermal shutdown protection safely turns off the converter when the IC junction temperature exceeds +165°C. Overvoltage Protection The overvoltage protection (OVP) comparator compares the voltage at OV with a 1.235V (typ) internal reference. When the voltage at OV exceeds the internal reference, the OVP comparator terminates PWM switching and no further energy is transferred to the load. The MAX16816 reinitiates soft-start once the overvoltage condition is removed. Connect OV to HI through a resistive voltage-divider to set the overvoltage threshold at the output. Setting the Overvoltage Threshold Connect OV to HI or to the high-side of the LEDs through a resistive voltage-divider to set the overvoltage threshold at the output (Figure 4). The overvoltage protection (OVP) comparator compares the voltage at OV with a 1.235V (typ) internal reference. Use the following equation to calculate resistor values: Inductor Selection The minimum required inductance is a function of operating frequency, input-to-output voltage differential, and the peak-to-peak inductor current (ΔI L ). Higher ΔI L allows for a lower inductor value while a lower ΔI L requires a higher inductor value. A lower inductor value minimizes size and cost, improves large-signal transient response, but reduces efficiency due to higher peak currents and higher peak-to-peak output ripple voltage for the same output capacitor. On the other hand, higher inductance increases efficiency by reducing the ripple current, ΔIL. However, resistive losses due to extra turns can exceed the benefit gained from lower ripple current levels, especially when the inductance is increased without also allowing for larger inductor dimensions. A good compromise is to choose ΔIL equal to 30% of the full load current. The inductor saturating current is also important to avoid runaway current during the output overload and continuous short circuit. Select the ISAT to be higher than the maximum peak current limit. Buck configuration: In a buck configuration the average inductor current does not vary with the input. The worstcase peak current occurs at high input voltage. In this case the inductance, L, for continuous conduction mode is given by: ⎛ VOV_LIM − VOV ⎞ ROV1 = ROV2 x ⎜ ⎟ VOV ⎝ ⎠ where VOV is the 1.235V OV threshold. Choose ROV1 and ROV2 to be reasonably high value resistors to prevent discharge of filter capacitors. This will prevent unnecessary undervoltage and overvoltage conditions during dimming. Load-Dump Protection The MAX16816 features load-dump protection up to 76V. LED drivers using the MAX16816 can sustain single fault load dump events. Repeated load dump events within very short time intervals can cause damage to the dimming MOSFET due to excess power dissipation. L = VOUT x ( VINMAX − VOUT ) VINMAX x fSW x ΔIL where VINMAX is the maximum input voltage, fSW is the switching frequency, and VOUT is the output voltage. VLED+ MAX16816 ROV1 OV Thermal Shutdown The MAX16816 contains an internal temperature sensor that turns off all outputs when the die temperature exceeds +165°C. Outputs are enabled again when the die temperature drops below +145°C. AGND ROV2 Figure 4. Setting the Overvoltage Threshold 22 ______________________________________________________________________________________ Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming L = VINMIN x ( VOUT − VINMIN ) VOUT x fSW x ΔIL where VINMIN is the minimum input voltage, VOUT is the output voltage, and fSW is the switching frequency. Buck-boost configuration: In a buck-boost converter the average inductor current is equal to the sum of the input current and the load current. In this case the inductance, L, is: L = VOUT x VINMIN (VOUT + VINMIN ) x fSW x ΔIL where VINMIN is the minimum input voltage, VOUT is the output voltage, and fSW is the switching frequency. Output Capacitor The function of the output capacitor is to reduce the output ripple to acceptable levels. The ESR, ESL, and the bulk capacitance of the output capacitor contribute to the output ripple. In most of the applications, the output ESR and ESL effects can be dramatically reduced by using low-ESR ceramic capacitors. To reduce the ESL effects, connect multiple ceramic capacitors in parallel to achieve the required bulk capacitance. In a buck configuration, the output capacitance, CF, is calculated using the following equation: CF ≥ (VINMAX − VOUT ) × VOUT ΔVR × 2 × L × VINMAX × fSW 2 where ΔVR is the maximum allowable output ripple. In a boost configuration, the output capacitance, CF, is calculated as: CF ≥ (VOUT − VINMIN ) × 2 × IOUT ΔVR × VOUT × fSW where IOUT is the output current. In a buck-boost configuration, the output capacitance, CF, is calculated as: CF ≥ 2 × VOUT × IOUT ΔVR × (VOUT + VINMIN ) × fSW where VOUT is the voltage across the load and IOUT is the output current. Input Capacitor An input capacitor connected between V CC and ground must be used when configuring the MAX16816 as a buck converter. Use a low-ESR input capacitor that can handle the maximum input RMS ripple current. Calculate the maximum allowable RMS ripple using the following equation: IIN(RMS) = IOUT × VOUT × (VINMIN - VOUT ) VINMIN In most of the cases, an additional electrolytic capacitor should be added to prevent input oscillations due to line impedances. When using the MAX16816 in a boost or buck-boost configuration, the input RMS current is low and the input capacitance can be small (see the Typical Operating Circuits). Operating the MAX16816 Without the Dimming Switch The MAX16816 can also be used in the absence of the dimming MOSFET. In this case, the PWM dimming performance is compromised but in applications that do not require dimming the MAX16816 can still be used. A short circuit across the load will cause the MAX16816 to disable the gate drivers and they will remain off until the input power is recycled. Switching Power MOSFET Losses When selecting MOSFETs for switching, consider the total gate charge, power dissipation, the maximum drain-to-source voltage, and package thermal impedance. The product of the MOSFET gate charge and RDS(ON) is a figure of merit, with a lower number signifying better performance. Select MOSFETs optimized for high-frequency switching applications. Layout Recommendations Typically, there are two sources of noise emission in a switching power supply: high di/dt loops and high dv/dt surfaces. For example, traces that carry the drain current often form high di/dt loops. Similarly, the heatsink of the MOSFET connected to the device drain presents a high dv/dt source; therefore, minimize the surface area of the heatsink as much as possible. Keep all PCB traces carrying switching currents as short as possible to minimize current loops. Use ground planes for best results. ______________________________________________________________________________________ 23 MAX16816 Boost configuration: In the boost converter, the average inductor current varies with line and the maximum average current occurs at low line. For the boost converter, the average inductor current is equal to the input current. In this case the inductance, L, is calculated as: MAX16816 Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming Careful PCB layout is critical to achieve low switching losses and clean, stable operation. Use a multilayer board whenever possible for better noise performance and power dissipation. Follow these guidelines for good PCB layout: • Use a large copper plane under the MAX16816 package. Ensure that all heat-dissipating components have adequate cooling. Connect the exposed pad of the device to the ground plane. • Isolate the power components and high current paths from sensitive analog circuitry. • Keep the high-current paths short, especially at the ground terminals. This practice is essential for stable, jitter-free operation. Keep switching loops short. • Connect AGND, SGND, and QGND to a ground plane. Ensure a low-impedance connection between all ground points. • Keep the power traces and load connections short. This practice is essential for high efficiency. Use thick copper PCBs (2oz vs. 1oz) to enhance full-load efficiency. • Ensure that the feedback connection to FB is short and direct. • Route high-speed switching nodes away from the sensitive analog areas. • To prevent discharge of the compensation capacitors, C1 and C2, during the off-time of the dimming cycle, ensure that the PCB area close to these components has extremely low leakage. Discharge of these capacitors due to leakage may result in degraded dimming performance. 1-Wire Interface EEPROM implementation uses a 1-Wire communication method. A 1-Wire net-based system consists of three main elements: a bus master with controlling software, the wiring and associated connectors, and 1-Wire devices. Data on the 1-Wire net is transferred with respect to time slots. For example, the master pulls the bus low and holds it for 15µs or less to write a logic ‘1’, and holds the bus low for at least 60µs to write a logic ‘0’. During EEPROM programming the MAX16816 is a 1-Wire slave device only. Data and clock signals are supplied through FAULT. MAX16816 1-Wire Function Commands Table 10 shows the list of 1-Wire function commands for the MAX16816. Use these commands to start the programming mode, write to the on-chip EEPROM, and read EEPROM through the 1-Wire interface. PASS_CODE_ONE: The PASS_CODE_ONE sequence is the first code that the MAX16816 must receive from the master. PASS_CODE_ONE must be received within the initial 8ms programming window after startup. PASS_CODE_TWO: The PASS_CODE_TWO sequence is the second code that the MAX16816 must receive during the 8ms programming window. The MAX16816 will start searching for PASS_CODE_TWO only after PASS_CODE_ONE has been received. EXT_EEM_MODE: The EXT_EEM_MODE command clears the PASS_CODE_ONE and PASS_CODE_TWO verification register. Use this command to exit programming mode. SET_WRITE_EE: The SET_WRITE_EE command is the write all command for the MAX16816. When the device detects the SET_WRITE_EE command the write Table 10. MAX16816 1-Wire Function Commands DATA BIT CODE D7 D6 D5 D4 D3 D2 D1 D0 HEX CODE PASS_CODE_ONE 0 0 1 0 1 0 0 1 29h PASS_CODE_TWO 0 0 0 0 1 0 0 1 09h EXT_EEM_MODE 0 0 0 0 0 0 0 1 01h SET_WRITE_EE 0 0 0 0 0 1 0 0 04h SET_WRITE_SCH ADD ADD ADD ADD DATA DATA DATA DATA — SET_READ_SCH 0 0 0 0 0 1 1 0 06h COMMAND 24 ______________________________________________________________________________________ Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming Programming To program the MAX16816 on-chip EEPROM with a pulldown device, directly connect FAULT to the DATA IN input of a microcontroller (µC). Also, connect FAULT to the DATA OUT output of a µC using an external switch (Figure 5). Connect the EN of the µC directly to UVEN to control the internal timer of the MAX16816 for programming purposes. Ensure that V CC is greater than the UVLO threshold because both UVEN and FAULT are pulled up to 5V. See the Electrical Characteristic tables for details. VCC EN UVEN μC MAX16816 DATA IN DATA OUT READ FAULT WRITE Figure 5. Programming Through a FAULT Pin Table 11. MAX16816 Memory Map (Scratchpad) SCRATCHPAD ADDRESS EEPROM ADDRESS 1h Reserved Reserved 2h Reserved Reserved 3h Reserved Reserved 4h Reserved Reserved 5h Reserved Reserved REGISTER 6h–9h 14h–23h Reserved Ah 24h–27h Binning Adjustment Register Bh 28h–2Bh REG2 Control Register Ch 2Ch–2Fh Reserved Dh 30h–33h Blanking Time Adjustment Register Eh 34h–37h Digital Soft-Start Duration Register, Internal Oscillator Enable Bit Fh 38h–3Bh Slope Compensation Register ______________________________________________________________________________________ 25 MAX16816 sequence begins. All EEPROM bits are copied to the EEPROM from the scratchpad with a single SET_WRITE_EE command. This command also sets an internal BUSY flag to mask all other incoming signals. SET_WRITE_SCH: The SET_WRITE_SCH command transfers data to the scratchpad. The 4 MSBs contain the register address and the 4 LSBs contain the data to be written. The internal BUSY flag is not set by this command. Table 11 shows the MAX16816 EEPROM memory organization. Use the SET_WRITE_EE command to transfer data from the scratchpad to the EEPROM. SET_READ_SCH: The SET_READ_SCH command is the command to read data in the scratch pad buffer. Once the MAX16816 receives the SET_READ_SCH command, data on the scratchpad register is shifted out. After 60 clock cycles, the MAX16816 completes the SET_READ_SCH sequence. The BUSY signal is not set by this command. MAX16816 Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming Programming Sequences The µC (master) starts the communication with the MAX16816 by pulling UVEN high. The MAX16816 then does the handshaking with the µC by pulling FAULT low. Once the µC receives the handshaking signal, it begins the initialization sequences to reset the 1-Wire interface. The sequence consists of a reset pulse from the µC followed by a presence pulse from the MAX16816. At this point the µC must send PASS_CODE_ONE and PASS_CODE_TWO. These pass codes must be received by the MAX16816 within the 8ms programming slot to allow the MAX16816 to enter the EE programming mode. 1-Wire Signaling The MAX16816 requires strict protocols to ensure data integrity. The protocol consists of four types of signaling on one line: reset sequence with Reset Pulse and Presence Pulse, Write-Zero, Write-One, and Read-Data. Except for the Presence Pulse, the bus master initiates all falling edges. Externally pull FAULT below VIL to indicate a logic-input low. Release the pulldown device to indicate a logicinput high. The MAX16816 will pull FAULT low below VOL to indicate a logic-output low. FAULT is pulled high with an internal 10kΩ resistor above VOH to indicate a logic-output high. Initialization Procedure (Reset and Presence Pulses) All 1-Wire communication with the MAX16816 begins with an initialization sequence that consists of a Reset Pulse from the master followed by a Presence Pulse from the MAX16816 (Figure 6). When the MAX16816 sends the Presence Pulse in response to the Reset Pulse, it is indicating to the master that it is ready to receive and transmit data. During the initialization sequence, the bus master transmits the reset pulse by pulling the 1-Wire bus low for a minimum of 480µs. The bus master then releases the bus and goes into receive mode. When the bus is released, the pullup resistor pulls the 1-Wire bus high. When the MAX16816 detects this rising edge, it waits 15µs to 60µs and then transmits a Presence Pulse by pulling the 1-Wire bus low for 60µs to 240µs. Read and Write Time Slots The bus master writes data to the MAX16816 during write time slots and reads data from the MAX16816 during read time slots. One bit of data is transmitted over the 1-Wire bus per time slot. MASTER Tx "RESET PULSE" MASTER Rx "PRESENCE PULSE" tMSP VOH VOL OR VIL 0V tRSTL RESISTOR MASTER MAX16816 Figure 6. 1-Wire Initialization Timing 26 ______________________________________________________________________________________ Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming low. When the bus is released, the pullup resistor will pull the bus high. To generate a Write-0 time slot, the bus master must continue to hold the bus low for the duration of the time slot (at least 60µs) after pulling the 1-Wire bus low. The MAX16816 samples the 1-Wire bus during a window that lasts from 15µs to 60µs after the master initiates the Write time slot. If the bus is high during the samples window, a ‘1’ is written to the MAX16816. If the line is low, a ‘0’ is written to the MAX16816. tW1L VOH MAX16816 SAMPLING WINDOW VOL 0V tREC tSLOT RESISTOR MASTER Figure 7. 1-Wire Write-1 Time Slot tW0L VOH MAX16816 SAMPLING WINDOW VIL 0V tREC tSLOT RESISTOR MASTER Figure 8. 1-Wire Write-0 Time Slot ______________________________________________________________________________________ 27 MAX16816 Write Time Slots There are two types of write time slots: Write-1 time slots and Write-0 time slots. The bus master uses a Write-1 time slot to write a logic ‘1’ to the MAX16816 and a Write-0 time slot to write a logic ‘0’. All write time slots must be a minimum of 60µs in duration with a minimum of a 1µs recovery time between individual Write slots. Both types of write time slots are initiated by the master pulling the 1-Wire bus low (Figures 7 and 8). To generate a Write-1 time slot, the bus master must release the 1-Wire bus within 15µs after pulling the bus MAX16816 Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming Read Time Slots The MAX16816 can only transmit data to the master when the master issues read time slots. All read time slots must be a minimum of 60µs in duration with a minimum of a 1µs recovery time between slots. A read time slot is initiated by the master device pulling the 1-Wire bus low for a minimum of 1µs and then releasing it (Figure 9). After the master initiates the read time slot, the MAX16816 will transmit a ‘1’ or a ‘0’ on the bus. The MAX16816 transmits a ‘1’ by leaving the bus high and transmits a ‘0’ by pulling the bus low. When transmitting a ‘0’, the MAX16816 will release the bus before the end of the time slot, and the bus will be pulled back to its high idle state by the pullup resistor. Output data from the MAX16816 is valid for 15µs after the falling edge that initiated the read time slot. Therefore, the master must release the bus and then sample the bus state within 15µs from the start of the slot. tMSR tRL VOH MASTER SAMPLING WINDOW VIL / VOL 0V tREC tSLOT RESISTOR MASTER MAX16816 Figure 9. 1-Wire Read Time Slot 28 ______________________________________________________________________________________ Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming VCC REG2 HI CLMP CS- CS+ LO TOP VIEW FAULT PROCESS: BiCMOS 32 31 30 29 28 27 26 25 + 24 N.C. 2 23 DGT REG1 3 22 QGND AGND 4 21 SNS- REF 5 20 SNS+ DIM 6 19 DRI RTSYNC 7 18 DRV CLKOUT 8 17 SGND MAX16816 9 10 11 12 13 14 15 16 COMP CS FB OV SGND *EP I.C. UVEN I.C. 1 I.C. N.C. TQFN (5mm x 5mm) *EP = EXPOSED PAD ______________________________________________________________________________________ 29 MAX16816 Pin Configuration Chip Information Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming MAX16816 Typical Operating Circuits (continued) VIN RCS CCLMP RUV2 VCC RUV1 CS+ CS- DGT LO CF CLMP UVEN RD QS LEDs DRV CUVEN SNS+ RSENSE REF MAX16816 SNS- R3 QGND ROV1 DIM R4 OV FAULT REG2 RT ROV2 DRI RTSYNC HI COMP CS REG1 FB AGND SGND CREG2 CREG1 R1 C2 R2 C1 BOOST CONFIGURATION 30 ______________________________________________________________________________________ Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming VIN RCS CCLMP RUV2 CF VCC HI LO CLMP CS- CS+ DGT QS RD FAULT DRV RUV1 LEDs SNS+ UVEN RSENSE CUVEN SNS- MAX16816 DIM QGND DIM REG1 CREG1 RT RTSYNC COMP OV CS AGND FB R1 SGND REG2 DRI CREG2 C2 C1 R2 BUCK CONFIGURATION ______________________________________________________________________________________ 31 MAX16816 Typical Operating Circuits (continued) 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.) QFN THIN.EPS MAX16816 Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming 32 ______________________________________________________________________________________ Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming 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 ____________________ 33 © 2008 Maxim Integrated Products Heaney is a registered trademark of Maxim Integrated Products, Inc. MAX16816 Package Information (continued) (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.)