ML4836CP

July 2000 PRELIMINARY ML4836* Compact Fluorescent Electronic Dimming Ballast Controller GENERAL DESCRIPTION The ML4836 is a complete solution for a dimmable or a non-dimmable high efficiency electronic ballast especially tailored for a compact fluorescent lamp (CFL). The Bi-CMOS ML4836 contains controllers for dimming ballast with end-of-life detection capability. The ballast controller section provides for programmable starting sequence with individual adjustable preheat and lamp out-of-socket interrupt times. The ML4836 provides latch type shut down comparator for ballast controllers in the event of end-of-life for the CFL. FEATURES s s Programmable start scenario for rapid/instant start lamps Triple frequency control network for dimming or starting to handle various lamp sizes Programmable restart for lamp out condition to reduce ballast heating. Internal over-temperature shutdown Low start-up current; < 0.55mA (* Indicates Part is End Of Life as of July 1, 2000) s s s BLOCK DIAGRAM INTERRUPT CONTROL AND GATING LOGIC 7 LAMP FB 2 LEAO 3 ANTI-FLASH COMPENSATION AND DIMMING LEVEL INTERFACE RSET RT/CT RT2 VCO VARIABLE FREQUENCY OSCILLATOR THREE-FREQUENCY CONTROL SEQUENCER OUT A 13 OUT B OUTPUT DRIVERS PGND 11 PRE-HEAT AND INTERRUPT TIMERS END-OF-LAMP DETECT AND POWER SHUTOFF UNDER-VOLTAGE AND THERMAL SHUTDOWN AGND REF 10 1 VCC 14 LAMP OUT DETECT AND AUTOMATIC LAMP RESTART RX/CX 8 12 4 6 5 PWDET 9 1 ML4836 PIN CONFIGURATION ML4836 14-Pin SOIC (S14) 14-Pin DIP (P14) REF LAMP FB LEAO RSET RT2 RT/CT INTERRUPT 1 2 3 4 5 6 7 14 13 12 11 10 9 8 VCC OUTA OUT B PGND AGND PWDET RX/CX TOP VIEW PIN DESCRIPTION PIN NAME FUNCTION PIN NAME FUNCTION 1 2 REF LAMP FB Buffered output for the 7.5V reference Inverting input of the lamp error amplifier, used to sense and regulate lamp arc current. Also the input node for dimmable control. Output of the lamp current error transconductance amplifier used for lamp current loop compensation External resistor which SETS oscillator FMAX, and RX/CX charging current Oscillator timing component to set start frequency Oscillator timing components 7 INTERRUPT Input used for lamp-out detection and restart. A voltage less than 1V will reset the IC and cause a restart after a programmable interval. RX/CX PWDET AGND PGND OUT B OUT A VCC Sets the timing for preheat and interrupt. Lamp output power detection Analog ground Power ground. Ballast MOSFET driver output Ballast MOSFET driver output Positive supply voltage 8 9 10 3 LEAO 4 5 6 RSET RT2 RT/CT 11 12 13 14 2 ML4836 ABSOLUTE MAXIMUM RATINGS Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. Supply Current (ICC) ............................................................ 50mA Output Current, Source or Sink (OUT A, OUT B) DC ............................................ 250mA PIFB Input Voltage ............................................ –3V to 2V Maximum Forced Voltage (PEAO, LEAO) ............................................ –0.3V to 7.7V Maximum Forced Current (LEAO) ................................................................. ±20mA Junction Temperature .............................................. 150ºC Storage Temperature Range...................... –65ºC to 150ºC Lead Temperature (Soldering, 10 sec) ...................... 260ºC Thermal Resistance (qJA) ML4836CP ............................................................... C/W ML4836CS ............................................................... C/W OPERATING CONDITIONS Temperature Range ........................................ 0°C to 85°C ELECTRICAL CHARACTERISTICS Unless otherwise specified, VCC = VCCZ –0.5V, RSET = 11.8kW, RT = 14.7kW, RT2 = 53.6kW, CT = 1.5nF, TA = Operating Temperature Range (Note 1) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS LAMP CURRENT AMPLIFIER (LAMP FB, LEAO) Input Bias Current Small Signal Transconductance Input Bias Voltage Output Low Output High Source Current Sink Current OSCILLATOR Initial Accuracy (FMIN) Total Variation (FMIN) Initial Accuracy (START) Total Variation (START) Ramp Valley to Peak Initial Accuracy (Preheat) Total Variation (Preheat) CT Discharge Current Output Drive Deadtime REFERENCE BUFFER Output Voltage Line Regulation Load Regulation Temperature Stability Total Variation Long Term Stabilty Line, Load, Temperature Tj = 125ºC, 1000 hrs 7.35 5 TA = 25ºC, IO = 0mA VCCZ – 4V < VCC < VCCZ – 0.5V 1mA < IO < 10mA 7.4 7.5 10 2 0.4 7.65 7.6 25 15 V mV mV % V mV TA = 25ºC Line, Temperature VRTCT = 2.5V CT = 1.5nF 60.8 60.8 6.0 TA = 25ºC Line, Temperature TA = 25ºC Line, Temperature 39.2 39.2 49 49 2.6 64 64 7.5 0.7 67.2 67.2 9.0 50 40 40.8 40.8 51 51 kHz kHz kHz kHz V kHz kHz mA us LAMP FB = 3V, RL = ¥ LAMP FB = 2V, RL = ¥ LAMP FB = 0V, LEAO = 6V LAMP FB = 5V, LEAO = 0.3V 7.1 -80 80 35 -0.3 0.2 7.5 -220 220 -0.3 75 -1.0 105 5.0 0.4 µA µ V V V µA µA W 3 ML4836 ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER REFERENCE BUFFER (Continued) Short Circuit Current RSET Voltage PREHEAT AND INTERRUPT TIMER (RX = 346kW, CX = 10µF) RX/CX Charging Current RX/CX Open Circuit Voltage RX/CX Maximum Voltage Preheat Lower Threshold Preheat Upper Threshold Start Period End Threshold Interrupt Disable Threshold Hysteresis Input Bias Current POWER SHUTDOWN Power Shutdown Voltage OUTPUTS (OUT A, OUT B, PFC OUT) Output Voltage Low IOUT = 20mA IOUT = 200mA Output Voltage High Output Voltage High Output Voltage Low in UVLO Output Rise and Fall Time UNDER VOLTAGE LOCKOUT AND BIAS CIRCUITS IC Shunt Voltage (VCCZ) Start-up Threshold (VCC START) Hysteresis Start-up Current Interrupt Current Operating Current Shutdown Temperature Hysteresis Note 1: Limits are guaranteed by 100% testing, sampling, or correlation with worst case test conditions. (Continued) CONDITIONS MIN TYP MAX UNITS 40 2.4 2.5 2.6 mA V –48 0.4 7.0 1.6 4.4 6.2 1.1 0.16 –52 0.7 7.3 1.75 4.65 6.6 1.25 0.26 –56 1.0 7.8 1.9 4.9 6.9 1.4 0.36 1 µA V V V V V V V µA 0.9 1.0 1.1 V 0.1 1.0 VCC – 0.2 VCC – 0.1 VCC – 2.0 VCC – 1.0 0.2 2.0 V V V V IOUT = 20mA IOUT = 200mA IOUT = 20mA, VCC < VCC START CL = 1000pF 0.2 50 V ns ICC = 15mA 14.0 14.8 15.5 V V V µA µA mA ºC ºC VCCz – 1.5 VCCz – 1.0 VCCz – 0.5 3.0 VCC START – 0.2V (VCCz – 0.5V), INTERRUPT = 0V (VCCz – 0.5V) 3.7 350 500 4.0 140 30 4.4 550 750 8.0 4 ML4836 FUNCTIONAL DESCRIPTION The ML4836 consists of flexible ballast control section. Start-up and lamp-out retry timing are controlled by the selection of external timing components, allowing for control of a wide variety of different lamp types. The ballast section controls the lamp power using frequency modulation (FM) with additional programmability provided to adjust the VCO frequency range. This allows for the IC to be used with a variety of different output networks. Figure 1 depicts a detailed block diagram of ML4836. The ML4836 provides several safety features. See the corresponding sections for more details: • End-of-lamp life detection to detect EOL and shut-off lamps; See End Of Life Section. • Thermal shutdown for temperature sensing extremes; See IC Bias, Under-Voltage Lockout and Thermal Shutdown Section. • Relamping starting with anti-flash for programmable restart for lamp out conditions while minimizing “flashing” when powering from full power to dimming levels; See Starting, Re-Start, Preheat and Interrupt Section REF 1 6.75V + – REF_OK THERMAL SHUTDOWN OUT A 13 OUT B + TEMP 140ºC/100ºC PGND 12 11 14 VCC – REF Q Q R S PWDET + – + – 9 1.05V 1.20V/1V INTERRUPT AGND 10 Q Q S R COMP 7 – + RX/CX 6.65V/1.25V Q T – RT2 Q UVLO + 5 14V + PREHEAT RT/CT LEAO 3 LAMP FB – + 4.65V/ 1.75V – 6 CLK RX/CX OSCILLATOR 8 2 2.5V 4 RSET V TO I V TO I Figure 1. Detailed Block Diagram 5 ML4836 FUNCTIONAL DESCRIPTION (Continued) The ML4836 implements a triple frequency operation scheme: programmable three-frequency sequence for preheat, ignition, and dimming, that extends lamp life, simplifies lamp network design, and starts lamps at any dimming level without flashing. This addresses the need for a high-Q network for starting sequence and low-Q network for operation, minimizing parasitic losses and improving overall power efficiency. The values for the pre-heat, start, operation, and restart can be programmed or selected (Figure 2). TRANSCONDUCTANCE AMPLIFIERS The Lamp voltage feedback amplifier is implemented as an operational transconductance amplifier. It is designed to have low small signal forward transconductance such that a large value of load resistor (R1) and a low value ceramic capacitor (