July 2000 PRELIMINARY ML4836* Compact Fluorescent Electronic Dimming Ballast Controller GENERAL DESCRIPTION FEATURES 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. ■ 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 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. (* Indicates Part is End Of Life as of July 1, 2000) BLOCK DIAGRAM INTERRUPT 7 CONTROL AND GATING LOGIC ANTI-FLASH COMPENSATION AND DIMMING LEVEL INTERFACE LAMP FB 2 LEAO 3 OUT A 4 6 5 RSET RT/CT 13 VARIABLE FREQUENCY OSCILLATOR OUT B 12 OUTPUT DRIVERS THREE-FREQUENCY CONTROL SEQUENCER PGND RT2 11 VCO PRE-HEAT AND INTERRUPT TIMERS PWDET 9 END-OF-LAMP DETECT AND POWER SHUTOFF UNDER-VOLTAGE AND THERMAL SHUTDOWN AGND REF 10 1 LAMP OUT DETECT AND AUTOMATIC LAMP RESTART RX/CX 8 VCC 14 1 ML4836 PIN CONFIGURATION ML4836 14-Pin SOIC (S14) 14-Pin DIP (P14) REF 1 14 VCC LAMP FB 2 13 OUTA LEAO 3 12 OUT B RSET 4 11 PGND RT2 5 10 AGND RT/CT 6 9 PWDET INTERRUPT 7 8 RX/CX TOP VIEW PIN DESCRIPTION PIN NAME FUNCTION PIN NAME 1 REF Buffered output for the 7.5V reference 7 LAMP FB Inverting input of the lamp error amplifier, used to sense and regulate lamp arc current. Also the input node for dimmable control. 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. 8 RX/CX Sets the timing for preheat and interrupt. 9 PWDET Lamp output power detection 10 AGND Analog ground 11 PGND Power ground. 12 OUT B Ballast MOSFET driver output 13 OUT A Ballast MOSFET driver output 14 VCC Positive supply voltage 2 3 4 LEAO Output of the lamp current error transconductance amplifier used for lamp current loop compensation RSET External resistor which SETS oscillator FMAX, and RX/CX charging current 5 RT2 Oscillator timing component to set start frequency 6 RT/CT Oscillator timing components 2 FUNCTION ML4836 ABSOLUTE MAXIMUM RATINGS Junction Temperature .............................................. 150ºC Storage Temperature Range...................... –65ºC to 150ºC Lead Temperature (Soldering, 10 sec) ...................... 260ºC Thermal Resistance (qJA) ML4836CP ............................................................... C/W ML4836CS ............................................................... C/W 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 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 -0.3 -1.0 µA 75 105 µ LAMP CURRENT AMPLIFIER (LAMP FB, LEAO) Small Signal Transconductance 35 Input Bias Voltage -0.3 W Input Bias Current 5.0 V 0.4 V Output Low LAMP FB = 3V, RL = ¥ Output High LAMP FB = 2V, RL = ¥ 7.1 7.5 V Source Current LAMP FB = 0V, LEAO = 6V -80 -220 µA Sink Current LAMP FB = 5V, LEAO = 0.3V 80 220 µA 40 0.2 OSCILLATOR Initial Accuracy (FMIN) TA = 25ºC 39.2 Total Variation (FMIN) Line, Temperature 39.2 Initial Accuracy (START) TA = 25ºC 49 Total Variation (START) Line, Temperature 49 Ramp Valley to Peak 50 40.8 kHz 40.8 kHz 51 kHz 51 kHz 2.6 V Initial Accuracy (Preheat) TA = 25ºC 60.8 64 67.2 kHz Total Variation (Preheat) Line, Temperature 60.8 64 67.2 kHz CT Discharge Current VRTCT = 2.5V 6.0 7.5 9.0 mA Output Drive Deadtime CT = 1.5nF 0.7 us REFERENCE BUFFER Output Voltage TA = 25ºC, IO = 0mA Line Regulation Load Regulation 7.4 7.5 7.6 V VCCZ – 4V < VCC < VCCZ – 0.5V 10 25 mV 1mA < IO < 10mA 2 15 mV Temperature Stability 0.4 Total Variation Line, Load, Temperature Long Term Stabilty Tj = 125ºC, 1000 hrs 7.35 % 7.65 5 V mV 3 ML4836 ELECTRICAL CHARACTERISTICS SYMBOL (Continued) PARAMETER CONDITIONS MIN TYP MAX UNITS REFERENCE BUFFER (Continued) Short Circuit Current 40 RSET Voltage mA 2.4 2.5 2.6 V RX/CX Charging Current –48 –52 –56 µA RX/CX Open Circuit Voltage 0.4 0.7 1.0 V RX/CX Maximum Voltage 7.0 7.3 7.8 V Preheat Lower Threshold 1.6 1.75 1.9 V Preheat Upper Threshold 4.4 4.65 4.9 V Start Period End Threshold 6.2 6.6 6.9 V Interrupt Disable Threshold 1.1 1.25 1.4 V 0.16 0.26 0.36 V 1 µA 1.0 1.1 V IOUT = 20mA 0.1 0.2 V IOUT = 200mA 1.0 2.0 V PREHEAT AND INTERRUPT TIMER (RX = 346kW, CX = 10µF) Hysteresis Input Bias Current POWER SHUTDOWN Power Shutdown Voltage 0.9 OUTPUTS (OUT A, OUT B, PFC OUT) Output Voltage Low Output Voltage High IOUT = 20mA VCC – 0.2 VCC – 0.1 V Output Voltage High IOUT = 200mA VCC – 2.0 VCC – 1.0 V Output Voltage Low in UVLO IOUT = 20mA, VCC < VCC START Output Rise and Fall Time CL = 1000pF 0.2 50 V ns UNDER VOLTAGE LOCKOUT AND BIAS CIRCUITS IC Shunt Voltage (VCCZ) ICC = 15mA Start-up Threshold (VCC START) 4 14.8 15.5 VCCz – 1.5 VCCz – 1.0 VCCz – 0.5 Hysteresis Note 1: 14.0 3.0 V V 3.7 4.4 V Start-up Current VCC START – 0.2V 350 550 µA Interrupt Current (VCCz – 0.5V), INTERRUPT = 0V 500 750 µA Operating Current (VCCz – 0.5V) 4.0 8.0 mA Shutdown Temperature 140 ºC Hysteresis 30 ºC Limits are guaranteed by 100% testing, sampling, or correlation with worst case test conditions. ML4836 FUNCTIONAL DESCRIPTION • End-of-lamp life detection to detect EOL and shut-off lamps; See End Of Life Section. 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. • 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 The ML4836 provides several safety features. See the corresponding sections for more details: REF OUT A REF_OK 1 + 6.75V 13 THERMAL SHUTDOWN – OUT B 14 VCC + TEMP – 140ºC/100ºC 12 PGND 11 REF AGND Q R Q S Q S Q R PWDET 9 + – 1.05V + 1.20V/1V INTERRUPT COMP – 10 – RX/CX + 6.65V/1.25V 7 Q RT2 T Q – 14V + UVLO + 4.65V/ 1.75V PREHEAT – RT/CT 3 LAMP FB OSCILLATOR RX/CX RSET V TO I 2 – + 4 6 LEAO CLK 8 5 2.5V 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). to have low small signal forward transconductance such that a large value of load resistor (R1) and a low value ceramic capacitor (<1µF) can be used for AC coupling (C1) in the frequency compensation network. The compensation network shown in Figure 5 will introduce a zero and a pole at: fZ = 1 2p R 1C1 fP = 1 2p R 1C 2 (2) TRANSCONDUCTANCE AMPLIFIERS Figure 3 shows the output configuration for the operational transconductance amplifiers. The Lamp voltage feedback amplifier is implemented as an operational transconductance amplifier. It is designed A DC path to ground or VCC at the output of the transconductance amplifiers will introduce an offset error. PREHEAT SET TIME VALUES FOR PREHEAT, START AND OPERATION, AND RESTART f1 HIGH Q ML4836 LOW Q f2 f3 START OPERATION Figure 2. Three Frequency Design Model CURRENT MIRROR IN IQ + IQ – OUT gmVIN 2 io = gmVIN gmVIN 2 IN OUT CURRENT MIRROR Figure 3. Output Configuration 6 ML4836 FUNCTIONAL DESCRIPTION (Continued) The magnitude of the offset voltage that will appear at the input is given by VOS = io/gm. For an io of 1µA and a gm of 0.05 µW the input referred offset will be 20mV. Capacitor C1 as shown in Figure 4 is used to block the DC current to minimize the adverse effect of offsets. Slew rate enhancement is incorporated into all of the operational transconductance amplifiers in the ML4836. This improves the recovery of the circuit in response to power up and transient conditions. The response to large signals will be somewhat non-linear as the transconductance amplifiers change from their low to high transconductance mode, as illustrated in Figure 5. END OF LAMP LIFE At the end of a lamp’s life when the emissive material is depleted, the arc current is rectified and high voltage occurs across the lamp near the depleted cathode. The ballast acts as a constant current source so power is dissipated near the depleted cathode which can lead to arcing and bulb cracking. Compact fluorescent lamps are more prone to cracking or shattering because their small diameter can’t dissipate as much heat as the larger linear lamps. Compact fluorescents also present more of a safety hazard since they are usually used in downlighting systems without reflector covers. iO LAMP FB 1 – 2.5V + LEAO VIN DIFFERENTIAL 0 R1 C2 LINEAR SLOPE REGION C1 Figure 4. Compensation Network Figure 5. Transconductance Amplifier Characteristics PFC LAMP NETWORK LAMP R9 ML4836 Figure 6. Simplified Model of ML4836 EOL Functionality 7 ML4836 FUNCTIONAL DESCRIPTION (Continued) EOL and the ML4836 that both ballast output drivers will be low during the discharging time tDIS of the oscillator capacitor CT. The ML4836 uses a circuit that creates a DC voltage representative of the power supplied to the lamps through the inverter when use in conjuction with PFC. This voltage is used by the ML4836 to latch off the ballast when it exceeds an internal threshold. An external resistor can be used as the “EOL latch resistor” to set the power level trip point, as shown in by R9 in Figure 6. OSCILLATOR The VCO frequency ranges are controlled by the output of the LFB amplifier (RSET). As lamp current decreases, LFB OUT falls in voltage, causing the CT charging current to increase, thereby causing the oscillator frequency to increase. Since the ballast output network attenuates high frequencies, the power to the lamp will be decreased. The oscillator frequency is determined by the following equations: BALLAST OUTPUT SECTION The IC controls output power to the lamps via frequency modulation with non-overlapping conduction. This means REF 1 RT2 RT RT2 5 DURING PREHEAT ICHG = 2.5V RSET AFTER PREHEAT LEA_ENB = HI ICHG = 5V – 7.5V RSET 8K±25% LEA_ENB = LOW ICHG = 5V – LEAO RSET 8K±25% ICHG 6 RT/CT + 3.8/1.2V – LEA_ENB 7 7.5mA – 1.20/1.0V 14 + VCC 0.625 RSET 8 CT + INTERRUPT RX/CX 4.65/1.75V 7.5V NOTE 1: RSET SHOULD BE SELECTED SUCH THAT AFTER PREHEAT WITH LEA_ENB "HI", ICHG MUST BE < 0. ICHG IS A UNI-DIRECTIONAL SOURCE CURRENT ONLY. – + CLOCK tDIS tCHG VTH = 3.8V CT VTL = 1.2V Figure 7. Oscillator Block Diagram and Timing 8 ML4836 FUNCTIONAL DESCRIPTION (Continued) FOSC = 1 (3) t CHG + t DIS and t CHG = R T C T In V V REF REF + ICHG ´ R T - VTL + IICHG ´ R T - VTH In preheat condition, charging current is fixed at (4) The oscillator’s minimum frequency is set when ICHG = 0 where: FMIN ≅ 1 0.54 × RT CT (5) The oscillator's start frequency can be expressed by: FSTART = 2 1 7 ICHG (PREHEAT ) = 1. The output of the preheat timer (6) The charging current behavior can be expressed as: 5V LEAO R SET 8k ± 25% (7) The highest frequency is attained when ICHG is highest, which is attained when voltage at LFB OUT is at 0V: Both equations assume that tCHG >> tDIS. When LFB OUT is high, ICHG = 0 and the minimum frequency occurs. The charging current varies according to two control inputs to the oscillator: 25 . R SET In running mode, charging current decreases as the voltage rises from 0V to VOH at the LAMP FB amplifier. ICHG = (5a) 0.54 × RT RT 2 × CT 2. The voltage at LFB OUT (lamp feedback amplifier output) ICHG(0) = 5 R SET (8) Highest lamp power, and lowest output frequency are attained when voltage at LFB OUT is at its maximum output voltage (VOH). VCC VCCZ V(ON) V(OFF) t ICC 5.5mA 0.34mA t Figure 8. Typical VCC and ICC Waveforms when the ML4836 is Started with a Bleed Resistor from the Rectified AC Line and Bootstrapped from an Auxiliary Winding. 9 ML4836 FUNCTIONAL DESCRIPTION (Continued) In this condition, the minimum operating frequency of the ballast is set per equation 5 above. For the IC to be used effectively in dimming ballasts with higher Q output networks a larger CT value and lower RT value can be used, to yield a smaller frequency excursion over the control range (voltage at LFB OUT). The discharge current is set to 7.5mA. The operation of the oscillator is hown in Figure 7. Assuming that IDIS >>IRT: ballast cost, the ML4836 includes a temperature sensor which will inhibit ballast operation if the IC’s junction temperature exceeds 140°C. In order to use this sensor in lieu of an external sensor, care should be taken when placing the IC to ensure that it is sensing temperature at the physically appropriate point in the ballast. The ML4836’s die temperature can be estimated with the following equation: TJ @ TA + (PD + 65° C / W) STARTING, RE-START, PREHEAT AND INTERRUPT t DIS( VCO) @ 600 ´ C T (9) The lamp starting scenario implemented in the ML4836 is designed to maximize lamp life and minimize ballast heating during lamp out conditions. IC BIAS, UNDER-VOLTAGE LOCKOUT AND THERMAL SHUTDOWN The IC includes a shunt clamp which will limit the voltage at VCC to 14.5V (VCCZ). The IC should be fed with a current limited source, typically derived from the ballast transformer auxiliary winding. When VCC is below VCCZ – 1.1V, the IC draws less than 0.55mA of quiescent current and the outputs are off. This allows the IC to start using a “bleed resistor” from the rectified AC line. The ICC start-up condition is shown in Figure 7. To help reduce The circuit in Figure 9 controls the lamp starting scenarios: Filament preheat and lamp out interrupt. CX is charged with a current of IR(SET)/4 and discharged through RX. The voltage at CX is initialized to 0.7V (VBE) at power up. The time for CX to rise to 4.65V is the filament preheat time. During that time, the oscillator charging current (ICHG) is 2.5/RSET. This will produce a high frequency for filament preheat, but will not produce sufficient voltage to ignite the lamp or cause significant glow current. 0.625 RSET RX/CX + 10 RX CX 1.75/4.65 HEAT – LEA_ENB OR DIMMING LOCKOUT + INTERRUPT 9 1.0/1.20 – S + 1.25/6.65 – R Figure 9. Lamp Preheat and Interrupt Timers 10 (10) Q INHIBIT ML4836 FUNCTIONAL DESCRIPTION (Continued) After cathode heating, the inverter frequency drops to FSTART causing a high voltage to appear to ignite the lamp. If lamp current is not detected when the lamp is supposed to have ignited, the CX charging current is shut off and the inverter is inhibited until CX is discharged by RX to the 1.25V threshold. Shutting off the inverter in this manner prevents the inverter from generating excessive heat when the lamp fails to strike or is out of socket. Typically this time is set to be fairly long by choosing a large value of RX. LFB OUT is ignored by the oscillator until INTERRUPT is above 1.20V The CX pin is clamped to about 7.5V. Care should also be taken not to turn on the VCCZ clamp so as not to dissipate excessive power in the IC. This will cause the temp sensor to become active at a lower ambient temperature. A summary of the operating frequencies in the various operating modes is shown below. OPERATING MODE OPERATING FREQUENCY Preheat [F(MAX) to F(MIN)] 2 After Preheat Dimming Control F(START) F(MIN) to F(MAX) 7.5 6.75 RX/CX 4.75 1.25 .7 0 HEAT LEA_ENB OR DIMMING LOCKOUT INTERRUPT INHIBIT Figure10. Lamp Starting and Restart Timing 11 ML4836 TYPICAL APPLICATIONS The ML4836 can be used for a variety of lamp types: The ML4836 can also be used for dimming applications. For example, 20:1 dimming can be achieved using the ML4836 with external dimming units. The applications schematics shown in Figures 11 and 12 are examples of the various uses of the ML4836. R17 C17 R16 C12 7 R13 C12 8 C13 R15 1 2 R6 8 RX/CX C6 INTRPT RT2 RT/CT 7 6 RSET 5 4 LEAO R11 R12 9 PWDET AGND 10 11 PGND 12 OUTB 13 OUTA LFB C5 R9 R10 C4 Figure11. 120V CFL Ballast 12 3 2 REF D4 R8 L2 NEUTRAL HOT F1 D3 R1 C1 L1 C8 D5 1 R7 D2 C3 ML4836 VCC D6 R3 D1 C2 R2 14 C7 C9 R5 R4 C10 6 T2 3 D9 C16 C14 Q3 D8 Q2 D7 R14 D10 C15 8 7 2 1 L2 6 5 C13 B B R R T4 or compact fluorescent lamps IEC T8 (linear lamps) T5 linear lamps T12 linear lamps R10 C4 R8 – + C5 R9 L2 7 6 5 4 3 2 1 C6 INTRPT RT/CT RT2 RSET D5 C8 R11 VCC D6 R12 RX/CX PWDET AGND PGND OUTB OUTA ML4836 R1 LEAO LFB REF R7 D4 D3 8 9 10 11 12 13 14 C7 R3 R2 C9 R6 R5 R4 C10 7 6 D7 C17 7 6 5 R13 C12 D9 C16 C18 D10 C15 2 1 L2 8 R16 Q3 C14 Q2 8 C13 R15 D8 R14 1 2 3 C12 T2 R17 B B R R ML4836 Figure12. DC Input CFL Ballast 13 ML4836 PHYSICAL DIMENSIONS inches (millimeters) Package: S14 14-Pin SOIC 0.337 - 0.347 (8.56 - 8.81) 14 0.148 - 0.158 0.228 - 0.244 (3.76 - 4.01) (5.79 - 6.20) PIN 1 ID 1 0.017 - 0.027 (0.43 - 0.69) (4 PLACES) 0.050 BSC (1.27 BSC) 0.059 - 0.069 (1.49 - 1.75) 0º - 8º 0.055 - 0.061 (1.40 - 1.55) 0.012 - 0.020 (0.30 - 0.51) SEATING PLANE 0.004 - 0.010 (0.10 - 0.26) 0.015 - 0.035 (0.38 - 0.89) 0.006 - 0.010 (0.15 - 0.26) Package: P14 14-Pin PDIP 0.740 - 0.760 (18.79 - 19.31) 14 0.240 - 0.260 0.295 - 0.325 (6.09 - 6.61) (7.49 - 8.25) PIN 1 ID 0.070 MIN (1.77 MIN) (4 PLACES) 1 0.050 - 0.065 (1.27 - 1.65) 0.100 BSC (2.54 BSC) 0.015 MIN (0.38 MIN) 0.170 MAX (4.32 MAX) 0.125 MIN (3.18 MIN) 14 0.016 - 0.022 (0.40 - 0.56) SEATING PLANE 0º - 15º 0.008 - 0.012 (0.20 - 0.31) ML4836 ORDERING INFORMATION © Micro Linear 1999. PART NUMBER TEMPERATURE RANGE PACKAGE ML4836CP (End Of Life) ML4836CS (End Of Life) 0°C to 70°C 0°C to 70°C 14-Pin DIP (P14) 14-Pin SOIC (S14) is a registered trademark of Micro Linear Corporation. All other trademarks are the property of their respective owners. Products described herein may be covered by one or more of the following U.S. patents: 4,897,611; 4,964,026; 5,027,116; 5,281,862; 5,283,483; 5,418,502; 5,508,570; 5,510,727; 5,523,940; 5,546,017; 5,559,470; 5,565,761; 5,592,128; 5,594,376; 5,652,479; 5,661,427; 5,663,874; 5,672,959; 5,689,167; 5,714,897; 5,717,798; 5,742,151; 5,747,977; 5,754,012; 5,757,174; 5,767,653; 5,777,514; 5,793,168; 5,798,635; 5,804,950; 5,808,455; 5,811,999; 5,818,207; 5,818,669; 5,825,165; 5,825,223; 5,838,723; 5.844,378; 5,844,941. Japan: 2,598,946; 2,619,299; 2,704,176; 2,821,714. Other patents are pending. Micro Linear reserves the right to make changes to any product herein to improve reliability, function or design. Micro Linear does not assume any liability arising out of the application or use of any product described herein, neither does it convey any license under its patent right nor the rights of others. The circuits contained in this data sheet are offered as possible applications only. Micro Linear makes no warranties or representations as to whether the illustrated circuits infringe any intellectual property rights of others, and will accept no responsibility or liability for use of any application herein. The customer is urged to consult with appropriate legal counsel before deciding on a particular application. DS4836-01 2092 Concourse Drive San Jose, CA 95131 Tel: (408) 433-5200 Fax: (408) 432-0295 www.microlinear.com 15