Micro Linear Corporation ML4833CS, ML4833CP Datasheet

July 2000

PRELIMINARY

ML4833*

Electronic Dimming Ballast Controller

GENERAL DESCRIPTION

The ML4833 is a complete solution for a dimmable or a non-dimmable, high power factor, high efficiency electronic ballast. The BiCMOS ML4833 contains controllers for “boost” type power factor correction as well as for a dimming ballast. The ML4833 was designed to minimize the number of external components required to build an electronic ballast.

The PFC circuit uses a new, simple PFC topology which requires only one loop for compensation. This system produces a power factor of better than 0.99 with low input current THD. An overvoltage protection comparator inhibits the PFC section in the event of a lamp out or lamp failure condition.

The ballast controller section provides for programmable starting sequence with individually adjustable preheat and lamp out-of-socket interrupt times. The IC controls lamp output power through feedback. The ML4833 provides a power down input which reduces power to the lamp, for GFI, end of life, etc.

BLOCK DIAGRAM

FEATURES

■ Complete power factor correction and dimming

ballast control in one IC

■ Low distortion, high efficiency continuous boost,

peak current sensing PFC section

■ Programmable start scenario for rapid or

instant start lamps

■ Lamp current feedback for dimming control

■ Variable frequency dimming and starting

■ Programmable restart for lamp out condition to

reduce ballast heating

■ Internal over-temperature shutdown replaces

external heat sensor

■ PFC overvoltage comparator eliminates output

“runaway” due to load removal

■ Low start-up current <0.5mA

■ Power reduction pin for end of life and GFI detectors

(* Indicates part is End Of Life as of July 1, 2000)

SET

/CT

X/CX

PDWN

RAMP

PIFB

PEAO

PVFB/OVP

VARIABLE FREQUENCY

OSCILLATOR

PRE-HEAT

AND INTERRUPT

TIMERS

POWER FACTOR

CONTROLLER

CONTROL

GATING LOGIC

UNDER-VOLTAGE

AND THERMAL

SHUTDOWN

OUTPUT DRIVERS

INTERRUPT

LAMP FB

LFB OUT

OUT A

OUT B

PFC OUT

PGND

VCC

REF

GND

ML4833

PIN CONFIGURATION

PEAO

PIFB

PDWN

LAMP FB

LFB OUT

SET

RT/C

INTERRUPT

X/CX

ML4833

18-Pin DIP (P18)

TOP VIEW

PVFB/OVP V

REF

VCC PFC OUT OUT A OUT B P GND GND C

RAMP

PEAO

PIFB

PDWN LAMP FB LFB OUT

SET

RT/C

INTERRUPT

X/CX

ML4833

18-Pin SOIC (S18)

1 2 3 4 5 6 7 8 9

TOP VIEW

PIN DESCRIPTION

PIN# NAME FUNCTION PIN# NAME FUNCTION

1 PEAO PFC error amplifier output and

compensation node.

2 PIFB Sensing of the inductor current and

peak current sense point of the PFC cycle by cycle current limit comparator.

3 PDWN A one volt comparator threshold that

switches the operating frequency to the preheat frequency when exceeded.

4 LAMP FB Inverting input of an error amplifier

used to sense (and regulate) lamp arc current. Also the input node for dimming control.

5 LFB OUT Output of the lamp current error

transconductance amplifier used for lamp current loop compensation.

SET

7RT/C

External resistor which sets oscillator F

, and R(X)/C(X) charging current.

MAX

Oscillator timing components.

8 INTERRUPT Input used for lamp-out detection and

restart. A voltage less than 1.25 volts resets the chip and causes a restart after a programmable interval.

9RX/C

Sets the timing for the preheat, dimming lockout, and interrupt.

10 C

RAMP

Integrated voltage of the error amp out.

11 GND Ground. 12 P GND Power ground for the IC. 13 OUT B Ballast MOSFET drive output. 14 OUT A Ballast MOSFET drive output. 15 PFC OUT Power Factor MOSFET drive output. 16 VCC Positive supply for the IC. 17 V

REF

Buffered output for the 7.5V voltage reference.

18 PVFB/OVP Inverting input to PFC error amplifier

and OVP comparator input.

18 17 16 15 14 13 12 11 10

PVFB/OVP V

REF

VCC PFC OUT OUT A OUT B P GND GND C

RAMP

ML4833

ABSOLUTE MAXIMUM RATINGS

Maximum Forced Voltage

(PEAO, LFB OUT) ...................................–0.3V to 7.7V

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) ............................................... 60mA

Output Current, Source or Sink

(OUT A, OUT B, PFC OUT) DC ......................... 250mA

Maximum Forced Current (PEAO, LFB OUT) ........ ±20mA

Junction Temperature ............................................ 150°C

Storage Temperature Range ..................... –65°C to 150°C

Lead Temperature (Soldering 10 sec.) .................... 260°C

Thermal Resistance (qJA)

ML4833CP ...................................................... 70°C/W

ML4833CS .................................................... 100°C/W

Output Energy (capacitive load per cycle).............. 1.5 mJ

Analog Inputs

OPERATING CONDITIONS

(LAMP FB, INTERRUPT, VCC) ........... –0.3V to VCC –2V

PIFB input voltage .........................................–1.5V to 2V

Temperature Range ........................................0°C to 85°C

ELECTRICAL CHARACTERISTICS

Unless otherwise specified, R

PARAMETER CONDITIONS MIN TYP MAX UNITS

Lamp Current Amplifier (LAMP FB, LFB OUT)

Input Bias Current –0.3 –1.0 µA Small Signal Transconductance 35 65 105 µW Input Voltage Range –0.3 5.0 V Output Low Voltage at LAMP FB = 3V, RL =  0.2 0.4 V Output High Voltage at LAMP FB = 2V, RL =  7.1 7.5 7.8 V Source Current Voltage at LAMP FB = 0V,

Sink Current Voltage at LAMP FB = 5V,

PFC Voltage Feedback Amplifier (PEAO, PVFB/OVP)

Input Bias Current –0.3 –1.0 µA Small Signal Transconductance 35 65 105 µW Input Voltage Range –0.3 5.0 V Output Low Voltage at PVFB = 3V, RL =  0.2 0.4 V Output High Voltage at PVFB = 2V, RL =  6.5 6.8 7.1 V Source Current Voltage at PVFB/OVP = 0V,

Sink Current Voltage at PVFB/OVP = 3V,

PFC Current — Limit Comparator (PIFB)

Current-Limit Threshold –0.90 –1.05 –1.15 V Propagation Delay 100mV step and 100mV overdrive 100 ns

Oscillator

Initial Accuracy TA = 25°C 72 76 80 kHz Voltage Stability V Temperature Stability 2% Total Variation Line, temperature 69 83 kHz Ramp Valley to Peak 2.5 V

= 22.1ký, RT = 15.8kW, CT = 1.5nF, C

SET

LFB OUT = 7V, TA = 25°C –0.05 –0.15 –0.25 mA

LFB OUT = 0.3V, TA = 25°C 0.05 0.12 0.22 mA

PEAO = 6V, TA = 25°C –0.05 –0.15 –0.25 mA

PEAO = 0.3V, TA = 25°C 0.03 0.07 0.16 mA

– 4.5V < VCC <V

CCZ

= 1µF, VCC = 12.5V. (Note 1)

VCC

– 0.5V 1 %

CCZ

ML4833

ELECTRICAL CHARACTERISTICS (Continued)

PARAMETER CONDITIONS MIN TYP MAX UNITS

Oscillator (Continued)

Charging Current Voltage at LAMP FB = 3V,

CT Discharge Current Voltage at RT/CT = 2.5V 4.0 5.5 7.0 mA Output Drive Deadtime 0.65 1 1.35 µs

Reference Section

Output Voltage TA = 25°C, IO = 1mA 7.4 7.5 7.6 V Line regulation V Load regulation 1mA < IO < 5mA 2 15 mV Temperature stability 0.4 % Total Variation Line, load, temp 7.35 7.65 V Output Noise Voltage 10Hz to 10kHz 50 µV Long Term Stability TJ = 125°C, 1000 hrs 5 mV

Preheat and Interrupt Timer (RX/CX where RX = 680ký, CX = 4.7µF)

Initial Preheat Period 0.8 s Subsequent Preheat Period 0.7 s Start Period 1.2 s Interrupt Period 5.7 s RX/CX Charging Current –24 –28 –33 µA RX/CX Open Circuit Voltage VCC < Start-up threshold 0.4 0.7 1.0 V RX/CX Maximum Voltage 7.0 7.3 7.7 V Input Bias Current Voltage at C Preheat Lower Threshold 1.05 1.22 1.36 V Preheat Upper Threshold 4.2 4.7 5.1 V Interrupt Recovery Threshold 1.05 1.22 1.36 V Start Period End Threshold 6.05 6.6 7.35 V

Interrupt Input (INTERRUPT)

Interrupt Threshold 1.1 1.22 1.4 V Input Bias Current 0.1 µA R

Voltage 2.4 2.5 2.6 V

SET

OVP Comparator (PVFB/OVP)

OVP Threshold 2.63 2.73 2.83 V Hysteresis 0.18 0.23 0.27 V Propagation Delay 1.4 µs

RT/CT = 2.5V, RX/CX = 0.9V (Preheat) –90 –110 –130 µA LAMP FB = 3V, R

RX/CX = Open –180 –220 –260 µA

– 4.5V < VCC < V

CCZ

RAMP

= 2.5V,

T/CT

– 0.5V 2 35 mV

CCZ

= 1.2V 0.1 µA

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Micro Linear Corporation ML4833CS, ML4833CP Datasheet

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