Micro Linear Corporation ML4832CP, ML4832CS Datasheet

July 2000

PRELIMINARY

ML4832*

Electronic Dimming Ballast Controller

GENERAL DESCRIPTION

The ML4832 is a complete solution for a dimmable/non­dimmable, high power factor, high efficiency electronic
ballast. The BiCMOS ML4832 contains controllers for
“boost” type power factor correction as well as for a
dimming ballast.

The power factor circuit uses the average current sensing
method with a gain modulator and overvoltage protection.
This system produces a power factor of better than 0.99
with low input current THD at > 95% efficiency. Special
care has been taken in the design of the ML4832 to
increase system noise immunity by using a high amplitude
oscillator, and a current-fed multiplier. An overvoltage
protection comparator inhibits the PFC section in the
event of a lamp out or lamp failure condition.

The ballast section provides for programmable starting
scenarios with programmable preheat and lamp out-of­socket interrupt times. The IC controls lamp output through
frequency modulation using lamp current feedback.

FEATURES

■ Complete power factor correction and dimming

ballast control in one IC

■ Low distortion, high efficiency continuous boost,

average 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

■ Over-temperature shutdown replaces external

heat sensor for safety

■ PFC overvoltage comparator eliminates output

“runaway” due to load removal

■ Large oscillator amplitude and gain modulator

improves noise immunity

■ Low start-up current <0.5mA

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

BLOCK DIAGRAM

R

SET

7

R

T/CT

8

R

X/CX

10

IA OUT

2

IA+

4

I

SINE

3

EA OUT

1

EA–/OVP

18

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

V

V

REF

GND

9

5

6

14

13

15

12

CC

16

17

11

1

ML4832

PIN CONFIGURATION

ML4832

18-Pin SOIC (S18)

1
2
3
4
5
6
7
8
9

TOP VIEW

EA OUT

IA OUT

I

SINE

IA+
LAMP FB
LFB OUT

R

SET

RT/C

INTERRUPT

ML4832

18-Pin DIP (P18)

1

2

3

4

5

6

7

8

T

9

TOP VIEW

18

EA–/OVP

17

V

REF

V

16

CC

PFC OUT

15

OUT A

14

OUT B

13

P GND

12

GND

11

R

10

X/CX

EA OUT
IA OUT

I

SINE

IA+
LAMP FB
LFB OUT

R

SET

RT/C

INTERRUPT

T

PIN DESCRIPTION

PIN# NAME FUNCTION PIN# NAME FUNCTION

1 EA OUT PFC error amplifier output and

compensation node

2 IA OUT Output and compensation node of the

PFC average current transconductance
amplifier

3I

SINE

PFC gain modulator input

9 INTERRUPT Input used for lamp-out detection

and restart. A voltage greater than

7.5 volts resets the chip and
causes a restart after a
programmable interval.

10 RX/C

X

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

18
17
16
15
14
13
12
11
10

EA–/OVP
V

REF

V

CC

PFC OUT
OUT A
OUT B
P GND
GND
R

X/CX

4 IA+ Non-inverting input of the PFC average

current transconductance amplifier
and peak current sense point of the
PFC cycle by cycle current limit
comparator

5 LAMP FB Inverting input of an error amplifier

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

6 LFB OUT Output from the lamp current error

transconductance amplifier used for
lamp current loop compensation

7R

SET

8RT/C

T

External resistor which sets oscillator
F

, and RX/CX charging current

MAX

Oscillator timing components

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 V

17 V

CC

REF

Positive supply for the IC

Buffered output for the 7.5V
voltage reference

18 EA–/OVP Inverting input to PFC error

amplifier and OVP comparator
input

2

ABSOLUTE MAXIMUM RATINGS

ML4832

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.

Maximum Forced Voltage

(IA OUT)................................................. –0.3V to 7.5V

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

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

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

Supply Current (ICC) ............................................... 60mA

Output Current, Source or Sink (OUT A, OUT B, PFC
OUT)

Thermal Resistance (qJA)

Plastic PDIP ..................................................... 70°C/W

Plastic SOIC................................................... 100°C/W

DC ................................................................... 250mA

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

Gain Modulator I

Input .....................................10mA

SINE

Analog Inputs ....................................... –0.3V to VCC –2V

IA+ Input Voltage.............................................. –3V to 2V

OPERATING CONDITIONS

Temperature Range

ML4832C ..................................................0°C to 85°C

Maximum Forced Voltage

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

Maximum Forced Current

(EA OUT, IA OUT, LFB OUT) ............................±20mA

ELECTRICAL CHARACTERISTICS

Unless otherwise specified, R
TA = Operating Temperature Range (Note 1)

PARAMETER CONDITIONS MIN TYP MAX UNITS

PFC CURRENT SENSE AMPLIFIER

Small Signal Transconductance 40 90 120 µ

= 22.1kW, RT = 15.8kW, CT = 1.5nF, C(VCC) = 1µF, I

SET

= 200µA, VCC = 12.5V,

SINE

W

Output Low I

Output High I

Source Current I

Sink Current I

PFC VOLTAGE FEEDBACK AMPLIFIER/LAMP CURRENT AMPLIFIER

Input Bias Current –0.3 –1.0 µA

Small Signal Transconductance 30 55 90 µ

Input Voltage Range –0.3 5.0 V

Output Low V

Output High V

Source Current V

= 0mA, V

SINE

V

= –0.3V, RL = ¥ 0.2 0.4 V

IA+

= 1.5mA, 6.3 6.8 V

SINE

V

SINE

V
V

SINE

V
V
TJ = 25ºC 0.03 0.07 0.16 mA

V
TJ = 25ºC

= V

EA–/OVP

= 1.5mA, –0.05 –0.15 –0.25 mA

EA–/OVP
IA OUT

= 0mA, V
= –0.6V

IA+
EA OUT

LAMP FB

LAMP FB

LAMP FB
EA OUT

IA+

= V

IA+

= 6V, TJ = 25ºC

= 0V, V

= V

EA–/OVP

= V

EA–/OVP

= V

EA–/OVP

= V

LFB OUT

= 0V,

EA OUT

= 0V, RL = ¥

= 0V,

= 0.3V,

IA OUT

= 5V,

EA–/OVP

= 3V, RL = ¥ 0.2 0.4 V

= 2V, RL = ¥ 7.1 7.5 7.8 V

= 0V, –0.06 –0.15 –0.30 mA

= 7V,

W

Sink Current V

LAMP FB

V

EA OUT

TJ = 25ºC

= V

= V

EA–/OVP

LFB OUT

= 5V, 0.06 0.12 0.28 mA

= 0.3V,

3

ML4832

ELECTRICAL CHARACTERISTICS (Continued)

PARAMETER CONDITIONS MIN TYP MAX UNITS

GAIN MODULATOR

Output Voltage (V

Output Voltage Limit I

Offset Voltage I

I

Input Voltage I

SINE

)I

MUL

= 100µA, V

SINE

I

= 300µA, V

SINE

I

=100µA, V

SINE

I

= 300µA, V

SINE

= 1.5mA, V

SINE

= 0µA, V

SINE

I

= 150µA, V

SINE

= 200µA 0.8 1.4 1.8 V

SINE

EA–/OVP

= 3V 85 mV

EA OUT

= 3V 260 mV

EA OUT

= 6V 200 mV

EA OUT

= 6V 600 mV

EA OUT

= 0V 0.9 1 1.1 V

EA–/OVP

= 0V 15 mV

= 3V 15 mV

EA–/OVP

PFC CURRENT — LIMIT COMPARATOR

Current-Limit Threshold –0.85 –1.0 –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

– 4.0V < VCC < V

CCZ

– 0.5V 1 %

CCZ

Temperature Stability 2%

Total Variation Line, temperature 69 83 kHz

Ramp Valley to Peak 2.5 V

C

Charging Current V

T

V

V

= 3V, V

LAMP FB

= 0.9V (Preheat) –90 –113 –130 µA

RX/CX

= 3V, V

LAMP FB

RT/CT

RT/CT

= 2.5V,

= 2.5V,

RX/CX = Open –180 –230 –260 µA

CT Discharge Current V

= 2.5V 4.0 5.5 7.0 mA

RT/CT

Output Drive Deadtime 0.64 0.91 1.30 µs

REFERENCE SECTION

Output Voltage TA = 25°C, IO = 1mA 7.4 7.5 7.6 V

Line regulation V

– 4.0V < VCC < V

CCZ

– 0.5V 8 25 mV

CCZ

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 = 680KW, 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

Pin 10 Charging Current –24 –28 –33 µA

4

ML4832

ELECTRICAL CHARACTERISTICS (Continued)

PARAMETER CONDITIONS MIN TYP MAX UNITS

PREHEAT AND INTERRUPT TIMER (RX = 680KW, CX = 4.7µF) CONTINUIED

Pin 10 Open Circuit Voltage VCC < Start-up threshold 0.4 0.7 1.0 V

Pin 10 Maximum Voltage 7.0 7.3 7.7 V

Input Bias Current V

= 1.2V 0.1 µA

RX/CX

Preheat Lower Threshold 1.05 1.22 1.36 V

Preheat Upper Threshold 4.4 4.77 5.15 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 Threshold 7.15 7.4 7.65 V

Input Bias Current 0.1 µA

R

Voltage 2.4 2.5 2.6 V

SET

OVP COMPARATOR

OVP Threshold 2.65 2.75 2.85 V

Hysteresis 0.20 0.25 0.27 V

Propagation Delay 1.4 µs

OUTPUTS

Output Voltage Low I

Output Voltage High I

Output Voltage Low in UVLO I

= 20mA 0.1 0.2 V

OUT

I

= 200mA 1.0 2.0 V

OUT

= –20mA V

OUT

I

= –200mA V

OUT

= 10mA, VCC 8V 0.2 V

OUT

– 0.2 VCC – 0.1 V

CC

– 2.0 VCC – 1.0 V

CC

Output Rise/Fall Time CL = 1000pF 20 ns

UNDER-VOLTAGE LOCKOUT AND BIAS CIRCUITS

IC Shunt Voltage (V

)I

CCZ

= 15mA 14.2 15.0 15.8 V

CC

Start-up Current VCC = Start-up threshold –0.2V 0.34 0.48 mA

Operating Current VCC = 12.5V, V

EA–/OVP

= V

V

= 0V, 5.5 8.0 mA

IA+

= 2.3V,

LAMP FB

IA OUT = open
RT = 16.2kW, R

= 22.1kW

SET

VCC = 12.5V, CL = 0

Start-up Threshold V

Shutdown Threshold V

– 1.2 V

CC

– 5.5 V

CC

– 1.0 VCC – 0.8 V

CCZ

– 5.0 VCC – 4.5 V

CCZ

Shutdown Temperature (TJ) 120 °C

Hysteresis (TJ) 30 °C

Note 1: Limits are guaranteed by 100% testing, sampling or correlation with worst case test conditions.

5