ML4836CS View Datasheet(PDF) - Micro Linear Corporation

Part Name

Description

Manufacturer

ML4836CS

Compact Fluorescent Electronic Dimming Ballast Controller

Micro Linear Corporation 

FUNCTIONAL DESCRIPTION (Continued)

FOSC

=

1

t CHG +

t DIS

(3)

and

  t CHG = RTCT In

VREF + ICHG ´ RT - VTL

VREF + IICHG ´ RT - VTH

(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:

2 7 FSTART = 0.54 ×

1

RT RT2

× CT

(5a)

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:

1. The output of the preheat timer

ML4836

2. The voltage at LFB OUT (lamp feedback amplifier

output)

In preheat condition, charging current is fixed at

ICHG(PREHEAT)

=

2.5

R SET

(6)

In running mode, charging current decreases as the

voltage rises from 0V to VOH at the LAMP FB amplifier.

The charging current behavior can be expressed as:

ICHG

= 5V

R SET

-

LEAO

8k ± 25%

(7)

The highest frequency is attained when ICHG is highest,

which is attained when voltage at LFB OUT is at 0V:

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)

ICC

t

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

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