IL9961 datasheet(10/12 Pages) IKSEMICON

10 / 12 page

IL9961

2013 December, Ver. 00

Input voltage control

Supply for driver IL9961 may be realized directly from mains of voltage of direct current

8.0~450 V through pin VIN. When this voltage supplied on pin VIN integrated circuit forms direct

voltage 7.5 V on pin VDD. To pin VDD there should be connected capacitor with small equivalent se-

ries resistance (ESR), in order to provide low resistance of bus for pulses of large current through

GATE pin during integrated circuit operation. IC IL9961 also can be supplied directly through VDD

pin with voltage larger than internally-regulated 7.5 V, but less than 12 V.

Direct voltage supplied on VIN pin, is limited by dissipated power in the package. For exam-

ple, in eight pin SO package at consumption in operating mode of current IIN = 2.5 mA through VIN

pin, maximum direct voltage on VIN pin is calculated by formula (1)





347











(1)

where Tj = 150 – maximum operating temperature of chip,

OC;

Ta = 25 - ambient temperature,

0C;

Rθ, ja = 148 - thermal resistance of chip - ambient,

OC / Watt.

In cases when integrated circuit should operate at higher voltage, sequentially to VIN pin

can be connect resistor or Zener diode for removal of dissipated power from IC. In mentioned ex-

ample, use of 100 V Zener diode allows the scheme to operate up to 447 V. Input current, con-

sumed by integrated circuit through VIN pin is calculated by formula (2)

мА





 0

(2)

where QG - capacity of gate of exterior transistor (from producer specification), pF;

fs - switching frequency, Hz.

LEDs Dimming Control

The LEDs dimming control may be performed by two means, separately or in combination,

depending on the application circuit. The LEDs dimming may be controlled either by means of the

linear alteration of the current value via LEDs, or by switching on / off this current at its constant

value. The second adjustment method (the so called MWM-attenuation) is based on LEDs dim-

ming by means of altering the fill-up ratio of the output current pulses.

The linear adjustment of LEDs dimming (linear attenuation) is performed by means of ap-

plying the voltage with the value from 0 to 1.5 V at the input LD. In this case the actuation thresh-

old of the comparator, controlling the voltage at the pin CS, is preset equal to the value: VLD·0.18. It

is in this way, that adjustment of the output current value takes place. The value of the controlled

voltage at the pin CS can be altered by means of the variable resistor, included into the lower

shoulder of the resistive voltage divider of the low voltage part of the circuit VDD and connected to

the pin LD. Application of the voltage over 1.5 V at the input LD does not result in increase of the

preset mean value of the output current. In order to obtain the current of the greater value it is nec-

essary to select the reading resistor with the smaller nominal resistance.

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