Simple Dimming Ballast Control IC
www.fairchildsemi.com
KA7540
Simple Dimming Ballast Control IC
Features
• • • • • • • • Internal soft start No lamp pr...
Description
www.fairchildsemi.com
KA7540
Simple Dimming Ballast Control IC
Features
Internal soft start No lamp protection Voltage controlled dimming Trimmed 1.5% internal bandgap reference Under voltage lock out with 1.8V of hysteresis Totem pole output with high state clamp Low start-up and operating current 8-pin DIP & 8-pin SOP
Descriptions
The KA7540 provides simple and high performance electronic ballast control functions. KA7540 is optimized for electronic ballast requiring a minimum board area, reduced component count and low power dissipation. Internal soft start circuitry eliminates the need for an external soft start PTC resistor. Voltage controlled dimming circuit is built into the IC to control the lighting output in a wide range. Protection circuitry has also been added to prevent switches from burning out in no lamp condition. Output gate drive circuit clamps power MOSFET gate voltage irrespective of supply voltage.
8-DIP
Applications
Electronic Ballast Lighting Control System Half-bridge Drive Control System
1
8-SOP
1
Rev. 1.0.1
©2001 Fairchild Semiconductor Corporation
KA7540
Internal Block Diagram
UVLO 2V Ref CS 6.8µF 1 25µA VZ Vref − + 17µA VZ IS UVLO Internal bias 1.8V + − 12.5V 8 VCC
Oscillator Ct 180pF 8Ict 2
Ict latch + Q
+ +
IC 7 OUT 1
F.D from VCS
Vdim
3 80kΩ Vd 20kΩ 100µA 3pF
VCC Id + − kVref VZ Frequency divider
6
OUT 2
Ldet
40kΩ 4 5pF 2V
25µA − + Shut down signal IS = 17µA × (Vref − VSS) / Vref Id = 25µA × (Vref − ...
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