Integrated Backlight Controllers Optimized to Drive CCFLs Using a Resonant Full-Bridge Inverter Architecture
| Status |
| Active: In Production. |
| Description |
The MAX8709B integrated backlight controller is optimized to drive cold-cathode fluorescent lamps (CCFLs) using a resonant full-bridge inverter architecture. The resonant operation maximizes striking capability and provides near-sinusoidal waveforms over the entire input range to improve CCFL lifetime. The controller operates over a wide input voltage range of 4.6V to 28V with high power-to-light efficiency. The device also includes safety features that effectively protect against many single-point fault conditions including lamp-out and short-circuit faults.
The MAX8709B achieves 10:1 dimming range by “chopping” the lamp current on and off using a digital pulse-width-modulation (DPWM) method. The minimum DPWM duty cycle of the MAX8709B is 12.5%. The brightness is controlled with a 2-wire SMBus™-compatible interface. The device directly drives the four external N-channel power MOSFETs of the full-bridge inverter. An internal 5.3V linear regulator powers the MOSFET drivers, the DPWM oscillator, and most of the internal circuitry. The MAX8709B is available in a space-saving 28-pin thin QFN package and operates over a -40°C to +85°C temperature range. |
An evaluation kit is available: MAX8709EVCMOD2, MAX8709EVKIT
| Key Features |
|
Applications/Uses |
- Synchronized to Resonant Frequency
- Longer Lamp Life
- Guaranteed Striking Capability
- High Power-to-Light Efficiency
- Wide Input Voltage Range (4.6V to 28V)
- Feed Forward for Excellent Line Rejection
- SMBus Dimming Control Interface
- 10:1 Dimming Range
- Guaranteed 200Hz to 220Hz DPWM Frequency
- Secondary Voltage Limit Reduces Transformer Stress
- Adjustable Lamp-Out Protection with 1s Timer
- Secondary Current Limit Protects Against High-Voltage Short Circuits to Ground
- Small, 5mm x 5mm, Thin QFN Package
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| Key Specifications: CCFL Controllers |
| Part Number |
Features |
VIN
(V) |
VIN
(V) |
Topology |
Channels |
Dimming Interface |
Freq. |
EV Kit |
Package/Pins |
Smallest Available Pckg.
(mm2) |
Oper. Temp.
(°C) |
| min |
max |
max w/pins |
| MAX8709B |
| All N-FET Drive |
| Lamp Fault Output |
| Status Registers | |
4.6 |
28 |
Full-Bridge |
1 |
|
Resonant |
No |
|
26 |
-40 to +85 |
| See All CCFL Controllers (17) |
| Diagram |
Typical Operating Circuit |
source：ShenZhen henlito electronic co.,ltd.
web:www.henlito.com
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