QUINTUPLE/TRIPLE-OUTPUT TFT LCD POWER SUPPLY FROM MAXIM WITH FAULT PROTECTION AND VCOM BUFFER
SUNNYVALE, CA-October 28, 2002-Maxim Integrated Products
(NASDAQ: MXIM) introduces the MAX1997/MAX1998 power supplies, which provide the voltages required for active-matrix, thin-film transistor, liquid crystal displays (TFT LCD). Both combine a high-performance step-up regulator with two linear-regulator controllers, input protection switch control, and flexible sequence programming. The MAX1997 contains two additional linear-regulator controllers and a VCOM buffer. The MAX1997/MAX1998 operate from 2.7V to 5.5V input supplies and feature multiple levels of protection circuitry, making a complete power supply system for displays.
The main DC-DC converter provides the regulated supply voltage for the display's source-driver ICs. The converter is a high-frequency (up to 1.5MHz) step-up regulator with an integrated 14V N-channel MOSFET that allows the use of ultra-small inductors and ceramic capacitors while achieving efficiencies over 85%. Its current-mode control architecture provides fast transient response to pulsed loads. Internal soft-start and cycle-by-cycle current limit help prevent input surge currents.
The positive and negative linear-regulator controllers post-regulate charge-pump outputs for TFT gate-on and gate-off supplies. Both linear-regulator controllers, as well as the step-up regulator, have supply-sequencing control inputs. The three outputs can be sequenced in any order by selecting the appropriate external components.
The MAX1997 features a high-current backplane driver (VCOM). This buffer provides peak currents exceeding 400mA and requires only a 0.47mF output filter capacitor. The MAX1997's two additional linear-regulator controllers can be used to build the gamma reference voltage and a logic supply.
The MAX1997/MAX1998 have a unique input switch control that can replace the typical input fuse by disconnecting the load from the input supply when a fault is detected. The fault detector monitors all the regulated output voltages as well as the current from the input supply. In addition, the MAX1997/MAX1998 enter shutdown when the internal overtemperature threshold is reached.
The MAX1997 is available in a 32-pin QFN package and the MAX1998 is available in a 20-pin QFN package. Both packages have a maximum 1.0mm thickness suitable for ultra-thin LCD panels. Prices start at $4.07 for the MAX1997 and $3.38 for the MAX1998 (1000-up, FOB USA).
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