Electronic Design

High-Current Quad Output Regulator Protects Large TFT Panels

Optimal protection for large thin-film-transistor (TFT) flat-panel displays (FPDs), 22 in. in diameter and larger, is now a possibility with the LT1493. Linear Technology's high-current quad output adjustable switching regulator features an input range of 4.5 to 22 V, delivering independent outputs for VLOGIC, ADD, VON, and VOFF signals as required by TFT FPDs. The IC contains a 2.4-V buck regulator to power VLOGIC, a 2.6-A boost regulator to drive the TFTs, a high-voltage TFT biasing output, and a 0.4-A inverter for negative TFT biasing.

The LT1493 operates at 1.2 MHz. A Panel Protect feature disables the VON signal if any of the four outputs are more than 10% below the normal reset output-voltage level. This prevents the TFT panel from being exposed to an onrush of VON current that would essentially "flash light" and damage the entire FPD. A high-side pnp transistor provides a delayed turn-on of the VON signal, which has up to 30 mA of bias current, to ensure that it comes on only after all the other outputs are powered up.

A PGOOD output signal drives an optional PMOS pass device to provide an output disconnect for the ADD output. A soft-start feature is also available for all channels.

Housed in a thermally enhanced TSSOP-28 package, the IC costs $4.75 each in 1000-unit quantities.

Linear Technology Corp.
(408) 432-1900

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