MAX8798

The MAX8798 includes a high-performance, step-up regulator; a high-speed operational amplifier; a digitally adjustable VCOM calibration device with nonvolatile memory; an I2C interface; and a high-voltage, level-shifting scan driver. The MAX8798 is optimized for thin-film transistor (TFT) liquid-crystal display (LCD) applications.

Features of the MAX8798 are:(1)1.8V to 5.5V IN supply voltage range; (2)1.8V to 4.0V VDD input voltage range; (3)1.2MHz current-mode step-up regulator; (4)high-speed (20MHz) operational amplifier ±150mA output current; (5)high-voltage drivers with scan logic; (6)thermal-overload protection.The step-up DC-DC converter provides the regulated supply voltage for panel source driver ICs. The high switching frequency allows the use of ultra-small inductors and ceramic capacitors. The current-mode control architecture of MAX8798 provides fast transient response to pulsed loads typical of source driver loads. The step-up regulator features soft-start and current limit.

The absolute maximum ratings of the MAX8798 can be summarized as:(1)operating temp:-40 to 85;(2)storage temperature range:-65 to +150;(3)junction temperature range:150;(4)GON to AGND:-0.3V to +50V;(5)BOOST to BGND:-0.3V to +20V;(6)LX, PGND RMS current rating:2.4A.Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied.Exposure to absolute maximum rating conditions for extended periods may affect device reliability.The undervoltage lockout (UVLO) circuit compares the input voltage at IN with the UVLO threshold (1.3V rising and 1.2V falling) to ensure that the input voltage is high enough for reliable operation. The 100mV (typ) hysteresis of MAX8798 prevents supply transients from causing a restart. Once the input voltage exceeds the UVLO rising threshold, startup begins. When the input voltage falls below the UVLO falling threshold, the controller MAX8798 turns off the main step-up regulator and the linear regulator,disables the switch-control block, and the operational amplifier output becomes high impedance.