Maxim Debuts the MAX1778 and MAX1880 - MAX1885 Series DC/DC Converters
Maxim Integrated Products (Sunnyvale, CA) debuted the MAX1778, and MAX1880 through MAX1885 Series of new multiple-output dc/dc converters. They are designed to provide the regulated voltages required by active-matrix, thin-film transistor, liquid-crystal displays.
The new converters feature one high-power step-up converter and two low-power charge pumps that convert the 2.7V to 5.5V input voltage into three independent output voltages. A built-in linear regulator and VCOM buffer complete the power-supply requirements. The main step-up converter generates an externally set output voltage up to 13V that can supply the display’s row/column drivers. Maxim reports that the converters' high switching frequency and current-mode PWM architecture provide fast transient response and allow the use of small low-profile inductors and ceramic capacitors. The company claims that the BiCMOS control circuitry and internal 14V switch, 0.35 n-channel MOSFET, enable efficiencies up to 91 percent.
The dual low-power charge pumps (MAX1778, MAX1880, MAX1881 and MAX1882 only) independently regulate one positive output (VPOS) and one negative output (VNEG). These low-power outputs use external diode and capacitor stages to regulate output voltages up to +40V and -40V. A control scheme minimizes output ripple as well as capacitor sizes for both charge pumps.
A resistor-programmable, 40mA, low-dropout linear regulator (MAX1778, MAX1881, MAX1883 and MAX1884 only) provides pre-regulation or post-regulation for any of the supplies. The VCOM buffer provides a high current output that is ideal for driving the capacitive backplane of TFT LCD panels. The VCOM buffer’s output voltage is preset with an internal 50-percent resistive-divider that can be externally adjusted for other voltages.
The MAX1778 and MAX1880 - MAX1885 are protected against output under-voltage and thermal overload conditions by a latched fault-detection circuit that shuts down the device. All devices are available in a TSSOP package with a maximum 1.1mm height.
