AT1621 Single PWM and Triple Linear Power Controller Features General Description Provides 4 Regulated Voltages -CPU Core, AGP Bus, Memory, and GTL Bus Power Drives two N-channel MOSFETs Linear Regulator Drives Compatible with both MOSFET and Bipolar Series Pass Transistors Operates from +5V and +12V input Fixed or Externally Resistor-Adjustable Linear Outputs Simple Single-Loop Control -Voltage-mode PWM control Fast Transient Response - High-bandwidth error amplifier - Full 0% to 100% duty ratio Excellent Output Voltage Regulation -Core PWM Output: 1% Over Temperature -Other Outputs: 3% Over Temperature TTL-compatible 5 bit digital-to-analog output voltage selection - Wide range 1.3VDc to 3.5VDC - 0.1V binary steps from 2.1VDC to 3.5VDC - 0.05V binary steps from 1.3VDC to 2.05VDC Power-Good Output Voltage Monitor Over-Voltage and Over-Current Fault Monitors -Does not require extra current sensing element Small converter size -Constant Frequency Operation -200 kHz Free-Running Oscillator Programmable From 50 kHz to Over 1 MHz The AT1621 provides complete control and protection for four voltages in high-performance, graphics intensive computer applications. It integrates a PWM controller and three linear controllers into a 28-pin SOIC package. One PWM controller regulates the CPU core voltage with a synchronous-rectified buck topology. The linear controllers regulate the computer system's AGP 1.5V or 3.3V bus power, the 1.5V GTL bus power, and the 1.8V power for the North/South Bridge core voltage and/or cache memory circuits. Applications Motherboard Power Regulation for Computers Low-Voltage Distributed Power Supplies The AT1621 includes a fully-TTL compatible 5-bit digital-to-analog converter (DAC) that adjusts the output voltage from 2.1VDC to 3.5VDC in 0.1V increments and from 1.3VDC to 2.1VDC in 0.05V steps. The precision reference and voltage-mode regulator hold the selected output voltage to within 1% over temperature. The AGP bus power linear controller's output is user-selectable, through a TTL-compatible signal applied at the SELECT pin, for levels of 1.5V or 3.3V with 3% accuracy. Based on the status of the FIX pin, the other two linear regulators provide either fixed output voltages of 1.5V 3% and 1.8V 3%, or useradjustable by means of an external resistor divider. All linear controllers can employ either N-channel MOSFETs or bipolar NPNs for the pass transistor. The AT1621 monitors all the output voltage. A single is issued when the core is within 10% of the DAC setting and all other outputs are above their under-voltage levels. Additional built-in overvoltage protection for the core output uses the lower MOSFET to prevent output voltage above 115% of the DAC setting. The PWM controllers' overcurrent function monitors the output current by using the rDS(on) of the upper MOSFET, which eliminates the need for a current sensing resistor. 2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 WWW: http://www.aimtron.com.tw Fax: 886-3-563-0879 Email: service@aimtron.com.tw Preview the document, detail datasheet contact to our service department. AT1621 Single PWM and Triple Linear Power Controller Block Diagram 2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 WWW: http://www.aimtron.com.tw Fax: 886-3-563-0879 Email: service@aimtron.com.tw Preview the document, detail datasheet contact to our service department.