ADP3153

The ADP3152/3 is a highly efficient synchronous rectified controller optimized for Pentium Pro and Pentium II Processor applications where 5V is stepped down to a digitally controlled output voltage between 1.8V and 3.5V. It uses a 5-Bit DAC to read a voltage identification (VID) code directly from the processor. The ADP3152/3 uses a current mode constant off-time architecture to generate a precise output voltage and maintain a constant inductor ripple current while providing excellent line and load transient response. It drives two synchronous N-channel MOSFETS at a switching frequency of 250kHz. The operating current level is user programmable via an external current sense resistor. Included in the ADP3153 is an integrated LDO controller.

The ADP3152/3 also comes with an added feature of an over-voltage protection crowbar. This feature use an N-channel MOSFET as the synchronous switch to provide the ability to crowbar the output wit the same MOSFET. In the event that the upper MOSFET shorts out and the output voltage exceeds 15% of the desired regulation level, the ADP3152/3 will turn on the lower MOSFET, which will current-limit the source power supply or blow its fuse. More importantly, this will pull down the output voltage, and thus, save the expensive microprocessor from destruction.