LM2648

LM2648 Two-Phase, Synchronous Step-Down 3-Channel Switching Regulator Controller December 2004 LM2648 Two-Phase, Synchronous Step-Down 3-Channel Switching Regulator Controller General Description The LM2648 consists of two current mode and two voltage mode synchronous buck regulator controllers providing 3 outputs at a switching frequency of 300kHz. Each pair of switching regulator controllers operate 180˚ out of phase. This feature reduces the input ripple RMS current, thereby significantly reducing the required input capacitance. The two current mode regulator outputs operate as a dualphase, single output regulator for high current applications. Current-mode feedback control on Channel 3 assures superior line and load regulation and wide loop bandwidth assures excellent response to fast load transients. Channels 1 and 2 employ voltage-mode feedback control. The LM2648 features analog soft-start circuitry that is independent of the output load and output capacitance. This makes the soft-start behavior more predictable than traditional soft-start circuits. Sequential startup is built in and requires a single capacitor to set the timing. The LM2648 has over-voltage protection and under-voltage protection for all outputs. Two additional comparator inputs (analog and logic level) are provided to shut down the IC for any user defined protection. The FAULT_DELAY pin allows delayed shut off time for the IC during an under-voltage or PROT-IN2 fault. The LM2648 also features an adj...