Features
| • | Four synchronous buck regulators |
| • | Channel 3: Two-phase, current mode controller |
| • | 4.5V to 18V input range |
| • | Built in sequential startup |
| • | Channels 1 and 2: Independent, 180° out of phase voltage mode controllers |
| • | Single soft start for channels 1 and 2 |
| • | Adjustable cycle-by-cycle current limit for each channel |
| • | Adjustable reference current |
| • | Adjustable input under-voltage lockout |
| • | Output over-voltage latch protection |
| • | Output under-voltage protection with delay |
| • | Two comparator inputs for user defined protection - one with delay |
| • | Thermal shutdown |
| • | Self-discharge of output capacitors when the regulator is off |
| • | TSSOP package |
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 dual-phase, 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 adjustable UVLO feature.
Applications
| • | Embedded Computer Systems |
| • | Interactive Games |
| • | Set-top Boxes/Home Gateways |
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