●The LM2635 is a high speed controller designed specifically for use in synchronous DC/DC buck converters for the Pentium II or Deschutes microprocessor. A 5-bit DAC accepts the VID code directly from the CPU and adjusts the output voltage from 1.8V to 3.5V. It provides the power good, over-voltage protection, and output enable features as required by Intel VRM specifications. Current limiting is achieved by monitoring the voltage drop across the rDS_ON of the high side MOSFET, which eliminates an expensive current sense resistor.
●The LM2635 employs a fixed-frequency voltage mode PWM architecture. To provide a faster response to a large and fast load transient, two ultra-fast comparators are built in to monitor the output voltage and override the primary control loop when necessary. The PWM frequency is adjustable from 50 kHz to 1 MHz through an external resistor. The wide range of PWM frequency gives the power supply designer the flexibility to make trade-offs between load transient response performance, MOSFET cost and the overall efficiency. The adaptive non-overlapping MOSFET gate drivers help avoid any potential shoot-through problem while maintaining high efficiency. BiCMOS gate drivers with rail-to-rail swing ensure that no spurious turn-on occur. When only 5V is available, a bootstrap structure can be employed to accommodate an NMOS high side switch. The precision reference trimmed to 2% over temperature is available externally for use by other regulators. Dynamic positioning of load voltage, which helps cut the number of output capacitors, can also be implemented easily.
● 1.8V to 3.5V 5-Bit Programmable Output Voltage
● Synchronous Rectification
● Power Good Flag and Output Enable
● Over-Voltage Protection
● Initial Output Accuracy: 2% Over Temperature
● Current Limit without External Sense Resistor
● Adaptive Non-Overlapping MOSFET Gate Drives
● Adjustable Switching Frequency: 50 kHz to 1 MHz
● Dynamic Output Voltage Positioning
● 1.256V Reference Voltage Available Externally
● Plastic SOIC-20 Package
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