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LM2635

National Semiconductor
Part Number LM2635
Manufacturer National Semiconductor
Description 5-Bit Programmable Synchronous Buck Regulator Controller
Published Mar 22, 2005
Detailed Description LM2635 5-Bit Programmable Synchronous Buck Regulator Controller May 2000 LM2635 5-Bit Programmable Synchronous Buck Re...
Datasheet PDF File LM2635 PDF File

LM2635
LM2635

Overview
LM2635 5-Bit Programmable Synchronous Buck Regulator Controller May 2000 LM2635 5-Bit Programmable Synchronous Buck Regulator Controller General Description 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.
Features n n n n n n n n n n n 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 exte...


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