MRF21010L

The MRF21010L provides a single chip controller IC for the Vcore, LDO controller for GTL+ and an internal 200mA regulator for clock supply which are required for the Pentium II applications. These devices feature a pat- ented topology that in combination with a few external components as shown in the typical application circuit, will provide in excess of 18A of output current for an on- board DC-DC converter while automatically providing the right output voltage via the 5-bit internal DAC. The MRF21010L also features loss-less current sensing for both switchers by using the RDS(on) of the high-side power MOSFET as the sensing resistor, internal current limit- ing for the clock supply, and a Power Good window com- parator that switches its open collector output low when any one of the outputs is outside of a pre-programmed window. Other features of the device are: Under-voltage lockout for both 5V and 12V supplies, an external pro- grammable soft-start function, programming the oscilla- tor frequency via an external resistor, Over-Voltage Pro- tection (OVP) circuitry for both switcher outputs and an internal thermal shutdown.

The MRF21010L routing of the modulated outputs requires special attention since these are particularly vulnerable to coupling from the VCO: unwanted coupling of the LO frequency to the RF output will modify the modulation depth. Typically, in instances where RF coupling is present, the amount of coupling (and the phase) will vary as the oscillator is tuned across the band, causing the modulation index to be either higher or lower than the situation where no RF coupling is present. Thus the modulation index will vary as the device is tuned from one channel to another. For VHF and other applications below 500MHz, oscillator coupling is not such an issue, however similar care should still be taken with the layout in order to maximise device performance.

The MRF21010L information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice. No liability will be accepted by the publisher for any consequence of its use. Publication thereof does not convey nor imply any license under patent- or other industrial or intellectual property rights.