FAN5090

www.fairchildsemi.com FAN5090 Two Phase Interleaved Synchronous Buck Converter for VRM 9.x Applications Features • Programmable output from 1.10V to 1.85V in 25mV steps using an integrated 5-bit DAC • Two interleaved synchronous phases for maximum performance • 100nsec transient response time • Built-in current sharing between phases • Remote sense • Programmable Active Droop (Voltage Positioning) • Programmable switching frequency from 100KHz to 300KHz per phase • Adaptive delay gate switching • Integrated high-current gate drivers • Integrated Power Good, OV, UV, Enable/Soft Start functions • Drives N-channel MOSFETs • Operation optimized for 12V operation • Overcurrent protection using MOSFET sensing • 24 pin TSSOP package Description The FAN5090 is a synchronous two-phase DC-DC controller IC which provides a highly accurate, programmable output voltage for VRM 9.x processors. Two interleaved synchronous buck regulator phases with built-in current sharing operate 180° out of phase to provide the fast transient response needed to satisfy high current applications while minimizing external components. The FAN5090 features Programmable Active Droop for transient response with minimum output capacitance. It has integrated high-current gate drivers, with adaptive delay gate switching, eliminating the need for external drive devices. The FAN5090 uses a 5-bit D/A converter to program the output voltage from 1.10V to 1.85V in 25mV steps with an accuracy of 1%. The FAN5090 uses a high level of integration to deliver load currents in excess of 50A from a 12V source with minimal external circuitry. The FAN5090 also offers integrated functions including Power Good, Output Enable/Soft Start, under-voltage lockout, over-voltage protection, and adjustable current limiting with independent current sense on each phase. It is available in a 24 pin TSSOP package. Applications • • • • Power supply for Pentium IV Power supply for Athlon VRM for Pentium IV processor Programmable step-down power supply Block Diagram BYPASS 6 23 RT +12V 18 5V Reg UVL O BOOT A 13 +12V OSC 14 + - Digital Control 15 +12V 17 16 BOOT B VO +12V + GNDA Current Limit + + + 12 11 Digital Control 10 +12V 8 9 5-Bit DAC 1 23 4 5 VID0 VID2 VID4 VID1 VID3 24 Power Good 19 PWRGD 21 7 22 ENABLE/SS 20 ILIM DROOP/E* AGND Pentium is a registered trademark of Intel Corporation. Athlon is a registered trademark of AMD. Programmable Active Droop is a trademark of Fairchild Semiconductor. REV. 1.0.1 9/16/03 FAN5090 PRODUCT SPECIFICATION Pin Assignments VID0 VID1 VID2 VID3 VID4 BYPASS AGND LDRVB PGNDB SWB HDRVB BOOTB 1 2 3 4 5 6 7 8 9 10 11 12 24 23 22 21 20 19 18 17 16 15 14 13 VFB RT ENABLE/SS DROOP ILIM PWRGD VCC LDRVA PGNDA SWA HDRVA BOOTA FAN5090 Pin Definitions Pin Number 1-5 6 7 8 Pin Name VID0-4 BYPASS AGND LDRVB Pin Function Description Voltage Identification Code Inputs. Internally pulled-up open collector/TTL compatible inputs program the output voltage over range specified in Table 1. 5V Rail. Bypass this pin with a 0.1µF ceramic capacitor to AGND. Analog Ground. Return path for low power analog circuitry. This pin should be connected to a low impedance system ground plane to minimize ground loops. Low Side FET Driver for B. Connect this pin to the gate of an N-channel MOSFET for synchronous operation. The trace from this pin to the MOSFET gate should optimally be