PM6641 Monolithic VR for chipset and DDR2/3 supply for ultra-mobile PC (UMPC) applications Features 0.8 V 1% internal voltage reference 2.7 V to 5.5 V input voltage range Fast response, constant frequency, current mode control Three independent, adjustable, out-of-phase VFQFPN-48 7x7 mm SMPS for DDR2/3 (VDDQ) and chipset supply Low noise DDR2/3 reference (VTTREF) 2 Apk LDO for DDR2/3 termination (VTT) Description with foldback S0-S5 states compliant DDR2/3 section The PM6641 is a monolithic voltage regulator module specifically designed to supply DDR2/3 Active soft-end for all outputs memory and chipset in ultra-mobile PC and real Selectable tracking discharge for VDDQ estate constrained portable systems. Separate Power Good signals It integrates three independent, adjustable, Pulse skipping at light load constant frequency buck converters, a 2 Apk low drop-out (LDO) linear regulator and a Programmable current limit and soft-start for 15 mA low noise buffered reference. all outputs Latched OVP, UVP protection Each regulator provides basic UV and OV protections, programmable soft-start and current Thermal protection limit and active soft-end. Pulse-skipping technique is performed to increase Applications efficiency at very light load. DDR2/3 memory and chipset supply UMPC and portable equipment Handheld and PDAs Table 1. Device summary Order codes Package Packaging PM6641 Tray VFQFPN-48 7x7 (exposed pad) PM6641TR Tape and reel May 2009 Doc ID 13510 Rev 3 1/47 www.st.com 47 Contents PM6641 Contents 1 Typical application circuit 3 2 Pin settings 4 2.1 Connections 4 2.2 Pin description 5 3 Electrical data 7 3.1 Maximum rating . 7 3.2 Thermal data . 7 3.3 Recommended operating conditions . 8 4 Electrical characteristics . 9 5 Typical operating characteristics . 13 6 Block diagram . 17 7 Device description . 18 7.1 Memory supply 19 7.1.1 VDDQ switching regulator 19 7.1.2 VTT LDO and VTTREF buffered reference 20 7.1.3 VTT and VTTREF soft-start . 20 7.1.4 S3 and S5 power management pins . 21 7.2 Chipset supply . 21 7.3 SW regulators control loop 23 7.4 SW regulators pulse skipping and PWM mode 25 7.5 Output voltage divider . 26 7.6 Outputs soft-start . 27 7.7 Outputs soft-end 28 7.8 Switching frequency selection . 28 7.9 Phase management . 29 7.10 Peak current limit . 30 7.11 Fault management 32 2/47 Doc ID 13510 Rev 3