3 Phase Controller

L6701 3 Phase Controller for VR10, VR9 and K8 CPUs Features ■ MULTI-DAC: VR9, VR10 AND K8 DAC SELECTABLE THROUGH SINGLE PIN 0.7% OUTPUT VOLTAGE ACCURACY ADJUSTABLE REFERENCE OFFSET HIGH CURRENT INTEGRATED DRIVERS DYNAMIC VID MANAGEMENT ACCURATE FULLY-DIFFERENTIAL LOADLINE CURRENT-SENSE ACROSS MAIN INDUCTORS MAKES BOM INDEPENDENT ON THE LAYOUT PRECISE CURRENT-SHARING AND OCP ACROSS LS MOSFETS CONSTANT OVER-CURRENT PROTECTION FEEDBACK DISCONNECTION PROTECTION PRELIMINARY OV PROTECTION OSCILLATOR INTERNALLY FIXED AT 100kHz (300kHz RIPPLE) EXT ADJUSTABLE SS_END / PGOOD SIGNAL INTEGRATED REMOTE-SENSE BUFFER PWSSO36 PACKAGE WITH EXPOSED PAD PowerSSO-36 ■ ■ ■ ■ ■ Description L6701 is an extremely simple, low-cost solution to implement a three phase step-down controller with integrated high-current drivers in a compact PowerSSO-36 package with exposed pad. The device embeds three selectable DACs: with a single pin it is possible to program the device to work in compatibility with VR9, VR10 or K8 applications managing D-VID with ±0.7% output voltage accuracy over line and temperature variations. Additional programmable offset can be added to the reference voltage with a single external resistor. Fast protection against load over current let the system works in Constant Current mode until UVP. Preliminary OVP allows full load protection in case of startup with failed HS. Furthermore, feedback disconnection prevents from damaging the load in case of misconnections in the system board. Combined use of DCR and RDS(on) current sensing assures precision in voltage positioning and safe current sharing and OCP per each phase. ■ ■ ■ ■ ■ ■ ■ ■ Applications ■ HIGH CURRENT VRM / VRD FOR DESKTOP / SERVER/ WORKSTATION CPUs HIGH DENSITY DC / DC CONVERTERS ■ Order codes Part number L6701 L6701TR Package PowerSSO-36 PowerSSO-36 Packing Tube Tape & Reel Rev 1 1/44 www.st.com 44 December 2005 L6701 Contents 1 2 Device Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Pins description and connection diagrams . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1 3.2 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4 Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.1 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5 Typical application circuit and block diagram . . . . . . . . . . . . . . . . . . . . . 11 5.1 5.2 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6 7 VID Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Configuring the Device: DAC Selection . . . . . . . . . . . . . . . . . . . . . . . . . . 17 7.1 Single-Wire CPU Automatic Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 8 Driver Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 8.1 Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 9 Current Sharing Loop and Current Reading . . . . . . . . . . . . . . . . . . . . . . . 20 9.1 9.2 Current Sharing Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Current Reading for Current Sharing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 10 Output Voltage Positioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 10.1 10.2 10.3 10.4 10.5 Load-Line (Droop Function - Optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Fully-Differential Load-Line (Droop Function - Optional) . . . . . . . . . . . . . . . 22 Offset (Optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Remote Voltage Sense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Maximum Duty Cycle limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 2/44 L6701 11 12 Dynamic VID Transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Soft Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 12.1 Low-Side-Less Startup (LSLess) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 13 Output voltage Monitor and Protections . . . . . . . . . . . . . . . . . . . . . . . . . . 29 13.1 13.2 13.3 13.4 13.5 13.6 Under Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Preliminary Over Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Over Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Feedback Disconnection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 PGOOD (Only for VR9 and K8 Modes) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Over Current Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 14 15 Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 System Control Loop Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 15.1 Compensation Network Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 16 Layout Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 16.1 16.2 16.3 Power Components and Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Small Signal Components and Connections . . . . . . . . . . . . . . . . . . . . . . . . . 39 Embedding L6701-based VRs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 17 18 Package Mechanical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 3/44 1 Device Description L6701 1 Device Description L6701 is multi-phase PWM controller with embedded high-current drivers that provides complete control logic and protections for a high-performance step-down DC-DC voltage regulator, optimized for advanced microprocessor power supply. Multi-phase buck is the simplest and most cost-effective topology employable to satisfy the increasing current demand of newer microprocessors and the modern high-current DC/DC converters and POLs requirements. It allows distributing equally load and power between the phases using smaller, cheaper and most common external power MOSFETs and inductors. Moreover, thanks to the equal phase-shift between each phase, the input and output capacitor count results in being reduced. Phase-interleaving causes in fact input rms current and output ripple voltage reduction and shows an effective output switching frequency increase: the 100kHz free-running frequency per phase, externally adjustable through a resistor, results multiplied on the output by the number of phases so reaching 300kHz in free-running. L6701 includes multiple DACs, selectable through an apposite pin, allowing compatibility with both Intel VR9, VR10 and AMD Hammer specifications, also performing D-VID transitions accordingly. In particular for Intel CPUs, it allows to automatically recognize the CPU with a single-wire connection, without any additional external component, by proper connecting the selector pin to the proper CPU pin. Precise voltage positioning (LL) is possible thanks to an accurate fully-differential current-sense across the main inductors still using only two pins for current-reading (pat. pend.): this makes any BOM insensitive to the board layout saving time in the design stage. The device internally balance the current driven by each phase by sensing the voltage drop across the LS MOSFET RDS(on). OC protection is effective with a threshold for each phase causing the device to work in constant-current mode. The controller provides output voltage protections to avoid any load damage due to failed components and/or feedback misconnections. Over-Voltage protects the load from dangerous over stress latching immediately the device by turning-on the lower driver and driving high the FAULT pin. Furthermore, preliminary-OVP protection also allows the device to protect the load from dangerous OVP when VCC is not above the UVLO threshold. Under-Voltage protection causes the device to stop switching when set while Over-Current protection, with a threshold for each phase, causes the device to enter in constant current mode until the latched UVP. L6701 implements soft-start increasing the reference up to the final value in 2048 clock cycles in closed loop regulation. Low-Side-Less feature allows the device to perform soft-start over pre-biased output avoiding dangerous current return through the main inductors as well as negative spike at the load side. The compact PowerSSO-36 package with exposed thermal pad allows dissipating the power to drive the external MOSFET through the system board. 4/44 L6701 2 Pins description and connection diagrams 2 Figure 1. Pins description and connection diagrams Pins connection (Top view) SGND VCC LGAT