L6701 datasheet(4/44 Pages) STMICROELECTRONICS

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1 Device Description

L6701

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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.

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