L6711 datasheet(18/50 Pages) STMICROELECTRONICS

18 / 50 page

Device description

L6711

18/50

Device description

The device is a three 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 modern high current DC/DC converters and POLs. 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 120° of 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

show an effective output switching frequency increase: the 150kHz free-running frequency

per phase, externally adjustable through a resistor, results tripled on the output.

The controller includes multiple DACs, selectable through an apposite pin (VID_SEL),

allowing compatibility with both VRD 10.x and Hammer specifications, also performing D-

VID transitions accordingly. The output voltage can be precisely selected, programming the

VID and VID_SEL pins, from 0.8185V to 1.5810V with 12.5mV binary steps (VRD 10.x

compliant mode - 6 BIT with -19mV offset already programmed during production) or from

0.800V to 1.550V with 25mV steps (VRM Hammer compliant mode - 5 BIT, VID5 programs

a 25mV positive offset in this case), with a maximum tolerance on the output regulated

voltage of ±0.5% (±0.6% for Hammer) over temperature and line voltage variations.

The device permits easy and flexible system design by allowing current reading across

either inductor or low side mosfet in fully differential mode simply selecting the desired way

through the CS_SEL pin. In both cases, also a sense resistor in series to the related

element can be considered to improve reading precision. The current information read

corrects the PWM output in order to equalize the average current carried by each phase

limiting the error at ±3% over static and dynamic conditions unless considering the sensing

element spread.

The device provides a programmable Over-Voltage protection to protect the load from

dangerous over stress and can be externally set to a fixed voltage through an apposite

resistor or it can be set internally with a fixed percentage, latching immediately by turning

ON the lower driver and driving high the FAULT pin. Furthermore, preliminary OVP

protection also allows the device to protect load from dangerous OVP when VCC is not

above the UVLO threshold.

Over-Current protection provided, with an OC threshold for each phase, causes the device

to enter in constant current mode until the latched UVP. Depending on the reading mode

selected, the device keeps constant the peak (inductor sensing) or the valley (LS sensing)

of the inductor current ripple.

The device drives high the FAULT pin after each latching event: to recover it is enough to

cycle VCC or the OUTEN pin.

A compact 7x7mm body TQFP48 package with exposed thermal pad allows dissipating the

power to drive the external mosfet through the system board.

L6711 Datasheet(PDF) 18 Page - STMicroelectronics

L6711 Datasheet(HTML) 18 Page - STMicroelectronics

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