L6756D datasheet(20/36 Pages) STMICROELECTRONICS

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Output voltage positioning

L6756D

20/36

Output voltage positioning

Output voltage positioning is performed by selecting the controller operation mode (VR10,

VR11 or VR11.1) and by programming the droop function and offset to the reference of both

the sections (See Figure 6). The controller reads the current delivered by monitoring the

voltage drop across the Inductors DCR. The current (IDROOP) sourced from the DROOP pin,

directly proportional to the read current, causes the output voltage to vary according to the

external RFB resistor so implementing the desired load-line effect. A fixed current (IOS) is

sunk through the VSEN pins causing the output voltage to be offset according to the

resistance ROS connected.

L6756D allows to recover from GND losses in order to regulate remotely the programmed

voltage without any additional external components. In this way, the output voltage

programmed is regulated compensating for board and socket losses. Keeping the sense

traces parallel and guarded by a power plane results in common mode coupling for any

picked-up noise.

Both DROOP and OFFSET function can be disabled. In case DROOP effect is not desired,

the current information source from the DROOP pin may be used to implement a secondary

load indicator as reported in Section 5.3.

Figure 6.

Voltage positioning

5.1

Phase # programming

L6756D implements a flexible 2 to 4 interleaved-phase converter. To program the desired

number of phase, refer to Table 8.

For the disabled phase(s), the current reading pins need to be properly connected to avoid

errors in current-sharing and voltage-positioning: CSx needs to be connected to the regu-

lated output voltage while CSxN needs to be connected to CSx with the same RG resistor

used for the other phases.

L6756D Datasheet(PDF) 20 Page - STMicroelectronics