L6718 datasheet(30/71 Pages) STMICROELECTRONICS

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Device configuration

L6718

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DocID023399 Rev 3

Section 6.6.2 ). This function can be useful in applications where the graphics section needs

to be designed with a multi-phase rail.

When setting MRO mode, the single-phase rail is off and Jmode can not be enabled. Jmode

bitstrapping is still used to select the multi-phase number (see Table 7).

6.4

Jmode

Jmode is selectable during startup through the CONFIG1 pinstrapping pin (see

Section 6.6.3 and Section 6.6.4).

If Jmode is configured, the controller sets the single-phase rail to switch as a completely

independent single-phase rail. As a consequence:

Single-phase rail is not addressed by the SVID bus. The device replies with a NACK to

any request by the CPU to communicate with the single-phase rail.

Single-phase rail becomes the DC-DC controller with an internal reference fixed at 0.75

V, so it is possible to select the output voltage by using a divider.

Droop is disabled on the single-phase rail.

The SREF/JEN pin is configured as single-phase rail enable. As a consequence, this

pin becomes a digital logic input. If it is set HIGH, the device turns on the single-phase

rail, otherwise the single rail remains off. An embedded pull-up sets the pin floating to

high.

The SVREADY is still used as single-phase Power Good.

Single-phase rail maximum current embedded register is fixed at 30 A.

In CPU mode, using the CONFIG0 pinstrapping, it is possible to set the used multi-

phase rail address to 01h (to supply the graphics section).

If a fault occurs on the multi-phase rail, the single-phase rail still runs.

If the device is set in a debug configuration (see Section 6.6), the multi-phase can turn

on only if Jmode is on, while in operating configuration the multi-phase rail and single-

phase rail can be turned on independently.

Jmode is an option for motherboard designs which need the multi-phase rail section to

supply the CPU CORE or DDR sections but they also need a single-phase high

performance DC-DC converter to supply other rails on the motherboard (such as VCCIO).

Jmode offers an advantage by having a free high performance single-phase buck controller

with voltage and current remote differential sensing, LTB, and voltage and current

protection. Output voltage can be increased with the use of an external divider or by adding

offset with SMBus or pinstrapping.

6.5

Phase number configuration

The multi-phase rail can be configured from 2 to 4-phase switching while the single-phase

rail can be also set off in MRO only. By using pinstrapping it is also possible to select the

number of embedded drivers used for the multi-phase rail (see Table 7).

During soft-start the device is able to check the status of the PWMx pins and set the multi-

phase rail total phase number. Setting SWAP mode the device uses all the embedded

drivers for the multi-phase rail section while external PWM is used for the single-phase rail

(see Section 6.3 for details). Jmode can change the status of the total phase number only in

MRO (see Section 6.3.1 for details).

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