PM6652 datasheet(25/53 Pages) STMICROELECTRONICS

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PM6652

Device description

Doc ID 16867 Rev 5

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Device description

The PM6652 is a single-phase, step-down controller which can be easily configured to

regulate power to IMPV6.5 and VR11 devices, as listed below:

●

The graphics (Render) core of the Intel® mobile Arrandale processor used on the

Calpella platform

●

The low voltage and ultra low voltage mobile CPU, used on the Calpella platform

●

The VR11 compliant CPU, like Intel® ATOM 200/300 and Pineview-D CPU.

The supply mode and platform compliance are selected by acting on two multi-function pins

(refer to

Section 8.2: Mode selection for details), before the device turn-on.

The PM6652 is based on constant on-time control architecture. This type of control offers a

very fast load transient response with a minimum external component count. A typical

application circuit is shown in

Figure 1. The controller includes a 7-bit digital-to-analog

converter (DAC) that provides a reference voltage according to the VID pin settings (see

Table 6 and Table 7). The PM6652 also allows the adjusting of an active load line (or droop)

control, proportional to the inductor DCR or dedicated precision resistor, according to

IMVP6.5 specifications.

The switching frequency can be programmed in the range 200 kHz up to 600 kHz with an

external resistor connected to the input voltage (see

Section 8.1: Constant on-time PWM

control for details).

In order to maximize the efficiency at very light load, a pulse-skipping control algorithm is

performed. The PM6652 is also fully compliant with the fast and slow render suspend state

exit mode, as required by IMVP 6.5 spec. for render core supply (see

Section 8.6: Voltage

dynamic (VID) transitions for details).

The device provides protection for overvoltage, undervoltage, overcurrent and

overtemperature as well as power good (PWRGD), current monitor (IMON) and thermal

throttling (VRTT#) signals for monitoring purposes. The clock enable output signal

(CLKEN#), for appropriate platform power-up, is available in CPU supply mode only.

8.1

Constant on-time PWM control

The PM6652 controller uses a pseudo-fixed frequency, constant on-time (COT) controller as

the core of the switching section. The COT controller uses a relatively simple algorithm,

exploiting the ripple voltage due to inductor resistance DCR (or due to a sense resistor

RSNS) to trigger the fixed on-time one-shot generator.

Nearly constant switching frequency is achieved by the system loop in steady-state

operating conditions, therefore avoiding the need for a clock generator. A slight switching

frequency variation towards the load is the consequence of the switching regulator power

losses, which implies the off-time duration decrease.

The on-time one-shot duration is directly proportional to the output voltage, sensed at the

VOUT pin, and inversely proportional to the input voltage, sensed at the VOSC pin, as

follows:

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