ADP3180 datasheet(10/20 Pages) AD

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ADP3180

–10–

six VID inputs are changing. Additionally, the ﬁrst VID change

initiates the PWRGD and CROWBAR blanking functions for a

minimum of 250 µs to prevent a false PWRGD or CROWBAR

event. Each VID change will reset the internal timer. Figure 3

shows VID on-the-ﬂy performance when the output voltage is

stepping up and the output current is switching between mini-

mum and maximum values, which is the worst-case situation.

Figure 3. VID On-the-Fly Waveforms, Circuit of Figure 5.

VID Change = 5 mV, 5 µs per Step, 50 Steps,

IOUT Change = 5 A to 65 A

Power Good Monitoring

The Power Good comparator monitors the output voltage via the

CSREF pin. The PWRGD pin is an open-drain output whose

high level (when connected to a pull-up resistor) indicates that

the output voltage is within the nominal limits speciﬁed in the

Speciﬁcations table based on the VID voltage setting. PWRGD

will go low if the output voltage is outside of this speciﬁed range.

PWRGD is blanked during a VID OTF event for a period of

250 µs to prevent false signals during the time the output is

changing.

Output Crowbar

As part of the protection for the load and output components of

the supply, the PWM outputs will be driven low (turning on the

low side MOSFETs) when the output voltage exceeds the upper

Power Good threshold. This crowbar action will stop once the

output voltage has fallen below the release threshold of approxi-

mately 450 mV.

Turning on the low side MOSFETs pulls down the output as the

reverse current builds up in the inductors. If the output overvolt-

age is due to a short of the high side MOSFET, this action will

current limit the input supply or blow its fuse, protecting the

microprocessor from destruction.

Output Enable and UVLO

The input supply (VCC) to the controller must be higher than

the UVLO threshold and the EN pin must be higher than its

logic threshold for the ADP3180 to begin switching. If UVLO is

less than the threshold or the EN pin is a logic low, the ADP3180

is disabled. This holds the PWM outputs at ground, shorts the

DELAY capacitor to ground, and holds the ILIMIT pin at

ground.

In the application circuit, the ILIMIT pin should be connected

to the

OD pins of the ADP3418 drivers. Because ILIMIT is

grounded, this disables the drivers such that both DRVH and

DRVL are grounded. This feature is important to prevent dis-

charging of the output capacitors when the controller is shut off.

If the driver outputs were not disabled, a negative voltage could

be generated on the output due to the high current discharge of

the output capacitors through the inductors.

APPLICATION INFORMATION

The design parameters for a typical Intel VRD 10 compliant

CPU application are as follows:

∑ Input voltage (V

IN) = 12 V

∑ VID setting voltage (V

VID) = 1.500 V

∑ Duty cycle (D) = 0.125

∑ Nominal output voltage at no load (V

ONL) = 1.480 V

∑ Nominal output voltage at 65 A load (V

OFL) = 1.3955 V

∑ Static output voltage drop based on a 1.3 mW load line (R

from no load to full load

∑ (V

D) = VONL – VOFL = 1.480 V – 1.3955 V = 84.5 mV

∑ Maximum Output Current (I

O) = 65 A

∑ Maximum Output Current Step (DI

O) = 60 A

∑ Number of Phases (n) = 3

∑ Switching frequency per phase (f

SW) = 267 kHz

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