RT8167B datasheet(35/38 Pages) RICHTEK

35 / 38 page

RT8167B

DS8167B-00

October 2011

www.richtek.com

Figure 15. OCP Setting with Temperature Compensation

OCSETx

VCC

ROC1b

ROC2

ROC1a

NTC

Usually, ROC1a is selected to be equal to the thermistor's

nominal resistance at room temperature. Ideally, VOCSET

is assumed to have the same temperature coefficient as

RSENSE (Inductor DCR) :

OCSET, HOT

SENSE, HOT

OCSET, COLD

SENSE, COLD

(19)

(18)

OC1

OC2

OCSET

⎛⎞

=×

−

⎜⎟

⎝⎠

Figure 14. OCP Setting without Temperature

Compensation

VCC

OCSETx

ROC1

ROC2

The current limit is triggered when inductor current

exceeds the current limit threshold ILIMIT, defined by

VOCSET. The driver will be forced to turn off UGATE until

the over current condition is cleared. If the over current

condition remains valid for 15 PWM cycles, VR will trigger

OCP latch. Latched OCP forces both UGATE and LGATE

to go low. When OCP is triggered in one of VRs, the

other VR will enter into soft shutdown sequence. The OCP

latch mechanism will be masked when VRx_READY =

low, which means that only the current limit will be active

when VOUT is ramping up to initial voltage (or VREFx).

If inductor DCR is used as the current sense component,

then temperature compensation is recommended for

protection under all conditions. Figure 15 shows a typical

OCP setting with temperature compensation.

Over Current Protection

The CORE/GFX VR compares a programmable current

limit set point to the voltage from the current sense amplifier

output for Over Current Protection (OCP). The voltage

applied to OCSETx pin defines the desired peak current

limit threshold ILIMIT :

VOCSET = 48 x ILIMIT x RSENSE

(17)

Connect a resistive voltage divider from VCC to GND, with

the joint of the resistive divider connected to OCSET pin

as shown in Figure 14. For a given ROC2, then

The RT8167B supports two temperature reporting,

VRHOT(hardware reporting) and ALERT(software

reporting), to fulfill VR12/IMVP7 specification. VRHOT is

an open-drain structure which sends out active-low VRHOT

signals. When TSEN voltage rises above 1.855V (100%

of VR temperature), the VRHOT signal will be set to low.

When TSEN voltage drops below 1.8V (97% of VR

temperature), the VRHOT signal will be reset to high. When

TSEN voltage rises above 1.8V (97% of VR temperature),

The RT8167B will update the bit1 data from 0 to 1 in the

Status_1 register and assert ALERT. When TSEN voltage

drops below 1.745V (94% of VR temperature), VR will

update the bit1 data from 1 to 0 in the Status_1 register

and assert ALERT.

The temperature reporting function for the GFX VR can be

disabled by pulling TSENA pin to VCC in case the

temperature reporting function for the GFX VR is not used

or the GFX VR is disabled. When the GFX VR's

temperature reporting function is disabled, the RT8167B

will reject the SVID command of getting the

Temperature_Zone register content of the GFX VR.

However, note that the temperature reporting function for

the CORE VR is always active. CORE VR's temperature

reporting function can not be disabled by pulling TSEN

pin to VCC.

RT8167B Datasheet(PDF) 35 Page - Richtek Technology Corporation

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