MP2932 - 6-PHASE PWM CONTROLLER WITH 8-BIT ADC CODE

MP2932 Rev.1.02

www.MonolithicPower.com

15

4/30/2012

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© 2012 MPS. All Rights Reserved.

R

R

CC

TM

0.33V

0.28V

VR_FAN

VR_HOT

°C

REF

TM1

CC

VCC

Figure 10—Block Diagram of Thermal

Monitoring Function

Figure 10 shows the diagram of thermal

monitoring function block. One NTC resistor

should be placed close to the power stage of

the voltage regulator to sense the temperature,

and one pull-up resistor is needed to form the

voltage divider for the TM pin. As the

temperature of the power stage increases, the

resistance of the NTC will reduce, resulting in

the reduced voltage at the TM pin.

There are two comparators with hysteresis to

compare the TM pin voltage to the fixed

thresholds for VR_FAN and VR_HOT signals

respectively. The VR_FAN signal is set to high

when the TM voltage is lower than 33% of VCC

voltage, and is pulled to GND when the TM

voltage increases to above 39% of VCC voltage.

The VR_FAN signal is set to high when the TM

voltage goes below 28% of VCC voltage, and is

pulled to GND when the TM voltage goes back

to above 33% of VCC voltage. Figure 11 shows

the operation of those signals.

TEMPERATURE

T1

T2

T3

VR_FAN

VR_HOT

TM

Figure 11—VR_HOT and VR_FAN Signal vs.

TM Voltage

Current Sense Output

The MP2932 has 2 current sense output pins

IDROOP and IOUT, they are identical. In typical

application, IDROOP pin is connected to FB pin

for the application where load line is required.

IOUT pin was designed for load current

measurement.

The current from the IDROOP pin is the sensed

average current. In typical application, the

IDROOP pin is connected to the FB pin for the

application where load line is required. Load

current

information

can

be

obtained

by

measuring the voltage at IOUT pin with a

resistor connecting IOUT pin to the ground.

When load line function is not needed, the

IDROOP pin can be used to obtain the load

current information: with one resistor from the

IDROOP pin to GND, the voltage at the

IDROOP pin will be proportional to the load

current in Equation (14):

LOAD

I

ISEN

R

X

R

N

IDROOP

R

IDROOP

V



(14)

to the ISEN+ pin, N is the active channel

sense element, either the DCR of the inductor

The resistor from the IDROOP pin to GND

should be chosen to ensure that the voltage at

the IDROOP pin is less than 2V under the

maximum load current.

If the IDROOP pin is not used, tie it to GND.