MP2930 - 4-PHASE PWM CONTROLLER WITH 8-BIT DAC CODE

MP2930 Rev. 1.01

www.MonolithicPower.com

15

10/30/2013

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© 2013 MPS. All Rights Reserved.

Once

the

average

current

exceeds

the

reference current, a comparator triggers the

converter to shutdown.

At the beginning of over-current shutdown, the

controller places all PWM signals in a high-

impedance state within 20ns to turn off the

MP86961. The system remains in this state

about 12ms. If the controller is still enabled at

the end of this wait period, it will attempt a soft-

start. If the fault remains, the hiccup mode will

continue indefinitely until either controller is

disabled or the fault is cleared. Note that the

energy delivered during hiccup mode is much

less than during full-load operation, so there is

no thermal hazard during this kind of operation.

OUTPUT VOLTAGE

OUTPUT CURRENT

0A

0V

Figure 9

—Over-current Behavior in HICCUP

Mode. FSW = 600kHz

For

the

individual

channel

over-current

protection, the MP2930 continuously compares

the sensed current signal of each channel with

the 120µA reference current. If one channel

current exceeds the reference current, MP2930

will pull PWM signal of this channel to low for

the rest of the switching cycle. This PWM signal

can be turned on next cycle if the sensed

channel

current

is

less

than

the

120µA

reference current. The peak current limit of

individual channel will not trigger the converter

to shutdown.

Thermal Monitoring (VR_HOT/VR_FAN)

There are two thermal signals to indicate the

temperature status of the voltage regulator:

VR_HOT and VR_FAN. Both VR_FAN and

VR_HOT pins are open-drain outputs, and

external pull-up resistors are required. Those

signals are valid after the controller is enabled.

The

VR_FAN

signal

indicates

that

the

temperature of the voltage regulator is high and

more cooling airflow is needed. The VR_HOT

signal can be used to inform the system that the

temperature of the voltage regulator is too high

and

the

CPU

should

reduce

its

power

consumption.

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

The diagram of thermal monitoring function

block is shown in Figure 10. One NTC resistor

should be placed close to the power stage of

the voltage regulator to sense the operational

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.

TEMPERATURE

T1

T2

T3

VR_FAN

VR_HOT

TM

Figure 11

—VR_HOT and VR_FAN Signal vs.

TM Voltage

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