MP100L EASYPOWER

OPERATION

MP100L employs a smart inductor-less regulator

design (patent pending) to charge the VD

capacitor (C1 in Typical Application Section) from

the offline AC input, and then to deliver the

stored energy to the load with a stable output

voltage. When VIN is less than its 34V threshold,

VD can be charged up by up to 1A input current.

An internal LDO regulates VOUT to 12V and can

supply up to 20mA load when VIN is between

85VAC and 305VAC. The proprietary design

allows the universal AC input to efficiently power

the IC directly.

Startup

During the startup, the internal switch connected

between VIN and VB turns on when the input

voltage is within its charging window (typically

below 34V), thus gradually charging the VD

voltage. The LDO will not resume with a soft-

start until the VD voltage reaches 15.4V.

Internal NMOS Switching

The EMI performance of MP100L greatly relates

to the turn-on and turn-off speed of internal

switch connected between VIN and VB. To pass

related emissions standards with only an X-cap

connected to the input ports, the MP100L slowly

turns off the internal switch when the VIN voltage

reaches

34V,

and

turns

the

switch

off

immediately when VIN reaches 86V during the

turn-off period. During the turn-on period, when

VIN falls to 31.5V, the internal switch turns on

slowly. The turn on and turn off slope is130us/A.

To avoid mis-triggered of internal switch when

there is noise or inductive kick in input voltage,

when Vin falls to 31.5V, the internal switch starts

to turn on, and there will be 110us blanking to

filer the noise of VIN to let the switch on, when

VIN rises to 34V, the internal switch starts to turn

off, and there is 300us blanking to prevent the

switch return on.

Active Bleeder Circuit

The input voltage may not enter its charging

window during normal operation due to parasitic

capacitance from VIN to GND. An active bleeder

circuit is enabled to pull down the VIN voltage

whenever the VD voltage falls below 14.4V to

guarantee that the output gets enough energy

from the input ports. In addition, when the power

supply shuts down, the active bleeder circuit

discharges the energy stored in the parasitic

capacitor to ensure that the circuit can restart

easily.

VD Over-Voltage Protection

The VD capacitor provides energy for the output

load. If the voltage of VD exceeds 21V, the

internal switch between VIN and VB turns off

immediately to prevent the VD voltage from rising

too high, which can damage the LDO stage.

VD Short-Circuit Protection

The output current is limited to 220mA if the

output

is

shorted

to

ground,

which

also

decreases the VD voltage. When VD drops

below 7.0V, LDO turns off. The input voltage then

gradually charges VD up to 15.4V to enable the

LDO. When LDO turns on, the output current

drops the VD voltage to 7.0V again. This process

will continue until the output short condition

ceases.

VOUT Over-Current Protection

The

VD

and

VOUT

voltages

will

drop

simultaneously if the output current exceeds its

normal value. When the VD voltage falls to 7.0V,

the second stage LDO shuts down immediately.

Then the input voltage charges VD to 15.4V to

enable the LDO. Due to the output current limit

circuit, the maximum current is typically limited to

220mA.

Thermal Shutdown Protection

Accurate temperature protection prevents the

chip

from

operating

at

exceedingly

high

temperature. When the silicon die temperature

exceeds 160°C, the whole chip shuts down.

When the temperature falls below its lower

threshold of 140

°C, the chip is enabled again.

MP100L Rev. 1.0

www.MonolithicPower.com

10

11/3/2014

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

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