MP100L EASYPOWERTM – OFFLINE INDUCTOR-LESS REGULATOR
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.
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.
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.
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.
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.
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.
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.
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.
Active Bleeder Circuit
The input voltage may not enter its charging
window during normal operation due to parasitic
MP100L Rev. 1.0
11/3/2014
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