MP100LGN Datasheet, PDF (12/18 Pages) MPS Industries, Inc. – Offline Inductor-Less Regulator For Low Power Application

MP100L EASYPOWER^TM – OFFLINE INDUCTOR-LESS REGULATOR
APPLICATION INFORMATION
COMPONENT SELECTION
Setting the Output Voltage
The output voltage is set to 12V by internal large
feedback resistors. Adjust VOUT by choosing
appropriate external feedback resistors. The
recommended output voltage is between 1.5V
and 15V. Defining the upper and lower feedback
resistors as R_UP and R_LW respectively (refer to the
picture in Typical Application section):
R_UP
= R_LW
× ( ^VOUT
1.235
− 1)
For the external resistors to dominate over the
internal resistors, select relatively small values of
R_UP and R_LW compared to the internal resistors.
However, to minimize the load consumption,
avoid very small external resistors. For most
applications, choose R_LW=10.2kΩ. To accurately
set the output voltage, select an R_UP that can
counter the internal upper-feedback resistor
value of 1MΩ. The table below lists typical
resistor values for different output voltages:
Table 1: Resistors Selecting vs. Output Voltage
Setting
VOUT(V)
1.5
3.3
5
15
R_UP(kΩ)
2.21(1%)
16.9(1%)
30.9(1%)
121(1%)
R_LW(kΩ)
10.2(1%)
10.2(1%)
10.2(1%)
10.2(1%)
SELECTION OF VD CAPACITOR
The bypass capacitor on the VD pin needs to be
sufficiently large to provide a stable current.
Calculate the capacitance (in μF) based on the
following equation:
C_VD
=
I_load × τ_s
V_ripple
Where, I_load is the output current (mA); τ _s is
based on the type of input rectifier—for example,
τ _s ^{is 20ms for a half-wave rectifier, and 10ms for}
a full-bridge rectifier, V_ripple is the voltage ripple on
the VD capacitor—normally the ripple is limited to
2V to 3V. For best results, use a small ceramic
capacitor and a large aluminum capacitor in
parallel.
Output Power Capability
The maximum input power to the VD capacitor is
limited by the fixed charging window. Considering
the LDO power loss, the MP100L has a limited
maximum output power.
The following factors influence the MP100L’s
maximum output power: the input rectifier (full
bridge or half-wave); the VD capacitor connected
between VD and GND; the output voltage; and
the MP100L’s temperature-rise requirement,
which is relative to the different application
environments.
V_IN
V_IN
V_AC
V_AC
GND
GND
Full Bridge Rectifier Half-wave Rectifier
Figure depicts the relationship between the
maximum output power and the VIN voltage
when the output voltage is 12V, 5V and 3.3V,
respectively. The plots account for full bridge
rectifiers, the temperature rise of MP100L is less
than 60°C on the test board in 25°C room
temperature test in the open frame.
Figure 2: Output Power vs. Input Voltage
Line Transformer
MP100L can work well when connected to AC
line or programmable AC source. But when using
an isolation transformer or a variable transformer
as source, because of the high inductance of the
MP100L Rev. 1.0
www.MonolithicPower.com
12
11/3/2014
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