MIC5501-1.8YMT-TR 데이터 시트보기 (PDF) - Unspecified
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MIC5501-1.8YMT-TR Datasheet PDF : 15 Pages
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Micrel, Inc.
Application Information
MIC5501/2/3/4 are low-noise 300mA LDOs. The
MIC5502 and MIC5504 include an auto-discharge circuit
that is switched on when the regulator is disabled
through the enable (EN) pin. The MIC5503 and MIC5504
have an internal pull-down resistor on the EN pin to
ensure the output is disabled if the control signal is tri-
stated. The MIC5501/2/3/4 regulator is fully protected
from damage due to fault conditions, offering linear
current limiting and thermal shutdown.
Input Capacitor
The MIC5501/2/3/4 is a high-performance, high-
bandwidth device. An input capacitor of 1µF is required
from the input to ground to provide stability. Low-ESR
ceramic capacitors provide optimal performance at a
minimum of space. Additional high-frequency capacitors,
such as small-valued NPO dielectric-type capacitors,
help filter out high-frequency noise and are good
practice in any RF-based circuit. X5R or X7R dielectrics
are recommended for the input capacitor. Y5V dielectrics
lose most of their capacitance over temperature and are
therefore, not recommended.
Output Capacitor
The MIC5501/2/3/4 requires an output capacitor of 1µF
or greater to maintain stability. The design is optimized
for use with low-ESR ceramic chip capacitors. High ESR
capacitors are not recommended because they may
cause high-frequency oscillation. The output capacitor
can be increased, but performance has been optimized
for a 1µF ceramic output capacitor and does not improve
significantly with larger capacitance.
X7R/X5R dielectric-type ceramic capacitors are
recommended because of their temperature
performance. X7R-type capacitors change capacitance
by 15% over their operating temperature range and are
the most stable type of ceramic capacitors. Z5U and
Y5V dielectric capacitors change value by as much as
50% and 60%, respectively, over their operating
temperature ranges. To use a ceramic chip capacitor
with Y5V dielectric, the value must be much higher than
an X7R ceramic capacitor to ensure the same minimum
capacitance over the equivalent operating temperature
range.
No-Load Stability
Unlike many other voltage regulators, the MIC5501/2/3/4
remains stable and in regulation with no load. This is
especially important in CMOS RAM keep-alive
applications.
MIC5501/2/3/4
Enable/Shutdown
The MIC5501/2/3/4 comes with an active-high enable
pin that allows the regulator to be disabled. Forcing the
EN pin low disables the regulator and sends it into an off
mode current state drawing virtually zero current. When
disabled the MIC5502 and MIC5504 switches an internal
25Ω load on the regulator output to discharge the
external capacitor.
Forcing the EN pin high enables the output voltage. The
MIC5501 and MIC5502 enable pin uses CMOS
technology and the EN pin cannot be left floating; a
floating EN pin may cause an indeterminate state on the
output. The MIC5503 and MIC5504 have an internal pull-
down resistor on the enable pin to disable the output
when the enable pin is floating.
Thermal Considerations
The MIC5501/2/3/4 is designed to provide 300mA of
continuous current in a very small package. Maximum
ambient operating temperature can be calculated based
on the output current and the voltage drop across the
part. For example if the input voltage is 3.6V, the output
voltage is 2.8V, and the output current = 300mA. The
actual power dissipation of the regulator circuit can be
determined using Equation 1:
PD = (VIN – VOUT1) I OUT + VIN IGND
Eq. 1
Because this device is CMOS and the ground current is
typically <100µA over the load range, the power
dissipation contributed by the ground current is < 1% and
can be ignored for this calculation:
PD = (3.6V – 2.8V) × 300mA
PD = 0.240W
To determine the maximum ambient operating
temperature of the package, use the junction-to-ambient
thermal resistance of the device and Equation 2:
PD(max)
=
TJ(max) −
θ JA
TA
Eq. 2
TJ(max) = 125°C, the maximum junction temperature of the
die, θJA thermal resistance = 250°C/W for the DFN
package.
April 20, 2015
9
Revision 2.3
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