MIC94300 MICREL [Micrel Semiconductor], MIC94300 Datasheet - Page 9

• Manufacturer Part Number: MIC94300
• Manufacturer: MICREL [Micrel Semiconductor]

Micrel, Inc.
Application Information
The MIC94300 utilizes Ripple Blocker™ technology to
integrate a load switch with a high-performance active
filter. The MIC94300 includes a low-voltage logic enable
pin, and is fully protected from damage due to fault
conditions, offering linear current limiting and thermal
shutdown.
Input Capacitor
The MIC94300 is a high-performance, high-bandwidth
device. An input capacitor of 470nF 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
recommended for the input capacitor. Y5V dielectrics
lose most of their capacitance over temperature and are
therefore, not recommended.
Output Capacitor
The MIC94300 requires an output capacitor of 0.47µF or
greater to maintain stability. For optimal ripple rejection
performance a 1µF capacitor is recommended. 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
recommended
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
The MIC94300 will remain stable with no load. This is
especially
applications.
February 2012
dielectric
circuit.
important
because
X5R
type
in
or
CMOS
ceramic
of
X7R
their
RAM
capacitors
dielectrics
temperature
keep-alive
are
are
9
Enable/Shutdown
The MIC94300 comes with an active-high enable pin
that allows the Ripple Blocker™ to be disabled. Forcing
the enable pin low disables the MIC94300 and sends it
into a “zero” off mode current state. In this state, current
consumed by the MIC94300 goes nearly to zero. Forcing
the enable pin high enables the output voltage. The
active-high enable pin uses CMOS technology and the
enable pin cannot be left floating; a floating enable pin
may cause an indeterminate state on the output.
Thermal Considerations
The MIC94300 is designed to provide 200mA 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 which is fixed at 170mV typical, 250mV worst case.
For example if the input voltage is 2.75V, the output
voltage is 2.5V, and the output current = 200mA. The
actual power dissipation of the Ripple Blocker™ can be
determined using the equation:
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:
To
temperature of the package, use the junction-to-ambient
thermal resistance of the device and the following basic
equation:
T
die, θ
package and 173°C/W for the YMT package.
J(max)
determine
= 125°C, the maximum junction temperature of the
JA
P
P
P
P
D
D
D
D(MAX)
thermal resistance = 250°C/W for the YCS
= (V
= (2.75V − 2.5V) × 200mA
= 0.05W
=
IN
⎛
⎜
⎜
⎝
− V
the
T
J(MAX)
OUT1
θ
maximum
JA
) I
−
OUT
T
A
+ V
⎞
⎟
⎟
⎠
IN
I
GND
ambient
M9999-020312-A
MIC94300
operating