MIC5256-2.6YM5 TR Micrel Inc, MIC5256-2.6YM5 TR Datasheet - Page 10

• Manufacturer Part Number: MIC5256-2.6YM5 TR
• Description: 150mA UCap LDO W/Flag( )
• Manufacturer: Micrel Inc

Specifications of MIC5256-2.6YM5 TR

• Regulator Topology: Positive Fixed
• Voltage - Output: 2.6V
• Voltage - Input: Up to 6V
• Voltage - Dropout (typical): 0.135V @ 150mA
• Number Of Regulators: 1
• Current - Output: 150mA
• Current - Limit (min): 160mA
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-5, SC-74A, SOT-25
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 576-1841-2; MIC5256-2.6YM5TR; MIC5256-2.6YM5TR

Application Information
Enable/Shutdown
The MIC5256 comes with an active-high enable pin that
allows the regulator to be disabled. Forcing the enable
pin low disables the regulator and sends it into a “zero”
off-mode-current state. In this state, current consumed
by the regulator goes nearly to zero. Forcing the enable
pin high enables the output voltage. This part is CMOS
and the enable pin cannot be left floating; a floating
enable pin may cause an indeterminate state on the
output.
Input Capacitor
The MIC5256 is a high-performance, high-bandwidth
device. Therefore, it requires a well-bypassed input
supply for optimal performance. A 1µF capacitor is
required from the input to ground to provide stability.
Low-ESR
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.
Output capacitor
The MIC5256 requires an output capacitor for stability.
The design requires 1µF or greater on the output to
maintain stability. The design is optimized for use with
low-ESR ceramic-chip capacitors. High-ESR capacitors
may cause high-frequency oscillation. The maximum
recommended ESR is 300mΩ. 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.
Error Flag
The error flag output is an active-low, open-drain output
that drives low when a fault condition AND an under-
voltage detection occurs. Internal circuitry intelligently
monitors overcurrent, overtemperature and dropout
conditions and ORs these outputs together to indicate
some fault condition. The output of that OR gate is
ANDed with an output voltage monitor that detects an
undervoltage condition. That output drives the open-
Micrel, Inc.
August 2010
dielectric-type
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10
drain transistor to indicate a fault. This prevents
chattering or inadvertent triggering of the error flag. The
error flag must be pulled-up using a resistor from the flag
pin to either the input or the output.
The error flag circuit was designed essentially to work
with a capacitor to ground to act as a power-on reset
generator, signaling a power-good situation once the
regulated voltage was up and/or out of a fault condition.
This capacitor delays the error signal from pulling high,
allowing the down stream circuits time to stabilize. When
the error flag is pulled-up to the input without using a
pull-down capacitor, then there can be a glitch on the
error flag upon start up of the device. This is due to the
response time of the error flag circuit as the device starts
up. When the device comes out of the “zero” off mode
current state, all the various nodes of the circuit power
up before the device begins supplying full current to the
output capacitor. The error flag drives low immediately
and then releases after a few microseconds. The
intelligent circuit that triggers an error detects the output
going into current limit AND the output being low while
charging the output capacitor. The error output then pulls
low for the duration of the turn-on time. A capacitor from
the error flag to ground will filter out this glitch. The glitch
does not occur if the error flag pulled up to the output.
Active Shutdown
The MIC5256 also features an active shutdown clamp,
which is an N-channel MOSFET that turns on when the
device is disabled. This allows the output capacitor and
load to discharge, de-energizing the load.
No Load Stability
The MIC5256 will remain stable and in regulation with no
load unlike many other voltage regulators. This is
especially
applications.
Thermal Considerations
The MIC5256 is designed to provide 150mA of
continuous current in a very small package. Maximum
power dissipation can be calculated based on the output
current and the voltage drop across the part. To
determine the maximum power dissipation of the
package, use the junction-to-ambient thermal resistance
of the device and the following basic equation:
P
D(max)
important
=
⎛
⎜
⎜
⎝
T
J(max)
θ
JA
in
−
T
CMOS
A
⎞
⎟
⎟
⎠
RAM
M9999-080510
MIC5256
keep-alive