MIC5255-2.8YD5 TR Micrel Inc, MIC5255-2.8YD5 TR Datasheet - Page 10

• Manufacturer Part Number: MIC5255-2.8YD5 TR
• Description: IC REG LDO 150MA 2.8V TSOT23-5
• Manufacturer: Micrel Inc

Specifications of MIC5255-2.8YD5 TR

• Regulator Topology: Positive Fixed
• Voltage - Output: 2.8V
• 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: TSOT-23-5, TSOT-5, TSOP-5
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 576-2818-2; MIC5255-2.8YD5 TR; MIC5255-2.8YD5TR; MIC5255-2.8YD5TR

Application Information
Enable/Shutdown
The MIC5255 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 MIC5255 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 MIC5255 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 dielectric-type ceramic capacitors are recom-
mended 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.
Bypass Capacitor
A capacitor can be placed from the noise bypass pin to
ground to reduce output voltage noise. The capacitor
bypasses the internal reference. A 0.01µF capacitor is
recommended for applications that require low-noise
outputs. The bypass capacitor can be increased, further
reducing noise and improving PSRR. Turn-on time
increases slightly with respect to bypass capacitance. A
unique quick-start circuit allows the MIC5255 to drive a
Micrel, Inc.
November 2006
ceramic
capacitors
provide
optimal
10
large capacitor on the bypass pin without significantly
slowing turn-on time. Refer to the “ Typical Character-
istics ” section for performance with different bypass
capacitors.
Active Shutdown
The MIC5255 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 MIC5255 will remain stable and in regulation with no
load unlike many other voltage regulators. This is
especially
applications.
Thermal Considerations
The MIC5255 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:
T
125°C, and T
is layout dependent; Table 1 shows examples of
junction-to-ambient thermal resistance for the MIC5255.
The actual power dissipation of the regulator circuit can
be determined using the equation:
Substituting P
conditions that are critical to the application will give the
maximum operating conditions for the regulator circuit.
For example, when operating the MIC5255-3.0BM5 at
50°C with a minimum footprint layout, the maximum
input voltage for a set output current can be determined
as follows:
(M5 or D5)
Package
SOT23-5
J(max)
is the maximum junction temperature of the die,
P
P
P
P
D
D(max)
D(max)
D(max)
Table 1. SOT-23-5 Thermal Resistance
= (V
important
Minimum Footprint
A
θ
D(max)
JA
= 315mW
is the ambient operating temperature. θ
IN
=
=
Recommended
– V
⎛
⎜
⎜
⎝
⎛
⎜
⎝
235°C/W
125
T
for P
J(max)
OUT
235
°
θ
C
) I
JA
in
D
°
−
C/W
OUT
−
and solving for the operating
50
T
CMOS
A
+ V
°
C
⎞
⎟
⎟
⎠
⎞
⎟
⎠
IN
θ
Copper Clad
I
JA
GND
185°C/W
1” Square
RAM
M9999-110906
MIC5255
keep-alive
145°C/W
θ
JC
JA