MIC37100-2.5WS Micrel Inc, MIC37100-2.5WS Datasheet - Page 12

• Manufacturer Part Number: MIC37100-2.5WS
• Description: IC REG LDO 1A 2.5V SOT223
• Manufacturer: Micrel Inc

Specifications of MIC37100-2.5WS

• Regulator Topology: Positive Fixed
• Voltage - Output: 2.5V
• Voltage - Input: Up to 6V
• Voltage - Dropout (typical): 0.28V @ 1A
• Number Of Regulators: 1
• Current - Output: 1A (Min)
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: SOT-223 (3 leads + Tab), SC-73, TO-261
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Limit (min): -
• Other names: 576-1162

without operating in dropout, NPN-based regulators
require an input voltage of 3.7V at the very least. The
MIC37100 regulator will provide excellent performance
with an input as low as 3.0V or 2.5V respectively. This
gives the PNP based regulators a distinct advantage
over older, NPN based linear regulators.
Minimum Load Current
The MIC37100/01/02 regulator is specified between
finite loads. If the output current is too small, leakage
currents dominate and the output voltage rises. A 10mA
minimum load current is necessary for proper regulation.
Adjustable Regulator Design
The MIC37102 allows programming the output voltage
anywhere between 1.24V and the 6V maximum
operating rating of the family. Two resistors are used.
Resistors can be quite large, up to 1MΩ, because of the
very high input impedance and low bias current of the
sense comparator. The resistor values are calculated by:
Where V
component definition. Applications with widely varying
load currents may scale the resistors to draw the
minimum load current required for proper operation (see
above).
Power SOIC-8 Thermal Characteristics
One of the secrets of the MIC37101/02’s performance is
its power SO-8 package featuring half the thermal
resistance of a standard SO-8 package. Lower thermal
resistance means more output current or higher input
voltage for a given package size.
Lower thermal resistance is achieved by joining the four
ground leads with the die attach paddle to create a
single-piece electrical and thermal conductor. This
concept has been used by MOSFET manufacturers for
years, proving very reliable and cost effective for the
user.
Micrel, Inc.
September 2007
SHUTDOWN
Figure 2. Adjustable Regulator with Resistors
ENABLE
R1
O
is the desired output voltage. Figure 2 shows
=
V
R2
IN
⎛
⎜ ⎜
⎝
V
1.240
V
OUT
OUT
IN
EN
MIC37102
=
−
1.240V
GND
1
⎞
⎟ ⎟
⎠
OUT
ADJ
⎛
⎜
⎝
1
+
R2
R1
R1
R2
⎞
⎟
⎠
C
OUT
V
OUT
12
Thermal resistance consists of two main elements, θ
(junction-to-case thermal resistance) and θ
ambient thermal resistance). See Figure 3. θ
resistance from the die to the leads of the package. θ
is the resistance from the leads to the ambient air and it
includes θ
(sink-to-ambient thermal resistance).
Using the power SOIC-8 reduces the θ
and allows the user to reduce θ
resistance, θ
is the limiting factor in calculating the maximum power
dissipation capability of the device. Typically, the power
SOIC-8 has a θ
than the standard SOIC-8 which is typically 75°C/W. θ
is reduced because pins 5 through 8 can now be
soldered directly to a ground plane which significantly
reduces the case-to-sink thermal resistance and sink to
ambient thermal resistance.
Low-dropout linear regulators from Micrel are rated to a
maximum junction temperature of 125°C. It is important
not to exceed this maximum junction temperature during
operation of the device. To prevent this maximum
junction
appropriate ground plane heat sink must be used.
Figure 4. Copper Area vs. Power SO-8
temperature
CS
JA
(case-to-sink thermal resistance) and θ
Figure 3. Thermal Resistance
700
600
500
400
300
200
100
(junction-to-ambient thermal resistance)
printed circuit board
JC
0
SOIC-8
0
of 20°C/W, this is significantly lower
Power Dissipation
POWER DISSIPATION (W)
T
0.25 0.50 0.75 1.00 1.25 1.50
JA
JC
=
from
JA
CA
MIC37100/37101/37102
being
AMBIENT
CA
. The total thermal
heat sink area
ground plane
exceeded,
JC
M9999-090607
CA
dramatically
(case-to-
JC
is the
the
CA
CA
SA
JC