MIC5209-2.5BS Micrel Inc, MIC5209-2.5BS Datasheet - Page 10

• Manufacturer Part Number: MIC5209-2.5BS
• Description: IC REG LDO 500MA 2.5V LN SOT223
• Manufacturer: Micrel Inc

Specifications of MIC5209-2.5BS

• Mounting Type: Surface Mount
• Regulator Topology: Positive Fixed
• Voltage - Output: 2.5V
• Voltage - Input: Up to 16V
• Voltage - Dropout (typical): 0.35V @ 500mA
• Number Of Regulators: 1
• Current - Output: 500mA
• Operating Temperature: -40°C ~ 125°C
• Package / Case: SOT-223 (3 leads + Tab), SC-73, TO-261
• No. Of Pins: 3
• Voltage Regulator Type: LDO Linear
• Output Current Max: 500mA
• Peak Reflow Compatible (260 C): No
• Current Rating: 500mA
• Output Voltage Max: 2.5V
• Leaded Process Compatible: No
• Rohs Compliant: No
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Limit (min): -
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant, Contains lead / RoHS non-compliant

Fixed Regulator Circuits
Figure 1 shows a basic MIC5209-x.xBM (SO-8) fi xed-voltage
regulator circuit. See Figure 5 for a similar confi guration us-
ing the more thermally-effi cient MIC5209-x.xBS (SOT-223).
A 1µF minimum output capacitor is required for basic fi xed-
voltage applications.
Figure 2 includes the optional 470pF noise bypass capacitor
between BYP and GND to reduce output noise. Note that the
minimum value of C
capacitor is used.
Adjustable Regulator Circuits
The MIC5209BM/U can be adjusted to a specifi c output volt-
age by using two external resistors (Figure 3). The resistors
set the output voltage based on the equation:
This equation is correct due to the confi guration of the
bandgap reference. The bandgap voltage is relative to the
output, as seen in the block diagram. Traditional regula-
tors normally have the reference voltage relative to ground;
therefore, their equations are different from the equation for
the MIC5209BM/U.
Although ADJ is a high-impedance input, for best performance,
R2 should not exceed 470kΩ.
M9999-060906
Figure 2. Ultra-Low-Noise Fixed Voltage Regulator
Figure 3. Low-Noise Adjustable Voltage Regulator
Figure 1. Low-Noise Fixed Voltage Regulator
V
V
V
OUT
OUT
V
IN
= 1.242V
V
IN
V
IN
2
1
MIC5209-x.xBM
2
1
I I N N
E E N N
MIC5209BM
OUT
I I N N
E E N N
MIC5209-x.xBM
2
1
I I N N
EN
GND









5–8
1
must be increased when the bypass
GND
5–8
+
GND
OUT
OUT
ADJ
ADJ
OUT
OUT
BYP
BYP
R2
R1
5–8
OUT
OUT
BYP
470pF






 


3
4
3
4
R1
R2
3
4
1µF
V
2.2µF
OUT
V
1µF
OUT
V
OUT
10
Figure 4 includes the optional 470pF bypass capacitor from
ADJ to GND to reduce output noise.
Slot-1 Power Supply
Intel’s Pentium II processors have a requirement for a 2.5V
±5% power supply for a clock synthesizer and its associated
loads. The current requirement for the 2.5V supply is depen-
dant upon the clock synthesizer used, the number of clock
outputs, and the type of level shifter (from core logic levels to
2.5V levels). Intel estimates a worst-case load of 320mA.
The MIC5209 was designed to provide the 2.5V power
requirement for Slot-1 applications. Its guaranteed perfor-
mance of 2.5V ±3% at 500mA allows adequate margin for
all systems, and its dropout voltage of 500mV means that it
operates from a worst-case 3.3V supply where the voltage
can be as low as 3.0V.
A Slot-1 power supply (Figure 5) is easy to implement. Only
two capacitors are necessary, and their values are not criti-
cal. C
0.1µF. C
response, and compensates the internal regulator control
loop. Its value should be at least 22µF. C
be increased as much as desired.
Slot-1 Power Supply Power Dissipation
Powered from a 3.3V supply, the Slot-1 power supply of
Figure 5 has a nominal effi ciency of 75%. At the maximum
anticipated Slot 1 load (320mA), the nominal power dissipa-
tion is only 256mW.
The SOT-223 package has suffi cient thermal characteristics
for wide design margins when mounted on a single layer
copper-clad printed circuit board. The power dissipation of
the MIC5209 is calculated using the voltage drop across the
device × output current plus supply voltage × ground current.
Figure 4. Ultra-Low-Noise Adjustable Application.
IN
bypasses the internal circuitry and should be at least
OUT
V
IN
0.1µF
Figure 5. Slot-1 Power Supply
provides output fi ltering, improves transient
V
C
2
1
IN
IN
EN
IN
MIC5209BM
GND
MIC5209-x.xBS
1
5–8
I I N N
OUT
ADJ
470pF
GND
3
4
2,TAB
OUT
OUT
3
R1
R2
C
22µF
V
IN
OUT
OUT
and C
2.2µF
V
OUT
June 2006
OUT
may