February 2006 1 M9999-022106
MIC5209 Micrel, Inc.
Typical Applications
1 32
0.1µF 22µF
tantalum
VOUT
2.5V ±1%
VIN
≥ 3.0V
MIC5209-2.5BS
3.3V Nominal-Input Slot-1
Power Supply
1
2
3
4
8
7
6
5
MIC5209-5.0BM
2.2µF
tantalum
VOUT
5V
470pF
(OPTIONAL)
VIN
6V
ENABLE
SHUTDOWN
Ultra-Low-Noise 5V Regulator
MIC5209
500mA Low-Noise LDO Regulator
General Description
The MIC5209 is an efficient linear voltage regulator with very
low dropout voltage, typically 10mV at light loads and less
than 500mV at full load, with better than 1% output voltage
accuracy.
Designed especially for hand-held, battery-powered devices,
the MIC5209 features low ground current to help prolong
battery life. An enable/shutdown pin on SO-8 and TO-263-
5 versions can further improve battery life with near-zero
shutdown current.
Key features include reversed-battery protection, current
limiting, overtemperature shutdown, ultra-low-noise capability
(SO-8 and TO-263-5 versions), and availability in thermally
efficient packaging. The MIC5209 is available in adjustable
or fixed output voltages.
For space-critical applications where peak currents do not
exceed 500mA, see the MIC5219.
Features
• Meets Intel® Slot 1 and Slot 2 requirements
• Guaranteed 500mA output over the full operating
temperature range
• Low 500mV maximum dropout voltage at full load
• Extremely tight load and line regulation
• Thermally-efficient surface-mount package
• Low temperature coefficient
• Current and thermal limiting
• Reversed-battery protection
• No-load stability
• 1% output accuracy
• Ultra-low-noise capability in SO-8 and TO-263-5
• Ultra-small 3mm x 3mm MLF™ package
Applications
• Pentium II Slot 1 and Slot 2 support circuits
• Laptop, notebook, and palmtop computers
• Cellular telephones
• Consumer and personal electronics
• SMPS post-regulator/dc-to-dc modules
• High-efficiency linear power supplies
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
MIC5209 Micrel, Inc.
M9999-022106 2 February 2006
Ordering Information
Part Number Voltage Junction Temp. Range Package Pb-Free
MIC5209-2.5BS 2.5V -40°C to +125°C SOT-223
MIC5209-2.5YS 2.5V -40°C to +125°C SOT-223 X
MIC5209-3.0BS 3.0V -40°C to +125°C SOT-223
MIC5209-3.0YS 3.0V -40°C to +125°C SOT-223 X
MIC5209-3.3BS 3.3V -40°C to +125°C SOT-223
MIC5209-3.3YS 3.3V -40°C to +125°C SOT-223 X
MIC5209-3.6BS 3.6V -40°C to +125°C SOT-223
MIC5209-3.6YS 3.6V -40°C to +125°C SOT-223 X
MIC5209-4.2BS 4.2V -40°C to +125°C SOT-223
MIC5209-4.2YS 4.2V -40°C to +125°C SOT-223 X
MIC5209-5.0BS 5.0V -40°C to +125°C SOT-223
MIC5209-5.0YS 5.0V -40°C to +125°C SOT-223 X
MIC5209-1.8BM* 1.8V -0°C to +125°C SOIC-8
MIC5209-1.8YM* 1.8V -0°C to +125°C SOIC-8 X
MIC5209-2.5BM 2.5V -40°C to +125°C SOIC-8
MIC5209-2.5YM 2.5V -40°C to +125°C SOIC-8 X
MIC5209-3.0BM 3.0V -40°C to +125°C SOIC-8
MIC5209-3.0YM 3.0V -40°C to +125°C SOIC-8 X
MIC5209-3.3BM 3.3V -40°C to +125°C SOIC-8
MIC5209-3.3YM 3.3V -40°C to +125°C SOIC-8 X
MIC5209-3.6BM 3.6V -40°C to +125°C SOIC-8
MIC5209-3.6YM 3.6V -40°C to +125°C SOIC-8 X
MIC5209-5.0BM 5.0V -40°C to +125°C SOIC-8
MIC5209-5.0YM 5.0V -40°C to +125°C SOIC-8 X
MIC5209BM Adj. -40°C to +125°C SOIC-8
MIC5209YM Adj. -40°C to +125°C SOIC-8 X
MIC5209-1.8YU* 1.8V -0°C to +125°C TO-263-5 X
MIC5209-2.5BU 2.5V -40°C to +125°C TO-263-5
MIC5209-2.5YU 2.5V -40°C to +125°C TO-263-5 X
MIC5209-3.0BU 3.0V -40°C to +125°C TO-263-5
MIC5209-3.0YU 3.0V -40°C to +125°C TO-263-5 X
MIC5209-3.3BU 3.3V -40°C to +125°C TO-263-5
MIC5209-3.3YU 3.3V -40°C to +125°C TO-263-5 X
MIC5209-3.6BU 3.6V -40°C to +125°C TO-263-5
MIC5209-3.6YU 3.6V -40°C to +125°C TO-263-5 X
MIC5209-5.0BU 5.0V -40°C to +125°C TO-263-5
MIC5209-5.0YU 5.0V -40°C to +125°C TO-263-5 X
MIC5209BU Adj. -40°C to +125°C TO-263-5
MIC5209YU Adj. -40°C to +125°C TO-263-5 X
MIC5209YML Adj. -40°C to +125°C 8-pin MLF™ X
* Contact marketing for availability.
February 2006 3 M9999-022106
MIC5209 Micrel, Inc.
1
2
3
4
8
7
6
5
GND
GND
GND
GND
EN
IN
OUT
BYP
MIC5209-x.xBM
SO-8
Fixed Voltages
1
2
3
4
8
7
6
5
GND
GND
GND
GND
EN
IN
OUT
ADJ
MIC5209BM
SO-8
Adjustable Voltage
Pin Description
Pin No.
8-pin MLF
Pin No.
SOT-223
Pin No.
SO-8
Pin No.
TO-263-5
Pin Name Pin Function
1, 2 1 2 2 IN Supply Input.
7 2, TAB 5–8 3 GND Ground: SOT-223 pin 2 and TAB are internally connected. SO-8
pins 5 through 8 are internally connected.
3, 4 3 3 4 OUT Regulator Output. Pins 3 and 4 must be tied together.
8 1 1 EN Enable (Input): CMOS compatible control input. Logic high =
enable; logic low = shutdown.
4 (fixed) 5 (fixed) BYP Reference Bypass: Connect external 470pF capacitor to GND to
reduce output noise. May be left open. For 1.8V or 2.5V operation,
see “Applications Information.”
6 4 (adj.) 5 (adj.) ADJ Adjust (Input): Feedback input. Connect to resistive voltage-divider
network.
5 BYP
4 OUT
3 GND
2 IN
1 EN
DNG
BAT
MIC5209-x.xBU
TO-263-5
Fixed Voltages
5 ADJ
4 OUT
3 GND
2 IN
1 EN
DNG
BAT
MIC5209BU
TO-263-5
Adjustable Voltage
Pin Configuration
IN OUTGND
1 32
TAB
GND
MIC5209-x.xBS
SOT-223
Fixed Voltages
1VIN
VIN
VOUT
VOUT
8 EN
GND
ADJ
NC
7
6
5
2
3
4
5209
YWW
Y
Part
Identification
MIC5209YML
8-Pin 3x3 MLF
Adjustable Voltages
MIC5209 Micrel, Inc.
M9999-022106 4 February 2006
Electrical Characteristics (Note 11)
VIN = VOUT + 1.0V; COUT = 4.7µF, IOUT = 100µA; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C except 0°C ≤ TJ ≤ +125°C
for 1.8V version; unless noted.
Symbol Parameter Conditions Min Typical Max Units
VOUT Output Voltage Accuracy variation from nominal VOUT –1 1 %
–2 2 %
ΔVOUT/ΔT Output Voltage Note 4 40 ppm/°C
Temperature Coefficient
ΔVOUT/VOUT Line Regulation VIN = VOUT + 1V to 16V 0.009 0.05 %/V
0.1 %/V
ΔVOUT/VOUT Load Regulation IOUT = 100µA to 500mA(5) 0.05 0.5 %
0.7 %
VIN – VOUT Dropout Voltage(6) IOUT = 100µA 10 60 mV
80 mV
IOUT = 50mA 115 175 mV
250 mV
IOUT = 150mA 165 300 mV
400 mV
IOUT = 500mA 350 500 mV
600 mV
IGND Ground Pin Current(7, 8) VEN ≥ 3.0V, IOUT = 100µA 80 130 µA
170 µA
VEN ≥ 3.0V, IOUT = 50mA 350 650 µA
900 µA
VEN ≥ 3.0V, IOUT = 150mA 1.8 2.5 mA
3.0 mA
VEN ≥ 3.0V, IOUT = 500mA 8 20 mA
25 mA
IGND Ground Pin Quiescent Current(8) VEN ≤ 0.4V (shutdown) 0.05 3 µA
VEN ≤ 0.18V (shutdown) 0.10 8 µA
PSRR Ripple Rejection f = 120Hz 75 dB
ILIMIT Current Limit VOUT = 0V 700 900 mA
1000 mA
ΔVOUT/ΔPD Thermal Regulation Note 9 0.05 %/W
eno Output Noise(10) VOUT = 2.5V, IOUT = 50mA, 500 nV √Hz
COUT = 2.2µF, CBYP = 0
IOUT = 50mA, COUT = 2.2µF, CBYP = 470pF 300 nV √Hz
Absolute Maximum Ratings(1)
Supply Input Voltage (VIN) ..............................–20V to +20V
Power Dissipation (PD) ..........................Internally Limited(3)
Junction Temperature (TJ)
all except 1.8V ...................................... –40°C to +125°C
1.8V only ................................................... 0°C to +125°C
Lead Temperature (soldering, 5 sec.) ........................ 260°C
Storage Temperature (TS) ........................ –65°C to +150°C
Operating Ratings(2)
Supply Input Voltage (VIN) ............................ +2.5V to +16V
Enable Input Voltage (VEN) ...................................0V to VIN
Junction Temperature (TJ)
all except 1.8V ...................................... –40°C to +125°C
1.8V only ................................................... 0°C to +125°C
Package Thermal Resistance ................................... Note 3
February 2006 5 M9999-022106
MIC5209 Micrel, Inc.
ENABLE Input
VENL Enable Input Logic-Low Voltage VEN = logic low (regulator shutdown) 0.4 V
0.18 V
VEN = logic high (regulator enabled) 2.0 V
IENL Enable Input Current VENL ≤ 0.4V 0.01 –1 µA
VENL ≤ 0.18V 0.01 –2 µA
IENH VENH ≥ 2.0V 5 20 µA
25 µA
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. The maximum allowable power dissipation at any TA (ambient temperature) is calculated using: PD(max) = (TJ(max) – TA) ÷ θJA. Exceeding the
maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. See Table 1 and the
“Thermal Considerations” section for details.
4. Output voltage temperature coefficient is the worst case voltage change divided by the total temperature range.
5. Regulation is measured at constant junction temperature using low duty cycle pulse testing. Parts are tested for load regulation in the load range
from 100µA to 500mA. Changes in output voltage due to heating effects are covered by the thermal regulation specification.
6. Dropout voltage is defined as the input to output differential at which the output voltage drops 2% below its nominal value measured at 1V differen-
tial.
7. Ground pin current is the regulator quiescent current plus pass transistor base current. The total current drawn from the supply is the sum of the load
current plus the ground pin current.
8. VEN is the voltage externally applied to devices with the EN (enable) input pin. [SO-8 (M) and TO-263-5 (U) packages only.]
9. Thermal regulation is the change in output voltage at a time “t” after a change in power dissipation is applied, excluding load or line regulation ef-
fects. Specifications are for a 500mA load pulse at VIN = 16V for t = 10ms.
10. CBYP is an optional, external bypass capacitor connected to devices with a BYP (bypass) or ADJ (adjust) pin. [SO-8 (M) and TO-263-5 (U) packages
only].
11. specification for packaged product only.
MIC5209 Micrel, Inc.
M9999-022106 6 February 2006
Block Diagrams
Current Limit
Thermal Shutdown
IN OUT
GND
Bandgap
Ref.
C
OUT
V
OUT
V
IN
MIC5209-x.xBS
Low-Noise Fixed Regulator (SOT-223 version only)
Ultra-Low-Noise Fixed Regulator
IN
EN
OUT
CBYP
(optional)
GND
VREF
Bandgap
Ref.
Current Limit
Thermal Shutdown
COUT
VOUT
VIN
R1
R2
MIC5209BM/U [adj.]
ADJ
Ultra-Low-Noise Adjustable Regulator
February 2006 7 M9999-022106
MIC5209 Micrel, Inc.
Typical Characteristics
-100
-80
-60
-40
-20
0
1E+1 1E+21E+31E+41E+51E+61E+7
)B
d(
RR
S
P
FREQUENCY (Hz)
Power Supply
Rejection Ratio
IOUT = 100µA
COUT = 1µF
VIN = 6V
VOUT = 5V
10 100 1k 10k 100k 1M 10M
-100
-80
-60
-40
-20
0
1E+11E+21E+31E+41E+51E+61E+7
)B
d(
RR
S
P
FREQUENCY (Hz)
Power Supply
Rejection Ratio
I
OUT
= 1mA
C
OUT
= 1µF
V
IN
= 6V
V
OUT
= 5V
10 100 1k 10k 100k 1M 10M -100
-80
-60
-40
-20
0
1E+11E+21E+31E+41E+51E+61E+7
)Bd(RRSP
FREQUENCY (Hz)
Power Supply
Rejection Ratio
I
OUT
= 100mA
C
OUT
= 1µF
V
IN
= 6V
V
OUT
= 5V
10 100 1k 10k 100k 1M 10M
-100
-80
-60
-40
-20
0
1E+1 1E+21E+31E+41E+51E+61E+7
)B
d(
RR
S
P
FREQUENCY (Hz)
Power Supply
Rejection Ratio
IOUT = 100µA
COUT = 2.2µF
CBYP = 0.01µF
VIN = 6V
VOUT = 5V
10 100 1k 10k 100k 1M 10M
-100
-80
-60
-40
-20
0
1E+11E+21E+31E+41E+51E+61E+7
)B
d(
RR
S
P
FREQUENCY (Hz)
Power Supply
Rejection Ratio
I
OUT
= 1mA
C
OUT
= 2.2µF
C
BYP
= 0.01µF
V
IN
= 6V
V
OUT
= 5V
10 100 1k 10k 100k 1M 10M -100
-80
-60
-40
-20
0
1E+11E+21E+31E+41E+51E+61E+7
)Bd(RRSP
FREQUENCY (Hz)
Power Supply
Rejection Ratio
I
OUT
= 100mA
C
OUT
= 2.2µF
C
BYP
= 0.01µF
V
IN
= 6V
V
OUT
= 5V
10 100 1k 10k 100k 1M 10M
0
10
20
30
40
50
60
0 0.1 0.2 0.3 0.4
)Bd(N
OI
T
CE
JE
RELPPI
R
VOLTAGE DROP (V)
Power Supply Ripple Rejection
vs. Voltage Drop
I
OUT
= 100mA
10mA
1mA
C
OUT
= 1µF
0
10
20
30
40
50
60
70
80
90
100
0 0.1 0.2 0.3 0.4
)Bd(NOITCE
J
E
R
EL
PP
I
R
VOLTAGE DROP (V)
Power Supply Ripple Rejection
vs. Voltage Drop
IOUT = 100mA
10mA
1mA
COUT = 2.2µF
CBYP = 0.01µF
0.0001
0.001
0.01
0.1
1
10
1E+11E+21E+31E+41E+51E+61E+7
(ESION µ/V √)zH
FREQUENCY (Hz)
Noise Performance
10 100 1k 10k 100k 1M 10M
10mA, C
OUT = 1µF
VOUT = 5V
0.0001
0.001
0.01
0.1
1
10
1E+11E+21E+31E+41E+51E+61E+7
(ESION µ/V
√
)zH
FREQUENCY (Hz)
Noise Performance
10mA
1mA
100mA
10 100 1k 10k 100k 1M 10M
V
OUT
= 5V
C
OUT
= 10µF
electrolytic
0.0001
0.001
0.01
0.1
1
10
1E+11E+21E+31E+41E+51E+61E+7
(ESION µ/V
√
)zH
FREQUENCY (Hz)
Noise Performance
10mA
1mA
100mA
10 100 1k 10k 100k 1M 10M
VOUT = 5V
COUT = 10µF
electrolytic
CBYP = 100pF
0
100
200
300
400
0 100 200 300 400 500
)Vm(
E
GATLOVTUOPORD
OUTPUT CURRENT (mA)
Dropout Voltage
vs. Output Current
MIC5209 Micrel, Inc.
M9999-022106 8 February 2006
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0 1 2 3 4 5 6 7 8 9
)V(E
G
ATL
O
VTU
P
TUO
INPUT VOLTAGE (V)
Dropout Characteristics
IL =100µA
IL=100mA
IL=500mA
0
2
4
6
8
10
12
0 100 200 300 400 500
)Am(TNERRUCDNUORG
OUTPUT CURRENT (mA)
Ground Current
vs. Output Current
0
5
10
15
20
25
0 1 2 3 4 5 6 7 8 9
)A
m
(TN
ER
RUCD
NU
ORG
INPUT VOLTAGE (V)
Ground Current
vs. Supply Voltage
IL=500mA
0
0.5
1.0
1.5
2.0
2.5
3.0
0 2 4 6 8
)Am(TNERRUCDNUORG
INPUT VOLTAGE (V)
Ground Current
vs. Supply Voltage
IL=100 mA
IL=100µ
A
February 2006 9 M9999-022106
MIC5209 Micrel, Inc.
Applications Information
Enable/Shutdown
Enable is available only on devices in the SO-8 (M) and
TO-263-5 (U) packages.
Forcing EN (enable/shutdown) high (> 2V) enables the regula-
tor. EN is compatible with CMOS logic. If the enable/shutdown
feature is not required, connect EN to IN (supply input).
Input Capacitor
A 1µF capacitor should be placed from IN to GND if there is
more than 10 inches of wire between the input and the ac
filter capacitor or if a battery is used as the input.
Output Capacitor
An output capacitor is required between OUT and GND to
prevent oscillation. The minimum size of the output capacitor
is dependent upon whether a reference bypass capacitor is
used. 1µF minimum is recommended when CBYP is not used
(see Figure 1). 2.2µF minimum is recommended when CBYP
is 470pF (see Figure 2). Larger values improve the regulator’s
transient response.
The output capacitor should have an ESR (equivalent series
resistance) of about 1Ω and a resonant frequency above
1MHz. Ultra-low-ESR capacitors can cause a low amplitude
oscillation on the output and/or underdamped transient re-
sponse. Most tantalum or aluminum electrolytic capacitors
are adequate; film types will work, but are more expensive.
Since many aluminum electrolytics have electrolytes that
freeze at about –30°C, solid tantalums are recommended
for operation below –25°C.
At lower values of output current, less output capacitance
is needed for output stability. The capacitor can be reduced
to 0.47µF for current below 10mA or 0.33µF for currents
below 1mA.
No-Load Stability
The MIC5209 will remain stable and in regulation with no load
(other than the internal voltage divider) unlike many other
voltage regulators. This is especially important in CMOS
RAM keep-alive applications.
Reference Bypass Capacitor
BYP (reference bypass) is available only on devices in SO-8
and TO-263-5 packages.
BYP is connected to the internal voltage reference. A 470pF
capacitor (CBYP) connected from BYP to GND quiets this
reference, providing a significant reduction in output noise
(ultra-low-noise performance). Because CBYP reduces the
phase margin, the output capacitor should be increased to
at least 2.2µF to maintain stability.
The start-up speed of the MIC5209 is inversely proportional
to the size of the reference bypass capacitor. Applications
requiring a slow ramp-up of output voltage should consider
larger values of CBYP. Likewise, if rapid turn-on is necessary,
consider omitting CBYP.
If output noise is not critical, omit CBYP and leave BYP
open.
Thermal Considerations
The SOT-223 has a ground tab which allows it to dissipate
more power than the SO-8. Refer to “Slot-1 Power Supply”
for details. At 25°C ambient, it will operate reliably at 2W
dissipation with “worst-case” mounting (no ground plane,
minimum trace widths, and FR4 printed circuit board).
Thermal resistance values for the SO-8 represent typical
mounting on a 1”-square, copper-clad, FR4 circuit board.
For greater power dissipation, SO-8 versions of the MIC5209
feature a fused internal lead frame and die bonding arrange-
ment that reduces thermal resistance when compared to
standard SO-8 packages.
Package θJA θJC
SOT-223 (S) 50°C/W 8°C/W
SO-8 (M) 50°C/W 20°C/W
TO-263-5 (U) — 2°C/W
3x3 MLF (ML) 63°C/W 2°C/W
Table 1. MIC5209 Thermal Resistance
Multilayer boards with a ground plane, wide traces near the
pads, and large supply-bus lines will have better thermal con-
ductivity and will also allow additional power dissipation.
For additional heat sink characteristics, please refer to Mi-
crel Application Hint 17, “Designing P.C. Board Heat Sinks”,
included in Micrel’s Databook. For a full discussion of heat
sinking and thermal effects on voltage regulators, refer to
Regulator Thermals section of Micrel’s Designing with Low-
Dropout Voltage Regulators handbook.
Low-Voltage Operation
The MIC5209-1.8 and MIC5209-2.5 require special con-
sideration when used in voltage-sensitive systems. They
may momentarily overshoot their nominal output voltages
unless appropriate output and bypass capacitor values are
chosen.
During regulator power up, the pass transistor is fully satu-
rated for a short time, while the error amplifier and voltage
reference are being powered up more slowly from the output
(see “Block Diagram”). Selecting larger output and bypass
capacitors allows additional time for the error amplifier and
reference to turn on and prevent overshoot.
To ensure that no overshoot is present when starting up into
a light load (100µA), use a 4.7µF output capacitance and
470pF bypass capacitance. This slows the turn-on enough
to allow the regulator to react and keep the output voltage
from exceeding its nominal value. At heavier loads, use a
10µF output capacitance and 470pF bypass capacitance.
Lower values of output and bypass capacitance can be used,
depending on the sensitivity of the system.
Applications that can withstand some overshoot on the output
of the regulator can reduce the output capacitor and/or reduce
or eliminate the bypass capacitor. Applications that are not
sensitive to overshoot due to power-on reset delays can use
normal output and bypass capacitor configurations.
Please note the junction temperature range of the regulator
at 1.8V output (fixed and adjustable) is 0˚C to +125˚C.
MIC5209 Micrel, Inc.
M9999-022106 10 February 2006
Fixed Regulator Circuits
MIC5209-x.xBM
IN OUT
GND
1µF
V
IN
V
OUT
EN BYP
1
2
5–8
3
4
Figure 1. Low-Noise Fixed Voltage Regulator
Figure 1 shows a basic MIC5209-x.xBM (SO-8) fixed-voltage
regulator circuit. See Figure 5 for a similar configuration us-
ing the more thermally-efficient MIC5209-x.xBS (SOT-223).
A 1µF minimum output capacitor is required for basic fixed-
voltage applications.
MIC5209-x.xBM
IN OUT
GND
470pF
V
IN
EN BYP
1
2
5–8
3
4
2.2µF
V
OUT
Figure 2. Ultra-Low-Noise Fixed Voltage Regulator
Figure 2 includes the optional 470pF noise bypass capacitor
between BYP and GND to reduce output noise. Note that the
minimum value of COUT must be increased when the bypass
capacitor is used.
Adjustable Regulator Circuits
MIC5209BM
IN OUT
GND
VIN
EN ADJ
1
2
5–8
3
4
1µF
VOUT
R1
R2
Figure 3. Low-Noise Adjustable Voltage Regulator
The MIC5209BM/U can be adjusted to a specific output volt-
age by using two external resistors (Figure 3). The resistors
set the output voltage based on the equation:
V = 1.242V + R2
R1
OUT 1
This equation is correct due to the configuration 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.
MIC5209BM
IN OUT
GND
V
IN
EN ADJ
1
2
5–8
3
4
2.2µF
V
OUT
R1
R2
470pF
Figure 4. Ultra-Low-Noise Adjustable Application.
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.
MIC5209-x.xBS
IN OUT
GND
COUT
22µF
VIN VOUT
1
2,TAB
3
CIN
0.1µF
Figure 5. Slot-1 Power Supply
A Slot-1 power supply (Figure 5) is easy to implement. Only
two capacitors are necessary, and their values are not criti-
cal. CIN bypasses the internal circuitry and should be at least
0.1µF. COUT provides output filtering, improves transient
response, and compensates the internal regulator control
loop. Its value should be at least 22µF. CIN and COUT may
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 efficiency of 75%. At the maximum
anticipated Slot 1 load (320mA), the nominal power dissipa-
tion is only 256mW.
The SOT-223 package has sufficient 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.
February 2006 11 M9999-022106
MIC5209 Micrel, Inc.
Considering worst case tolerances, the power dissipation
could be as high as:
(VIN(max) – VOUT(max)) × IOUT + VIN(max) × IGND
[(3.6V – 2.375V) × 320mA] + (3.6V × 4mA)
PD = 407mW
Using the maximum junction temperature of 125°C and a θJC
of 8°C/W for the SOT-223, 25°C/W for the SO-8, or 2°C/W
for the TO-263 package, the following worst-case heat-sink
thermal resistance (θSA) requirements are:
θJA
J(max) A
D
T T
P
=−
θSA = θJA = θJC
TA 40°C 50°C 60°C 75°C
θJA (limit) 209°C/W 184°C/W 160°C/W 123°C/W
θSA SOT-223 201°C/W 176°C/W 152°C/W 115°C/W
θSA SO-8 184°C/W 159°C/W 135°C/W 98°C/W
θSA TO-263-5 207°C/W 182°C/W 158°C/W 121°C/W
Table 2. Maximum Allowable Thermal Resistance
Table 2 and Figure 6 show that the Slot-1 power supply ap-
plication can be implemented with a minimum footprint layout.
Figure 6 shows the necessary copper pad area to obtain
specific heat sink thermal resistance (θSA) values. The θSA
values in Table 2 require much less than 500mm2 of copper,
according to Figure 6, and can easily be accomplished with
the minimum footprint.
0
10
20
30
40
50
60
70
0 2000 4000 6000
COPPER HEAT SINK AREA (mm
2)
Figure 6. PCB Heat Sink Thermal Resistance
MIC5209 Micrel, Inc.
M9999-022106 12 February 2006
Package Information
SOT-223 (S)
8-Pin SOIC (M)
February 2006 13 M9999-022106
MIC5209 Micrel, Inc.
MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's
use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2004 Micrel Incorporated
1
θ
θ1
3
θ
4θ
1
θ
2
θ
3
θ4θ
2θ1θ
TO-263-5 (U)
8-Pin 3mm x 3mm MLF (ML)