June 2009 1 M0371-061809
Micrel, Inc. MIC5219
Typical Applications
MIC5219
500mA-Peak Output LDO Regulator
General Description
The MIC5219 is an efcient linear voltage regulator with high
peak output current capability, very-low-dropout voltage, and
better than 1% output voltage accuracy. Dropout is typically
10mV at light loads and less than 500mV at full load.
The MIC5219 is designed to provide a peak output current for
start-up conditions where higher inrush current is demanded.
It features a 500mA peak output rating. Continuous output
current is limited only by package and layout.
The MIC5219 can be enabled or shut down by a CMOS or
TTL compatible signal. When disabled, power consumption
drops nearly to zero. Dropout ground current is minimized to
help prolong battery life. Other key features include reversed-
battery protection, current limiting, overtemperature shutdown,
and low noise performance with an ultra-low-noise option.
The MIC5219 is available in adjustable or xed output volt-
ages in the space-saving 6-pin (2mm × 2mm) MLF®, 6-pin
(2mm × 2mm) Thin MLF® SOT-23-5 and MM8® 8-pin power
MSOP packages. For higher power requirements see the
MIC5209 or MIC5237.
All support documentation can be found on Micrel’s web site
at www.micrel.com.
Features
• 500mA output current capability
SOT-23-5 package - 500mA peak
2mm×2mm MLF® package - 500mA continuous
2mm×2mm Thin MLF® package - 500mA
continuous
MSOP-8 package - 500mA continuous
• Low 500mV maximum dropout voltage at full load
• Extremely tight load and line regulation
• Tiny SOT-23-5 and MM8™ power MSOP-8 package
• Ultra-low-noise output
• Low temperature coefcient
• Current and thermal limiting
• Reversed-battery protection
• CMOS/TTL-compatible enable/shutdown control
• Near-zero shutdown current
Applications
• Laptop, notebook, and palmtop computers
• Cellular telephones and battery-powered equipment
• Consumer and personal electronics
• PC Card VCC and VPP regulation and switching
• SMPS post-regulator/DC-to-DC modules
• High-efciency linear power supplies
1
2
3
4
8
7
6
5
MIC5219-5.0BMM
2.2µF
tantalum
VOUT5V
VIN 6V
ENABLE
SHUTDOWN
470pF
5V Ultra-Low-Noise Regulator
15
2
34
2.2µF
tantalum
470pF
VOUT3.3V
MIC5219-3.3BM5
VIN 4V
ENABLE
SHUTDOWN
3.3V Ultra-Low-Noise Regulator
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
MM8 is a registered trademark of Micrel, Inc.
MicroLeadFrame and MLF are registered trademarks of Amkor Technology, Inc..
ENABLE
SHUTDOWN
MIC5219-x.xYML
1
EN 6CBYP
(optional)
VIN VOUT
COUT
5
4
2
3
Ultra-Low-Noise Regulator (Fixed)
ENABLE
SHUTDOWN
MIC5219YMT
1
EN 6
470pF
VIN VOUT
2.2µF
5
4
2
3
R1
R2
+
Ultra-Low-Noise Regulator (Adjustable)
Micrel, Inc. MIC5219
June 2009 2 M0371-061809
Ordering Information
Part Number Marking
Standard Pb-Free Standard Pb-Free* Volts Temp. Range Package
MIC5219-2.5BMM MIC5219-2.5YMM — — 2.5V –40°C to +125°C MSOP-8
MIC5219-2.85BMM MIC5219-2.85YMM — — 2.85V –40°C to +125°C MSOP-8
MIC5219-3.0BMM MIC5219-3.0YMM — — 3.0V –40°C to +125°C MSOP-8
MIC5219-3.3BMM MIC5219-3.3YMM — — 3.3V –40°C to +125°C MSOP-8
MIC5219-3.6BMM MIC5219-3.6YMM — — 3.6V –40°C to +125°C MSOP-8
MIC5219-5.0BMM MIC5219-5.0YMM — — 5.0V –40°C to +125°C MSOP-8
MIC5219BMM MIC5219YMM — — Adj. –40°C to +125°C MSOP-8
MIC5219-2.5BM5 MIC5219-2.5YM5 LG25 LG25 2.5V –40°C to +125°C SOT-23-5
MIC5219-2.6BM5 MIC5219-2.6YM5 LG26 LG26 2.6V –40°C to +125°C SOT-23-5
MIC5219-2.7BM5 MIC5219-2.7YM5 LG27 LG27 2.7V –40°C to +125°C SOT-23-5
MIC5219-2.8BM5 MIC5219-2.8YM5 LG28 LG28 2.8V –40°C to +125°C SOT-23-5
MIC5219-2.8BML MIC5219-2.8YML G28 G28 2.8V –40°C to +125°C 6-Pin 2×2 MLF®
MIC5219-2.85BM5 MIC5219-2.85YM5 LG2J LG2J 2.85V –40°C to +125°C SOT-23-5
MIC5219-2.9BM5 MIC5219-2.9YM5 LG29 LG29 2.9V –40°C to +125°C SOT-23-5
MIC5219-3.1BM5 MIC5219-3.1YM5 LG31 LG31 3.1V –40°C to +125°C SOT-23-5
MIC5219-3.0BM5 MIC5219-3.0YM5 LG30 LG30 3.0V –40°C to +125°C SOT-23-5
MIC5219-3.0BML MIC5219-3.0YML G30 G30 3.0V –40°C to +125°C 6-Pin 2×2 MLF®
MIC5219-3.3BM5 MIC5219-3.3YM5 LG33 LG33 3.3V –40°C to +125°C SOT-23-5
MIC5219-3.3BML MIC5219-3.3YML G33 G33 3.3V –40°C to +125°C 6-Pin 2×2 MLF®
MIC5219-3.6BM5 MIC5219-3.6YM5 LG36 LG36 3.6V –40°C to +125°C SOT-23-5
MIC5219-5.0BM5 MIC5219-5.0YM5 LG50 LG50 5.0V –40°C to +125°C SOT-23-5
MIC5219BM5 MIC5219YM5 LGAA LGAA Adj. –40°C to +125°C SOT-23-5
MIC5219YMT GAA Adj. –40°C to +125°C 6-Pin 2x2 Thin MLF®**
MIC5219-5.0YMT G50 5.0V –40°C to +125°C 6-Pin 2x2 Thin MLF®**
Other voltages available. Consult Micrel for details.
* Over/underbar may not be to scale. ** Pin 1 identier = ▲.
1
2
3
4
8
7
6
5
GND
GND
GND
GND
EN
IN
OUT
BYP
MIC5219-x.xBMM / MM8® / MSOP-8
Fixed Voltages
(Top View)
1
2
3
4
8
7
6
5
GND
GND
GND
GND
EN
IN
OUT
BYP
MIC5219YMM / MIC5219BMM
MM8® MSOP-8
Adjustable Voltage
(Top View)
IN
OUTBYP
EN
LGxx
13
4 5
2
GND
MIC5219-x.xBM5 / SOT-23-5
Fixed Voltages
(Top View)
Part
Identification
IN
OUTADJ
EN
LGAA
13
45
2
GND
MIC5219BM5 / SOT-23-5
Adjustable Voltage
(Top View)
Pin Conguration
1EN
GND
IN
6BYP
NC
OUT
5
4
2
3
MIC5219-x.xBML
6-Pin 2mm × 2mm MLF® (ML)
(Top View)
MIC5219YMT
6-Pin 2mm × 2mm Thin MLF® (MT)
(Top View)
June 2009 3 M0371-061809
Micrel, Inc. MIC5219
Pin Description
Pin No. Pin No. Pin No. Pin Name Pin Function
MLF-6 MSOP-8 SOT-23-5
TMLF-6
3 2 1 IN Supply Input.
2 5–8 2 GND Ground: MSOP-8 pins 5 through 8 are internally connected.
4 3 5 OUT Regulator Output.
1 1 3 EN Enable (Input): CMOS compatible control input. Logic high = enable; logic
low or open = shutdown.
6 4 (xed) 4 (xed) BYP Reference Bypass: Connect external 470pF capacitor to GND to reduce
output noise. May be left open.
5(NC) 4 (adj.) 4 (adj.) ADJ Adjust (Input): Feedback input. Connect to resistive voltage-divider network.
EP — — GND Ground: Internally connected to the exposed pad. Connect externally to
GND pin.
Micrel, Inc. MIC5219
June 2009 4 M0371-061809
Electrical Characteristics(3)
VIN = VOUT + 1.0V; COUT = 4.7µF, IOUT = 100µA; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C; 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 Coefcient
ΔVOUT/VOUT Line Regulation VIN = VOUT + 1V to 12V 0.009 0.05 %/V
0.1
ΔVOUT/VOUT Load Regulation IOUT = 100µA to 500mA, Note 5 0.05 0.5 %
0.7
VIN – VOUT Dropout Voltage(6) I
OUT = 100µA 10 60 mV
80
I
OUT = 50mA 115 175 mV
250
I
OUT = 150mA 175 300 mV
400
I
OUT = 500mA 350 500 mV
600
IGND Ground Pin Current(7, 8) V
EN ≥ 3.0V, IOUT = 100µA 80 130 µA
170
V
EN ≥ 3.0V, IOUT = 50mA 350 650 µA
900
V
EN ≥ 3.0V, IOUT = 150mA 1.8 2.5 mA
3.0
V
EN ≥ 3.0V, IOUT = 500mA 12 20 mA
25
Ground Pin Quiescent Current(8) V
EN ≤ 0.4V 0.05 3 µA
V
EN ≤ 0.18V 0.10 8 µA
PSRR Ripple Rejection f = 120Hz 75 dB
ILIMIT Current Limit VOUT = 0V 700 1000 mA
ΔVOUT/ΔPD Thermal Regulation Note 9 0.05 %/W
eno Output Noise(10) I
OUT = 50mA, COUT = 2.2µF, CBYP = 0 500
nV/ Hz
I
OUT = 50mA, COUT = 2.2µF, CBYP = 470pF 300
nV/ Hz
ENABLE Input
VENL Enable Input Logic-Low Voltage VEN = logic low (regulator shutdown) 0.4 V
0.18
V
EN = logic high (regulator enabled) 2.0 V
IENL Enable Input Current VENL ≤ 0.4V 0.01 –1 µA
V
ENL ≤ 0.18V 0.01 –2 µA
IENH V
ENH ≥ 2.0V 2 5 20 µA
25
Absolute Maximum Ratings(1)
Supply Input Voltage (VIN) ..............................–20V to +20V
Power Dissipation (PD) ............................. Internally Limited
Junction Temperature (TJ) ........................ –40°C to +125°C
Storage Temperature (TS) ........................ –65°C to +150°C
Lead Temperature (Soldering, 5 sec.) ....................... 260°C
Operating Ratings(2)
Supply Input Voltage (VIN) ............................ +2.5V to +12V
Enable Input Voltage (VEN)....................................0V to VIN
Junction Temperature (TJ) ........................ –40°C to +125°C
Package Thermal Resistance ........................... see Table 1
June 2009 5 M0371-061809
Micrel, Inc. MIC5219
Notes:
1. Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specications do not apply when operating
the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(max),
the junction-to-ambient thermal resistance, θJA, and the ambient temperature, TA. The maximum allowable power dissipation at any 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.
2. The device is not guaranteed to function outside its operating rating.
3. Specication for packaged product only.
4. Output voltage temperature coefcient is dened as 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 specication.
6. Dropout voltage is dened 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.
9. Thermal regulation is dened as the change in output voltage at a time “t” after a change in power dissipation is applied, excluding load or line regu-
lation effects. Specications are for a 500mA load pulse at VIN = 12V for t = 10ms.
10. CBYP is an optional, external bypass capacitor connected to devices with a BYP (bypass) or ADJ (adjust) pin.
Micrel, Inc. MIC5219
June 2009 6 M0371-061809
Typical Characteristics
-100
-80
-60
-40
-20
0
1E+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7
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+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7
FREQUENCY (Hz)
Power Supply
Rejection Ratio
IOUT = 1mA
COUT = 1µF
VIN = 6V
VOUT = 5V
10 100 1k 10k 100k 1M 10M
-100
-80
-60
-40
-20
0
1E+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7
FREQUENCY (Hz)
Power Supply
Rejection Ratio
IOUT = 100mA
COUT = 1µF
VIN = 6V
VOUT = 5V
10 100 1k 10k 100k 1M 10M
-100
-80
-60
-40
-20
0
1E+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7
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+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7
FREQUENCY (Hz)
Power Supply
Rejection Ratio
IOUT = 1mA
COUT = 2.2µF
CBYP = 0.01µF
VIN = 6V
VOUT = 5V
10 100 1k 10k 100k 1M 10M
0
10
20
30
40
50
60
0 0.1 0.2 0.3 0.4
VOLTAGE DROP (V)
Power Supply Ripple Rejection
vs. Voltage Drop
IOUT = 100mA
10mA
1mA
COUT = 1µF
0
10
20
30
40
50
60
70
80
90
100
0 0.1 0.2 0.3 0.4
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+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7
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+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7
FREQUENCY (Hz)
Noise Performance
10mA
1mA
100mA
10 100 1k 10k 100k 1M 10M
VOUT = 5V
COUT = 10µF
electrolytic
0.0001
0.001
0.01
0.1
1
10
1E+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7
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
OUTPUT CURRENT (mA)
Dropout Voltage
vs. Output Current
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0123456789
INPUT VOLTAGE (V)
Dropout Characteristics
IL =100µA
IL=100mA
IL=500mA
June 2009 7 M0371-061809
Micrel, Inc. MIC5219
0
2
4
6
8
10
12
0 100 200 300 400 500
OUTPUT CURRENT (mA)
Ground Current
vs. Output Current
0
0.5
1.0
1.5
2.0
2.5
3.0
02468
INPUT VOLTAGE (V)
Ground Current
vs. Supply Voltage
IL=100 mA
IL=100µA
0
5
10
15
20
25
0123456789
INPUT VOLTAGE (V)
Ground Current
vs. Supply Voltage
IL=500mA
Micrel, Inc. MIC5219
June 2009 8 M0371-061809
Block Diagrams
IN
EN
OUT
BYP
C
BYP
(optional)
GND
V
REF
Bandgap
Ref.
Current Limit
Thermal Shutdown
C
OUT
V
OUT
V
IN
MIC5219-x.xBM5/M/YMT
Ultra-Low-Noise Fixed Regulator
IN
EN
OUT
C
BYP
(optional)
GND
V
REF
Bandgap
Ref.
Current Limit
Thermal Shutdown
C
OUT
V
OUT
V
IN
R1
R2
MIC5219BM5/MM/YMT
Ultra-Low-Noise Adjustable Regulator
June 2009 9 M0371-061809
Micrel, Inc. MIC5219
Applications Information
The MIC5219 is designed for 150mA to 200mA output current
applications where a high current spike (500mA) is needed for
short, start-up conditions. Basic application of the device will
be discussed initially followed by a more detailed discussion
of higher current applications.
Enable/Shutdown
Forcing EN (enable/shutdown) high (>2V) enables the
regulator. EN is compatible with CMOS logic. If the enable/
shutdown feature is not required, connect EN to IN (supply
input). See Figure 5.
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
lter 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 5). 2.2µF minimum is recommended when CBYP
is 470pF (see Figure 6). For applications < 3V, the output
capacitor should be increased to 22µF minimum to reduce
start-up overshoot. Larger values improve the regulator’s
transient response. The output capacitor value may be in-
creased without limit.
The output capacitor should have an ESR (equivalent series
resistance) of about 1Ω or less and a resonant frequency
above 1MHz. Ultra-low-ESR capacitors could cause oscilla-
tion and/or underdamped transient response. Most tantalum
or aluminum electrolytic capacitors are adequate; lm types
will work, but are more expensive. Many aluminum electro-
lytics have electrolytes that freeze at about –30°C, so solid
tantalums are recommended for operation below –25°C.
At lower values of output current, less output capacitance is
needed for stability. The capacitor can be reduced to 0.47µF
for current below 10mA, or 0.33µF for currents below 1mA.
No-Load Stability
The MIC5219 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 is connected to the internal voltage reference. A 470pF
capacitor (CBYP) connected from BYP to GND quiets this
reference, providing a signicant reduction in output noise
(ultra-low-noise performance). CBYP reduces the regulator
phase margin; when using CBYP
, output capacitors of 2.2µF
or greater are generally required to maintain stability.
The start-up speed of the MIC5219 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
.
Thermal Considerations
The MIC5219 is designed to provide 200mA of continuous
current in two very small prole packages. 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 thermal resistance,
junction-to-ambient, of the device and the following basic
equation.
PD(max ) = TJ(max ) − TA
( )
θJA
TJ(max) is the maximum junction temperature of the die,
125°C, and TA is the ambient operating temperature. θJA
is layout dependent; Table 1 shows examples of thermal
resistance, junction-to-ambient, for the MIC5219.
Package θJA Recommended θJA 1" Squareθ
JC
Minimum Footprint 2oz. Copper
MM8® (MM) 160°C/W 70°C/W 30°C/W
SOT-23-5 (M5) 220°C/W 170°C/W 130°C/W
2×2 MLF® (ML) 90°C/W — —
2×2 Thin
MLF® (MT) 90°C/W — —
Table 1. MIC5219 Thermal Resistance
The actual power dissipation of the regulator circuit can be
determined using one simple equation.
P
D = (VIN – VOUT) IOUT + VIN IGND
Substituting PD(max) for PD and solving for the operating
conditions that are critical to the application will give the
maximum operating conditions for the regulator circuit. For
example, if we are operating the MIC5219-3.3BM5 at room
temperature, with a minimum footprint layout, we can deter-
mine the maximum input voltage for a set output current.
PD(max ) = 125 °C−25°C
( )
220°C/W
P
D(max) = 455mW
The thermal resistance, junction-to-ambient, for the minimum
footprint is 220°C/W, taken from Table 1. The maximum power
dissipation number cannot be exceeded for proper opera-
tion of the device. Using the output voltage of 3.3V, and an
output current of 150mA, we can determine the maximum
input voltage. Ground current, maximum of 3mA for 150mA
of output current, can be taken from the “Electrical Charac-
teristics” section of the data sheet.
455mW = (VIN – 3.3V) × 150mA + VIN × 3mA
455mW = (150mA) × VIN + 3mA × VIN – 495mW
950mW = 153mA × VIN
V
IN = 6.2VMAX
Therefore, a 3.3V application at 150mA of output current
can accept a maximum input voltage of 6.2V in a SOT-23-5
package. For a full discussion of heat sinking and thermal
effects on voltage regulators, refer to the “Regulator Ther-
mals” section of Micrel’s Designing with Low-Dropout Voltage
Regulators handbook.
Micrel, Inc. MIC5219
June 2009 10 M0371-061809
Peak Current Applications
The MIC5219 is designed for applications where high start-up
currents are demanded from space constrained regulators.
This device will deliver 500mA start-up current from a SOT-
23-5 or MM8 package, allowing high power from a very low
prole device. The MIC5219 can subsequently provide output
current that is only limited by the thermal characteristics of
the device. You can obtain higher continuous currents from
the device with the proper design. This is easily proved with
some thermal calculations.
If we look at a specic example, it may be easier to follow.
The MIC5219 can be used to provide up to 500mA continuous
output current. First, calculate the maximum power dissipa-
tion of the device, as was done in the thermal considerations
section. Worst case thermal resistance (θJA = 220°C/W for
the MIC5219-x.xBM5), will be used for this example.
PD(max ) = TJ(max ) − TA
( )
θJA
Assuming a 25°C room temperature, we have a maximum
power dissipation number of
PD(max ) = 125 °C−25°C
( )
220 °C/W
P
D(max) = 455mW
Then we can determine the maximum input voltage for a
5-volt regulator operating at 500mA, using worst case ground
current.
P
D(max) = 455mW = (VIN – VOUT) IOUT + VIN IGND
I
OUT = 500mA
V
OUT = 5V
I
GND = 20mA
455mW = (VIN – 5V) 500mA + VIN × 20mA
2.995W = 520mA × VIN
VIN(max ) = 2.955W
520mA =5.683V
Therefore, to be able to obtain a constant 500mA output cur-
rent from the 5219-5.0BM5 at room temperature, you need
extremely tight input-output voltage differential, barely above
the maximum dropout voltage for that current rating.
You can run the part from larger supply voltages if the proper
precautions are taken. Varying the duty cycle using the en-
able pin can increase the power dissipation of the device by
maintaining a lower average power gure. This is ideal for
applications where high current is only needed in short bursts.
Figure 1 shows the safe operating regions for the MIC5219-x.
xBM5 at three different ambient temperatures and at differ-
ent output currents. The data used to determine this gure
assumed a minimum footprint PCB design for minimum heat
sinking. Figure 2 incorporates the same factors as the rst
gure, but assumes a much better heat sink. A 1" square cop-
per trace on the PC board reduces the thermal resistance of
the device. This improved thermal resistance improves power
dissipation and allows for a larger safe operating region.
Figures 3 and 4 show safe operating regions for the MIC5219-x.
xBMM, the power MSOP package part. These graphs show
three typical operating regions at different temperatures. The
lower the temperature, the larger the operating region. The
graphs were obtained in a similar way to the graphs for the
MIC5219-x.xBM5, taking all factors into consideration and
using two different board layouts, minimum footprint and 1"
square copper PC board heat sink. (For further discussion
of PC board heat sink characteristics, refer to “Application
Hint 17, Designing PC Board Heat Sinks” .)
The information used to determine the safe operating regions
can be obtained in a similar manner such as determining
typical power dissipation, already discussed. Determining
the maximum power dissipation based on the layout is the
rst step, this is done in the same manner as in the previous
two sections. Then, a larger power dissipation number multi-
plied by a set maximum duty cycle would give that maximum
power dissipation number for the layout. This is best shown
through an example. If the application calls for 5V at 500mA
for short pulses, but the only supply voltage available is
8V, then the duty cycle has to be adjusted to determine an
average power that does not exceed the maximum power
dissipation for the layout.
Avg.P D=% DC
100


 

 VIN – V OUT
( )
I OUT +VIN I GND
455mW = % DC
100


 

 8V – 5V
( )
500mA +8V ×20mA
455mW = % Duty Cycle
100


 

 1.66W
0.274 = % Duty Cycle
100
% Duty Cycle Max = 27.4%
With an output current of 500mA and a three-volt drop across
the MIC5219-xxBMM, the maximum duty cycle is 27.4%.
Applications also call for a set nominal current output with a
greater amount of current needed for short durations. This is a
tricky situation, but it is easily remedied. Calculate the average
power dissipation for each current section, then add the two
numbers giving the total power dissipation for the regulator.
For example, if the regulator is operating normally at 50mA,
but for 12.5% of the time it operates at 500mA output, the
total power dissipation of the part can be easily determined.
First, calculate the power dissipation of the device at 50mA.
We will use the MIC5219-3.3BM5 with 5V input voltage as
our example.
P
D × 50mA = (5V – 3.3V) × 50mA + 5V × 650µA
P
D × 50mA = 173mW
However, this is continuous power dissipation, the actual
on-time for the device at 50mA is (100%-12.5%) or 87.5%
of the time, or 87.5% duty cycle. Therefore, PD must be mul-
tiplied by the duty cycle to obtain the actual average power
dissipation at 50mA.
June 2009 11 M0371-061809
Micrel, Inc. MIC5219
0
2
4
6
8
10
0 20 40 60 80 100
DUTY CYCLE (%)
500mA
400mA
300mA
200mA
100mA
0
2
4
6
8
10
0 20 40 60 80 100
DUTY CYCLE (%)
500mA
400mA
300mA
200mA
100mA
0
2
4
6
8
10
0 20 40 60 80 100
DUTY CYCLE (%)
500mA
400mA
300mA
200mA
100mA
0
2
4
6
8
10
0 20 40 60 80 100
DUTY CYCLE (%)
500mA
400mA
300mA
200mA
0
2
4
6
8
10
0 20 40 60 80 100
DUTY CYCLE (%)
500mA
400mA
300mA
200mA
100mA
0
2
4
6
8
10
0 20 40 60 80 100
DUTY CYCLE (%)
500mA
400mA
300mA
200mA
100mA
0
2
4
6
8
10
0 20 40 60 80 100
DUTY CYCLE (%)
500mA
400mA
300mA
200mA
100mA
0
2
4
6
8
10
0 20 40 60 80 100
DUTY CYCLE (%)
500mA
400mA
300mA
200mA
0
2
4
6
8
10
0 20 40 60 80 100
DUTY CYCLE (%)
500mA
400mA
300mA
200mA
100mA
0
2
4
6
8
10
0 20 40 60 80 100
DUTY CYCLE (%)
500mA
400mA 300mA
200mA
100mA
0
2
4
6
8
10
0 20 40 60 80 100
DUTY CYCLE (%)
500mA
400mA
300mA
200mA
100mA
0
2
4
6
8
10
0 20 40 60 80 100
DUTY CYCLE (%)
500mA
400mA
300mA
200mA
100mA
a. 25°C Ambient b. 50°C Ambient c. 85°C Ambient
Figure 4. MIC5219-x.xBMM (MSOP-8) on 1-inch2 Copper Cladding
a. 25°C Ambient b. 50°C Ambient c. 85°C Ambient
Figure 3. MIC5219-x.xBMM (MSOP-8) on Minimum Recommended Footprint
a. 25°C Ambient b. 50°C Ambient c. 85°C Ambient
Figure 2. MIC5219-x.xBM5 (SOT-23-5) on 1-inch2 Copper Cladding
a. 25°C Ambient b. 50°C Ambient c. 85°C Ambient
Figure 1. MIC5219-x.xBM5 (SOT-23-5) on Minimum Recommended Footprint
Micrel, Inc. MIC5219
June 2009 12 M0371-061809
P
D × 50mA = 0.875 × 173mW
P
D × 50mA = 151mW
The power dissipation at 500mA must also be calculated.
P
D × 500mA = (5V – 3.3V) 500mA + 5V × 20mA
P
D × 500mA = 950mW
This number must be multiplied by the duty cycle at which it
would be operating, 12.5%.
P
D × = 0.125 × 950mW
P
D × = 119mW
The total power dissipation of the device under these condi-
tions is the sum of the two power dissipation gures.
P
D(total) = PD × 50mA + PD × 500mA
P
D(total) = 151mW + 119mW
P
D(total) = 270mW
The total power dissipation of the regulator is less than the
maximum power dissipation of the SOT-23-5 package at room
temperature, on a minimum footprint board and therefore
would operate properly.
Multilayer boards with a ground plane, wide traces near the
pads, and large supply-bus lines will have better thermal
conductivity.
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.
Fixed Regulator Circuits
MIC5219-x.x
IN OUT
GND 1µF
V
IN
V
OUT
EN BYP
Figure 5. Low-Noise Fixed Voltage Regulator
Figure 5 shows a basic MIC5219-x.xBMX xed-voltage regu-
lator circuit. A 1µF minimum output capacitor is required for
basic xed-voltage applications.
MIC5219-x.x
IN OUT
GND
470pF
V
IN
EN BYP
2.2µF
V
OUT
Figure 6. Ultra-Low-Noise Fixed Voltage Regulator
Figure 6 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
MIC5219
IN OUT
GND
V
IN
EN ADJ
1µF
V
OUT
R1
R2
Figure 7. Low-Noise Adjustable Voltage Regulator
Figure 7 shows the basic circuit for the MIC5219 adjustable
regulator. The output voltage is congured by selecting values
for R1 and R2 using the following formula:
VOUT =1.242V R2
R1 +1


 


Although ADJ is a high-impedance input, for best performance,
R2 should not exceed 470kΩ.
MIC5219
IN OUT
GND
V
IN
EN ADJ
2.2µF
V
OUT
R1
R2
470pF
Figure 8. Ultra-Low-Noise Adjustable Application
Figure 8 includes the optional 470pF bypass capacitor from
ADJ to GND to reduce output noise.
June 2009 13 M0371-061809
Micrel, Inc. MIC5219
Package Information
8-Pin MSOP (MM)
SOT-23-5 (M5)
Micrel, Inc. MIC5219
June 2009 14 M0371-061809
6-Pin MLF® (ML)
6-Pin Thin MLF® (MT)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
t e l + 1 (408) 944-0800 f a x + 1 (408) 474-1000 w e b http://www.micrel.com
The 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 specications at any time without notication 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 signicant injury to the user. A Purchaser’s
use or sale of Micrel Products for use in life support appliances, devices or systems is at Purchaser’s own risk and Purchaser agrees to fully indemnify
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