MICREL MIC3775

MIC3775
Micrel
MIC3775
750mA µCap Low-Voltage Low-Dropout Regulator
Final
General Description
Features
The MIC3775 is a 750mA low-dropout linear voltage regulators that provides low-voltage, high-current output from an
extremely small package. Utilizing Micrel’s proprietary
Superβeta PNP™ pass element, the MIC3775 offers extremely low-dropout (typically 280mV at 750mA) and low
ground current (typically 7.5mA at 750mA).
The MIC3775 is ideal for PC add-in cards that need to convert
from standard 5V to 3.3V or 3.0V, 3.3V to 2.5V or 2.5V to 1.8V
or 1.65V. A guaranteed maximum dropout voltage of 500mV
over all operating conditions allows the MIC3775 to provide
2.5V from a supply as low as 3.0V and 1.8V or 1.5V from a
supply as low as 2.25V.
The MIC3775 is fully protected with overcurrent limiting,
thermal shutdown, and reversed-leakage protection. Fixed
and adjustable output voltage options are available with an
operating temperature range of –40°C to +125°C.
• Fixed and adjustable output voltages to 1.24V
• 280mV typical dropout at 750mA
Ideal for 3.0V to 2.5V conversion
Ideal for 2.5V to 1.8V or 1.65V conversion
• Stable with ceramic capacitor
• 750mA minimum guaranteed output current
• 1% initial accuracy
• Low ground current
• Current limiting and thermal shutdown
• Reversed-leakage protection
• Fast transient response
• Low-profile power MSOP-8 package
Applications
•
•
•
•
•
•
•
•
For other voltages, contact Micrel.
Fiber optic modules
LDO linear regulator for PC add-in cards
PowerPC™ power supplies
High-efficiency linear power supplies
SMPS post regulator
Multimedia and PC processor supplies
Battery chargers
Low-voltage microcontrollers and digital logic
Ordering Information
Part Number
Voltage
Junction Temp. Range
Package
MIC3775-1.5BMM
1.5V
–40°C to +125°C
MSOP-8
MIC3775-1.65BMM
1.65V
–40°C to +125°C
MSOP-8
MIC3775-1.8BMM
1.8V
–40°C to +125°C
MSOP-8
MIC3775-2.5BMM
2.5V
–40°C to +125°C
MSOP-8
MIC3775-3.0BMM
3.0V
–40°C to +125°C
MSOP-8
MIC3775-3.3BMM
3.3V
–40°C to +125°C
MSOP-8
MIC3775BMM
Adj.
–40°C to +125°C
MSOP-8
Typical Applications
Dropout
vs. Output Current
300
ENABLE
SHUTDOWN
250
MIC3775BMM
IN
OUT
DROPOUT (mV)
VIN
2.5V
1.25V
R1
EN
ADJ
GND
R2
10µF
ceramic
1.8VOUT
200
150
100
3.3VOUT
2.5VOUT
50
1.25V/750mA Adjustable Regulator
0
0
0.25
0.5
0.75
OUTPUT CURRENT (A)
Superβeta PNP is a trademark of Micrel, Inc.
PowerPC is a trademark of Motorola
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
March 2003
1
MIC3775
MIC3775
Micrel
Pin Configuration
EN 1
8 GND
EN 1
8 GND
IN 2
7 GND
IN 2
7 GND
FLG 3
6 GND
ADJ 3
6 GND
OUT 4
5 GND
OUT 4
5 GND
MIC3775-x.x
Fixed
MSOP-8 (MM)
MIC3775
Adjustable
MSOP-8 (MM)
Pin Description
Pin No.
Fixed
Pin No.
Adjustable
Pin Name
1
1
EN
Enable (Input): CMOS-compatible control input. Logic high = enable, logic
low or open = shutdown.
2
2
IN
Supply (Input).
3
Pin Function
FLG
Flag (Output): Open-collector error flag output. Active low = output undervoltage.
3
ADJ
Adjustment Input: Feedback input. Connect to resistive voltage-divider
network.
4
4
OUT
Regulator Output.
5–8
5–8
GND
Ground.
MIC3775
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March 2003
MIC3775
Micrel
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Supply Voltage (VIN) .................................................... 6.5V
Enable Voltage (VEN) ................................................. +6.5V
Storage Temperature (TS) ....................... –65°C to +150°C
Lead Temperature (soldering, 5 sec.) ....................... 260°C
ESD ......................................................................... Note 3
Supply Voltage (VIN) .................................... +2.25V to +6V
Enable Voltage (VEN) ......................................... 0V to +6V
Maximum Power Dissipation (PD(max))..................... Note 4
Junction Temperature (TJ) ....................... –40°C to +125°C
Package Thermal Resistance
MSOP-8 (θJA) ...................................................... 80°C/W
Electrical Characteristics (Note 5)
VIN = VOUT + 1V; VEN = 2.25V; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C; unless noted
Symbol
Parameter
Condition
VOUT
Output Voltage
10mA
10mA ≤ IOUT ≤ 750mA, VOUT + 1V ≤ VIN ≤ 6V
Line Regulation
IOUT = 10mA, VOUT + 1V ≤ VIN ≤ 6V
Load Regulation
VIN = VOUT + 1V, 10mA ≤ IOUT ≤ 750mA,
∆VOUT/∆T
Output Voltage Temp. Coefficient,
Note 6
VDO
Dropout Voltage, Note 7
IGND
Typ
Max
Units
1
2
%
%
0.06
0.5
%
0.2
1
%
–1
–2
40
ppm/°C
IOUT = 100mA, ∆VOUT = –1%
125
IOUT = 500mA, ∆VOUT = –1%
210
IOUT = 750mA, ∆VOUT = –1%
280
IOUT = 100mA, VIN = VOUT + 1V
700
µA
IOUT = 500mA, VIN = VOUT + 1V
3.7
mA
IOUT = 750mA, VIN = VOUT + 1V
7.5
15
mA
Current Limit
VOUT = 0V, VIN = VOUT + 1V
1.6
2.5
A
Enable Input Voltage
logic low (off)
0.8
V
Ground Current, Note 8
IOUT(lim)
Min
200
250
mV
mV
mV
500
mV
Enable Input
VEN
logic high (on)
IEN
Enable Input Current
VEN = 2.25V
2.25
1
V
10
VEN = 0.8V
30
µA
2
4
µA
µA
Flag Output
IFLG(leak)
Output Leakage Current
VOH = 6V
0.01
1
2
µA
µA
VFLG(do)
Output Low Voltage
VIN = 2.250V, IOL, = 250µA
250
500
mV
VFLG
Low Threshold
% of VOUT
High Threshold
% of VOUT
93
%
99.2
Hysteresis
%
1
%
Adjustable Output Only
Reference Voltage
1.227
1.215
Adjust Pin Bias Current
Note 1.
Exceeding the absolute maximum ratings may damage the device.
Note 2.
The device is not guaranteed to function outside its operating rating.
Note 3.
Devices are ESD sensitive. Handling precautions recommended.
Note 4.
PD(max) = (TJ(max) – TA) ÷ θJA, where θJA depends upon the printed circuit layout. See “Applications Information.”
March 2003
3
1.240
1.252
1.265
V
V
40
80
120
nA
nA
MIC3775
MIC3775
Note 5.
Micrel
Specification for packaged product only.
Note 6.
Output voltage temperature coefficient is ∆VOUT(worst case) ÷ (TJ(max) – TJ(min)) where TJ(max) is +125°C and TJ(min) is –40°C.
Note 7.
VDO = VIN – VOUT when VOUT decreases to 98% of its nominal output voltage with VIN = VOUT + 1V. For output voltages below 1.75V, dropout
voltage is the input-to-output voltage differential with the minimum input voltage being 2.25V. Minimum input operating voltage is 2.25V.
Note 8.
IGND is the quiescent current. IIN = IGND + IOUT.
MIC3775
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March 2003
MIC3775
Micrel
Typical Characteristics
Power Supply
Rejection Ratio
Power Supply
Rejection Ratio
80
80
VIN = 5V
VOUT = 3.3V
40
30 I
OUT=750mA
20 COUT =10µF
10 CIN =0
40
30 I
OUT=750mA
20 COUT =47µF
10 CIN =0
0
0.01
1000
Power Supply
Rejection Ratio
DROPOUT (mV)
PSRR (dB)
50
40
30 I
OUT=750mA
20 COUT =47µF
10 CIN =0
3.3VOUT
100
2.5VOUT
50
1.8
1.6
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
1.4
1.2
1.0
10mA Load
0.6
750mA Load
0.2
0
1.5
1.7
1.9
2.1
2.3
INPUT VOLTAGE (V)
2.5
1.0
0.8
10mA Load
0.6
0.4
0.2
0
1.5
GROUND CURRENT (mA)
OUTPUT VOLTAGE (V)
Dropout Characteristics
(2.5V)
2
2.5
INPUT VOLTAGE (V)
2.5
2.0
3.0
2.5
750mA Load
10mA Load
1.0
0.5
4.5
10mA Load
1.0
0.5
2
2.5
3
INPUT VOLTAGE (V)
3.5
Ground Current
vs. Supply Voltage (1.5V)
0.8
6
2.5VOUT
5
4
3
2
1
0
750mA Load
1.5
0
1.5
3
7
March 2003
100
Ground Current
vs. Output Current
3.5
2
2.5
3
3.5
4
INPUT VOLTAGE (V)
150
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
0.25
0.5
0.75
OUTPUT CURRENT (A)
750mA Load
1.4
1.2
4.0
1.5
200
3.0
Dropout Characteristics
(3.3V)
2.0
2.5VOUT
250
Dropout Characteristics
(1.8V)
Dropout Characteristics
(1.5V)
0.4
300
50
0
0
2.0
1000
350
1.8VOUT
150
1000
0.1
1
10
100
FREQUENCY (KHz)
Dropout
vs. Temperature
200
1.6
0.8
30 I
OUT=750mA
20 COUT =10µF
10 CIN =0
400
250
60
0.1
1
10
100
FREQUENCY (KHz)
40
0
0.01
1000
300
VIN =3.3V
VOUT =2.5V
0
0.01
50
Dropout
vs. Output Current
80
70
0.1
1
10
100
FREQUENCY (KHz)
DROPOUT (mV)
0.1
1
10
100
FREQUENCY (KHz)
50
OUTPUT VOLTAGE (V)
0
0.01
60
PSRR (dB)
60
50
VIN =3.3V
VOUT =2.5V
70
3.3VOUT
0
0.25
0.5
0.75
OUTPUT CURRENT (A)
5
GROUND CURRENT (mA)
PSRR (dB)
60
80
VIN =5V
VOUT =3.3V
70
PSRR (dB)
70
0
1.5
Power Supply
Rejection Ratio
0.7
0.6
100mA
0.5
0.4
0.3
0.2
10mA
0.1
0
0
1
2
3
4
5
INPUT VOLTAGE (V)
6
MIC3775
MIC3775
Micrel
10
9
0.8
6
5
4
3
2
1
500mA
0
0
1
2
3
4
5
INPUT VOLTAGE (V)
0.6
0.4
0.3
0.2
0.1
0
0
6
16
GROUND CURRENT (mA)
1.0
100mA
0.6
0.4
10mA
1
2
3
4
5
INPUT VOLTAGE (V)
12
750mA
8
6
500mA
2
8
6
4
6
7
6
2.5VOUT
4
3
2
IOUT=750mA
OUTPUT VOLTAGE (V)
GROUND CURRENT (mA)
8
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
MIC3775
1
2
3
4
5
INPUT VOLTAGE (V)
2
500mA
1
2
3
4
5
INPUT VOLTAGE (V)
6
1.2
1.0
0.3
2.5VOUT
0.25
0.2
0.15
0.1
0.05
IOUT=10mA
100mA
0.8
0.6
0.4
10mA
0.2
0
0
6
1
2
3
4
5
INPUT VOLTAGE (V)
6
Ground Current
vs. Temperature
5
4.5
4
3.5
3
2.5
2.5VOUT
2
1.5
1
0.5
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
IOUT=500mA
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
Output Voltage
vs. Temperature
Short Circuit Current
vs. Supply Voltage
2.60
9
1
500mA
0.35
Ground Current
vs. Temperature
5
750mA
GROUND CURRENT (mA)
GROUND CURRENT (mA)
GROUND CURRENT (mA)
14
1
2
3
4
5
INPUT VOLTAGE (V)
4
0
0
0.4
0
6
1.4
10
2
750mA
8
Ground Current
vs. Temperature
16
4
10
Ground Current
vs. Supply Voltage (3.3V)
12
0
0
6
18
10
12
6
14
Ground Current
vs. Supply Voltage (3.3V)
0
1
2
3
4
5
INPUT VOLTAGE (V)
2.55
2.50
2.5VOUT
2.45
2.40
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
6
SHORT CIRCUIT CURRENT (A)
GROUND CURRENT (mA)
18
1.2
0
0
10mA
14
Ground Current
vs. Supply Voltage (2.5V)
1.4
0.2
100mA
0.5
Ground Current
vs. Supply Voltage (2.5V)
0.8
GROUND CURRENT (mA)
750mA
16
0.7
GROUND CURRENT (mA)
8
7
Ground Current
vs. Supply Voltage (1.8V)
Ground Current
vs. Supply Voltage (1.8V)
GROUND CURRENT (mA)
GROUND CURRENT (mA)
Ground Current
vs. Supply Voltage (1.5V)
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
2.25
3
3.75 4.5 5.25
SUPPLY VOLTAGE (V)
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March 2003
MIC3775
Micrel
1.0
1.6
1.4
0.8
2.5VIN
0.8
0.6
0.4
0.2
2.5V
IN
0.2
0
0 0.5 1 1.5 2 2.5 3 3.5 4
FLAG CURRENT (mA)
300
250
200
150
100
50
Flag Current = 250µA
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
Enable Current
vs. Temperature
9
Flag High (OK)
5
4
3
2
Flag Low (FAULT)
1
0.1
1
10
100 1000 10000
RESISTANCE (kΩ)
March 2003
ENABLE CURRENT (µA)
6
FLAG VOLTAGE (V)
5V
IN
0.4
Error Flag Pull-Up Resistor
0.01
3.3V
IN
0.6
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
0
350
FLAG LOW VOLTAGE (mV)
2.0
1.8
1.2
1.0
Flag Low Voltage
vs. Temperature
Flag Voltage
vs. Flag Current
FLAG VOLTAGE (V)
SHORT CIRCUIT CURRENT (A)
Short Circuit Current
vs. Temperature
8
7
6
5
4
2.5VEN
3
2
1
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
7
MIC3775
MIC3775
Micrel
Functional Characteristics
Load Transient Response
Output Voltage
(200mV/div)
Output Voltage
(200mV/div)
Load Transient Response
VIN = 3.3V
VOUT = 2.5V
COUT = 10µF Ceramic
VIN = 3.3V
VOUT = 2.5V
COUT = 10µF Ceramic
Output Current
(500mA/div)
750mA
10mA
TIME (200µs/div)
TIME (200µs/div)
Line Transient Response
Enable Transient Response
Enable Voltage
(2V/div)
5V
3.3V
VIN = 3.3V
VOUT = 2.5V
COUT = 10µF Ceramic
VOUT = 2.5V
COUT = 10µF Ceramic
TIME (10µs/div)
TIME (200µs/div)
MIC3775
10mA
Output Voltage
(1V/div)
Output Voltage
(50mV/div)
Input Voltage
(2V/div)
Output Current
(500mA/div)
750mA
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March 2003
MIC3775
Micrel
Functional Diagrams
OUT
IN
1.180V
FLAG
Ref.
1.240V
EN
Thermal
Shutdown
GND
MIC3775 Fixed Regulator with Flag and Enable Block Diagram
OUT
IN
Ref.
1.240V
ADJ
EN
Thermal
Shutdown
GND
MIC3775 Adjustable Regulator Block Diagram
March 2003
9
MIC3775
MIC3775
Micrel
Input Capacitor
An input capacitor of 1µF or greater is recommended when
the device is more than 4 inches away from the bulk AC
supply capacitance or when the supply is a battery. Small,
surface mount, ceramic chip capacitors can be used for
bypassing. Larger values will help to improve ripple rejection
by bypassing the input to the regulator, further improving the
integrity of the output voltage.
Error Flag
The MIC3775 features an error flag (FLG), which monitors
the output voltage and signals an error condition when this
voltage drops 5% below its expected value. The error flag is
an open-collector output that pulls low under fault conditions
and may sink up to 10mA. Low output voltage signifies a
number of possible problems, including an overcurrent fault
(the device is in current limit) or low input voltage. The flag
output is inoperative during overtemperature conditions. A
pull-up resistor from FLG to either VIN or VOUT is required for
proper operation. For information regarding the minimum and
maximum values of pull-up resistance, refer to the graph in
the “Typical Characteristics” section of the data sheet.
Enable Input
The MIC3775 features an active-high enable input (EN) that
allows on-off control of the regulator. Current drain reduces
to “zero” when the device is shutdown, with only microamperes of leakage current. The EN input has TTL/CMOS
compatible thresholds for simple logic interfacing. EN may be
directly tied to VIN and pulled up to the maximum supply
voltage
Transient Response and 3.3V to 2.5V or 2.5V to 1.8V or
1.65V Conversion
The MIC3775 has excellent transient response to variations
in input voltage and load current. The device has been
designed to respond quickly to load current variations and
input voltage variations. Large output capacitors are not
required to obtain this performance. A standard 10µF output
capacitor, is all that is required. Larger values help to improve
performance even further.
By virtue of its low-dropout voltage, this device does not
saturate into dropout as readily as similar NPN-based designs. When converting from 3.3V to 2.5V or 2.5V to 1.8V or
1.65V, the NPN-based regulators are already operating in
dropout, with typical dropout requirements of 1.2V or greater.
To convert down to 2.5V or 1.8V without operating in dropout,
NPN-based regulators require an input voltage of 3.7V at the
very least. The MIC3775 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 MIC3775 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.
Applications Information
The MIC3775 is a high-performance low-dropout voltage
regulator suitable for moderate to high-current voltage regulator applications. Its 500mV dropout voltage at full load and
overtemperature makes it especially valuable in batterypowered systems and as high-efficiency noise filters in postregulator applications. Unlike older NPN-pass transistor designs, where the minimum dropout voltage is limited by the
base-to-emitter voltage drop and collector-to-emitter saturation voltage, dropout performance of the PNP output of these
devices is limited only by the low VCE saturation voltage.
A trade-off for the low-dropout voltage is a varying base drive
requirement. Micrel’s Superβeta PNP™ process reduces
this drive requirement to only 2% of the load current.
The MIC3775 regulator is fully protected from damage due to
fault conditions. Linear current limiting is provided. Output
current during overload conditions is constant. Thermal shutdown disables the device when the die temperature exceeds
the maximum safe operating temperature. The output structure of these regulators allows voltages in excess of the
desired output voltage to be applied without reverse current
flow.
VIN
MIC3775-x.xBMM
IN
CIN
VOUT
OUT
GND
COUT
Figure 1. Capacitor Requirements
Output Capacitor
The MIC3775 requires an output capacitor for stable operation. As a µCap LDO, the MIC3775 can operate with ceramic
output capacitors as long as the amount of capacitance is
10µF or greater. For values of output capacitance lower than
10µF, the recommended ESR range is 200mΩ to 2Ω. The
minimum value of output capacitance recommended for the
MIC3775 is 4.7µF.
For 10µF or greater the ESR range recommended is less than
1Ω. Ultra-low ESR ceramic capacitors are recommended for
output capacitance of 10µF or greater to help improve transient response and noise reduction at high frequency.
X7R/X5R dielectric-type ceramic capacitors are recommended because of their temperature performance. X7Rtype 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.
MIC3775
10
March 2003
MIC3775
Micrel
sink thermal resistance) and θSA (sink-to-ambient thermal
resistance).
Using the power MSOP-8 reduces the θJC dramatically and
allows the user to reduce θCA. The total thermal resistance,
θJA (junction-to-ambient thermal resistance) is the limiting
factor in calculating the maximum power dissipation capability of the device. Typically, the power MSOP-8 has a θJA of
80°C/W, this is significantly lower than the standard MSOP-8
which is typically 160°C/W. θCA 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 temperature from being exceeded, the appropriate ground plane
heatsink must be used.
Adjustable Regulator Design
VIN
MIC3775
OUT
IN
VOUT
R1
ENABLE
SHUTDOWN
EN
ADJ
GND
R2
COUT
 R1
VOUT = 1.240V 1 +

 R2 
Figure 2. Adjustable Regulator with Resistors
The MIC3775 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:

V
R1 = R2  OUT − 1
 1.240 
Where VO is the desired output voltage. Figure 2 shows
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 MSOP-8 Thermal Characteristics
One of the secrets of the MIC3775’s performance is its power
MSOP-8 package featuring half the thermal resistance of a
standard MSOP-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 singlepiece electrical and thermal conductor. This concept has
been used by MOSFET manufacturers for years, proving
very reliable and cost effective for the user.
Thermal resistance consists of two main elements, θJC
(junction-to-case thermal resistance) and θCA (case-to-ambient thermal resistance). See Figure 3. θJC is the resistance
from the die to the leads of the package. θCA is the resistance
from the leads to the ambient air and it includes θCS (case-to-
MSOP-8
θJA
θJC
printed circuit board
Figure 3. Thermal Resistance
Figure 4 shows copper area versus power dissipation with
each trace corresponding to a different temperature rise
above ambient.
From these curves, the minimum area of copper necessary
for the part to operate safely can be determined. The maximum allowable temperature rise must be calculated to determine operation along which curve.
100°C
900
800
COPPER AREA (mm2)
40°C
50°C
55°C
65°C
75°C
85°C
COPPER AREA (mm2)
700
600
500
400
300
200
100
0
0
700
TJ = 125°C
85°C
50°C 25°C
600
500
400
300
200
100
0
0
0.25 0.50 0.75 1.00 1.25 1.50
POWER DISSIPATION (W)
Figure 4. Copper Area vs. Power-MSOP
∆TJA)
Power Dissipation (∆
March 2003
ground plane
heat sink area
AMBIENT
900
800
θCA
0.25 0.50 0.75 1.00 1.25 1.50
POWER DISSIPATION (W)
Figure 5. Copper Area vs. Power-MSOP
Power Dissipation (TA)
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∆T = TJ(max) – TA(max)
TJ(max) = 125°C
TA(max) = maximum ambient operating temperature
For example, the maximum ambient temperature is 50°C, the
∆T is determined as follows:
∆T = 125°C – 50°C
∆T = 75°C
Using Figure 4, the minimum amount of required copper can
be determined based on the required power dissipation.
Power dissipation in a linear regulator is calculated as follows:
PD = (VIN – VOUT) IOUT + VIN × IGND
Quick Method
Determine the power dissipation requirements for the design
along with the maximum ambient temperature at which the
device will be operated. Refer to Figure 5, which shows safe
operating curves for three different ambient temperatures:
25°C, 50°C and 85°C. From these curves, the minimum
amount of copper can be determined by knowing the maximum power dissipation required. If the maximum ambient
temperature is 50°C and the power dissipation is as above,
625mW, the curve in Figure 5 shows that the required area of
copper is 160mm2.
The θJA of this package is ideally 80°C/W, but it will vary
depending upon the availability of copper ground plane to
which it is attached.
If we use a 2.5V output device and a 3.3V input at an output
current of 750mA, then our power dissipation is as follows:
PD = (3.3V – 2.5V) × 750mA + 3.3V × 7.5mA
PD = 600mW + 25mW
PD = 625mW
From Figure 4, the minimum amount of copper required to
operate this application at a ∆T of 75°C is 160mm2.
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Package Information
0.122 (3.10)
0.112 (2.84)
0.199 (5.05)
0.187 (4.74)
DIMENSIONS:
INCH (MM)
0.120 (3.05)
0.116 (2.95)
0.036 (0.90)
0.032 (0.81)
0.043 (1.09)
0.038 (0.97)
0.012 (0.30) R
0.012 (0.3)
0.0256 (0.65) TYP
0.008 (0.20)
0.004 (0.10)
5° MAX
0° MIN
0.007 (0.18)
0.005 (0.13)
0.012 (0.03) R
0.039 (0.99)
0.035 (0.89)
0.021 (0.53)
8-Lead MSOP (MM)
March 2003
13
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MICREL, INC.
TEL
1849 FORTUNE DRIVE SAN JOSE, CA 95131
+ 1 (408) 944-0800
FAX
+ 1 (408) 944-0970
WEB
USA
http://www.micrel.com
The information furnished by Micrel in this datasheet 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 at Purchaser’s own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2003 Micrel, Incorporated.
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