MIC3975-1.65BMM [MICREL]
750mA UCap Low-Voltage Low-Dropout Regulator; 750毫安UCAP低电压低压差稳压器
| 型号： | MIC3975-1.65BMM |
| 厂家： | 
MICREL SEMICONDUCTOR |
| 描述： | 750mA UCap Low-Voltage Low-Dropout Regulator |
| 文件： | 总12页 (文件大小：107K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC3975
750mA µCap Low-Voltage Low-Dropout Regulator
Final Information
General Description
Features
The MIC3975 is a 750mA low-dropout linear voltage regula-
tors that provide low-voltage, high-current output from an
extremely small package. Utilizing Micrel’s proprietary Super
βeta PNP™ pass element, the MIC3975 offers extremely low
dropout (typically 300mV at 750mA) and low ground current
(typically 6.5mA at 750mA).
• Fixed and adjustable output voltages to 1.24V
• 300mV 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-battery protection
TheMIC3975isidealforPCadd-incardsthatneedtoconvert
fromstandard5Vto3.3Vor3.0V, 3.3Vto2.5Vor2.5Vto1.8V
or 1.65V. A guaranteed maximum dropout voltage of 500mV
over all operating conditions allows the MIC3975 to provide
2.5V from a supply as low as 3.0V and 1.8V or 1.65V from a
supply as low as 2.25V.
• Reversed-leakage protection
• Fast transient response
• Low-profile MSOP-8
The MIC3975 is fully protected with overcurrent limiting,
thermal shutdown, and reversed-battery protection. Fixed
voltages of 5.0V, 3.3V, 3.0, 2.5V, 1.8V, and 1.65V are
available. An adjustable output voltage option is available for
voltages down to 1.24V.
Applications
• Fiber optic modules
• LDO linear regulator for PC add-in cards
• PowerPC™ power supplies
For other voltages, contact Micrel.
• 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
MSOP-8
MSOP-8
MSOP-8
MSOP-8
MSOP-8
MSOP-8
MSOP-8
MIC3975-1.65BMM
MIC3975-1.8BMM
MIC3975-2.5BMM
MIC3975-3.0BMM
MIC3975-3.3BMM
MIC3975-5.0BMM
MIC3975BMM
1.65V
1.8V
2.5V
3.0V
3.3V
5.0V
Adj.
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
Typical Applications
100k
MIC3975-2.5BMM
Error
Flag
Output
MIC3975BMM
VIN
3.3V
VIN
2.5V
IN
OUT
2.5V
IN
OUT
1.5V
R1
R1
R2
ENABLE
SHUTDOWN
ENABLE
SHUTDOWN
EN
FLG
EN
ADJ
10µF
ceramic
10µF
ceramic
GND
GND
2.5V/750mA Regulator with Error Flag
1.5V/750mA Adjustable Regulator
Super βeta PNP is a trademark of Micrel, Inc.
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
February 2003
1
MIC3975
MIC3975
Micrel
Pin Configuration
EN
IN
1
2
3
4
8
7
6
5
GND
GND
GND
GND
EN
IN
1
2
3
4
8
7
6
5
GND
GND
GND
GND
FLG
OUT
ADJ
OUT
MIC3975-x.x
Fixed
Adjustable
MSOP-8 (MM)
MSOP-8 (MM)
Pin Description
Pin No.
Fixed
Pin No.
Pin Name
Pin Function
Adjustable
1
1
EN
Enable (Input): CMOS-compatible control input. Logic high = enable, logic
low or open = shutdown.
2
3
2
3
IN
Supply (Input)
FLG
Flag (Output): Open-collector error flag output. Active low = output under-
voltage.
ADJ
Adjustment Input: Feedback input. Connect to resistive voltage-divider
network.
4
4
OUT
GND
Regulator Output
Ground
5–8
5–8
MIC3975
2
February 2003
MIC3975
Micrel
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Supply Voltage (V ) ..................................... –20V to +20V
Supply Voltage (V ) .................................. +2.25V to +16V
IN
IN
Enable Voltage (V ) ..................................................+20V
Enable Voltage (V ) ..................................................+16V
EN
EN
Storage Temperature (T ) ....................... –65°C to +150°C
Maximum Power Dissipation (P
) .................... Note 4
S
D(max)
Lead Temperature (soldering, 5 sec.) ....................... 260°C
ESD, Note 3
Junction Temperature (T ) ....................... –40°C to +125°C
J
Package Thermal Resistance
MSOP-8 (θ ) ......................................................80°C/W
JA
Electrical Characteristics(Note 12)
VIN = VOUT + 1V; VEN = 2.25V; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C; unless noted
Symbol
Parameter
Condition
Min
Typ
Max
Units
VOUT
Output Voltage
10mA
–1
–2
1
2
%
%
10mA ≤ IOUT ≤ 750mA, VOUT + 1V ≤ VIN ≤ 8V
Line Regulation
Load Regulation
IOUT = 10mA, VOUT + 1V ≤ VIN ≤ 16V
VIN = VOUT + 1V, 10mA ≤ IOUT ≤ 750mA,
0.06
0.2
40
0.5
1
%
%
∆VOUT/∆T
Output Voltage Temp. Coefficient,
100 ppm/°C
Note 5
VDO
Dropout Voltage, Note 6
IOUT = 100mA, ∆VOUT = –1%
140
200
250
mV
mV
IOUT = 500mA, ∆VOUT = –1%
IOUT = 750mA, ∆VOUT = –1%
IOUT = 100mA, VIN = VOUT + 1V
IOUT = 500mA, VIN = VOUT + 1V
IOUT = 750mA, VIN = VOUT + 1V
VOUT = 0V, VIN = VOUT + 1V
225
300
400
4
mV
mV
µA
mA
mA
A
500
IGND
Ground Current, Note 7
7.5
1.8
15
IOUT(lim)
Enable Input
VEN
Current Limit
2.5
Enable Input Voltage
Enable Input Current
logic low (off)
logic high (on)
VEN = 2.25V
0.8
V
V
2.25
IEN
1
15
30
75
µA
µA
VEN = 0.8V
2
4
µA
µA
Flag Output
IFLG(leak)
Output Leakage Current
Output Low Voltage
VOH = 16V
0.01
210
1
2
µA
µA
VFLG(do)
VFLG
VIN = 2.250V, IOL, = 250µA, Note 9
300
400
mV
mV
Low Threshold
High Threshold
Hysteresis
% of VOUT
% of VOUT
93
%
%
%
99.2
1
February 2003
3
MIC3975
MIC3975
Micrel
Symbol
Parameter
Condition
Min
Typ
Max
Units
Adjustable Output Only
Reference Voltage
1.228 1.240 1.252
V
V
V
1.215
1.203
1.265
1.277
Note 10
Note 11
Adjust Pin Bias Current
40
20
80
120
nA
nA
Reference Voltage
Temp. Coefficient
ppm/°C
Adjust Pin Bias Current
Temp. Coefficient
0.1
nA/°C
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.
P
= (T
– T ) ÷ θ , where θ depends upon the printed circuit layout. See “Applications Information.”
J(max) A JA JA
D(max)
Note 5. Output voltage temperature coefficient is ∆V
÷ (T
– T
) where T
is +125°C and T is –40°C.
J(min)
OUT(worst case)
J(max)
J(min)
J(max)
Note 6.
V
= V – V
when V
decreases to 98% of its nominal output voltage with V = V
+ 1V. For output voltages below 2.25V, dropout
OUT
DO
IN
OUT
OUT
IN
voltage is the input-to-output voltage differential with the minimum input voltage being 2.25V. Minimum input operating voltage is 2.25V.
Note 7.
Note 8.
I
is the quiescent current. I = I + I
.
OUT
GND
IN
GND
V
≤ 0.8V, V ≤ 8V, and V
= 0V.
OUT
EN
IN
Note 9. For a 2.5V device, V = 2.250V (device is in dropout).
IN
Note 10. V
≤ V
≤ (V – 1V), 2.25V ≤ V ≤ 16V, 10mA ≤ I ≤ 750mA, T = T
.
REF
OUT
IN
IN
L
J
MAX
Note 11. Thermal regulation is defined as the change in output voltage at a time t after a change in power dissipation is applied, excluding load or line
regulation effects. Specifications are for a 200mA load pulse at V = 16V for t = 10ms.
IN
Note 12. Specification for packaged product only.
MIC3975
4
February 2003
MIC3975
Micrel
Typical Characteristics
Power Supply
Rejection Ratio
Power Supply
Rejection Ratio
Power Supply
Rejection Ratio
80
80
60
40
20
0
80
60
40
20
0
VIN = 5V
VOUT = 3.3V
VIN = 5V
VOUT = 3.3V
VIN = 3.3V
VOUT = 2.5V
60
40
IOUT = 750mA
20
IOUT = 750mA
COUT = 47µF
CIN = 0
IOUT = 750mA
COUT = 10µF
CIN = 0
COUT = 10µF
CIN = 0
0
1E+1 1E+2 1E+3 1E+4 1E+5 1E+6
1E+1 1E+2 1E+3 1E+4 1E+5 1E+6
1k
10k 1M
1E+1 1E+2 1E+3 1E+4 1E+5 1E+6
1k
10k
1M
1k
10k
1M
10
100
100k
10
100
100k
10
100
100k
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
Power Supply
Dropout Voltage
Dropout Voltage
vs. Temperature
Rejection Ratio
vs. Output Current
80
350
400
VIN = 3.3V
VOUT = 2.5V
300
250
200
150
100
50
2.5V
2.5V
60
40
20
0
350
300
250
200
1.8V
3.3V
1.8V
IOUT = 750mA
COUT = 47µF
CIN = 0
3.3V
TA = 25°C
500
ILOAD = 750mA
0
1E+1 1E+2 1E+3 1E+4 1E+5 1E+6
1k
10k
0
250
750
-40 -20
0
20 40 60 80 100120140
1M
3.5
8
10
100
100k
FREQUENCY (Hz)
OUTPUT CURRENT (mA)
TEMPERATURE (°C)
Dropout Characteristics
(2.5V)
Dropout Characteristics
(3.3V)
Ground Current
vs. Output Current
2.8
3.6
3.4
3.2
3.0
2.8
2.6
2.4
10
9
8
7
6
5
4
3
2
1
0
2.6
2.4
2.2
2.0
1.8
1.6
1.4
I
=100mA
I
=100mA
LOAD
LOAD
1.8V
2.5V
I
LOAD
=750mA
3.3V
I
LOAD
=750mA
0
250
500
750
2
2.3
2.6
2.9
3.2
2.8
3.2
3.6
4.0
4.4
OUTPUT CURRENT (mA)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
Ground Current
vs. Supply Voltage (2.5V)
Ground Current
vs. Supply Voltage (3.3V)
Ground Current
vs. Supply Voltage (2.5V)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
30
25
20
15
10
5
I
=100mA
LOAD
I
=100mA
=10mA
LOAD
I
LOAD
I
=10mA
LOAD
I
= 750mA
LOAD
0
0
2
4
6
0
2
4
6
8
0
2
4
6
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
February 2003
5
MIC3975
MIC3975
Micrel
Ground Current
vs. Supply Voltage (3.3V)
Ground Current
vs. Temperature
Ground Current
vs. Temperature
30
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
1.0
0.8
0.6
0.4
0.2
0
I
=750mA
LOAD
2.5V
3.3V
25
20
15
10
5
I
=10mA
LOAD
1.8V
3.3V
2.5V
1.8V
ILOAD = 500mA
0
0
1
2
3
4
5
6
-40 -20
0
20 40 60 80 100 120
-40 -20
0
20 40 60 80 100 120
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
Output Voltage
vs. Temperature
Ground Current
vs. Temperature
Short Circuit
vs. Temperature
9
8
8
7
7
6
6
5
3.40
3.35
3.30
3.25
3.20
2.5
2.0
1.5
1.0
0.5
0
2.5V
3.3V
Typical 3.3V
Device
1.8V
2.5V
1.8V
3.3V
ILOAD = 750mA
-40 -20
0 20 40 60 80 100120140
-40 -20
0
20 40 60 80 100 120
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
Error Flag
Pull-Up Resistor
Enable Current
vs. Temperature
Flag-Low Voltage
vs. Temperature
12
10
8
250
200
150
100
50
6
5
4
3
2
1
VIN = 5V
VIN = VOUT + 1V
FLAG-LOW
VOLTAGE
VEN = 2.4V
FLAG HIGH
(OK)
6
VIN = 2.25V
RPULL-UP = 22kΩ
4
FLAG LOW
(FAULT)
2
0
0
0
0.01 0.1
1
10 100 100010000
-40 -20
0
20 40 60 80 100120140
-40 -20
0
20 40 60 80 100120140
RESISTANCE (kΩ)
TEMPERATURE (°C)
TEMPERATURE (°C)
MIC3975
6
February 2003
MIC3975
Micrel
Functional Characteristics
Load Transient Response
Load Transient Response
VIN = 3.3V
VOUT = 2.5V
COUT = 10µF Ceramic
VIN = 3.3V
VOUT = 2.5V
COUT = 10µF Ceramic
750mA
750mA
100mA
10mA
TIME (200µs/div.)
TIME (200µs/div.)
Line Transient Response
5.0V
3.3V
VOUT = 2.5V
COUT = 10µF Ceramic
ILOAD = 10mA
TIME (200µs/div.)
February 2003
7
MIC3975
MIC3975
Micrel
Functional Diagrams
OUT
IN
O.V.
ILIMIT
18V
1.180V
1.240V
Ref.
FLAG
EN
Thermal
Shut-
down
GND
MIC3975 Fixed Regulator with Flag and Enable Block Diagram
OUT
IN
O.V.
ILIMIT
18V
1.240V
Ref.
ADJ
EN
Thermal
Shut-
down
GND
MIC3975 Adjustable Regulator Block Diagram
MIC3975
8
February 2003
MIC3975
Micrel
Input Capacitor
Applications Information
An input capacitor of 1µF or greater is recommended when
thedeviceismorethan4inchesawayfromthebulkacsupply
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 bypass-
ing the input to the regulator, further improving the integrity of
the output voltage.
The MIC3975 is a high-performance low-dropout voltage
regulator suitable for moderate to high-current voltage regu-
lator applications. Its 500mV dropout voltage at full load and
overtemperature makes it especially valuable in battery-
powered systems and as high-efficiency noise filters in post-
regulator applications. Unlike older NPN-pass transistor de-
signs, where the minimum dropout voltage is limited by the
base-to-emitter voltage drop and collector-to-emitter satura-
tion voltage, dropout performance of the PNP output of these
Error Flag
The MIC3975 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
devices is limited only by the low V saturation voltage.
CE
A trade-off for the low dropout voltage is a varying base drive
requirement. Micrel’s Super βeta PNP™ process reduces
this drive requirement to only 2% of the load current.
The MIC3975 regulator is fully protected from damage due to
fault conditions. Linear current limiting is provided. Output
current during overload conditions is constant. Thermal shut-
down disables the device when the die temperature exceeds
the maximum safe operating temperature. Transient protec-
tion allows device (and load) survival even when the input
voltage spikes above and below nominal. The output struc-
ture of these regulators allows voltages in excess of the
desired output voltage to be applied without reverse current
flow.
pull-up resistor from FLG to either V or V
is required for
IN
OUT
properoperation.Forinformationregardingtheminimumand
maximum values of pull-up resistance, refer to the graph in
the typical characteristics section of the data sheet.
Enable Input
The MIC3975 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 microam-
peres of leakage current. The EN input has TTL/CMOS
compatiblethresholdsforsimplelogicinterfacing. ENmaybe
MIC3975x.x
VIN
VOUT
IN
OUT
GND
directly tied to V and pulled up to the maximum supply
CIN
COUT
IN
voltage
Transient Response and 3.3V to 2.5V or 2.5V to 1.8V or
1.65V Conversion
Figure 1. Capacitor Requirements
Output Capacitor
The MIC3975 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, isallthatisrequired. Largervalueshelptoimprove
performance even further.
The MIC3975 requires an output capacitor for stable opera-
tion. As aµCap LDO, the MIC3975 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
MIC3975 is 4.7µF.
By virtue of its low-dropout voltage, this device does not
saturate into dropout as readily as similar NPN-based de-
signs. 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.
Toconvertdownto2.5Vor1.8Vwithoutoperatingindropout,
NPN-based regulators require an input voltage of 3.7V at the
very least. The MIC3975 regulator will provide excellent
performance with an input as low as 3.0V or 2.5V respec-
tively. This gives the PNP based regulators a distinct advan-
tage over older, NPN based linear regulators.
For10µForgreatertheESRrangerecommendedislessthan
1Ω. Ultra-low ESR ceramic capacitors are recommended for
output capacitance of 10µF or greater to help improve tran-
sient response and noise reduction at high frequency.
X7R/X5R dielectric-type ceramic capacitors are recom-
mended because of their temperature performance. X7R-
type capacitors change capacitance by 15% over their oper-
ating temperature range and are the most stable type of
ceramiccapacitors.Z5UandY5Vdielectriccapacitorschange
value by as much as 50% and 60% respectively over their
operatingtemperatureranges. Touseaceramicchipcapaci-
torwithY5Vdielectric, thevaluemustbemuchhigherthanan
X7R ceramic capacitor to ensure the same minimum capaci-
tance over the equivalent operating temperature range.
Minimum Load Current
The MIC3975 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.
February 2003
9
MIC3975
MIC3975
Micrel
Adjustable Regulator Design
sink thermal resistance) and θ
(sink-to-ambient thermal
SA
resistance).
Using the power MSOP-8 reduces the θ dramatically and
JC
MIC3975
allows the user to reduce θ . The total thermal resistance,
VIN
IN
OUT
VOUT
COUT
CA
R1
R2
θ
(junction-to-ambient thermal resistance) is the limiting
JA
ENABLE
SHUTDOWN
EN
ADJ
factor in calculating the maximum power dissipation capabil-
GND
ity of the device. Typically, the power MSOP-8 has a θ of
JA
80°C/W, this is significantly lower than the standard MSOP-8
R1
R2
which is typically 160°C/W. θ is reduced because pins 5
V
= 1.240V 1+
CA
OUT
through 8 can now be soldered directly to a ground plane
which significantly reduces the case-to-sink thermal resis-
tance and sink to ambient thermal resistance.
Figure 2. Adjustable Regulator with Resistors
The MIC3975 allows programming the output voltage any-
wherebetween1.24Vandthe16Vmaximumoperatingrating
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:
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 opera-
tionofthedevice.Topreventthismaximumjunctiontempera-
ture from being exceeded, the appropriate ground plane heat
sink must be used.
VOUT
R1= R2
−1
1.240
Where V is the desired output voltage. Figure 2 shows
MSOP-8
O
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
θJA
One of the secrets of the MIC3975’s performance is its power
MSO-8 package featuring half the thermal resistance of a
standard MSO-8 package. Lower thermal resistance means
more output current or higher input voltage for a given
package size.
ground plane
heat sink area
θJC
θCA
AMBIENT
printed circuit board
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.
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 maxi-
mum allowable temperature rise must be calculated to deter-
mine operation along which curve.
Thermal resistance consists of two main elements, θ
JC
(junction-to-casethermalresistance)andθ (case-to-ambi-
CA
ent thermal resistance). See Figure 3. θ is the resistance
JC
from the die to the leads of the package. θ is the resistance
CA
from the leads to the ambient air and it includes θ (case-to-
CS
900
800
700
600
500
400
300
200
100
0
900
T
= 125°C
85°C
800
700
600
500
400
300
200
100
0
J
50°C 25°C
0
0.25 0.50 0.75 1.00 1.25 1.50
POWER DISSIPATION (W)
0
0.25 0.50 0.75 1.00 1.25 1.50
POWER DISSIPATION (W)
Figure 4. Copper Area vs. Power-MSOP
Power Dissipation (∆T
Figure 5. Copper Area vs. Power-MSOP
)
Power Dissipation (T )
JA
A
MIC3975
10
February 2003
MIC3975
∆T = T
Micrel
Quick Method
– T
J(max)
A(max)
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 maxi-
mum 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
T
T
= 125°C
J(max)
A(max)
= maximum ambient operating temperature
Forexample, themaximumambienttemperatureis50°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 fol-
lows:
2
copper is 160mm .
The θ of this package is ideally 80°C/W, but it will vary
JA
depending upon the availability of copper ground plane to
which it is attached.
P = (V – V
) I
+ V × I
D
IN
OUT OUT IN GND
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:
P = (3.3V – 2.5V) × 750mA + 3.3V × 7.5mA
D
P = 600mW + 25mW
D
P = 625mW
D
From Figure 4, the minimum amount of copper required to
2
operate this application at a ∆T of 75°C is 160mm .
February 2003
11
MIC3975
MIC3975
Micrel
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
0.007 (0.18)
0.005 (0.13)
0.008 (0.20)
0.004 (0.10)
5° MAX
0° MIN
0.012 (0.3)
0.012 (0.03) R
0.039 (0.99)
0.0256 (0.65) TYP
0.035 (0.89)
0.021 (0.53)
8-Lead MSOP (MM)
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TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB 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.
MIC3975
12
February 2003
相关型号：
MIC3975-1.65YMMTR
1.65V FIXED POSITIVE LDO REGULATOR, 0.5V DROPOUT, PDSO8, LEAD FREE, MSOP-8
MICROCHIP
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