MIC3775
750mA µCap Low-Voltage
Low-Dropout Regulator
PowerPC is a trademark of IBM Corp.
Super βeta PNP is a registered trademark of Micrel, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
408
) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
December 2006
1 M9999-121906
General Description
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 1.8Vor 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.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
Features
• 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
• 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
___________________________________________________________________________________________________________
Typical Application
1.25V/750mA Adjustable Regulator
Micrel, Inc. MIC3775
December 2006
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Ordering Information
Part Number
Standard Pb-Free
Voltage Junction
Temp. Range Package
MIC3775-1.5BMM MIC3775-1.5YMM 1.5V –40° to +125°C 8-Pin MSOP
MIC3775-1.65BMM MIC3775-1.65YMM 1.65V –40° to +125°C 8-Pin MSOP
MIC3775-1.8BMM MIC3775-1.8YMM 1.8V –40° to +125°C 8-Pin MSOP
MIC3775-2.5BMM MIC3775-2.5YMM 2.5V –40° to +125°C 8-Pin MSOP
MIC3775-3.0BMM MIC3775-3.0YMM 3.0V –40° to +125°C 8-Pin MSOP
MIC3775-3.3BMM MIC3775-3.3YMM 3.3V –40° to +125°C 8-Pin MSOP
MIC3775BMM MIC3775YMM Adj. –40° to +125°C 8-Pin MSOP
Note: For other voltages. Contact Micrel Marketing for details.
Pin Configuration
MIC3775-x.x (Fixed)
8-Pin MSOP (MM)
MIC3775 (Adjustable)
8-Pin MSOP (MM)
Pin Description
Pin Number Pin Name Pin Function
1 EN
Enable (Input): CMOS-compatible control input. Logic high = enable, logic low
or open = shutdown.
2 IN Supply (Input).
FLG Flag (Output): Open-collector error flag output. Active low = output under-
voltage.
3
ADJ Adjustment Input: Feedback input. Connect to resistive voltage-divider network.
4 OUT Regulator Output.
5 – 8 GND Ground.
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Absolute Maximum Ratings(1)
Supply Voltage (V
IN
)......................................................6.5V
Enable Voltage (V
EN
).....................................................6.5V
Lead Temperature (soldering, 5 sec.)........................ 260°C
Storage Temperature (T
s
) .........................–65°C to +150°C
EDS Rating................................................................ Note 3
Operating Ratings(2)
Supply Voltage (V
IN
)...................................... +2.25V to +6V
Enable Voltage (V
EN
)............................................ 0V to +6V
Maximum Power Dissipation (P
D(MAX)
) ...................... Note 4
Junction Temperature (T
J
) ........................–40°C to +125°C
Package Thermal Resistance
MSOP-8 (θ
JA
).....................................................80°C/W
Electrical Characteristics(5)
V
IN
= V
OUT
+ 1V; V
EN
= 2.25V; T
J
= 25°C, bold values indicate –40°C< T
J
< +125°C, unless noted.
Symbol Parameter Condition Min Typ Max Units
V
OUT
Output Voltage 10mA
10mA ≤ I
OUT
≤ 750mA, V
OUT
+ 1V ≤ V
IN
≤ 6V
–1
–2
1
2
%
%
Line Regulation I
OUT
= 10mA, V
OUT
+ 1V ≤ V
IN
≤ 6V 0.06 0.5 %
Load Regulation V
IN
= V
OUT
+ 1V, 10mA ≤ I
OUT
≤ 750mA 0.2 1 %
∆V
OUT
/∆T Output Voltage Temp.
Coefficient, Note 6
40 ppm/°C
I
OUT
= 100mA, ∆V
OUT
= –1% 125 200
250
mV
mV
I
OUT
= 500mA, ∆V
OUT
= –1% 210 mV
V
DO
Dropout Voltage, Note 7
I
OUT
= 750mA, ∆V
OUT
= –1% 280 500 mV
I
OUT
= 100mA, V
IN
= V
OUT
+ 1V 700 µA
I
OUT
= 500mA, V
IN
= V
OUT
+ 1V 3.7 mA
I
GND
Ground Current, Note 8
I
OUT
= 750mA, V
IN
= V
OUT
+ 1V 7.5 15 mA
I
OUT(lim)
Current Limit V
OUT
= 0V, V
IN
= V
OUT
+ 1V 1.6 2.5 A
Enable Input
logic low (off) 0.8 V V
EN
Enable Input Voltage
logic high (on) 2.25 V
V
EN
= 2.25V 1 10 30 µA I
EN
Enable Input Current
V
EN
= 0.8V 2
4
µA
µA
Flag Output
I
FLG(leak)
Output Leakage Current V
OH
= 6V 0.01 1
2
µA
µA
V
FLG(do)
Output Low Voltage V
IN
= 2.250V, I
OL
, = 250µA 250 500 mV
Low Threshold % of V
OUT
93 %
High Threshold % of V
OUT
99.2 %
V
FLG
Hysteresis 1 %
Adjustable Output Only
Reference Voltage 1.227
1.215
1.240 1.252
1.265
V
V
Adjust Pin Bias Current 40 80
120
nA
nA
Micrel, Inc. MIC3775
December 2006
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Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive. Handling precautions recommended.
4. P
D(max)
= (T
J(max)
– T
A
) ÷ θ
JA
, where θ
JA
depends upon the printed circuit layout. See “Applications Information.”
5. Specification for packaged product only.
6. Output voltage temperature coefficient is ∆V
OUT(worst case)
÷ (T
J(max)
– T
J(min)
) where T
J(max)
is +125°C and T
J(min)
is –40°C.
7. V
DO
= V
IN
– V
OUT
when V
OUT
decreases to 98% of its nominal output voltage with V
IN
= V
OUT
+ 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.
8. I
GND
is the quiescent current. I
IN
= I
GND
+ I
OUT
.
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December 2006
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Typical Characteristics
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December 2006
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Typical Characteristics (cont.)
Micrel, Inc. MIC3775
December 2006
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Typical Characteristics (cont.)
Micrel, Inc. MIC3775
December 2006
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Functional Characteristics
Micrel, Inc. MIC3775
December 2006
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Functional Diagrams
MIC3775 Fixed Regulator with Flag and Enable Block Diagram
MIC3775 Adjustable Regulator Block Diagram
Micrel, Inc. MIC3775
December 2006
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Application 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
battery-powered systems and as high-efficiency noise
filters in post-regulator 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 perform-
ance of the PNP output of these devices is limited only
by the low V
CE
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.
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. X7R-type 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.
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 V
IN
or V
OUT
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 V
IN
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
Micrel, Inc. MIC3775
December 2006
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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.
Adjustable Regulator Design
⎟
⎠
⎞
⎜
⎝
⎛+= R2
R1
11.240VV
OUT
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:
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛−= 1
1.240
V
R2R1
OUT
Where V
O
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
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.
Thermal resistance consists of two main elements, θ
JC
(junction-to-case thermal resistance) and θ
CA
(case-to-
ambient thermal resistance). See Figure3. θ
JC
is the
resistance from the die to the leads of the package. θ
CA
is the resistance from the leads to the ambient air and it
includes θ
CS
(case-to- sink thermal resistance) and θ
SA
(sink-to-ambient thermal resistance).
Using the power MSOP-8 reduces the θ
JC
dramatically
and allows the user to reduce θ
CA
. The total thermal
resistance, θ
JA
(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 θ
JA
of 80°C/W, this is significantly lower
than the standard MSOP-8 which is typically 160°C/W.
θ
CA
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.
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 deter-
mined. The maximum allowable temperature rise must
be calculated to determine operation along which curve.
Figure 4. Copper Area vs. Power-MSOP
Power Dissipation (∆T
JA
)
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December 2006
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Figure 5. Copper Area vs. Power-MSOP
Power Dissipation (T
A
)
∆T = T
J(max)
– T
A(max)
T
J(max)
= 125°C
T
A(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:
P
D
= (V
IN
– V
OUT
) I
OUT
+ V
IN
×I
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
D
= (3.3V – 2.5V) × 750mA + 3.3V × 7.5mA
P
D
= 600mW + 25mW
P
D
= 625mW
From Figure 4, the minimum amount of copper required
to operate this application at a ∆T of 75°C is 160mm
2
.
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 160mm
2
.The θ
JA
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.
Micrel, Inc. MIC3775
December 2006
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Package Information
8-Pin MSOP (MM)
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
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 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.
© 2002 Micrel, Incorporated.
