MICREL MIC37122YM

MIC37110/MIC37112
MIC37120/MIC37122
High-Performance, Low-Noise,
1A LDOs
General Description
Features
The MIC37110/MIC37112 and MIC37120/MIC37122 are
high-performance, low-noise, low dropout regulators. Each
of these LDOs is capable of sourcing 1A output current,
offers high power supply rejection, and low output noise.
These general purpose LDOs are most suitable for
consumer applications such as multimedia devices, set-top
boxes, Blu-ray players, handheld devices, and gaming
consoles.
The MIC37112 and MIC37122 feature adjustable output
voltages while the MIC37110 and MIC37120 come in fixed
1.8V output voltage options. All devices feature 2% initial
output voltage accuracy, typical dropout of 230mV at 1A,
and low ground current.
This family of low-noise regulators is available in 2mm x
®
2mm Thin MLF , SOIC-8 and SOT-223 packages and they
all have an operating junction 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.
• Input voltage range: 2.375V to 5.5V
• Output voltage adjustable down to 1.0V
(MIC37112/MIC37122)
• Stable with small, 2.2µF ceramic output capacitor
• 230mV typical dropout at 1A
• 1A minimum guaranteed output current
• ±2.0% initial accuracy
• Low ground current
• High PSRR: >60dB, up to 1kHz
• Output auto-discharge circuit (MIC37120/MIC37122)
• Thermal-shutdown and current-limit protection
Applications
•
•
•
•
•
Mobile phones and consumer multimedia devices
Set-top boxes and Blu-ray players
Gaming consoles
Tablets and handheld devices
GPS receivers
___________________________________________________________________________________________________________
Typical Application
Dropout Voltage
vs. Output Current
DROPOUT VOLTAGE (mV)
400
VIN = 2.5V
VADJ = 0.95 * 1.0V
ADJUSTABLE OPTION
300
TA = 25ºC
200
100
0
0.0
0.2
0.4
0.6
0.8
1.0
OUTPUT CURRENT (A)
MLF and MicroLeadFrame are registered trademarks of Amkor Technology, 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 2012
M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Ordering Information
(1,2)
Part Number
Output Voltage
Top Mark
Output Auto-Discharge
Package
MIC37110-1.8YS
1.8V
ZHG
No
SOT-223-3L
MIC37110-1.8YM
1.8V
−
No
SOIC-8L
MIC37110-1.8YMT
1.8V
GHZ
No
2mm × 2mm Thin MLF-6L
Adjustable
−
No
SOIC-8L
No
2mm × 2mm Thin MLF-6L
SOIC-8L
MIC37112YM
Adjustable
AZZ
MIC37120-1.8YM
1.8V
−
Yes
MIC37120-1.8YMT
1.8V
1H8
Yes
2mm × 2mm Thin MLF-6L
MIC37122YM
Adjustable
−
Yes
SOIC-8L
MIC37122YMT
Adjustable
ZAZ
Yes
2mm × 2mm Thin MLF-6L
MIC37112YMT
Note:
1.
RoHS compliant with ‘high-melting solder’ exemption.
2.
Temperature range is -40°C to +125°C
Pin Configuration
December 2012
SOT-223 (S)
MIC371x0-1.8 (Fixed)
2mm x 2mm Thin MLF - 6 Lead (MT)
MIC371xx (Fixed/Adjustable)
8-Pin SOIC (M)
MIC371x0-1.8 (Fixed)
8-Pin SOIC (M)
MIC371x2 (Adjustable)
2
M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Pin Description
Pin Number
SOIC-8
Pin Number
SOIC-8
(Fixed)
—
Pin Name
(Adjustable)
Pin Number
2mm × 2mm
Thin MLF-6L
1
1
1
EN
1
2
2
3
IN
3
3
3
4
OUT
Regulator Output.
4
5
ADJ
Adjustment Input: Feedback input. Connect to
resistive voltage-divider network to set the output
voltage of the MIC37112/MIC37122.
—
5
SNS
Output Voltage Sense Input. Connect this pin at
the point-of-load to monitor the output voltage of
the fixed output voltage options.
Ground.
Pin Number
SOT-223 -3L
—
—
2, TAB
5-8
5-8
2
GND
—
4
—
6
NC
December 2012
3
Pin Description
Enable (Input): CMOS-compatible control input.
Logic high = enable, logic low = shutdown.
Supply (Input).
Not internally connected
M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VIN) ......................................... -0.3V to +6V
Enable Voltage (VEN). ....................................... -0.3V to +VIN
Adjust Pin Voltage (VADJ).................................. -0.3V to +VIN
Lead Temperature (soldering, 5s) .............................. 260°C
Storage Temperature (Ts) ......................... –65°C to +150°C
(3)
ESD Rating
HBM ......................................................................... 3kV
Supply Voltage (VIN) ................................. +2.375V to +5.5V
Enable Voltage (VEN). ............................................. 0V to VIN
(4)
Power Dissipation (PD(max))………………Internally Limited
Junction Temperature (TJ) ........................ –40°C to +125°C
Package Thermal Resistance
SOT-223 (θJA) .................................................... 40°C/W
SOIC-8 (θJA) ....................................................... 63°C/W
Thin MLF-6 (θJA) .............................................. 100°C/W
Electrical Characteristics(5)
VIN = VEN = VOUT + 1V; IOUT = 10mA; CIN = 1.0 µF; COUT = 2.2µF; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C, unless noted.
Parameter
Condition
Min.
Typ.
Max.
Units
5.5
V
2.2
V
Power Supply Input
2.375
Input Voltage Range (VIN)
Input Supply UVLO
100
Input Supply UVLO Hysteresis
Ground Pin Current
(6)
Ground Current in Shutdown
mV
10mA ≤ IOUT ≤ 1.0A
250
500
µA
VEN = VOUT = 0V
0.1
5
µA
1
1.025
V
Reference
Adjust Pin Voltage
Adjustable Option
Output Voltage Accuracy
Fixed Option
Load Regulation
IOUT = 10mA to 1A
Line Regulation
VIN = (VOUT + 1V) to 5.5V
ADJ Pin Current
VADJ = 1.0V
0.975
-2
+2
-2.5
+2.5
-1.0
+1.0
%
0.05
0.5
%
0.01
1
µA
2.3
4.0
A
230
400
mV
%
Current Limit
Current Limit
VOUT = 0V
1.2
Dropout Voltage
Dropout Voltage (VIN − VOUT)
(7)
IOUT = 1A
Load Discharge Resistance (MIC37120/MIC37122)
Load Discharge Resistance
VEN = 0V; VIN = 3.6V; IOUT = 3mA
30
Ω
0.75
V
Enable Input
1.2
Enable Logic Level High
Enable Logic Level Low
0.65
EN Hysteresis
100
EN Pin Current
December 2012
0.25
mV
VEN = 0.2V (Regulator Shutdown)
0.1
1
VIN = VEN = 3.6V (Regulator Enabled)
0.1
1
4
V
µA
M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Electrical Characteristics(5) (Continued)
VIN = VEN = VOUT + 1V; IOUT = 10mA; CIN = 1.0 µF; COUT = 2.2µF; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C, unless noted.
Parameter
Condition
Min.
Typ.
Max.
Units
140
500
µs
Enable Input
Start-Up Time
Minimum Load Current
10
Minimum Load Current
mA
Thermal Protection
Over-Temperature Shutdown
TJ Rising
160
°C
15
°C
Over-Temperature Shutdown
Hysteresis
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.
PD(max) = (TJ(max) – TA) ÷ θJA, where θJA depends upon the printed circuit layout. See “Applications Information” section.
5.
Specification for packaged product only.
6.
IGND is the quiescent current. IIN = IGND + IOUT.
7.
VDO = VIN – VOUT when VOUT decreases to 98% of its nominal output voltage with VIN = VOUT + 1V. For output voltages below 2.25V, dropout voltage
is the input-to-output voltage differential with the minimum input voltage being 2.25V. The minimum input operating voltage is 2.375V.
December 2012
5
M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Typical Characteristics
GND Pin Current
vs. Input Voltage
Dropout Voltage
vs. Input Voltage
500
250
200
IOUT = 1A
150
100
IOUT = 500mA
50
1.0
VOUT = VIN - 1.0V
400
IOUT = 1A
300
200
100
0
0
2
3
4
5
3
5
6
VOUT = 1.0V
IOUT = 10mA
1.000
0.995
0.990
5
6
15
10
5
4
5
6
0.10
0.05
3
0
INPUT VOLTAGE (V)
6
5
6
Load Discharge Resistance
vs. Input Voltage
80
VOUT = VIN - 1.0V
(ADJUSTABLE OPTION)
IOUT = 10mA TO 1A
0.4
0.3
0.2
0.1
VEN = 0V
IOUT = 3mA
60
40
20
0
0.0
5
4
INPUT VOLTAGE (V)
DISCHARGE RESISTANCE (Ω)
LOAD REGULATION (%)
1
December 2012
0.15
Load Regulation
vs. Input Voltage
2
4
VEN = 3.6V
2
0.5
3
IOUT = 10mA
0.00
3
Current Limit
vs. Input Voltage
VOUT = 0V
6
VOUT = 1.0V
0.20
INPUT VOLTAGE (V)
3
5
0.25
2
4
4
Enable Pin Current
vs. Input Voltage
VADJ = 1.0V
INPUT VOLTAGE (V)
2
3
INPUT VOLTAGE (V)
0
4
0.2
2
ENABLE PIN CURRENT (µA)
ADJ PIN CURRENT (nA)
ADJ PIN VOLTAGE (V)
4
20
3
0.4
Adjust Pin Current
vs. Input Voltage
1.010
2
0.6
INPUT VOLTAGE (V)
Adjust Pin Voltage
vs. Input Voltage
1.005
VOUT = 0V
VEN = 0V
0.8
0.0
2
6
INPUT VOLTAGE (V)
CURRENT LIMIT (A)
GROUND CURRENT (µA)
ADJUSTABLE OPTION
VADJ = 0V
GROUND CURRENT (µA)
DROPOUT VOLTAGE (mV)
300
Shutdown Ground Current
vs. Input Voltage
2
3
4
5
INPUT VOLTAGE (V)
6
6
2
3
4
5
6
INPUT VOLTAGE (V)
M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Typical Characteristics (Continued)
GND Pin Current
vs. Temperature
Shutdown Ground Current
vs. Temperature
2.50
400
300
200
100
0
UVLO THRESHOLD (V)
2.0
VIN = 2.5V
VOUT = 1.5V
IOUT = 500mA
GROUND CURRENT (µA)
GROUND CURRENT (µA)
500
1.5
VIN =2.375V
VOUT = 0V
1.0
0.5
0.0
-50
-25
0
25
50
75
100
125
VIN UVLO Threshold
vs. Temperature
2.25
2.00
1.75
1.50
-50
-25
0
TEMPERATURE (°C)
25
50
75
100
125
-50
-25
TEMPERATURE (°C)
Dropout Voltage
vs. Temperature
Dropout Voltage
vs. Temperature
500
0
25
50
75
100
125
TEMPERATURE (°C)
Current Limit
vs. Temperature
500
VADJ = 0.95 * 1.0V
ADJUSTABLE OPTION
400
IOUT = 1A
300
200
100
IOUT = 500mA
VIN = 3.3V
400
300
IOUT = 1A
200
100
0
-50
-25
0
25
50
75
100
-25
Adjust Pin Voltage
vs. Temperature
1.02
0
25
50
75
100
125
-50
15
10
5
0
0.98
25
50
75
TEMPERATURE (°C)
December 2012
100
125
50
75
100
125
VIN = 2.5V to 5.5V
LINE REGULATION (%)
ADJ PIN CURRENT (nA)
0.99
25
1.0
VADJ = 1.0V
1.00
0
Line Regulation
vs. Temperature
VOUT = 1.5V
IOUT = 10mA
-25
Adjust Pin Current
vs. Temperature
VIN = 3.3V
0
1
TEMPERATURE (°C)
VIN = 2.5V
-25
2
TEMPERATURE (°C)
20
-50
3
0
-50
125
TEMPERATURE (°C)
1.01
VOUT = 0V
IOUT = 500mA
0
ADJ PIN VOLTAGE (V)
VIN = 2.5V
VADJ = 0.95 * 1.0V
ADJUSTABLE OPTION
CURRENT LIMIT (A)
DROPOUT VOLTAGE (mV)
DROPOUT VOLTAGE (mV)
4
VIN = 2.375V
VOUT = 1.5V
0.8
IOUT = 10mA
0.6
0.4
0.2
0.0
-50
-25
0
25
50
75
TEMPERATURE (°C)
7
100
125
-50
-25
0
25
50
75
100
125
TEMPERATURE (°C)
M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Typical Characteristics (Continued)
300
200
100
VIN = 2.5V
VIN = 3.3V
ADJ PIN VOLTAGE (V)
VADJ = 0.95 * 1.0V
ADJUSTABLE OPTION
0
VADJ = 0.95 * 1.0V
ADJUSTABLE OPTION
300
200
100
0
0.0
0.2
0.4
0.6
0.8
1.0
VOUT = 1.8V
1.005
1.000
0.995
0.990
0.0
0.2
0.8
0.6
0.4
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
Line Regulation
vs. Output Current
GND Pin Current
vs. Output Current
1.0
0.0
0.2
0.4
VOUT = 1.4V
0.6
0.4
0.2
0.0
-0.2
VOUT = 1.8V
300
200
100
0
0.0
0.2
0.4
0.6
0.8
1.0
0.0
-10
-20
0.4
0.6
0.8
OUTPUT CURRENT (A)
PSRR vs. Frequency
PSRR vs. Frequency
1.0
Noise Spectral
Density
1
0.1
VIN =2.5V
VOUT = 1.8V
0.01
IOUT = 500mA
COUT = 10µF
0.001
0.01
0.1
1
10
100
1000
FREQUENCY (kHz)
10
Gain (dB)
VIN =2.8V
VOUT = 1.8V
VRIPPLE = 80mV
IOUT = 100mA
CIN = 0uF
COUT = 10uF
0
RIPPLE REJECTION (dB)
0
0.2
OUTPUT CURRENT (A)
10
1.0
10
OUTPUT NOISE (µV/√Hz)
GROUND CURRENT (µA)
VIN = 2.5V to 5.5V
0.8
Output Noise
vs. Frequency
VIN = 2.5V
0.8
0.6
OUTPUT CURRENT (A)
400
1.0
LINE REGULATION (%)
1.010
400
VIN = 2.5V
DROPOUT VOLTAGE (mV)
DROPOUT VOLTAGE (mV)
400
RIPPLE REJECTION (dB)
Adjust Pin Voltage
vs. Output Current
Dropout Voltage
vs. Output Current
Dropout Voltage
vs. Output Current
-30
-40
-50
-60
-10
IOUT = 1A
CIN = 1uF
COUT = 10uF
-40
-50
-60
-70
-80
0.01
1
10
December 2012
100
1000
VRIPPLE= 80mV
-30
-80
0.01
FREQUENCY (kHz)
VOUT = 2.2V
-20
-70
0.1
Gain (dB)
VIN = 2.8V
0.1
1
10
100
1000
FREQUENCY (kHz)
8
M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Typical Characteristics (Continued)
Power Dissipation
vs. Output Current
Power Dissipation
vs. Output Current
100
VIN = 3.3V
VOUT = 2.5V
0.8
0.5
0.3
CASE TEMPERATURE (°C)
1.0
POWER DISSIPATION (W)
POWER DISSIPATION (W)
1.0
Case Temperature* (YM)
vs. Output Current
VIN = 2.5V
VOUT = 1.8V
0.8
0.5
0.3
0.0
0.0
0.0
0.2
0.4
0.6
0.8
1.0
OUTPUT CURRENT (A)
VIN = 3.3V
VOUT = 2.5V
80
60
40
20
0
0.0
0.2
0.4
0.6
0.8
OUTPUT CURRENT (A)
1.0
0.0
0.2
0.4
0.6
0.8
1.0
OUTPUT CURRENT (A)
Case Temperature* (YS)
vs. Output Current
CASE TEMPERATURE (°C)
100
VIN = 2.5V
VOUT = 1.8V
80
60
40
20
0
0.0
0.2
0.4
0.6
0.8
1.0
OUTPUT CURRENT (A)
Case Temperature*: The temperature measurement was taken at the hottest point on the MIC371xx that was case mounted on a 2.25 square inch PCB
at an ambient temperature of 25°C; see “Thermal Measurement” section. Actual results will depend upon the size of the PCB, ambient temperature and
proximity to other heat-emitting components.
December 2012
9
M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Functional Characteristics
December 2012
10
M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Functional Characteristics (Continued)
December 2012
11
M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Functional Characteristics (Continued)
December 2012
12
M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Functional Diagrams
MIC37110 Functional Diagram − Fixed Voltage
MIC37112 Functional Diagram − Adjustable Voltage
December 2012
13
M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Input Capacitor
An input capacitor of 1µF or greater is recommended
when the device is more than four 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. Place the external capacitors for the input/output
as close to the IC as possible. See Figure 1.
Application Information
The MIC37110/2 and MIC37120/2 are high-performance,
low-noise, low-voltage regulators suitable for moderate
current consumer applications such as mobile phones,
set-top boxes, and gaming consoles. The MIC37110/2
and MIC37120/2 are capable of sourcing 1A output, offer
high PSRR and low output noise. With a 400mV dropout
voltage at full load and over temperature, these ICs are
especially valuable in battery-powered systems and as
high-efficiency noise filters in post-regulator applications.
The MIC37110/12 and MIC37120/22 regulators are 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.
Enable Input
The TMLF-6 (Thin MLF) and SOIC-8 package options
feature an active-high enable input (EN) that allows for
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.
Transient Response and 3.3V to 2.5V or 2.5V to 1.8V,
1.65V or 1.5V Conversion
The MIC37110/02 and MIC37120/22 have 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 (ceramic) is all that is required. Larger values
help to improve performance even further.
Figure 1. Capacitor Requirements
Output Capacitor
The MIC37110/2 and MIC37120/2 requires an output
capacitor to maintain stability and improve transient
response. The MIC37110/2 and MIC37120/2 require a
2.2µF or greater output capacitor to maintain stability.
Larger capacitor values may be used but the device is
optimized for 2.2µF and optimum performance is
achieved with the use of low ESR ceramic capacitors.
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 a X7R ceramic capacitor to
ensure the same minimum capacitance over the
equivalent operating temperature range.
December 2012
14
M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Minimum Load Current
The MIC37112/22 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
VOUT
R1
R2
1.0V
0
−
1.1V
10.0Ω
100Ω
1.2V
20.0Ω
100Ω
1.5V
49.9Ω
100Ω
1.8V
80.6Ω
100Ω
2.2V
121Ω
100Ω
2.5V
150Ω
100Ω
3.0V
200Ω
100Ω
3.3V
232Ω
100Ω
3.6V
261Ω
100Ω
Table 1. Resistor Selection for Specific VOUT
Thermal Measurements
It is always wise the measure the IC’s case temperature
to make sure that it is within its operating limits. Although
this might seem like a very elementary task, it is very
easy to get to get erroneous results. The most common
mistake is to use the standard thermal couple that
comes with the thermal voltage meter. This thermal
couple wire gauge is large, typically 22 gauge, and
behaves like a heatsink, resulting in a lower case
measurement.
There are two suggested methods for measuring the IC
case temperature: a thermal couple or an infrared
thermometer. If a thermal couple is used, it must be
constructed of 36 gauge wire or higher to minimize the
wire heatsinking effect. In addition, the thermal couple tip
must be covered in either thermal grease or thermal glue
to make sure that the thermal couple junction is making
good contact to the case of the IC. This thermal couple
from Omega (5SC-TT-K-36-36) is adequate for most
applications.
To avoid this messy thermal couple grease or glue, an
infrared thermometer is recommended. Most infrared
thermometers’ spot size is too large for an accurate
reading on small form factor ICs. However, an IR
thermometer from Optris has a 1mm spot size, which
makes it ideal for the MIC371xx 2mm x 2mm Thin MLF
package. Also, get the optional stand. The stand makes
it easy to hold the beam on the IC for long periods of
time.
Figure 2. Adjustable Regulator with Resistors
The MIC37112 and MIC37122 allow programming the
output voltage anywhere between 1.0V and 5.0V by
placing a resistor divider network from OUT to GND and
is determined by the following equation:
 R1 
VOUT = VADJ × 
+ 1
 R2 
where:
VOUT is the desired output voltage and VADJ = 1.0V.
Two resistors are used. Resistors can be quite large, but
the resistor (R1) value between the OUT pin and the
ADJ pin should not exceed 10kΩ. Larger values can
cause instability.
The resistor values are calculated from the previous
equation, resulting in the following:
R1 = R2 × (VOUT − 1)
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 Table 1 for a list of resistor combinations to set the
output voltage. A 1% tolerance is recommended for both
R1 and R2.
December 2012
Power SOIC-8 Thermal Characteristics
One of the secrets of the MIC37110/37120’s
performance is its power SO-8 package featuring half
the thermal resistance of a standard SO-8 package.
Lower thermal resistance means more output current or
higher input voltage for a given package size.
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MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
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, θJC
(junction-to-case thermal resistance) and θCA (case-toambient 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-sink thermal resistance) and θSA
(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 heat sink must be used.
Figure 4. Copper Area vs. Power SO-8 Power Dissipation
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:
Figure 3. Thermal Resistance
ΔT = TJ(max) – TA(max)
TJ(max) = 125°C
TA(max) = maximum ambient operating
temperature.
Using the power SOIC-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
SOIC-8 has a θJC of 20°C/W, this is significantly lower
than the standard SOIC-8 which is typically 75°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 sinks to
ambient thermal resistance.
For example, the maximum ambient temperature is
50°C, the ΔT is determined as follows:
ΔT = 125°C – 50°C
ΔT = 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
December 2012
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MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
The θJA of this package is ideally 63°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 1A, then our power dissipation is as
follows:
PD = (3.3V – 2.5V) × 1A + 3.3V × 11mA
PD = 800mW + 36mW
PD = 836mW
From Figure 4, the minimum amount of copper required
2
to operate this application at a ΔT of 75°C is 160mm .
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, 836mW, the
curve in Figure 5 shows that the required area of copper
2
is 160mm .
December 2012
Figure 5. Copper Area vs. Power-SOIC Power Dissipation
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MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Package Information
SOT-223 (S)
December 2012
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M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Package Information (Continued)
6-Pin 2mm × 2mm Thin MLF (MT)
December 2012
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M9999-121312-A
MIC37110/MIC37112
MIC37120/MIC37122
Micrel, Inc.
Package Information (Continued)
8-Pin SOIC (M)
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
Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This
information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,
specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual
property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability
whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right.
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.
© 2012 Micrel, Incorporated.
December 2012
20
M9999-121312-A