MIC37252 DATA SHEET (11/09/2015) DOWNLOAD

MIC37252
2.5A, Low Voltage µCap LDO Regulator
General Description
Features
The Micrel MIC37252 is a 2.5A low-dropout linear voltage
regulator that provides a low voltage, high current output
with a minimum of external components. It offers high
precision, low dropout and low ground current.
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•
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The MIC37252 operates from an input voltage of 3.0V
to6.0V. It is designed to drive digital circuits requiring low
voltage at high currents (i.e., PLDs, DSP, microcontroller,
etc.). It is available in an adjustable output voltage capable
of 1.24V to 5.5V.
Features of the MIC37252 LDO include thermal and
current limit protection, and reverse current and reverse
battery protection.
Junction temperature range of the MIC37252 is from
–40°C to +125°C.
For higher currents see the MIC3730x family of LDOs.
2.5A minimum guaranteed output current
Ideal for 3.3V to 1.8V conversion
Stable with ceramic or tantalum capacitor
±2.0% initial output tolerance
Dropout voltage = 550mV @ 2.5A
Excellent line and load regulation specifications
Logic controlled shutdown
Thermal shutdown and current limit protection
Reverse-leakage protection
S-Pak and TO-263 packages
Applications
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LDO linear regulator for low-voltage digital IC
PC add-in cards
High efficiency linear power supplies
SMPS post regulator
Battery charger
____________________________________________________________________________________________________________
Typical Application
Adjustable Regulator
SuperSwitcher and Super ßeta PNP are trademarks 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
February 2006
M9999-021606
(408) 955-1690
Micrel, Inc.
MIC37252
Ordering Information
Part Number
Output
Current
Voltage*
Junction
Temperature Range
Package
Standard
RoHS Compliant**
MIC37252BR
MIC37252WR
2.5A
Adj.
–40° to +125°C
S-Pak-5
MIC37252BU
MIC37252WU
2.5A
Adj.
–40° to +125°C
TO-263-5
*For other voltages, please contact Micrel Marketing.
**RoHS compliant with “high melting solder” exemption.
Pin Configuration
S-PAK5 (R)
TO-263 (U)
Pin Description
Pin Number
Pin Name
1
EN
Enable (Input): CMOS compatible input. Logic high = enable, logic low =
shutdown.
2
VIN
Input voltage which supplies current to the output power device.
3
GND
Ground (TAB is connected to ground on S-Pak).
4
VOUT
5
ADJ
February 2006
Pin Function
Regulator Output.
Adjustable regulator feedback input. Connect to resistor voltage divider.
2
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Micrel, Inc.
MIC37252
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VIN) ......................................................6.5V
Enable Input Voltage (VEN)............................................6.5V
Power Dissipation .....................................Internally Limited
Junction Temperature .........................–40°C ≤ TJ ≤ +125°C
Storage Temperature ..........................–65°C ≤ TJ ≤ +150°C
Lead Temperature (soldering, 5sec.)......................... 260°C
EDS(3)
Supply voltage (VIN) ......................................... 3.0V to 6.0V
Enable Input Voltage (VEN).................................. 0V to 6.0V
Junction Temperature Range .............–40°C ≤ TJ ≤ +125°C
Maximum Power Dissipation(4)
Package Thermal Resistance
S-Pak (θJC) ..........................................................2°C/W
TO-263-5 (θJC).....................................................2°C/W
Electrical Characteristics(5)
TA = 25°C with VIN = VOUT + 1V; VEN = VIN; IL = 10mA, bold values indicate –40°C< TJ < +125°C, unless otherwise noted.
Parameter
Condition
Min
Output Voltage Accuracy
IL = 10mA
10mA < IOUT < IL(max), VOUT + 1 ≤ VIN ≤ 6V
Typ
Max
Units
-2
+2
%
-3
+3
%
Output Voltage Line Regulation
VIN = VOUT + 1.0V to 6.0V, IL = 10mA
0.02
0.5
%
Output Voltage Load Regulation
IL = 10mA to 2.5A
0.2
1
%
VIN – VOUT; Dropout Voltage,
Note 6
IL = 1.5A
400
500
mV
IL = 2.5A
550
1000
mV
Ground Pin Current, Note 7
IL = 2.5A
40
60
mA
Ground Pin Current in Shutdown
VIL ≤ 0.5V, VIN = VOUT + 1V
1.0
µA
Current Limit
VOUT = 0; VIN = 3.3V
3
A
Start-up Time
VEN = VIN, IOUT = 10mA, COUT = 47µF
150
250
µs
Enable Input
Enable Input Threshold
Regulator enable
Enable Pin Input Current
VIL ≤ 0.8V (Regulator shutdown)
V
2.25
Regulator shutdown
VIH ≥ 2.25V (Regulator enable)
Reference Voltage
0.8
V
2
4
µA
µA
1
10
30
µA
1.215
1.202
1.240
1.265
1.277
V
V
40
80
120
nA
nA
Adjust Pin Bias Current
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. Device is ESD sensitive. Handling precautions recommended.
4. PD(max) = TJ(max) – TA) / θJA, where θJA, depends upon the printed circuit layout. See “Applications Information.”
5. Specification for packaged product only
6. VDO = VIN – VOUT when VOUT decreased to 98% of its nominal output voltage with VIN = VOUT + 1V. For output voltages below 2V, dropout voltage
specification does not apply due to a minimum input operating voltage of 3V
7. IGND is the quiescent current. IIN = IGND + IOUT.
February 2006
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MIC37252
Typical Characteristics
100mA
60
1A
50
2.5A
40
30
20 COUT = 100µF Ceramic
V = 3.3V
10 IN
VOUT = 1.8V
0
1 10 100 1k 10k 100k 1M
FREQUENCY (Hz)
200
100
3.3VOUT
2.5A load
GROUND CURRENT (mA)
3.5
3
2.5
2
1.5
1
0.5
VOUT = 0V
VIN = 4.3V
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE TJ (°C)
50
45
40
35
30
25
20
15
10
5
0
1.85
1.84
1.83
1.82
1.81
1.80
1.79
1.78
1.77
1.76
1.75
-40 -20 0 20 40 60 80 100 120
TEMPERATURE °C)
(
Short Circuit Current
vs. Temperature
Ground Current
vs. Output Current
0
February 2006
0.5
1
1.5
2
2.5
OUTPUT CURRENT (A)
200
100
0
50
45
40
35
30
25
20
15
10
5
0
0
Enable Pin Current
vs. Temperature
100mA Load
14
12
10
8
6
4
2
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE °C)
(
Ground Current
vs. Temperature
2.5A
1.5A
5
2.510
2.508
2.506
2.504
2.502
2.500
2.498
2.496
2.494
2.492 2.5V
OUT
2.490
0
0.5
1
1.5
2
2.5
OUTPUT CURRENT (A)
4
0.5
1
1.5
2
2.5
OUTPUT CURRENT (A)
16
Ground Current
vs. Supply Voltage
0.5A
1
2
3
4
SUPPLY VOLTAGE (V)
0
18
Output Voltage
vs. Load Current
OUTPUT VOLTAGE (V)
GROUND CURRENT (mA)
SHORT CIRCUIT CURRENT (A)
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE °C)
(
4
300
ENABLE CURRENT (µA)
300
30
Dropout Voltage
VOUT = 3.3V
400
GROUND CURRENT (mA)
400
2.5A
40
500
Output Voltage
vs. Temperature
OUTPUT VOLTAGE (V)
DROPOUT VOLTAGE (mV)
500
1A
20 COUT = 47µF
V = 3.3V
10 IN
VOUT = 1.8V
0
1 10 100 1k 10k 100k 1M
FREQUENCY (Hz)
Dropout
vs. Temperature
600
600
100mA
OUTPUT VOLTAGE (V)
PRSS (dB)
50
PSRR (dB)
60
PSRR
70
DROPOUT VOLTAGE (mV)
PSRR
70
50
2.5A Load
45
40
35
30
25
20
15 1A Load
10
5 10mA Load
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE °C)
(
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.00
Dropout Characteristics
0.5A
1.5A
2.5A
1
2
3
SUPPLY VOLTAGE (V)
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Micrel, Inc.
MIC37252
Functional Characteristics
LoadTransient Response
OUTPUT VOLTAGE
(200mV/div.)
VIN = 3.3V
VOUT = 1.8V
COUT = 47µF
2A
OUTPUT CURRENT
(1A/div.)
VIN = 3.3V
VOUT = 1.8V
COUT = 47µF
OUTPUT CURRENT
(1A/div.)
OUTPUT VOLTAGE
(100mV/div.)
LoadTransient Response
10mA
TIME (400µs/div.)
2.5A
10mA
TIME (400µs/div.)
OUTPUT VOLTAGE
(20mV/div.)
Line Transient Response
5V
INPUT VOLTAGE
(2V/div.)
3.3V
TIME (100µs/div.)
February 2006
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MIC37252
applications where the minimum input voltage is known
and is large compared with the dropout voltage. Use a
series input resistor to drop excessive voltage and
distribute the heat between this resistor and the
regulator. The low dropout properties of Micrel Super
βeta PNP® regulators allow significant reductions in
regulator power dissipation and the associated heat sink
without compromising performance. When this technique
is employed, a capacitor of at least 1.0µF is needed
directly between the input and regulator ground. Refer to
Application Note 9 for further details and examples on
thermal design and heat sink applications.
Application Information
The MIC37252 is a high-performance low-dropout
voltage regulator suitable for moderate to high-current
regulator applications. Its 550mV dropout voltage at full
load makes it especially valuable in battery-powered
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-toemitter saturation voltage, dropout performance of the
PNP output of these devices is limited only by the low
VCE saturation voltage.
Output Capacitor
The MIC37252 requires an output capacitor for stable
operation. As a µCap LDO, the MIC37252 can operate
with ceramic output capacitors as long as the amount of
capacitance is 47µF or greater. For values of output
capacitance lower than 47µF, the recommended ESR
range is 200mΩ to 2Ω. The minimum value of output
capacitance recommended for theMIC37252 is 10µF.
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% to 5% of the
load current.
The MIC37252 regulator is fully protected from damage
due to fault conditions. Current limiting is provided. This
limiting is linear; output current during overload
conditions is constant. Thermal shutdown disables the
device when the die temperature exceeds the maximum
safe operating temperature. Transient protection allows
device (and load) survival even when the input voltage
spikes above and below nominal. The output structure of
these regulators allows voltages in excess of the desired
output voltage to be applied without reverse current flow.
For 47µF or greater the ESR range recommended is
less than1Ω. Ultra-low ESR, ceramic capacitors are
recommended for output capacitance of 47µF 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 withY5V dielectric, the value must be
much higher than an X7Rceramic capacitor to ensure
the same minimum capacitance over the equivalent
operating temperature range. The MIC37252 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 47µF
output capacitor is all that is required. Larger values help
to improve performance even further.
Thermal Design
Linear regulators are simple to use. The most
complicated design parameters to consider are thermal
characteristics. Thermal design requires the following
application-specific parameters:
•
Maximum ambient temperature (TA)
•
Output current (IOUT)
•
Output voltage (VOUT)
•
Input voltage (VIN)
•
Ground current (IGND)
First, calculate the power dissipation of the regulator
from these numbers and the device parameters from this
datasheet.
PD = (VIN – VOUT) IOUT + VIN IGND
Input Capacitor
An input capacitor of 1.0µF or greater is recommended
when the device is more than 4 inches away from the
bulk supply capacitance, or when the supply is a battery.
Small, surface-mount chip capacitors can be used for
the bypassing. The capacitor should be place within 1” of
the device for optimal performance. Larger values will
help to improve ripple rejection by bypassing the input to
the regulator, further improving the integrity of the output
voltage.
Where the ground current is approximated by using
numbers from the “Electrical Characteristics” or “Typical
Characteristics.” Then the heat sink thermal resistance is
determined with this formula:
θSA = ((TJ(MAX) – TA)/ PD) – (θJC + θCS)
Where T J(MAX) ≤ 125°C and θCS is between 0°C and
2°C/W. The heat sink may be significantly reduced in
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MIC37252
input is TTL/CMOS compatible for simple logic interface,
but can be connected to up to VIN. When enabled, it
draws approximately 15µA.
Transient Response and 5V to 3.3V or 3.3V to
1.8VConversions
The MIC37252 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, preferably tantalum,
is all that is required. Larger values help to improve
performance even further.
Adjustable Regulator Design
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 1.8V, the NPNbased regulators are already operating in dropout, with
typical dropout requirements of 2V or greater. To convert
down to1.8V without operating in dropout, NPN-based
regulators require an input voltage of 3.8V at the very
least. The MIC37252 regulator will provide excellent
performance with an input as low as 3.0V. This gives the
PNP-based regulators a distinct advantage over older
NPN-based linear regulators.
Figure 2. Adjustable Regulator with Resistors
The MIC37252 allows programming of the output voltage
anywhere between 1.24V and the 5.5V maximum
operating rating of the family. Two resistors are used.
Resistors values are recommended to be less than 10kΩ
in value to improve stability. The resistor values can be
sized to draw the mini-mum load current for this device.
The resistor values are calculated by:
⎞
⎛V
R1 = R2⎜⎜ OUT − 1⎟⎟
⎠
⎝ 1.240
Minimum Load Current
The MIC37252 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 operation.
Where VOUT 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).
Enable Input
The MIC37252 also features an enable input for on/off
control of the device. Its shutdown state draws “zero”
current (only microamperes of leakage). The enable
February 2006
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(408) 955-1690
Micrel, Inc.
MIC37252
Package Information
5-Pin S-PAK (R)
θ4
θ1
θ2
θ1
θ1
θ2
θ3
θ4
θ1
θ3
5-Pin TO-263 (U)
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.
February 2006
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