MICREL MIC37252

MIC37252
Micrel
MIC37252
2.5A, Low Voltage µCap LDO Regulator
Final
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.
The MIC37252 operates from an input voltage of 3.0V to
6.0V. 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
•
•
•
•
•
LDO linear regulator for low-voltage digital IC
PC add-in cards
High efficiency linear power supplies
SMPS post regulator
Battery charger
Typical Application
3.3V
MIC37252
VIN
VOUT
1.8V
R1
CIN
VEN
COUT
47µF, Ceramic
ADJ
R2
GND
Adjustable Regulator
SuperSwitcher and Super βeta PNP are trademarks 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
January 2003
1
MIC37252
MIC37252
Micrel
Ordering Information
Part Number
Output
Current
Voltage*
Junction Temp. Range
Package
MIC37252BR
2.5A
ADJ.
–40°C to +125°C
S-Pak
MIC37252BU
2.5A
ADJ.
–40°C to +125°C
TO-263-5
*For other voltages contact Micrel.
Pin Configuration
TAB
5
4
3
2
1
ADJ
VOUT
GND
VIN
EN
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
Regulator Output
5
ADJ
MIC37252
Pin Function
Adjustable regulator feedback input. Connect to resistor voltage divider.
2
January 2003
MIC37252
Micrel
Absolute Maximum Rating (Note 1)
Operating Maximum Rating (Note 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, 5 sec.) ....................... 260°C
ESD, Note 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 …………….. ............... Note 4
Package Thermal Resistance
S-Pak (θJC) ........................................................ 2°C/W
TO-263-5 (θJC) .................................................. 2°C/W
Electrical Characteristics
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 ;
IL = 1.5A
400
500
mV
Note 5
IL = 2.5A
550
1000
mV
Ground Pin Current, Note 6
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
2.25
V
Regulator shutdown
Enable Pin Input Current
VIL < 0.8V (Regulator shutdown)
VIH > 2.25V (Regulator enabled)
Reference Voltage
Exceeding the absolute maximum ratings may damage the device.
Note 2.
The device is not guaranteed to function outside its operating rating.
Note 3.
Device is ESD sensitive. Handling precautions recommended.
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
Note 1.
0.8
Note 4.
PD(MAX) = (TJ(MAX) – TA) / θJA, where θJA, depends upon the printed circuit layout. See “Applications Information.”
Note 5.
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.
Note 6.
IGND is the quiescent current. IIN = IGND + IOUT.
January 2003
3
MIC37252
MIC37252
Micrel
Typical Characteristics
PSRR
PSRR
100mA
60
1A
1A
50
2.5A
PSRR (dB)
PRSS (dB)
50
40
30
20 COUT = 100µF Ceramic
V = 3.3V
10 IN
V
= 1.8V
OUT
0
1
10 100 1k 10k 100k 1M
FREQUENCY (Hz)
10
0
1
600
500
1.84
1.83
OUTPUT VOLTAGE (V)
300
200
3.3VOUT
2.5A load
500
400
300
200
100
0
100 1k 10k 100k 1M
FREQUENCY (Hz)
0
Output Voltage
vs. Temperature
1.80
1.79
1.78
1.77
14
12
10
8
6
4
2
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
Ground Current
vs. Temperature
50
45
40
45
40
2
1.5
1
0.5
VOUT = 0V
VIN = 4.3V
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE TJ (°C)
GROUND CURRENT (mA)
50
GROUND CURRENT (mA)
4
2.5A
35
30
25
20
15
10
5
0
0
Ground Current
vs. Output Current
1.5A
0.5A
1
2
3
4
SUPPLY VOLTAGE (V)
5
OUTPUT VOLTAGE (V)
30
25
20
15
10
5
0
0
MIC37252
0.5
1
1.5
2
OUTPUT CURRENT (A)
25
20
15
10
2.5
1A Load
5 10mA Load
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
Dropout Characteristics
2.510
2.508
40
35
2.5A Load
35
30
Output Voltage
vs. Load Current
50
45
100mA Load
16
3.5
3
2.5
18
Ground Current
vs. Supply Voltage
2.5
0.5
1
1.5
2
OUTPUT CURRENT (A)
Enable Pin Current
vs. Temperature
1.82
1.81
Short Circuit Current
vs. Temperature
SHORT CIRCUIT CURRENT (A)
10
1.76
1.75
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
GROUND CURRENT (mA)
VIN = 3.3V
VOUT = 1.8V
VOUT = 3.3V
2.0
OUTPUT VOLTAGE (V)
DROPOUT VOLTAGE (mV)
30
1.85
400
2.5A
40
20 C
= 47µF
OUT
Dropout
vs. Temperature
100
100mA
DROPOUT VOLTAGE (mV)
60
Dropout Voltage
600
70
ENABLE CURRENT (µA)
70
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
OUTPUT CURRENT (A)
4
2.5
1.8
1.6
1.4
1.2
0.5A
1.5A
1.0
0.8
0.6
0.4
0.2
0.0
0
2.5A
1
2
3
SUPPLY VOLTAGE (V)
4
January 2003
MIC37252
Micrel
Functional Characteristics
Load Transient Response
OUTPUT VOLTAGE
(200mV/div.)
VIN = 3.3V
VOUT = 1.8V
COUT = 47µF
OUTPUT CURRENT
(1A/div.)
2A
10mA
2.5A
10mA
TIME (400µs/div.)
TIME (400µs/div.)
MIC37252 Start Up
Line Transient Response
OUTPUT VOLTAGE
(20mV/div.)
Load = 2A
TIME (100µs/div.)
January 2003
5V
3.3V
INPUT VOLTAGE
(2V/div.)
OUTPUT VOLTAGE
(1V/div.)
INPUT VOLTAGE
(1V/div.)
VIN = 3.3V
VOUT = 1.8V
COUT = 47µF
OUTPUT CURRENT
(1A/div.)
OUTPUT VOLTAGE
(100mV/div.)
Load Transient Response
TIME (100µs/div.)
5
MIC37252
MIC37252
Micrel
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 the
MIC37252 is 10µF.
For 47µF or greater the ESR range recommended is less than
1Ω. 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 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. 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.
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, surfacemount 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.
Transient Response and 5V to 3.3V or 3.3V to 1.8V
Conversions
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.
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 NPN-based
regulators are already operating in dropout, with typical
dropout requirements of 2V or greater. To convert down to
1.8V 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.
Applications 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 highefficiency 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 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 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.
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
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 TJ(MAX) < 125oC and θCS is between 0oC and 2oC/W.
The heat sink may be significantly reduced in 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.
MIC37252
6
January 2003
MIC37252
Micrel
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.
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 input is TTL/CMOS
compatible for simple logic interface, but can be connected to
up to VIN. When enabled, it draws approximately 15µA.
Adjustable Regulator Design
VIN
MIC37252
OUT
IN
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 minimum load current for this device. The resistor values are
calculated by:
V

R1 = R2  OUT − 1
 1.240 
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).
VOUT
R1
ENABLE
SHUTDOWN
EN
ADJ
GND
R2
COUT
 R1
VOUT = 1.240V 1 +

 R2 
Figure 2. Adjustable Regulator with Resistors
January 2003
7
MIC37252
MIC37252
Micrel
Package Information
0.370±0.005
9.395±0.125
0.355±0.005
9.015±0.125
0.040±0.010
1.015±0.255
0.075±0.005
1.905±0.125
0.256
6.50
0.010
0.250
0.040±0.005
1.015±0.125
0.315±0.005
8.000±0.130
0.415±0.005
10.54±0.130
0.067
1.700
INCHES
MILLIMETER
0.003±0.002
0.080±0.050
0.010
0.250
0.028±0.003
0.710±0.080
0.036±0.005
0.915±0.125
0° min
6° max
5-Lead S-PAK (R)
0.176 ±0.005
0.405±0.005
0.065 ±0.010
20°±2°
0.060 ±0.005
0.050±0.005
0.360±0.005
0.600±0.025
SEATING PLANE
0.004 +0.004
–0.008
8° MAX
0.032 ±0.003
0.067±0.005
0.100 ±0.01
0.015 ±0.002
DIM. = INCH
5-Lead TO-263 (U)
MICREL, INC. 1849 FORTUNE DRIVE
TEL
+ 1 (408) 944-0800
FAX
SAN JOSE, CA 95131
+ 1 (408) 944-0970
WEB
USA
http://www.micrel.com
This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or
other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel, Inc.
© 2002 Micrel, Incorporated
MIC37252
8
January 2003