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MIC37252
Micrel
MIC37252
2.5A, Low Voltage Cap LDO Regulator Final
General Description
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 -40C to 125C. For higher currents see the MIC3730x family of LDOs.
Features
* * * * * * * * * * * * * * * 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 LDO linear regulator for low-voltage digital IC PC add-in cards High efficiency linear power supplies SMPS post regulator Battery charger
Applications
Typical Application
MIC37252 VIN VOUT R1 VEN GND ADJ R2 COUT 47F, Ceramic
3.3V
1.8V
CIN
Adjustable Regulator
SuperSwitcher and Super eta 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
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MIC37252
MIC37252
Micrel
Ordering Information
Part Number MIC37252BR MIC37252BU Output Current 2.5A 2.5A Voltage* ADJ. ADJ. Junction Temp. Range -40C to +125C -40C to +125C Package S-Pak TO-263-5
*For other voltages contact Micrel.
Pin Configuration
5 4 3 2 1 ADJ VOUT GND VIN EN
TAB
S-PAK5 (R) TO-263 (U)
Pin Description
Pin Number 1 2 3 4 5 Pin Name EN VIN GND VOUT ADJ Pin Function Enable (Input): CMOS compatible input. Logic high = enable, logic low = shutdown Input voltage which supplies current to the output power device. Ground (TAB is connected to ground on S-Pak) Regulator Output Adjustable regulator feedback input. Connect to resistor voltage divider.
MIC37252
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MIC37252
Micrel
Absolute Maximum Rating (Note 1)
Supply Voltage (VIN) .................................................... 6.5V Enable Input Voltage (VEN) .......................................... 6.5V Power Dissipation .................................... Internally Limited Junction Temperature ........................ -40C TJ +125C Storage Temperature ......................... -65C TJ +150C Lead Temperature (soldering, 5 sec.) ....................... 260C ESD, Note 3
Operating Maximum Rating (Note 2)
Supply Voltage (VIN) ....................................... 3.0V to 6.0V Enable Input Voltage (VEN) ................................ 0V to 6.0V Junction Temperature Range ............. -40C TJ +125C Maximum Power Dissipation ................. ............... Note 4 Package Thermal Resistance S-Pak (JC) ........................................................ 2C/W TO-263-5 (JC) .................................................. 2C/W
Electrical Characteristics
TA = 25C with VIN = VOUT + 1V; VEN = VIN; IL = 10mA; bold values indicate -40C < TJ < +125C; unless otherwise noted. Parameter Output Voltage Accuracy Condition IL = 10mA 10mA < IOUT < IL(max), VOUT + 1 VIN 6V Output Voltage Line Regulation Output Voltage Load Regulation VIN - VOUT; Dropout Voltage ; Note 5 Ground Pin Current, Note 6 Ground Pin Current in Shutdown Current Limit Start-up Time Enable Input Enable Input Threshold Regulator enable Regulator shutdown Enable Pin Input Current VIL < 0.8V (Regulator shutdown) VIH > 2.25V (Regulator enabled) Reference Voltage Adjust Pin Bias Current
Note 1. Note 2. Note 3. Note 4. Note 5. Note 6. Exceeding the absolute maximum ratings may damage the device. The device is not guaranteed to function outside its operating rating. Device is ESD sensitive. Handling precautions recommended. PD(MAX) = (TJ(MAX) - TA) / JA, where JA, depends upon the printed circuit layout. See "Applications Information." 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. IGND is the quiescent current. IIN = IGND + IOUT.
Min -2 -3
Typ
Max +2 +3
Units % % % % mV mV mA A A s
VIN = VOUT +1.0V to 6.0V, IL = 10mA IL = 10mA to 2.5A IL = 1.5A IL = 2.5A IL = 2.5A VIL < 0.5V, VIN = VOUT + 1V VOUT = 0; VIN = 3.3V VEN = VIN, IOUT = 10mA, COUT = 47F 2.25
0.02 0.2 400 550 40 1.0 3 150
0.5 1 500 1000 60
250
V 0.8 2 4 V A A A V V nA nA
1 1.215 1.202
10 1.240 40
30 1.265 1.277 80 120
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MIC37252
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Typical Characteristics
PSRR
70 60 50 PRSS (dB) 40 30 20 COUT = 100F Ceramic V = 3.3V 10 IN V = 1.8V OUT 0 1 10 100 1k 10k 100k 1M FREQUENCY (Hz)
100mA 1A
PSRR
70 60
1A
600 DROPOUT VOLTAGE (mV)
100mA
Dropout Voltage
VOUT = 3.3V
500 400 300 200 100 0 0 0.5 1 1.5 2 OUTPUT CURRENT (A) 2.5
PSRR (dB)
2.5A
50 40 30
2.5A
20 C = 47F OUT 10 0 1 VIN = 3.3V VOUT = 1.8V 10 100 1k 10k 100k 1M FREQUENCY (Hz)
Dropout vs. Temperature
600 DROPOUT VOLTAGE (mV) 500 400 300 200 100 3.3VOUT 2.5A load OUTPUT VOLTAGE (V)
1.85 1.84 1.83 1.82 1.81 1.80 1.79 1.78 1.77
Output Voltage vs. Temperature
18 ENABLE CURRENT (A) 16 14 12 10 8 6 4 2
Enable Pin Current vs. Temperature
100mA Load
0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
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)
Short Circuit Current vs. Temperature
SHORT CIRCUIT CURRENT (A) 4 GROUND CURRENT (mA) 3.5 3 2.5 2 1.5 1 0.5 VOUT = 0V VIN = 4.3V 50 45 40 35 30 25 20 15 10 5 0 0
Ground Current vs. Supply Voltage
50 GROUND CURRENT (mA) 45 40 35 30 25 20 15 10
Ground Current vs. Temperature
2.5A Load
2.5A
1.5A 0.5A 1 2 3 4 SUPPLY VOLTAGE (V)
1A Load
0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE TJ (C)
5
5 10mA Load 0 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
Ground Current vs. Output Current
GROUND CURRENT (mA) 50 45 OUTPUT VOLTAGE (V) 40 35 30 25 20 15 10 5 0 0 0.5 1 1.5 2 OUTPUT CURRENT (A) 2.5 2.510 2.508 2.506 2.504 2.502 2.500 2.498 2.496
Output Voltage vs. Load Current
2.0 OUTPUT VOLTAGE (V) 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0
Dropout Characteristics
0.5A
1.5A
2.494 2.492 2.5V OUT 2.490 0 0.5 1 1.5 2 OUTPUT CURRENT (A)
2.5A
2.5
1 2 3 SUPPLY VOLTAGE (V)
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Functional Characteristics
Load Transient Response OUTPUT VOLTAGE (100mV/div.) VIN = 3.3V VOUT = 1.8V COUT = 47F OUTPUT VOLTAGE (200mV/div.) VIN = 3.3V VOUT = 1.8V COUT = 47F
Load Transient Response
OUTPUT CURRENT (1A/div.)
2.5A
2A OUTPUT CURRENT (1A/div.)
10mA
10mA
TIME (400s/div.)
TIME (400s/div.)
MIC37252 Start Up
INPUT VOLTAGE (1V/div.)
Line Transient Response
Load = 2A OUTPUT VOLTAGE (20mV/div.)
5V 3.3V
OUTPUT VOLTAGE (1V/div.)
TIME (100s/div.)
INPUT VOLTAGE (2V/div.)
TIME (100s/div.)
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MIC37252
MIC37252
Micrel
Output Capacitor The MIC37252 requires an output capacitor for stable operation. As a Cap LDO, the MIC37252 can operate with ceramic output capacitors as long as the amount of capacitance is 47F or greater. For values of output capacitance lower than 47F, the recommended ESR range is 200m to 2. The minimum value of output capacitance recommended for the MIC37252 is 10F. For 47F or greater the ESR range recommended is less than 1. Ultra-low ESR, ceramic capacitors are recommended for output capacitance of 47F 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 47F output capacitor is all that is required. Larger values help to improve performance even further. Input Capacitor An input capacitor of 1.0F 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 10F 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 eta 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: SA = ((TJ(MAX) - TA)/ PD) - (JC + CS) Where TJ(MAX) < 125oC and CS 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 eta 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 1.0F 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
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MIC37252
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 15A. Adjustable Regulator Design
MIC37252 OUT R1
ENABLE SHUTDOWN
Micrel
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 10k 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).
VIN
IN
VOUT COUT
EN
ADJ GND
R2
R1 VOUT = 1.240V 1 + R2
Figure 2. Adjustable Regulator with Resistors
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MIC37252
MIC37252
Micrel
Package Information
0.3700.005 9.3950.125 0.3550.005 9.0150.125 0.256 6.50 0.0750.005 1.9050.125 0.010 0.250
0.0400.010 1.0150.255
0.3150.005 8.0000.130
0.0400.005 1.0150.125 0.4150.005 10.540.130 0.0030.002 0.0800.050
INCHES MILLIMETER
0.067 1.700
0.0280.003 0.7100.080
0.010 0.250
0.0360.005 0.9150.125 0 min 6 max
5-Lead S-PAK (R)
0.4050.005 0.065 0.010 202 0.0500.005
0.176 0.005 0.060 0.005
0.3600.005 0.6000.025 SEATING PLANE 0.004 +0.004 -0.008
0.0670.005 DIM. = INCH
0.032 0.003
8 MAX 0.015 0.002
0.100 0.01
5-Lead TO-263 (U)
MICREL, INC. 1849 FORTUNE DRIVE
TEL
SAN JOSE, CA 95131
WEB
USA
+ 1 (408) 944-0800
FAX
+ 1 (408) 944-0970
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. (c) 2002 Micrel, Incorporated
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