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MIC35302
3A, Low Voltage Cap LDO Regulator
General Description
The MIC35302 is a 3A low-dropout linear voltage regulator that provides a low voltage, high current output with a minimum of external components. It offers high precision, ultra-low dropout (600mV over temperature), and low ground current. The MIC35302 operates from an input of 2.25V to 6.0V. It is designed to drive digital circuits requiring low voltage at high currents (i.e., PLDs, DSPs, micro-controllers, etc.), providing an adjustable output voltage from 1.24V to 5.4V. Features of the MIC35302 LDO include current limiting and thermal protection, and reverse current and reverse battery protection. Also logic (active-HIGH) enable pin is included. The MIC35302 is available in a 5-pin power D-Pak package (TO-252) with an operating temperature range of -40C to +125C. Data sheets and support documentation can be found on Micrel's web site at www.micrel.com.
Features
* 3A minimum guaranteed output current * 600mV maximum dropout voltage over temperature - Ideal for 3.0V to 2.5V conversion - Ideal for 2.5V to 1.8V, 1.65V, or 1.5V conversion * Stable with ceramic or tantalum capacitor * Wide input voltage range - VIN: 2.25V to 6.0V * 1.0% initial output tolerance * Excellent line and load regulation specifications * Logic controlled shutdown * Thermal shutdown and current limit protection * Reverse-leakage protection * -40C to +125C junction temperature * Power D-Pak package (TO-252)
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**
Adjustable Regulator Application
(*See Minimum Load Current Section)
**See Thermal Design Section Super eta 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
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MIC35302
Ordering Information
Part Number MIC35302WD*
Note: * RoHS compliant with `high-melting solder' exemption.
Output Current 3A
Voltage Adjustable
Junction Temp. Range(1) -40 to +125C
Package 5-Pin TO-252
Pin Configuration
5-Pin TO-252 D-Pak (D)
Pin Description
Pin Number 1 2 3 4 Pin Name EN IN GND, TAB OUT Pin Function Enable (Input): CMOS compatible input. Logic high = enable, logic low = shutdown. Input Voltage: Supplies the current to the output power device Ground: TAB is also connected internally to the IC's ground on D-PAK. Regulator Output: The output voltage is set by the resistor divider connected from OUT to GND (with the divided connection tied to ADJ). A minimum value capacitor must be used to maintain stability. See Functional Description Information. Adjustable Regulator Feedback Input: Connect to the resistor voltage divider that is placed from OUT to GND in order to set the output voltage.
5
ADJ
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Absolute Maximum Ratings(1)
Supply Voltage (VIN) ..................................... -0.3V to +6.5V Enable Input Voltage (VEN)........................... -0.3V to +6.5V Power Dissipation .....................................Internally Limited Junction Temperature .........................-40C TJ +125C Storage Temperature (Ts) ...................-65C TJ +150C Lead Temperature (soldering, 5sec.)......................... 260C ESD Rating(3) .................................................................. 2kV
Operating Ratings(2)
Supply voltage (VIN) ................................... +2.25V 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 TO-252 (JC) ........................................................3C/W TO-252 (JA) ......................................................56C/W
Electrical Characteristics(5)
TJ = 25C with VIN = VEN = VOUT + 1V; IOUT = 10mA; bold values indicate -40C < TJ < +125C, unless otherwise noted.
Parameter Output Voltage Line Regulation Output Voltage Load Regulation Dropout Voltage, VIN - VOUT Note 6 Ground Pin Current, Note 7 Ground Pin Current in Shutdown Current Limit Start-up Time Enable Input Enable Input Threshold Enable Pin Input Current Adjust Pin Reference Voltage Reference Voltage Temp. Coefficient Adjust Pin Bias Current Adjust Pin Bias Current Temp. Coefficient
Notes: 1. 2. 3. 4. 5. 6. 7. 8. Exceeding the absolute maximum rating may damage the device. The device is not guaranteed to function outside its operating rating. Devices are ESD sensitive. Handling precautions recommended. 200V Machine Model PD(MAX) = (TJ(MAX) - TA) / JA, where JA, depends upon the printed circuit layout. See "Applications Information." Specification for packaged product only. VDO = VIN - VOUT when VOUT decreased to 98% of its nominal output voltage with VIN = VOUT +1V. For output voltages below 1.75V, dropout voltage specification does not apply due to a minimum input operating voltage of 2.25V. IGND is the quiescent current. IIN = IGND + IOUT. Thermal regulation is defined as the change in output voltage at a time t after a change in power dissipation is applied, excluding load or line regulation effects. Specifications are for a 200mA load pulse at VIN = 6V for t = 10ms.
Condition VIN = VOUT +1.0V to 6.0V IOUT = 10mA to 3A IOUT = 1.5A IOUT = 3A IOUT = 3A VIL 0.5V, VIN = VOUT + 1V VOUT = 0 VEN = VIN, IOUT = 10mA, COUT = 47F Regulator enable Regulator shutdown VIL 0.8V (regulator shutdown) VIH 2.25V (regulator enabled)
Min
Typ 0.02 0.2 250 370 20 1.0
Max 0.5 1 450 600 50 8.5 150
Units % % mV mV mA A A s V
3.5
6 35
2.25 0.8 4 1 1.228 1.215 15 1.240 20 40 0.1 80 120 75 1.252 1.265
V A A V V ppm/C nA nA nA/C
Note 8
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Typical Characteristics
80 70 60 PSRR (dB) 50 40 30 IOUT = 3A COUT = 47F 10 C = 0 IN 0 0.01 0.1 1 10 100 FREQUENCY (kHz) 20
Power Supply Rejection Ratio
VIN = 2.5V VOUT = 1.5V PSRR (dB)
80 70 60 50 40 30
Power Supply Rejection Ratio
VIN = 2.5V VOUT = 1.5V
1000
IOUT = 3A COUT = 100F 10 C = 0 IN 0 0.01 0.1 1 10 100 FREQUENCY (kHz) 20
1000
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Functional Characteristics
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MIC35302 regulator. The low dropout properties of Micrel Super eta PNP(R) 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. With no heat sink in the application, calculate the junction temperature to determine the maximum power dissipation that will be allowed before exceeding the maximum junction temperature of the MIC35302. The maximum power allowed can be calculated using the thermal resistance (JA) of the D-Pak adhering to the following criteria for the PCB design: 2 oz. copper and 100mm2 copper area for the MIC35302. As an example, given an expected maximum ambient temperature (TA) of 75C with VIN = 2.25V, VOUT = 1.75V, and IOUT = 2.5A, first calculate the expected PD using Equation (1); PD = (2.25V - 1.75V)2.5A + (2.25V)(0.027A) = 1.31W Next, calcualte the junction temperature for the expected power dissipation. TJ=(JAxPD)+TA=(56C/Wx1.31W)+75C=148.4C Now determine the maximum power dissipation allowed that would not exceed the IC's maximum junction temperature (125C) without the use of a heat sink by PD(MAX)=(TJ(MAX)-TA)/JA=(125C-75C)/(56C/W)=0.893W Output Capacitor The MIC35302 requires an output capacitor for stable operation. As a Cap LDO, the MIC35302 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 MIC35302 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.
Functional Description
The MIC35302 is a high-performance low-dropout voltage regulator suitable for moderate to high-current regulator applications. Its 600mV dropout voltage at full load and over-temperature makes it especially valuable in battery-powered systems and as high-efficiency noise filters in post-regulator applications. Unlike older NPNpass transistor designs, there the minimum dropout voltage is limited by the based-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(R) process reduces this drive requirement to only 2% to 5% of the load current. The MIC35302 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 (1) 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) (2) Where TJ(MAX) 125C and CS is between 0C and 2C/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 October 2009 6
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Micrel, Inc. Input Capacitor An input capacitor of 1.0F or greater is recommended when the device is more than 4 inches away from the bulk and 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. Transient Response and 3.3V to 2.5V, 2.5V to 1.8V or 1.65V, or 2.5V to 1.5V Conversions The MIC35302 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 tantalum 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, 2.5V to 1.8V or 1.65V, or 2.5V to 1.5V, the NPN-based regulators are already operating in dropout, with typical dropout requirements of 1.2V or greater. To convert down to 2.5V without operating in dropout, NPN-based regulators require an input voltage of 3.7V at the very least. The MIC35302 regulator will provide excellent performance with an input as low as 3.0V or 2.25V, respectively. This gives the PNP-based regulators a distinct advantage over older, NPN-based linear regulators. Minimum Load Current The MIC35302 regulator is specified between finite loads. If the output current is too small, leakage currents
MIC35302 dominate and the output voltage rises. A 10mA minimum load current is necessary for proper operation. Enable Input The MIC35302 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
Figure 1. Adjustable Regulator with Resistors
The MIC35302 allows programming the output voltage anywhere between 1.24V and 5.4V. Two resistors are used. The resistor values are calculated by:
V R1 = R2 x OUT - 1 1.240
Where VOUT is the desired output voltage. Figure 1 shows component definition. Applications with widely varying load currents may scale the resistors to draw the minimum load current required for proper operation (see Minimum Load Current section).
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Package Information
5-Pin TO-252-5 (D)
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. (c) 2009 Micrel, Incorporated.
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