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MIC3775
750mA Cap Low-Voltage Low-Dropout Regulator
General Description
The MIC3775 is a 750mA low-dropout linear voltage regulators that provides low-voltage, high-current output from an extremely small package. Utilizing Micrel's proprietary Supereta PNP(R) pass element, the MIC3775 offers extremely low-dropout (typically 280mV at 750mA) and low ground current (typically 7.5mA at 750mA). The MIC3775 is ideal for PC add-in cards that need to convert from standard 5V to 3.3V or 3.0V, 3.3V to 2.5V or 2.5V to 1.8Vor 1.65V. A guaranteed maximum dropout voltage of 500mV over all operating conditions allows the MIC3775 to provide 2.5V from a supply as low as 3.0V and 1.8V or 1.5V from a supply as low as 2.25V. The MIC3775 is fully protected with overcurrent limiting, thermal shutdown, and reversed-leakage protection. Fixed and adjustable output voltage options are available 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
* Fixed and adjustable output voltages to 1.24V * 280mV typical dropout at 750mA - Ideal for 3.0V to 2.5V conversion - Ideal for 2.5V to 1.8V or 1.65V conversion * Stable with ceramic capacitor * 750mA minimum guaranteed output current * 1% initial accuracy * Low ground current * Current limiting and thermal shutdown * Reversed-leakage protection * Fast transient response * Low-profile power MSOP-8 package
Applications
* * * * * * * * Fiber optic modules LDO linear regulator for PC add-in cards PowerPCTM power supplies High-efficiency linear power supplies SMPS post regulator Multimedia and PC processor supplies Battery chargers Low-voltage microcontrollers and digital logic
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Typical Application
1.25V/750mA Adjustable Regulator
PowerPC is a trademark of IBM Corp. 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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Ordering Information
Part Number Standard MIC3775-1.5BMM MIC3775-1.65BMM MIC3775-1.8BMM MIC3775-2.5BMM MIC3775-3.0BMM MIC3775-3.3BMM MIC3775BMM Pb-Free MIC3775-1.5YMM MIC3775-1.65YMM MIC3775-1.8YMM MIC3775-2.5YMM MIC3775-3.0YMM MIC3775-3.3YMM MIC3775YMM Voltage 1.5V 1.65V 1.8V 2.5V 3.0V 3.3V Adj. Junction Temp. Range -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C -40 to +125C Package 8-Pin MSOP 8-Pin MSOP 8-Pin MSOP 8-Pin MSOP 8-Pin MSOP 8-Pin MSOP 8-Pin MSOP
Note: For other voltages. Contact Micrel Marketing for details.
Pin Configuration
MIC3775-x.x (Fixed) 8-Pin MSOP (MM)
MIC3775 (Adjustable) 8-Pin MSOP (MM)
Pin Description
Pin Number 1 2 3 ADJ 4 5-8 OUT GND Pin Name EN IN FLG Pin Function Enable (Input): CMOS-compatible control input. Logic high = enable, logic low or open = shutdown. Supply (Input). Flag (Output): Open-collector error flag output. Active low = output undervoltage. Adjustment Input: Feedback input. Connect to resistive voltage-divider network. Regulator Output. Ground.
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Absolute Maximum Ratings(1)
Supply Voltage (VIN) ......................................................6.5V Enable Voltage (VEN).....................................................6.5V Lead Temperature (soldering, 5 sec.)........................ 260C Storage Temperature (Ts) .........................-65C to +150C EDS Rating................................................................ Note 3
Operating Ratings(2)
Supply Voltage (VIN)...................................... +2.25V to +6V Enable Voltage (VEN)............................................ 0V to +6V Maximum Power Dissipation (PD(MAX)) ...................... Note 4 Junction Temperature (TJ) ........................ -40C to +125C Package Thermal Resistance MSOP-8 (JA) .....................................................80C/W
Electrical Characteristics(5)
VIN = VOUT + 1V; VEN = 2.25V; TJ = 25C, bold values indicate -40C< TJ < +125C, unless noted.
Symbol VOUT Parameter Output Voltage Line Regulation Load Regulation VOUT/T VDO Output Voltage Temp. Coefficient, Note 6 Dropout Voltage, Note 7 IOUT = 100mA, VOUT = -1% IOUT = 500mA, VOUT = -1% IOUT = 750mA, VOUT = -1% IGND Ground Current, Note 8 IOUT = 100mA, VIN = VOUT + 1V IOUT = 500mA, VIN = VOUT + 1V IOUT = 750mA, VIN = VOUT + 1V IOUT(lim) VEN IEN Current Limit Enable Input Voltage Enable Input Current VOUT = 0V, VIN = VOUT + 1V logic low (off) logic high (on) VEN = 2.25V VEN = 0.8V Flag Output IFLG(leak) VFLG(do) VFLG Output Leakage Current Output Low Voltage Low Threshold High Threshold Hysteresis Adjustable Output Only Reference Voltage Adjust Pin Bias Current 1.227 1.215 1.240 40 1.252 1.265 80 120 V V nA nA VOH = 6V VIN = 2.250V, IOL, = 250A % of VOUT % of VOUT 1 93 99.2 0.01 250 1 2 500 A A mV % % % 2.25 1 10 30 2 4 Enable Input 0.8 V V A A A Condition 10mA 10mA IOUT 750mA, VOUT + 1V VIN 6V IOUT = 10mA, VOUT + 1V VIN 6V VIN = VOUT + 1V, 10mA IOUT 750mA Min -1 -2 0.06 0.2 40 125 210 280 700 3.7 7.5 1.6 15 2.5 500 200 250 Typ Max 1 2 0.5 1 Units % % % % ppm/C mV mV mV mV A mA mA A
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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) / JA, where JA depends upon the printed circuit layout. See "Applications Information." 5. Specification for packaged product only. 6. Output voltage temperature coefficient is VOUT(worst case) / (TJ(max) - TJ(min)) where T J(max) is +125C and TJ(min) is -40C. 7. VDO = VIN - VOUT when VOUT decreases to 98% of its nominal output voltage with VIN = VOUT + 1V. For output voltages below 1.75V, dropout voltage is the input-to-output voltage differential with the minimum input voltage being 2.25V. Minimum input operating voltage is 2.25V. 8. IGND is the quiescent current. IIN = IGND + IOUT.
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Typical Characteristics
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Typical Characteristics (cont.)
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Typical Characteristics (cont.)
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Functional Characteristics
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Functional Diagrams
MIC3775 Fixed Regulator with Flag and Enable Block Diagram
MIC3775 Adjustable Regulator Block Diagram
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MIC3775 the same minimum capacitance over the equivalent operating temperature range. Input Capacitor An input capacitor of 1F or greater is recommended when the device is more than 4 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. Error Flag The MIC3775 features an error flag (FLG), which monitors the output voltage and signals an error condition when this voltage drops 5% below its expected value. The error flag is an open-collector output that pulls low under fault conditions and may sink up to 10mA. Low output voltage signifies a number of possible problems, including an overcurrent fault (the device is in current limit) or low input voltage. The flag output is inoperative during overtemperature conditions. A pull-up resistor from FLG to either VIN or VOUT is required for proper operation. For information regarding the minimum and maximum values of pull-up resistance, refer to the graph in the "Typical Characteristics" section of the data sheet. Enable Input The MIC3775 features an active-high enable input (EN) that allows 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 and pulled up to the maximum supply voltage. Transient Response and 3.3V to 2.5V or 2.5V to 1.8V or 1.65V Conversion The MIC3775 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, 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 or 2.5V to 1.8V or 1.65V, the NPN-based regulators are already operating in dropout, with typical dropout requirements of 1.2V or greater. To convert down to 2.5V or 1.8V without operating in dropout, NPN-based regulators require an input voltage of 3.7V at the very least. The MIC3775 regulator will provide excellent performance 10
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Application Information
The MIC3775 is a high-performance low-dropout voltage regulator suitable for moderate to high-current voltage regulator applications. Its 500mV dropout voltage at full load and overtemperature makes it especially valuable in battery-powered systems and as high-efficiency noise filters in post-regulator applications. Unlike older NPNpass 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 Supereta PNP(R) process reduces this drive requirement to only 2% of the load current. The MIC3775 regulator is 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.
Figure 1. Capacitor Requirements
Output Capacitor The MIC3775 requires an output capacitor for stable operation. As a Cap LDO, the MIC3775 can operate with ceramic output capacitors as long as the amount of capacitance is 10F or greater. For values of output capacitance lower than 10F, the recommended ESR range is 200m to 2. The minimum value of output capacitance recommended for the MIC3775 is 4.7F. For 10F or greater the ESR range recommended is less than 1. Ultra-low ESR ceramic capacitors are recommended for output capacitance of 10F 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
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Micrel, Inc. with an input as low as 3.0V or 2.5V respectively. This gives the PNP-based regulators a distinct advantage over older, NPN-based linear regulators. Minimum Load Current The MIC3775 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
MIC3775
Using the power MSOP-8 reduces the JC dramatically and allows the user to reduce CA. The total thermal resistance, JA (junction-to-ambient thermal resistance) is the limiting factor in calculating the maximum power dissipation capability of the device. Typically, the power MSOP-8 has a JA of 80C/W, this is significantly lower than the standard MSOP-8 which is typically 160C/W. CA 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 sink-toambient thermal resistance. Low-dropout linear regulators from Micrel are rated to a maximum junction temperature of 125C. 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 heatsink must be used.
R1 VOUT = 1.240V 1 + R2
Figure 2. Adjustable Regulator with Resistors
The MIC3775 allows programming the output voltage anywhere between 1.24V and the 6V maximum operating rating of the family. Two resistors are used. Resistors can be quite large, up to 1M, because of the very high input impedance and low bias current of the sense comparator. The resistor values are calculated by: V R1 = R2 OUT - 1 1.240 Where VO 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).
Figure 3. Thermal Resistance
Power MSOP-8 Thermal Characteristics One of the secrets of the MIC3775's performance is its power MSOP-8 package featuring half the thermal resistance of a standard MSOP-8 package. Lower thermal resistance means more output current or higher input voltage for a given package size. 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, JC (junction-to-case thermal resistance) and CA (case-toambient thermal resistance). See Figure3. JC is the resistance from the die to the leads of the package. CA is the resistance from the leads to the ambient air and it includes CS (case-to- sink thermal resistance) and SA (sink-to-ambient thermal resistance). December 2006 11
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 4. Copper Area vs. Power-MSOP Power Dissipation (TJA)
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MIC3775 PD = (VIN - VOUT) IOUT + VINxIGND If we use a 2.5V output device and a 3.3V input at an output current of 750mA, then our power dissipation is as follows: PD = (3.3V - 2.5V) x 750mA + 3.3V x 7.5mA PD = 600mW + 25mW PD = 625mW From Figure 4, the minimum amount of copper required to operate this application at a T of 75C is 160mm2.
Figure 5. Copper Area vs. Power-MSOP Power Dissipation (TA)
T = TJ(max) - TA(max) TJ(max) = 125C = maximum ambient operating TA(max) temperature For example, the maximum ambient temperature is 50C, the T is determined as follows: T = 125C - 50C T = 75C 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:
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: 25C, 50C and 85C. From these curves, the minimum amount of copper can be determined by knowing the maximum power dissipation required. If the maximum ambient temperature is 50C and the power dissipation is as above, 625mW, the curve in Figure 5 shows that the required area of copper is 160mm2.The JA of this package is ideally 80C/W, but it will vary depending upon the availability of copper ground plane to which it is attached.
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Package Information
8-Pin MSOP (MM)
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) 2002 Micrel, Incorporated.
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