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MIC23031
4MHz PWM 400mA Buck Regulator with HyperLight LoadTM
General Description
The MIC23031 is a high-efficiency 4MHz 400mA synchronous buck regulator with HyperLight LoadTM mode. HyperLight LoadTM provides very-high efficiency at light loads and ultra-fast transient response which is perfectly suited for supplying processor core voltages. An additional benefit of this proprietary architecture is very-low output ripple voltage throughout the entire load range with the use of small output capacitors. The tiny 1.6mm x 1.6mm Thin MLF(R) package saves precious board space and requires only three external components. The MIC23031 is designed for use with a very-small inductor, down to 0.47H, and an output capacitor as small as 2.2F that enables a sub-1mm height. The MIC23031 has a very-low quiescent current of 21A and achieves as high as 88% efficiency at 1mA. At higher loads, the MIC23031 provides a constant switching frequency around 4MHz while achieving peak efficiencies up to 93%. The MIC23031 is available in a 6-pin 1.6mm x 1.6mm Thin MLF(R) package with an operating junction temperature range from -40C to +125C. Data sheets and support documentation can be found on Micrel's web site at: www.micrel.com.
Features
* * * * * * * Input voltage: 2.7V to 5.5V 400mA output current Up to 93% efficiency and 88% at 1mA 21A typical quiescent current 4MHz PWM operation in continuous mode Ultra-fast transient response Low voltage output ripple - 20mVpp ripple in HyperLight LoadTM mode - 3mV output voltage ripple in full PWM mode 0.01A shutdown current Fixed and adjustable output voltage options available 6-pin 1.6mm x 1.6mm Thin MLF(R) -40C to +125C junction temperature range Mobile handsets Portable media/MP3 players Portable navigation devices (GPS) WiFi/WiMax/WiBro modules Digital Cameras Wireless LAN cards USB-powered devices Portable applications
* * * * * * * * * * * *
Applications
Typical Application
HyperLight Load is a trademark of Micrel, Inc MLF and MicroLead Frame are registered trademarks of Amkor Technology, 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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Micrel Inc.
MIC23031
Ordering Information
Part Number MIC23031-AYMT MIC23031-GYMT MIC23031-FYMT MIC23031-4YMT MIC23031-CYMT
Notes: 1. 2. Other options available. Contact Micrel for details. Thin MLF is GREEN RoHS-compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
(R)
Marking Code GEA GEG GEF GE4 GEC
Nominal Output Voltage Adjustable 1.8V 1.5V 1.2V 1.0V
Junction Temperature Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C
Package 6-Pin 1.6mm x 1.6mm Thin MLF(R) 6-Pin 1.6mm x 1.6mm Thin MLF 6-Pin 1.6mm x 1.6mm Thin MLF
(R) (R) (R) (R)
Lead Finish Pb-Free Pb-Free Pb-Free Pb-Free Pb-Free
6-Pin 1.6mm x 1.6mm Thin MLF 6-Pin 1.6mm x 1.6mm Thin MLF
Pin Configuration
VIN SW SNS 1 2 3 6 5 4 PGND AGND EN VIN SW SNS 1 2 3 6 5 4 GND FB EN
6-Pin 1.6 x 1.6mm Thin MLF(R) (MT) Fixed (Top View)
6-Pin 1.6 x 1.6mm Thin MLF(R) (MT) Adjustable (Top View)
Pin Description
Fixed Option 1 2 3 4 5 - 6 - ePad Adjustable Option 1 2 3 4 - 5 - 6 ePad Pin Name VIN SW SNS EN AGND FB PGND GND HS PAD Pin Function Input Voltage: Connect a capacitor to ground to decouple the noise. Switch (Output): Internal power MOSFET output switches. Sense: Connect to VOUT as close to output capacitor as possible to sense output voltage. Enable (Input): Logic high enables operation of the regulator. Logic low will shut down the device. Do not leave floating. Analog Ground: Connect to central ground point where all high current paths meet (CIN, COUT, PGND) for best operation. Feedback (Input): Connect resistor divider at this node to set output voltage. Resistors should be selected based on a nominal VFB of 0.62V. Power Ground. Ground. Connect to PGND or GND.
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Absolute Maximum Ratings(1)
Supply Voltage (VIN) . ..............................................6V Sense (VSNS).. ..................................................................6V Output Switch Voltage ..................................................6V Enable Input Voltage (VEN)................................-0.3V to VIN Storage Temperature Range .................-65C to +150C ESD Rating(3) ................................................. ESD Sensitive
Operating Ratings(2)
Supply Voltage (VIN)... ................................2.7V to 5.5V Enable Input Voltage (VEN) .. ............................0V to VIN Output Voltage Range (VSNS) ......................0.7V to 3.6V Junction Temperature Range (TJ).. ....-40C TJ +125C Thermal Resistance 1.6 x 1.6mm Thin MLF(R)-6 (JA).......................92.4C/W
Electrical Characteristics(4)
TA = 25C; VIN = VEN = 3.6V; L = 1H; COUT = 4.7F unless otherwise specified. Bold values indicate -40C TJ +125C, unless noted. Parameter Supply Voltage Range Under-Voltage Lockout Threshold Quiescent Current Shutdown Current Output Voltage Accuracy Feedback Voltage Current Limit Output Voltage Line Regulation Output Voltage Load Regulation PWM Switch ON-Resistance Frequency Soft-Start Time Enable Threshold Enable Input Current Over-Temperature Shutdown Over-Temperature Shutdown Hysteresis
Notes: 1. 2. 3. 4. 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. Human body model, 1.5k in series with 100pF. Specification for packaged product only.
Condition (Turn-on) IOUT = 0mA , SNS > 1.2 * VOUT Nominal VEN = 0V, VIN = 5.5V VIN = 3.6V; ILOAD = 20mA Adjustable Option Only SNS = 0.9*VOUTNOM VIN = 3.0V to 5.5V, VOUT = 1.2V, ILOAD = 20mA, 20mA < ILOAD < 400mA, VOUT = 1.2V, VIN = 3.6V ISW = 100mA PMOS ISW = -100mA NMOS IOUT = 120mA VOUT = 90%
Min. 2.7 2.45
Typ. 2.55 21 0.01
Max. 5.5 2.65 35 4 +2.5
Units V V A A % V
-2.5 0.62 0.41 0.7 0.3 0.7 0.65 0.8 4 100 0.5 0.9 0.1 160 20
1
A %/V % MHz s
1.2 2
V A C C
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Typical Characteristics
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Typical Characteristics (Continued)
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MIC23031
Functional Characteristics
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Functional Characteristics (Continued)
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Functional Characteristics (Continued)
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Functional Diagram
VIN
EN UVLO CONTROL LOGIC Timer & Softstart Gate Drive SW
Reference
Current Limit ERROR COMPARATOR ZERO 1 ISENSE PGND SNS
AGND
Simplified MIC23031 Fixed Functional Block Diagram
VIN
EN UVLO CONTROL LOGIC Timer & Softstart Gate Drive SW
Reference
Current Limit ERROR COMPARATOR ZERO 1 ISENSE SNS FB
GND
Simplified MIC23031 Adjustable Functional Block Diagram
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MIC23031 AGND (Fixed Output Only) The analog ground (AGND) is the ground path for the biasing and control circuitry. The current loop for the signal ground should be separate from the power ground (PGND) loop. Refer to the layout recommendations for more details. FB (Adjustable Output Only) The feedback pin (FB) allows the regulated output voltage to be set by applying an external resistor network. The internal reference voltage is 0.62V and the recommended value of R2 is 200k. The output voltage is calculated from the equation below.
R1 VOUT = 0.62V + 1 200 k
MIC23031
VIN C1 EN
Functional Description
VIN The input supply (VIN) provides power to the internal MOSFETs for the switch mode regulator along with the internal control circuitry. The VIN operating range is 2.7V to 5.5V so an input capacitor, with a minimum voltage rating of 6.3V, is recommended. Due to the high switching speed, a minimum 2.2F bypass capacitor placed close to VIN and the power ground (PGND) pin is required. Refer to the layout recommendations for details. EN A logic high signal on the enable pin activates the output voltage of the device. A logic low signal on the enable pin deactivates the output and reduces supply current to 0.01A. MIC23031 features built-in soft-start circuitry that reduces in-rush current and prevents the output voltage from overshooting at start up. Do not leave floating. SW The switch (SW) connects directly to one end of the inductor and provides the current path during switching cycles. The other end of the inductor is connected to the load, SNS pin and output capacitor. Due to the high speed switching on this pin, the switch node should be routed away from sensitive nodes whenever possible. SNS The sense (SNS) pin is connected to the output of the device to provide feedback to the control circuitry. The SNS connection should be placed close to the output capacitor. Refer to the layout recommendations for more details.
VIN
SW SNS
VOUT L1 R1 C2
EN GND
FB
R2 GND
GND
Figure 1. MIC23031-AYMT Schematic
PGND / GND The power ground pin is the ground path for the high current in PWM mode. The current loop for the power ground should be as small as possible and separate from the analog ground (AGND) loop as applicable. Refer to the layout recommendations for more details.
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MIC23031 The MIC23031 was designed for use with an inductance range from 0.47H to 4.7H. Typically, a 1H inductor is recommended for a balance of transient response, efficiency and output ripple. For faster transient response, a 0.47H inductor will yield the best result. For lower output ripple, a 4.7H inductor is recommended. Maximum current ratings of the inductor are generally given in two methods; permissible DC current and saturation current. Permissible DC current can be rated either for a 40C temperature rise or a 10% to 20% loss in inductance. Ensure the inductor selected can handle the maximum operating current. When saturation current is specified, make sure that there is enough margin so that the peak current does not cause the inductor to saturate. Peak current can be calculated as follows:
1 - VOUT /VIN IPEAK = IOUT + VOUT 2x f xL
Application Information
The MIC23031 is a high-performance DC/DC step-down regulator offering a small solution size. Supporting an output current up to 400mA inside a tiny 1.6mm x 1.6mm Thin MLF(R) package and requiring only three external components, the MIC23031 meets today's miniature portable electronic device needs. Using the HyperLight LoadTM switching scheme, the MIC23031 is able to maintain high efficiency throughout the entire load range while providing ultra-fast load transient response. The following sections provide additional device application information. Input Capacitor A 2.2F ceramic capacitor or greater should be placed close to the VIN pin and PGND / GND pin for bypassing. A TDK C1608X5R0J475K, size 0603, 4.7F ceramic capacitor is recommended based upon performance, size and cost. A X5R or X7R temperature rating is recommended for the input capacitor. Y5V temperature rating capacitors, aside from losing most of their capacitance over temperature, can also become resistive at high frequencies. This reduces their ability to filter out high-frequency noise. Output Capacitor The MIC23031 was designed for use with a 2.2F or greater ceramic output capacitor. Increasing the output capacitance will lower output ripple and improve load transient response but could increase solution size or cost. A low equivalent series resistance (ESR) ceramic output capacitor such as the TDK C1608X5R0J475K, size 0603, 4.7F ceramic capacitor is recommended based upon performance, size and cost. Both the X7R or X5R temperature rating capacitors are recommended. The Y5V and Z5U temperature rating capacitors are not recommended due to their wide variation in capacitance over temperature and increased resistance at high frequencies. Inductor Selection When selecting an inductor, it is important to consider the following factors (not necessarily in the order of importance): * * * * Inductance Rated current value Size requirements DC resistance (DCR)
As shown by the calculation above, the peak inductor current is inversely proportional to the switching frequency and the inductance; the lower the switching frequency or the inductance the higher the peak current. As input voltage increases, the peak current also increases. The size of the inductor depends on the requirements of the application. Refer to Typical Application Circuit and Bill of Materials for details. DC resistance (DCR) is also important. While DCR is inversely proportional to size, DCR can represent a significant efficiency loss. Refer to the Efficiency Considerations. Compensation The MIC23031 is designed to be stable with a 0.47H to 4.7H inductor with a minimum of 2.2F ceramic (X5R) output capacitor. Duty Cycle The typical maximum duty cycle of the MIC23031 is 80%. Efficiency Considerations Efficiency is defined as the amount of useful output power, divided by the amount of power supplied.
V xI Efficiency % = OUT OUT V xI IN IN x 100
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Micrel, Inc. Maintaining high efficiency serves two purposes. It reduces power dissipation in the power supply, reducing the need for heat sinks and thermal design considerations and it reduces consumption of current for battery powered applications. Reduced current draw from a battery increases the devices operating time and is critical in hand held devices. There are two types of losses in switching converters; DC losses and switching losses. DC losses are simply the power dissipation of I2R. Power is dissipated in the high side switch during the on cycle. Power loss is equal to the high side MOSFET RDSON multiplied by the Switch Current squared. During the off cycle, the low side Nchannel MOSFET conducts, also dissipating power. Device operating current also reduces efficiency. The product of the quiescent (operating) current and the supply voltage represents another DC loss. The current required driving the gates on and off at a constant 4MHz frequency and the switching transitions make up the switching losses. The DCR losses can be calculated as follows: L Pd = IOUT2 x DCR
MIC23031
Eq. 3
From that, the loss in efficiency due to inductor resistance can be calculated as follows:
V xI Efficiency % = OUT OUT V xI IN IN x 100
Efficiency loss due to DCR is minimal at light loads and gains significance as the load is increased. Inductor selection becomes a trade-off between efficiency and size in this case. HyperLight LoadTM Mode MIC23031 uses a minimum on and off time proprietary control loop (patented by Micrel). When the output voltage falls below the regulation threshold, the error comparator begins a switching cycle that turns the PMOS on and keeps it on for the duration of the minimum-on-time. This increases the output voltage. If the output voltage is over the regulation threshold, then the error comparator turns the PMOS off for a minimumoff-time until the output drops below the threshold. The NMOS acts as an ideal rectifier that conducts when the PMOS is off. Using a NMOS switch instead of a diode allows for lower voltage drop across the switching device when it is on. The asynchronous switching combination between the PMOS and the NMOS allows the control loop to work in discontinuous mode for light load operations. In discontinuous mode, the MIC23031 works in pulse frequency modulation (PFM) to regulate the output. As the output current increases, the off-time decreases, thus provides more energy to the output. This switching scheme improves the efficiency of MIC23031 during light load currents by only switching when it is needed. As the load current increases, the MIC23031 goes into continuous conduction mode (CCM) and switches at a frequency centered at 4MHz. The equation to calculate the load when the MIC23031 goes into continuous conduction mode may be approximated by the following formula:
V - VOUT x D ILOAD = IN 2L x f
Figure 2. MIC23031 Efficiency Curve
The figure above shows an efficiency curve. From no load to 100mA, efficiency losses are dominated by quiescent current losses, gate drive and transition losses. By using the HyperLight LoadTM mode, the MIC23031 is able to maintain high efficiency at low output currents. Over 100mA, efficiency loss is dominated by MOSFET RDSON and inductor losses. Higher input supply voltages will increase the Gate-to-Source threshold on the internal MOSFETs, thereby reducing the internal RDSON. This improves efficiency by reducing DC losses in the device. All but the inductor losses are inherent to the device. In which case, inductor selection becomes increasingly critical in efficiency calculations. As the inductors are reduced in size, the DC resistance (DCR) can become quite significant.
(
)
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Micrel, Inc. As shown in the previous equation, the load at which MIC23031 transitions from HyperLight LoadTM mode to PWM mode is a function of the input voltage (VIN), output voltage (VOUT), duty cycle (D), inductance (L) and frequency (f). This is illustrated in the graph below. Since the inductance range of MIC23031 is from 0.47H to 4.7H, the device may then be tailored to enter HyperLight LoadTM mode or PWM mode at a specific load current by selecting the appropriate inductance. For example, in Figure 3, when the inductance is 4.7H the MIC23031 will transition into PWM mode at a load of approximately 4mA. Under the same condition, when the inductance is 1H, the MIC23031 will transition into PWM mode at approximately 70mA.
MIC23031
Figure 3. MIC23031 SW Frequency vs. Output Current
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MIC23031 Typical Application Circuit (Fixed 1.8V)
U1 MIC23031
VIN 2.7 to 5.5V C1 EN
1
VIN
SW 2
VOUT
L1 C2
4
EN AGND 5
SNS 3 PGND 6
GND
GND
Bill of Materials
Item C1, C2 Part Number C1608X5R0J475K LQM21PN1R0M00 LQH32CN1R0M33 L1 LQM31PN1R0M00 GLF251812T1R0M LQM31PNR47M00 MIPF2520D1R5 U1
Notes: 1. 2. 3. 4. TDK: www.tdk.com. Murata: www.murata.com. FDK: www.fdk.co.jp. Micrel, Inc.: www.micrel.com.
Manufacturer TDK
(1) (2) (2)
Description 4.7F Ceramic Capacitor, 6.3V, X5R, Size 0603 1H, 0.8A, 190m, L2mm x W1.25mm x H0.5mm 1H, 1A, 60m, L3.2mm x W2.5mm x H2.0mm 1H, 1.2A, 120m, L3.2mm x W1.6mm x H0.95mm 1H, 0.8A, 100m, L2.5mm x W1.8mm x H1.35mm 0.47H, 1.4A, 80m, L3.2mm x W1.6mm x H0.85mm 1.5H, 1.5A, 70m, L2.5mm x W2mm x H1.0mm 4MHz 400mA Buck Regulator with HyperLight LoadTM Mode
Qty. 2
Murata Murata TDK
Murata(2)
(1)
1
Murata(2) FDK(3) Micrel, Inc.(4)
MIC23031-xYMT
1
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MIC23031
MIC23031 Typical Application Circuit (Adjustable 1.8V)
U1 - MIC23031 VIN C1 EN 4 EN GND 6 SNS 3 FB 5 1 VIN SW 2 VOUT L1 R1 383k C2
GND
R2 200k
GND
Bill of Materials
Item Part Number Manufacturer Description Qty.
C1, C2 R1 R2
C1608X5R0J475K CRCW06033833FT1 CRCW06032003FT1 LQM21PN1R0M00 LQH32CN1R0M33 LQM31PN1R0M00 GLF251812T1R0M LQM31PNR47M00 MIPF2520D1R5
TDK
(1) (2) (2)
4.7F Ceramic Capacitor, 6.3V, X5R, Size 0603 383k, 1%, Size 0603 200k, 1%, Size 0603 1H, 0.8A, 190m, L2mm x W1.25mm x H0.5mm 1H, 1A, 60m, L3.2mm x W2.5mm x H2.0mm 1H, 1.2A, 120m, L3.2mm x W1.6mm x H0.95mm 1H, 0.8A, 100m, L2.5mm x W1.8mm x H1.35mm 0.47H, 1.4A, 80m, L3.2mm x W1.6mm x H0.85mm 1.5H, 1.5A, 70m, L2.5mm x W2mm x H1.0mm
4MHz 400mA Buck Regulator with HyperLight LoadTM Mode
2 1 1
Vishay Vishay
Murata(3) Murata(3) Murata
(3)
L1
TDK(1) Murata(3) FDK
(4)
1
U1
Notes: 1. 2. 3. 4. 5.
MIC23031-AYMT
TDK: www.tdk.com. Vishay: www.vishay.com. Murata: www.murata.com. FDK: www.fdk.co.jp. Micrel, Inc.: www.micrel.com.
Micrel, Inc.(5)
1
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PCB Layout Recommendations (Fixed)
Fixed Top Layer
Fixed Bottom Layer
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PCB Layout Recommendations (Adjustable)
Adjustable Top Layer
Adjustable Bottom Layer
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Package Information
6-pin 1.6mm x 1.6mm Thin MLF(R) (MT)
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
Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual property rights is granted by this document. Except as provided in Micrel's terms and conditions of sale for such products, Micrel assumes no liability whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right 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) 2008 Micrel, Incorporated.
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