MIC33153 4MHz PWM 1.2A Internal Inductor Buck Regulator with HyperLight Load™ and Power Good General Description Features The MIC33153 is a high-efficiency 4MHz 1.2A synchronous buck regulator with an internal inductor, HyperLight Load™ mode, Power Good (PG) output indicator, and programmable soft start. HyperLight Load™ provides very high efficiency at light loads and ultra-fast transient response which makes the MIC33153 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 MIC33153 is designed so that only two external capacitors as small as 2.2µF are needed for stability. This gives the MIC33153 the ease of use of an LDO with the efficiency of a HyperLight Load™ DC converter. The TM MIC33153 achieves efficiency in HyperLight Load mode as high as 85% at 1mA, with a very low quiescent current of 22µA. At higher loads, the MIC33153 provides a constant switching frequency up to 4MHz. The MIC33153 is available in 14-pin 3.0mm x 3.5mm MLF® package with an operating junction temperature range from –40°C to +125°C. Datasheets and support documentation can be found on Micrel’s web site at: www.micrel.com. • Internal inductor − Simplifies design to two external capacitors • Input voltage: 2.7V to 5.5V • Output voltage: fixed or adjustable (0.62V to 3.6V) • Up to 1.2 A output current • Up to 93% peak efficiency • 85% typical efficiency at 1mA • Power Good (PG) output • Programmable soft start • 22µA typical quiescent current • 4MHz PWM operation in continuous mode • Ultra-fast transient response • Low ripple output voltage ™ − 35mVpp ripple in HyperLight Load mode − 7mV output voltage ripple in full PWM mode • 0.01µA shutdown current • Thermal shutdown and current limit protection • 14-pin 3.0 x 3.5 x 1.1mm MLF® package • –40°C to +125°C junction temperature range Applications • Solid State Drives (SSD) • Mobile handsets • Portable media/MP3 players • Portable navigation devices (GPS) • WiFi/WiMax/WiBro modules • Wireless LAN cards • Portable applications ____________________________________________________________________________________________________________ Typical Application Fixed Output Voltage Adjustable Output Voltage HyperLight Load is a trademark of Micrel, Inc. MLF and MicroLeadFrame are registered trademark Amkor Technology Inc. Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-01200 • fax + 1 (408) 474-1000 • http://www.micrel.com September 2010 M9999-092910-A Micrel Inc. MIC33153 Ordering Information Part Number1 Marking Code −4 MIC33153-4YHJ 33153 MIC MIC33153YHJ 33153 Nominal Output Voltage Junction Temperature Range 1.2V –40°C to +125°C 14-pin 3.0 x 3.5 x 1.1mm MLF® Adjustable –40°C to +125°C 14-pin 3.0 x 3.5 x 1.1mm MLF® Package2 Notes: 1. Other options available (1V - 3.3V). Contact Micrel Marketing for details. 2. MLF is GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free. ® Pin Configuration 14- Pin 3.0mm x 3.5mm MLF® (HJ) Fixed Output Voltage (Top View) ® 14- Pin 3.0mm x 3.5mm MLF (HJ) Adjustable Output Voltage (Top View) Pin Description Pin Number (Fixed) Pin Number (Adjustable) Pin Name 1 1 SS Soft Start: Place a capacitor from this pin to ground to program the soft start time. Do not leave floating, 100pF minimum CSS is required. 2 2 AGND Analog Ground: Connect to central ground point where all high current paths meet (CIN, COUT, PGND) for best operation. 3 3 VIN 4 4 PGND 5,6,7 5,6,7 OUT 8,9,10 8,9,10 SW Switch: Internal power MOSFET output switches before Inductor Enable: Logic high enables operation of the regulator. Logic low will shut down the device. Do not leave floating. Pin Function Input Voltage: Connect a capacitor to ground to decouple the noise. Power Ground. Output Voltage: The output of the regulator. Connect to SNS pin. For adjustable option, connect to feedback resistor network. 11 11 EN 12 12 SNS Sense: Connect to VOUT as close to output capacitor as possible to sense output voltage. 13 13 PG Power Good: Open drain output for the Power Good (PG) indicator. Use a pull up resistor from this pin to a voltage source to detect a power good condition. 14 − NC Not Internally Connected. − 14 FB Feedback: Connect a resistor divider from the output to ground to set the output voltage. September 2010 2 M9999-092910-A Micrel Inc. MIC33153 Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VIN) .......................................... −0.3V to 6V Sense Voltage (VSNS) ........................................−0.3V to VIN Output Switch Voltage (VSW) .............................−0.3V to VIN Enable Input Voltage (VEN)................................−0.3V to VIN Power Good (PG) Voltage (VPG) .......................−0.3V to VIN Storage Temperature Range ..……………−65°C to +150°C Lead Temperature (soldering, 10 sec.)...................... 260°C ESD Rating(3) ................................................. ESD Sensitive Supply Voltage (VIN)... …………………………..2.7V to 5.5V Enable Input Voltage (VEN) .. ……………………….0V to VIN Sense Voltage (VSNS) ..................................... 0.62V to 3.6V Junction Temperature Range (TJ).. ….−40°C ≤ TJ ≤ +125°C Thermal Resistance 3.0mm x 3.5mm MLF®-14 (θJA)..........................55°C/W Electrical Characteristics(4) TA = 25°C; VIN = VEN = 3.6V; COUT = 4.7µF unless otherwise specified. Bold values indicate –40°C ≤ TJ ≤ +125°C, unless noted. Parameter Condition Min. Supply Voltage Range Under-Voltage Lockout Threshold (Turn-On) 2.45 Under-Voltage Lockout Hysteresis IOUT = 0mA , SNS > 1.2 * VOUT Nominal Shutdown Current VEN = 0V; VIN = 5.5V VIN = 3.6V if VOUTNOM < 2.5V, ILOAD = 20mA VIN = 4.5V if VOUTNOM ≥ 2.5V, ILOAD = 20mA Feedback Regulation Voltage ILOAD = 20mA Current Limit SNS = 0.9*VOUTNOM Output Voltage Line Regulation Output Voltage Load Regulation PWM Switch ON-Resistance 2.55 Max. Units 5.5 V 2.65 V 75 Quiescent Current Output Voltage Accuracy Typ. 2.7 mV 22 45 µA 0.01 5 µA +2.5 % 0.6355 V −2.5 0.6045 0.62 2.2 3.3 A VIN = 3.6V to 5.5V if VOUTNOM < 2.5V, ILOAD = 20mA VIN = 4.5V to 5.5V if VOUTNOM ≥ 2.5V, ILOAD = 20mA 0.3 %/V 1mA < ILOAD < 1A, VIN = 3.6V if VOUTNOM < 2.5V 0.8 1mA < ILOAD < 1A, VIN = 5.0V if VOUTNOM ≥ 2.5V 0.85 ISW = 100mA PMOS 0.2 ISW = −100mA NMOS 0.19 %/A Ω Maximum Switching Frequency IOUT = 300mA 4 MHz Soft Start Time VOUT = 90%, CSS = 470pF 320 µs Soft Start Current VSS = 0V 2.7 µA PG Threshold (Rising) 86 PG Threshold Hysteresis PG Delay Time Rising Enable Threshold Turn-On 92 96 % 7 % 68 µs 0.9 1.2 V Enable Input Current 0.1 2 µA Over-Temperature Shutdown 160 °C Over-Temperature Shutdown Hysteresis 20 °C 0.5 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. Human body model, 1.5kΩ in series with 100pF. 4. Specification for packaged product only. September 2010 3 M9999-092910-A Micrel Inc. MIC33153 Typical Characteristics Efficiency (VOUT = 2.5V) 90 90 90 80 80 80 70 70 60 VIN = 4.2V VIN = 5.0V 50 VIN = 5.5V 40 30 60 VIN = 5.5V 50 40 30 10 100 1000 10000 1 Efficiency (VOUT = 1.5V) 10 100 1000 VIN = 3.0V 20 60 VIN = 3.6V 50 EFFICIENCY (%) 70 EFFICIENCY (%) 70 30 VIN = 4.2V 40 30 20 0 10 100 1000 10000 VIN = 3.6V 50 30 COUT = 4.7µF 0 1 10 OUTPUT CURRENT (mA) 100 1000 10000 1 10 OUTPUT CURRENT (mA) Current Limit vs. Input Voltage VIN = 4.2V 40 10 COUT = 4.7µF 0 1 60 20 10 COUT = 4.7µF 10000 VIN = 3.0V 90 70 40 1000 Efficiency (VOUT = 1.0V) 80 VIN = 4.2V 100 100 80 10 10 OUTPUT CURRENT (mA) Efficiency (VOUT = 1.2V) 90 VIN = 3.6V COUT = 4.7µF 1 80 50 VIN = 4.2V 30 10000 100 VIN = 3.0V VIN = 3.6V 40 OUTPUT CURRENT (mA) 100 60 VIN = 3.0V 50 0 OUTPUT CURRENT (mA) 90 60 10 COUT = 4.7µF 0 1 70 20 10 COUT = 4.7µF 0 Quiescent Current vs. Input Voltage 40 100 1000 10000 OUTPUT CURRENT (mA) Shutdown Current vs. Input Voltage 30 QUIESCENT CURRENT (µA) 4.50 4.00 3.50 3.00 2.50 2.00 1.50 1.00 35 T = 20°C T = 125°C SHUTDOWN CURRENT (nA) 5.00 30 25 20 15 T = - 45°C No Switching SNS > 1.2 * VOUTNOM 10 5 COUT = 4.7µF 0.50 0 0.00 2.7 3.2 3.7 4.2 4.7 5.2 INPUT VOLTAGE (V) 2.7 5.7 1.880 OUTPUT VOLTAGE (V) IOUT = 160mA 1.840 1.820 1.800 1.780 IOUT = 1mA 1.760 1.740 VOUTNOM = 1.8V 1.720 4.2 4.7 5.2 3.5 4 4.5 INPUT VOLTAGE (V) September 2010 10 5 2.5 3.0 1.880 VOUTNOM = 1.8V 1.860 COUT = 4.7µF 1.820 1.800 1.780 1.760 1.740 IOUT = 1000mA IOUT = 500mA 5 5.5 5.5 Load Regulation IOUT = 300mA 1.840 3.5 4.0 4.5 5.0 INPUT VOLTAGE (V) 1.300 VIN = 4.2V 1.250 VIN = 3.6V 1.200 1.150 VIN = 3.0V VOUTNOM = 1.2V COUT = 4.7µF 1.700 1.700 3 15 1.720 COUT = 4.7µF 2.5 20 0 5.7 Line Regulation (Heavy Load) 1.900 IOUT = 40mA 1.860 3.7 25 INPUT VOLTAGE (V) Line Regulation (Light Load) 1.900 3.2 OUTPUT VOLTAGE (V) EFFICIENCY (%) VIN = 4.2V VIN = 3.6V 20 10 CURRENT LIMIT (A) EFFICIENCY (%) 100 20 OUTPUT VOLTAGE (V) Efficiency (VOUT = 1.8V) 100 EFFICIENCY (%) EFFICIENCY (%) Efficiency (VOUT = 3.3V) 100 1.100 2.5 3 3.5 4 4.5 INPUT VOLTAGE (V) 4 5 5.5 0 200 400 600 800 1000 1200 OUTPUT CURRENT (mA) M9999-092910-A Micrel Inc. MIC33153 Typical Characteristics Feedback Voltage vs. Temperature UVLO Threshold vs. Temperature 1.8 2.55 0.62 0.61 0.60 VIN = 3.6V 0.59 -40 -20 VEN THRESHOLD (V) 0.63 ON 2.54 2.53 2.52 2.51 2.50 2.49 2.48 OFF 2 1.6 RISE TIME (µs) Enable ON 1.2 1 0.8 0.6 Enable OFF 0.4 0 2.7 3.2 3.7 4.2 4.7 5.2 5.7 10000 1000 100 INPUT VOLTAGE (V) 1 100 Turn OFF VOUT = 3.6V 0 20 40 60 80 100 120 TEMPERATURE (%) SW Frequency vs. Temperature 6 5.5 10 IOUT = 150mA 0.4 -40 -20 VOUT Rise Time vs. CSS COUT = 4.7µF 0.2 0.6 0 20 40 60 80 100 120 TEMPERATURE (°C) 100000 1.4 1 0.8 0 1000000 Turn ON 1.2 2.46 Enable Voltage vs. Input Voltage 1.8 1.4 0.2 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 1.6 2.47 SW FREQUENCY (MHz) UVLO THRESHOLD (V) FB VOLTAGE (V) 0.64 ENABLE VOLTAGE (V) 2 2.56 0.65 Enable Threshold vs. Temperature 5 4.5 4 3.5 3 2.5 2 1.5 VIN = 3.6V 1 0.5 COUT = 4.7µF Load = 400mA 0 1000 10000 100000 1000000 CSS (pF) -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) Switching Frequency vs. Output Current 5 SW FREQUENCY (MHz) 4.5 4 VIN = 3.6V 3.5 VIN = 4.2V 3 2.5 2 1.5 1 0.5 0 0.1 1 10 100 1000 10000 OUTPUT CURRENT (mA) September 2010 5 M9999-092910-A Micrel Inc. MIC33153 Functional Characteristics September 2010 6 M9999-092910-A Micrel Inc. MIC33153 Functional Characteristics (Continued) September 2010 7 M9999-092910-A Micrel Inc. MIC33153 Functional Characteristics (Continued) September 2010 8 M9999-092910-A Micrel Inc. MIC33153 Functional Diagram Figure 1. Simplified MIC33153 Functional Block Diagram – Fixed Output Voltage Figure 2. Simplified MIC33153 Functional Block Diagram – Adjustable Output Voltage September 2010 9 M9999-092910-A Micrel Inc. MIC33153 Functional Description Power Good PG The Power Good (PG) pin is an open drain output which indicates logic high when the output voltage is typically above 92% of its steady state voltage. When the output voltage is below 86%, the PG pin indicates logic low. A pull up resistor of more than 10kΩ should be connected from PG to VOUT. 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 2.2µF bypass capacitor placed close to VIN and the power ground (PGND) pin is required. Refer to the layout recommendations for details. SS The soft start (SS) pin is used to control the output voltage ramp up time. The approximate equation for the ramp time in milliseconds is: 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 0.01µA. MIC33153 features external soft start circuitry via the soft start (SS) pin that reduces in rush current and prevents the output voltage from overshooting at start up. Do not leave the EN pin floating. T(ms) = 270x103 x ln (10) x CSS where: T is the time in milliseconds and CSS is the external soft start capacitance (in Farads). For example, for a CSS = 470pF, Trise ~ 0.3ms or 300µs. See the Typical Characteristics curve for a graphical guide. The minimum recommended value for CSS is 100pF. 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. FB The feedback (FB) pin is provided for the adjustable voltage option (no internal connection for fixed options). This is the control input for programming the output voltage. A resistor divider network is connected to this pin from the output and is compared to the internal 0.62V reference within the regulation loop. The output voltage can be programmed between 0.65V and 3.6V using the following equation: 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. ⎛ R1 ⎞ VOUT = VREF × ⎜1+ ⎟ ⎝ R2 ⎠ AGND 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. where: R1 is the top resistor, R2 is the bottom resistor. PGND 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. September 2010 Example feedback resistor values: 10 VOUT R1 R2 1.2V 274k 294k 1.5V 316k 221k 1.8V 301k 158k 2.5V 324k 107k 3.3V 309k 71.5k M9999-092910-A Micrel Inc. MIC33153 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. Application Information The MIC33153 is a high performance DC-to-DC step down regulator offering a small solution size. With the HyperLight Load™ switching scheme, the MIC33153 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 2.2µF ceramic capacitor or greater should be placed close to the VIN pin and PGND pin for bypassing. A Murata GRM188R60J475ME84D, size 0603, 4.7µF 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 MIC33153 is designed for use with a 2.2µF or greater ceramic output capacitor. Increasing the output capacitance will lower output ripple and improve load transient response but could also increase solution size or cost. A low equivalent series resistance (ESR) ceramic output capacitor such as the Murata GRM188R60J475ME84D, size 0603, 4.7µF 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. Compensation The MIC33153 is designed to be stable with a 4.7µF ceramic (X5R) output capacitor. Figure 3. Efficiency Under Load Duty Cycle The typical maximum duty cycle of the MIC33153 is 80%. Figure 3 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 Load™ mode, the MIC33153 is able to maintain high efficiency at low output currents. Efficiency Considerations Efficiency is defined as the amount of useful output power, divided by the amount of power supplied: ⎛V ×I Efficiency % = ⎜⎜ OUT OUT ⎝ VIN × IIN September 2010 ⎞ ⎟⎟ × 100 ⎠ 11 M9999-092910-A Micrel Inc. MIC33153 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. The DCR losses can be calculated as follows: HyperLight Load™ Mode MIC33153 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 minimum off 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 MIC33153 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 MIC33153 during light load currents by only switching when it is needed. As the load current increases, the MIC33153 goes into continuous conduction mode (CCM) and switches at a frequency centered at 4MHz. The equation to calculate the load when the MIC33153 goes into continuous conduction mode may be approximated by the following formula: PDCR = IOUT2 x DCR From that, the loss in efficiency due to inductor resistance can be calculated as follows: ⎡ ⎛ VOUT × IOUT Efficiency Loss = ⎢1− ⎜⎜ ⎢⎣ ⎝ VOUT × IOUT + PDCR ⎞⎤ ⎟⎥ × 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. The effect of MOSFET voltage drops and DCR losses in conjunction with the maximum duty cycle combine to limit maximum output voltage for a given input voltage. The following graph shows this relationship based on the typical resistive losses in the MIC33153: ⎛ (V − VOUT ) × D ⎞ ⎟⎟ ILOAD > ⎜⎜ IN 2L × f ⎝ ⎠ As shown in the above equation, the load at which MIC33153 transitions from HyperLight Load™ mode to PWM mode is a function of the input voltage (VIN), output voltage (VOUT), duty cycle (D), inductance (L) and frequency (f). For example, if VIN = 3.6V, VOUT=1.8V, D=0.5, f=4MHz and the internal inductance of MIC33153 is 0.47μH, then the device will enter HyperLight Load™ mode or PWM mode at approximately 200mA. VOUTMAX vs. VIN 5 100mA OUTPUT VOLTAGE (V) 4.5 4 400mA 3.5 3 1.2A 2.5 2 800mA 1.5 1 0.5 0 2.5 3 3.5 4 4.5 5 5.5 INPUT VOLTAGE (V) September 2010 12 M9999-092910-A Micrel Inc. MIC33153 As can be seen in the diagram, total thermal resistance RθJA = RθJC + RθCA. Hence this can also be written: Power Dissipation Considerations As with all power devices, the ultimate current rating of the output is limited by the thermal properties of the package and the PCB it is mounted on. There is a simple, Ohm’s law type of relationship between thermal resistance, power dissipation and temperature which is analogous to an electrical circuit: TJ = PDISS × (Rθ JA ) + TAMB Since effectively all of the power loss in the converter is dissipated within the MIC33153 package, PDISS can be calculated thus: 1 PDISS = POUT × ( − 1) η Where: η = Efficiency taken from efficiency curves RθJC and RθJA are found in the operating ratings section of the datasheet. Example: A MIC33153 is intended to drive a 1A load at 1.8V and is placed on a printed circuit board which has a ground plane area of at least 25mm square. The voltage source is a Li-ion battery with a lower operating threshold of 3V and the ambient temperature of the assembly can be up to 50ºC. Summary of variables: IOUT = 1A VOUT = 1.8V VIN = 3V to 4.2V TAMB = 50ºC From this simple circuit, one can calculate VX if one knows ISOURCE, VZ and the resistor values, RXY and RYZ using the equation: V X = ISOURCE × (R XY + R YZ ) + VZ Thermal circuits can be considered using these same rules and can be drawn similarly replacing current sources with power dissipation (in Watts), resistance with thermal resistance (in ºC/W) and voltage sources with temperature (in ºC): RθJA = 55ºC/W from Datasheet η @ 1A = 80% (worst case with VIN=4.2V from the Typical Characteristics Efficiency vs. Load graphs) PDISS = 1.8 ⋅ 1× ( 1 − 1) = 0.45W 0.80 The worst case switch and inductor resistance will increase at higher temperatures, so a margin of 20% can be added to account for this: Now replacing the variables in the equation for VX, one can find the junction temperature (TJ) from power dissipation, ambient temperature and the known thermal resistance of the PCB (RθCA) and the package (RθJC): PDISS = 0.45 x 1.2 = .54W TJ = PDISS × (RθJC + RθCA ) + TAMB Therefore: TJ = 0.54W x (55 ºC/W) + 50ºC TJ = 79.7ºC This is well below the maximum 125ºC. September 2010 13 M9999-092910-A Micrel Inc. MIC33153 Typical Application Circuit (Fixed Output) Bill of Materials Item C1, C2 C3 R3, R4 U1 Part Number C1608X5R0J475K GRM188R60J475KE19D C1608NPO0J471K CRCW06031002FKEA MIC33153-xYHJ Manufacturer TDK(1) Murata(2) TDK(1) (3) Vishay (4) Micrel, Inc. Description Qty. Ceramic Capacitor, 4.7µF, 6.3V, X5R, Size 0603 2 Ceramic Capacitor, 470pF, 6.3V, NPO, Size 0603 1 Resistor, 10k, Size 0603 2 4MHz 1.2A Buck Regulator with HyperLight Load™ Mode and Fixed Output Voltage 1 Notes: 1. TDK: www.tdk.com. 2. Murata: www.murata.com. 3. Vishay: www.vishay.com. 4. Micrel, Inc.: www.micrel.com. September 2010 14 M9999-092910-A Micrel Inc. MIC33153 Typical Application Circuit (Adjustable Output) Bill of Materials Item C1, C2 C3 Part Number C1608X5R0J475K GRM188R60J475KE19D C1608NPO0J471K − C4 Manufacturer TDK(1) (2) Murata TDK(1) − Description Qty. Ceramic Capacitor, 4.7µF, 6.3V, X5R, Size 0603 2 Ceramic Capacitor, 470pF, 6.3V, NPO, Size 0603 1 Not Fitted (NF) 0 (3) R1 CRCW06033013FKEA Vishay Resistor, 301k, Size 0603 1 R2 CRCW06031583FKEA Vishay(3) Resistor, 158k, Size 0603 1 R3, R4 CRCW06031002FKEA (3) Resistor, 10k, Size 0603 2 U1 MIC33153-YHJ 4MHz 1.2A Buck Regulator with HyperLight Load™ Mode and Adjustable Output Voltage 1 Vishay Micrel, Inc.(4) 1. TDK: www.tdk.com. 2. Murata : www.murata.com. 3. Vishay: www.vishay.com. 4. Micrel, Inc.: www.micrel.com. September 2010 15 M9999-092910-A Micrel Inc. MIC33153 PCB Layout Recommendations Top Layer Bottom Layer September 2010 16 M9999-092910-A Micrel Inc. MIC33153 Package Information 14-Pin 3.0mm x 3.5mm MLF® (HJ) 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. © 2010 Micrel, Incorporated. September 2010 17 M9999-092910-A