MIC2875 4.8A ISW, Synchronous Boost Regulator with Bi-Directional Load Disconnect General Description Features The MIC2875 is a compact and highly-efficient 2MHz synchronous boost regulator with a 4.8A switch. It features a bi-directional load disconnect function which prevents any leakage current between the input and output when the device is disabled. The MIC2875 operates in bypass mode automatically when the input voltage is greater than the target output voltage. At light loads, the boost converter goes to the PFM mode to improve the efficiency. • Input voltage range: 2.5V to 5.5V • Fully-integrated, high-efficiency, 2MHz synchronous boost regulator • Bi-directional true load disconnect • Integrated anti-ringing switch • Minimum switching frequency of 45kHz • Up to 95% efficiency • <1µA shutdown current • Bypass mode for VIN ≥ VOUT • Overcurrent protection and thermal shutdown • Fixed and adjustable output versions • 8-pin 2mm × 2mm TDFN package To minimize switching artifacts in the audio band, the MIC2875 is designed to operate with a minimum switching frequency of 45kHz. The MIC2875 also features an integrated anti-ringing switch to minimize EMI. The MIC2875 is available in a 8-pin 2mm × 2mm Thin DFN (TDFN) package, with a junction temperature range of −40°C to +125°C. Datasheets and support documentation are available on Micrel’s web site at: www.micrel.com. Applications • • • • • Tablet and smartphones USB OTG and HDMI hosts Portable power reserve supplies Low-noise audio applications Portable equipment Simplified Application Schematics MIC2875 (Adjustable Output) MIC2875 (Fixed Output) Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com January 19, 2015 Revision 1.1 Micrel, Inc. MIC2875 Ordering Information Mark Code Output Voltage Temperature Range Package(1, 2) MIC2875-4.75YMT 87F 4.75V −40°C to +125°C 8-Pin 2mm × 2mm TDFN MIC2875-5.0YMT 87G 5.00V −40°C to +125°C 8-Pin 2mm × 2mm TDFN MIC2875-5.25YMT 87H 5.25V −40°C to +125°C 8-Pin 2mm × 2mm TDFN MIC2875-5.5YMT 87J 5.50V −40°C to +125°C 8-Pin 2mm × 2mm TDFN MIC2875-AYMT 87A Adjustable −40°C to +125°C 8-Pin 2mm × 2mm TDFN Part Number Notes: 1. TDFN is a RoHS-compliant package. Lead finish is Pb free and Matte Tin. Mold compound is Halogen free. 2. ▲ = TDFN Pin 1 identifier. Pin Configuration 8-Pin 2mm × 2mm TDFN (MT) Fixed Output (Top View) 8-Pin 2mm × 2mm TDFN (MT) Adjustable Output (Top View) Pin Description Pin Number Fixed Output Pin Number Adjustable Output Pin Name 1 1 SW 2 2 PGND 3 3 IN 4 4 AGND Analog Ground: The analog ground for the regulator control loop. 5 − OUTS Output Voltage Sense Pin: For output voltage regulation in fixed voltage version. Connect to the boost converter output. − 5 FB Feedback Pin: For output voltage regulation in adjustable voltage version. Connect to the feedback resistor divider. 6 6 EN Boost Converter Enable: When this pin is driven low, the IC enters shutdown mode. The EN pin has an internal 2.5MΩ pull-down resistor. The output is disabled when this pin is left floating. January 19, 2015 Pin Function Boost Converter Switch Node: Connect the inductor between IN and SW pins. Power Ground: The power ground for the synchronous boost DC-to-DC converter power stage. Supply Input: Connect at least 1µF ceramic capacitor between IN and AGND pins. 2 Revision 1.1 Micrel, Inc. MIC2875 Pin Description (Continued) Pin Number Fixed Output Pin Number Adjustable Output Pin Name Pin Function 7 7 /PG Open Drain Power Good Output (Active Low): The /PG pin is high impedance when the output voltage is below the power good threshold, and becomes low once the output is above the power good threshold. The /PG pin has a typical RDS(ON) = 90Ω and requires a pull up resistor of 1MΩ. Connect /PG pin to AGND when the /PG signal is not used. 8 8 OUT Boost Converter Output. EP EP ePad Exposed Heat Sink Pad. Connect to AGND for best thermal performance. January 19, 2015 3 Revision 1.1 Micrel, Inc. MIC2875 Absolute Maximum Ratings(3) Operating Ratings(4) IN, EN, OUT, FB, /PG to PGND ...................... −0.3V to +6V AGND to PGND. .......................................... −0.3V to +0.3V Power Dissipation .................................. Internally Limited(5) Lead Temperature (soldering, 10s) ............................ 260°C Storage Temperature (TS) ......................... −65°C to +150°C ESD Rating(6) Human Body Model .............................................. 1.5kV Machine Model ...................................................... 200V Supply Voltage (VIN) ..................................... +2.5V to +5.5V Output Voltage (VOUT) ......................................... Up to 5.5V Enable Voltage (VEN) .............................................. 0V to VIN Junction Temperature (TJ) ........................ –40°C to +125°C Package Thermal Resistance 8-Pin 2mm × 2mm TDFN (θJA) .......................... 90°C/W Electrical Characteristics(7) VIN = 3.6V, VOUT = 5V, CIN = 4.7µF, COUT = 22µF, L = 1µH TA = 25°C, bold values indicate −40°C ≤ TJ ≤ +125°C, unless otherwise noted. Symbol Parameter Condition Min. Typ. Max. Unit 5.5 V 2.49 V Power Supply 2.5 VIN Supply Voltage Range VUVLOR UVLO Rising Threshold 2.32 VUVLOH UVLO Hysteresis 200 mV IVIN Quiescent Current Operating at minimum switching frequency 1 mA IVINSD VIN Shutdown Current VEN = 0V, VIN = 5.5V, VOUT = 0V 1 3 µA IVOUTSD VOUT Shutdown Current VEN = 0V, VIN = 0.3V, VOUT = 5.5V 2 5 µA VOUT Output Voltage 5.5 V VFB Feedback Voltage Adjustable version, IOUT = 0A 0.9135 V Voltage Accuracy Fixed version, IOUT = 0A +1.5 % Line Regulation 2.5V < VIN < 4.5V, IOUT = 500mA 0.3 %/V Load Regulation IOUT = 200mA to 1200mA 0.2 %/A 92 % 6.5 % DMAX Maximum Duty Cycle DMIN Minimum Duty Cycle ILS PMOS NMOS Low-Side Switch Current Limit VIN (8) Switch On-Resistance 0.8865 −1.5 3.8 VIN = 2.5V 0.9 4.8 VIN = 3.0V, ISW = 200mA, VOUT = 5.0V 79 VIN = 3.0V, ISW = 200mA, VOUT = 5.0V 82 ISW Switch Leakage Current(8) VEN = 0V, VIN = 5.5V 0.2 FSWMIN Minimum Switching Frequency IOUT = 0mA 45 FOSC Oscillator Frequency TSD 1.6 2 Overtemperature Shutdown Threshold 155 Overtemperature Shutdown Hysteresis 15 5.8 A mΩ 5 µA kHz 2.4 MHz °C Notes: 3. Exceeding the absolute maximum ratings may damage the device. 4. The device is not guaranteed to function outside its operating ratings. 5. The maximum allowable power dissipation of any TA (ambient temperature) is PD(max) = (TJ(max) – TA) / θJA. Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown 6. Devices are ESD sensitive. Handling precautions are recommended. Human body model, 1.5kΩ in series with 100pF. 7. Specification for packaged product only. 8. Guaranteed by design and characterization. January 19, 2015 4 Revision 1.1 Micrel, Inc. MIC2875 Electrical Characteristics(7) (Continued) VIN = 3.6V, VOUT = 5V, CIN = 4.7µF, COUT = 22µF, L = 1µH TA = 25°C, bold values indicate −40°C ≤ TJ ≤ +125°C, unless otherwise noted. Symbol Parameter Condition Min. Typ. Max. Unit Soft-Start TSS Soft-Start Time VOUT = 5.0V 1.1 ms EN, /PG Control Pins VEN EN Threshold Voltage EN Pin Current Boost converter and chip logic ON 1.5 0.4 Boost converter and chip logic OFF VIN = VEN = 3.6V 1.5 3 V µA V/PG-THR Power-Good Thershold (Rising) 0.90 × VOUT V V/PG-THF Power-Good Thershold (Falling) 0.83 × VOUT V January 19, 2015 5 Revision 1.1 Micrel, Inc. MIC2875 Typical Characteristics Efficiency vs. Load Current 5.10 OUTPUT VOLTAGE (V) VIN = 3.6V 80 VIN = 3.0V VIN = 2.5V 70 60 VOUT = 5.0V L = 1µH COUT = 22µF 50 0.001 5.00 TA = 125℃ 4.95 TA = 25℃ 0.010 0.100 1.000 0.0 TA = -40℃ 0.5 1.0 1.5 2.5 2.0 3.0 3.5 4.0 4.5 Oscillator Frequency vs. Temperature Output Shutdown Current vs. Temperature Feedback Voltage vs. Temperature 0 3.50 FEEDBACK VOLTAGE (V) SHUTDOWN CURRENT (µA) 25 50 75 100 125 3.00 2.50 2.00 ADJUSTABLE R2 = 910kΩ R3 = 200kΩ 1.50 -25 0 25 50 75 100 TEMPERATURE (℃) TEMPERATURE (℃) UVLO Threshold vs. Temperature Enable Threshold vs. Temperature ENABLE THRESHOLDVOLTAGE (V) 2.40 RISING 2.30 2.20 2.10 FALLING 2.00 125 25 50 75 100 TEMPERATURE (℃) January 19, 2015 125 150 0.900 0.898 150 ADJUSTABLE VOUT = 5.0V R2 = 910kΩ R3 = 200kΩ -50 -25 0 25 50 75 100 125 150 TEMPERATURE (℃) Power Good Threshold vs. Temperature 4.80 1.20 RISING 1.00 0.80 FALLING RISING 4.60 ADJUSTABLE R2 = 910kΩ R3 = 200kΩ VOUT = 5.0V 4.40 4.20 FALLING 4.00 3.80 0.60 0 0.902 0.896 -50 150 5.0 0.904 VEN = 0V VIN = 0.3V VOUT = 5.5V 1.00 1.96 -25 TA = 25℃ ADJUSTABLE R2 = 910kΩ R3 = 200kΩ INPUT VOLTAGE(V) VIN = 3.6V VOUT = 5.0V L = 1µH COUT = 22µF IOUT = 0A -50 TA = 125℃ 4.90 LOAD CURRENT (A) 2.00 -25 5.00 LOAD CURRENT (A) 2.02 -50 5.10 4.80 4.90 4.00 1.98 VOUT = 5.0V L = 1µH COUT = 22µF IOUT = 500mA TA = -40℃ 2.04 OSCILLATOR FREQUENCY (MHz) 5.05 /PG THRESHOLD VOLTAGE (V) EFFICIENCY (%) 90 5.20 ADJUSTABLE R2 = 910kΩ R3 = 200kΩ VIN = 3.5V VOUT = 5.0V L = 1µH COUT = 22µF OUTPUT VOLTAGE (V) 100 INPUT VOLTAGE (V) Output Voltage vs. Input Voltage Output Voltage vs. Load Current -50 -25 0 25 50 75 100 TEMPERATURE (℃) 6 125 150 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (℃) Revision 1.1 Micrel, Inc. MIC2875 Functional Characteristics January 19, 2015 7 Revision 1.1 Micrel, Inc. MIC2875 Functional Characteristics (Continued) January 19, 2015 8 Revision 1.1 Micrel, Inc. MIC2875 Functional Characteristics (Continued) January 19, 2015 9 Revision 1.1 Micrel, Inc. MIC2875 Functional Diagram Simplified Adjustable Output Simplified Fixed Output January 19, 2015 10 Revision 1.1 Micrel, Inc. MIC2875 Functional Description Feedback/Output Voltage Sense (FB/OUTS) Feedback or output voltage sense pin for the boost converter. For the fixed voltage version, this pin should be connected to the OUT pin. For the adjustable version, connect a resistor divider to set the output voltage (see “Output Voltage Programming” for more information). Input (IN) The input supply provides power to the internal MOSFETs gate drivers and control circuitry for the boost regulator. The operating input voltage range is from 2.5V to 5.5V. A 1µF low-ESR ceramic input capacitor should be connected from IN to AGND as close to MIC2875 as possible to ensure a clean supply voltage for the device. A minimum voltage rating of 10V is recommended for the input capacitor. Power-Good Output (/PG) The open-drain active-low power-good output (/PG) is low when the output voltage is above the power-good threshold. A pull-up resistor of 1MΩ is recommended. Switch Node (SW) The MIC2875 has internal low-side and synchronous MOSFET switches. The switch node (SW) between the internal MOSFET switches 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 input supply voltage. Due to the highspeed switching on this pin, the switch node should be routed away from sensitive nodes wherever possible. Exposed Heat Sink Pad (EP) The exposed heat sink pad, or ePad (EP), should be connected to AGND for best thermal performance. Ground Path (AGND) The ground path (AGND) is for the internal biasing and control circuitry. AGND should be connected to the PCB pad for the package exposed pad. The current loop of the analog ground should be separated from that of the power ground (PGND). AGND should be connected to PGND and EP at a single point. Power Ground (PGND) The power ground (PGND) is the ground path for the high current in the boost switches. The current loop for the power ground should be as short as possible and separate from the AGND loop as applicable. Boost Converter Output (OUT) A low-ESR ceramic capacitor of 22µF (for operation with VIN ≤ 5.0V), or 66µF (for operation with VIN > 5.0V) should be connected from VOUT to PGND as close as possible to the MIC2875. A minimum voltage rating of 10V is recommended for the output capacitor. Enable (EN) Enable pin of the MIC2875. A logic high on this pin enables the MIC2875. When this pin is driven low, the MIC2875 enters the shutdown mode. When the EN pin is left floating, it is pulled-down internally by a built-in 2.5MΩ resistor. January 19, 2015 11 Revision 1.1 Micrel, Inc. MIC2875 Application Information General Description The MIC2875 is a 2MHz, current-mode, PWM, synchronous boost converter with an operating input voltage range of 2.5V to 5.5V. At light load, the converter enters pulse-skipping mode to maintain high efficiency over a wide range of load current. The maximum peak current in the boost switch is limited to 4.8A (typical). Automatic Bypass Mode (when VIN > VOUT) The MIC2875 automatically operates in bypass mode when the input voltage is higher than the target output voltage. In bypass mode, the NMOS is turned off while the PMOS is fully turned-on to provide a very low impedance path from IN to OUT. Soft-Start The MIC2875 integrates an internal soft-start circuit to limit the inrush current during start-up. When the device is enabled, the PMOS is turned-on slowly to charge the output capacitor to a voltage close to the input voltage. Then, the device begins boost switching cycles to gradually charge up the output voltage to the target VOUT. Bi-Directional Output Disconnect The power stage of the MIC2875 consists of a NMOS transistor as the main switch and a PMOS transistor as the synchronous rectifier. A control circuit turns off the back gate diode of the PMOS to isolate the output from the input supply when the chip is disabled (VEN = 0V). An “always on” maximum supply selector switches the cathode of the back gate diode to either the IN or the OUT (whichever of the two has the higher voltage). As a result, the output of the MIC2875 is bi-directionally isolated from the input as long as the device is disabled. The maximum supply selector and hence the output disconnect function requires only 0.3V at the IN pin to operate. Output Voltage Programming The MIC2875 has an adjustable version that allows the output voltage to be set by an external resistor divider R2 and R3. The typical feedback voltage is 900mV, the recommended maximum and minimum output voltage is 5.5V and 3.2V, respectively. The current through the resistor divider should be significantly larger than the current into the FB pin (typically 0.01µA). It is recommended that the total resistance of R2 + R3 should be around 1MΩ. The appropriate R2 and R3 values for the desired output voltage are calculated as in Equation 1: Minimum Switching Frequency When the MIC2875 enters the pulse-skipping mode for more than 20µs, an internal control circuitry forces the PMOS to turn on briefly to discharge VOUT to VIN through the inductor. When the inductor current reaches a predetermined threshold, the PMOS is turned off and the NMOS is turned on so that the inductor current can decrease gradually. Once the inductor current reaches zero, the NMOS is eventually turned off. The above cycle repeats if there is no switching activity for another 20µs, effectively maintaining a minimum switching frequency of 45 kHz. The frequency control circuit is disabled when VOUT is less than or within 200mV of VIN. This minimum switching frequency feature is advantageous for applications that are sensitive to low-frequency EMI, such as audio systems. V R 2 = R3 × OUT − 1 0 . 9 V Eq. 1 Integrated Anti-Ringing Switch The MIC2875 includes an anti-ringing switch that eliminates the ringing on the SW node of a conventional boost converter operating in the discontinuous conduction mode (DCM). At the end of a switching cycle during DCM operation, both the NMOS and PMOS are turned off. The anti-ringing switch in the MIC2875 clamps the SW pin voltage to IN to dissipate the remaining energy stored in the inductor and the parasitic elements of the power switches. January 19, 2015 12 Revision 1.1 Micrel, Inc. MIC2875 Component Selection Inductor Inductor selection is a trade-off between efficiency, stability, cost, size, and rated current. Since the boost converter is compensated internally, the recommended inductance is limited from 1µH to 2.2µH to ensure system stability and presents a good balance between these considerations. The Y5V and Z5U type temperature rating ceramic capacitors are not recommended due to their large reduction in capacitance over temperature and increased resistance at high frequencies. These reduce their ability to filter out high-frequency noise. The rated voltage of the input capacitor should be at least 20% higher than the maximum operating input voltage over the operating temperature range. A large inductance value reduces the peak-to-peak inductor ripple current hence the output ripple voltage. This also reduces both the DC loss and the transition loss at the same inductor’s DC resistance (DCR). However, the DCR of an inductor usually increases with the inductance in the same package size. This is due to the longer windings required for an increase in inductance. Since the majority of the input current passes through the inductor, the higher the DCR the lower the efficiency is, and more significantly at higher load currents. On the other hand, inductor with smaller DCR but the same inductance usually has a larger size. The saturation current rating of the selected inductor must be higher than the maximum peak inductor current to be encountered and should be at least 20% to 30% higher than the average inductor current at maximum output current. Output Capacitor Output capacitor selection is also a trade-off between performance, size, and cost. Increasing output capacitor will lead to an improved transient response, however, the size and cost also increase. For operation with VIN ≤ 5.0V, a minimum of 22µF output capacitor with ESR less than 10mΩ is required. For operation with VIN > 5.0V, a minimum of 66µF output capacitor with ESR less than 10mΩ is required. X5R or X7R type ceramic capacitors are recommended for better tolerance over temperature. Additional capacitors can be added to improve the transient response, and to reduce the ripple of the output when the MIC2875 operates in and out of bypass mode. The Y5V and Z5U type ceramic capacitors are not recommended due to their wide variation in capacitance over temperature and increased resistance at high frequencies. The rated voltage of the output capacitor should be at least 20% higher than the maximum operating output voltage over the operating temperature range. 0805 size ceramic capacitor is recommended for smaller ESL at output capacitor which contributes smaller voltage spike at the output voltage of high-frequency switching boost converter. Input Capacitor to the Device Supply A ceramic capacitor of 1µF or larger with low ESR is recommended to reduce the input voltage ripple to ensure a clean supply voltage for the device. The input capacitor should be placed as close as possible to the MIC2875 IN pin and AGND pin with short traces to ensure good noise performance. X5R or X7R type ceramic capacitors are recommended for better tolerance over temperature. The Y5V and Z5U type temperature rating ceramic capacitors are not recommended due to their large reduction in capacitance over temperature and increased resistance at high frequencies. The use of these reduces the ability to filter out high-frequency noise. The rated voltage of the input capacitor should be at least 20% higher than the maximum operating input voltage over the operating temperature range. Input Capacitor to the Power Path A ceramic capacitor of a 4.7µF of larger with low ESR is recommended to reduce the input voltage fluctuation at the voltage supply of the high current power path. An input capacitor should be placed close to the VIN supply to the power inductor and PGND for good device performance at heavy load condition. X5R or X7R type ceramic capacitors are recommended for better tolerance overtemperature. January 19, 2015 13 Revision 1.1 Micrel, Inc. MIC2875 Power Dissipation As with all power devices, the ultimate current rating of the output is limited by the thermal properties of the device package and the PCB on which the device is mounted. There is a simple, Ohm’s law-type relationship between thermal resistance, power dissipation, and temperature which are analogous to an electrical circuit (Figure 1): Now replacing the variables in the equation for VX, we can find the junction temperature (TJ) from the power dissipation, ambient temperature and the known thermal resistance of the PCB (θCA) and the package (θJC). TJ = PDISS × (θJC + θCA) + TA Eq. 3 As can be seen in the diagram, total thermal resistance θJA = θJC + θCA. This can also be written as in Equation 4: TJ + PDISS × (θJA) + TA Eq. 4 Given that all of the power losses (minus the inductor losses) are effectively in the converter are dissipated within the MIC2875 package, PDISS can be calculated thusly: Figure 1. Series Electrical Resistance Circuit From this simple circuit we can calculate VX if we know ISOURCE, VZ and the resistor values, RXY and RYZ using Equation 2: 1 Linear Mode: PDISS = POUT × − 1 − IOUT 2 × DCR η Eq. 5 VX = ISOURCE × (RXY + RYZ) + VZ Eq. 2 PDISS = POUT Boost Mode: Thermal circuits can be considered using this same rule and can be drawn similarly by replacing current sources with power dissipation (in watts), resistance with thermal resistance (in °C/W) and voltage sources with temperature (in °C). 2 1 I × − 1 − OUT × DCR η 1 − D Eq. 6 V − VIN Duty Cycle (Boost Mode): D + OUT VOUT Eq. 7 where: η = Efficiency taken from efficiency curves and DCR = inductor DCR. θJC and θJA are found in the operating ratings section of the datasheet. Figure 2. Series Thermal Resistance Circuit January 19, 2015 14 Revision 1.1 Micrel, Inc. MIC2875 Where the real board area differs from 1” square, θCA (the PCB thermal resistance), values for various PCB copper areas can be taken from Figure 3. (Note: Figure 3 taken from Designing with Low Dropout Voltage Regulators available from Micrel’s web site at: www.micrel.com.) Figure 3. Determining PC Board Area for a Given PCB Thermal Resistance Figure 3 shows the total area of a round or square pad, centered on the device. The solid trace represents the area of a square, single-sided, horizontal, solder-masked, copper PC board trace heat sink, measured in square millimeters. No airflow is assumed. The dashed line shows PC boards trace heat sink covered in black oil-based paint and with 1.3m/sec (250 feet per minute) airflow. This approaches a “best case” pad heat sink. Conservative design dictates using the solid trace data, which indicates that a maximum pad size of 5000 mm2 is needed. This is a pad 71mm × 71mm (2.8 inches per side). January 19, 2015 15 Revision 1.1 Micrel, Inc. MIC2875 PCB Layout Guidelines Output Capacitor PCB layout is critical to achieve reliable, stable and efficient performance. A ground plane is required to control EMI and minimize the inductance in power, signal and return paths. The following guidelines should be followed to ensure proper operation of the device: • Use wide and short traces to connect the output capacitor as close as possible to the OUT and PGND pins without going through via holes to minimize the switching current loop during the main switch off cycle and the switching noise. • Use either X5R or X7R temperature rating ceramic capacitors. Do not use Y5V or Z5U type ceramic capacitors. IC (Integrated Circuit) • Place the IC close to the point-of-load. • Use fat traces to route the input and output power lines. • Analog grounds and power ground should be kept separate and connected at a single location at the PCB pad for exposed pad of the IC. • Place as much as thermal vias on the PCB pad for exposed pad and connected it to the ground plane to ensure a good PCB thermal resistance can be achieved. IN Decoupling Capacitor • The IN decoupling capacitor must be placed close to the IN pin of the IC and preferably connected directly to the pin and not through any via. The capacitor must be located right at the IC. • The IN decoupling capacitor should be connected as close as possible to AGND. • The IN terminal is noise sensitive and the placement of capacitor is very critical. Figure 4. Suggested PCB Routing VIN Power Path Bulk Capacitor • The VIN power path bulk capacitor should be placed and connected close to the VIN supply to the power inductor and the PGND of the IC. • Use either X5R or X7R temperature rating ceramic capacitors. Do not use Y5V or Z5U type ceramic capacitors. Inductor • Keep both the inductor connections to the switch node (SW) and input power line short and wide enough to handle the switching current. Keep the areas of the switching current loops small to minimize the EMI problem. • Do not route any digital lines underneath or close to the inductor. • Keep the switch node (SW) away from the noise sensitive pins. • To minimize noise, place a ground plane underneath the inductor. January 19, 2015 16 Revision 1.1 Micrel, Inc. MIC2875 Typical Application Schematics MIC2875-AYMT Typical Application Schematic − VIN ≤ 5.0V MIC2875-5.0YMT Typical Application Schematic − VIN ≤ 5.0V MIC2875-AYMT Typical Application Schematic − VIN > 5.0V MIC2875-5.0YMT Typical Application Schematic − VIN > 5.0V January 19, 2015 17 Revision 1.1 Micrel, Inc. MIC2875 Bill of Materials Item Part Number C1 C1608X5R1A475K080AC C2 LMK212BJ226MG-T C3 L1 R1 GRM188R61A105KA61J PIMB042T-1R0MS-39 ERJ-3GEYJ105V Manufacturer (9) TDK Taiyo Yuden(10) Description Qty. Capacitor 4.7μF, 10V, 10%, X5R, 0603 1 Capacitor 22μF, 10V, 20%, X5R, 0805 (VIN ≤ 5.00V) 1 Capacitor 22μF, 10V, 20%, X5R, 0805 (VIN > 5.00V, in parallel) 3 (11) Capacitor 1μF, 10V, 10%, X5R, 0603 1 (12) Inductor 1μH, 4.5A, SMD, 4.2mm × 4.0mm × 1.8mm 1 Resistor 1MΩ, 5%, 0603 1 Resistor 910kΩ, 0.1%, 0603 1 Murata Cyntec Panasonic (13) (14) R2 1-1879417-8 TE R3 ERA-3AEB204V Panasonic Resistor 200kΩ, 0.1%, 0603 1 R4 ERJ-3GEYJ103V Panasonic Resistor 10kΩ, 5%, 0603 1 UI MIC2875-xxxYMT Micrel, Inc.(15) 4.8A ISW, Synchronous Boost Regulator with Bi-Directional Load Disconnect 1 Notes: 9. TDK: www.tdk.com. 10. Taiyo Yuden: www.t-yuden.com. 11. Murata: www.murata.com. 12. Cyntec: www.cyntec.com. 13. Panasonic: www.panasonic.com. 14. TE: www.te.com. 15. Micrel, Inc.: www.micrel.com. January 19, 2015 18 Revision 1.1 Micrel, Inc. MIC2875 PCB Layout Recommendations Top Layer Bottom Layer January 19, 2015 19 Revision 1.1 Micrel, Inc. MIC2875 Package Information and Recommended Landing Pattern(16) 8-Pin 2mm × 2mm TDFN (MT) Note: 16. Package information is correct as of the publication date. For updates and most current information, go to www.micrel.com. January 19, 2015 20 Revision 1.1 Micrel, Inc. MIC2875 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, Inc. is a leading global manufacturer of IC solutions for the worldwide high-performance linear and power, LAN, and timing & communications markets. The Company’s products include advanced mixed-signal, analog & power semiconductors; high-performance communication, clock management, MEMs-based clock oscillators & crystal-less clock generators, Ethernet switches, and physical layer transceiver ICs. Company customers include leading manufacturers of enterprise, consumer, industrial, mobile, telecommunications, automotive, and computer products. Corporation headquarters and state-of-the-art wafer fabrication facilities are located in San Jose, CA, with regional sales and support offices and advanced technology design centers situated throughout the Americas, Europe, and Asia. Additionally, the Company maintains an extensive network of distributors and reps worldwide. Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this datasheet. 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. © 2014 Micrel, Incorporated. January 19, 2015 21 Revision 1.1