MIC23158/9 3MHz PWM Dual 2A Buck Regulator with HyperLight Load and Power Good General Description Features The MIC23158/9 is a high-efficiency, 3MHz, dual, 2A synchronous buck regulator with HyperLight Load mode, power good output indicator, and programmable soft start. The MIC23159 also provides an auto discharge feature that switches in a 225Ω pull down circuit on its output to discharge the output capacitor when disabled. HyperLight Load provides very high efficiency at light loads and ultrafast transient response which makes the MIC23158/9 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 20-pin 3mm x 4mm ® MLF package saves precious board space and requires seven external components for each channel. The MIC23158/9 is designed for use with a very small inductor, down to 0.47µH, and an output capacitor as small as 2.2µF that enables a total solution size, less than 1mm in height. The MIC23158/9 has a very low quiescent current of 45µA and achieves a peak efficiency of 94% in continuous conduction mode. In discontinuous conduction mode, the MIC23158/9 can achieve 83% efficiency at 1mA. The MIC23158/9 is available in a 20-pin 3mm x 4mm 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. • • • • • • • • • • • • • • • • • 2.7V to 5.5V input voltage Adjustable output voltage (down to 1.0V) 2 independent 2A outputs Up to 94% peak efficiency 83% typical efficiency at 1mA 2 independent power good indicators Independent programmable soft start 45µA typical quiescent current 3MHz PWM operation in continuous conduction mode Ultra-fast transient response Fully-integrated MOSFET switches Output pre-bias safe 0.1µA shutdown current Thermal-shutdown and current-limit protection 20-pin 3mm x 4mm MLF package Internal 225Ω pull-down circuit on output (MIC23159) –40°C to +125°C junction temperature range Applications • Solid State Drives (SSD) • Smart phones • Tablet PCs • Mobile handsets • Portable devices (PMP, PND, UMPC, GPS) • WiFi/WiMax/WiBro applications _______________________________________________________________________________________________________ Typical Application HyperLight Load is a registered trademark of Micrel, Inc. MLF and MicroLeadFrame are registered trademarks 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 November 2012 M9999-110812-A Micrel Inc. MIC23158/9 Ordering Information Nominal Output Voltage VOUT1 VOUT2 Output Auto Discharge MIC23158YML ADJ ADJ NO –40°C to +125°C 20-Pin 3mm x 4mm MLF MIC23159YML ADJ ADJ YES –40°C to +125°C 20-Pin 3mm x 4mm MLF Part Number Junction Temperature Range Package Notes: 1. Fixed output voltage options available. Contact Micrel Marketing for details. 2. MLF is a GREEN RoHS-compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free. AVIN1 AGND1 EN1 SNS1 Pin Configuration 20 19 18 17 VIN1 11 16 FB1 PGND1 2 15 PG1 SW1 3 14 SS1 SW2 4 13 SS2 PGND2 5 12 PG2 VIN2 6 11 FB2 7 8 9 10 AVIN2 AGND2 EN2 SNS2 EP 3mm x 4mm MLF (ML) Adjustable Output Voltage (Top View) Pin Description Pin Number (Adjustable) Pin Name 1 VIN1 2 PGND1 3 SW1 Switch (Output): Internal power MOSFET output switches for regulator 1. 4 SW2 Switch (Output): Internal power MOSFET output switches for regulator 2. 5 PGND2 6 VIN2 7 AVIN2 November 2012 Pin Function Power Input Voltage for Regulator 1. Connect a capacitor to ground to decouple noise and switching transients. Power Ground for Regulator 1. Power Ground for Regulator 2. Power Input Voltage for Regulator 2. Connect a capacitor to ground to decouple noise and switching transients. Analog Input Voltage for Regulator 2. Tie to VIN2 and connect a capacitor to ground to decouple noise. 2 M9999-110812-A Micrel Inc. MIC23158/9 Pin Description (Continued) Pin Number (Adjustable) Pin Name 8 AGND2 9 EN2 10 SNS2 Sense Input for Regulator 2. Connect to the output of regulator 2 as close to the output capacitor as possible to accurately sense the output voltage. 11 FB2 Feedback Input for Regulator 2. Connect a resistor divider from the output of regulator 2 to ground to set the output voltage. 12 PG2 Power Good Output for Regulator 2. Open drain output for the power good indicator for output 2. Use a pull-up resistor between this pin and VOUT2 to indicate a power good condition. 13 SS2 Soft-Start for Regulator 2. Connect a minimum of 200pF capacitor to ground to set the turn-on time of regulator 2. Do not leave floating. 14 SS1 Soft-Start for Regulator 1. Connect a minimum of 200pF capacitor to ground to set the turn-on time of regulator 1. Do not leave floating. 15 PG1 Power Good Output for Regulator 1. Open drain output for the power good indicator for output 1. Use a pull-up resistor between this pin and VOUT1 to indicate a power good condition. 16 FB1 Feedback Input for Regulator 1. Connect a resistor divider from the output of regulator 1 to ground to set the output voltage. 17 SNS1 Sense Input for Regulator 1. Connect to the output of regulator 1 as close to the output capacitor as possible to accurately sense the output voltage. 18 EN1 19 AGND1 Analog Ground for Regulator 1. Connect to a central ground point where all high current paths meet (CIN, COUT, PGND1) for best operation. 20 AVIN1 Analog Input Voltage for Regulator 1. Tie to VIN1 and connect a capacitor to ground to decouple noise. EP ePad Exposed Heat Sink Pad. Connect to PGND. November 2012 Pin Function Analog Ground for Regulator 2. Connect to a central ground point where all high current paths meet (CIN, COUT, PGND2) for best operation. Enable Input for Regulator 2. Logic high enables operation of regulator 2. Logic low will shut down regulator 2. Do not leave floating. Enable Input for Regulator 1. Logic high enables operation of regulator 1. Logic low will shut down regulator 1. Do not leave floating. 3 M9999-110812-A Micrel Inc. MIC23158/9 (1) (2) Absolute Maximum Ratings Operating Ratings Supply Voltage (AVIN1, AVIN2, VIN1, VIN2).... −0.3V to 6V Switch1 (VSW1), Sense1 (VSNS1)......................−0.3V to VIN1 Enable1 (VEN1), Power Good1 (VPG1) .............−0.3V to VIN1 Feedback1 (VFB1) ......................................... −-0.3V to VIN1 Switch2 (VSW2), Sense2 (VSNS2)...................... -0.3V to VIN2 Enable2 (VEN2), Power Good2 (VPG2) .............−0.3V to VIN2 Feedback2 (VFB2) ...........................................−0.3V to VIN2 Power Dissipation TA = 70°C .................... Internally Limited Storage Temperature Range .................... −65°C to +150°C Lead Temperature (soldering, 10s) ............................ 260°C (3) ESD Rating ..................................................ESD sensitive Supply Voltage (AVIN1, VIN1) ..................... +2.7V to +5.5V Supply Voltage (AVIN2, VIN2) ..................... +2.7V to +5.5V Enable Input Voltage (VEN1, VEN2) ...................... 0V to VIN1,2 Output Voltage Range (VSNS1, VSNS2) .......... +1.0V to +3.3V Junction Temperature Range (TJ) ...... −40°C ≤ TJ ≤ +125°C Thermal Resistance 3mm x 4mm MLF-20 (θJA) ................................. 53°C/W Electrical Characteristics(4) TA = 25°C; AVIN1,2 = VIN1,2 = VEN1,2 = 3.6V; L1,2 = 1.0µH; COUT1,2 = 4.7µF unless otherwise specified. Bold values indicate –40°C ≤ TJ ≤ +125°C, unless noted. Parameter Condition Min. Undervoltage Lockout Threshold Typ. 2.7 Supply Voltage Range 2.45 Rising Undervoltage Lockout Hysteresis 2.55 Max. Units 5.5 V 2.65 V 75 mV Quiescent Current IOUT = 0mA , SNS > 1.2 * VOUTNOM (both outputs) 45 90 µA Shutdown Current VEN = 0V; VIN = 5.5V (per output) 0.1 5 µA Feedback Regulation Voltage IOUT = 20mA 0.62 0.6355 V Feedback Bias Current (per output) Current Limit SNS = 0.9*VOUTNOM Output Voltage Line Regulation Output Voltage Load Regulation PWM Switch RDSON 0.6045 0.01 µA 4.3 A VIN = 3.6V to 5.5V if VOUTNOM < 2.5V, IOUT = 20mA VIN = 4.5V to 5.5V if VOUTNOM ≥ 2.5V, IOUT = 20mA 0.45 %/V DCM, VIN = 3.6V if VOUTNOM < 2.5V 0.55 DCM, VIN = 5.0V if VOUTNOM ≥ 2.5V 1.0 2.2 CCM, VIN = 3.6V if VOUTNOM < 2.5V CCM, VIN = 5.0V if VOUTNOM ≥ 2.5V ISW1,2 = 100mA PMOS 0.20 ISW1,2 = -100mA NMOS 0.19 Switching Frequency IOUT = 180mA Soft-Start Time VOUT = 90%, CSS = 470pF Soft-Start Current VSS = 0V 0.8 Ω 3 MHz 300 µs 2.7 Power Good Threshold (Rising) 86 Power Good Threshold Hysteresis Power Good Delay Time % Rising Power Good Pull-Down Resistance 92 µA 96 % 7 % 68 µs 95 Ω 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. November 2012 4 M9999-110812-A Micrel Inc. MIC23158/9 Electrical Characteristics(4) (Continued) TA = 25°C; AVIN1,2 = VIN1,2 = VEN1,2 = 3.6V; L1,2 = 1.0µH; COUT1,2 = 4.7µF unless otherwise specified. Bold values indicate –40°C ≤ TJ ≤ +125°C, unless noted. Parameter Condition Min. Enable Input Voltage Typ. Max. 0.4 Logic Low 1.2 Logic High Enable Input Current 0.1 2 Units V µA 225 Ω Overtemperature Shutdown 160 °C Shutdown Hysteresis 20 °C Output Discharge Resistance November 2012 MIC23159 Only; EN = 0V, IOUT = 250µA 5 M9999-110812-A Micrel Inc. MIC23158/9 Typical Characteristics 100 90 90 80 80 VIN = 4.2V 70 VIN = 5V EFFICIENCY (%) EFFICIENCY (%) 100 Efficiency (VOUT = 2.5V) vs. Output Current 60 50 40 30 20 90 80 70 VIN = 4.2V VIN = 3.6V VIN = 5V 60 50 40 30 20 COUT=4.7µF L=1µH 10 10 100 1000 100 VIN = 5V VIN = 4.2V 50 40 30 COUT=4.7µF L=1µH 10 100 1000 1 10000 10 100 1000 10000 OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) Current Limit vs. Input Voltage VOUT Rise Time vs. CSS Efficiency (VOUT = 1.5V) vs. Output Current VIN = 3.6V 0 1 10000 VIN = 2.7V 60 10 0 1 70 20 COUT=4.7µF L=1µH 10 0 Efficiency (VOUT = 1.8V) vs. Output Current 100 EFFICIENCY (%) Efficiency (VOUT = 3.3V) vs. Output Current 6.0 1000000 100000 70 RISE TIME (µs) EFFICIENCY (%) 80 CURRENT LIMIIT (A) 90 VIN = 3.6V 60 VIN = 5V VIN = 2.7V VIN = 4.2V 50 40 10000 1000 30 20 100 COUT=4.7µF L=1µH 10 0 1 100 10 1000 VOUT = 1.8V COUT = 4.7µF 10 100 10000 VOUT = 1.8V COUT = 4.7µF 1.0 10000 100000 1000000 2.5 3.0 50 T = 25°C 45 40 T = -40°C No Switching SNS > VOUTNOM * 1.2 COUT = 4.7µF 4.0 3.0 3.5 4.0 4.5 5.0 5.5 November 2012 5.5 1.95 100 10 1.90 IOUT = 300mA IOUT = 1A 1.85 1.80 1.75 1.70 VOUTNOM = 1.8V 1.65 1 COUT = 4.7µF 1.60 2.5 INPUT VOLTAGE (V) 5.0 2.00 20 2.5 4.5 Line Regulation (CCM) OUTPUT VOLTAGE (V) 55 3.5 INPUT VOLTAGE (V) 1000 T = 125°C SHUTDOWN CURRENT (nA) QUIESCENT CURRENT (µA) 2.0 Shutdown Current vs. Input Voltage 60 25 3.0 CSS (pF) Quiescent Current vs. Input Voltage 30 4.0 0.0 1000 OUTPUT CURRENT (mA) 35 5.0 3.0 3.5 4.0 4.5 INPUT VOLTAGE (V) 6 5.0 5.5 2.5 3.0 3.5 4.0 4.5 5.0 5.5 INPUT VOLTAGE (V) M9999-110812-A Micrel Inc. MIC23158/9 Typical Characteristics (Continued) Load Regulation (CCM) 2.00 1.95 1.95 1.95 1.90 IOUT = 80mA IOUT = 20mA 1.85 1.80 1.75 IOUT = 1mA 1.70 VOUTNOM = 1.8V 3.0 3.5 4.0 4.5 5.0 1.85 1.80 1.75 VIN = 3.6V 1.70 5.5 1.90 1.85 1.80 1.75 COUT = 4.7µF VOUTNOM =1.8V 1000 1400 60 80 100 120 Switching Frequency vs. Temperature 5 FEEDBACK VOLTAGE (V) IOUT = 400mA 3.5 IOUT = 1.2A 2.5 2.0 TA = 25°C SWITCHING FREQUENCY (MHz) 0.65 IOUT = 100mA 1.5 40 OUTPUT CURRENT (mA) Feedback Voltage vs. Temperature 5.0 3.0 20 1800 OUTPUT CURRENT (mA) VOUTMAX vs. VIN 4.0 COUT = 4.7µF 1.60 0 600 INPUT VOLTAGE (V) 4.5 VIN = 3.6V 1.70 1.65 VOUTNOM = 1.8V 1.60 200 1.60 2.5 1.90 1.65 COUT = 4.7µF OUTPUT VOLTAGE (V) 2.00 1.65 OUTPUT VOLTAGE (V) Load Regulation (HLL) 2.00 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) Line Regulation (HLL) 0.64 0.63 0.62 0.61 VIN = 3.6V 0.60 VOUT = 1.8V 4 3 2 VIN = 3.6V 1 VOUTNOM = 1.8V COUT = 4.7µF 0 1.0 0.59 2.5 3.0 3.5 4.0 4.5 INPUT VOLTAGE (V) November 2012 5.0 5.5 -40 -40 -20 0 20 40 60 80 TEMPERATURE (°C) 7 100 -20 0 20 40 60 80 100 120 120 TEMPERATURE (°C) M9999-110812-A Micrel Inc. MIC23158/9 Functional Characteristics November 2012 8 M9999-110812-A Micrel Inc. MIC23158/9 Functional Characteristics (Continued) November 2012 9 M9999-110812-A Micrel Inc. MIC23158/9 Functional Characteristics (Continued) November 2012 10 M9999-110812-A Micrel Inc. MIC23158/9 Functional Diagram Figure 1. Simplified MIC23158 Functional Block Diagram – Adjustable Output Voltage November 2012 11 M9999-110812-A Micrel Inc. MIC23158/9 Functional Diagrams (Continued) Figure 2. Simplified MIC23159 Functional Block Diagram – Adjustable Output Voltage November 2012 12 M9999-110812-A Micrel Inc. MIC23158/9 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. Functional Description VIN The input supply (VIN) provides power to the internal MOSFETs for the switch mode regulator section. The VIN operating range is 2.7V to 5.5V. 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 PCB Layout Recommendations for details. PG The power good (PG) pin is an open drain output which indicates when the output voltage is within regulation. This is indicated by a logic high signal when the output voltage is above the PG threshold. Connect a pull up resistor greater than 5kΩ from PG to VOUT. AVIN Analog VIN (AVIN) provides power to the internal control and analog supply circuitry. AVIN and VIN must be tied together. Careful layout should be considered to ensure high frequency switching noise caused by VIN is reduced before reaching AVIN. A 1µF capacitor as close to AVIN as possible is recommended. Refer to the PCB Layout Recommendations for details. SS An external soft start circuitry set by a capacitor on the SS pin reduces inrush current and prevents the output voltage from overshooting at start up. The SS pin is used to control the output voltage ramp up time and the approximate equation for the ramp time in milliseconds 3 is 296 x 10 x ln(10) x CSS. For example, for a CSS = 470pF, TRISE ≈ 300µs. Refer to the “VOUT Rise Time vs. CSS” graph in the Typical Characteristics section. The minimum recommended value for CSS is 200pF. 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 0.1µA. Do not leave the EN pin floating. When disabled, the MIC23159 switches in a 225Ω load from the SNS pin to AGND, to discharge the output capacitor. FB The feedback (FB) pin is provided for the adjustable voltage option. This is the control input for setting 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 calculated using Equation 1: 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. R1 VOUT = VREF ⋅ 1 + R2 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. The SNS pin also provides the output active discharge circuit path to pull down the output voltage when the device is disabled. Recommended feedback resistor values: 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 PCB Layout Recommendations for details. November 2012 Eq. 1 13 VOUT R1 R2 1.2V 274k 294k 1.5V 316k 221k 1.8V 301k 158k 2.5V 324k 107k 3.3V 309k 71.5k M9999-110812-A Micrel Inc. MIC23158/9 Peak current can be calculated in Equation 2: Application Information The MIC23158/9 is a high-performance DC/DC step down regulator offering a small solution size. Supporting two outputs of up to 2A each in a 3mm x 4mm MLF package. Using the HyperLight Load switching scheme, the MIC23158/9 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. 1 − VOUT /VIN IPEAK = IOUT + VOUT 2× f ×L Eq. 2 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 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 the typical application circuit and Bill of Materials for details. Input Capacitor A 2.2µF ceramic capacitor or greater should be placed close to the VIN pin and PGND pin for bypassing. A Murata GRM188R60J475KE19D, 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. Output Capacitor The MIC23158/9 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 GRM188R60J475KE19D, size 0603, 4.7µF ceramic capacitor is recommended based upon performance, size and cost. Both the X7R or X5R temperature rating capacitors are recommended. Inductor Selection When selecting an inductor, it is important to consider the following factors: • Inductance • Rated current value • Size requirements • DC resistance (DCR) Figure 3. Transition between CCM Mode to HLL Mode 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” subsection. The transition between continuous conduction mode (CCM) to HyperLight Load mode is determined by the inductor ripple current and the load current. The diagram shows the signals for high-side switch drive (HSD) for TON control, the Inductor current, and the lowside switch drive (LSD) for TOFF control. In HLL mode, the inductor is charged with a fixed TON pulse on the high side switch. After this, the low side switch is turned on and current falls at a rate VOUT/L. The controller remains in HLL mode while the inductor falling current is detected to cross approximately -50mA. When the LSD (or TOFF) time reaches its minimum and the inductor falling current is no longer able to reach the threshold, the part is in CCM mode. The MIC23158/9 is designed for use with a 0.47µH to 2.2µH inductor. For faster transient response, a 0.47µH inductor will yield the best result. For lower output ripple, a 2.2µH 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 40°C 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. November 2012 14 M9999-110812-A Micrel Inc. MIC23158/9 Figure 4 shows an efficiency curve. From 1mA load to 2A, efficiency losses are dominated by quiescent current losses, gate drive and transition losses. By using the HyperLight Load mode, the MIC23158/9 is able to maintain high efficiency at low output currents. Over 180mA, 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 in Equation 5: Once in CCM mode, the TOFF time will not vary. Therefore, it is important to note that if L is large enough, the HLL transition level will not be triggered. That inductor is illustrated in Figure 3: L MAX = VOUT − 135ns Eq. 3 2 − 50mA Duty Cycle The typical maximum duty cycle of the MIC23158/9 is 80%. Efficiency Considerations Efficiency is defined as the amount of useful output power, divided by the amount of power supplied. 2 PDCR = IOUT x DCR V ×I Efficiency % = OUT OUT × V IN IIN × 100 Eq. 4 From that, the loss in efficiency due to inductor resistance can be calculated as in Equation 6: There are two types of losses in switching converters; DC losses and switching losses. DC losses are simply 2 the power dissipation of I R. 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 3MHz frequency and the switching transitions make up the switching losses. VOUT × IOUT Efficiency Loss = 1 − V OUT × IOUT + PDCR 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 Load Mode The MIC23158/9 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 an NMOS switch instead of a diode allows for lower voltage drop across the switching device when it is on. The synchronous 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 MIC23158/9 works in HyperLight Load 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 MIC23158/9 during light load currents by only switching when it is needed. 90 EFFICIENCY (%) 80 70 VIN = 2.7V 60 VIN = 3.6V VIN = 5V VIN = 4.2V 50 40 30 20 COUT=4.7µF L=1µH 10 0 1 10 100 1000 10000 OUTPUT CURRENT (mA) Figure 4. Efficiency under Load November 2012 × 100 Eq. 6 Efficiency (VOUT = 1.8V) vs. Output Current 100 Eq. 5 15 M9999-110812-A Micrel Inc. MIC23158/9 As the load current increases, the MIC23158/9 goes into continuous conduction mode (CCM) and switches at a frequency centered at 3MHz. The equation to calculate the load when the MIC23158/9 goes into continuous conduction mode may be approximated by the following formula: (V − VOUT ) × D ILOAD > IN 2L × f Eq. 7 As shown in Equation 7, the load at which the MIC23158/9 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). As shown in Figure 5, as the output current increases, the switching frequency also increases until the MIC23158/9 goes from HyperLight Load mode to PWM mode at approximately 180mA. The MIC23158/9 will switch at a relatively constant frequency around 3MHz once the output current is over 180mA. Switching Frequency vs. Output Current SWITCHING FREQUENCY (MHz) 5.0 4.5 4.0 L=1.0µH 3.5 3.0 L=0.47µH 2.5 2.0 1.5 1.0 0.5 0.0 0.1 1 10 100 1000 10000 OUTPUT CURRENT (mA) Figure 5. SW Frequency vs. Output Current November 2012 16 M9999-110812-A Micrel Inc. MIC23158/9 Typical Application Circuit (Adjustable Output) Bill of Materials Item C1, C2 C3, C4, C5, C6 C7, C8 L1, L2 R1 R2 R3 R4 R5, R6 R7, R8 Part Name 06036D105KAT2A GRM188R60J105KA01D C1608X5R0J105K 06036D475KAT2A GRM188R60J475KE19D C1608X5R0J475K 06035A471JAT2A GRM1885C1H471JA01D C1608C0G1H471J CDRH4D28CLDNP-1R0P LQH44PN1R0NJ0 CRCW06033013FKEA CRCW06031583FKEA CRCW06033163FKEA CRCW06032213FKEA CRCW06031003FKEA CRCW06031002FKEA U1 MIC23158/9YML Manufacturer (1) AVX (2) Murata (3) TDK AVX Murata TDK AVX Murata TDK (4) SUMIDA MURATA (5) Vishay/Dale Vishay/Dale Vishay/Dale Vishay/Dale Vishay/Dale Vishay/Dale Micrel, Inc (6) Description Qty. 1µF, 0603, 6.3V 2 4.7µF, 6.3V, X5R, 0603 4 470pF, 50V, 0603 2 1µH, 3.0A, 14mΩ, L5.1mm x W5.1mm x H3.0mm 1µH, 2.8A, 14mΩ, L5.1mm x W5.1mm x H3.0mm 301KΩ, 1%, 1/10W, 0603 158KΩ, 1%, 1/10W, 0603 316KΩ, 1%, 1/10W, 0603 221KΩ, 1%, 1/10W, 0603 100KΩ, 1%, 1/10W, 0603 10KΩ, 1%, 1/10W, 0603 3MHz PWM Dual 2A Buck Regulator with HyperLight Load and Power Good 2 1 1 1 1 2 2 1 Notes: 1. AVX: www.avx.com. 2. Murata: www.murata.com. 3. TDK: www.tdk.com. 4. Sumida: www.sumida.com. 5. Vishay/Dale: www.vishay.com. 6. Micrel, Inc.: www.micrel.com. November 2012 17 M9999-110812-A Micrel Inc. MIC23158/9 PCB Layout Recommendations Top Layer Bottom Layer November 2012 18 M9999-110812-A Micrel Inc. MIC23158/9 Package Information(1) 20-Pin 3mm x 4mm MLF Note: 1. Package information is correct as of the publication date. For updates and most current information, go to www.micrel.com. November 2012 19 M9999-110812-A Micrel Inc. MIC23158/9 Recommended Land Pattern 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. © 2012 Micrel, Incorporated. November 2012 20 M9999-110812-A