MPQ4423AGQ-AEC1-P

MPQ4423A 3A, 36V, High-Efficiency, Synchronous, Step-Down Converter AEC-Q100 Qualified DESCRIPTION FEATURES The MPQ4423A is a high-efficiency, synchronous, rectified, step-down, switch-mode converter with built-in power MOSFETs. It offers a very compact solution that achieves 3A of continuous output current with excellent load and line regulation over a wide input supply range. • • • • • The MPQ4423A uses synchronous mode operation to achieve higher efficiency over the output current load range. Current-mode operation provides fast transient response and eases loop stabilization. • • • • • • • • • Full protection features include over-current protection (OCP) and thermal shutdown. The MPQ4423A requires a minimal number of readily available, standard, external components and is available in a compact QFN-8 (3mmx3mm) package. Wide 4V to 36V Continuous Operating Input Range 85mΩ/55mΩ Low RDS(ON) Internal Power MOSFETs High-Efficiency Synchronous Mode Operation Default 410kHz Switching Frequency Synchronizes to a 200kHz to 2.2MHz External Clock High Duty Cycle for Automotive Cold Crank Forced CCM Mode Internal Soft Start Power Good Over-Current Protection (OCP) and Hiccup Thermal Shutdown Output Adjustable from 0.8V Available in a QFN-8 (3mmx3mm) Package Available in AEC-Q100 Grade 1 APPLICATIONS • • • Automotive Industrial Control System Distributed Power Systems All MPS parts are lead-free, halogen-free, and adhere to the RoHS directive. For MPS green status, please visit the MPS website under Quality Assurance. “MPS” and “The Future of Analog IC Technology” are registered trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION 4 R4 7 VIN C1 22μF 20 C4 0.1μF BST IN SW L1 6 10μH MPQ4423A 8 EN/SYNC PG FB C3 0.1μF 1 R3 VOUT R1 41.2k 51k R2 13k 5 2 VCC GND 3 EN/SYNC 3.3V/3A C2 47μF MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 1 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER ORDERING INFORMATION Part Number* MPQ4423AGQ MPQ4423AGQ-AEC1 Package QFN-8 (3mmx3mm) QFN-8 (3mmx3mm) Top Marking See Below * For Tape & Reel, add suffix –Z (e.g. MPQ4423AGQ–Z) TOP MARKING APP: Product code of MPQ4420AGJ and MPQ4420AGJ-AEC1 Y: Year code LLL: Lot number PACKAGE REFERENCE TOP VIEW FB 1 8 PG VCC 2 7 IN EN/SYNC 3 6 SW BST 4 5 GND QFN-8 (3mmx3mm) MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 2 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance VIN ................................................ -0.3V to 40V VSW ................................................ -0.3V to 41V VBS ......................................................VSW + 6V (2) All other pins ................................ -0.3V to 6V (3) Continuous power dissipation (TA = +25°C) QFN-8 (3mmx3mm) .................................2.27W Junction temperature ............................... 150°C Lead temperature .................................... 260°C Storage temperature .................. -65°C to 150°C QFN-8 (3mmx3mm) .............. 55 ...... 13 ... °C/W Recommended Operating Conditions Continuous supply voltage (VIN) ......... 4V to 36V Output voltage (VOUT) ............... 0.8V to 0.9 x VIN Operating junction temp. (TJ)… -40°C to +125°C (4) θJA θJC NOTES: 1) Absolute maximum ratings are rated under room temperature unless otherwise noted. Exceeding these ratings may damage the device. 2) For details on EN’s ABS MAX rating, please refer to the Enable/SYNC Control section on page 14. 3) The maximum allowable power dissipation is a function of the maximum junction temperature TJ (MAX), the junction-toambient thermal resistance θJA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by PD (MAX) = (TJ (MAX)-TA)/θJA. Exceeding the maximum allowable power dissipation produces an excessive die temperature, causing the regulator to go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. 4) Measured on JESD51-7, 4-layer PCB. MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 3 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER ELECTRICAL CHARACTERISTICS VIN = 12V, TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TJ = +25°C. Parameter Symbol Supply current (shutdown) ISHDN Supply current (quiescent) IQ Condition Min Typ VEN = 0V Max Units 8 μA VEN = 2V, VFB = 1V, no switching 0.6 0.8 mA HS switch on resistance RON_HS VBST-SW = 5V 85 150 mΩ LS switch on resistance RON_LS VCC = 5V 55 105 mΩ Switch leakage ILKG_SW VEN = 0V, VSW = 12V 1 μA Current limit ILIMIT Under 40% duty cycle 3.6 5.7 7.8 A fSW VFB = 750mV 320 410 500 kHz Foldback frequency fFB VFB < 400mV 70 100 130 kHz Maximum duty cycle DMAX VFB = 750mV, 410kHz 92 95 % 70 ns Oscillator frequency (5) Minimum on time tON MIN Sync frequency range fSYNC Feedback voltage VFB Feedback current IFB 0.2 TJ = 25°C 780 776 VFB = 820mV 2.4 MHz 792 804 808 mV 10 100 nA EN rising threshold VEN_RISING 1.15 1.4 1.65 V EN falling threshold VEN_FALLING 1.05 1.25 1.45 V EN threshold hysteresis EN input current VEN_HYS IEN VIN under-voltage threshold rising VIN under-voltage threshold falling lockout VIN under-voltage threshold hysteresis lockout VCC regulator lockout VEN = 2V 4 8 μA VEN = 0 0 0.2 μA 3.3 3.5 3.7 V INUVFALLING 3.1 3.3 3.5 V 200 INUVHYS VCC load regulation Thermal shutdown ICC = 0mA 4.6 tSS VOUT from 10% to 90% mV 4.9 5.2 V 1.5 4 % 0.45 1. 5 2.55 ms 150 170 °C 30 °C ICC = 5mA (5) Thermal hysteresis mV INUVRISING VCC Soft-start period 150 (5) PG rising threshold PGVth_RISING as a percentage of VFB 86 90 94 % PG falling threshold PGVth as a percentage of VFB 80 84 88 % FALLING MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 4 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER ELECTRICAL CHARACTERISTICS (continued) VIN = 12V, TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TJ = +25°C. Parameter Symbol Condition PG threshold hysteresis PGVth_HYS as a percentage of VFB Min Typ Max 6 Units % PG rising delay PGTd_RISING 40 90 160 μs PG falling delay PGTd_FALLING 30 55 95 μs 0.1 0.3 V 10 100 nA PG sink current capability PG leakage current VPG Sink 4mA ILKG_PG NOTE: 5) Derived from bench characterization. Not tested in production MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 5 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER TYPICAL CHARACTERISTICS MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 6 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER TYPICAL CHARACTERISTICS (continued) MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 7 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS VIN = 12V, VOUT = 3.3V, L = 10µH, RBST = 20Ω, TA = +25°C, unless otherwise noted. MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 8 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, VOUT = 3.3V, L = 10µH, RBST = 20Ω, TA = +25°C, unless otherwise noted. MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 9 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, VOUT = 3.3V, L = 10µH, RBST = 20Ω, TA = +25°C, unless otherwise noted. MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 10 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, VOUT = 3.3V, L = 10µH, RBST = 20Ω, TA = +25°C, unless otherwise noted. MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 11 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER PIN FUNCTIONS Pin # 1 2 3 4 5 6 7 8 Name Description Feedback. Connect FB to the tap of an external resistor divider from the output to GND to set the output voltage. When the FB voltage is below 660mV, the frequency foldback FB comparator lowers the oscillator frequency to prevent current limit runaway during a shortcircuit fault condition. Bias supply. Decouple VCC with a 0.1μF to 0.22μF capacitor. Select a capacitor that VCC does not exceed 0.22μF. Enable/synchronize. Drive EN/SYNC high to enable the MPQ4423A. Apply an external EN/SYNC clock to EN/SYNC to change the switching frequency. Bootstrap. A capacitor connected between SW and BST is required to form a floating BST supply across the high-side switch driver. A 20Ω resistor placed between the SW and BST cap is strongly recommended to reduce SW voltage spikes. System ground. GND is the reference ground of the regulated output voltage. GND GND requires special consideration during PCB layout. For best results, connect GND with copper traces and vias. Switch output. Connect using a wide PCB trace. SW Supply voltage. The MPQ4423A operates from a 4V to 36V input rail. C1 is required to IN decouple the input rail. Connect using a wide PCB trace. Power good. The output of PG is an open drain and goes high if the output voltage PG exceeds 90% of the nominal voltage. MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 12 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER BLOCK DIAGRAM Figure 1: Functional Block Diagram MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 13 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER OPERATION The MPQ4423A is a high-efficiency, synchronous, rectified, step-down, switch-mode converter with built-in power MOSFETs. It offers a very compact solution that achieves 3A of continuous output current with excellent load and line regulation over a wide input supply range. The MPQ4423A operates in a fixed-frequency, peak-current-control mode to regulate the output voltage. An internal clock initiates a PWM cycle. The integrated high-side power MOSFET (HSFET) turns on and remains on until its current reaches the value set by the COMP voltage (VCOMP). When the power switch is off, it remains off until the next clock cycle begins. If the current in the power MOSFET does not reach the current value set by COMP within 95% of one PWM period, the power MOSFET is forced off. Internal Regulator The 5V internal regulator powers most of the internal circuitries. This regulator takes the VIN input and operates in the full VIN range. When VIN exceeds 5.0V, the output of the regulator is in full regulation; when VIN falls below 5.0V, the output of the regulator decreases following VIN. A 0.1µF decoupling ceramic capacitor is needed at VCC. Error Amplifier (EA) The error amplifier compares the FB voltage against the internal 0.8V reference (REF) and outputs a COMP voltage that controls the power MOSFET current. The optimized internal compensation network minimizes the external component count and simplifies the control loop design. Enable/SYNC Control EN/SYNC is a digital control that turns the regulator on and off. Drive EN/SYNC high to turn on the regulator; drive EN/SYNC low to turn off the regulator. An internal 500kΩ resistor from EN/SYNC to GND allows EN/SYNC to be floated to shut down the chip. EN/SYNC is clamped internally using a 6.5V series Zener diode (see Figure 2). Connect the EN/SYNC input through a pull-up resistor to any voltage connected to VIN. The pull-up resistor limits the EN/SYNC input current below 150µA. For example, with 12V connected to VIN, RPULLUP ≥ (12V - 6.5V) ÷ 150µA = 36.7kΩ. Connecting EN/SYNC directly to a voltage source without a pull-up resistor requires limiting the voltage amplitude below or equal to 6V to prevent damage to the Zener diode. Figure 2: 6.5V-Type Zener Diode To use the synchronous function, connect an external clock in the range of 200kHz to 2.2MHz to EN/SYNC. The external clock should be connected at least 2ms after the output voltage is set. The internal clock rising edge is synchronized to the external clock rising edge when the external clock is connected. The pulse width of the external clock signal should be below 1.7μs. Under-Voltage Lockout (UVLO) Under-voltage lockout (UVLO) protects the chip from operating at an insufficient supply voltage. The MPQ4423A UVLO comparator monitors the output voltage of the internal regulator (VCC). The UVLO rising threshold is about 3.5V, while its falling threshold is 3.3V. Internal Soft Start (SS) The soft start (SS) prevents the converter output voltage from overshooting during start-up. When the chip starts up, the internal circuitry generates a soft-start voltage that ramps up from 0V to 1.2V. When SS is lower than REF, SS overrides REF so the error amplifier uses SS as the reference. When SS exceeds REF, the error amplifier uses REF as the reference. The SS time is internally set to 1.5ms. Over-Current Protection (OCP) and Hiccup The MPQ4423A uses a cycle-by-cycle overcurrent limit when the inductor current peak value exceeds the set current-limit threshold. If the output voltage drops until FB is below the undervoltage (UV) threshold (typically 84% below the reference), the MPQ4423A enters hiccup mode to restart the part periodically. This protection mode is especially useful when the output is dead-shorted to ground. MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 14 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER The average short-circuit current is reduced greatly to alleviate the thermal issue and to protect the regulator. The MPQ4423A exits hiccup mode once the over-current condition is removed. D1 VIN M1 HS-FET BST 5V +- U1 R4 + C4 VOUT SW Thermal Shutdown Thermal shutdown prevents the chip from operating at exceedingly high temperatures. When the silicon die temperature exceeds 170°C, the entire chip shuts down. When the temperature drops below its lower threshold (typically 140°C), the chip is enabled again. Floating Driver and Bootstrap Charging An external bootstrap capacitor powers the floating power MOSFET driver. A dedicated internal regulator charges and regulates the bootstrap capacitor voltage to about 5V (see Figure 3). When the voltage between the BST and SW nodes drops below regulation, a PMOS pass transistor connected from VIN to BST turns on. The charging current path is from VIN to BST and then to SW. The external circuit should provide enough voltage headroom to facilitate charging. As long as VIN is higher than SW significantly, the bootstrap capacitor remains charged. When the HS-FET is on, VIN is approximately equal to VSW, so the bootstrap capacitor cannot charge. When the LS-FET is on, VIN - VSW reaches its maximum for fast charging (the charging path is shown in Figure 3a). When the HS-FET and LS-FET are both off, VSW is equal to VOUT, so the difference between VIN and VOUT can charge the bootstrap capacitor (the charging path is shown in Figure 3b). The floating driver has its own UVLO protection, with a rising threshold of 2.2V and hysteresis of 150mV. A 20Ω resistor placed between the SW and BST cap is strongly recommended to reduce SW voltage spikes. L1 C2 LS-FET 3b: BST Charging Path when HS-FET and LS-FET are Both Off Figure 3: Internal Bootstrap Charging Circuit Start-Up and Shutdown If both VIN and EN exceed their appropriate thresholds, the chip starts up. The reference block starts first, generating a stable reference voltage and current, and then the internal regulator is enabled. The regulator provides a stable supply for the remaining circuitries. Three events can shut down the chip: EN low, VIN low and thermal shutdown. In the shutdown procedure, the signaling path is blocked first to avoid any fault triggering. VCOMP and the internal supply rail are then pulled down. The floating driver is not subject to this shutdown command. Power Good (PG) The MPQ4423A has a power good (PG) output. PG is the open drain of the MOSFET. It should be connected to VCC or another voltage source through a resistor (e.g.: 100kΩ). In the presence of an input voltage, the MOSFET turns on so that PG is pulled low before SS is ready. When VFB reaches 90%xREF, PG is pulled high after a delay (typically 90μs). When VFB drops to 84%xREF, PG is pulled low. PG is also pulled low if thermal shutdown occurs or if EN is pulled low. D1 VIN M1 HS-FET BST 5V +- U1 R4 + C4 VOUT SW L1 C2 LS-FET 3a: BST Charging Path when LS-FET is On MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 15 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER APPLICATION INFORMATION Setting the Output Voltage The external resistor divider sets the output voltage (see Typical Application on page 1). The feedback resistor (R1) sets the feedback loop bandwidth with the internal compensation capacitor. Choose R1 to be around 40kΩ. R2 can then be calculated with Equation (1): R2 = R1 (1) VOUT −1 0.792V The T-type network is highly recommended when VOUT is low (see Figure 4). RT R1 FB R2 Choose the inductor ripple current to be approximately 30% of the maximum load current. The maximum inductor peak current can be calculated with Equation (3): DIL (3) 2 Use a larger inductor for improved efficiency below 100mA under light-load conditions. IL(MAX ) = ILOAD + VIN Under-Voltage Lockout (UVLO) Setting The MPQ4423A has an internal, fixed, undervoltage lockout (UVLO) threshold. The rising threshold is 3.5V, while its falling threshold is about 3.3V. The application needs a higher UVLO point, so the external resistor divider between EN/SYNC and IN can be used to achieve a higher equivalent UVLO threshold (see Figure 5). VIN R5 Figure 4: T-Type Network RT + R1 is used to set the loop bandwidth. The higher RT + R1 is, the lower the bandwidth is. To ensure loop stability, it is strongly recommended to limit the bandwidth below 40kHz based on the 410kHz default fsw. Table 1 lists the recommended T-type resistor values for common output voltages. Table 1: Resistor Selection for Common Output Voltages VOUT (V) R1 (kΩ) R2 (kΩ) RT (kΩ) 3.3 5 41.2 (1%) 41.2 (1%) 13 (1%) 7.68 (1%) 51 (1%) 51 (1%) Selecting the Inductor Use a 1µH to 10µH inductor with a DC current rating at least 25% higher than the maximum load current for most applications. For the highest efficiency, an inductor with a small DC resistance is recommended. For most designs, the inductance value can be derived from Equation (2): L1 = IN VOUT × (VIN − VOUT ) VIN × ∆IL × fOSC Where ΔIL is the inductor ripple current. (2) EN/SYNC R6 500k Figure 5: Adjustable UVLO using EN/SYNC Divider The UVLO threshold can be calculated with Equation (4) and Equation (5): INUVRISING = (1 + R5 ) × VEN_RISING 500k//R6 (4) INUVFALLING = (1 + R5 ) × VEN_FALLING 500k//R6 (5) Where VEN_RISING is 1.4V and VEN_FALLING is 1.25V. When selecting R5, ensure that it is large enough to limit the current flows into EN/SYNC below 150µA. Selecting the Input Capacitor The input current to the step-down converter is discontinuous and therefore requires a capacitor to supply AC current to the step-down converter while maintaining the DC input voltage. For best performance, use low ESR capacitors. Ceramic capacitors with X5R or X7R dielectrics are recommended because of their low ESR and small temperature coefficients. MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 16 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER For most applications, a 22µF ceramic capacitor is sufficient to maintain the DC input voltage. It is strongly recommended to use another lower value capacitor (e.g.: 1µF) with a small package size (0603) to absorb high-frequency switching noise. Place the smaller capacitor as close to IN and GND as possible (see PCB Layout Guidelines on page 18). For ceramic capacitors, the capacitance dominates the impedance at the switching frequency and causes the majority of the output voltage ripple. For simplification, the output voltage ripple can be estimated with Equation (10):  V  VOUT (10) = ΔV × 1 − OUT Since C1 absorbs the input switching current, it requires an adequate ripple current rating. The RMS current in the input capacitor can be estimated with Equation (6): With tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated with Equation (11): IC1 = ILOAD × VOUT  VOUT  × 1− VIN  VIN  (6) The worse case condition occurs at VIN = 2VOUT, shown in Equation (7): IC1 = ILOAD 2 (7) For simplification, choose an input capacitor with an RMS current rating greater than half of the maximum load current. The input capacitor can be electrolytic, tantalum, or ceramic. When using electrolytic or tantalum capacitors, add a small, high-quality ceramic capacitor (e.g.: 1μF) placed as close to the IC as possible. When using ceramic capacitors, ensure that they have enough capacitance to provide a sufficient charge to prevent an excessive voltage ripple at input. The input voltage ripple caused by capacitance can be estimated with Equation (8): DV = IN   ILOAD V V × OUT ×  1 − OUT  fS × C1 VIN  VIN  ΔVOUT =  8 × fS 2 × L1 × C2  VOUT  V ×  1 − OUT fS × L1  VIN  VIN    × RESR  (11) The characteristics of the output capacitor also affect the stability of the regulation system. The MPQ4423A can be optimized for a wide range of capacitance and ESR values. BST Resistor and External BST Diode A 20Ω resistor in series with a BST capacitor is recommended to reduce SW voltage spikes. A higher resistance is better for SW spike reduction but compromises efficiency. An external BST diode can enhance the efficiency of the regulator when the duty cycle is high (>65%). A power supply between 2.5V and 5V can be used to power the external bootstrap diode. Either VCC or VOUT can be used as the power supply in this circuit (see Figure 6). (8) Selecting the Output Capacitor The output capacitor (C2) maintains the DC output voltage. Use ceramic, tantalum, or lowESR electrolytic capacitors. For best results, use low ESR capacitors to keep the output voltage ripple low. The output voltage ripple can be estimated with Equation (9): VOUT  VOUT ∆VOUT = × 1− fS × L1  VIN OUT  (9)   1   ×  RESR + 8 × fS × C2    Figure 6: Optional External Bootstrap Diode to Enhance Efficiency The recommended external BST diode is IN4148, and the recommended BST capacitor value is 0.1µF to 1μF. Where L1 is the inductor value and RESR is the equivalent series resistance (ESR) value of the output capacitor. MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 17 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER PCB Layout Guidelines Efficient PCB layout, especially the input capacitor and VCC capacitor placement, is critical for stable operation. For best results, refer to Figure 7 and follow the guidelines below. 1. Place the ceramics input capacitor as close to IN and GND as possible, especially the small package size (0603) input bypass capacitor. 2. Keep the connection of the input capacitor and IN as short and wide as possible. 3. Place the VCC capacitor to VCC and GND as close as possible. 4. Make the trace length of VCC to the capacitor to GND as short as possible. 5. Use a large ground plane connected directly to GND. 6. Add vias near GND if the bottom layer is the ground plane. Top Layer 7. Route SW and BST away from sensitive analog areas such as FB. 8. Place the T-type feedback resistor close to the chip to ensure that the trace connecting to FB is as short as possible. Bottom Layer Figure 7: Recommended PCB Layout MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 18 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER TYPICAL APPLICATION CIRCUITS 7 VIN C1A 10μF C1B C1C 10μF 0.1μF BST 4 IN R5 1M 3 8 EN/SYNC SW 6 10μH PG R6 100k 2 C3 0.1μF R4 20 C4 100nF L1 MPQ4423A VCC GND 5 FB 1 R3 51k 3.3V/2A C2A C2B VOUT 22μF 22μF R1 41.2k R2 13k Figure 8: 3.3V Output Typical Application Circuit MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 19 MPQ4423A – 3A, 36V, SYNCHRONOUS, STEP-DOWN CONVERTER PACKAGE INFORMATION QFN-8 (3mmx3mm) PIN 1 ID 0.15x45° TYP. PIN 1 ID MARKING PIN 1 ID INDEX AREA BOTTOM VIEW TOP VIEW SIDE VIEW 0.15x45° NOTE: 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH. 3) LEAD COPLANARITY SHALL BE 0.10 MILLIMETERS MAX. 4) JEDEC REFERENCE IS MO-220. 5) DRAWING IS NOT TO SCALE. RECOMMENDED LAND PATTERN NOTICE: The information in this document is subject to change without notice. Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not assume any legal responsibility for any said applications. MPQ4423A Rev.1.0 www.MonolithicPower.com 5/24/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 20