MP9942A The Future of Analog IC Technology High Efficiency 2A, 36V, 410kHz Synchronous Step-Down Converter with Power Good DESCRIPTION FEATURES The MP9942A is a high-frequency, synchronous, rectified, step-down, switch-mode converter with built-in power MOSFETs. It offers a very compact solution to achieve a 2A continuous output current with excellent load and line regulation over a wide input supply range. The MP9942A has synchronous mode operation for 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 and thermal shutdown. The MP9942A requires a minimal number of readily-available standard external components, and is available in a space-saving 8-pin TSOT23 package. Wide 4V to 30V Continuous Operating Input Range 36V Input Transient Tolerance 90mΩ/55mΩ Low RDS(ON) Internal Power MOSFETs High-Efficiency Synchronous Mode Operation 410kHz Switching Frequency Synchronizes from 200kHz to 2.2MHz External Clock High Duty Cycle for Automotive Cold-crank Force CCM Mode Internal Soft-Start Power Good Indicator Over-Current Protection with Hiccup Thermal Shutdown Output Adjustable from 0.8V Available in an 8-pin TSOT-23 package 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 MPS website under Quality Assurance. “MPS” and “The Future of Analog IC Technology” are Registered Trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION VIN C1 22 F EN/SYNC BST IN R4 20 C4 100nF L1 MP9942A EN/SYNC SW PG C6 0.1 F VCC 10 H R9 51k GND R1 41.2k 3.3V/2A C2 47 F VOUT FB R2 13k MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 1 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER ORDERING INFORMATION Part Number* MP9942AGJ Package TSOT23-8 Top Marking See Below * For Tape & Reel, add suffix –Z (e.g. MP9942AGJ–Z). TOP MARKING AQW: product code of MP9942AGJ; Y: year code; PACKAGE REFERENCE TOP VIEW PG 1 8 FB IN 2 7 VCC SW 3 6 EN/SYNC GND 4 5 BST TSOT23-8 MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 2 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance VIN .................................................. -0.3V to 40V VSW .................................................. -0.3V to 41V VBST ........................................................ VSW+6V All Other Pins ................................ -0.3V to 6V (2) (3) Continuous Power Dissipation (TA = +25°C) TSOT23-8 ................................................ 1.25W Junction Temperature ...............................150°C Lead Temperature ....................................260°C Storage Temperature ................. -65°C to 150°C TSOT23-8 .............................. 100 ..... 55... °C/W Recommended Operating Conditions (4) Continuous Supply Voltage VIN ........... 4V to 30V Output Voltage VOUT ..................0.8V to VIN*DMAX Operating Junction Temp. (TJ). -40°C to +125°C (5) θJA θJC Notes: 1) Absolute maximum ratings are rated under room temperature unless otherwise noted. Exceeding these ratings may damage the device. 2) About the details of EN pin’s ABS MAX rating, please refer to page 12, Enable/SYNC control section. 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 will cause excessive die temperature, and the regulator will go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. 4) The device is not guaranteed to function outside of its operating conditions. 5) Measured on JESD51-7, 4-layer PCB. MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 3 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER ELECTRICAL CHARACTERISTICS VIN = 12V, TJ = +25°C, unless otherwise noted. Parameter Symbol Supply Current (Shutdown) ISHDN Supply Current (Quiescent) IQ HS Switch-ON Resistance Condition Min Typ VEN = 0V Max Units 8 μA VEN = 2V, VFB = 1V 0.5 0.7 mA RON_HS VBST-SW=5V 90 155 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 Oscillator Frequency Fold-Back Frequency fSW fFB Maximum Duty Cycle DMAX Minimum ON Time (6) Under 40% Duty Cycle 3.5 5 7 A VFB=750mV VFB<400mV 320 70 410 100 500 130 kHz kHz VFB=750mV, 410kHz 92 95 % 70 ns tON_MIN Sync Frequency Range fSYNC 0.2 Feedback Voltage VFB 780 792 Feedback Current IFB MHz 804 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 VFB=820mV 2.4 VEN_HYS IEN 150 mV VEN=2V 4 6 μA VEN=0 0 0.2 μA VIN Under-Voltage Lockout Threshold-Rising VIN Under-Voltage Lockout Threshold-Falling INUVRISING 3.3 3.5 3.7 V INUVFALLING 3.1 3.3 3.5 V VIN Under-Voltage Lockout Threshold-Hysteresis INUVHYS VCC Regulator VCC VCC Load Regulation Soft-Start Period Thermal Shutdown Thermal Hysteresis (6) ICC=0mA 4.6 VOUT from 10% to 90% TSD mV 4.9 5.2 V 1.5 4 % 0.55 1.45 2.45 ms 150 170 ICC=5mA tSS (6) 200 TSD_HYS °C 30 °C PG Rising Threshold PGVth_RISING as percentage of VFB 86.5 90 93.5 % PG Falling Threshold PGVth as percentage of VFB 80.5 84 87.5 % FALLING MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 4 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER ELECTRICAL CHARACTERISTICS (continued) VIN = 12V, TJ = +25°C, unless otherwise noted. Parameter Symbol Condition PG Threshold Hysteresis PGVth_HYS as 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 Notes: 6) Derived from bench characterization. Not tested in production MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 5 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER PIN FUNCTIONS Package Pin # 1 2 3 4 5 6 7 8 Name Description Power Good. The output of this pin is an open drain and goes high if the output voltage exceeds 90% of the nominal voltage. Supply Voltage. The MP9942A operates from a 4V to 30V input rail. Requires C1 to IN decouple the input rail. Connect using a wide PCB trace. SW Switch Output. Connect with a wide PCB trace. System Ground. This pin is the reference ground of the regulated output voltage, and PCB GND layout requires special care. For best results, connect to GND with copper traces and vias. Bootstrap. Requires a capacitor connected between SW and BST pins to form a floating BST supply across the high-side switch driver. A 20Ω resistor placed between SW and BST cap is strongly recommended to reduce SW spike voltage. Enable/Synchronize. EN/SYNC high to enable the MP9942A. Apply an external clock to EN/SYNC the EN/SYNC pin to change the switching frequency. Bias Supply. Decouple with 0.1μF-to-0.22μF capacitor. Select a capacitor that does not VCC exceed 0.22μF Feedback. Connect to the tap of an external resistor divider from the output to GND, to set the output voltage. The frequency fold-back comparator lowers the oscillator frequency FB when the FB voltage is below 660mV to prevent current limit runaway during a short-circuit fault condition. PG MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 6 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER TYPICAL CHARACTERISTICS MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 7 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER TYPICAL CHARACTERISTICS (continued) MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 8 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS VIN = 12V, VOUT = 3.3V, L = 10µH, RBST=20Ω, TA = +25°C, unless otherwise noted. MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 9 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, VOUT = 3.3V, L = 10µH, RBST=20Ω, TA = +25°C, unless otherwise noted. MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 10 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, VOUT = 3.3V, L = 10µH, RBST=20Ω, TA = +25°C, unless otherwise noted. MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 11 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, VOUT = 3.3V, L = 10µH, RBST=20Ω, TA = +25°C, unless otherwise noted. \ MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 12 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER FUNCTIONAL BLOCK DIAGRAM Figure 1: Functional Block Diagram MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 13 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER OPERATION The MP9942A is a high-frequency, synchronous, rectified, step-down, switch-mode converter with built-in power MOSFETs. It offers a very compact solution to achieve 2A continuous output current with excellent load and line regulation over a wide input supply range. When MP9942A 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 turns on and remains on until its current reaches the value set by the COMP voltage. When the power switch is off, it remains off until the next clock cycle starts. 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 will be forced to turn off. Internal Regulator The 5V internal regulator power most of the internal circuitries. This regulator is supplied by 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 the VIN. A 0.1uF decoupling ceramic capacitor is needed at the pin. Error Amplifier The error amplifier compares the FB pin voltage against the internal 0.792V reference (REF) and outputs a COMP voltage—this COMP voltage 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 pin that turns the regulator on and off: Drive EN/SYNC high to turn on the regulator, drive it low to turn it off. An internal 500kΩ resistor from EN/SYNC to GND allows EN/SYNC to be floated to shut down the chip. The EN/SYNC pin is clamped internally using a 6.5V series Zener diode, as shown in Figure 2 Connect the EN/SYNC pin through a pullup resistor to any voltage connected to the VIN pin— the pullup resistor limits the EN/SYNC input current to less than 150µA. For example, with 12V connected to VIN, RPULLUP ≥ (12V – 6.5V) ÷ 150µA = 36.7kΩ. Connecting the EN/SYNC pin directly to a voltage source without any pullup resistor requires limiting voltage amplitude to ≤6V to prevent damage to the Zener diode. Figure 2: 6.5V-type Zener Diode Connect an external clock with a range of 200kHz to 2.2MHz to synchronize the internal clock rising edge to the external clock rising edge. The pulse width of external clock signal should be less than 2μs. Under-Voltage Lockout Under-voltage lockout (UVLO) protects the chip from operating at an insufficient supply voltage. The MP9942A 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 The soft-start prevents the converter output voltage from overshooting during startup. When the chip starts, the internal circuitry generates a soft-start voltage (SS) 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 1.45ms. Over-Current Protection and Hiccup The MP9942A has cycle-by-cycle over current limit when the inductor current peak value exceeds the set current limit threshold. If the output voltage starts to drop until FB is below the Under-Voltage (UV) threshold—typically 84% below the reference—the MP9942A enters hiccup mode to periodically restart the part. This protection mode is especially useful when the MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 14 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER output is dead-shorted to ground. The average short-circuit current is greatly reduced to alleviate the thermal issue and to protect the regulator. The MP9942A exits the hiccup mode once the over-current condition is removed. Thermal Shutdown Thermal shutdown prevents the chip from operating at exceedingly high temperatures. When the silicon die temperature exceeds 170°C, it shuts down the whole chip. 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. This floating driver has its own UVLO protection, with a rising threshold of 2.2V and hysteresis of 150mV. The bootstrap capacitor voltage is regulated internally by VIN through D1, M1, C4, L1 and C2 (Figure 3). If (VIN-VSW) exceeds 5V, U1 regulates M1 to maintain a 5V BST voltage across C4. A 20Ω resistor placed between SW and BST cap is strongly recommended to reduce SW spike voltage. floating driver is not subject to this shutdown command. Power Good The MP9942A has power good (PG) output. The PG pin is the open drain of a MOSFET. It should be connected to VCC or some other voltage source through a resistor (e.g. 100kΩ). In the presence of an input voltage, the MOSFET turns on so that the PG pin is pulled to low before SS is ready. After VFB reaches 90%×REF, the PG pin is pulled high after a delay, typically 90μs. When VFB drops to 84%×REF, the PG pin is pulled low. Also, PG is pulled low if thermal shutdown or EN is pulled low. Figure 3: Internal Bootstrap Charging Circuit Startup and Shutdown If both VIN and EN exceed their appropriate thresholds, the chip starts: The reference block starts first, generating stable reference voltage and currents, and then the internal regulator is enabled. The regulator provides 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 first blocked to avoid any fault triggering. The COMP voltage and the internal supply rail are then pulled down. The MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 15 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER APPLICATION INFORMATION Setting the Output Voltage The external resistor divider sets the output voltage (see Typical Application on page 1). Choose R1 around 41.2kΩ. R2 is then given by: R2 IL(MAX) ILOAD R1 VOUT 1 0.792V 8 RT R1 IL 2 VIN UVLO Setting The T-type network—as shown in Figure —is highly recommended when VOUT is low. FB Choose the inductor ripple current to be approximately 30% of the maximum load current. The maximum inductor peak current is: VOUT R2 The MP9942A has internal fix under voltage lock out (UVLO) threshold: rising threshold is 3.5V while falling threshold is about 3.3V. For the application needs higher UVLO point, external resistor divider between EN/SYNC and IN as shown in Figure 5 can be used to get higher equivalent UVLO threshold. Figure 4: T-Type Network RT+R1 is used to set the loop bandwidth. Basically, higher RT+R1, lower bandwidth. To ensure the loop stability, it is strongly recommended to limit the bandwidth lower than 40kHz based on the 410kHz default fsw. Table 1 lists the recommended T-type resistors value for common output voltages. Table 1: Resistor Selection for Common Output Voltages (7) VOUT (V) R1 (kΩ) R2 (kΩ) RT (kΩ) 3.3 41.2 (1%) 13 (1%) 51 (1%) 5 41.2 (1%) 7.68 (1%) 51 (1%) Notes: 7) The feedback resistors in Table 1 are optimized for 410kHz switching frequency. The detailed schematic is shown on TYPICAL APPLICATION CIRCUITS. Selecting the Inductor Use a1µH-to-10µH inductor with a DC current rating of at least 25% percent higher than the maximum load current for most applications. For highest efficiency, an inductor with small DC resistance is recommended. For most designs, the inductance value can be derived from the following equation. L1 Figure 5: Adjustable UVLO using EN divider The UVLO threshold can be computed from below two equations: INUVRISING (1 INUVFALLING (1 REN_UP 500k//REN_DOWN REN_UP 500k//REN_DOWN ) VEN_RISING ) VEN_FALLING Where VEN_RISING=1.4V, VEN_FALLING=1.25V. When choose REN_UP, make sure it is big enough to limit the current flows into EN/SYNC pin lower than 100uA. Selecting the Input Capacitor The input current to the step-down converter is discontinuous, therefore requires a capacitor is to supply the AC current to the step-down converter VOUT (VIN VOUT ) VIN IL fOSC Where ∆IL is the inductor ripple current. MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 16 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER while maintaining the DC input voltage. Use low ESR capacitors for the best performance. Use ceramic capacitors with X5R or X7R dielectrics for best results because of their low ESR and small temperature coefficients. For most application, a 22µF ceramic capacitor is sufficient to maintain the DC input voltage. And it is strongly recommended to use another lower value capacitor (e.g. 0.1µF) with small package size (0603) to absorb high frequency switching noise. Make sure place the small size capacitor as close to IN and GND pins as possible (see PCB LAYOUT section). Since C1 absorbs the input switching current, it requires an adequate ripple current rating. The RMS current in the input capacitor can be estimated by: I C1 ILOAD VOUT VOUT 1 VIN VIN The worse case condition occurs at VIN = 2VOUT, where: IC1 ILOAD 2 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, make sure that they have enough capacitance to provide sufficient charge to prevent excessive voltage ripple at input. The input voltage ripple caused by capacitance can be estimated by: VIN ILOAD V V OUT 1 OUT fS C1 VIN VIN Where L1 is the inductor value and RESR is the equivalent series resistance (ESR) value of the output capacitor. For ceramic capacitors, the capacitance dominates the impedance at the switching frequency, and the capacitance causes the majority of the output voltage ripple. For simplification, the output voltage ripple can be estimated by: ∆VOUT V VOUT 1 OUT VIN 8 fS L1 C2 2 For tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated to: ∆VOUT VOUT V 1 OUT RESR fS L1 VIN The characteristics of the output capacitor also affect the stability of the regulation system. The MP9942A can be optimized for a wide range of capacitance and ESR values. BST Resistor and External BST Diode A 20Ω resistor in series with BST capacitor is recommended to reduce the SW spike voltage. Higher resistance is better for SW spike reduction, but will compromise the efficiency on the other hand. An external BST diode can enhance the efficiency of the regulator when the duty cycle is high (>65%) or VIN is below 5V, and also help to avoid BST voltage insufficient. A power supply between 3.3V and 5V can be used to power the external bootstrap diode and VCC or VOUT is the good choice of this power supply in the circuit as shown in Figure 6. 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 by: VOUT VOUT VOUT 1 1 RESR fS L1 VIN 8 fS C2 MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 17 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER C3 R1 GND C4 SW R5 PCB Layout (8) PCB layout, especially the input capacitor and VCC capacitor placement, is very important to achieve stable operation. For the best results, follow these guidelines: R9 6 5 4 7 3 2 R4 L1 C8 C1 Figure 6: Optional External Bootstrap Diode to Enhance Efficiency The recommended external BST diode is 1N4148, and the BST capacitor value is 0.1µF to 1μF. 8 R7 1 R2 C6 Vin C2 Vout GND Top Layer 1) Place the ceramics input capacitor as close to IN and GND pins as possible, especially the small package size (0603) input bypass capacitor. Keep the connection of input capacitor and IN pin as short and wide as possible. 2) Place the VCC capacitor to VCC pin and GND pin as close as possible. Make the trace length of VCC pin-VCC capacitor anode-VCC capacitor cathode-chip GND pin as short as possible. 3) Use large ground plane directly connect to GND pin. Add vias near the GND pin if bottom layer is ground plane. 4) Route SW, BST away from sensitive analog areas such as FB. 5) Place the T-type feedback resistor close to chip to ensure the trace which connects to FB pin as the short as possible. Notes: 8) The recommended layout is based on the typical application circuit in Page 18. Bottom Layer Figure 7: Recommended PCB Layout MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 18 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER Design Example Below is a design example following the application guidelines for the specifications: Table 2—Design Example VIN VOUT IO 12V 3.3V 2A The detailed application schematic is shown in Figure 8. The typical performance and circuit waveforms have been shown in the Typical Performance Characteristics section. For more device applications, please refer to the related Evaluation Board Datasheets. MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 19 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER TYPICAL APPLICATION CIRCUITS Figure 8: 12VIN, 3.3V/2A Output MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 20 MP9942A – 36V, 2A SYNCHRONOUS STEP-DOWN CONVERTER PACKAGE INFORMATION TSOT23-8 See note 7 EXAMPLE TOP MARK PIN 1 ID RECOMMENDED LAND PATTERN TOP VIEW SEATING PLANE SEE DETAIL ''A'' FRONT VIEW SIDE VIEW NOTE: DETAIL ''A'' 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH, PROTRUSION OR GATE BURR. 3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION. 4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.10 MILLIMETERS MAX. 5) JEDEC REFERENCE IS MO-193, VARIATION BA. 6) DRAWING IS NOT TO SCALE. 7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARK FROM LEFT TO RIGHT, (SEE EXAMPLE TOP MARK) 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. MP9942A Rev. 1.0 www.MonolithicPower.com 10/14/2016 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 21