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MP1591_06 MPS | Alldatasheet

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Technical content

2A, 32V, 330KHz Step-Down Converter MP1591 Rev. 2.3 www.MonolithicPower.com 1 9/27/2006 MPS Proprietary Information. Unaut horized Photocopy and Duplication Prohibited. © 2006 MPS. All Rights Reserved. The Future of Analog IC Technology

DESCRIPTION

The MP1591 is a high voltage step-down converter ideal for automotive power adapter battery chargers. Its wide 6.5V to 32V input voltage range covers the automotive battery’s requirements and it achieves 2A continuous output for quick charge capability. Current mode operation provides fast transient response and eases loop stabilization. Fault protection includes cycle-by-cycle current limiting and thermal shutdown. In shutdown mode, the converter draws only 20µA of supply current. The MP1591 requires a minimum number of readily available external components to complete a 2A step-down DC to DC converter solution. EVALUATION BOARD REFERENCE Board Number Dimensions EV0020 2.1”X x 1.4”Y x 0.5”Z

FEATURES

• Wide 6.5V to 32V Input Operating Range
• 34V Absolute Maximum Input
• 2A Output Current
• 120m Ω Internal Power MOSFET Switch
• Stable with Low ESR Output Ceramic Capacitors
• Up to 95% Efficiency
• 20µA Shutdown Mode
• Fixed 330KHz Frequency
• Thermal Shutdown
• Cycle-by-Cycle Over Current Protection
• Output Adjustable From 1.23V to 21V
• Under Voltage Lockout
• Reference Voltage Output
• Available in 8-Pin SOIC Packages

APPLICATIONS

• Automotive Power Adapters
• PDA and Cellular Phone Battery Chargers
• Distributed Power Systems
• Automotive Aftermarket Electronics “MPS” and “The Future of Analog IC Technology” are Registered Trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION INPUT 6.5V to 32V OPEN NOT USED OUTPUT 2.5V 4.7nF 10nF MP1591 BSIN FB SW REF GND COMP EN OPEN OFF ON 100 EFFICIENCY (%) 0 0.5 1 1.5 2 LOAD CURRENT (A) Efficiency vs Load Current VOUT=5V VOUT=3.3V VIN=12V

MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER MP1591 Rev. 2.3 www.MonolithicPower.com 2 9/27/2006 MPS Proprietary Information. Unaut horized Photocopy and Duplication Prohibited. © 2006 MPS. All Rights Reserved. PACKAGE REFERENCE Part Number* Package Temperature MP1591DN SOIC8E –40°C to +85°C MP1591DS SOIC8 –40°C to +85°C * For Tape & Reel, add suffix –Z (eg. MP1591DN–Z) For RoHS Compliant Packaging, add suffix –LF (eg. MP1591DN–LF–Z) ABSOLUTE MAXIMUM RATINGS (1) Recommended Operating Conditions (2) Thermal Resistance (3) θJA θJC Notes: 1) Exceeding these ratings may damage the device. 2) The device is not guaranteed to function outside of its operating conditions. 3) Measured on approximately 1” square of 1 oz copper.

ELECTRICAL CHARACTERISTICS

VIN = 12V, TA = +25°C, unless otherwise noted. Parameter Symbol Condition Min Typ Max Units Shutdown Supply Current V EN = 0V 20 35 µA Supply Current V EN = 5V, VFB = 1.4V 1.0 1.2 mA Feedback Voltage 6.5V ≤ VIN ≤ 32V, VCOMP < 2V 1.202 1.230 1.258 V Error Amplifier Voltage Gain 400 V/V Error Amplifier Transconductance ∆IC = ±10µA 500 700 1100 µA/V High-Side Switch On Resistance (4) 120 m Ω Low-Side Switch On Resistance (4) 8.5 Ω High-Side Switch Leakage Current V EN = 0V, VSW = 0V 0 10 µA Current Limit (5) 2.5 3.6 4.9 A Current Sense to COMP Transconductance 3.5 A/V Oscillation Frequency 280 330 380 KHz Short Circuit Oscillation Frequency V FB = 0V 35 KHz Maximum Duty Cycle (4) V FB = 1.0V 90 % Minimum Duty Cycle (4) V FB = 1.5V 0 % EN Shutdown Threshold Voltage 0.8 1.2 1.6 V Enable Pull-Up Current V EN = 0V 1.8 µA EN UVLO Threshold V EN Rising 2.4 2.6 2.8 V EN UVLO Threshold Hysteresis 250 mV BS IN SW GND REF EN COMP FB TOP VIEW EXPOSED PAD ON BACKSIDE (SOIC8N ONLY) CONNECT TO PIN 4

MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER MP1591 Rev. 2.3 www.MonolithicPower.com 3 9/27/2006 MPS Proprietary Information. Unaut horized Photocopy and Duplication Prohibited. © 2006 MPS. All Rights Reserved. ELECTRICAL CHARACTERISTICS (continued) VIN = 12V, TA = +25°C, unless otherwise noted. Parameter Symbol Condition Min Typ Max Units Thermal Shutdown (4) 160 °C REF Voltage I REF = 0 5.0 V REF Load Regulation (4) ∆IREF = 0 to 1mA 100 mV REF Line Regulation (4) I REF = 100µA, VIN = 6.5 to 32V 30 mV Notes: 4) These parameters are guaranteed by design, not production tested. 5) Equivalent output current = 1.5A ≥ 50% Duty Cycle 2.0A ≤ 50% Duty Cycle Assumes ripple current = 30% of load current. Slope compensation changes current limit. PIN FUNCTIONS Pin # Name Description 1 BS High-Side Gate Drive Boost Input. BS supplies the drive for the high-side N-Channel MOSFET switch. Connect a 10nF or greater capacitor from SW to BS to power the high-side switch. 2 IN Power Input. IN supplies the power to the IC , as well as the step-down converter switches. Drive IN with a 6.5V to 32V power source. Bypass IN to GND with a suitably large capacitor to eliminate noise on the input to the IC. See Input Capacitor. 3 SW Power Switching Output. SW is the switchi ng node that supplies power to the output. Connect the output LC filter from SW to the output load. Note that a capacitor is required from SW to BS to power the high-side switch. 4 GND Ground. For the MP1591DN, co nnect the Exposed Pad to pin 4. 5 FB Feedback Input. FB senses the output voltage to regulate that voltage. Drive FB with a resistive voltage divider from the output voltage. The feedback threshold is 1.230V. See Setting the Output Voltage. 6 COMP Compensation Node. COMP is used to compensate the regulation control loop. Connect a series RC network from COMP to GND to compensate the regulation control loop. In some cases, an additional capacitor from COMP to GND is required. See Compensation. 7 EN Enable/UVLO. A voltage greater than 2.8V enables operation. For complete low current shutdown the EN pin voltage needs to be less than 800mV. 8 REF Reference Output. REF is the 5V reference vo ltage output. It can supply up to 1mA to external circuitry. If used, bypass REF to GND with 10nF or greater capacitor. Leave REF unconnected if not used.

MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER MP1591 Rev. 2.3 www.MonolithicPower.com 4 9/27/2006 MPS Proprietary Information. Unaut horized Photocopy and Duplication Prohibited. © 2006 MPS. All Rights Reserved. OPERATION The MP1591 is a current mode step-down regulator. It regulates input voltages from 6.5V to 32V down to an output voltage as low as 1.230V and is able to supply up to 2A of load current. The MP1591 uses current-mode control to regulate the output voltage. The output voltage is measured at FB through a resistive voltage divider and amplified through the internal error amplifier. The output current of the transconductance error amplifier is presented at COMP where a network compensates the regulation control system. The voltage at COMP is compared to the switch current measured internally to control the output voltage. The converter uses an internal N-Channel MOSFET switch to step-down the input voltage to the regulated output voltage. Since the MOSFET requires a gate voltage greater than the input voltage, a boost capacitor connected between SW and BS drives the gate. The capacitor is internally charged while SW is low. An internal 10 Ω switch from SW to GND is used to insure that SW is pulled to GND when the switch is off to fully charge the BS capacitor LOCKOUT COMPARATOR ERROR AMPLIFIER FREQUENCY FOLDBACK COMPARATOR INTERNAL REGULATORS 1.8V SLOPE COMP CLK CURRENT COMPARATOR CURRENT SENSE AMPLIFIER SHUTDOWN COMPARATOR COMP IN 2 EN 7 5 6 GND4 OSCILLATOR THERMAL PROTECTION 35/330KHz S R Q SW BS REF 5V8 Q 1.2V + + 2.60V/ 2.35V + 1.230V0.7V + FB Figure 1—Functional Block Diagram

MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER MP1591 Rev. 2.3 www.MonolithicPower.com 5 9/27/2006 MPS Proprietary Information. Unaut horized Photocopy and Duplication Prohibited. © 2006 MPS. All Rights Reserved.

APPLICATION INFORMATION

Setting the Output Voltage The output voltage is set using a resistive voltage divider from the output voltage to FB. The voltage divider divides the output voltage down by the ratio: )2R1R( 2RVV OUTFB +×= Where VFB is the feedback voltage and V OUT is the output voltage. Thus the output voltage is: )2R1R(230.1VOUT +×= A typical value for R2 can be as high as 100k Ω, but 10kΩ is recommended. Using that value, R1 is determined by: For example, for a 3.3V output voltage, R2 is 10kΩ, and R1 is 17kΩ. Inductor (L1) The inductor is required to supply constant current to the output load while being driven by the switched input voltage. A larger value inductor results in less ripple current that results in lower output ripple voltage. However, the larger value inductor has a larger physical size, higher series resistance, and/or lower saturation current. Choose an inductor that does not saturate under the worst-case load conditions. A good rule to use for determining the inductance is to allow the peak-to-peak ripple current in the inductor to be approximately 30% of the maximum load current that the IC can provide. Also, make sure that the peak inductor current (the load current plus half the peak-to-peak inductor ripple current) is below the 2.3A minimum current limit. The inductance value can be calculated by the equation: )IfV( )VV(V1L IN OUTIN OUT ∆×× −×= Where VIN is the input voltage, f is the switching frequency and ∆I is the peak-to-peak inductor ripple current. Table 1 lists a number of suitable inductors from various manufacturers. Table 1—Inductor Selection Guide Package Dimensions (mm) Vendor/ Model Core Type Core Material W L H Sumida CR75 Open Ferrite 7.0 7.8 5.5 CDH74 Open Ferrite 7.3 8.0 5.2 CDRH5D28 Shielded Ferrite 5.5 5.7 5.5 CDRH5D28 Shielded Ferrite 5.5 5.7 5.5 CDRH6D28 Shielded Ferrite 6.7 6.7 3.0 CDRH104R Shielded Ferrite 10.1 10.0 3.0 Toko D53LC Type A Shielded Ferrite 5.0 5.0 3.0 D75C Shielded Ferrite 7.6 7.6 5.1 D104C Shielded Ferrite 10.0 10.0 4.3 D10FL Open Ferrite 9.7 1.5 4.0 Coilcraft DO3308 Open Ferrite 9.4 13.0 3.0 DO3316 Open Ferrite 9.4 13.0 5.1 Input Capacitor (C1) The input current to the step-down converter is discontinuous, and so a capacitor is required to supply the AC current to the step-down converter while maintaining the DC input voltage. A low ESR capacitor is required to keep the noise at the IC to a minimum. Ceramic capacitors are preferred, but tantalum or low ESR electrolytic capacitors may also suffice.

MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER MP1591 Rev. 2.3 www.MonolithicPower.com 6 9/27/2006 MPS Proprietary Information. Unaut horized Photocopy and Duplication Prohibited. © 2006 MPS. All Rights Reserved. The input capacitor value should be greater than 10µF. The capacitor can be electrolytic, tantalum or ceramic. However, since it absorbs the input switching current it requires an adequate ripple current rating. Its RMS current rating should be greater than approximately 1/2 of the DC load current. For insuring stable operation C1 should be placed as close to the IC as possible. Alternately, a smaller high quality ceramic 0.1µF capacitor may be placed closer to the IC and a larger capacitor placed farther away. If using this technique, it is recommended that the larger capacitor be a tantalum or electrolytic type. All ceramic capacitors should be placed close to the MP1591. Output Capacitor (C5) The output capacitor is required to maintain the DC output voltage. Low ESR capacitors are preferred to keep the output voltage ripple low. The characteristics of the output capacitor also affect the stability of the regulation control system. Ceramic, tantalum or low ESR electrolytic capacitors are recommended. In the case of ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance, and so the output voltage ripple is mostly independent of the ESR. The output voltage ripple is estimated to be: SW LC INRIPPLE f fV4.1V ⎟⎟ ⎛××≅ Where VRIPPLE is the output ripple voltage, f LC is the resonant frequency of the LC filter, fSW is the switching frequency. In the case of tantalum or low-ESR electrolytic capacitors, the ESR dominates the impedance at the switching frequency, and so the output ripple is calculated as: ESRRIPPLE RIV ×∆≅ Where V RIPPLE is the output voltage ripple and RESR is the equivalent series resistance of the output capacitors. Output Rectifier Diode (D1) The output rectifier diode supplies the current to the inductor when the high-side switch is off. To reduce losses due to the diode forward voltage and recovery times, use a Schottky rectifier. Table 2 provides some recommended Schottky rectifiers based on the maximum input voltage and current rating. Table 2—Diode Selection Guide 2A Load Current 3A Load Current VIN (Max) Part Number Vendor Part Number Vendor 15V 30BQ15 4 B220 1 B320 1 SK23 6 SK33 1, 6 20V SR22 6 SS32 3 20BQ030 4 B330 1 B230 1 B340L 1 SK23 6 MBRD330 4, 5 SR23 3, 6 SK33 1, 6 30V SS23 2, 3 SS33 2, 3 21DQ04 4 B340L 1 MBRS240L 5 MBRS340 4 SK24 6 SK34 1, 6 34V SS24 2, 3 SS34 2, 3 Table 3 lists manufacturer’s websites. Table 3—Schottky Diode Manufacturers # Vendor Web Site 1 Diodes, Inc. www.diodes.com 2 Fairchild Semiconductor www.fairchildsemi.com 3 General Semiconductor www.gensemi.com 4 International Rectifier www.irf.com 5 On Semiconductor www.onsemi.com 6 Pan Jit International www.panjit.com.tw Choose a rectifier whose maximum reverse voltage rating is greater than the maximum input voltage, and whose current rating is greater than the maximum load current.

MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER MP1591 Rev. 2.3 www.MonolithicPower.com 7 9/27/2006 MPS Proprietary Information. Unaut horized Photocopy and Duplication Prohibited. © 2006 MPS. All Rights Reserved. Compensation The system stability is controlled through the COMP pin. COMP is the output of the internal transconductance error amplifier. A series capacitor-resistor combination sets a pole-zero combination to control the characteristics of the control system. The DC loop gain is: LOADCSVEA OUT REF VDC RGAV VA ×××= Where V REF is the feedback threshold voltage, 1.230V, A VEA is the transconductance error amplifier voltage gain, 400 V/V, and G CS is the current sense gain (roughly the output current divided by the voltage at COMP), 3.5 A/V. The system has 2 poles of importance; one is due to the compensation capacitor (C4) and the other is due to the output capacitor (C5). These are: )4CA2( Gf VEA MEA 1P ××π= Where fP1 is the first pole, and G MEA is the error amplifier transconductance (770µS) and )5CR2( LOAD 2P ××π= The system has one zero of importance due to the compensation capacitor (C4) and the compensation resistor (R3) which is )4C3R2( 1f 1Z ××π= If large value capacitors with relatively high equivalent-series-resistance (ESR) are used, the zero due to the capacitance and ESR of the output capacitor can be compensated by a third pole set by R3 and C3 )3C3R2( 1f 3P ××π= The system crossover frequency f C, (the frequency where the loop gain drops to 1, or 0dB) is important. A good rule of thumb is to set the crossover frequency to approximately one tenth of the switching frequency. In this case, the switching frequency is 330KHz, so use a crossover frequency of 33KHz. Lower crossover frequencies result in slower response and worse transient load recovery. Higher crossover frequencies can result in instability. Choosing the Compensation Components The values of the compensation components given in Table 4 yield a stable control loop for the output voltage and given capacitor. Table 4—Compensation Values for Typical Output Voltage/Capacitor Combinations VOUT C5 R3 C3 C4 2.5V 22µF Ceramic 3.9k Ω None 4.7nF 3.3V 22µF Ceramic 5.1k Ω None 3.9nF 5V 22µF Ceramic 7.5k Ω None 2.7nF 12V 22µF Ceramic 18k Ω None 1.2nF 2.5V 47µF SP-Cap 8.2k Ω None 2.2nF 3.3V 47µF SP-Cap 10k Ω None 2.2nF 5V 47µF SP-Cap 16k Ω None 1.5nF 12V 47µF SP-Cap 36k Ω None 1nF 2.5V 560µF/6.3V, AL 30mΩ ESR 100kΩ 150pF 1nF 3.3V 560µF/6.3V, AL 30mΩ ESR 120kΩ 120pF 1nF 5V 470µF/10V, AL 30mΩ ESR 150kΩ 82pF 1nF 12V 220µF/25V, AL 30mΩ ESR 180kΩ 33pF 1nF Note: “AL” = Electrolytic

MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER MP1591 Rev. 2.3 www.MonolithicPower.com 8 9/27/2006 MPS Proprietary Information. Unaut horized Photocopy and Duplication Prohibited. © 2006 MPS. All Rights Reserved. To optimize the compensation components that are not listed in Table 4, use the following procedure. Choose the compensation resistor to set the desired crossover frequency. Determine the value by the following equation: REFCSEA COUT VGG fV5C23R ×× ×××π= Putting in the know constants and setting the crossover frequency to the desired 33KHz: OUT 7 V5C1088.63R ×××≅ Choose the compensation capacitor to set the zero below one fourth of the crossover frequency. Determine the value by the following equation: 1093.1 f3R 24C C Determine if the second compensation capacitor, C3, is required. It is required if the ESR zero of the output capacitor occurs at less than four times the crossover frequency, or 1fR5C8 CESR ≥×××π If this is the case, then add the second compensation resistor. Determine the value by the equation: R5C )MAX(ESR× Where R ESR(MAX) is the maximum ESR of the output capacitor. Example: VOUT = 5V, C5 = 22µF Ceramic (ESR = 10mΩ) R3 ≈ 6.88x107 (22x10-6) (5) = 7568Ω Use the nearest standard value of 7.5kΩ. C4 > 1.93x10-5 / 7.5K = 2.57nF Use standard value of 2.7nF. 8π x C5 x R ESR x fC = 0.22, which is less than 1. Therefore, no second compensation capacitor (C3) is required. External Bootstrap Diode It is recommended that an external bootstrap diode be added when the system has a 5V fixed input or the power supply generates a 5V output. This helps improve the efficiency of the regulator. The bootstrap diode can be a low cost one such as IN4148 or BAT54. MP1591 SW BS 10nF Figure 2—External Bootstrap Diode This diode is also recommended for high duty cycle operation (when IN OUT V V >65%) and high output voltage (VOUT>12V) applications.

MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER MP1591 Rev. 2.3 www.MonolithicPower.com 10 9/27/2006 MPS Proprietary Information. Unaut horized Photocopy and Duplication Prohibited. © 2006 MPS. All Rights Reserved.

PACKAGE INFORMATION

0.016(0.41) 0.050(1.27)0o-8o DETAIL "A" 0.010(0.25) 0.020(0.50) x 45 o SEE DETAIL "A" 0.0075(0.19) 0.0098(0.25) 0.150(3.80) 0.157(4.00)PIN 1 ID 0.050(1.27) BSC 0.013(0.33) 0.020(0.51) SEATING PLANE 0.004(0.10) 0.010(0.25) 0.189(4.80) 0.197(5.00) 0.053(1.35) 0.069(1.75) TOP VIEW FRONT VIEW 0.228(5.80) 0.244(6.20) SIDE VIEW RECOMMENDED LAND PATTERN 0.213(5.40) 0.063(1.60) NOTE: 1) CONTROL DIMENSION IS IN INCHES. DIMENSION IN BRACKET IS IN MILLIMETERS. 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. 3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. 4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.004" INCHES MAX. 5) DRAWING CONFORMS TO JEDEC MS-012, VARIATION AA. 6) DRAWING IS NOT TO SCALE. 0.010(0.25) BSC GAUGE PLANE

MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER 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 w hen integrating MPS products into any application. MPS will not assume any legal responsibility for any said applications. MP1591 Rev. 2.3 www.MonolithicPower.com 11 9/27/2006 MPS Proprietary Information. Unaut horized Photocopy and Duplication Prohibited. © 2006 MPS. All Rights Reserved. SOIC8E (WITH EXPOSED PAD) SEE DETAIL "A" 0.0075(0.19) 0.0098(0.25) 0.050(1.27) BSC 0.013(0.33) 0.020(0.51) SEATING PLANE 0.000(0.00) 0.006(0.15) 0.051(1.30) 0.067(1.70) TOP VIEW FRONT VIEW SIDE VIEW BOTTOM VIEW NOTE: 1) CONTROL DIMENSION IS IN INCHES. DIMENSION IN BRACKET IS IN MILLIMETERS. 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. 3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. 4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.004" INCHES MAX. 5) DRAWING CONFORMS TO JEDEC MS-012, VARIATION BA. 6) DRAWING IS NOT TO SCALE. 0.089(2.26) 0.101(2.56) 0.124(3.15) 0.136(3.45) RECOMMENDED LAND PATTERN 0.213(5.40) 0.063(1.60) 0.103(2.62) 0.138(3.51) 0.150(3.80) 0.157(4.00)PIN 1 ID 0.189(4.80) 0.197(5.00) 0.228(5.80) 0.244(6.20)14 0.016(0.41) 0.050(1.27)0o-8o DETAIL "A" 0.010(0.25) 0.020(0.50) x 45o 0.010(0.25) BSC GAUGE PLANE