MP1410

MP1410 MPS | Alldatasheet

Document overview

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Technical content

Features

/square4 2A Output Current /square4 0.18Ω Internal Power MOSFET Switch /square4 Stable with Low ESR Output Ceramic capacitors /square4 Up to 95% Efficiency /square4 20uA Shutdown Mode /square4 Fixed 380kHz frequency /square4 Thermal Shutdown /square4 Cycle-by-cycle over current protection /square4 Wide 4.75 to 15V operating input range /square4 Output Adjustable from 1.22 to 13V /square4 Programmable under voltage lockout /square4 Available in 8 pin SO /square4 Evaluation Board Available

Applications

/square4 PC Monitors /square4 Distributed Power Systems /square4 Battery Charger /square4 Pre-Regulator for Linear Regulators Figure 1: Typical Application Circuit 0 0.5 1 1.5 2 Output Current (A) Efficiency (%) 5.0V 3.3V 2.5V 4.75 to 15V INPUT ENABLE SHUTDOWN OUTPUT 2.5V/2A MP1410 Efficiency versus Output Current and Voltage. VIN=10V

MP1410 Rev 1.0_ 05/29/02 www.monolithicpower.com 2 Monolithic Power Systems Absolute Maximum Ratings (Note 1) Recommended Operating Conditions (Note 2) IN Voltage -0.3V to 16V IN Input Voltage 4.75V to 15V SW Voltage -1V to VIN +1V Operating Temperature -20°C to +85°C BS Voltage V SW-0.3V toVSW+6V All Other Pins –0.3 to 6V Junction Temperature 150°C Lead Temperature 260°C Package Thermal Characteristics (Note 3) Storage Temperature -65°C to 150°C θJA (8 pin SOIC) 105°C/W Electrical Characteristics (Unless otherwise specified Circuit of Figure1, V EN=5V, VIN=12V, TA=25 C) Parameters Condition Min Typ Max Units Feedback Voltage 4.75V ≤ VIN ≤ 25V 1.184 1.222 1.258 V Upper Switch On Resistance 0.25 Ω Lower Switch On Resistance 10 Ω Upper Switch Leakage V EN=0V; VSW=0V 10 µA Current Limit 2.4 2.95 A Oscillator Frequency 320 380 440 KHz Short Circuit Frequency FB = 0V 42 KHz Maximum Duty Cycle FB = 1.0V 90 % Minimum Duty Cycle FB = 1.5V 0 % Enable Threshold 0.7 1.0 1.3 V Under Voltage Lockout Threshold High Going 2.0 2.5 3.0 V Under Voltage Lockout Threshold Hysteresis 200 mV Shutdown Supply current V EN=0V 25 50 µA Operating Supply current V EN=0V; VFB =1.4V 1.0 1.5 mA Thermal Shutdown 160 °C Note 1. Exceeding these ratings may damage the device. Note 2. The device is not guaranteed to function outside its operating rating. Note 3. Measured on 1” square of 1 oz. copper FR4 board.

MP1410 Rev 1.0_ 05/29/02 www.monolithicpower.com 3 Monolithic Power Systems Figure 2: Functional Block Diagram Σ 40/400KHz Oscillator Slope Compensation 1.8V Current Comparator Internal Regulators 1uA 2.30/2.53V 0.7V Shutdown Comparator Lockout Comparator 1.22V Error Amplifier gm= 630uA/Volt IN EN COMP FB GND SW BS1 0.7VFrequency Foldback Comparator CLK S R Q Q Current Sense Amplifier Pin Description # Name Description 1 BS High-Side Gate Drive Boost Input. BS supplies the drive for the high-side n-channel MOSFET switch. Connect a 0.1µF 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 4.75V to 15V 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 switching 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. 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 1.22V. 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. See Compensatiionr. 7 EN Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the regulator, drive it low to turn it off. For automatic startup, leave EN unconnected.

8 N/C No Connect

MP1410 Rev 1.0_ 05/29/02 www.monolithicpower.com 4 Monolithic Power Systems Functional Description The MP1410 is a current-mode step-down switch-mode regulator. It regulates input voltages from 4.75V to 15V down to an output voltage as low as 1.22V, and is able to supply up to 2A of load current. The MP1410 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 the switch is off. 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.

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: V FB = VOUT * R2 / (R1 + R2). Thus the output voltage is: V A typical value for R2 can be as high as 100k, but a typical value is 10k Ω. Using that value, R1 is determined by: For example, for a 3.3V output voltage, R2 is 10kΩ, and R1 is 17kΩ. Input Capacitor 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. 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 C IN should be placed as close to the IC as possible. Alternately a smaller high quality ceramic 0.1uF capacitor may be placed closer to the IC and a larger capacitor placed further away. If using this technique, it is recommended that the larger capacitor be a tantalum or electrolytic type. All ceramic capacitors should be places close to the MP1410. Output Capacitor The output capacitor is required to maintain the DC output voltage. Low ESR capacitors are preferred to keep the output voltage ripple low.

MP1410 Rev 1.0_ 05/29/02 www.monolithicpower.com 5 Monolithic Power Systems Application Information (Continued) The characteristics of the output capacitor also effect 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: V RIPPLE ~= 1.4 * VIN * (fLC/fSW)^2 Where V RIPPLE is the output ripple voltage, V IN is the input voltage, f LC is the resonant frequency of the LC filter, f SW 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: V RIPPLE ~= ∆I * RESR Where VRIPPLE is the output voltage ripple, ∆I is the inductor ripple current, and R ESR is the equivalent series resistance of the output capacitors. Output Rectifier Diode 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. Choose a rectifier who’s maximum reverse voltage rating is greater than the maximum input voltage, and who’s current rating is greater than the maximum load current. Table 1 provides a list of manufacturer’s and their websites. Table 1: Schottky Diode Manufacturers # Manufacturer Website 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 Compensation The output of the transconductance error amplifier is used to compensate the regulation system. Typically compensation capacitors, CC sets the dominant pole. The compensation resistor sets a zero that should have the same frequency as the pole set by the load resistance and the output capacitor. If the output capacitor is not ceramic type, then there may need to be another capacitor from COMP to GND (C CA) to compensate for the zero produced by the output capacitor and its ESR. One of the critical parameters is the DC loop gain. This can be determined by the equation: A VL = (VFB / VOUT) * AEA * ACS * RL Where AVL is the loop gain, VFB is the feedback threshold, 1.22V, V OUT is the regulated output voltage, AEA is the error amplifier voltage gain, ACS is the current sense gain, and R L is the load resistance, or VOUT / ILOAD. Simplifying the equation: AVL = A EA * A CS * (V FB / I LOAD(MAX)) ~= 1663 / ILOAD(MAX) Another critical parameter is the desired crossover frequency.

MP1410 Rev 1.0_ 05/29/02 www.monolithicpower.com 6 Monolithic Power Systems Application Information (Continued) This should be approximately one-fifth of the switching frequency or approximately f C = 75kHz. This and the loop gain determines the frequency of the dominant pole, f P1 = f C / A VL. The dominant pole occurs when GM / 2* π * fP1 * C C = A EA, where G M is the error amplifier transconductance. This CC can be determined by: CC ~= 306 * AVL / fC ~= 6.8 / ILOAD(MAX) (nF). The zero of the compensation network is determined by the compensation resistor RC. RC should be at the same frequency as the pole due to the output capacitor and the load resistor. Or: R C * CC = RL * COUT Solving for RC: RC = RL * COUT / CC = VOUT * COUT / ILOAD(MAX) * CC If non-ceramic capacitors are used, the second compensation capacitor is required to compensate for the zero formed from the capacitor and its ESR. The second compensation capacitor can be determined by: R C * CCA = COUT * RESR Solving for CCA: CCA = COUT * RESR / RC. Inductor The inductor is required to supply constant current to the output load while being driven by the switched input voltage. A larger value inductor will result in less ripple current that will result in lower output ripple voltage. However, the larger value inductor will have a larger physical size, higher series resistance, and/or lower saturation current. Choose an inductor that will not saturate under the worst-case load conditions. Table 2 provides a list of manufacturer’s and their websites. Table 2: Inductor Manufacturers # Manufacturer Website 1 Sumida Corporation www.sumida.com 2 Toko, Inc. www.toko.com 3 Coilcraft, Inc. www.coilcraft.com A good rule for determining the inductance to use, is to allow the peak-to-peak ripple current in the inductor to be approximately 30% of the maximum load current. Also, make sure that the peak inductor current (the load current plus half the peak-to-peak inductor ripple current) is below the 2.4A minimum current limit. The inductance value can be calculated by the equation: L = (V OUT) * (VIN-VOUT) / VIN * f * ∆I Where VOUT is the output voltage, VIN is the input voltage, f is the switching frequency, and ∆I is the peak-to-peak inductor ripple current. Table 3 gives a list of inductors for the various inductor manufacturers.

MP1410 Rev 1.0_ 05/22/02 www.monolithicpower.com 7 Monolithic Power Systems Table 3: Inductor Selection Guide Vendor/Model Value (uH) Max IDC (A) Max DCR (Ω) Core Type Core Material Package Dimensions (mm) W L H Sumida Toko Coilcraft

Figure 3. MP1410 with Murata 22uF/10V Ceramic Output Capacitor

MP1410 Rev 1.0 Monolithic Power Systems, Inc. 9 05/29/02 3777 Stevens Creek Blvd, Suite 400, Santa Clara, CA 95051-7364 USA © 2002 MPS, Inc. Tel: (408) 243-0088, Fax: (408) 243-0099, Web: www.monolithicpower.com Monolithic Power Systems Packaging SOIC 8 Pin NOTE: 1) Control dimension is in inches. Dimension in bracket is millimeters. 0.016(0.410) 0.050(1.270) 0o-8o DETAIL "A" 0.011(0.280) 0.020(0.508) x 45o SEE DETAIL "A" 0.0075(0.191) 0.0098(0.249) 0.229(5.820) 0.244(6.200) SEATING PLANE 0.0040(0.102) 0.0098(0.249) 0.189(4.800) 0.197(5.004) 0.053(1.350) 0.068(1.730) 0.049(1.250) 0.060(1.524) 0.150(3.810) 0.157(4.000) PIN 1 IDENT. 0.050(1.270)BSC 0.013(0.330) 0.020(0.508) PDIP 8 Pin NOTICE: MPS believes the information in this document to be accurate and reliable. However, it is subject to change without notice. Please contact the factory for current specifications. No responsibility is assumed by MPS for its use or fit to any application, nor for infringement of patent or other rights of third parties.