EUP3410

EUP3410/3411 2A,16V,380KHz Step-Down Converter DESCRIPTION The EUP3410/3411 is a current mode, step-down switching regulator capable of driving 2A continuous load with excellent line and load regulation. The EUP3410/3411 can operate with an input voltage range from 4.5V to 16V and the output can be externally set from 1.2V to 12V with a resistor divider. Fault condition protection includes cycle-by-cycle current limiting and thermal shutdown. In shutdown mode the regulator draws 25µA of supply current. The EUP3410/3411 requires a minimum number of external components. FEATURES 30V Input Surge Protection Up to 2A Output Current 0.17Ω Internal DMOS Output Switch 4.5V to 16V Input Operating Range Output Adjustable from 1.2V to 12V Up to 95% Efficiency 25µA Shutdown Current Fixed 380KHz Frequency Thermal Shutdown and Overcurrent Protection Input Supply Overvoltage and Undervoltage Lockout Available in SOP-8 & MSOP-10 Packages RoHS Compliant and 100% Lead(Pb)-Free APPLICATIONS PC Monitors Distributed Power Systems Networking Systems Portable Electronics Typical Application Circuit Figure 1. Typical Application Circuit with Ceramic Capacitors DS3410/3411 Ver1.2 Nov. 2008 1 EUP3410/3411 Typical Application Circuit (continued) Figure 2. Typical Application Circuit with Electrolytic Capacitors Block Diagram Figure 3. Functional Block Diagram DS3410/3411 Ver1.2 Nov. 2008 2 EUP3410/3411 Pin Configurations Package Type Pin Configurations Package Type Pin Configurations SOP-8 MSOP-10 Pin Description Pin Name BS EUP3410 1 EUP3411 2 DESCRIPTION High-Side Gate Driver Boostrap Supply. BS provides power to the gate driver of high-side n-channel MOSFET switch. Connect a 10nF or greater capacitor from SW to BS. Input Supply Pin. IN supplies the power to the IC and the high side power switch. Connect IN to a 4.5V to 16V power source. Bypass IN to GND with a suitably large value capacitor to minimize input ripple to the IC. See Input Capacitor Section of the applications notes. Power Switcher Output. Connect the output LC filter from SW to the output. Ground. Output Feedback Input. FB senses the output voltage to regulate that voltage. Connect FB to an external resistor divider to set the output voltage. The feedback threshold is 1.2V. See Setting the Output Voltage. Loop compensation pin. Connect a series RC network from COMP to GND to compensate the regulation control loop. See Compensation. Enable Input. EN is a logic input that controls the regulator on or off. Drive EN logic high to turn on the regulator, and set EN logic low to turn it off. For automatic startup, leave EN unconnected and EN is pulled high by an internal current source to enable the device. No Connect Soft-Start pin. Connect SS to an external capacitor to program the soft-start time. If the pin is not used, leave it open. IN SW GND FB COMP 2 3 4 5 6 4 5 6 7 8 EN NC SS 7 8 - 9 1,3 10 DS3410/3411 Ver1.2 Nov. 2008 3 EUP3410/3411 Ordering Information Order Number Package Type Marking Operating Temperature Range EUP3410DIR1 EUP3411MIR1 SOP-8 MSOP-10 xxxxx P3410 xxxxx 3411A -40°C to +85°C -40 °C to +85°C EUP3410/3411 □ □□□ Lead Free Code 1: Lead Free 0: Lead Packing R: Tape & Reel Operating temperature range I: Industry Standard Package Type D: SOP M: MSOP DS3410/3411 Ver1.2 Nov. 2008 4 EUP3410/3411 Absolute Maximum Ratings (1) Input Voltage (VIN) ------------------------------------------------------------ -0.3V to 30V Switch Voltage (VSW) ------------------------------------------------------ -1V to VIN +0.3V Boot Strap Voltage (VBS) ------------------------------------------------ VSW-0.3V to VSW +6V All Other Pins --------------------------------------------------------------------- -0.3V to 6V Junction Temperature ------------------------------------------------------------------- 150°C Storage Temperature ------------------------------------------------------ -65°C to +150°C Lead Temp (Soldering, 10sec) ------------------------------------------------------260°C Thermal Resistance θJA (SOP-8) ----------------------------------------------------- 90°C/W Thermal Resistance θJA (MSOP-10) --------------------------------------------- 61.11°C/W Recommend Operating Conditions (2) Supply Voltage (VIN) ------------------------------------------------------------- 4.5V to 16V Operating Temperature Range ----------------------------------------------- -40°C to +85°C Note (1): Stress beyond those listed under “Absolute Maximum Ratings” may damage the device. Note (2): The device is not guaranteed to function outside the recommended operating conditions Electrical Characteristics Unless otherwise specified, VEN=5V, VIN=12V ,TA=+25°C. Parameter Feedback Voltage Upper Switch On Resistance Lower Switch On Resistance Upper Switch Leakage Switch Peak Current Limit Oscillator Frequency Short Circuit Frequency Maximum Duty Cycle Minimum Duty Cycle Enable Threshold Input Undervoltage Lockout Threshold Rising Input Undervoltage Lockout Threshold Hysteresis Input Overvoltage Lockout Threshold Shutdown Supply Current Operating Supply Current Soft-Start Current (EUP3411) Thermal Shutdown Conditions 4.5V ≤ VIN ≤ 16V EUP3410/3411 Min Typ Max 1.162 1.200 0.17 6.8 3 380 45 90 0 0.95 2.5 110 1.236 Unit V Ω Ω µA A KHz KHz % % V V mV VEN=0V, VSW=0V 2.4 320 VFB=0V VFB=1V VFB=1.5V 0.7 2 5 440 1.4 3 VEN=0V VFB=1.4V VSS=0V 22 25 0.45 5.2 160 36 0.7 V µA mA uA °C DS3410/3411 Ver1.2 Nov. 2008 5 EUP3410/3411 Typical Operating Characteristics See Figure 2.C1=390uF, C2=0.22uF, C6=0.22uF, C7=560uF, L=15uH, TA= +25℃. DS3410/3411 Ver1.2 Nov. 2008 6 EUP3410/3411 Typical Operating Characteristics See Figure 2.C1=390uF, C2=0.22uF, C6=0.22uF, C7=560uF, L=15uH, TA= +25℃. (EUP3410) (EUP3410) (EUP3411) (EUP3411) DS3410/3411 Ver1.2 Nov. 2008 7 EUP3410/3411 Typical Operating Characteristics See Figure 2.C1=390uF, C2=0.22uF, C6=0.22uF, C7=560uF, L=15uH, TA= +25℃. DS3410/3411 Ver1.2 Nov. 2008 8 EUP3410/3411 Functional Description The EUP3410/3411 is a current-mode step-down switching regulator. The device regulates an output voltage as low as 1.2V from a 4.5V to 16V input power supply. The device can provide up to 2Amp continuous current to the output. The EUP3410/3411 uses current-mode architecture to control the regulator loop. 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 pin where a RC network compensates the regulator loop. Slope compensation is internally added to eliminate subharmonic oscillation at high duty cycle. The slope compensation adds voltage ramp to the inductor current signal which reduces maximum inductor peak current at high duty cycles. The device uses an internal Hside n-channel switch to step down the input voltage to the regulated output voltage. Since the Hside n-channel switch requires gate voltage greater than the input voltage, a boostrap BS capacitor is connected between SW and BS to drive the n-channel gate. The BS capacitor is internally charged while the switch is off. An internal 6.8Ω switch from SW to GND is added to insure that SW is pulled to GND when the switch is off to fully charge the BS capacitor. current (the load current plus half the peak-to-peak inductor ripple current) is below the 2.4A minimum peak current limit. The inductance value can be calculated by the equation: L = (VOUT ) ∗ (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. Input Capacitor The input current to the step-down converter is discontinuous, and therefore an input capacitor C1 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 minimum at the IC. Ceramic capacitors are preferred, but tantalum or low-ESR electrolytic capacitors may also suffice. The input capacitor value should be greater than 10µF, and the RMS current rating should be greater than approximately 1/2 of the DC load current. In Figure 2, for insuring stable operation C2 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 further away. If using this technique, it is recommended that the larger capacitor type are either tantalum or electrolytic. In Figure 1, all ceramic capacitors should be placed close to the EUP3410/3411. 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. The characteristics of the output capacitor also affect the stability of the regulator control loop. 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. The output voltage ripple is estimated to be: Application Information Setting the Output Voltage The output voltage is set through a resistive voltage divider (see Figure1 or 2). The voltage divider divides the output voltage down by the ratio: VFB = VOUT ∗ R 3 / (R 2 + R 3) = 1.2 V Thus the output voltage is : VOUT = 1.2 V ∗ (R 2 + R 3) / R 3 Choose R3 value in the range 10k to 100k, R2 is determined by : R 2 = (VOUT / 1.2 − 1) ∗ R 3 For example, for a 3.3V output voltage, R3 is 10KΩ, and R2 is 17.5KΩ. 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 results in less ripple current and lower output ripple voltage. However, the larger value inductor has a larger physical size, higher series resistance, and lower saturation current. Choose an inductor that does not saturate under the worst-case load conditions. A good rule 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. Also, make sure that the peak inductor DS3410/3411 Ver1.2 Nov. 2008 VRIPPLE ~ = 1.4 ∗ VIN ∗ (f LC / f )∧ 2 Where VRIPPLE is the output ripple voltage, VIN is the input voltage, fLC is the resonant frequency of the LC filter, f is the switching frequency. In the case of tanatalum or low ESR electrolytic capacitors, the ESR dominates the impedance at the switching frequency, and so the output ripple is calculated as: VRIPPLE ~ = ∆I ∗ R ESR Where VRIPPLE is the output voltage ripple, ∆I is the inductor ripple current, and RESR is the equivalent series resistance of the output capacitors. 9 EUP3410/3411 Output Rectifier Diode The output rectifier diode supplies the current to the inductor when the high-side switch is off. A schottky diode is recommended to reduce losses due to the diode forward voltage and recovery times. Loop 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 feedback loop. The DC loop gain is: crossover frequency, fC, of 40KHz. Lower crossover frequency results in slower loop response and poor load transient performance. Higher crossover frequency can result in loop instability. Table 1. Compensation Values for Typical Output Voltage /Capacitor Combinations VOUT 2.5V 3.3V 5V 12V 2.5V 3.3V 5V 12V C7 22µF Ceramic 22µF Ceramic 22µF Ceramic 22µF Ceramic 560µF/6.3V (30mΩ ESR) 560µF/6.3V (30mΩ ESR) 470µF/10V (30mΩ ESR) 220µF/25V (30mΩ ESR) R1 10KΩ 10KΩ 10KΩ 10KΩ 10KΩ 10KΩ 10KΩ 10KΩ C5 3.9nF 3.9nF 3.9nF 3.9nF 30nF 39nF 47nF 56nF C4 None None None None None None None None A VDC = (VFB / VOUT ) ∗ A VEA ∗ G CS ∗ R LOAD Where: VFB is the feedback threshold voltage, 1.2V VOUT is the desired output regulation voltage AVEA is the transconductance error amplifier voltage gain, 400 V/V GCS is the current sense gain, (roughly the output current divided by the voltage at COMP), 2A/V RLOAD is the load resistance (VOUT / IOUT where IOUT is the output load current) The system has 2 poles. One is due to the compensation capacitor (C5), and the other is due to the output capacitor (C7). These are: The values of the compensation components listed in Table 1 yield a stable control loop for the given output voltage. f P1 = G EA / (2 π ∗ A VEA ∗ C5 ) Where P1 is the first pole, and GEA is the error amplifier transconductance (660µA/V). and f P 2 = 1 / (2 π ∗ R LOAD ∗ C 7 ) The system has one zero of importance, due to the compensation capacitor (C5) and the compensation resistor (R1). The zero is: f Z1 = 1 / (2 π ∗ R1 ∗ C5 ) If a large value capacitor (C7) with relatively high equivalent-series-resistance (ESR) is used, the zero due to the capacitance and ESR of the output capacitor can be compensated by a third pole set by R1 and C4. The pole is: f P3 = 1/ (2π ∗ R1 ∗ C4 ) The system crossover frequency (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 1/10 of the switching frequency. In this case, the switching frequency is 380KHz, therefore use a DS3410/3411 Ver1.2 Nov. 2008 10 EUP3410/3411 Packaging Information SOP-8 SYMBOLS A A1 D E E1 L b e MILLIMETERS MIN. 1.35 0.10 4.90 5.80 3.90 0.40 0.31 1.27 1.27 0.51 6.20 0.228 MAX. 1.75 0.25 MIN. INCHES MAX. 0.069 0.010 0.193 0.244 0.153 0.016 0.012 0.050 0.050 0.020 0.053 0.004 DS3410/3411 Ver1.2 Nov. 2008 11 EUP3410/3411 MSOP-10 SYMBOLS A A1 D E1 E L b e D1 E2 MILLIMETERS MIN. MAX. 1.10 0.00 0.15 3.00 3.00 4.70 5.10 0.40 0.80 0.17 0.33 0.50 1.80 1.66 INCHES MIN. 0.000 0.118 0.118 0.185 0.016 0.006 0.020 0.071 0.065 0.201 0.031 0.013 MAX. 0.043 0.006 DS3410/3411 Ver1.2 Nov. 2008 12