芯美电子 Preliminary EUP3409 Dual 1.5MHz, 800mA Synchronous Step-Down Converter DESCRIPTION FEATURES The EUP3409 contains two independent 1.5MHz constant frequency, current mode, PWM step-down converters. Each converter integrates a main switch and a synchronous rectifier for high efficiency without an external Schottky diode. The EUP3409 is ideal for powering portable equipment that runs from a single cell Lithium-Ion (Li+) battery. Each converter can supply 800mA of load current from a 2.5V to 5.5V input voltage. The output voltage can be regulated as low as 0.6V. The EUP3409 can also run at 100% duty cycle for low dropout applications. z z z z z z z z z z z z z Up to 95% Efficiency 1.5MHz Constant Switching Frequency 800mA Load Current on Each Channel 2.5V to 5.5V Input Voltage Range Output Voltage as Low as 0.6V 100% Duty Cycle in Dropout Current Mode Operation Short Circuit Protection Thermal Fault Protection <1µA Shutdown Current Soft Start Function Space Saving 10-Pin QFN Package RoHS Compliant and 100% Lead(Pb)-Free APPLICATIONS z z z z z Cellular and Smart Phones Microprocessors and DSP Core Supplies PDAs and Portable Media Players Wireless and DSL Modems Digital Still and Video Cameras Typical Application Circuit Figure 1. DS3409 Ver0.1 May. 2007 1 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 Preliminary EUP3409 Block Diagram Figure 2. Pin Configurations Package Type Pin Configurations TDFN-10 Pin Description PIN Pin EN1 1 FB1 2 IN2 3 GND2 4 SW2 5 EN2 6 FB2 7 IN1 8 GND1 9 SW1 10 DS3409 Ver0.1 May. 2007 DESCRIPTION Channel 1 Enable Control Input. Drive EN1 above 1.5V to turn on the Channel 1. Drive EN1 below 0.3V to turn it off (shutdown current < 0.1µA). Channel 1 Feedback Input. Connect FB1 to the center point of the external resistor divider. Normal voltage for this pin is 0.6V. Channel 2 Supply Input. Ground 2. Channel 2 Switch Node Connection to Inductor. This pin connects to the drains of the internal main and synchronous power MOSFET switches. Channel 2 Enable Control Input. Drive EN2 above 1.5V to turn on the Channel 2. Drive EN2 below 0.3V to turn it off (shutdown current < 0.1µA). Channel 2 Feedback Input. Connect FB2 to the center point of the external resistor divider. Normal voltage for this pin is 0.6V. Channel 1 Supply Input. Ground 1. Channel 1 Switch Node Connection to Inductor. This pin connects to the drains of the internal main and synchronous power MOSFET switches. 2 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 Preliminary EUP3409 Ordering Information Order Number Package Type Marking Operating Temperature range EUP3409JIR1 TDFN-10 xxxxx P3409 20 -40 °C to 85°C EUP3409 □ □ □ □ Lead Free Code 1: Lead Free 0: Lead Packing R: Tape & Reel Operating temperature range I: Industry Standard Package Type J: TDFN DS3409 Ver0.1 May. 2007 3 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUP3409 Preliminary Absolute Maximum Ratings VIN1/IN2 to GND ---------------------------------------------------------------------- -0.3V to 6V VSW1/SW2 to GND ------------------------------------------------------------ -0.3V to VIN+0.3V VFB1/FB2 ,VEN1/EN2 to GND ---------------------------------------------------------- -0.3V to 6V Junction Temperature --------------------------------------------------------------------- 150°C Storage Temperature ----------------------------------------------------------- -65°C to 150°C Lead Temp (Soldering, 10sec) ------------------------------------------------------260°C Recommended Operating Conditions Supply Voltage, VIN1/IN2 ---------------------------------------------------------- 2.5V to 5.5V Output Voltage, VOUT1/OUT2 ------------------------------------------------------ 0.6V to 5.5V Operating Temperature -------------------------------------------------------- -40°C to 85°C Electrical Characteristics VIN1/IN2 =VEN1/EN2 =3.6V, TA=25°C, Unless otherwise specified. Symbol Parameter VIN Input Voltage Range IVFB Feedback Current IQ ISHDN Conditions 2.5 Each converter Supply Current VFB1/FB2=0.5V, SW1/SW2 Open VIN1/IN2=3V,VFB1/FB2=0.5V VFB Regulator Feedback Voltage (Note 1) ∆VLOADREG Output Voltage Line Regulation Reference Voltage Line Regulation Output Voltage Load Regulation Unit V nA 270 Each converter Shutdown Current VEN1/EN2=0V, VIN1/IN2=4.2V Peak Inductor Current ∆VFB 5.5 ±30 IPK ∆VOUT EUP3409 Min Typ Max. 370 µA 1 µA A 1 1.3 1.6 TA=25℃ 0.588 0.6 0.612 -40℃≤ TA≤ 85℃ 0.585 0.6 0.615 VIN=2.5V to 5.5V, ILOAD=0 0.25 0.4 %/V VIN=2.5V to 5.5V 0.25 0.4 %/V ILOAD=0 to 800mA 0.4 VFB1/FB2=0.6V 1.2 1.5 V % 1.8 fOSC Each converter Oscillator Frequency VFB1/FB2=0 0.7 RPFET RDS(ON) of P-Channel FET ISW1/SW2=100mA 0.28 0.4 Ω RNFET RDS(ON) of N-Channel FET 0.3 0.4 Ω ILSW SW Leakage Current ISW1/SW2= -100mA VEN1/EN2=0V, VSW1/SW2=0 or 5V, VIN1/IN2=5V ±1 µA VEN EN Threshold 1.5 V -40℃≤ TA ≤ 85℃ 0.3 1.0 Note 1: The EUP3409 is tested in a proprietary test mode that connects VFB1/FB2 to the output of the error amplifier. DS3409 Ver0.1 May. 2007 4 联系电话：１５９９９６４４５７９ ８３１５１７１５ MHz 芯美电子 Preliminary EUP3409 Typical Operating Characteristics DS3409 Ver0.1 May. 2007 5 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 DS3409 Ver0.1 May. 2007 Preliminary EUP3409 6 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 DS3409 Ver0.1 May. 2007 Preliminary EUP3409 7 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 Preliminary EUP3409 Operation Short Circuit Protection The EUP3409 has dual independent constant frequency current mode PWM step-down converters. The EUP3409 is optimized for low voltage, Li-Ion battery powered applications where high efficiency and small size are critical. The EUP3409 uses external resistor dividers to set two output voltages independently from 0.6V to 5.5V. The device integrates both main switches and synchronous rectifiers, which provides high efficiency and eliminates the need for an external Schottky diode. The EUP3409 can achieve 100% duty cycle. The duty cycle D of each step-down converter is defined as: The EUP3409 has short circuit protection. When any output is shorted to ground, the oscillator frequency is reduced to prevent the inductor current from increasing beyond the PFET current limit. The PFET current limit is also reduced to lower the short circuit current. The frequency and current limit will return to the normal values once the short circuit condition is removed and the feedback voltage reaches 0.6V. VOUT D = TON × f OSC × 100% = × 100% VIN Where TON is the main switch on time, fOSC is the oscillator frequency (1.5MHz), VOUT is the output voltage and VIN is the input voltage. Maximum Load Current The EUP3409 can operate down to 2.5V input voltage, however the maximum load current decreases at lower input due to large IR drop on the main switch and synchronous rectifier. The slope compensation signal reduces the peak inductor current as a function of the duty cycle to prevent sub-harmonic oscillations at duty cycles greater than 50%. Conversely the current limit increases as the duty cycle decreases. Current Mode PWM Control Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for superior load and line response and protection of the internal main switch and synchronous rectifier. Each channel switches at a constant frequency (1.5MHz) and regulates the output voltage. During each cycle the PWM comparator modulates the power transferred to the load by changing the inductor peak current based on the feedback error voltage. During normal operation, the main switch is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on until the next cycle starts or the inductor current starts to reverse. Dropout Operation Each channel of the EUP3409 allows the main switch to remain on for more than one switching cycle and increases the duty cycle while the input voltage is dropping close to the output voltage. When the duty cycle reaches 100%, the main switch is held on continuously to deliver current to the output up to the PFET current limit. The output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. DS3409 Ver0.1 May. 2007 8 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 Application Information Inductor Selection The output inductor is selected to limit the ripple current to some predetermined value, typically 20%~40% of the full load current at the maximum input voltage. Large value inductors lower ripple currents. Higher VIN or VOUT also increases the ripple current as shown in equation. A reasonable starting point for setting ripple current is ∆IL=320mA (40% of 800mA). ∆I L = VOUT VOUT 1 − (f)(L) VIN 1 The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation. Thus, a 960mA rated inductor should be enough for most applications (800mA+160mA). For better efficiency, choose a low DC-resistance inductor. CIN and COUT Selection In continuous mode, the source current of the top MOSFET is a square wave of duty cycle VOUT/VIN. The primary function of the input capacitor is to provide a low impedance loop for the edges of pulsed current drawn by the EUP3409. A low ESR input capacitor sized for the maximum RMS current must be used. The size required will vary depending on the load, output voltage and input voltage source impedance characteristics. A typical value is around 4.7µF. The input capacitor RMS current varies with the input voltage and the output voltage. The equation for the maximum RMS current in the input capacitor is: I RMS =I O × EUP3409 Preliminary V V O × 1 − O V V IN IN When choosing the input and output ceramic capacitors, choose the X5R or X7R dielectric formulations. These dielectrics have the best temperature and voltage characteristics of all the ceramics for a given value and size. Output Voltage Programming The output voltage is set by a resistive divider according to the following formula: R2 VOUT = 0.6V 1 + R1 The external resistive divider is connected to the output, allowing remote voltage sensing as shown in below figure. Thermal Dissipation Power dissipation shall be considered when both channels of the EUP3409 provide maximum 800mA output current to the loads at high ambient temperature with low input supply voltage. If the junction temperature rises above 150°C, the EUP3409 two channels will be shut down. The junction-to-ambient thermal resistance of the 10-pin DFN (3mm x 3mm) RθJA is 50°C /W. The maximum power dissipation is about 1.6W when the EUP3409 is operating in a 70°C ambient temperature environment. PD MAX = The output capacitor COUT has a strong effect on loop stability. The selection of COUT is driven by the required effective series resistance (ESR). ESR is a direct function of the volume of the capacitor; that is, physically larger capacitors have lower ESR. Once the ESR requirement for COUT has been met, the RMS current rating generally far exceeds the IRIPPLE(P-P) requirement. The output ripple ∆VOUT is determined by: 150°C − 70°C 50°C/W = 1.6W PC Board Layout The high current paths (GND1/GND2, IN1/IN2 and SW1/SW2) should be placed very close to the device with short, direct and wide traces. Input capacitors should be placed as close as possible to the respective IN and GND pins. The external feedback resistors shall be placed next to the FB pins. Keep the switching nodes SW1/SW2 short and away from the feedback network. 1 ∆VOUT ≅ ∆I L ESR + 8fCOUT DS3409 Ver0.1 May. 2007 9 联系电话：１５９９９６４４５７９ ８３１５１７１５ 芯美电子 EUP3409 Preliminary Packaging Information TDFN-10 SYMBOLS MILLIMETERS MIN. MAX. MIN. MAX. A 0.70 0.80 0.028 0.031 A1 0.00 0.05 0.000 0.002 D 2.90 3.10 0.114 0.122 E1 DS3409 Ver0.1 May. 2007 INCHES 1.70 0.067 E 2.90 3.10 0.114 0.122 L 0.30 0.50 0.012 0.020 b 0.18 0.30 0.007 0.012 e 0.50 0.020 D1 2.40 0.094 10 联系电话：１５９９９６４４５７９ ８３１５１７１５