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EUP3409
Dual 1.5MHz, 800mA Synchronous Step-Down Converter
DESCRIPTION
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.
FEATURES
Up to 96% 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 <1A Shutdown Current Soft Start Function Space Saving 10-Pin TDFN Package RoHS Compliant and 100% Lead(Pb)-Free
APPLICATIONS
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. Adjustable Voltage Regulator
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Block Diagram
Figure 2.
Pin Configurations
Package Type Pin Configurations
TDFN-10
Pin Description
PIN EN1 FB1 IN2 GND2 SW2 EN2 FB2 IN1 GND1 SW1 Pin 1 2 3 4 5 6 7 8 9 10 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 < 0.1A).Do not leave EN1 floating. Channel 1 Feedback. 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 < 0.1A). Do not leave EN2 floating. Channel 2 Feedback. 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.
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Ordering Information
Order Number EUP3409JIR1 Package Type TDFN-10 Marking xxxxx P3409 20 Operating Temperature range -40 C to 85C
EUP3409 1/4
1/4
1/4
1/4
Lead Free Code 1: Lead Free 0: Lead
Packing R: Tape & Reel Operating temperature range I: Industry Standard Package Type J: TDFN
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Absolute Maximum Ratings
VINX to GND ------------------------------------------------------------------------- -0.3V to 6V VSWX to GND --------------------------------------------------------------- -0.3V to VINX+0.3V VFBX ,VENX to GND --------------------------------------------------------------- -0.3V to VINX Junction Temperature --------------------------------------------------------------------- 125C Storage Temperature ----------------------------------------------------------- -65C to 150C Lead Temp (Soldering, 10sec) ------------------------------------------------------260C
Recommended Operating Conditions
Supply Voltage, VINX ----------------------------------------------------------2.5V to 5.5V Output Voltage, VOUTX ---------------------------------------------------------0.6V to 5V Operating Temperature --------------------------------------------------------- -40C to 85C
Electrical Characteristics
VINX =VENX =3.6V, TA=25C, Unless otherwise specified.
Symbol
VIN IFB IQ ISHDN IPK VFB VOUT VFB VLOADREG fOSC RPFET RNFET ILSW VEN
Parameter
Input Voltage Range Feedback Current Each converter Supply Current Peak Inductor Current Regulator Feedback Voltage (Note 1) Output Voltage Line Regulation Reference Voltage Line Regulation Output Voltage Load Regulation Each converter Oscillator Frequency RDS(ON) of P-Channel FET RDS(ON) of N-Channel FET SW Leakage Current EN Threshold
Conditions
EUP3409 Min Typ Max.
2.5 30 5.5 270 1.05 0.588 0.585 1.25 0.6 0.6 0.25 0.25 0.5 1.2 1.5 0.7 0.28 0.3 0.3 1.0 0.4 0.4 1 1.5 1.8 0.612 0.615 0.4 0.4 370 1
Unit
V nA A A A V %/V %/V % MHz A V
VFBX=0.5V, SWX Open VINX=3V,VFBX=0.5V TA=25J -40ae TA 85J VINX=2.5V to 5.5V, ILOAD=0 VINX=2.5V to 5.5V ILOAD=0 to 800mA VFBX=0.6V VFBX=0 ISWX=200mA ISWX= -200mA VENX=0V, VSWX=0 or 5V, VINX=5V -40ae TA 85J
Each converter Shutdown Current VENX=0V, VINX=4.2V
Note 1: The EUP3409 is tested in a proprietary test mode that connects FBX to the output of the error amplifier.
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Typical Operating Characteristics
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Operation
The EUP3409 has dual independent slop-compensated constant frequency current mode PWM step-down converters. Both the main (P-channel MOSFET) and synchronous (N-channel MOSFET) switches are internal. During normal operation, the EUP3409 regulates output voltage by switching at a constant frequency and then modulating the power transferred to the load each cycle using PWM comparator. The duty cycle is controlled by three weighted differential signals: the output of error amplifier, the main switch sense voltage and the slope-compensation ramp. It modulates output power by adjusting the inductor-peak current during the first half of each cycle. An N-channel, synchronous switch turns on during the second half of each cycle (off time). When the inductor current starts to reverse or when the PWM reaches the end of the oscillator period, the synchronous switch turns off. This keeps excess current from the output capacitor to GND, or through the main and synchronous switch to GND.
I RMS =I O x
V V O x 1 - O V V IN IN

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:
1 VOUT I L ESR + 8fC OUT

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).
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:
I L =
VOUT VOUT 1 - (f)(L) VIN
1

R2 VOUT = 0.6V 1 + R1
The external resistive divider is connected to the output, allowing remote voltage sensing as shown in below figure.
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 4.7F. 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:
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Thermal Considerations To avoid the EUP3409 from exceeding the maximum junction temperature, the user will need to do a thermal analysis. The goal of the thermal analysis is to determine whether the operating conditions exceed the maximum junction temperature of the part. The temperature rise is given by: TR=(PD)(JA) Where PD=ILOAD2 N RDS(ON) is the power dissipated by the regulator ; JA is the thermal resistance from the junction of the die to the ambient temperature. The junction temperature, TJ, is given by: TJ=TA+TR Where TA is the ambient temperature. TJ should be below the maximum junction temperature of 125C. PC Board Layout Checklist When laying out the printed circuit board, the following guidelines should be used to ensure proper operation of the EUP3409. 1. The input capacitor CINX should connect to VINX as closely as possible. This capacitor provides the AC current to the internal power MOSFETs. 2. The power traces, consisting of the GND trace, the SW trace and the VINX trace should be kept short, direct and wide. 3. The FBx pin should connect directly to the feedback resistors. The resistive divider R11/R12 and R21/R22 must be connected between the COUTX and ground. 4. Keep the switching node, SWX, away from the sensitive FBx node.
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Packaging Information
TDFN-10
SYMBOLS A A1 D E1 E L b e D1
MILLIMETERS MIN. 0.70 0.00 2.90 1.70 2.90 0.30 0.18 0.50 2.40 3.10 0.50 0.30 0.114 0.012 0.007 MAX. 0.80 0.05 3.10 MIN. 0.028 0.000 0.114
INCHES MAX. 0.031 0.002 0.122 0.067 0.122 0.020 0.012 0.020 0.094
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