Portable Media Players GPS Receivers Hard Disk Drives

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1 XRP A 1.3MHZ SYNCHRONOUS STEP DOWN CONVERTER FEATURES Guaranteed 1.5A Output Current Fixed 1.3MHz frequency PWM Operations Achieve 95% efficiency Input Voltage : 2.5V to 5.5V Adjustable Output Voltages down to 0.6V Internal Current Mode Compensation Network No Schottky Diode Required Low Dropout Operation: % Duty Cycle 240μA Quiescent Current (no load) 1μA Shutdown Current Soft Start Function Over-current and Over-temperature Protection RoHS/Halogen free Thin DFN-6 Package APPLICATIONS Point of Load Set-top Boxes Wireless Networking Portable Media Players GPS Receivers Hard Disk Drives DESCRIPTION The XRP6657 is a high efficiency synchronous step down DC to DC converter optimized for portable battery-operated applications. Operating from 2.5V to 5.5V, it provides a guaranteed output current of 1.5A with an adjustable regulated output voltage down to 0.6V. The XRP6657 uses a fixed 1.3 MHz frequency pulse width modulation (PWM) scheme allowing for compact external components, low output voltage ripple and fixed frequency noise, while Pulse Skip Mode (PSM) is used to improve light load efficiency. A low dropout mode provides % duty cycle operation. The solution footprint is further reduced by a current mode internal compensation network and built-in synchronous switch removing the need for an external Schottky diode while improving the overall efficiency. The XRP6657 is available in a small RoHS/halogen free thin DFN-6 package. TYPICAL APPLICATION CIRCUIT 1/12

2 BLOCK DIAGRAM Fig.1: XRP6657 Block Diagram PIN DESCRIPTION Thin DFN-6L Exposed Pad Pin Number Name Description 1 V FB Feedback Pin. Receives the feedback voltage from an external resistive divider across the output. 2 VSS_PWR Power Ground Pin. 3 SW 4 VIN_PWR 5 VIN_CLN Switching node. Must be connected to inductor. This pin connects to the drains of the internal main and synchronous power MOSFET switches. Power Input Pin. Must be closely decoupled to ground pin with a 4.7µF or greater capacitor. Analog Input Pin. Must be closely decoupled to ground pin with a 4.7µF or greater capacitor. 6 EN Enable Pin. >1.2V: Enables the XRP6657 <0.4V:Disables the XRP6657 Do not leave this pin floating and enable the device once Vin is in the operating range. Exposed Pad VSS_CLN Analog Ground Pin. 2/12

3 Absolute Maximum Ratings ELECTRICAL CHARACTERISTICS These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for prolonged time periods may affect device reliability. All voltages are with respect to ground. Input Voltage V IN V to 6V EN V FB Voltage V to V IN SW Voltage V to (V IN + 0.3V) PMOS Switch Source Current (DC)... 2A NMOS Switch Sink Current (DC)... 2A Peak Switch Sink and Source Current A Operating Junction Temp. (Note 1) ºC Storage Temp. Range T STG ºC to 150ºC Lead Temperature (sold. 10s) T LEAD...2ºC ESD Human Body Model (HBM)... 2KV ESD Machine Model (MM) V Thermal Resistance θ JC...10ºC/W Thermal Resistance θ JA...55ºC/W Note 1: T J is a function of the ambient temperature T A and power dissipation P D (T J = T A + P D x 55 C/W). Recommended Operating Conditions Operating Temperature T OP ºC to 85 ºC Input voltage V IN V to 5.5V V IN =5.0V, T A =25ºC, unless otherwise specified Boldface characters apply over the full temperature range. Parameter Symbol Conditions Min Typ. Max Unit Feedback Current I VFB ± na Regulated Feedback Voltage Reference Voltage Line Regulation V FB T A =25 C V -40ºC T A 85 ºC ΔV FB V IN =2.5V to 5.5V 0.4 %/V Output Voltage Accuracy ΔV OUT % % Output Over-Voltage Lockout Over Temperature Protection Threshold Over Temperature Protection Hysteresis Output Voltage Line Regulation Peak Inductor Current Output Voltage Load Regulation ΔV OVL ΔV OVL = V OVL V FB mv t OTP Temperature rising 165 C t OTPHYS 10 C ΔV OUT V IN =2.5V to 5.5V 0.4 %/V I PK V IN =3V, V FB =0.5V or V OUT =%, Duty cycle <35% 2.4 A V LOADREG I OUT =10mA to 1.5A 0.2 %/V Quiescent Current (Note 2) I Q V FB =0.5V or V OUT =% µa Shutdown Current I SHTDWN V EN =0V, V IN =4.2V µa Oscillator Frequency f osc V FB =0.6V or V OUT =% MHz Minimum Duty Cycle D MIN 20 % R DS(ON) of PMOS R PFET I SW =750mA 0.18 Ω R DS(ON) of NMOS R NFET I SW =-750mA 0.16 Ω SW Leakage I LSW V EN =0V, V SW =0V or 5V, V IN =5V ±1 µa Enable Threshold 1.2 V Shutdown Threshold Output Voltage Start-up time V EN 0.4 V t STUP 200 µs EN Leakage Current I EN ±1 µa Note 1: The Switch Current Limit is related to the Duty Cycle. Please refer to figure 29 for details. Note 2: Dynamic quiescent current is higher due to the gate charge being delivered at the switching frequency. 3/12

4 ELECTRICAL CHARACTERISTICS Typical Characteristics 3.3Vout Efficiency vs Output Current V Output Voltage vs Output Current Vin=3.7V Output Voltage (V) Vin=3.7V Fig. 2: Efficiency vs Output Current 3.2 Fig. 3: Output Voltage vs Output Current 2.5Vout Efficiency vs Output Current V Output Voltage vs Output Current Output Voltage (V) Fig. 4: Efficiency vs Output Current 2.4 Fig. 5: Output Voltage vs Output Current 1.8Vout Efficiency vs Output Current V Output Voltage vs Output Current Output Voltage (V) Fig. 6: Efficiency vs Output Current 1.7 Fig. 7: Output Voltage vs Output Current 4/12

5 ELECTRICAL CHARACTERISTICS 1.5Vout Efficiency vs Output Current 1.5V Output Voltage vs Output Current Fig. 8: Efficiency vs Output Current Output Voltage (V) Fig. 9: Output Voltage vs Output Current 1.2Vout Efficiency vs Output Current 1.2V Output Voltage vs Output Current Fig. 10: Efficiency vs Output Current Output Voltage (V) Fig. 11: Output Voltage vs Output Current 1.0Vout Efficiency vs Output Current 1.0Vout Efficiency vs Output Current Vin=5.0V Vin=5.0V Fig. 12: Efficiency vs Output Current Fig. 13: Output Voltage vs Output Current 5/12

6 ELECTRICAL CHARACTERISTICS Fig. 14: Reference Voltage vs Temperature Fig. 15: Output Voltage vs Load Current Fig. 16: PMOS R DS(ON) vs Temperature Fig. 17: NMOS R DS(ON) vs Temperature Fig. 18: PMOS R DS(ON) vs Input Voltage Fig. 19: NMOS R DS(ON) vs Input Voltage 6/12

7 ELECTRICAL CHARACTERISTICS Fig. 20: Oscillator Frequency vs Temperature Fig. 21: Oscillator Frequency vs Supply Voltage Fig. 22: Dynamic Supply Current vs Temperature Fig. 23: Dynamic Supply Current vs Supply Voltage Fig. 24: Start-up from Shutdown Fig. 25: Start-up from Shutdown 7/12

8 ELECTRICAL CHARACTERISTICS Fig. 26: Load Step 0.75A to 1.5A Fig. 27: Load Step 0.25A to 1.5A Current Limit (A) Output current limit vs Duty Cycle Duty Cycle (%) Fig. 28: Load Step 0.5A to 1.0A Fig. 29: Output Current Limit (foldback) vs Duty Cycle 8/12

9 THEORY OF OPERATION Detailed Description Applications The typical application circuit is shown below. Fig. 30: Adjustable Output Voltage Version Typical Application Circuit Inductor Selection Inductor ripple current and core saturation are two factors considered to select the inductor value. Eq. 1: Δ I 1 V OUT = L VOUT f L 1 VIN Equation 1 shows the inductor ripple current as a function of the frequency, inductance, V IN and V OUT. It is recommended to set the ripple current to 40% of the maximum load current. A low ESR inductor is preferred. C IN and C OUT Selection A low ESR input capacitor can prevent large voltage transients at V IN. The RMS current rating of the input capacitor is required to be larger than I RMS calculated by: Eq. 2: I RMS I OMAX V OUT ( V V ) V IN IN OUT currents, high voltage ratings and low ESR that makes them ideal for switching regulator applications. As C OUT does not affect the internal control loop stability, its value can be optimized to balance very low output ripple and circuit size. It is recommended to use an X5R or X7R rated capacitors which have the best temperature and voltage characteristics of all the ceramics for a given value and size. Output Voltage The adjustable output voltage is determined by: Eq. 4: R 0.6V 1 + R = 1 V OUT 2 Short Circuit Behavior The XRP6657 has an over current and over temperature protection. The over current applies cycle by cycle and limits the P-driver FET current to maintain the inductor current within safe limits. The over temperature protection circuitry turns off the driver FETs when the junction temperature is too high. Normal Operations are restored when temperature drops below the safety threshold. In the following example, the XRP6657 is used to convert a 5V input to a 1.2V output. Shorting V OUT to ground triggers both the over current and over temperature protection circuits. The waveform is shown below. The ESR rating of the capacitor is an important parameter to select C OUT. The output ripple V OUT is determined by: 1 Eq. 3: ΔV OUT ΔI L ESR + 8 f COUT Higher values, lower cost ceramic capacitors are now available in smaller sizes. These capacitors have high ripple 9/12

10 THEORY OF OPERATION Thermal Considerations Allthough the XRP6657 has an on board over temperature circuitry, the total power dissipation it can support is based on the package thermal capabilities. The formula to ensure safe operation is given in note 1. To avoid exceeding the maximum junction temperature, thermal analysis is strongly suggested. PCB Layout The following PCB layout guidelines should be taken into account to ensure proper operation and performance of the XRP6657: 1- The GND, SW and V IN traces should be kept short, direct and wide. 2- V FB pin must be connected directly to the feedback resistors. The resistor divider network must be connected in parallel to the C OUT capacitor. 3- The input capacitor C IN must be kept as close as possible to the V IN pin. 4- The SW and VFB nodes should be kept as separate as possible to minimize possible effects from the high frequency and voltage swings of the SW node. 5- The ground plates of C IN and C OUT should be kept as close as possible. 6- Connect all analog grounds to a common node and connect the common node to the power ground via an independent path. Self Enable Application A self enable function is easily implemented through the following arrangement. A resistor ratio R3/R4=1/1.5 is recommended. Design Example In a single Lithium-Ion battery powered application, the V IN range is about 2.7V to 4.2V. The desired output voltage is 1.8V. The inductor value needed can be calculated using the following equation L 1 V = V OUT f ΔI 1 L V OUT Substituting V OUT =1.8V, V IN =4.2V, ΔI L =0mA and f=1.3mhz gives L = 1.32μH A 1.5µH inductor can be chosen with this application. An inductor of greater value with less equivalent series resistance would provide better efficiency. The CIN capacitor requires an RMS current rating of at least I LOAD(MAX) /2 and low ESR. In most cases, a ceramic capacitor will satisfy this requirement. IN Recommended Components Supplier Inductance I SAT DCR max Dimensions (mm) Part # Inter-Technical 1.5µH 2.5A 47mΩ 4.5x5x2 SD52-1R5M Supplier Capacitance Package Part # Murata 4.7µF 05 GRM219R61A475K Murata 22 µf 05 GRM219RJ226M 10/12

11 PACKAGE Thin DFN-6L Unit: mm 11/12

12 ORDERING INFORMATION Adjustable Output Voltage Part Number Voltage Option Operating Temperature Range Package XRP6657IHBTR-F Adjustable -40ºC to +85ºC Thin DFN-6L WW = Work Week X = Low Number Marking 6657 IHB WWX Packing Quantity 5,000/T&R Notice EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a user s specific application. While the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances. Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited. Exar Corporation Headquarters and Sales Offices Kato Road Fremont, CA USA Tel.: +1 (510) Fax: +1 (510) /12