LESHAN RADIO COMPANY, LTD. 5A, 500KHz Synchronous Boost Converter with Output Disconnect LR8425 Series INTRODUCTION: The /58425 devices provide a power supply solution for products powered by either a one-cell Li-Ion or Li-polymer, or a two to three-cell alkaline, NiCd or NiMH battery. The converter generates a stable output voltage that is adjusted by an external resistor divider. It provides high efficient power conversion and is capable of delivering output currents up to 1.5A at 5V at a supply voltage down to 2V. The implemented boost converter is based on a fixed switching frequency (500kHz typical), current-mode controller using a synchronous rectifier to obtain maximum efficiency. Boost switch and rectifier switch are connected internally to provide the lowest leakage inductance and best EMI behavior possible. The current-mode control scheme provides fast transient response and good output voltage accuracy. At light load, the converter will automatically enter into Pulse Frequency Modulation (PFM) operation to reduce the dominant switching losses. During PFM operation, the IC consumes very low quiescent current and maintains high efficiency over a wide load current range. The converter can be disabled to minimize battery drain. During shutdown, the load is completely disconnected from the battery. The device allows use of small inductors and output capacitors for USB devices. APPLICATIONS˖ ˖ z All Single Cell Li or Dual Cell Battery Operated Products as Tablet PC, Smartbook and Other Portable Equipment Products including portable HDMI and USB-OTG USB Hosts Without Native 5V Supplies USB Charging Port (5V) Power Bank, Battery Backup Units Wireless Peripherals Portable Audio Players Personal Medical Devices Industrial Metering Equipments DC/DC Micro Modules z z z z z z z z z Ver0.5 FEATURES: z z z 97% Efficiency at VOUT=5V from 3.3V Input Device Quiescent Current: 37μA (Typ) Guaranteed 2.5A Output Current at VOUT=5V from 3.3V Input 500kHz PWM Switching Frequency Synchronous and Embedded Power MOSFETs, No Schottky Diode Required Low RDS( ON) (main switch/synchronous switch) at 5.0V output: 20/40mohm Input Voltage Range: 1.8V to 5.25V Adjustable Output Voltage Range: from 2.5V to 5.5V Pulse Frequency Modulation Operation for Improved Efficiency at Low Output Power Current Mode Operation with Internal Compensation for Excellent Line and Load Transient Response Logic Controlled Shutdown(<1μA) Load Disconnect During Shutdown Automatic output discharge at shutdown: /58425A: Auto output discharge function /58425B: No output discharge function Low Battery Comparator Internal Soft-Start to Limit Inrush Current Over Current Protection Input Under Voltage Lockout Output Over Voltage Protection Over-Temperature Protection Available in 2.1mm x 2.1mm QFN10 Package z z z z z z z z z z z z z z z z z 1/7 LESHAN RADIO COMPANY, LTD. ORDER INFORMATION Device No. /58425AQD10 Output Voltage Adjustable Package QFN2.1x2.1-10 Packaging 3000 parts per reel /58425BQD10 Adjustable QFN2.1x2.1-10 3000 parts per reel PIN CONFIGURATION: Top View 10 9 8 7 1 6 2 5 3 4 (QFN2.1X2.1-10) PIN NO. NAME 1 CE TYPE(1) I DESCRIPTION Chip Enable Input. Internal integrated with 1Mohm pull down resistor. CE=High: Normal free running operation. CE=Low: Shutdown; quiescent current <1μA. Output capacitor can be completely discharged through the load or feedback resistors. 2 LBI I If CE is undefined, pin SW may ring. Low Battery Comparator Input (comparator enabled with CE). Battery Supply Input Voltage. The device gets its start-up bias from VIN . Once AVOUT exceeds 2.3V, bias comes from AVOUT. Thus, once started, operation is completely independent from VIN . Operation is only limited by the output power level and the battery’s internal series resistance. The VIN 3 VIN I pin should be connected to the positive terminal of the battery and bypassed with a low ESR ceramic bypass capacitor. Care should be taken to minimize the loop area formed by the bypass capacitor connections, the VIN pin, and the /58425 AGND pin. The minimum recommended bypass capacitance is 1μF ceramic with a X5R or X7R dielectric and the optimum placement is closest to the VIN pin and the AGND pin. PCB trace length from VIN to the input filter capacitor(s) should be as short and wide as possible. Ver0.5 27 LESHAN RADIO COMPANY, LTD. Power Ground. Ground connection for high-current power converter node. High current return for the low-side driver and power main switch N-MOSFET. Connect PGND with large copper areas directly to the input 4 PGND P and output supply returns and negative terminals of the input and output filter capacitor(s). Tie this pin to the ground island/plane through the lowest impedance connection available. Connect this pin to AGND. Boost and Rectifying Switch Input. Connect an inductor between this pin and VIN. Keep the PCB trace lengths as short and wide as is practical 5 SW I to reduce EMI and voltage overshoot. If the inductor current falls to zero, or pin CE is low, an internal anti-ringing switch is connected from this pin to VIN to minimize EMI. DC-DC Power Output (Drain of the Internal Synchronous Rectifier P-MOSFET). PCB trace length from PVOUT to the output filter capacitor(s) 6 PVOUT O should be as short and wide as possible. Care should be taken to minimize the loop area formed by the output filter capacitor(s) connections, the PVOUT pin, and the /58425 PGND pin. The minimum recommended output filter capacitance is 22μF ceramic with a X5R or X7R dielectric and the optimum placement is closest to the PVOUT pin and the PGND pin. PVOUT is completely disconnected from VIN when CE is low, due to the output disconnect feature. IC Supply Voltage and Output Voltage Sense Input. Bias is derived from AVOUT when AV OUT exceeds 2.3V. The AVOUT pin should be connected to the DC-DC power output pin, PVOUT, and bypassed with a 7 AVOUT I low ESR ceramic bypass capacitor for noise immunity consideration. Care should be taken to minimize the loop area formed by the bypass capacitor connections, the AVOUT pin, and the /58425 AGND pin. The minimum recommended bypass capacitance is 1μF ceramic with a X5R or X7R dielectric and the optimum placement is closest to the AVOUT pin and the AGND pin. PCB trace length from AVOUT to the output filter capacitor(s) should be as short and wide as possible. AVOUT is also completely disconnected from VIN when CE is low, due to the output disconnect feature. Feedback Input. Feedback Input to the gm Error Amplifier. Connect resistor divider tap to this pin. 8 FB I The output voltage can be adjusted from 2.5V to 5.5V by: VOUT =1.2V噝[1+(R1/R2)] The feedback networks should be connected directly to a dedicated analog ground plane and this ground plane must connect to the AGND pin. If no analog ground plane is available, then the ground connection of Ver0.5 3/7 LESHAN RADIO COMPANY, LTD. the feedback network must tie directly to the AGND pin. Connecting the network to the PGND can inject noise into the system and effect performance. The feedback network, resistors R1 and R2 must be connected to FB pin directly as closely as possible. And FB is a sensitive signal node, trace area at FB pin should be small. Please keep FB away from the inductor and SW switching node on the PCB layout to minimize copper trace connections that can inject noise into the system. Analog Ground. The analog ground ties to all of the noise sensitive signals. Provide a clean ground for the analog control circuitry and should 9 AGND I not be in the path of large currents. Return for output voltage set resistor divider. 10 LBO Connect this pin to PGND. Low Battery Comparator Output (open drain). O (1) I = input; O = output; P = power ABSOLUTE MAXIMUM RATINGS (1) PARAMETER CE Voltage Other Pins Voltage Power Dissipation (3) SYMBOL RATINGS UNITS VCE VOUT+0.3 V 6 V PD @T A=25ć 2.5 W θJA 50 °C/W θJC 10 °C/W Tj 150 °C T solder T stg 260 -65~150 °C °C (2) (2) QFN2.1X2.1-10 Package Thermal Resistance (4) Operating Junction Temperature Range Lead Temperature(Soldering, 10 sec) Storage Temperature Range (1) Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods my affect device reliability. (2) All voltages are with respect to network ground terminal. (3) The maximum allowable power dissipation is a function of the maximum junction temperature TJ (MAX), the junction-to ambient thermal resistance θJA , and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by PD (MAX) = [ TJ(MAX)-T A ]/ θJA . Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. (4) θJA is measured in the natural convection at TA=25ć on a four-layer Chipower Evaluation Board Ver0.5 4/7 LESHAN RADIO COMPANY, LTD. RECOMMENDED OPERATING CONDITIONS (5) MIN NOM MAX UNITS Supply voltage at VIN 1.8 5.25 V Output voltage at PVOUT, AVOUT 2.5 5.5 V CE 0 VOUT+0.3 V All other pins 0 5.5 V Operating Ambient temperature range, T A -40 85 °C Operating junction temperature range, T j -40 125 °C (5) The device is not guaranteed to function outside its operating conditions. ELECTRICAL CHARACTERISTICS (VCE=VIN =2.4V, VOUT=5V, IOUT =500mA, T A=25°C, unless otherwise specified) PARAMETER Input VIN UVLO Threshold VIN UVLO Hysteresis SYMBOL CONDITIONS VUVLO VIN Rising MIN VUVLO_HY S VIN Quiescent Current IQ VOUT UNITS 1.78 V V VCE=VIN =1.8V, VOUT=5V, no load, Measured on VIN pin 10 μA VCE=VIN =1.8V, VOUT=5V, no load, Measured on VOUT pin 27 μA 0.1 ISHDN VCE=0V, VIN =2.4V CE High-Level Threshold VCEH CE Rising CE Low-Level Threshold VCEL CE Falling Soft-start time T SS 1 1.2 μA V 0.3 1 0.75 /58425A VOUTİ1V (7) MAX 0.1 Shutdown Current Linear Charge Current Limit TYP(6) V ms A /58425B 1.3 A /58425A 0.7 A /58425B For /58425A only 1.2 100 A Ω ICHARGE 1V<VOUT <90%VIN Output Discharge Resistor RDSC Low Side Main N-FET RON RNDS(ON) VOUT=5V 20 mΩ Synchronous P-FET RON RPDS(ON) VOUT=5V 40 mΩ 500 KHz % A Switching Frequency F SW Maximum Duty Cycle Main N-FET Current Limit (7) (8) DMA X ILIM1 90 5.0 95 6.5 Feedback Reference Voltage Output Over Voltage Protection VREF VOVP 1.182 1.2 5.8 1.218 V V LBI Voltage Threshold VLBI 1.176 1.2 1.224 V LBI Input Hysteresis Thermal Shutdown (7) Thermal Shutdown Hysteresis (7) VIN Falling VLBI_HY S 20 mV TSD 150 °C THY S 20 °C (6) Typical numbers are at 25°C and represent the most likely norm. (7) Specification is guaranteed by characterization and not 100% tested in production. (8) Duty cycle affects current limit due to ramp generator. Ver0.5 5/7 LESHAN RADIO COMPANY, LTD. TYPICAL APPLICATION CIRCUIT R5 100K¡ VIN VBAT VIN:1.8V~4.35V C6 1F 22F/ 6.3V C1 C2 22F 22F R7 AVOUT L1 1.5H 0.1¡ LBO R3 300K¡ SW PVOUT R1 470K¡ /58425 LBI C8 0¡ 1F FB R4 200K¡ CE PGND AGND VOUT=5V C4 C9 22F 100F R2 148.4K¡ Figure 1 Standard Application Circuit Ver0.5 6/7 LESHAN RADIO COMPANY, LTD. PACKAGING INFORMATION z QFN2.1X2.1-10 Package Outline Dimensions Ver0.5 7/7