PAM2308FB2YMBK

Dual High-Efficiency PWM Step-Down DC-DC Coverter PAM2308 Features n Efficiency up to 96% n Only 40μA(Typ. per Channel) Quiescent Current n Output Current: Up to 1A per Channel n Internal Synchronous Rectifier n 1.5MHz Switching Frequency n Soft Start n Under-Voltage Lockout n Short Circuit Protection n Thermal Shutdown n Small 10L WDFN 3x3 Packages n Pb-Free Package and RoHS Compliant General Description The PAM2308 is a dual step-down current-mode, DC-DC converter. At heavy load, the constantfrequency PWM control performs excellent stability and transient response. To ensure the longest battery life in portable applications, the PA M 2 3 0 8 p r o v i d e s a p o w e r - s a v i n g P u l s e Skipping Modulation (PSM) mode to reduce quiescent current under light load operation. The PAM2308 supports a range of input voltages from 2.5V to 5.5V, allowing the use of a single Li+/Li-polymer cell, multiple Alkaline/NiMH cell, USB, and other standard power sources. The dual output voltages are available for 3.3V, 2.8V, 2.5V, 1.8V, 1.5V, 1.2V or adjustable. All versions employ internal power switch and synchronous rectifier for to minimize external part count and realize high efficiency. During shutdown, the input is disconnected from the output and the shutdown current is less than 0.1 μ A. Other key features include under-voltage lockout to prevent deep battery discharge. Applications n n n n n Cellular Phone Portable Electronics Personal Information Appliances Wireless and DSL Modems MP3 Players Typical Application L1 V OUT1 C OUT1 10μF C Fw1 100nF R11 1 EN1 FB1 PAM2308 LX1 VIN1 GND 10 8 9 C IN1 4 . μF 7 V IN1 R12 2 R22 4 CIN2 4. 7μF V IN2 GND VIN2 LX2 L2 3 5 FB2 7 6 EN2 R21 C FW2 100pF V OUT2 C OUT2 10μF VOUTx = VREF 1 + Rx1 Rx2 Figure 1. Adjustable Voltage Regulator ( ) Power Analog Microelectronics , Inc www.poweranalog.com 1 07/2008 Rev 1.0 Dual High-Efficiency PWM Step-Down DC-DC Coverter PAM2308 Typical Application V OUT1 C OUT1 10μF 1 L1 PAM2308 EN1 2 LX1 VIN1 GND FB2 EN2 10 8 9 7 6 C IN2 4. 7μF V IN2 FB1 GND VIN2 C IN1 4. 7μF V IN1 4 3 5 LX2 L2 V OUT2 C OUT2 10 μ F VOUTx = 1. , 1. , 1.8V, 2. 2.8V or 3. 2V 5V 5V, 3V Figure 2. Fixed Voltage Regulator Block Diagram VINx OSC FBx FREQ SHIFT + -++ 1 . 5M OSC SLOPE COMP PWM COMP IAMP + - SQ EA R1 R2 COMP VIN SWITCHING RQ LOGIC AND RS LATCH BLANKING CIRCUIT MAIN SWITCH ( PCH ) ANTI SHOOT THRU LXx SYNCHRONOUS RECTIFIER ( NCH ) ENx 0 . 6VREF SHUTDOWN IRCMP + - GND Power Analog Microelectronics , Inc www.poweranalog.com 2 07/2008 Rev 1.0 Dual High-Efficiency PWM Step-Down DC-DC Coverter PAM2308 Pin Configuration and Marking Information TOP VIEW WDFN-10L 3x3 EN1 FB1 VIN2 GND LX2 1 2 3 4 5 10 9 LX1 GND VIN1 FB2 EN2 2308v 1v 2 XXXYW 8 7 6 v 1: Output Voltage 1 v 2: Output Voltage 2 (refer to “Ordering Information”) X: Internal Code Y: Year W: Week GND (Exposed Pad) Pin No. 1 2 3 4 ,9 5 6 7 8 10 Pin Name EN1 FB1 VIN2 GND LX2 EN2 FB2 VIN1 LX1 Pin Function Chip Enable of Channel 1 (Active High). VEN1≤VIN1. Feedback of Channel 1. Power Input of Channel 2. Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. Pin for Switching of Channel 2. Chip Enable of Channel 2 (Active High). VEN2≤VIN2. Feedback of Channel 2. Power I t of Channel 1. npu Pin for Switching of Channel 1. Power Analog Microelectronics , Inc www.poweranalog.com 3 07/2008 Rev 1.0 Dual High-Efficiency PWM Step-Down DC-DC Coverter PAM2308 Absolute Maximum Ratings 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................................. - 0.3V to 6.5V E N 1,F B 1,L X 1,E N 2,F B 2 and LX2 Pin Voltage........ - 0 . 3V to ( V IN + 0 . 3V ) Junction Temperature................................150°C Storage Temperature Range....... - 65°C to 150°C Soldering Temperature.....................260°C , 10sec Recommended Operating Conditions Supply Voltage...............................2.5V to 5.5V Ambient Temperature Range......... - 40 °C to 85 °C Junction Temperature Range.........-40°C to 125 °C Thermal Information Parameter Thermal Resistance (Junction to ambient) Thermal Resistance (Junction to case) Power Dissipation Symbol θJA θJC PD Package WDFN 3x3-10 WDFN 3x3-10 WDFN 3x3-10 Maximum 60 8.5 1.66 Unit °C/W °C/W W Power Analog Microelectronics , Inc www.poweranalog.com 4 07/2008 Rev 1.0 Dual High-Efficiency PWM Step-Down DC-DC Coverter PAM2308 Electrical Characteristic T A=25 OC, V IN=3.6V, V O=1.8V, C IN=10μF, C O=10μF, L=2.2μH, unless otherwise noted. PARAMETER Input Voltage Range Regulated Feedback Voltage Reference Voltage Line Regulation Regulated Output Voltage Accuary Peak Inductor Current Output Voltage Line Regulation Output Voltage Load Regulation Quiescent Current (per channel) Shutdown Current (per channel) Oscillator Frequency Drain-Source On-State Resistance SW Leakage Current (per channel) High Efficiency EN Threshold High EN Threshold Low EN Leakage Current Over Temperature Protection OTP Hysteresis SYMBOL VIN V FB ΔV FB VO IPK LNR LDR IQ ISD fOSC RDS(ON) ILSW η VEH VEL IEN OTP OTH ±0.01 150 30 1.5 0.3 IO = 100mA VIN=3V,VFB = 0.5V or VO=90% VIN = 2.5V to 5V, IO=10mA IO=1mA to 1A No load VEN = 0V VO = 100% VFB = 0V or VO = 0V IDS=100mA P MOSFET N MOSFET 1.2 -3 1.5 0.2 0.5 40 0.1 1.5 500 0.3 0.35 ±0.01 96 0.45 0.5 1 0.5 1.5 70 1 1.8 Test Conditions MIN 2.5 0.588 0.6 0.3 +3 TYP MAX 5.5 0.612 UNITS V V %/V % A %/V % μA μA MHz kHz Ω Ω μA % V V μA °C °C Power Analog Microelectronics , Inc www.poweranalog.com 5 07/2008 Rev 1.0 Dual High-Efficiency PWM Step-Down DC-DC Coverter PAM2308 Typical Performance Characteristics T A=25 °C , C IN=10 μ F, C O=10 μ F, L=4.7 μ H, unless otherwise noted. Efficiency vs Output Current (Vo=1.2V) Efficiency vs Output Current (Vo=1.5V) 100 90 80 70 60 50 40 30 20 10 0 100 90 Efficiency(%) Efficiency(%) 80 70 60 50 40 30 20 2.5V 3.6V 4.2V Vin=3.6V Vin=4.2V Vin=5V 1 10 100 1000 1 10 100 1000 Output Current(mA) Output Current(mA) Efficiency vs Output Current ( Vo=1.8V ) 100 90 100 90 80 Efficiency vs Output Current ( Vo=2.5V ) Efficiency(%) 80 70 60 50 40 30 20 1 10 100 Output Current(mA) 1000 2.5V 3.6V 4.2V Efficiency(%) 70 60 50 40 30 20 1 10 100 1000 Output Current(mA) 3V 3.6V 4.2V 100 90 Efficiency vs Output Current (Vo=2.8V) 70 60 50 40 30 20 1 10 100 Output Current(mA) 3V 3.6V 4.2V Efficiency(%) Efficiency(%) 80 100 90 80 70 60 50 40 30 20 10 0 Eifficiency VS Output Current (Vo=3.3V) Vin=3.6V Vin=4.2V Vin=5V 1000 1 10 100 1000 Output Current(mA) Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 6 Dual High-Efficiency PWM Step-Down DC-DC Coverter PAM2308 Typical Performance Characteristics T A=25 °C , C IN=10 μ F, C O=10 μ F, L=4.7 μ H, unless otherwise noted. Efficiency VS Input Voltage ( Vo=1.2V ) 100 90 Efficiency(%) Efficiency(%) 100 90 80 70 60 50 Io=10mA E fficiency vs Input Voltage ( Vo=1.5V ) 80 70 60 50 40 30 3 3.5 4 4.5 5 5.5 Input Voltage(V) Io=100mA Io=800mA 10mA 40 30 2.5 3 100mA 800mA 3.5 4 4.5 5 5.5 Input Voltage(V) Efficiency vs Input Voltage ( Vo=1.8V ) 100 90 100 90 Efficiency vs Input Voltage ( Vo=2.5V ) Efficiency(%) Efficiency(%) 80 70 60 50 10mA 80 70 60 50 10mA 40 30 2.5 3 100mA 800mA 40 30 100mA 800mA 3.5 4 4.5 5 5.5 3 3.5 4 4.5 5 5.5 Input Voltage(V) Input Voltage(V) 100 90 Efficiency vs Input Voltage ( Vo=2.8V ) Eifficiency VS Input Voltage (Vo=3.3V) 100 90 80 70 60 50 40 30 20 10 0 Io=10mA Io=100mA Io=800mA Efficiency(%) 70 60 50 10mA 40 30 3 100mA 800mA Eifficiency(%) 80 3.5 4 4.5 5 5.5 3.5 3.75 4 4.25 4.5 4.75 5 5.25 5.5 Input Voltage(V) Input Voltage(V) Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 7 Dual High-Efficiency PWM Step-Down DC-DC Coverter PAM2308 Typical Performance Characteristics T A=25 °C , C IN=10 μ F, C O=10 μ F,L=4.7 μ H, unless otherwise noted. Reference Voltage VS Input Voltage 0.602 0.600 0.598 0.596 Vfb(V) Output Voltage VS Input Voltage 1.218 1.213 Output Voltage(V) Vin=3.6V 1.208 1.203 1.198 Io=1mA 0.594 0.592 0.590 0.588 0.586 0.584 2 3 4 Input Voltage(V) 5 6 I=100mA I=600mA I=800mA 1.193 1.188 2.5 3 Io=500mA Io=1A 3.5 4 4.5 5 5.5 Input Voltage(V) Reference Voltage VS Temperature 0.620 1.194 1.193 Output Voltage VS Temperature Reference Voltage(V) 0.615 0.610 0.605 0.600 0.595 0.590 0 50 100 150 Tem perature(°C) Output Voltage(V) 1.192 1.191 1.19 1.189 1.188 20 40 60 80 100 120 140 Temperature(°C) Vo=1.2V Vin=3.6V Io=100mA Reference Voltage VS Load Current 0.603 0.600 1.213 1.218 Output Voltage VS Load Current Vo=1.2V Reference Voltage(V) 0.598 0.595 0.593 0.590 0.588 0.585 0.583 0.580 0 200 400 600 800 1000 Load Current(mA) Vin=2.7V Vin=3.6V Vin=4.2V Output Voltage(V) 1.208 1.203 1.198 1.193 1.188 0 100 200 300 400 500 600 700 800 900 1000 Load Current(mA) Vin=2.7V Vin=3.6V Vin=4.2V Vin=5V Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 8 Dual High-Efficiency PWM Step-Down DC-DC Coverter PAM2308 Typical Performance Characteristics T A=25 C, C IN=10 μ F, C O=10 μ F,L=4.7 μ H, unless otherwise noted. Dynamic Supply Current VS Input Voltage 50 O Dynamic Supply Current VS Temperature 60 Dynamic Supply Current(uA) Dynamic Supply Current(uA) 45 40 35 30 25 20 15 10 5 0 Vo=1.2V ILoad =0A 50 40 30 Vo=1.2V 20 10 0 Vin=3.6V ILoad=0A 2.5 3 3.5 4 4.5 Input Voltage(V) 5 5.5 40 60 80 100 120 140 Temperature(°C) R dson VS Input Voltage 0.4 Rdson VS Temperature 0.6 Vin=3.6V 0.35 RDS(ON) Vin=3.6V 0.5 0.4 0.3 0.25 0.2 0.15 0.1 2 3 4 Input Voltage(V) 5 6 Rds(on) 0.3 0.2 0.1 0 20 70 Temperature(°C) 120 Vin=4.2V Vin=3.6V Vin=2.7V Oscillator Frequency VS Supply Voltage 1.8 1.58 Oscillator Frequency VS Temperature Vin=3.6V Oscillator Frequency(MHz) 1.56 Vin=3.6V Oscillator Frequency(MHz) 1.7 1.6 1.5 1.4 1.3 1.2 2 3 4 Supply Voltage(V) 5 1.54 1.52 1.50 20 40 60 80 100 120 140 Temperature(°C) Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 9 Dual High-Efficiency PWM Step-Down DC-DC Coverter PAM2308 Typical Performance Characteristics T A=25 °C ,C IN=10 μ F, C O=10 μ F,L=4.7 μ H, unless otherwise noted. L oad Transient Io=0-500mA Vo=3.3V Vin=5V Load Transient Io=0-1A Vo=1.2V Vin=3.6V Output Current Output Current Voltage Output Voltage Output Start-up from Shutdown Vo=1.8V,Vin=3.6V Voltage Output Enable Inductor Current Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 10 Dual High-Efficiency PWM Step-Down DC-DC Coverter PAM2308 A pplication Information The basic PAM2308 application circuit is shown in Page 1. External component selection is determined by the load requirement, selecting L first and then Cin and Cout. Inductor Selection For most applications, the value of the inductor will fall in the range of 1μH to 4.7μH. Its value is chosen based on the desired ripple current. Large value inductors lower ripple current and small value inductors result in higher ripple currents. Higher V IN or Vout also increases the ripple current as shown in equation 1. A reasonable starting point for setting ripple current is △I L = 400mA (40% of 1A). DIL = 1 æ VOUT ö VOUT ç 1÷ f )(L ) VIN ø ( è The selection of Cout is driven by the required effective series resistance (ESR). Typically, once the ESR requirement for Cout has been met, the RMS current rating generally far exceeds the I RIPPLE(P-P) requirement. The output ripple △Vout is determined by: 1ö æ VVOUT @VIL ç ESR+ ÷ 8fCOUT ø è Where f = operating frequency, C OUT =output capacitance and Δ I L = ripple current in the inductor. For a fixed output voltage, the output ripple is highest at maximum input voltage since Δ I L increases with input voltage. Using Ceramic Input and Output Capacitors Higher values, lower cost ceramic capacitors are now becoming available in smaller case sizes. Their high ripple current, high voltage rating and low ESR make them ideal for switching regulator applications. Using ceramic capacitors can achieve very low output ripple and small circuit size. When choosing the input and output ceramic capacitors, choose the X5R or X7R dielectric formulations. These dielectrics have the best temperature and voltage charac teristics of all the ceramics for a given value and size. Thermal consideration Thermal protection limits power dissipation in the PAM2308. When the junction temperature exceeds 150°C, the OTP (Over Temperature Protection) starts the thermal shutdown and turns the pass transistor off. The pass transistor resumes operation after the junction temperature drops below 120°C. For continuous operation, the junction temperature should be maintained below 125°C. The power dissipation is defined as: PD =IO 2 VORDSONH + (VIN -VO )RDSONL VIN + (t SW FSIO +IQ )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 1.4A rated inductor should be enough for most applications (1A + 400mA). For better efficiency, choose a low DC-resis tance inductor. Vo L 1.2V 2.2μH 1.5V 2.2μH 1.8V 2.2μH 2.5V 4.7μH 3.3V 4.7μH C IN and C OUT Selection In continuous mode, the source current of the top MOSFET is a square wave of duty cycle Vout/Vin. To prevent large voltage transients, a low ESR input capacitor sized for the maximum RMS current must be used. The maximum RMS capacitor current is given by: é VOUT (VIN - VOUT )ù û CIN required IRMS @ IOMAX ë VIN 1 2 This formula has a maximum at V IN =2Vout, w h e r e I RMS= I OUT/ 2 . T h i s s i m p l e w o r s t - c a s e condition is com monly used for design because even significant deviations do not offer much relief. Note that the capacitor manufacturer's ripple current ratings are often based on 2000 hours of life. This makes it advisable to further derate the capacitor, or choose a capacitor rated at a higher temperature than required. Consult the manufac turer if there is any question. I Q is the step-down converter quiescent current. The term tsw is used to estimate the full load step-down converter switching losses. Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 11 Dual High-Efficiency PWM Step-Down DC-DC Coverter 100% Duty Cycle Operation As the input voltage approaches the output voltage, the converter turns the P-chan nel transistor continuously on. In this mode the output voltage is equal to the input voltage minus the voltage drop across the P - channel transistor: V OUT = V IN – I LOAD (R dson + R L) where R dson = P-channel switch ON resistance, I L O A D = Output current, R L = Inductor DC resistance UVLO and Soft-Start The reference and the circuit remain reset until the VIN crosses its UVLO threshold. The PAM2308 has an internal soft-start circuit that limits the in-rush current during start-up. This prevents possible voltage drops of the input voltage and eliminates the output voltage overshoot. The soft-start acts as a digital circuit to increase the switch current in several steps to the P-channel current limit (1500mA). Short Circuit Protection The switch peak current is limited cycle-by-cycle to a typical value of 1500mA. In the event of an output voltage short circuit, the device operates with a frequency of 400kHz and minimum duty cycle, therefore the average input current is typically 200mA. Thermal Shutdown When the die temperature exceeds 150°C, a reset occurs and the reset remains until the temperature decrease to 120°C, at which time the circuit can be restarted. PAM2308 F or the condition where the step-down converter is in dropout at 100% duty cycle, the total device dis sipation reduces to: PD =IO 2RDSONH +IQ VIN Since R DS(ON), quiescent current, and switching losses all vary with input voltage, the total losses should be investigated over the complete input voltage range. The maximum power dissipation depends on the thermal resistance of IC package, PCB layout, the rate of surrounding airflow and temperature difference between junction and ambient. The maximum power dissipation can be calculated by the following formula: PD = TJ(MAX) -TA θJA Where TJ(max) is the maximum allowable junction temperature 125°C.T A is the ambient temperature and θ JA is the thermal resistance from the junction to the ambient. Based on the standard JEDEC for a two layers thermal test board, the thermal resistance θ JA of WDFN3X3 is 60°C/W. The maximum power dissipation at T A = 25°C can be calculated by following formula: P D=(125°C-25°C)/60°C/W=1.66W Setting the Output Voltage The internal reference is 0.6V (Typical). The output voltage is calculated as below: æ R1 ö VO=0.6×1+ ç R2 ÷ è ø The output voltage is given by Table 1. Table 1: Resistor selection for output voltage setting Vo 1.2V 1.5V 1.8V 2.5V 3.3V R1 100k 150k 200k 380k 540k R2 100k 100k 100k 120k 120k Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 12 Dual High-Efficiency PWM Step-Down DC-DC Coverter P CB Layout Check List When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the PAM2308. These items are also illustrated graphically in Figure 1. Check the following in your layout: 1. The power traces, consisting of the GND trace, the SW trace and the VIN trace should be kept short, direct and wide. 2. Does the FB pin connect directly to the feedback resistors? The resistive divider R1/R2 must be connected between the (+) plate of C OUT and ground. 3. Does the (+) plate of CIN connect to VIN as closely as possible? This capacitor provides the AC current to the internal power MOSFETs. 4. Keep the switching node, SW, away from the sensitive FB node. 5. Keep the (–) plates of C IN and C OUT as close as possible. Top Bottom PAM2308 Figure 1 :PAM2308 Suggested Layout Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 13 Dual High-Efficiency PWM Step-Down DC-DC Coverter PAM2308 Ordering Information PAM 2308 X X X v 1 v 2 Output Voltage 2 Output Voltage 1 Number of Pins Package Type Pin Configuration Output Voltage v1 K: 3.3V H: 2.8V G: 2.5V E: 1.8V C: 1.5V B: 1.2V A: Adj v2 K: 3.3V H: 2.8V G: 2.5V E: 1.8V C: 1.5V B: 1.2V A: Adj Pin Configuration B Type 1. EN1 2. FB1 3. VIN2 4. GND 5. LX2 6 :EN2 7. FB2 8. VIN1 9. GND 10. LX1 Package Type Y: WDFN 3x3 Number of Pins M: 10 Part Number PAM2308BYMv1v2 Marking 2308v1v2 XXXYW Package Type WDFN3x3-10 Standard Package 3,000 Units/Tape&Reel Power Analog Microelectronics , Inc www.poweranalog.com 14 07/2008 Rev 1.0 Dual High-Efficiency PWM Step-Down DC-DC Coverter PAM2308 Outline Dimensions 3x3 mm WDFN 10 Power Analog Microelectronics , Inc www.poweranalog.com 15 07/2008 Rev 1.0