PAM2306 Dual High-Efficiency PWM Step-Down DC-DC Coverter Features General Description 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 12L WDFN3x3 Package n Pb-Free Package and RoHS Compliant The PAM2306 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 6 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 PAM2306 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 C OUT2 10μF L2 V OUT2 PAM2306 V IN2 CIN2 4 7μF 1 VIN2 EN2 12 2 LX2 NC2 11 GND FB2 10 3 R12 CFw1 100 pF 4 R11 R21 C FW2 100 pF 9 FB1 GND 5 NC1 LX1 6 EN1 VIN1 7 R22 8 C IN1 4.7 μF V IN1 L1 V OUT1 C OUT1 10μF ( VOUTx = VREF 1 + Rx1 Rx2 ) Figure 1. Adjustable Voltage Regulator Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 1 PAM2306 Dual High-Efficiency PWM Step-Down DC-DC Coverter Typical Application L2 V OUT2 V IN2 PAM2306 C IN2 4.7μF 1 VIN2 EN2 12 2 NC2 11 LX2 FB2 10 3 GND 4 C OUT2 10 μ F FB1 GND 5 NC1 LX1 6 EN1 VIN1 9 8 7 C IN1 4.7μF V IN1 L1 V OUT1 C OUT1 10μF VOUTx = 1.2V,1.5V,1.8V,2.5V, 2.8V or 3.3V Figure 2. Fixed Voltage Regulator Block Diagram SLOPE COMP OSC FBx R1 IAMP - PWM COMP MAIN SWITCH ( PCH ) S Q FREQ SHIFT + R2 EA COMP SWITCHING R Q LOGIC AND RS LATCH BLANKING CIRCUIT ANTI SHOOT THRU 0 . 6VREF + IRCMP SHUTDOWN LXx SYNCHRONOUS RECTIFIER ( NCH ) VIN ENx VINx - + + 1 . 5M OSC + GND - Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 2 PAM2306 Dual High-Efficiency PWM Step-Down DC-DC Coverter Pin Configuration and Marking Information TOP VIEW WDFN-12L 3x3 VIN2 1 12 EN2 LX2 2 11 NC2 GND 3 10 FB2 9 GND FB1 4 NC1 5 2306v 1v 2 XXXYW EN1 6 8 LX1 7 VIN1 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. Pin Name Pin Function 1 VIN2 Power Input of Channel 2. 2 LX2 Pin for Switching of Channel 2. GND Ground.The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. FB1 Feedback of Channel 1. NC1,NC2 No Connection 6 EN1 Chip Enable of Channel 1 (Active High).VEN1≤VIN1. 7 VIN1 Power Input of Channel 1. 8 LX1 Pin for Switching of Channel 1. 10 FB2 Feedback of Channel 2. 12 EN2 Chip Enable of Channel 2 (Active High). VEN2≤VIN2. 3,9, Exposed Pad 4 5,11 Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 3 PAM2306 Dual High-Efficiency PWM Step-Down DC-DC Coverter 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 En1, Fb1, Lx1, En2, Fb2 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 Ambient Temperature Range......... - 40 °C to 85 °C Junction Temperature Range.........-40°C to 125 °C Supply Voltage...............................2.5V to 5.5V Thermal Information Parameter Symbol Package Maximum Unit Thermal Resistance (Junction to ambient) θJA WDFN 3x3-12 60 °C/W Thermal Resistance (Junction to case) θJC WDFN 3x3-12 8.5 °C/W Power Dissipation PD WDFN 3x3-12 1.66 W Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 4 PAM2306 Dual High-Efficiency PWM Step-Down DC-DC Coverter 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 SYMBOL Test Conditions MIN Input Voltage Range V IN 2.5 Regulated Feedback Voltage VFB 0.588 TYP 0.6 Reference Voltage Line Regulation ΔVFB Regulated Output Voltage Accuary VO IO = 100mA Peak Inductor Current IPK V IN =3V,V FB = 0.5V or VO=90% 1.5 MAX UNITS 5.5 V 0.612 V 0.3 -3 %/V +3 % A Output Voltage Line Regulation LNR V IN = 2.5V to 5V, IO =10mA 0.2 0.5 %/V Output Voltage Load Regulation LDR IO=1mA to 1A 0.5 1.5 % Quiescent Current (per channel) IQ No load 40 70 μA Shutdown Current (per channel) ISD V EN = 0V 0.1 1 μA Oscillator Frequency fOS C 1.5 1.8 MHz 1.2 V FB = 0V or VO = 0V 500 kHz P MOSFET 0.3 0.45 Ω N MOSFET 0.35 0.5 Ω ILSW ±0.01 1 μA η 96 Drain-Source On-State Resistance RDS(ON) SW Leakage Current (per channel) High Efficiency V O = 100% IDS=100mA % EN Threshold High V EH 1.5 V EN Threshold Low VE L EN Leakage Current IEN ±0.01 μA Over Temperature Protection OTP 150 °C OTP Hysteresis OTH 30 °C 0.3 V Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 5 PAM2306 Dual High-Efficiency PWM Step-Down DC-DC Coverter Typical Performance Characteristics Efficiency vs Output Current (Vo=1.2V) 100 90 80 70 60 50 40 30 20 10 0 Efficiency vs Output Current (Vo=1.5V) 100 90 Efficiency(%) Efficiency(%) T A=25 °C , C IN=10 μ F, C O=10 μ F, L=4.7 μ H, unless otherwise noted. 70 60 50 40 Vin=3.6V 2.5V 3.6V 30 Vin=4.2V 4.2V Vin=5V 1 80 20 10 100 1 1000 100 90 90 80 80 Efficiency(%) Efficiency(%) Efficiency vs Output Current ( Vo=1.8V ) 100 70 60 50 3.6V 70 60 50 3V 3.6V 30 4.2V 4.2V 20 20 1 10 100 Output Current(mA) 1 1000 90 Efficiency(%) 80 70 60 50 40 3V 30 3.6V 4.2V 20 1 10 10 100 1000 Output Current(mA) Efficiency vs Output Current (Vo=2.8V) 100 Efficiency(%) 1000 Efficiency vs Output Current ( Vo=2.5V ) 40 2.5V 30 100 Output Current(mA) Output Current(mA) 40 10 100 1000 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 1 Output Current(mA) 10 100 1000 Output Current(mA) Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 6 PAM2306 Dual High-Efficiency PWM Step-Down DC-DC Coverter 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. 100 90 90 80 80 Efficiency(%) Efficiency(%) Efficiency VS Input Voltage ( Vo=1.2V ) 100 70 60 50 Efficiency vs Input Voltage ( Vo=1.5V ) 70 60 50 10mA Io=10mA 40 40 Io=100mA 100mA 800mA Io=800mA 30 30 3 3.5 4 4.5 5 2.5 5.5 3 3.5 Efficiency vs Input Voltage ( Vo=1.8V ) 100 100 90 90 80 80 Efficiency(%) Efficiency(%) 4.5 5 5.5 Input Voltage(V) Input Voltage(V) 70 60 Efficiency vs Input Voltage ( Vo=2.5V ) 70 60 50 50 10mA 10mA 40 40 100mA 30 30 2.5 3 100mA 800mA 800mA 3.5 4 4.5 5 3 5.5 3.5 4 5 5.5 Eifficiency VS Input Voltage (Vo=3.3V) Efficiency vs Input Voltage ( Vo=2.8V ) 100 4.5 Input Voltage(V) Input Voltage(V) 100 90 90 80 Eifficiency(%) Efficiency(%) 4 70 60 50 10mA 40 100mA 80 70 60 50 40 30 20 Io=10mA Io=100mA 10 800mA Io=800mA 30 0 3 3.5 4 4.5 5 3.5 5.5 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 PAM2306 Dual High-Efficiency PWM Step-Down DC-DC Coverter 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. Output Voltage VS Input Voltage Reference Voltage VS Input Voltage 0.602 1.218 Vin=3.6V 0.600 1.213 Output Voltage(V) 0.598 Vfb(V) 0.596 0.594 0.592 0.590 0.588 I=100mA 1.203 1.198 Io=1mA 1.193 I=600mA 0.586 1.208 Io=500mA Io=1A I=800mA 1.188 0.584 2 3 4 Input Voltage(V) 5 6 2.5 3.5 4 5 5.5 Output Voltage VS Temperature 1.194 0.615 1.193 Output Voltage(V) 0.620 0.610 0.605 0.600 0.595 1.192 1.191 Vo=1.2V 1.19 Vin=3.6V 1.189 0.590 Io=100mA 1.188 0 50 100 20 150 40 60 80 100 120 140 Temperature(°C) Tem perature(°C) Output Voltage VS Load Current Reference Voltage VS Load Current 0.603 1.218 Vo=1.2V 0.600 1.213 0.598 Output Voltage(V) Reference Voltage(V) 4.5 Input Voltage(V) Reference Voltage VS Temperature Reference Voltage(V) 3 0.595 0.593 0.590 0.588 0.585 1.208 1.203 1.198 Vin=2.7V Vin=3.6V Vin=2.7V 1.193 Vin=3.6V 0.583 Vin=4.2V Vin=5V Vin=4.2V 0.580 1.188 0 200 400 600 800 0 1000 100 200 300 400 500 600 700 800 900 1000 Load Current(mA) Load Current(mA) Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 8 PAM2306 Dual High-Efficiency PWM Step-Down DC-DC Coverter Typical Performance Characteristics O 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 Dynamic Supply Current VS Temperature 60 Vo=1.2V 45 Dynamic Supply Current(uA) Dynamic Supply Current(uA) 50 ILoad=0A 40 35 30 25 20 15 10 50 40 30 Vo=1.2V 20 Vin=3.6V 10 ILoad=0A 5 0 0 2.5 3 3.5 4 4.5 Input Voltage(V) 5 40 5.5 60 100 120 140 Rdson VS Temperature R dson VS Input Voltage 0.6 0.4 Vin=3.6V Vin=3.6V 0.35 0.5 0.3 0.4 Rds(on) RDS(ON) 80 Temperature(°C) 0.25 0.3 0.2 0.2 0.15 0.1 0.1 0 Vin=4.2V Vin=3.6V Vin=2.7V 2 3 4 Input Voltage(V) 5 6 20 120 Oscillator Frequency VS Temperature Oscillator Frequency VS Supply Voltage 1.58 1.8 Vin=3.6V Vin=3.6V Oscillator Frequency(MHz) Oscillator Frequency(MHz) 70 Temperature(°C) 1.7 1.6 1.5 1.4 1.3 1.56 1.54 1.52 1.50 1.2 2 3 4 Supply Voltage(V) 20 5 40 60 80 100 120 140 Temperature(°C) Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 9 PAM2306 Dual High-Efficiency PWM Step-Down DC-DC Coverter 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. Load 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 PAM2306 Dual High-Efficiency PWM Step-Down DC-DC Coverter Application Information The basic PAM2306 application circuit is shown in Page 1. External component selection is determined by the load requirement, selecting L first and then Cin and Cout. 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: 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 1 ö 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 (1) 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. 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 1.2V 1.5V 1.8V 2.5V 3.3V L 2.2μH 2.2μH 2.2μH 4.7μH 4.7μH 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. C IN and C OUT Selection Thermal consideration 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 )ùû CIN required IRMS @ IOMAX ë VIN Thermal protection limits power dissipation in the PAM2306. 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. 1 2 For continuous operation, the junction temperature should be maintained below 125°C. The power dissipation is defined as: 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. PD =IO 2 VORDSONH + (VIN -VO )RDSONL VIN + (t SW FSIO +IQ )VIN 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 PAM2306 Dual High-Efficiency PWM Step-Down DC-DC Coverter 100% Duty Cycle Operation For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dis sipation reduces to: 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: 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 = 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 TJ(MAX) -TA The reference and the circuit remain reset until the VIN crosses its UVLO threshold. 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 DFN3X3 is 60°C/W. The maximum power dissipation at T A = 25°C can be calculated by following formula: The PAM2306 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 P D=(125°C-25°C)/60°C/W=1.66W 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. 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 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. The output voltage is given by Table 1. Table 1: Resistor selection for output voltage setting Vo R1 R2 1.2V 100k 100k 1.5V 150k 100k 1.8V 200k 100k 2.5V 380k 120k 3.3V 540k 120k Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 12 PAM2306 Dual High-Efficiency PWM Step-Down DC-DC Coverter PCB Layout Check List When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the PAM2306. 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 Figure 1 :PAM2306 Suggested Layout Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 13 PAM2306 Dual High-Efficiency PWM Step-Down DC-DC Coverter Ordering Information PAM 2306 X X X v 1 v 2 Output Voltage 2 Output Voltage 1 Number of Pins Package Type Pin Configuration Pin Configuration A Type Package Type Number of Pins Y: WDFN 3x3 P: 12 Output Voltage v1 v2 K: 3.3V K: 3.3V 1. VIN2 H: 2.8V H: 2.8V 2. LX2 G: 2.5V G: 2.5V 3. GND E: 1.8V E: 1.8V 4. FB1 C: 1.5V C: 1.5V 5. NC1 B: 1.2V B: 1.2V 6. EN1 A: Adj A: Adj 7. VIN1 8. LX1 9. GND 10. FB2 11: NC2 12 :EN2 Part Number PAM2306AYPv1v2 Marking 2306v1v2 XXXYW Package Type Standard Package WDFN3x3-12 3,000 Units/Tape&Reel Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 14 PAM2306 Dual High-Efficiency PWM Step-Down DC-DC Coverter Outline Dimensions 3x3 mm WDFN 12 2 1 2 1 DETAIL A Pin #1 ID and Tie Bar Mark Options Note :The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 0.700 0.800 0.028 0.031 A1 0.000 0.050 0.000 0.002 A3 0.175 0.250 0.007 0.010 b 0.150 0.250 0.006 0.010 D 2.950 3.050 0.116 0.120 D2 2.300 2.650 0.091 0.104 E 2.950 3.050 0.116 0.120 E2 1.400 1.750 0.055 0.069 e L 0.450 0.350 0.018 0.450 0.014 0.018 Power Analog Microelectronics , Inc www.poweranalog.com 07/2008 Rev 1.0 15