PAM2306D 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 PAM2306D is a dual step-down currentmode, DC-DC converter. At heavy load, the constant-fr equency PWM control performs excellent stability and transient response. To ensure the longest battery life in portable applications, the PAM2306D provides a powersaving Pulse-Skipping Modulation (PSM) mode to r ed uc e q ui e sc e nt c u r r en t un de r li gh t l oa d operation. The PAM2306D 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 adjustmen t. All versions employ internal power switch and synchronous rectifier for to minimize external part c o u n t a n d r e a l i z e h i g h e ff i c i e n c y. D u r i n g shutdown, the input is disconnected from the output and the shutdown current is less than 0.1 μA. 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 VOUT2 V IN2 PAM2306D 1 V IN2 2 C IN2 4.7μF 3 R12 4 5 CFw1 100 pF R11 6 EN2 12 LX2 NC2 G ND FB2 FB1 G ND NC1 LX1 E N1 V IN1 R21 C FW2 100 pF 11 10 9 R22 8 C IN1 4.7 μF 7 V IN1 L1 V OUT1 C OUT1 10μF ( VOUTx = VREF 1 + Rx1 Rx2 ) Power Analog Microelectronics, Inc www.poweranalog.com 02/2012 Rev1.1 1 PAM2306D Dual High-Efficiency PWM Step-Down DC-DC Coverter Block Diagram 1 . 5M OSC + SLOPE COMP VINx IAMP - OSC FBx R1 MAIN SWITCH( PCH ) S Q FREQ SHIFT EA + R2 COMP SWITCHING LOGIC AND RS LATCH BLANKING CIRCUIT R Q ANTI SHOOTTHRU SYNCHRONOUS RECTIFIER ( NCH ) VIN E Nx 0. 6VREF + IRCMP SHUTDOWN L Xx GND - Power Analog Microelectronics, Inc www.poweranalog.com 02/2012 Rev1.1 2 PAM2306D Dual High-Efficiency PWM Step-Down DC-DC Coverter Pin Configuration and Marking Information TOP VIEW WDFN-12L 3x3 VIN2 1 12 E N2 LX2 2 11 N C2 GND 3 10 F B2 F B1 4 9 GND N C1 5 8 LX1 EN 1 6 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. 1 2 3,9, Exposed Pad 4 5,11 Pin Name VIN2 LX2 GND Pin Function Power Input of Channel 2. Pin f or Switching of Channel 2. Ground.The exposed pad must be soldered to a large PCB and connected to GND f or maximum power dissipation. FB1 NC1,NC2 Feedback of Channel 1. No Connection 6 EN1 Chip Enable of Channel 1 (Active High).VEN1 ≤VIN1. 7 8 VIN1 LX1 Power Input of Channel 1. Pin for Switching of Channel 1. 10 12 FB2 EN2 Feedback of Channel 2. Chip Enable of Channel 2 (Active High).VEN2 ≤VIN2. Power Analog Microelectronics, Inc www.poweranalog.com 02/2012 Rev1.1 3 PAM2306D 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 E N1, FB1, LX1, EN2, FB 2 and LX2 Pin Voltage....... -0.3V to (V IN+0.3V) Maximum 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 Symbol Package Maximum Unit Thermal Resis tance (Junction to ambient) θJA WDFN 3x3-12 60 °C/W Thermal Res istance (Junc tion to case) θJ C WDFN 3x3-12 8.5 °C/W Power Dissipation PD WDFN 3x3-12 1.66 W Power Analog Microelectronics, Inc www.poweranalog.com 02/2012 Rev1.1 4 PAM2306D Dual High-Efficiency PWM Step-Down DC-DC Coverter Electrical Characteristic O TA =25 C, VIN =3.6V, VO =1.8V, CIN =10µF, CO =10µF, L=2.2µH, unless otherwise noted. PARAMETER SYMBOL Test Conditions MIN TYP Input Voltage Range VIN 2.5 Regulated Feedback Voltage V FB 0.588 Reference Voltage Line Regulation ΔVF B Regulated Output Voltage Accuary VO IO = 100mA Peak Inductor Current IPK V IN=3V ,V FB = 0.5V or V O=90% 1.5 0.6 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 Output Voltage Load Regulation LDR IO=1mA to 1A 1.5 Quiescent Current (per channel) IQ No load 40 70 µA Shutdown Current (per channel) ISD V EN = 0V 0.1 1 µA 1.5 1.8 MHz Oscillator Frequenc y fOSC V O = 100% 1.2 V FB = 0V or V O = 0V IDS =100mA 0.5 % /V % 500 kHz P MOSFET 0.3 0.45 Ω N MOSFET 0.35 0.5 Ω ±0.01 1 µA Drain-Sourc e On-State Resistance RDS(O N) SW Leakage Current (per channel) ILSW EN Threshold High V EH EN Threshold Low V EL EN Leak age Current IEN ±0.01 µA Over Temperature Protection OTP 150 °C OTP Hys teresis OTH 30 °C 1.5 V 0.3 V Power Analog Microelectronics, Inc www.poweranalog.com 02/2012 Rev1.1 5 PAM2306D Dual High-Efficiency PWM Step-Down DC-DC Coverter Typical Performance Characteristics TA =25 °C , CIN =10μF, CO =10μF, L=4.7 μH, unless otherwise noted. Efficiency vs Output Current (Vo=1.2V) Efficiency vs Input Voltage (Vo=1.2V) 100 95 90 90 85 80 80 70 75 60 Vin=3.6V Vin=4.2V Vin=5.0V 50 70 40 1 10 100 Io=10mA Io=100mA Io=1000mA 65 60 2.5 1000 3.0 3.5 4.0 4.5 5.0 5.5 Input Voltage(V) Output Current(mA) Efficiency vs Output Current (Vo=1.5V ) Efficiency vs Input Voltage (Vo=1.5V) 100 95 90 90 85 80 80 70 75 60 70 Vin=3.6V Vin=4.2V Vin=5.0V 50 65 60 2.5 40 1 10 100 Io=10mA Io=100mA Io=1000mA 1000 3.0 3.5 Output Current(mA) 4.0 4.5 Input Voltage(V) 5.0 5.5 Eifficiency vs Input Voltage (Vo=1.8V) Efficiency vs Output Current (Vo=1.8V) 100 95 90 90 85 80 80 70 75 60 70 Vin=3.6V Vin=4.2V Vin=5.0V 50 65 60 2.0 40 1 10 100 Io=10mA Io=100mA Io=1000mA 1000 Output Current(mA) 3.0 4.0 5.0 6.0 Input Voltage(V) Power Analog Microelectronics, Inc www.poweranalog.com 02/2012 Rev1.1 6 PAM2306D Dual High-Efficiency PWM Step-Down DC-DC Coverter Typical Performance Characteristics TA =25 °C , CIN =10μF, CO =10μF, L=4.7 μH, unless otherwise noted. Efficiency vs Output Current (Vo=2.5V) Efficiency vs Input Voltage (Vo=2.5V) 100 96 92 90 88 80 84 80 70 76 60 72 Vin=3.6V Vin=4.2V Vin=5.0V 50 64 40 1 10 100 Output Current(mA) 60 2.5 1000 100 95 95 90 90 85 85 80 80 75 75 5.5 65 60 4.0 60 10 100 Output Current(mA) Io=10mA Io=100mA Io=1000mA 70 Vin=4.2V Vin=5.0V Vin=5.5V 1 4.5 Efficiency vs Input Voltage (Vo=3.3V) 100 65 3.5 Input Voltage(V) Efficiency vs Output Current (Vo=3.3V ) 70 Io=10mA Io=100mA Io=1000mA 68 1000 4.5 5.0 Input Voltage(V) 5.5 Rdson vs Input Voltage Quiescent Current vs Input Voltage 43 0.36 42 0.34 41 Vout=1.2V Vout=2.5V Vout=3.3V 0.32 40 0.3 39 0.28 38 Vout=1.2V Vout=1.8V Vout=3.3V 37 0.26 36 2.5 3 3.5 4 4.5 Input Votage(V) 5 0.24 2.5 5.5 3 3.5 4 4.5 Input Votage(V) 5 5.5 Power Analog Microelectronics, Inc www.poweranalog.com 02/2012 Rev1.1 7 PAM2306D Dual High-Efficiency PWM Step-Down DC-DC Coverter Typical Performance Characteristics TA =25 °C , CIN =10μF, CO =10μF,,Vo=1.2V, L=4.7 μH, unless otherwise noted. Reference Voltage vs Load Current Output Voltage vs Load Current 614 1. 235 612 1. 230 610 1. 225 608 1. 220 606 1. 215 604 602 1. 210 Vin=3.6V Vin=4.2V Vin=5.0V 600 Vin=3.6V Vin=4.2V Vin=5.0V 1. 205 598 1. 200 0 200 400 6 00 800 0 1000 200 400 600 800 1000 Output Current(m A ) Output Current(mA) Oscillator Frequency vs Supply Voltage Oscillator Frequency vs Temperature 1.58 1.8 Vo=1.2V 1.7 1.56 1.6 1.5 1.54 1.4 1.52 1.3 1.2 1.50 2 3 4 5 Supply Voltage(V) 6 7 20 40 60 80 100 120 140 Temperature(℃） Load Transient Io=0-1A, Vo=3.3V, Vin=5V Load Transient Io=0-1A, Vo=1.2V, Vin=5V Output Current Output Current Output Voltage Output Voltage Power Analog Microelectronics, Inc www.poweranalog.com 02/2012 Rev1.1 8 PAM2306D Dual High-Efficiency PWM Step-Down DC-DC Coverter Application Information The basic PAM2306D 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 VOUT V OUT 1 (f )(L ) V IN 1 V VOUT @VI L ESR+ 8fCO UT 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 ΔIL increases with input voltage. (1) 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. 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: Thermal protection limits power dissipation in the PAM2306D. 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. 2 VOUT (VIN - VO UT ) C IN required IRMS @ IOMAX VIN 1 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 IR MS = IOU T / 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 + (tSW FSIO +IQ )VIN IQ 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 02/2012 Rev1.1 9 PAM2306D Dual High-Efficiency PWM Step-Down DC-DC Coverter For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dis sipation reduces to: 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 th e voltag e d rop ac ros s the P - c hannel transistor: 2 PD =IO R DSONH +IQ VIN Since RDS(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 de pend s on th e ther ma l r esi sta nc e 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 Rdson = P-channel switch ON resistance, IL O A D = O ut pu t c u rr e n t, RL = I nd uc t or 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 θJA 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 θJA of WDFN3X3 is 60°C/W. The maximum power dissipation at T A = 25°C can be calculated by following formula: The PAM2306D 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: R1 V O=0.6×1+ R2 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 02/2012 Rev1.1 10 PAM2306D 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 PAM2306D. 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 c onnected between the (+) plate of COUT 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 :PAM2306D Suggested Layout Power Analog Microelectronics, Inc www.poweranalog.com 02/2012 Rev1.1 11 PAM2306D Dual High-Efficiency PWM Step-Down DC-DC Coverter Ordering Information PAM 2306D X X v 1 v 2 Output Voltage 2 Output Voltage 1 Number of Pins Package Type Package Type Number of Pins Y: WDFN 3x3 P: 12 Part Number PAM2306DYPv1 v2 Marking 2306Dv1 v2 X XXYW Output Voltage v1 v2 A: Adj A: Adj Package Type Standard Package WDFN3x3-12 3,000 Units/Tape&Reel Power Analog Microelectronics, Inc www.poweranalog.com 02/2012 Rev1.1 12 PAM2306D 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 isoptional, 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 02/2012 Rev1.1 13