PAM2301 800mA Step-Down DC-DC Converters Features n n n n n n n n n n n General Description The PAM2301 is a step-down current-mode, DCDC 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 1 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 to save power. Efficiency up to 96% Only 40μA(TYP.) Quiescent Current Output Current: Up to 800mA Internal Synchronous Rectifier 1.5MHz Switching Frequency Soft Start Under-Voltage Lockout Short Circuit Protection Thermal Shutdown 5-pin Small SOT23-5 Package Pb-Free Package The PAM2301 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 output voltage is adjustable from 0.6V to the input voltage, while the part number suffix PAM2301XX indicates pre-set output voltage of 3.3V, 2.8V, 2.5V, 1.8V, 1.5V, 1.2V or adjustable. All versions employ internal power switch and synchronous rectifierfor 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 n n n Cellular Phone Portable Electronics Wireless Devices Cordless Phone Computer Peripherals Battery Powered Widgets Electronic Scales Digital Frame The PAM2301 is available in SOT23-5 package. Typical Application Fixed Output Voltage V IN C IN 10μF 4 VIN SW 1 EN VOUT 3 4 . 7μH 5 Adjustable Output Voltage Vo V IN Co 10μF C IN 10μF 4 VIN SW 3 4 . 7μH R1 1 EN FB 5 Vo 20pF Co 10μF R2 GND GND 2 2 R1 ö æ VO = 0.6 ´ ç1 + ÷ è R2 ø Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 1 PAM2301 800mA Step-Down DC-DC Converters Block Diagram 1.5M OSC + IAMP - VIN + - + SLOPE COMP PWM COMP FB FREQ SHIFT OSC S Q R1 R Q RS LATCH R2 EA + VIN MAIN SWITCH ( PCH ) SWITCHING LOGIC AND BLANKING CIRCUIT ANTI SHOOT THRU COMP 0.6VREF EN SW SYNCHRONOUS RECTIFIER ( NCH ) + IRCMP - SHUTDOWN GND Pin Configuration& Marking Information Top View SOT23 - 5 VIN VOUT/FB 5 4 BA V Y W 1 2 3 EN GND SW BA: Product Code of PAM2301 V: Output Voltage Y: Year W: Week Pin Number Name Function 1 EN 2 GND 3 SW The drains of the internal main and synchronous power MOSFET. 4 VIN Chip main power supply pin Enable control input. Force this pin voltage above 1.5V, enables the chip, and below 0.3V shuts down the device. Ground VOUT: Output voltage feedback pin, an internal resistive divider divides the 5 VOUT/FB output voltage down for comparison to the internal reference voltage. FB: Feedback voltage to internal error amplifier, the threshold voltage is 0.6V. Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 2 PAM2301 800mA Step-Down DC-DC Converters 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 . Junction Temperature................................125 OC Storage Temperature Range........-65 OC to 150 OC Soldering Temperature......................300 OC, 5sec Input Voltage..................................-0.3V to 6.6V EN, FB Pin Voltage.............................- 0.3V to V IN SW Pi n Voltage.....................- 0.3V to ( V IN+0.3V ) Recommended Operating Conditions Ambient Temperature Range..........-40 OC to 85 OC Supply Voltage................................2.5V to 5.5V Max. Supply Voltage (for Max. duration of 30 minutes)................................................6.0V Thermal Information Parameter Thermal Resistance (Junction to Case) Thermal Resistance (Junction to Ambient) Internal Power Dissipation Package Symbol Maximum SOT23-5 θJC 130 Unit °C/W SOT23-5 θJA 250 SOT23-5 PD 400 mW Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 3 PAM2301 800mA Step-Down DC-DC Converters Electrical Characteristic T A=25 OC, V IN=3.6V, V O=1.8V, C IN=10μF, C O=10μF,L=4.7μH, unless otherwise noted. PARAMETER SYMBOL Test Conditions MIN Input Voltage Range VIN 2.5 Regulated Feedback Voltage VFB 0.588 Reference Voltage Line Regulation ΔV FB Regulated Output Voltage Accuary VO Peak Inductor Current IPK TYP 0.6 MAX UNITS 5.5 V 0.612 V 0.3 IO = 100mA -3 VIN=3V,VFB = 0.5V or %/V +3 1.2 VO=90% % A Output Voltage Line Regulation LNR VIN = 2.5V to 5V, IO=10mA 0.2 0.5 %/V Output Voltage Load Regulation LDR IO=1mA to 800mA 0.5 1.5 % Quiescent Current IQ No load 40 70 μA Shutdown Current ISD VEN = 0V 0.1 1 μA Oscillator Frequency fOSC 1.5 1.8 MHz Drain-Source On-State Resistance SW Leakage Current High Efficiency VO = 100% 1.2 VFB = 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 RDS(ON) IDS =100mA % EN Threshold High VE H 1.5 V EN Threshold Low VEL 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 09/2008 Rev 1.3 4 PAM2301 800mA Step-Down DC-DC Converters Typical Performance Characteristics O 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(%) Eifficiency(%) T A=25 C, C IN=10 μ F, C O=10uF,L=4.7 μ H, unless otherwise noted. 80 70 60 50 40 Vin=2.7V Vin=3.6V 2.5V 3.6V 30 Vin=4.2V 4.2V 20 1 10 100 1 1000 90 90 80 80 70 60 50 70 60 50 40 2.5V 3.6V 3V 3.6V 30 4.2V 20 4.2V 20 1 10 100 Output Current(mA) 1 1000 80 70 Eifficiency(%) 80 70 60 50 3V 3.6V 60 50 40 30 20 Vin=3.6V Vin=4.2V Vin=5.0V 10 4.2V 20 1000 Eifficiency VS Output Current (Vo=3.3V) 90 30 100 100 90 40 10 Output Current(mA) Efficiency VS Output Current (Vo=2.8V) 100 Efficiency(%) 1000 Efficiency VS Output Current ( Vo=2.5V ) 100 Efficiency(%) Efficiency(%) Efficiency VS Output Current ( Vo=1.8V ) 100 30 100 Output Current(mA) Output Current(m A) 40 10 0 1 10 100 1 1000 10 100 1000 Output Current(mA) Output Current(mA) Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 5 PAM2301 800mA Step-Down DC-DC Converters Typical Performance Characteristics O T A=25 C, C IN=10 μ F, C O=10uF,L=4.7 μ H, unless otherwise noted. 100 90 90 80 70 80 Efficiency(%) Eifficiency (%) Efficiency VS Input Voltage ( Vo=1.2V ) 100 60 50 40 Efficiency VS Input Voltage ( Vo=1.5V ) 70 60 50 30 20 10mA 40 Io=10mA 800mA Io=100mA 10 0 30 Io=800mA 2.5 100mA 2.5 3.5 4.5 Input Voltage(V) 3.5 5.5 100 90 90 80 80 Efficiency(%) 100 70 60 4.5 5 Efficiency VS Input Voltage ( Vo=2.5V ) 70 60 50 50 10mA 10mA 40 40 100mA 100mA 800mA 800mA 30 30 2.5 3 3.5 4 4.5 3 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 Input Voltage(V) Efficiency VS Input Voltage ( Vo=1.8V ) Efficiency(%) 3 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 09/2008 Rev 1.3 6 PAM2301 800mA Step-Down DC-DC Converters Typical Performance Characteristics O T A=25 C, C IN=10 μ F, C O=10uF,L=4.7 μ H, unless otherwise noted. Output Voltage VS Load Current Reference Voltage VS Input Voltage 1.215 0.602 Vin=3.6V 0.600 1.210 Output Voltage(V) 0.598 0.596 Vfb 0.594 0.592 0.590 0.588 I=100mA I=600mA 0.586 1.200 1.195 1.190 1.185 Vo=1.2V 1.180 Vin=3.6V I=800mA 0.584 1.175 2 3 4 Input Voltage 5 6 0 200 400 Load Current(mA) 600 800 Output Voltage VS Temperature Reference Voltage VS Temperature 0.620 1.194 1.193 0.615 Output Voltage(V) Reference Voltage(V) 1.205 0.610 0.605 0.600 1.192 1.191 Vin=3.6V 0.595 1.189 0.590 1.188 0 50 100 Vo=1.2V 1.19 Io=100mA 20 150 40 60 80 100 120 140 Temperature(℃） Tem perature(℃） Output Voltage VS Output Current Reference Voltage VS Load Current 1.205 0.604 Vo=1.2V 1.203 0.6 Output Voltage(V) 1.201 Vfb 0.596 0.592 0.588 1.199 1.197 1.195 1.193 2.5V 1.191 4.2V 3.6V Vin=2.7V 0.584 Vin=3.6V 5V Vin=4.2V 1.189 0.58 0 200 400 600 10 800 Load Current 110 210 310 410 510 610 710 810 Output Current(mA) Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 7 PAM2301 800mA Step-Down DC-DC Converters 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 ILoad=0A 10 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(℃） 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 5 20 6 120 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(℃) 1.7 1.6 1.5 1.4 1.3 1.2 1.56 1.54 1.52 1.50 2 3 4 5 Supply Voltage(V) 6 7 20 40 60 80 100 120 140 Temperature(℃） Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 8 PAM2301 800mA Step-Down DC-DC Converters 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. Load Transient Io=0-800mA Vo=1.8V Vin=3.6V Load Transient Io=50-800mA Vo=1.8V Vin=3.6V Voltage Output Voltage Output Inductor Current Inductor Current Output Current Output Current Start-up from Shutdown Vo=1.8V,Vin=3.6V Load Transient Io=200-800mA Vo=1.8V Vin=3.6V Voltage Output Voltage Output Inductor Current Enable Output Current Inductor Current Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 9 PAM2301 800mA Step-Down DC-DC Converters Application Information The basic PAM2301 application circuit is shown in Page 1. External component selection is determined by the load requirement, selecting L first and then Cin and Cout. 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: 1 ö æ VVOUT @VIL ç ESR+ ÷ 8fCOUT ø è 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 = 320mA (40% of 800mA). DIL = æ VOUT ö VOUT ç 1÷ f L VIN ø ( )( ) è 1 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. (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 1120mA rated inductor should be enough for most applications (800mA + 320mA). For better efficiency, choose a low DC-resis tance inductor. 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 Cout 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 )ùû CIN required IRMS @ IOMAX ë VIN Setting the Output Voltage The internal reference is 0.6V (Typical). The output voltage is calculated as below: R1 ö æ VO = 0.6 ´ ç1 + ÷ è R2 ø 1 2 The output voltage is given by Table 1. Table 1: Resistor selection for output voltage setting This formula has a maximum at VIN =2Vout, where I R M S =Iout/2. This simple worst-case 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. The selection of Cout is driven by the required effective series resistance (ESR). 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 09/2008 Rev 1.3 10 PAM2301 800mA Step-Down DC-DC Converters 100% Duty Cycle Operation PCB Layout Check List 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: When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the PAM2301. 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 V FB pin connect directly to the feedback resistors? The resistive divider R1/R2 must be con nected 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 VFB node. 5. Keep the (–) plates of C IN and C OUT as close as possible. 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 PAM2301 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. Figure 1 :PAM2301 Suggested Layout Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 11 PAM2301 800mA Step-Down DC-DC Converters Ordering Information PAM 2301 X X X X xxx Output Voltage Number of Pins Package Type Pin Configuration Output Current Output Current C: 800mA Pin Configuration Package Type Number of Pins A: SOT-23 B: 5 A Type Output Voltage 330: 3.3V 1. EN 280: 2.8V 2. GND 250: 2.5V 3. SW 180: 1.8V 4. VIN 150: 1.5V 5. VOUT/FB 120: 1.2V ADJ: Adj Part Number Output Voltage Marking Package Type Standard Package PAM2301CAAB330 3.3V BAKYW SOT23-5 3,000Units/Tape&Reel PAM2301CAAB280 2.8V BAHYW SOT23-5 3,000Units/Tape&Reel PAM2301CAAB250 2.5V BAGYW SOT23-5 3,000Units/Tape&Reel PAM2301CAAB180 1.8V BAEYW SOT23-5 3,000Units/Tape&Reel PAM2301CAAB150 1.5V BACYW SOT23-5 3,000Units/Tape&Reel PAM2301CAAB120 1.2V BABYW SOT23-5 3,000Units/Tape&Reel PAM2301CAABADJ ADJ BAAYW SOT-23-5 3,000Units/Tape&Reel Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 12 PAM2301 800mA Step-Down DC-DC Converters Outline Dimensions c (REF.) SOT23-5 0.25 D e1 θ L1 (REF.) A2 A1 A E1 E L REF. REF. A A1 A2 c D E E1 L L1 θ b e e1 Min 0 0.70 2.70 2.60 1.40 0º 0.30 Millimeter Nom 1.10MAX 0.05 1.00 0.12REF. 2.90 2.80 1.60 0.45REF. 0.60REF. 5º 0.40 0.95REF. 1.90REF. Max 0.10 1.295 3.10 3.00 1.80 10º 0.50 Power Analog Microelectronics , Inc www.poweranalog.com 09/2008 Rev 1.3 13