PAM2320 3A Low Noise Step-Down DC-DC Converter Features n n n n n n n n n n n n n Description T h e PA M 2 3 2 0 i s a 3 A s t e p - d o w n D C - D C converter. At heavy load, the constant-frequency PWM control performs excellent stability and transient response. No external compensation components are required. Output Current: Up to 3A Output Voltage: 0.6V to V IN Input Voltage: 2.7 to 5.5V Efficiency up to 95% 42 μA (Typ) No Load Quiescent Current Shutdown Current: <1 μA 100% Duty Cycle Operation 1.5MHz Switching Frequency Internal Soft Start No external Compensation Required Current Limit Protection Thermal Shutdown PSOP-8 Package The PAM2320 supports a range of input voltages from 2.7V to 5.5V, allowing the use of a single L i + /L i - p o l y m e r c e l l , m u l ti p l e A l k a l i n e /N i M H cell,and other standard power sources. The output voltage is adjustable from 0.6V to the input voltage. The PAM2320 employs internal power switch and synchronous rectifier 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 1 μA. Other key features include over-temperature and short circuit protection, and under-voltage lockout to prevent deep battery discharge. Applications n n n n n n 5V or 3.3V Point of Load Conversion Telecom/Networking Equipment Set Top Boxes Storage Equipment Video Cards DDR Power Supply The PAM2320 delivers 3A maximum output current while consuming only 42μA of no-load quiescent current. Ultra-low RDS(ON) integrated MOSFETs and 100% duty cycle operation make the PAM2320 an ideal choice for high output voltage, high current applications which require a low dropout threshold. The PAM2320 is available in PSOP8 package. Typical Application L VIN VO VIN (2) CIN (3)SW PAM2320 PAM 2310 40uF 22uF R1 Cf w 100p EN(7) Co (5)FB 22uF 30uF 0 R2 NC (1,6,8) GND(4) 0 0 0 R1 VO = 0.6 1+ R2 Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 1 PAM2320 3A Low Noise Step-Down DC-DC Converter Block Diagram 1.5M OSC SLOPE COMP FREQ SHIFT OSC + IAMP - VIN FB MAIN SWITCH( PCH) S Q R1 RS LATCH R2 SWITCHING LOGIC AND BLANKING CIRCUIT R Q VIN + EA ANTI SHOOT THRU SW COMP SYNCHRONOUS EN + RECTIFIER (NCH ) IRCMP - 0.6VREF SHUTDOWN GND Pin Configuration & Marking Information Top View PSOP-8 NC NC VIN EN SW NC GND FB P2320:PAM2320 A: Adjustable Output X: Internal Code Y: Year W: Week (Exposed Pad) Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 2 PAM2320 3A Low Noise Step-Down DC-DC Converter Pin Description Name P in Number Function NC 1 No Connected VIN 2 B ias s upply. Chip main power supply pin SW 3 The drains of the internal main and synchronous power MOSFET. GND 4 GND FB 5 Feedback voltage to internal error amplifier, the threshold voltage is 0.6V. NC 6 No Connected EN 7 NC 8 E nable control input. Force this pin voltage above 1.5V, enables the chip, and below 0.3V shuts down the device. No Connected 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 V I N ......................................6V SW Pin Voltage......................-0.3V to (V IN+0.3V) FB Pin Voltage.........................-0.3V to (V IN+0.3V) EN Pin Voltage....................................- 0.3V to 6V Maximum Junction Temperature..................150°C Storage Temperature Range...........-65°C to 150°C Soldering Temperature.......................300°C, 5sec Recommended Operating Conditions Supply Voltage..................................2.7V to 5.5V Junction Temperature Range..........-40 °C to 125 °C Ambient Temperature Range...........-40 °C to 85 °C Thermal Information Parameter Symbol Package Maximum Unit Thermal Resistance (Junction to Ambient) θJA PSOP-8 90 °C/W Thermal Resistance (Junction to Case) θJC PSOP-8 11 °C/W Internal Power Diss ipation (@TA=25°C) PD PSOP-8 1100 mW Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 3 PAM2320 3A Low Noise Step-Down DC-DC Converter Electrical Characteristic TA =25 °C , Vin=3.6V, Vo=1.8V, Cin=33uF,Co=22uF, L=2.2uH, unless otherwise noted. PARAMETER SYMBOL Test Conditions MIN TYP MAX UNITS Input Voltage Range VIN 2.7 5.5 V Output Voltage Range VO 0.6 V IN V 2.5 V UVLO Threshold VUV LO V IN Rising 2.4 Hys teresis 240 V IN Falling Regulated Output Voltage Accuary VO Regulated Feedback Voltage VF B FB Leak age Current IF B mV 1.8 IO = 0 to 3A V -3 0.591 0.6 V O=1V +3 % 0.609 V 0.2 µA Output Voltage Line Regulation LNR V IN = 2.5V to 5V 0.2 %/V Output Voltage Load Regulation LDR IO=0A to 3A 0.5 %/A 42 Quiescent Current IQ No load Shutdown Current IS D V E N = 0V Current Limit ILIM Oscillator Frequency fO SC Drain-Source On-State Resistanc e η Analog Soft Start Time tS EN Threshold High VE H EN Threshold Low VE L EN Leakage Current IE N µA 1 µA 4 1.2 RDS (ON) High Efficiency 90 1.5 A 1.8 High Side 85 mΩ Low Side 60 mΩ 95 % 0.5 ms From enable to output regulation 1.5 V IN =VEN = 0V MHz V -1.0 0.3 V 1.0 µA Over Temperature Protection OTP 150 °C OTP Hysteresis OTH 30 °C Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 4 PAM2320 3A Low Noise Step-Down DC-DC Converter Typical Performance Characteristics TA =25 °C , CIN =33uF,Co=22 μF unless otherwise noted. Efficienvy VS Input Voltage (Vo=1.2V) Efficiency vs Output Current (Vo=1.2V) 100% 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 90% 80% 70% 60% 50% 40% 30% 3.3V 4.2V 5V 20% 10% 0% 1 10 100 1000 Output Current (m A) 10000 0.1A 1A 3A 2 Efficiency vs Output Current (Vo=1.8V ) 70% 60% 50% 40% 30% 3.3V 4.2V 5V 0% 10 100 1000 10000 2 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 2.5 100 3 3.5 4 4.5 5 5.5 6 5.5 6 Efficienvy VS Input Voltage (Vo=3.3V) 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 4.2V 5V 5.5V 10 5 Input Voltage (V) Efficiency vs Output Current (Vo=3.3V) 1 4.5 0.1A 1A 3A Output Current (m A) 110% 100% 4 Efficienvy VS Input Voltage (Vo=1.8V) 80% 1 3.5 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 90% 10% 3 Input Voltage (V) 100% 20% 2.5 1000 10000 Output Current (mA) 0.1A 1A 3A 3 3.5 4 4.5 5 5.5 6 Input Voltage (V) Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 5 PAM2320 3A Low Noise Step-Down DC-DC Converter Typical Performance Characteristics TA =25 °C , CIN =33uF,Co=22 μF unless otherwise noted. Output Voltage vs Output Current (Vo=1.2V) Load Regulation (Vo=1.2V) 1.2 0.1% 1 .195 -0.1% -0.3% 1.19 -0.5% 1 .185 -0.7% 1.18 -0.9% 1 .175 -1.1% 1.17 1 .165 3.3V 4.2V -1.4% 5V -1.8% 3.3V 4.2V 5V -1.6% -2.0% 1.16 0 5 00 1000 1500 2000 Output Current (mA) 2 500 1 3000 Output Voltage vs Output Current ( Vo=1.8V ) 10 100 1000 Output Current (mA) 10000 Load Regulation (Vo=1.8V) 1.82 0.0% -0.2% 1.81 -0.4% -0.6% 1.8 -0.8% 1.79 -1.0% -1.2% 1.78 -1.4% 3.3V 4.2V 5V 1.77 3.3V 4.2V 5V -1.6% -1.8% 1.76 -2.0% 0 500 1000 1500 2000 Output Current (mA) 2500 3000 1 10 100 1000 10000 Output Current (mA) Output Voltage vs Output Current ( Vo=3.3V ) Load Regulation (Vo=3.3V) 3.29 0.1% 3.285 -0.2% 3.28 -0.4% 3.275 -0.6% 3.27 4.2V 5V 5.5V 3.265 -1.0% 3.26 0 500 4.2V 5V 5.5V -0.8% 1000 1500 2000 2500 1 3000 10 100 1000 10000 Output Current (mA) Output Current (mA) Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 6 PAM2320 3A Low Noise Step-Down DC-DC Converter Typical Performance Characteristics TA =25 °C , CIN =33uF,Co=22 μF unless otherwise noted. Quiescent Current VS Input Voltage Rdson VS Input Voltage 44 110 42 100 40 90 38 80 36 70 34 Vo1.2V Vo1.8V Vo3.3V 32 60 30 P-0.1A N-0.1A 50 2 2.5 3 3.5 4 4.5 5 5.5 6 2 2.5 3 Input Voltage (V) 3.5 4 4.5 5 5.5 6 Input Voltage (V) Oscillator Frequency VS Input Voltage Oscillator Frequency VS Temperature 1.58 1.50 1.48 1.46 1.56 1.44 1.42 1.40 1.54 1.38 1.36 1.52 1.34 Io=3A 1.32 Vin=3.6V 1.30 1.50 2.5 3 3.5 4 4.5 5 5.5 20 40 Input Voltage(V) 60 80 100 120 140 Temperature(℃） Reference Voltage VS Temperature Reference Voltage VS Input Voltage 0.602 0.6 0.600 0.598 0.598 0.596 0.596 0.594 0.592 0.594 0.59 0.592 0.588 0.590 0.586 0.588 I =100mA 0.584 I =600mA 0.586 0.582 I =800mA 0.584 0.58 2 3 4 Input Voltage 5 6 25 50 75 100 125 150 Tem perature Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 7 PAM2320 3A Low Noise Step-Down DC-DC Converter Application Information The basic PAM2320 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 3.3µH. Its value is chosen based on the desired ripple current and efficiency. 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 3A reasonable starting point for setting ripple current is △I L = 1.2A (40% of 3A). DIL = 1 VOUT V OUT 1 (f )(L ) V IN △Vout≈△IL(ESR+1/8fCout) Where f = operating frequency, C OUT=output capacitance and ΔI L = ripple current in the inductor. For a fixed output voltage, the output ripple is highest at maximum input voltage since Δ IL 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 4.2A rated inductor should be enough for most applications (3A + 1.2A). For better efficiency, choose a low DC-resis tance inductor. Vo 1.2V 1.5V 1.8V 2.5V 3.3V L 1µH 1.5µH 2.2µH 2.2µH 3.3µH When choosing the input and output ceramic capacitors, choose the X5R or X7R dielectric formul ations. 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 PAM2320. 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 I R M S= I O U 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 advis able 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. VORDSONH + (VIN -VO )RDSONL + (tSW FSIO +IQ )VIN VIN I Q is the step-down converter quiescent current. The term tsw is used to estimate the f ull load step-down converter switching losses. PD =IO 2 Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 8 PAM2320 3A Low Noise Step-Down DC-DC Converter 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 O PD =I RDSON H +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 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: TJ(MAX) -TA PD = 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 SOP-8(EP) 90°C/W respec tively. The maximum power dissipation at T A = 25°C can be calculated by following formula: V OUT = V IN –I LOAD (R dson + R L) where R dson = P-channel switch ON resistance, I L O A D = O ut pu t c u rr e n t, R L = I nd uc t or DC resistance UVLO and Soft-Start The reference and the circuit remain reset until the VIN crosses its UVLO threshold. The PAM2320 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 make the output voltage rise up smoothly. Short Circuit Protection P D=(125°C-25°C)/90°C/W=1.11W(SOP-8) The switch peak current is limited cycle-by-cycle to a typical value of 4A. In the event of an output voltage short circuit, the device operates with a frequency of 500kHz and minimum duty cycle, therefore the average input current is more smaller than current limit. Setting the Output Voltage The internal reference is 0.6V (Typical). The output voltage is calculated as below: The output voltage is given by Table 1. 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. R1 V O=0.6×1+ R2 Table 1: Resistor recommend for output voltage setting Vo R1 R2 1.2V 150k 150k 1.5V 225k 150k 1.8V 300k 150k 2.5V 475k 150k 3.3V 680k 150k Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 9 PAM2320 3A Low Noise Step-Down DC-DC Converter Ordering Information PAM 2320 X X X xxx X Shipping Package Output Voltage Number of Pins Package Type Pin Configuration Pin Configuration B Type Package Type Num ber of Pins E: PSOP-8 C: 8 Output Voltage ADJ: Adj 8 pins Par t Number Output Voltage Package Type Shipping Package PAM2320BECADJR ADJ PS OP-8 2,500 Units /Tape & Reel Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 10 PAM2320 3A Low Noise Step-Down DC-DC Converter Outline Dimensions PSOP-8 Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 11