PAM2307 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 0 7 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 QFN3x3 16-Pin and SOP-8(EP) Package The PAM2307 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 PAM2307 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 PAM2307 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 PAM2307 an ideal choice for high output voltage, high current applications which require a low dropout threshold. The PAM2307 is available in QFN3x3 16-Pin and SOP-8(EP) package. Typical Application U1 L1 VIN PVIN SW 2 1 VOU T R3 1k VI N C1 22uF C3 R 1 100pF PAM2307 EN C2 FB 22uF C4 1uF TEST R2 R1 VO = 0.6 1+ R2 Power Analog Microelectronics, Inc www.poweranalog.com 03/2011 Rev2.1 1 PAM2307 3A Low Noise Step-Down DC-DC Converter Block Diagram VIN 1.5M OSC SLOPE COMP FREQ SHIFT OSC + IAMP - PVIN FB MAIN SWITCH (PCH ) S Q R1 R Q RS LATCH EA R2 + VIN SWITCHING LOGIC AND BLANKING CIRCUIT ANTISHOOT THRU SW COMP SYNCHRONOUS EN + RECTIFIER (NCH ) IRCMP - 0.6VREF SHUTDOWN GND PGND TEST Pin Configuration & Marking Information Top View QFN 3X3 16L 16 15 14 13 PGND PGND PGND FB PVIN PVIN 10 PVIN 9 VIN 12 1 P2307A XXXYW 2 11 3 4 5 6 7 A: Y: W: X: 8 Pin Configuration Year Week Internal Code Pin Description Name Pin Num ber Function PGND 1-3 FB 4 Feedback voltage to internal error amplifier, the threshold voltage is 0.6V. GND 5 Signal ground for small signal components. NC 6, 16 EN 7 TEST 8 Test Mode(no connect or to Ground) VIN 9 Bias supply. Chip main power supply pin PVIN 10 -12 Input supply for power s tage. Must be c losely decoupled to PGND SW 13 -15 The drains of the internal main and synchronous power MOS FET. Main power ground pin No connection Enable control input. Force this pin voltage above 1.5V, enables the chip, and below 0.3V s huts down t he dev ice. Power Analog Microelectronics, Inc www.poweranalog.com 03/2011 Rev2.1 2 PAM2307 3A Low Noise Step-Down DC-DC Converter Pin Configuration & Marking Information Top View SOP-8(EP) 8 7 6 5 P2307B XXXYW 1 2 3 B: Y: W: X: 4 Pin Configuration Year Week Internal Code Pin Description Name Pin Num ber Function SW 1 The drains of the internal main and synchronous power MOSFET. PGND 2 Main power ground pin FB 3 Feedback voltage to internal error amplifier, the threshold voltage is 0.6V. GND 4 Signal ground for small signal components. EN 5 TEST 6 Test Mode(no connect or to Ground) VIN 7 Bias supply. Chip main power supply pin PVIN 8 Input supply for power stage. Must be closely decoupled to PGND Enable control input. Force this pin voltage above 1.5V, enables the chip, and below 0.3V shuts down t he device. 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 PV IN,V IN......................................6V SW Pin Voltage......................-0.3V to (PV 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..................................2.5V to 5.5V Junction Temperature Range..........-40 °C to 125 °C Ambient Temperature Range...........-40 °C to 85 °C Thermal Information Parameter Symbol Thermal Resistance (Junction to Ambient) θJA Thermal Resistance (Junction to Case) θJC Package Maximum QFN 3x3-16 35 SOP-8(EP) 90 QFN 3x3-16 14 SOP-8(EP) 11 Unit °C/W °C/W Power Analog Microelectronics, Inc www.poweranalog.com 03/2011 Rev2.1 3 PAM2307 3A Low Noise Step-Down DC-DC Converter Electrical Characteristic TA =25 °C , Vin=3.6V, Vo=1.8V, Cin=22uF,Co=22uF, L=2.2uH, unless otherwise noted. PARAMETER SYMBOL Test Conditions MIN TYP MAX UNITS Input Voltage Range V IN 2.5 5.5 V Output Voltage Range VO 0.6 V IN V 2.5 V UVLO Threshold VUVLO V IN Rising 2.4 Hys teresis 240 V IN Falling Regulated Output Voltage Accuary VO Regulated Feedback Voltage VFB FB Leakage Current IFB mV 1.8 IO = 0 to 3A,VIN =2.5 to 5.5V V -2 0.588 0.6 V O=1V +2 % 0.612 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 ISD V EN = 0V Current Limit ILIM Os cillator Frequenc y fO SC Drain-Source On-State Resistance η Start up Time tS EN Threshold High V EH EN Threshold Low VE L EN Leakage Current IEN µA 1 µA 3.5 1.2 RDS(ON) High Efficiency 90 1.5 A 1.8 High Side 0.140 Ω Low Side 0.09 Ω From enable to output regulation 95 % 3 ms 1.5 V IN =V EN = 0V MHz V -1.0 0.3 V 1.0 µA Ov er Temperature Protection OTP 150 °C OTP Hysteresis OTH 30 °C Power Analog Microelectronics, Inc www.poweranalog.com 03/2011 Rev2.1 4 PAM2307 3A Low Noise Step-Down DC-DC Converter Typical Performance Characteristics TA =25 °C , CIN =22*2uF,Co=22 μF unless otherwise noted. Efficiency vs Output Current (Vo=1.2V) Load Regulation (Vo=1.2V) 100 1 90 0.8 80 0.6 Vin=3. 6V Vin=4. 2V 70 Vin=5V 0.4 60 0.2 50 0 40 -0.2 30 Vin=3. 6V 20 Vin=4. 2V 10 Vin=5V 1 10 10 0 1000 10000 -0.4 -0.6 -0.8 0 1 10 100 Output Curren t(mA) 1000 10000 -1 Ou tput C urrent (mA) Efficiency vs Output Current (Vo=1.8V ) Load Regulation (Vo=1.8V) 100 1 90 0 .8 V in=3 .6 V V in=4 .2 V 0 .6 V in=5 V 80 70 0 .4 60 0 .2 50 0 40 -0 .2 30 Vin=3. 6V 20 1 10 100 1000 10000 -0 .4 Vin=4V 10 -0 .6 Vin=5V 0 -0 .8 1 10 100 Out put Current(mA) 1000 10000 -1 Out p ut C urre nt(mA ) Efficiency vs Output Current (Vo=3.3V) Load Regulation (Vo=3.3V) 100 1 90 0 .8 Vi n =3 .6V 80 0 .6 Vi n =4 .2V Vi n =5 V 70 0 .4 60 0 .2 50 0 40 30 Vin=3.6V -0 .2 20 Vin=4.2V -0 .4 10 Vin=5V -0 .6 0 1 10 100 10 0 0 10 0 00 -0 .8 1 10 100 1000 10000 -1 Output Current(mA) Ou tp ut Cu rre n t(m A ) Power Analog Microelectronics, Inc www.poweranalog.com 03/2011 Rev2.1 5 PAM2307 3A Low Noise Step-Down DC-DC Converter Typical Performance Characteristics TA =25 °C , CIN =22*2uF,Co=22 μF unless otherwise noted. Reference Voltage VS Input Voltage Output Voltage VS Load Current 0.602 3.32 0.600 3.31 0.598 3.3 0.596 3.29 0.594 3.28 Vo=3.3V 3.27 0.592 3.26 0.590 0.588 I =100mA I =600mA 0.586 3.25 Vin=3.6V 3.24 Vin=4.2V Vin=5V 3.23 I =800mA 0.584 3.22 2 3 4 5 6 0 500 Input Voltage Reference Voltage VS Temperature 0.620 1000 1500 2000 Load Current(mA) 2500 3000 Dynamic Supply Current VS Temperature 60 Vin=3.6V 0.615 50 0.610 40 0.605 30 0.600 20 0.595 10 Vo=1.2V Vin=3.6V 0.590 ILoad=0A 0 0 50 100 150 40 60 Temperature(℃） 100 120 140 Temperature(℃） Reference Voltage VS Load Current 0.604 80 Rdson VS Input Voltage 0.2 0.6 0.16 0.596 0.12 0.592 0.08 0.588 Vin=2.7V 0.584 0.04 Vin=3.6V PMOS NMOS Vin=4.2V 0.58 0 0 200 400 600 800 2.5 Load Current 3 3.5 4 4.5 Input Voltage(V) 5 5.5 Power Analog Microelectronics, Inc www.poweranalog.com 03/2011 Rev2.1 6 PAM2307 3A Low Noise Step-Down DC-DC Converter Typical Performance Characteristics TA =25 °C , CIN =22*2uF,Co=22 μF unless otherwise noted. Oscillator Frequency VS Temperature Oscillator Frequency VS Input Voltage 1.8 1.58 Vin=3.6V 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(℃） Dynamic Supply Current VS Input Voltage 50 45 40 35 30 25 20 15 Vo=1.2V 10 5 0 Iload=0A 2.5 3.5 4.5 5.5 Input Voltage(V) Power Analog Microelectronics, Inc www.poweranalog.com 03/2011 Rev2.1 7 PAM2307 3A Low Noise Step-Down DC-DC Converter Typical Performance Characteristics TA =25 °C , CIN =22*2uF,Co=22 μF unless otherwise noted. Load Transient Io=0-3A, Vo=1.2V, Vin=5V Load Transient Io=1-3A, Vo=1.2V, Vin=5V Output Current Output Current Voltage Output Voltage Output Load Transient Io=0-1A, Vo=1.2V, Vin=5V Load Transient Io=1-2A, Vo=3.3V, Vin=5V Output Current Output Current Voltage Output Voltage Output Start-up from Shutdown Vo=1.2V, Vin=5V, Io=2A Start-up from Shutdown Vo=1.2V, Vin=5V,Io=3A Enable Enable Voltage Output Voltage Output Power Analog Microelectronics, Inc www.poweranalog.com 03/2011 Rev2.1 8 PAM2307 3A Low Noise Step-Down DC-DC Converter Application Information The basic PAM2307 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 2.7µH. 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 1.2µH 1.5µH 2.2µH 2.2µH 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. 2.2µH 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 PAM2307. 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 03/2011 Rev2.1 9 PAM2307 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 PD =IO 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 QFN3X3 68°C/W and SOP-8(EP) 90°C/W respectively. 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 PAM2307 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). P D=(125°C-25°C)/68°C/W=1.47W(QFN3X3) P D=(125°C-25°C)/90°C/W=1.11W(SOP-8) 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. Setting the Output Voltage The inter nal reference is 0.6V (Typical). The output voltage is calculated as below: The output voltage is given by Table 1. Thermal Shutdown R1 V O=0.6×1+ R2 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. 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 03/2011 Rev2.1 10 PAM2307 3A Low Noise Step-Down DC-DC Converter Ordering Information PAM 2307 X X X xxx X Shipping Package Output Voltage Number of Pins Package Type Pin Configuration Pin Configuration A Type Package Type Num ber of Pins Output Voltage J: QFN 3x3 E: 16 ADJ: Adj E: SOP-8(EP) C: 8 ADJ: Adj 16 pins B Type 8 pins Par t Num ber Output Voltage Package Type S hipping Package PAM2307AJEADJR ADJ QFN3x3-16 3,000 Units/Tape & Reel PAM2307BE CADJR ADJ SOP-8(EP) 2,500 Units/Tape & Reel Power Analog Microelectronics, Inc www.poweranalog.com 03/2011 Rev2.1 11 PAM2307 3A Low Noise Step-Down DC-DC Converter Outline Dimensions 3x3 mm QFN 16 DIMENSIONS (Millieters) MIN TYP MAX A 0.50 0.55 0.60 A1 0.00 0.02 0.05 A2 0.20 b 0.18 0.25 0.30 D 2.90 3.00 3.10 D1 1.55 1.70 1.80 E 2.90 3.00 3.10 E1 1.55 1.70 1.80 e L 0.50BSC 0.30 0.40 0.50 N 16 aaa 0.08 bbb 0.10 Power Analog Microelectronics, Inc www.poweranalog.com 03/2011 Rev2.1 12 PAM2307 3A Low Noise Step-Down DC-DC Converter Outline Dimensions SOP-8(EP) Power Analog Microelectronics, Inc www.poweranalog.com 03/2011 Rev2.1 13