PAM2310 2A 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 1 0 i s a 2 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 2A Output Voltage: 0.6V to V IN Input Voltage: 2.7V to 5.5V Peak 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 SOP-8 Package The PAM2310 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 PAM2310 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 PAM2310 delivers 2A 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 PAM2310 an ideal choice for high output voltage, high current applications which require a low dropout threshold. The PAM2310 is available in SOP-8 package. Typical Application L VO VIN VIN (2) (3)SW CI N R1 PAM2310 22uF Cfw 100p EN(7) Co 22uF (5)FB 0 R2 N C(1,6,8) GND (4) 0 0 0 R1 V O = 0.6 1+ R2 Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 1 PAM2310 2A 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 SOP-8 NC NC VIN EN SW NC GND FB P2310:PAM2310 V: Output Voltage X: Internal Code Y: Year W: Week Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 2 PAM2310 2A Low Noise Step-Down DC-DC Converter Pin Description Name Pin Number Function NC 1 No Connected VIN 2 Bias supply. 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 Enable control input. Force this pin voltage above 1.5V, enables the chip, and below 0.3V shuts down t he 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 SOP-8 90 °C/W Thermal Resistance (Junction to Case) θJC SOP-8 11 °C/W Internal Power Diss ipation (@TA=25°C) PD SOP-8 1100 mW Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 3 PAM2310 2A Low Noise Step-Down DC-DC Converter Electrical Characteristic TA =25 °C , Vin=5.0V, Vo=1.8V, Cin=22uF,Co=22uF, L=2.2uH, unless otherwise noted. PARAMETER SYM BOL Test Co nditions MIN TYP M AX UNITS Input Voltage Range VIN 2.7 5.5 V Output Voltage Range VO 0.6 VIN V Regulated Output Voltage Accuary VO -2 +2 % Regulated Feedback Voltage VF B 0.612 V FB Leak age Current IFB 0.2 µA I O = 0 to 2A,VIN =2.7V to 5.5V 0.588 0.6 VO=1V Output Voltage Line Regulation LNR VIN = 2.7V t o 5V 0.2 %/V Output Voltage Load Regulation LDR I O=0A to 2A 0.5 %/A 42 Quies cent Current IQ No load Shutdown C urrent ISD VE N = 0V Peak Inductor Current I LIM Oscillator Frequency f OS C Drain-Source On-State Res istance Start up Time RDS( ON) tS EN Threshold High VE H EN Threshold Low VE L EN Leakage Current IEN 90 µA 1 µA 3 Isw=100mA A 1.5 MH z High Side 90 mΩ Low Side 70 mΩ 0.5 ms From enable to output regulation 1.5 VIN =VEN = 0V V -1.0 0.3 V 1.0 µA Over T emperature Protection OTP 150 °C OTP Hysteresis OT H 30 °C Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 4 PAM2310 2A Low Noise Step-Down DC-DC Converter Typical Performance Characteristics TA =25 °C , CIN =22uF,Co=22 μF, 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 Io=100mA 70 Io=1000mA Vin=3.6V Vin=5.0V Vin=5.5V 50 65 Io=2000mA 40 1 10 100 1000 10000 60 2.0 3.0 4.0 5.0 6.0 Input Voltage(V) Output Current(mA) Efficiency vs Output Current (Vo=1.8V ) Efficiency vs Input Voltage (Vo=1.8V) 100 1 00 90 95 90 80 85 70 80 Io= 100mA 60 Vin=3.6V 75 . Io= 1000mA Vin=5.0V 50 70 Vin=5.5V Io= 2000mA 40 1 10 100 1000 10000 65 2.0 3.0 4.0 5.0 6.0 Input Voltage(V) Output Current(mA) Efficiency vs Output Current(Vo=3.3V) Efficiency vs Input Voltage (Vo=3.3V) 100 100 95 95 90 90 85 85 80 Io=100mA 80 75 Vin=4.5V 70 Vin=5.0V 65 Vin=5.5V 60 1 10 100 1000 10000 O utput C u rrent(mA) 75 Io=1000mA 70 Io=2000mA 65 4.0 4.5 5.0 5.5 6.0 Input Voltage(V ) Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 5 PAM2310 2A Low Noise Step-Down DC-DC Converter Typical Performance Characteristics TA =25 °C , CIN =22uF,Co=22 μF, unless otherwise noted. Reference Voltage VS Input Voltage Output Voltage VS Load Current 0.602 1.210 0.600 1.205 Vin=3.6V 0.598 1.200 Vin=5.0V 0.596 Vin=5.5V 1.195 0.594 1.190 0.592 1.185 0.590 0.588 1.180 I =100mA I =600mA 0.586 1.175 I =800mA 0.584 1.170 2 3 4 5 0 6 500 1500 2000 Output Current(mA) Input Voltage Reference Voltage VS Temperature 0.620 1000 Dynamic Supply Current VS Temperature 60 Vin=4.5V 0.615 50 0.610 40 0.605 30 0.600 20 0.595 10 Vo=1.2V Vin=4.5V 0.590 ILoad=0A 0 0 50 100 150 40 60 80 Temperature(℃） 120 140 Temperature(℃） Reference Voltage VS Load Current 0.604 100 Rdson VS Input Voltage 120 0.6 100 0.596 80 0.592 60 0.588 40 Vin=2.7V 0.584 P-MOS 20 Vin=3.6V Vin=4.2V 0 0.58 0 200 400 600 2 800 3 4 5 6 Input Voltage(V) Load Current Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 6 PAM2310 2A Low Noise Step-Down DC-DC Converter Typical Performance Characteristics TA =25 °C , CIN =22uF,Co=22 μF, unless otherwise noted. Oscillator Frequency VS Temperature Oscillator Frequency VS Input Voltage 1.8 1.58 Vin=4.5V 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=0-2A, Vo=1.2V, Vin=5V Load Transient Io=0-2A, Vo=3.3V, Vin=5V Output Current Output Current Voltage Output Voltage Output Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 7 PAM2310 2A Low Noise Step-Down DC-DC Converter Application Information The basic PAM2310 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 2A reasonable starting point for setting ripple current is △I L = 1.2A (40% of 2A). 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 (2A + 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 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. 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 PAM2310. 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 PAM2310 2A 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 QFN3X3 68°C/W and SOP-8 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 PAM2310 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 (3000mA). 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 3000mA. 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 typically 500mA. 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 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 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 PAM2310 2A Low Noise Step-Down DC-DC Converter Ordering Information PAM 2310 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: SOP-8 C: 8 Output Voltage ADJ: Adj 8 pins Part Number Output Voltage Package Type Shipping Package PAM2310BECADJR ADJ SOP-8 2,500 Units/Tape & Reel Power Analog Microelectronics, Inc www.poweranalog.com 05/2011 Rev1.0 10 PAM2310 2A Low Noise Step-Down DC-DC Converter Outline Dimensions SOP-8 REF DIMENSIONS Millimeters Min Max A 5.80 6.20 B 4.80 5.00 C 3.80 4.00 D 0º 8º E 0.40 0.90 F 0.19 0.25 M 0.10 0.25 H 0.35 0.49 L 1.35 1.75 B G J 0.375 REF K 45º G 1.27 TYP J K D H E Power Analog Microelectronics, Inc www.poweranalog.com 04/2011 Rev1.0 11