PAM2321 3MHz,Fast Transient 2A Step-Down Converter Features n n n n n n n n n n n n n n General Description The PAM2321 is a 2A step-down converter with a typical input voltage of 3.3V and a fixed output voltage of 1.2V or an adjustable output. The 3MHz switching frequency enables the use of small external components. The ultra-small 3mm x 3mm footprint and high efficiency make the PAM2321 an ideal choice for portable applications. The PAM2321 delivers 2 A maximum output current while consuming only 55uA no - load quiescent current. Low R DS(ON) integrated MOSFETs and 100 % duty cycle operation make the PAM2321 the ideal choice for high output voltage, high current applications which require a low dropout threshold . The PAM 23 21 p r ov id es ex c el le nt tr an s ie nt r es p o n s e a n d o u tp ut a c c ur a c y a c r o s s th e operating range. T h e PA M 2 3 2 1 m a i n t a i n s h i g h e f f i c i e n c y th r ou g h o u t th e l o a d r a n g e . Th e PA M 2 3 2 1 automatically optimizes efficiency during light l oa d m o de ( P S M) an d m a i nt a i n s c o n s ta n t frequency and low output ripple during PWM mode. Over-temperature and short circuit protection safeguard the PAM2321 and system components from damage. The PAM2321 are available in Pb-free, ultrasmall, low profile, TDFN3X3-10 packages. The product is rated over a temperature range of 40°C to 85°C. 2A Maximum Output Current Tiny 0.47uH Chip Inductor Excellent Transient Response Input Voltage: 2.7V to 5.5V Fixed or Adjustable Output Voltage Options: - Fixed Output Voltage: 1.2V - Adjustable Output Voltage: 1.0V to Vin High Efficiency with 3MHz Switching Frequency 55uA No Load Quiescent Current 100% Duty Cycle Low-Dropout Operation Internal Soft Start Over-Temperature and Current Limit Protection < 1uA Shutdown Current -40°C to 85°C Temperature Range Pb-Free/Halogen Free Package RoHS/REACH Compliant Applications n n n n n n n n Cellular Phone Digital Cameras Hard Disk Drives MP3 Players PDAs and Handheld Computers Portable Media Players USB Devices Wireless Network Cards Typical Application L1 Vin C1 10µF C3 1.0µF PVIN SW EN SW VIN FB AGND PGND Vout 0.47uH R1 Cfw 100pF C2 10µF R2 Vout=0.6* (1+R1/R2) Power Analog Microelectronics , Inc www.poweranalog.com 01/2013 Rev1.2 1 PAM2321 3MHz,Fast Transient 2A Step-Down Converter Block Diagram VIN 3.0M OSC SLOPE COMP FREQ SHIFT OSC + IAMP - PVIN FB MAIN SWITCH ( PCH ) S Q R1 R Q RS LATCH R2 VIN + EA SWITCHING LOGIC AND BLANKING CIRCUIT ANTI SHOOTTHRU SW COMP EN 0.6VREF + IRCMP - SHUTDOWN SYNCHRONOUS RECTIFIER ( NCH ) PGND GND Pin Configuration & Marking Information Top View TDFN3X3-10L EN 1 10 PGND PVIN 2 9 VIN 3 8 PGND SW AGND 4 7 FB 5 6 SW AGND A/B: Pin Configuration X: Internal Code Y: Year W: Week (Exposed Pad) Power Analog Microelectronics , Inc www.poweranalog.com 01/2013 Rev1.2 2 PAM2321 3MHz,Fast Transient 2A Step-Down Converter Pin Description Name Function PGND Main power ground return pin. Connect to the output and input capacitor return. PVIN Input power supply tied to the source of the high side P-channel MOSFET. VIN Power supply; supplies power for the internal circuitry. Feedback input pin. This pin is connected directly to the converter output for the 1.2V fixed FB output version, or connected to an external resistor divider for the adjustable output version. AGND EN SW EP Analog ground. This pin is internally connected to the analog ground of the control circuitr y. Enable pin. A logic low disables the converter and it consumes less than 1µA of current. When connected high, it resumes normal operation. Switching node. Connect the inductor to this pin. It is internally connected to the drain of both high and low side MOSFETs. Exposed pad of the package provides both electrical contact to the ground and good thermal contact to the PCB. This pad must be soldered to the PCB for proper operation. 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 EN, FB Pin Voltage.............................- 0.3V to V IN SW Pi n Voltage.....................- 0.3V to ( V IN +0.3V ) 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 Operation Temperature Range.........-40 °C to 85 °C Junction Temperature Range........-40 °C to 125 °C Thermal Information Parameter Thermal Resistance (Junction to Case) Thermal Resistance (Junction to Ambient) Internal Power Dissipation Symbol Package Maximum θJC TDFN3X3-10 8.5 Unit °C/W θJA TDFN3X3-10 60 PD TDFN3X3-10 1.66 W Power Analog Microelectronics , Inc www.poweranalog.com 01/2013 Rev1.2 3 PAM2321 3MHz,Fast Transient 2A Step-Down Converter Electrical Characteristic T A =25 °C , V IN=3.3V, Vout=1.2V,C IN=10µF, C O =10µF, L=0.47µH, unless otherwise noted. PARAMETER Input Voltage Range UVLO Threshold SYMBOL Test Conditions MIN TYP MAX UNITS 2.7 3.3 5.5 V VIN Rising 2.6 2.7 V Hysteresis 250 VIN VUVLO VIN Falling 2 Output Voltage Range Vout Output Voltage Accuary Vout Io=100mA Regulated Feedback Voltage V FB No Load PMOS Current Limit ILIM Output Voltage Line Regulation LNR VIN = 3.3V to 4V Output Voltage Load Regulation LDR 1 1.2 -3.0 0.588 0.60 Vin V +3.0 % 0.612 V A 0.3 %/V IO=1mA to 2A 1 %/A 55 IQ No load Shutdown Current ISD VEN = 0V Oscillator Frequency fOSC RDS(O N) V 3.0 Quiescent Current Drain-Source On-State Resistance mV IDS=100mA 90 µA 1 µA 3 MHz P MOSFET 130 mΩ N MOSFET 90 mΩ SW Leakage Current ILSW 1 Start-up Time Ts PSM Threshold ITH EN Threshold High VEH EN Threshold Low VEL EN Leakage Current IEN ±0.01 µA Over Temperature Protection OTP 150 °C OTP Hysteresis OTH 30 °C Vin=3.3V,Vo=1.2V µA 200 us 200 mA 1.4 V 0.4 V Power Analog Microelectronics , Inc www.poweranalog.com 01/2013 Rev1.2 4 PAM2321 3MHz,Fast Transient 2A Step-Down Converter Typical Performance Characteristics T A =25 °C , C IN=10 µ F, C O =10 µ F,L=0.47µH, unless otherwise noted. Efficiency vs Output Current Efficiency vs Output Current 100 100 90 90 80 80 70 70 60 60 50 50 Vo=1.2V L=0.47uH 40 Vo=1.5V L=0.47uH 40 30 30 20 Vin=3.3V Vin=4.2V Vin=5V 10 Vin=3.3V 20 Vin=4.2V 10 0 Vin=5V 0 1 10 100 Output Current (mA) 1000 1 10000 Efficiency vs Output Current 10 100 Output Current (mA) 1000 10000 Efficiency vs Input Voltage 100 100 90 90 80 80 70 70 60 60 50 50 Vo=1.8V L=0.47uH 40 40 30 Vo=2.5V L=1uH 30 Vin=3.3V Vin=4.2V Vin=5V 20 10 Vin=3.3V 20 Vin=4.2V 10 0 Vin=5V 0 1 10 100 1000 10000 1 10 Output Current (mA) 100 Output Current (mA) 1000 10000 Load Regulation Efficiency vs Output Current 100 2.00 90 1.50 80 Vo=1.2V L=0.47uH 1.00 70 0.50 60 0.00 50 Vo=3.3V L=1uH 40 -0.50 30 -1.00 Vin=4.2V Vin=5V Vin=5.5V 20 10 Vin=3.3V Vin=4.2V Vin=5.0V -1.50 -2.00 0 1 10 100 Output Current (mA) 1000 0 10000 500 1000 1500 2000 Output Current(mA) Power Analog Microelectronics , Inc www.poweranalog.com 01/2013 Rev1.2 5 PAM2321 3MHz,Fast Transient 2A Step-Down Converter Typical Performance Characteristics T A =25 °C , C IN=10 µ F, C O =10 µ F, L=0.47µH,unless otherwise noted. Line Regulation Quiescent Current vs Input Voltage 0.5 66 Vo=1.2V L=0.47uH 0.4 61 0.3 0.2 56 0.1 0.0 51 -0.1 46 -0.2 Io=100mA Io=1000mA Io=2000mA -0.3 -0.4 41 -0.5 36 2.7 3.1 3.5 3.9 4.3 Input Voltage(V) 4.7 5.1 5.5 2 Rdson vs Input Voltage(Vo=1.2V) 3 4 Input Votage(V) 5 6 Start-up Io=2A, Vo=1.2V, Vin=3.3V 160 140 120 100 80 60 40 PMOS 20 NMOS 0 2.5 3 3.5 4 4.5 Input Voltage(V) 5 5.5 Load Transient Io=0~2A, Vo=3.3V, Vin=5V Load Transient Io=0~2A, Vo=1.2V, Vin=3.3V Power Analog Microelectronics , Inc www.poweranalog.com 01/2013 Rev1.2 6 PAM2321 3MHz,Fast Transient 2A Step-Down Converter Application Information The basic PAM2321 application circuit is shown in Page 1. External component selection is determined by the load requirement, selecting L first and then Cin and Cout. output ripple △Vout is determined by: Inductor Selection 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. 1 ö æ V VOUT @VIL ç ESR+ ÷ 8fCOUT ø è 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 2.0 A reasonable starting point for setting ripple current is △I L = 800mA (40% of 2A). DIL = æ VOUT ö VOUT ç 1÷ VIN ø (f )(L ) è 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. (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 2.8A rated inductor should be enough for most applications (2A + 800mA). 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 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 PAM2321. 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. é VOUT (VIN - VOUT )ùû CIN required IRMS @ IOMAX ë VIN 1 2 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 er e I RMS= I OUT/ 2. T hi s s im pl e w or s t - c as 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. The selection of Cout is driven by the required effective series resistance (ESR). PD =IO 2 VORDSONH + (VIN -VO )RDSONL VIN + (t SW FSIO +IQ )VIN I Q is the step-down converter quiescent current. The term tsw is used to estimate the full load step-down converter switching losses. For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dis sipation reduces to: Typically, once the ESR requirement for Cout has been met, the RMS current rating generally far exceeds the I RIPPLE (P-P) requirement. The PD =IO 2RDSONH +IQ VIN Power Analog Microelectronics , Inc www.poweranalog.com 01/2013 Rev1.2 7 PAM2321 3MHz,Fast Transient 2A Step-Down Converter 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 amplifier.When the feedback voltage gets higher than internal reference voltage, the device will enter into low I Q idle state with most of internal blocks disabled. The output voltage will be reduced by loading or leakage current. When the feedback voltage gets lower than the internal reference voltage, the convertor will start a working state again. 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: 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 Where TJ(max) is the maximum allowable junction temperature 125°C.T A is the ambient temperature and θ JA 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 θ JA of TDFN3X3 package is 60°C/W and DFN3X3 is 68.5°C/W, respectively. The maximum power dissipation at T A = 25°C can be calculated by following formula: UVLO and Soft-Start P D=(125°C-25°C)/60°C/W=1.66W P D =(125°C-25°C)/68.5°C/W=1.46W The reference and the circuit remain reset until the VIN crosses its UVLO threshold. The PAM2321 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. 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. æ R1 ö VO=0.6×1+ ç R2 ÷ è ø Short Circuit Protection 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 When the converter output is shorted or the device is overloaded,each high-side MOSFET current-limit event (3A typ) turns off the high-side MOSFET and turns on the low-side MOSFET. A internal counter is used to count the each current-limit event. The counter is reset after consecutive high-side MOSFETs turn on without re ac h in g c ur r e nt l i mi t. I f the c ur r en t- l im it condition persists, the counter fills up. The control logic then stops both high-side and lowside MOSFETs and waits for a hiccup period, before attemping a new soft-start sequence. The counter bits is decided by Vfb voltage. If Vfb≤ 0 . 2, the counter is 3-bit counter; if Vfb>0.2 the counter is 6-bit counter. The typical hicuup made duty cycle is 1.7%. The hicuup mode is disable during soft-start time. Pulse Skipping Mode (PSM) Description When load current decreases, the peak switch current in Power-PMOS will be lower than skip current threshold and the device will enter into Pulse Skipping Mode. 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. In this mode, the device has two states, working state and idle state. First, the device enters into wo rk i ng s ta te c on tr ol l ed b y i nte r nal er r or Power Analog Microelectronics , Inc www.poweranalog.com 01/2013 Rev1.2 8 PAM2321 3MHz,Fast Transient 2A Step-Down Converter PCB Layout Check List When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the PAM2321. Check the following in your layout: 1. The input capacitor should be close to IC as close as possible. 2. Must put a small decoupling capacitor between Vin Pin and AGND Pin. 3. Minimize the switching loop area to avoid excessive switching noise. 4. AGND and PGND should connect at input capacitor GND. 5. For the good thermal dissipation, PAM2321 has a heat dissipate pad in the bottom side, it should be soldered to PCB surface. For the copper area can't be large in the component side, so we can use multiple vias connect to other side of the PCB. Power Analog Microelectronics , Inc www.poweranalog.com 01/2013 Rev1.2 9 PAM2321 3MHz,Fast Transient 2A Step-Down Converter Ordering Information PAM 2321 X X X xxx Output Voltage Number of Pins Package Type Pin Configuration Pin Configuration A Type Part Number PAM2321AYMADJ Package Type Number of Pins Y: TDFN3X3-10 M: 10 Marking P2321A XXXYW Output Voltage ADJ: Adjustable(0.6V) Package Type Standard Package TDFN3X3-10 3,000 Units/Tape & Reel Power Analog Microelectronics , Inc www.poweranalog.com 01/2013 Rev1.2 10 PAM2321 3MHz,Fast Transient 2A Step-Down Converter Outline Dimensions TDFN3X3-10 Power Analog Microelectronics , Inc www.poweranalog.com 01/2013 Rev1.2 11