A Product Line of Diodes Incorporated PAM2307 3A LOW NOISE STEP-DOWN DC-DC CONVERTER Description Pin Assignments The PAM2307 is a 3A step-down DC-DC converter. At heavy load, the constant-frequency PWM control performs excellent stability and transient response. No external compensation components are required. The PAM2307 supports a range of input voltages from 2.7V to 5.5V, allowing the use of a single Li+/Li-polymer cell, multiple Alkaline/ NiMH 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 1µA. Other key features include over-temperature and short circuit protection, and under-voltage lockout to prevent deep battery discharge. 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. Features Applications • • Output Current: Up to 3A Output Voltage: 0.6V to VIN • 5V or 3.3V Point of Load Conversion • Input Voltage: 2.7 to 5.5V • Telecom/Networking Equipment • Efficiency up to 95% • Set Top Boxes • 42µA (Typ) No Load Quiescent Current • Storage Equipment • Shutdown Current: <1µA • Video Cards • 100% Duty Cycle Operation • DDR Power Supply • 1.5MHz Switching Frequency • Internal Soft Start • No external Compensation Required • Current Limit Protection • Thermal Shutdown • QFN3x3 16-Pin and SOP-8(EP) Package PAM2307 Document number: DSxxxxx Rev. 2 - 1 1 of 14 www.diodes.com September 2012 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2307 Typical Applications Circuit ⎛ ⎞ V O = 0.6 × ⎜1 + R1 ⎟ ⎜ R2 ⎟⎠ ⎝ Pin Descriptions Pin Name PGND FB GND NC Package Name QFN3x3-16L SOP-8(EP) 1, 2, 3 2 4 3 5 4 6, 16 — EN 7 5 TEST VIN PVIN SW 8 9 10, 11, 12 13, 14, 15 6 7 8 1 Function Main power ground pin. Feedback voltage to internal error amplifier, the threshold voltage is 0.6V. Signal ground for small signal components. No connection. Enable control input. Force this pin voltage above 1.5V, enables the chip, and below 0.3V shuts down the device. Test Mode(no connect or to Ground). Bias supply. Chip main power supply pin. Input supply for power stage. Must be closely decoupled to PGND. The drains of the internal main and synchronous power MOSFET. Functional Block Diagram PAM2307 Document number: DSxxxxx Rev. 2 - 1 2 of 14 www.diodes.com September 2012 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2307 Absolute Maximum Ratings (@TA = +25°C, unless otherwise specified.) 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. Parameter Rating Unit 6 V SW Pin Voltage -0.3 to (PVIN +0.3) V FB Pin Voltage -0.3 to (VIN +0.3) -0.3 to +6.0 150 -65 to +150 300, 5sec V °C °C °C Input Voltage PVIN, VIN EN Pin Voltage Maximum Junction Temperature Storage Temperature Range Soldering Temperature V Recommended Operating Conditions (@TA = +25°C, unless otherwise specified.) Parameter Supply Voltage Junction Temperature Range Ambient Temperature Range Rating 2.5 to 5.5 -40 to +125 -40 to +85 Unit V °C Thermal Information Parameter Symbol Thermal Resistance (Junction to Ambient) θJA Thermal Resistance (Junction to Case) θJC PAM2307 Document number: DSxxxxx Rev. 2 - 1 Package QFN3x3-16 SOP-8(EP) QFN3x3-16 SOP-8(EP) 3 of 14 www.diodes.com Max 35 90 14 11 Unit °C/W September 2012 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2307 Electrical Characteristics (@TA = +25°C, VIN = 3.6V, VO = 1.8V, CIN = 22µF, CO = 22µF, L = 2.2µH, unless otherwise specified.) Parameter Symbol Test Conditions Min Typ Max Units Input Voltage Range VIN 2.5 5.5 V Output Voltage Range VO 0.6 VIN V UVLO Threshold VUVLO Regulated Output Votlage Accuracy VO Regulated Feedback Voltage VFB FB Leakage Current IFB 2.4 VIN Rising Hysteresis VIN Falling 1.8 IO = 0 to 3A, VIN = 2.5 to 5.5V -2 0.588 V 0.600 VO =1V LNR VIN = 2.5V to 5V 0.2 Output Voltage Load Regulation LDR IO = 0A to 3A 0.5 Quiescent Current IQ No Load 42 Shutdown Current ISD VEN = 0V Current Limit ILIM Drain-Source On-State Resisitance High Efficiency Start-Up Time fOSC tS VEH EN Threshold Low VEL EN Leakage Current IEN OTP OTH PAM2307 Document number: DSxxxxx Rev. 2 - 1 V 0.2 µA %/V %/A 90 µA 1 µA 1.8 MHz 95 Ω Ω % 3 ms A 0.140 0.09 η EN Threshold High Over Temperature Protection OTP Hysteresis High Side Low Side RDS(ON) 1.5 From enable to output regulation 1.5 VIN = VEN = 0V V -1.0 150 30 4 of 14 www.diodes.com % 0.612 3.5 1.2 V mV +2 Output Voltage Line Regulation Oscillator Frequency 2.5 240 0.3 V +1.0 µA °C °C September 2012 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2307 Typical Performance Characteristics (@TA = +25°C, CIN = 22*2µF, CO = 22µF, unless otherwise specified.) PAM2307 Document number: DSxxxxx Rev. 2 - 1 5 of 14 www.diodes.com September 2012 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2307 Typical Performance Characteristics (cont.) (@TA = +25°C, CIN = 22*2µF, CO = 22µF, unless otherwise specified.) PAM2307 Document number: DSxxxxx Rev. 2 - 1 6 of 14 www.diodes.com September 2012 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2307 Typical Performance Characteristics (cont.) (@TA = +25°C, CIN = 22*2µF, CO = 22µF, unless otherwise specified.) PAM2307 Document number: DSxxxxx Rev. 2 - 1 7 of 14 www.diodes.com September 2012 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2307 Typical Performance Characteristics (cont.) (@TA = +25°C, CIN = 22*2µF, CO = 22µF, unless otherwise specified.) PAM2307 Document number: DSxxxxx Rev. 2 - 1 8 of 14 www.diodes.com September 2012 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2307 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. 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 VIN or VOUT also increases the ripple current as shown in equation 3A reasonable starting point for setting ripple current is ΔIL = 1.2A (40% of 3A). ΔIL = ⎛ ⎞ ⎜1 − V OUT ⎟ ⎟ VIN ⎠ 1 Equation (1) (f )(L ) VOUT ⎜⎝ 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-resistance inductor. VO L 1.2V 1.5V 1.8V 2.5V 3.3V 1.2µH 1.5µH 2.2µH 2.2µH 2.2µH CIN 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: CIN required IRMS ≅ IOMAX [VOUT (VIN − VOUT )]1/ 2 VIN This formula has a maximum at VIN = 2VOUT, where IRMS =IOUT /2. This simple worst-case condition is commonly 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 manufacturer if there is any question. 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 IRIPPLE (P-P) requirement. The output ripple ΔVOUT is determined by: ΔV OUT ≈ ΔIL (ESR + 1 / 8f COUT ) Where f = operating frequency, COUT = output capacitance and ΔIL = ripple current in the inductor. For a fixed output voltage, the output ripple is highest at maximum input voltage since ΔIL 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. When choosing the input and output ceramic capacitors, choose the X5R or X7R dielectric formul ations. These dielectrics have the best temperature and voltage characteristics of all the ceramics for a given value and size. Thermal Consideration 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. For continuous operation, the junction temperature should be maintained below +125°C. The power dissipation is defined as: PD = IO 2 V O RDS(ON)H + (VIN − V O )RDS( ON)L VIN + (tSW FS IO + IQ ) VIN IQ is the step-down converter quiescent current. The term tsw is used to estimate the full load step-down converter switching losses. PAM2307 Document number: DSxxxxx Rev. 2 - 1 9 of 14 www.diodes.com September 2012 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2307 Application Information (cont.) For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to: PD = IO 2 RDS(ON)H + IQ VIN Since RDS(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 depends on the thermal resistance 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: PD = T J(MAX ) − T A θJA Where TJ(max) is the maximum allowable junction temperature +125°C. TA 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 TA = +25°C can be calculated by following formula: P = (125°C - 25°C) /68°C/W = 1.47W (QFN3X3) P = (125°C - 25°C) /90°C/W = 1.11W (SOP-8) 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. R1 ⎞ ⎛ ⎟ V O = 0 .6 x ⎜ 1 + R 2⎠ ⎝ Table 1: Resistor selection for output voltage setting. VO R1 R2 1.2V 1.5V 1.8V 2.5V 3.3V 100k 150k 200k 380k 540k 100k 100k 100k 120k 120k 100% Duty Cycle Operation As the input voltage approaches the output voltage, the converter turns the P-Channel transistor continuously on. In this mode the output voltage is equal to the input voltage minus the voltage drop across the P-Channel transistor: V OUT = VIN − ILOAD (RDSON + RL ) where RDS(ON) = P-Channel switch ON resistance, ILOAD = Output Current, RL = Inductor 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). 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. PAM2307 Document number: DSxxxxx Rev. 2 - 1 10 of 14 www.diodes.com September 2012 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2307 Ordering Information Part Number PAM2307AJEADJR PAM2307BECADJR Output Voltage ADJ ADJ Part Type QFN3x3-16 SOP-8(EP) Standard Package 3000 Units/Tape & Reel 2500 Units/Tape & Reel Marking Information QFN3x3-16 SOP-8(EP) PAM2307 Document number: DSxxxxx Rev. 2 - 1 11 of 14 www.diodes.com September 2012 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2307 Package Outline Dimensions (All dimensions in mm.) QFN3x3-16 Notes: 1. Controlling dimensions are in millimeters (angle in degrees). 2. Coplanarity applies to the exposed pad as well as the terminals. 3. DAP is 1.90 x 1.90mm. PAM2307 Document number: DSxxxxx Rev. 2 - 1 12 of 14 www.diodes.com September 2012 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2307 Package Outline Dimensions (cont.) (All dimensions in mm.) SOP-8(EP) PAM2307 Document number: DSxxxxx Rev. 2 - 1 13 of 14 www.diodes.com September 2012 © Diodes Incorporated A Product Line of Diodes Incorporated PAM2307 IMPORTANT NOTICE DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION). Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or trademark rights, nor the rights of others. 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