DS8048-01 RICHTEK | Alldatasheet
Document overview
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Technical content
Features
zzzzz 2.5V to 5.5V Input Range zzzzz 3MHz Fix-Frequency PWM Operation zzzzz 1A Output Current zzzzz 90% Efficiency zzzzz No Schottky Diode Required zzzzz 0.6V Reference Allows Low Output Voltage zzzzz Low Dropout Operation : 100% Duty Cycle zzzzz RoHS Compliant and Halogen Free
Applications
z Microprocessors and DSP Core supplies z Cellular Phones z Wireless and DSL Modems z PC Cards Marking Information Note : Richtek products are : \ RoHS compliant and compatible with the current require- ments of IPC/JEDEC J-STD-020. \ Suitable for use in SnPb or Pb-free soldering processes. HB : Product Code W : Date Code NC EN FB/VOUT GND LXVIN GND RT8048( Package Type QW : WDFN-6L 2x2 (W-Type) Lead Plating System Z : ECO (Ecological Element with Halogen Free and Pb free) - ) Output Voltage Default : Adjustable 10 : 1.0V 12 : 1.2V 15 : 1.5V 18 : 1.8V 25 : 2.5V 33 : 3.3V HBW
DS8048-01 June 2011 www.richtek.com Function Block Diagram COMP RC RS1 RS2 EN VIN LX FB/VOUT UVLO & Power Good Detector VREF Slope Compensation Current Sense OSC & Shutdown Control Current Limit Detector DriverControl Logic PWM Comparator Error Amplifier GND
DS8048-01 June 2011www.richtek.com Absolute Maximum Ratings (Note 1) z Power Dissipation, PD @ TA = 25°C z Package Thermal Resistance (Note 2) z ESD Susceptibility (Note 3) Recommended Operating Conditions (Note 4)
Electrical Characteristics
Parameter Symbol Test Conditions Min Typ Max Unit Quiescent Current IQ -- 81 -- μA Reference Voltage VREF 0.588 0.6 0.612 V VIN Rising -- 2.3 -- Under Voltage Lockout Threshold V UVLO VIN Falling -- 2.1 -- V Shutdown Current ISHDN -- 0.1 1 μA Switching Frequency f OSC -- 3 -- MHz Logic-High V IH 1.5 -- V IN EN Input Threshold Voltage Logic-Low V IL -- -- 0.4 V Thermal Shutdown Temperature T SD -- 140 -- °C Switch On Resistance, High R PFET I LX = 0.2A -- 250 -- m Ω Switch On Resistance, Low R NFET I LX = 0.2A -- 260 -- m Ω Peak Current Limit ILIM -- 1.5 -- A Output Voltage Line Regulation V IN = 2.5V to 5.5V -- -- 1 %/V Output Voltage Load Regulation 0mA < I LOAD < 0.6A -- -- 1 % (VIN = 3.6V, TA = 25°C unless otherwise specified)
DS8048-01 June 2011 www.richtek.com Note 1. Stresses listed as the above “Absolute Maximum Ratings” may cause permanent damage to the device. These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability. Note 2. θ JA is measured in natural convection at TA = 25°C on a high effective thermal conductivity four-layer test board of JEDEC 51-7 thermal measurement standard. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions.
DS8048-01 June 2011www.richtek.com Efficiency vs. Output Current 100 Output Current (A) Efficiency (%) Typical Operating Characteristics VOUT = 1.2V, L = 1μH VIN = 3.3V VIN = 5V Efficiency vs. Output Current 100 Output Current (A) Efficiency (%) VIN = 5V, VOUT = 3.3V, L = 1μH Reference Voltage vs. Temperature 0.580 0.585 0.590 0.595 0.600 0.605 0.610 0.615 0.620 -50 -25 0 25 50 75 100 125 Temperature (°C) Reference Voltage (V) Frequency vs. Temperature 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 -50 -25 0 25 50 75 100 125 Temperature (°C) Frequency (MHz) 1 VIN = 5V, VOUT = 3.3V, IOUT = 0.3A Current Limit vs. Input Voltage 0.5 0.8 1.1 1.4 1.7 2.0 2.3 2.6 Input Voltage (V) Current Limit (A) VOUT = 1.2V Current Limit vs. Temperature 1.1 1.3 1.5 1.7 1.9 2.1 -50 -25 0 25 50 75 100 125 Temperature (°C) Current Limit (A) VIN = 5V VOUT = 1.2 VOUT = 3.3
DS8048-01 June 2011 www.richtek.com Switching Time (250ns/Div) VIN = 5V, VOUT = 1.2V, IOUT = 1A VOUT (10mV/Div) IL (2A/Div) VLX (5V/Div) Switching Time (250ns/Div) VOUT (10mV/Div) IL (2A/Div) VLX (5V/Div) VIN = 5V, VOUT = 3.3V, IOUT = 1A UVLO vs. Temperature 1.5 1.8 2.1 2.4 2.7 3.0 -50 -25 0 25 50 75 100 125 Temperature (°C) UVLO (V) Rising Falling EN Threshold Voltage vs. Temperature 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 -50 -25 0 25 50 75 100 125 Temperature (°C) EN Threshold Voltage (V ) Rising Falling Output Voltage vs. Output Current 1.18 1.19 1.20 1.21 1.22 1.23 1.24 Output Current (A) Output Voltage (V) VIN = 5V VIN = 3.3V VOUT = 1.2V Output Voltage vs. Output Current 3.32 3.33 3.34 3.35 3.36 3.37 3.38 3.39 3.40 3.41 3.42 Output Current (A) Output Voltage (V) VIN = 5V, VOUT = 3.3V
DS8048-01 June 2011www.richtek.com Power Off from EN Time (10 μs/Div) VIN = 5V, VOUT = 3.3V, IOUT = 1A IOUT (2A/Div) VOUT (5V/Div) VEN (10V/Div) Power On from EN Time (100 μs/Div) IOUT (2A/Div) VOUT (5V/Div) VEN (10V/Div) VIN = 5V, VOUT = 3.3V, IOUT = 1A Load Transient Response Time (250 μs/Div) VOUT (50mV/Div) IOUT (0.5A/Div) VIN = 5V, VOUT = 3.3V, IOUT = 50mA to 1A Load Transient Response Time (250 μs/Div) VOUT (50mV/Div) IOUT (0.5A/Div) VIN = 3.3V, VOUT = 1.2V, IOUT = 50mA to 1A
DS8048-01 June 2011 www.richtek.com
Application Information
The basic RT8048 application circuit is shown in Typical Application Circuit. External component selection is determined by the maximum load current and begins with the selection of the inductor value and operating frequency followed by C IN and COUT. Although frequency as high as 3MHz are possible, the minimum on-time of the RT8048 imposes a minimum limit on the operating duty cycle. The minimum duty is equal to 70ns’ f OSC(Hz)’ 100%. Inductor Selection For a given input and output voltage, the inductor value and operating frequency determine the ripple current. The ripple current ΔI L increases with higher VIN and decreases with higher inductance : Having a lower ripple current reduces the ESR losses in the output capacitors and the output voltage ripple. Highest efficiency operation is achieved at low frequency with small ripple current. This, however, requires a large inductor. A reasonable starting point for selecting the ripple current is ΔI L = 0.4 (IMAX). The largest ripple current occurs at the highest VIN. To guarantee that the ripple current stays below a specified maximum, the inductor value should be chosen according to the following equation : OUT OUT OSC L(MAX) IN(MAX) VVL = 1fI V ⎡⎤ ⎡ ⎤ Inductor Core Selection Once the value for L is known, the type of inductor can be selected. High efficiency converters generally cannot afford the core loss found in low cost powdered iron cores, forcing the use of more expensive ferrite or molypermalloy cores. Actual core loss is independent of core size for a fixed inductor value, but it is very dependent on the inductance selected. As the inductance increases, core losses decrease. Unfortunately, increased inductance requires more turns of wire and, therefore, more copper losses. Ferrite designs have very low core losses and are preferred at high switching frequencies. Hence, design goals should concentrate on copper loss and saturation prevention. Ferrite core material saturates “ hard” , which means that the inductance collapses abruptly when the peak design current is exceeded. This result in an abrupt increase in inductor ripple current and consequent output voltage ripple. Do not allow the core to saturate! Different core materials and shapes will change the size, current and price/current relationship of an inductor. Toroid or shielded pot cores in ferrite or permalloy materials are small and don’t radiate energy, but generally cost more than powdered iron core inductors with similar characteristics. The choice of inductor type to use mainly depends on the price vs. size requirements and any radiated field/EMI requirements. CIN and COUT Selection The input capacitance, C IN, is needed to filter the trapezoidal current at the source of the top MOSFET . To prevent large ripple voltage, a low ESR input capacitor sized for the maximum RMS current should be used. RMS current is given by : OUT OUT L OSC IN VVI = 1 fL V =− OUT IN RMS OUT(MAX) IN OUT V VII 1 VV 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 ripple current ratings from capacitor manufacturers are often based on only 2000 hours of life, which makes it advisable to either further derate the capacitor or choose a capacitor rated at a higher temperature than required. Several capacitors may also be placed in parallel to meet size or height requirements in the design. The selection of C OUT is determined by the effective series resistance (ESR) that is required to minimize voltage ripple and load step transients, as well as the amount of bulk capacitance that is necessary to ensure that the control loop is stable. Loop stability can be examined by viewing the load transient response as described in a later section. The output ripple, ΔV OUT, is determined by : OUT L OSC OUT 1V I ESR 8f C The output ripple is highest at maximum input voltage since ΔIL increases with input voltage. Multiple capacitors placed in parallel may be needed to meet the ESR and RMS current handling requirements. Dry tantalum, special
W on a standard JEDEC 51-7 four-layer thermal test board. Figure 3. Derating Curve for the RT8048 Packages high voltage coefficient and audible piezoelectric effects. can also lead to significant ringing. by the regulator to return VOUT to its steady-state value.
DS8048-01 June 2011 www.richtek.com Richtek Technology Corporation Headquarter 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. No third party intellectual property infringemen t of the applications should be guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed b y Richtek. Richtek Technology Corporation Taipei Office (Marketing) 5F, No. 95, Minchiuan Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)86672399 Fax: (8862)86672377 Email: marketing@richtek.com Outline Dimension W-Type 6L DFN 2x2 Package Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0.700 0.800 0.028 0.031 A1 0.000 0.050 0.000 0.002 A3 0.175 0.250 0.007 0.010 b 0.200 0.350 0.008 0.014 D 1.950 2.050 0.077 0.081 D2 1.000 1.450 0.039 0.057 E 1.950 2.050 0.077 0.081 E2 0.500 0.850 0.020 0.033 e 0.650 0.026 L 0.300 0.400 0.012 0.016 D E A e b L SEE DETAIL A 1 122 Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. DETAIL A Pin #1 ID and Tie Bar Mark Options