RT8010B RICHTEK | Alldatasheet
Document overview
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Technical content
Features
zzzzz +2.5V to +4V Input Range zzzzz Output Voltage (Adjustable Output From 0.6V to VIN) zzzzz 800mA Output Current zzzzz 95% Efficiency zzzzz No Schottky Diode Required zzzzz 1.5MHz Fixed-Frequency PWM Operation zzzzz Small 8-Lead WDFN Package zzzzz RoHS Compliant and 100% Lead (Pb)-Free
Applications
z Personal Information Appliances z Wireless and DSL Modems z MP3 Players z Portable Instruments 1.5MHz, 800mA, High Efficiency PWM Step-Down DC/DC Converter General Description The RT8010B is a high-efficiency Pulse-Width-Modulated (PWM) step-down DC-DC converter. Capable of delivering 800mA output current over a wide input voltage range from 2.5V to 4V, the RT8010B is ideally suited for portable electronic devices that are powered from 1-cell Li-ion battery or from other power sources such as cellular phones, PDAs and hand-held devices. Two operating modes are available including PWM/Low- Dropout autoswitch and shut-down modes. The internal synchronous rectifier with low R DS(ON) dramatically reduces conduction loss at PWM mode. No external Schottky diode is required in practical application. The RT8010B enters Low-Dropout mode when normal PWM can not provide regulated output voltage by continuously turning on the upper PMOS. The RT8010B enters shut-down mode and consumes less than 0.1μA when EN pin is pulled low. The switching ripple is easily smoothed-out by small package filtering elements due to a fixed operating frequency of 1.5MHz. This along with small WDFN-8L 2x2 package provides small PCB area application. Other features include soft start, lower internal reference voltage with 2% accuracy, over temperature protection, and over current protection. Marking Information For marking information, contact our sales representative directly or through a Richtek distributor located in your area, otherwise visit our website for detail.
Ordering Information
Note : Richtek Green 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. \`100% matte tin (Sn) plating. RT8010B Package Type QW : WDFN-8L 2x2 (W-Type) Operating Temperature Range G : Green (Halogen Free with Commer- cial Standard) Pin Configurations (TOP VIEW) WDFN-8L 2x2 EN FB PGND PGND PGNDVIN LX AGND
DS8010B-00 July 2007www.richtek.com Preliminary Function Block Diagram Functional Pin Description Pin No. Pin Name Pin Function 1 EN Chip Enable (Active High). 2 FB Feedback Pin. 3 VIN Power Input. 4 LX Pin for Switching. 5 AGND Analog Ground. 6, 7, 8 PGND Power Ground. Exposed Pad (9) NC No Internal Connection. Typical Application Circuit ⎞⎜⎝ ⎛ += R2 R11 x VV REFOUT with R2 = 75k Ω to 200kΩ, and (R1 x C1) should be in the range between 3x10 -6 and 6x10-6 for component selection. 4.7uF 10uF VIN LX RT8010B EN FB 2.2uH 2.5V to 4V VIN VOUT CIN L
1 COUT
PGND 5AGND6, 7, 8 COMP RC RS1 RS2 EN VIN LX FB UVLO & Power Good Detector VREF Slope Compensation Current Sense OSC & Shutdown Control Current Limit Detector DriverControl LogicPWM ComparatorError Amplifier PGND AGND
DS8010B-00 July 2007 www.richtek.com Preliminary Absolute Maximum Ratings (Note 1) z Power Dissipation, PD @ TA = 25°C z Package Thermal Resistance (Note 4) z ESD Susceptibility (Note 2)
Electrical Characteristics
Parameter Symbol Test Conditions Min Typ Max Units Input Voltage Range VIN 2.5 -- 4 V Quiescent Current IQ I OUT = 0mA, VFB = VREF + 5% -- 50 70 μA Shutdown Current ISHDN EN = GND -- 0.1 1 μA Reference Voltage VREF For Adjustable Output Voltage 0.588 0.6 0.612 V Adjustable Output Range VOUT (Note 6) VREF -- VIN − 0.2V V Output Voltage Accuracy Adjustable ΔVOUT VIN = VOUT + ΔV to 4V (Note 5) FB Input Current IFB V FB = VIN −50 -- 50 nA P-MOSFET RON R DS(ON)_P IOUT = 200mA N-MOSFET RON R DS(ON)_N IOUT = 200mA P-Channel Current Limit ILIM_P VIN = 2.5V to 4V 1.2 1.5 -- A EN High-Level Input Voltage VEN_H V IN = 2.5V to 4V 1.5 -- -- V EN Low-Level Input Voltage VEN_L V IN = 2.5V to 4V -- -- 0.4 V Under Voltage Lock Out Threshold UVLO -- 1.8 -- V Hysteresis -- 0.1 -- V To be continued Recommended Operating Conditions (Note 3)
DS8010B-00 July 2007www.richtek.com Preliminary Parameter Symbol Test Conditions Min Typ Max Units Oscillator Frequency fOSC V IN = 3.6V, IOUT = 100mA 1.2 1.5 1.8 MHz Thermal Shutdown Temperature TSD -- 160 -- °C Max. Duty Cycle 100 -- -- % LX Leakage Current VIN = 3.6V, VLX = 0V or VLX = 3.6V −1 -- 1 μA 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. Devices are ESD sensitive. Handling precaution recommended. Note 3. The device is not guaranteed to function outside its operating conditions. Note 4. θ JA is measured in the natural convection at T A = 25°C on a high effective four layers thermal conductivity test board of JEDEC 51-7 thermal measurement standard. The case point of θJC is on the expose pad for the QFN package. Note 5. ΔV = IOUT x PRDS(ON) Note 6. Guarantee by design.
DS8010B-00 July 2007 www.richtek.com Preliminary Typical Operating Characteristics Efficiency vs. Output Current 100 Output Current (A) Efficiency (%) VOUT = 1.2V, COUT = 4.7μF, L = 4.7μH VIN = 2.5V VIN = 3.3V EN Pin Threshold vs. Temperature 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature EN Pin Threshold (V) (°C) VIN = 3.6V, VOUT = 1.2V, IOUT = 0A Rising Falling EN Pin Threshold vs. Input Voltage 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 Input Voltage (V) EN Pin Threshold (V) VOUT = 1.2V, IOUT = 0A Rising Falling VREF vs. Temperature 0.588 0.590 0.592 0.594 0.596 0.598 0.600 0.602 0.604 0.606 0.608 0.610 0.612 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature VREF (V) (°C) Efficiency vs. Output Current 100 Output Current (A) Efficiency (%) VOUT = 1.2V, COUT = 10μF, L = 2.2μH VIN = 2.5V VIN = 3.3V UVLO Threshold vs. Temperature 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature UVLO Threshold (V) (°C) VOUT = 1.2V, IOUT = 0A Rising Falling
DS8010B-00 July 2007www.richtek.com Preliminary Output Voltage vs. Loading Current 1.180 1.185 1.190 1.195 1.200 1.205 1.210 1.215 1.220 1.225 1.230 Loading Current (A) Output Voltage (V) VIN = 3.6V Output Voltage vs. Temperature 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature Output Voltage (V) VIN = 3.6V, IOUT = 0A (°C) Frequency vs. Temperature 1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature Frequency (MHz) VIN = 3.6V, VOUT = 1.2V, IOUT = 300mA (°C) Frequency vs. Input Voltage 1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 Input Voltage (V) Frequency (MHz) VIN = 3.6V, VOUT = 1.2V, IOUT = 300mA Output Current Limit vs. Temperature 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature Output Current limit (A) VIN = 3.6V VOUT = 1.2V VIN = 3.3V (°C) Output Current Limit vs. Input Voltage 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 Input Voltage (V) Output Current limit (A) VOUT = 1.2V @ TA = 25°C
DS8010B-00 July 2007 www.richtek.com Preliminary Power On from EN Time (100 μs/Div) VIN = 3.6V, VOUT = 1.2V, IOUT = 10mA VOUT (1V/Div) VEN (2V/Div) IIN (500mA/Div) Load Transient Response Time (50 μs/Div) VIN = 3.6V, VOUT = 1.2V IOUT = 50mA to 1A VOUT (50mV/Div) IOUT (500mA/Div) Load Transient Response Time (50 μs/Div) VIN = 3.6V, VOUT = 1.2V IOUT = 50mA to 0.5A VOUT (50mV/Div) IOUT (500mA/Div) Power On from EN Time (100 μs/Div) VIN = 3.6V, VOUT = 1.2V, IOUT = 1A VOUT (1V/Div) VEN (2V/Div) IIN (500mA/Div) Output Ripple Voltage Time (500ns/Div) VIN = 3.6V, VOUT = 1.2V IOUT = 0A VOUT (10mV/Div) VLX (2V/Div) Output Ripple Voltage Time (500ns/Div) VIN = 3.6V, VOUT = 1.2V IOUT = 1A VOUT (10mV/Div) VLX (2V/Div)
DS8010B-00 July 2007www.richtek.com Preliminary ⎡ +≤ OUT LOUT 8fC 1ESR ΔIΔV Applications Information The basic RT8010B 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. 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 : Inductor Core Selection Once the value for L is known, the type of inductor must be selected. High efficiency converters generally can not afford the core loss found in low cost powdered iron cores, forcing the use of more expensive ferrite or mollypermalloy 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 copper losses will increase. Ferrite designs have very low core losses and are preferred at high switching frequencies, so design goals can concentrate on copper loss reduction and saturation prevention. Ferrite core material saturates “hard”, which means that inductance collapses abruptly when the peak IN OUTOUTL V V1Lf VΔI Δ×= IN(MAX) OUT L(MAX) OUT V V1If VL design current is exceeded. This results 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 do not radiate energy but generally cost more than powdered iron core inductors with similar characteristics. The choice of which style inductor to use mainly depends on the price vs size requirements and any radiated field/EMI requirements. C IN 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 : V V VII OUT IN IN OUT OUT(MAX)RMS −= This formula has a maximum at V IN = 2V OUT, where IRMS = I OUT/2. This simple worst-case condition is commonly used for design because even significant deviations do not offer much relief or choose a capacitor rated at a higher temperature than required. Several capacitors may also be paralleled 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 checked by viewing the load transient response as described in a later section. The output ripple, ΔV OUT, is determined by :
high voltage coefficient and audible piezoelectric effects. can also lead to significant ringing. of the output voltage as shown in Figure 4. Figure 4. Setting the Output Voltage actual power lost is of no consequence.
- The VIN quiescent current appears due to two factors
be more pronounced at higher supply voltages.
- I2R losses are calculated from the resistances of the
internal switches, RSW and external inductor RL.
and temperature difference between junction to ambient. θJA is the junction to ambient thermal resistance. by the regulator to return VOUT to its steady-state value. overshoot or ringing that would indicate a stability problem. LX node to prevent stray capacitive noise pick-up. \` Connect feedback network behind the output capacitors. components near the RT8010B. behind the output capacitors. Figure 5. Derating Curves for RT8010B Package temperature on the maximum power allowed.
Table 1. Recommended Inductors Table 2. Recommended Capacitors for CIN and COUT
DS8010B-00 July 2007www.richtek.com Richtek Technology Corporation Headquarter 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Richtek Technology Corporation Taipei Office (Marketing) 8F, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com Preliminary Outline Dimension W-Type 8L 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 0.300 0.008 0.012 D 1.950 2.050 0.077 0.081 D2 1.000 1.250 0.039 0.049 E 1.950 2.050 0.077 0.081 E2 0.400 0.650 0.016 0.026 e 0.500 0.020 L 0.300 0.400 0.012 0.016 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 D E A L be SEE DETAIL A