SC2440TETRT Semtech, SC2440TETRT Datasheet
SC2440TETRT
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SC2440TETRT Summary of contents
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... Two 2A Integrated Switches External Synchronization Thermal Shutdown Thermally Enhanced 16-pin TSSOP Package XDSL and Cable Modems Set-up Boxes Point of Load Applications CPE Equipment DSP Power Supplies Disk Drives Efficiency vs Load Current 12V IN V OUT2 3.3V OUT1 0.5 1 Load Current (A) SC2440 = 5V 1.5 2 www.semtech.com ...
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... Quiescent Current Shutdown Current Feedback Voltage Feedback Voltage Line Regulation FB Pin Input Bias Current Error Amplifier Transconductance Error Amplifier Open-loop Gain COMP Source Current COMP Sink Current COMP Pin to Switch Current Gain 2005 Semtech Corp. Symbol BST V -V BST SW V PGOOD ...
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... Notes: (1) Guaranteed by design, not tested in production. (2) The maximum duty cycle specified corresponds to 1.4MHz switching frequency. Duty cycles higher than those specified can be achieved by lowering the operating frequency. (3) This device is ESD sensitive. Use of standard ESD handling precautions is required. 2005 Semtech Corp. < 105° 12. ...
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... Underside GND SC2440. It also provides a thermal contact to the circuit board soldered to the ground Metal plane of the board. 2005 Semtech Corp. Ordering Information Part Number SC2440TETRT FB1 SC2440EVB COMP1 Notes: PGOOD1 (1) Only available in tape and reel packaging. A reel contains SS1 2500 devices. ...
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... EA + SS1 13 SS2 12 ROSC 5 OSCILLATOR SYNC 4 Figure 2. SC2440 Functional Diagram (One of Two Converters Shown FAULT Figure 3. Details of the Soft-Start and Overload Hiccup Control Circuit 2005 Semtech Corp. SLOPE COMP 1 + PWM - 1V 0.74V REFERENCE FAULT & THERMAL SHUTDOWN SLOPE SLOPE COMP 2 COMP 1 SLOPE COMP ...
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... Temperature (°C) Switch Current Limit vs Temperature 3.0 2.8 2.6 2.4 2.2 2.0 -50 - 100 125 Temperature (°C) 2005 Semtech Corp. Frequency Setting Resistor vs Channel Frequency 1000 = 5V 100 0.5 1 1.5 Frequency (MHz) Switch Saturation Voltage vs Switch Current 400 125°C -40°C ...
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... V ( Supply Current IN vs Soft-Start Voltage 25° SS1 SS2 COMP1 COMP2 0 0.0 0.5 1.0 1.5 V (V) SS 2005 Semtech Corp. V Quiescent Current 25°C 3 105° ( Overload Threshold vs Temperature 1.0 0.9 0.8 0.7 0.6 0.5 2.0 -50 - Temperature (°C) 7 Soft-Start Pin Current vs Soft-Start Voltage ...
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... The SS pin is a multiple-function pin. An external capacitor connected from the SS pin to the ground together with the internal 1.8µA and 2.6µA current sources set the 2005 Semtech Corp. soft-start and overload shutoff times of the regulator (Figure 3). The SS pin can also be used to shut off the corresponding regulator ...
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... Table 1. The 12V to 5V Converter in Figure 1 is modified to run at Different Frequencies. © 2005 Semtech Corp. Choosing the Operating Frequency The free-running frequency of the master set with an external resistor from the ROSC pin to ground. Channel frequency is one-half of that of the master oscillator. A graph of channel shown in the “ ...
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... the 1.0V and 3.3V converters can be calculated 2 using (2 2005 Semtech Corp ratio. In peak V OUT If the ambient temperature can be as high then ). Closed-loop ON (MIN) the maximum operating frequencies of the 1.0V and the V OUT ratios shows 3 ...
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... The frequency of the synchronizing clock should not be higher than 1.6 times 2005 Semtech Corp. the set frequency of master oscillator because the amplitudes of the internal sawtooth ramp and slope compensation ramp will both be significantly reduced. ...
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... For a single channel buck converter, the RMS ripple current in the input capacitor RMS OUT ( CIN ) 2005 Semtech Corp Power dissipated in the input capacitor (3), Equation (6) has a maximum value ...
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... To maximize efficiency, the turn-on voltage across the internal power NPN transistors should be minimized. If these transistors are to be driven into saturation, then their bases will have to be driven from a power supply 2005 Semtech Corp. higher in voltage than V voltage (at least 2.5V higher than the SW voltage over = 0.6A, ...
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... V is the applied D A base current discharges the bootstrap capacitor the end of conduction. The BST RECT BST difference between this voltage and that at SW must be 2005 Semtech Corp. DBST CBST VOUT D RECT = + > VIN + 2. CBST VOUT D RECT Figure 8. Methods of Bootstrapping the SC2440. ...
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... TO INPUT 4 Load Current (mA) (a) Figure 9. Minimum Input Voltage Required to Start and to Maintain Bootstrap.(T 2005 Semtech Corp. BOOST pin can be somewhat higher than 2V pin voltage should not exceed its absolute maximum rating of 40V. (if Figures 8(c) and (d) show how to bootstrap the SC2440 OUT from a second independent power supply V > ...
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... Figure 10(b). Start-up Fails due to (i) Short Soft-start Duration or (ii) Output Overload or (iii) Output Short-circuited. 2005 Semtech Corp. disabled. A 1.8µA current source continues to charge the soft-start capacitor (Figure 3). The soft-start voltage ramp at the SS pin clamps the error amplifier output current IN (Figure 2) ...
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... OFF Figure 11. Sequencing the Outputs by (a) Delaying Release of one Channel Relative to the Other and (b) Using the PGOOD of one Channel to Control the Other. 2005 Semtech Corp. When starting into a shorted output, the SC2440 will repeatedly start and shut off (“hiccup”). V will appear as asymmetrical triangular waves [Figure 10(b)] ...
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... Figure 12 shows a simplified equivalent circuit of a step- down converter. The power stage, which consists of the C6 Figure 12. Simplified Control Loop Equivalent Circuit 2005 Semtech Corp. current-mode PWM comparator, the power switch, the freewheeling diode and the inductor, feeds the output network. The power stage can be modeled as a voltage- ...
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... O 5 Figure 13. Bode Plots of Control-to-Ouput, Output-to-Control and the Overall Loop Gain. Control-to-output transfer function is shown with two poles near half the switching frequency 2005 Semtech Corp. forms a high frequency pole p component values shown in Figure 1 for the 12V to 3.3V R regulator (1.3MHz), 1 (9) ...
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... Increasing R increases the mid-band gain and 5 2005 Semtech Corp. the crossover frequency. However it reduces the phase margin. An estimate of R (11) and (12) with n=1. The compensation is then checked by measuring the loop gain and the phase or by observing ...
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... DC-DC Converter in Figure 1. (c) Channel 1 Load Transient Response, I 0.3A and 1.7A. (d) Channel 2 Load Transient Response, I 1.7A. 2005 Semtech Corp. For jitter-free operation, the size of the loop formed by these components should be minimized. Since the power switches are already integrated within the SC2440, ...
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... Figure 16. the device and that the only component on the backside is the frequency-setting resistor. All vias are 12mil in diameter. 2005 Semtech Corp. input pins. Shortening the traces of the SW and BOOST nodes reduces the parasitic trace inductance at these nodes. This not only reduces EMI but also decreases switching voltage spikes at these nodes ...
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... GND PGOOD2 100K Figure 17(a). 1.3MHz 5V to 3.3V and 1.8V Step-down Converter 20 s/div Upper Trace : OUT1 Voltage, AC Coupled, 0.2V/div Lower Trace : L Inductor Current, 0.5A/div 1 (b) Figures 17(b) and 17(c). Load Transient Response. I 2005 Semtech Corp. D3 1N4148 L1 OUT1 1.4 H 3.3V/2A R1 VIN D1 23.2K 5V ...
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... Figure 18(a). Producing an Output Lower than FB Voltage. 1.5MHz 5V to 2.5V and 0.8V Step-down Converter pre-load to shunt the current from R 3 CH1 2ms/div CH1 : OUT1 Voltage, 0.5V/div CH2 : OUT2 Voltage, 1V/div CH3 : SS2 Voltage, 1V/div CH4 : PGOOD2, 1V/div Figure 18(b). V Start-up Transient (I IN 2005 Semtech Corp FB1 COMP1 BOOST1 C2 BAT-54 470pF 0.1 F SW1 SS1 VIN ...
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... OUT1. This Bootstrapping Scheme Requires OUT1 to be Present at All Times (i.e. No Hiccup or Shutdown). Channel 2 will still Run if OUT1 is Absent. However its Power Disspation will be High 20V IN CH2 CH1 1 s/div CH1 : SW1 Voltage, 10V/div CH2 : SW2 Voltage, 10V/div Figure 19(b). Switching Waveforms. 2005 Semtech Corp. R6 100K D3 FB1 C5 PGOOD1 BOOST1 C2 1N4148 0.1 F ...
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... C SIDE VIEW EXPOSED PAD NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. DATUMS 3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. 4. REFERENCE JEDEC STD MO-153, VARIATION AB. Land Pattern - TSSOP-16 w/EDP (C) NOTES: 1. Contact Information 2005 Semtech Corp e bxN bbb C A-B D ...