SC2620 Semtech Corporation, SC2620 Datasheet
SC2620
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SC2620 Summary of contents
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... Due to the SC2620’s high frequency operation, small inductors and ceramic capacitors can be used, resulting in very compact power supplies. The two channels of the SC2620 operate at 180° out of phase for reduced input voltage ripples. Separate soft start/enable pins allow independent control of each channel ...
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... SC2620 ° ° ° ...
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... µ SC2620 µ µ µ ...
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... SC2620 ...
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... Semtech Corp SLOPE COMP PWM - R 1V 0.7V REFERENCE FAULT & THERMAL SHUTDOWN SLOPE SLOPE COMP 2 COMP 1 SLOPE COMP CLK1 FREQUENCY CLK2 DIVIDER Figure 2. SC2620 Block Diagram (Channel 1.8 A 1V/2V 2 SC2620 PVIN1 4 + ISEN - 6.3m + 20mV ILIM - BOOST1 2 Q POWER TRANSISTOR FB1 SW1 ...
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... Temperature (°C) V Shutdown Current 200 T = 25°C A 150 100 SS1 SS2 ( SC2620 Normalized Channel Frequency vs Temperature 1.10 600kHz 1.05 1.00 1.4MHz 0.95 0.90 1.5 -50 - Temperature (°C) Boost Pin Current vs Switch Current BST 60 -40° ...
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... SS1 SS2 COMP1 COMP2 0 0.0 0.5 1.0 1.5 2.0 V (V) SS Efficiency vs Load Current 3.3V 80 OUT1 1.2V OUT2 Figure 1(a 0.5 1 1.5 Load Current ( Overload Threshold vs Temperature 1.0 0.9 0.8 0.7 0.6 0.5 2.0 -50 - Temperature (°C) =12V IN 2 SC2620 75 100 125 www.semtech.com ...
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... When either SS pin is released, the corresponding soft-start capacitor is charged with a 2µA current source (not shown in Figure 3). As either SS voltage exceeds 0.3V, the internal bias circuit of the SC2620 is enabled. The SC2620 draws 3.5mA from V circuit quickly charges the soft-start capacitor to 1V. At this juncture, the fast charge circuit turns off and the 1.8µ ...
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... The propagation delay time required to immediately turn off the switch after it is turned on is the minimum controllable switch on time (T measurement of the SC2620 with low 205 ) 061 % . ...
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... POWER MANAGEMENT Applications Information www.DataSheet4U.com that the minimum on time is about 105ns at room temperature (Figure 5). The power switch in the SC2620 is either not turned on at all or for at least T D required switch on time (= ) is shorter than the minimum f on time, the regulator will either skip cycles or it will jitter. ...
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... RMS ripple current in the input capacitor to a fraction of that of a single-phase buck converter. If both power transistors in the SC2620 were to switch on in phase, the current drawn by the SC2620 would consist of current pulses with amplitude equal to the sum of the channel output currents. If each channel ...
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... The bootstrapped output (the common node between D and connected to the BOOST pin of the SC2620. BST The power transistor in the SC2620 is first switched on to build up current in the inductor. When the transistor is switched off, the inductor current pulls the SW node low, allowing C switch is again turned on, the SW voltage goes high ...
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... > 2.5V CBST VIN VOUT D RECT = MAX V DBST VS > VIN + 2.5V BST BOOST VIN IN SW SC2620 GND (d) Figure 7. Methods of Bootstrapping the SC2620 every cycle, where BST RECT anode voltage. Switch base current discharges BST BST RECT ...
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... In general efficiency penalty increases as D decreases. Figure 7 summarizes various ways of bootstrapping the SC2620. A fast switching PN diode (such as 1N4148 or 1N914) and a small (0.1µF – 0.47µF) ceramic capacitor can be used. In Figure 7(a) the power switch is bootstrapped from the output. This is the most efficient ...
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... Shutdown and Soft-Start Each regulating channel of the SC2620 has its own soft- start circuit. Pulling its soft-start pin below 0.8V with an open-collector NPN or an open-drain NMOS transistor turns off the corresponding regulator. The other regulator continues to operate ...
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... Notice that the inductor current, not the converter output voltage, is ramped during soft-start. Both soft-start capacitors are charged to a final voltage of about 2.4V. Overload / Short-Circuit Protection Each current limit comparator in the SC2620 limits the peak inductor current to 3.2A (typical). The regulator CONTROL1 CSS1 M1 CONTROL2 ...
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... The SC2620 will reach its cycle-by-cycle current limit sometime during the soft-start charging phase (see Figure 17(c)). As described previously, the switches in the SC2620 either do not turn on at all or for at least 105ns. With the output shorted, the error amplifier will command the regulator to operate at full duty cycle. The current limit comparator will turn off the switch if the switch current exceeds 3 ...
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... output-to-control transfer v v COMP FB is also shown in Figure 12. Its mid OUT and OUT OUT www.semtech.com SC2620 function The –20dB/ 5 and p ) will 1 2 ...
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... Figure 12. Making gives a first-order estimate determines the mid-band loop gain of the 5 increases the mid-band gain and small ceramic capacitor to roll off the loop 6 v COMP v OUT SC2620 : 5 (12) www.semtech.com ...
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... V =16V IN V =1.2V OUT 40 s/div Inductor Current, 0.5A/div 2 (b) and I are switched OUT1 OUT2 www.semtech.com SC2620 2 A and ( MAX ) ...
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... 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 SC2620, connecting the anodes of both freewheeling diodes close to the negative terminal of the input bypass capacitor 150 pF minimizes size of the switched current loop ...
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... C15 C15 Suggested PCB Layout for the SC2620. 22 SC2620 OUT1 IN or OUT1 AGND AGND C16 C16 R10 R10 C10 C10 C8 ...
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... 10.7k C16 D2 0.1 F 10BQ 015 L2 OUT2 1.8 H 1.2V/ 0.1 F 2.15k 10.7k OUT1 Upper Trace : OUT2 Voltage, AC Coupled, 0.2V/div Lower Trace : L OUT 23 SC2620 Efficiency 3.3V OUT1 1.2V OUT2 0.5 1 1.5 Load Current (A) OUT2 40 s/div Inductor Current, 0 ...
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... C1: Murata GRM21BR60J 226M L2 : Coiltronics DR73 C3: Murata GRM31CR60J476M C15: Murata GRM32DR61E106K constitute the feedback voltage divider for Channel 1.5A). Figure 17(c). Channel 2 Output Short-circuit Hiccup. OUT1 OUT2 24 SC2620 OUT1 C11 5V/2A R1 47pF 60.4k R11 C1 80. C12 15.0k 47pF R12 4 ...
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... VIN C16 D2 SS2 0.1 F UPS140 COMP2 SW2 C4 D4 0.1 F 1N4148 FB2 BOOST2 GND L1 : Coiltronic DR74 L2 : Coiltronic DR73 s/div V = 12V IN 1 SC2620 OUT1 C11 5V/2A R1 47pF 60. C12 R2 47pF 15.0k L2 OUT2 10 H 1.5V/2A R3 5.76k 11. CH1 : SW1 Voltage, 10V/div CH2 : SW2 Voltage, 10V/div ...
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... H .080 .085 .090 2.03 2.16 2. .010 .020 0.25 0.50 .016 .028 .041 0.40 0.72 1. (.041) (1.04 0° 8° 0° 8° .004 0.10 .010 0.25 .008 0. (L1) A DETAIL A -H- DIMENSIONS INCHES MILLIMETERS (.205) (5.20) .114 2.90 .201 5.10 .094 2.40 .118 3.00 .050 1.27 .024 0.60 .087 2.20 .291 7.40 SC2620 www.semtech.com ...