SC4901ITSTRT Semtech, SC4901ITSTRT Datasheet
SC4901ITSTRT
Specifications of SC4901ITSTRT
Related parts for SC4901ITSTRT
SC4901ITSTRT Summary of contents
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... Resistive or inductive current sensing with 2V current signal and 2.5V reference for external applications. 4.5 to 18V operation Max operating frequency to 1 MHz Low profile 16 pin TSSOP package Based on Semtech’s patented Combi Sync concept Applications Telecom isolated converters with multiple low voltage outputs ...
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... Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not implied Electrical Characteristics Unless specified 25°C, VCC = 12V 2005 Semtech Corp SC4901 ° C ° C ° C ° µ A µ A www.semtech.com ...
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... POWER MANAGEMENT Electrical Characteristics (Cont.) Unless specified 25°C, VCC = 12V 2005 Semtech Corp ° < < < I < ° ° ° ° SC4901 µ µ www.semtech.com ...
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... Notes: (1) Assured by design. Not tested in production. Pin Configurations TOP VIEW CS CS CAO 3 14 SSEN 4 13 AVCC 5 12 OUTB 6 11 XFRA 7 10 PGND 8 2005 Semtech Corp ° Ordering Information Notes: AGND 1) Only available in tape and reel packaging. A reel ZCD contains 2500 devices. ...
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... POWER MANAGEMENT Pin Descriptions 2005 Semtech Corp SC4901 www.semtech.com ...
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... POWER MANAGEMENT Block Diagram 2005 Semtech Corp. 6 SC4901 www.semtech.com ...
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... AVCC Volts Internal Reference vs Temperature 0.7550 0.7530 0.7510 0.7490 0.7470 0.7450 -40 -30 -20 - Temperature (°C) 2005 Semtech Corp. Current Amplifier Offset vs Temperature 4.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 -0.50 -1.00 -40 -30 -20 - 2.51 2.51 2.50 2 ...
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... The VEA follows the SSEN voltage and the output gradually ramps up. Once the SSEN pin charges to 3.3V, the soft start cycle is complete and the device is fully operational. 2005 Semtech Corp. ZCD and RCT Since the SC4901 is specifically designed for secondary side control, the oscillator is always derived from the transformer winding ...
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... VOLTAGE ZCD INPUT RCT RAM P Fig 2. Idealised ZCD and RCT waveforms 2005 Semtech Corp. The timings for the idealised waveforms above are easier to implement if the transformer has some form of constant volt-second operation or control; the secondary voltage can be directly used to charge the timing capacitor CT. The maximum input current into the RCT pin under clamped conditions should be limited ...
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... OUTB. This ensures that the forward FET pair is off before transformer voltage goes negative. 2005 Semtech Corp. Current Sense and Current Limit Current sensing is done as the input of an uncommitted differential amplifier. The current limit threshold is 2.5V at − ...
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... C u rre Fig 3a. Driving a Pulse Transformer using XFRA and OUTA with < 50% duty ratio 2005 Semtech Corp. If maximum duty ratio is more than 50% a ceramic capacitor C RES may be added in series to the transformer primary as shown in Fig 3b). The capacitor carries a small voltage only when duty ratio is more than 50% which correspondingly reduces the gate drive voltage during the ON time ...
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... Fig 3b. Driving the Pulse Transformer with > 50% duty ratio using using a series capacitor SIN GLE • • OPTION TOR RANSFORM ECONDARY RAM rre Fig 3c. Driving a Pulse Transformer with > 50% duty ratio using using a zener for reset 2005 Semtech Corp. DVCC OUT A P VCC - + DRES VCC OUT B XFRA DTO ...
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... The traces from the transformer to OUTA and XFRA pins must be kept short to minimise the overall inductance in the drive path. 2005 Semtech Corp. Reference Design and Typical Waveforms The complete schematic of a secondary channel delivering 3.3V/10A is shown in Fig 4). Typical waveforms are shown ...
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... POWER MANAGEMENT Application Information (Cont.) uF 100 uF 470 uF 470 R24 • 2005 Semtech Corp. CS SSEN XFR 7 XFRA1 PGND 8 • R54 14 SC4901 GND 16 ZCD 15 RCT REF www.semtech.com ...
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... Fig 6) Transformer scondary voltage (top), OUTA gate drive for forward MOSFET pair (center) and OUTB gate drive for the rectifying FET (botom) 2005 Semtech Corp. Fig 7) Transformer scondary voltage (top), rectified PWM output for 2.5V (center) and rectified PWM output for 3.3V (bottom) ...
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... Two approaches have been used to drive the MOSFETs. One is the self driven scheme where the transformer secondary itself provides the gate voltage for the appropriate FET. While the scheme is simple and has a very low cost, it has several limitations. 2005 Semtech Corp. • • ...
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... PWM duration ii) peak current crosses the overload limit or, iii) transformer secondary voltage begins to fall. 2005 Semtech Corp. d) After the forward FETs QS and QF are turned OFF, the rectifying FET QR is turned after a short delay. QR continues to conduct until the beginning of the next cycle when transformer secondary voltage goes positive again ...
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... MOS F ETs are sw it ched lay t o pre sho rt ing the se co nda ry w inding are t urne urne Turn OF F dela prev ent sho o t thro ugh 2005 Semtech Corp. FIg 11) Theoretical waveforms of Combi Sync topology GATE This e dge is Pulse Widt dula gulat ...
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... Note that peak current mode control is not suitable with the trailing edge modulation. 2005 Semtech Corp necessary to drive the forward FETs through a transformer interface. The common source of the two devices is a floating return and will swing to the peak negative voltage appearing at the transformer secondary ...
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... Land Pattern - TSSOP-16 X (C) P NOTES: 1. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. Contact Information Phone: (805)498-2111 FAX (805)498-3804 2005 Semtech Corp. DIMENSIONS INCHES MILLIMETERS DIM MIN NOM MAX MIN NOM MAX ...