MAX253 Maxim Integrated Products, MAX253 Datasheet
MAX253
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MAX253 Summary of contents
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... DC power supply. The secondary can be wound to provide any isolated voltage needed at power levels up to 1W. The MAX253 consists of a CMOS oscillator driving a pair of N-channel power switches. The oscillator runs at double the output frequency, driving a toggle flip-flop to ensure 50% duty cycle to each of the switches. ...
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... Shutdown Input Threshold Shutdown Input Leakage Current FS Input Threshold FS Input Leakage Current Start-Up Voltage Note 1: Operating supply current is the current used by the MAX253 only, not including load current. Note 2: Shutdown supply current includes output switch-leakage currents. 2 _______________________________________________________________________________________ Operating Temperature Ranges + 0.3V) MAX253C_ _ ........................................................0° ...
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Operating Characteristics (Circuit of Figure ±10 +25°C, unless otherwise noted OUTPUT RESISTANCE vs. TEMPERATURE (FS = LOW) 10.5 MEASURED AT TP1 10.0 9 4.5V IN 9.0 8.5 8.0 V ...
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Transformer Driver for Isolated RS-485 Interface ____________________________Typical Operating Characteristics (continued) (Circuit of Figure ±10 +25°C, unless otherwise noted EFFICIENCY vs. LOAD CURRENT (FS = HIGH) 100 5. ...
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... MAX253 with a linear regulator, a center-tapped trans- former, optocouplers, and the appropriate Maxim inter- face product (as described in the Isolated RS-485/RS- 232 Data Interface section). The MAX253 consists oscillator followed by a toggle flip-flop, which generates two 50% duty-cycle square waves, out-of-phase at half the oscillator fre- _______________________________________________________________________________________ ...
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... Transformer Driver for Isolated RS-485 Interface 0.1µ MAX253 ON / OFF GND1 GND2 74HC04 390 DI * 74HC04 390 DE 3.3k * 74HC04 RO * 74HC04 OR EQUIVALENT ** SEE TABLE 2 Figure 3. Typical RS-485 Application Circuit, 5V Configuration 6 _______________________________________________________________________________________ ISOLATION BARRIER 1N5817 ICT:1.3CT 0.1µF 8 1N5817 3 PC410 / 417 PC357T PC410 / 417 ...
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... V IN 3.3V C1 0.1µ N.C. 4 MAX253 ON / OFF GND1 GND2 2 7 1N5817 C5 0.1µF * 74HC04 390 DI * 74HC04 390 DE 3.3k * 74HC04 RO * 74HC04 OR EQUIVALENT ** SEE TABLE 2 Figure 4. Typical RS-485 Application Circuit, 3.3V Configuration _______________________________________________________________________________________ Transformer Driver for Isolated RS-485 Interface ISOLATION BARRIER 1N5817 ICT:2.1CT** ...
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... Transformer Driver for Isolated RS-485 Interface 0.1µ N.C. MAX253 OFF SD GND1 GND2 2 *74HC04 390 T1 IN 74HC04 390 T2 IN 74HC04 390 T3 IN 74HC04 390 T4 IN 74HC04 390 3.3k 74HC04 R1 OUT 74HC04 R2 OUT 74HC04 R3 OUT 74HC04 R4 OUT 74HC04 R5 OUT *74HC04 OR EQUIVALENT ** SEE TABLE 2 4N25 LOWER SPEED, LOWER COST ALTERNATE OPTOCOUPLER CONFIGURATIONS (FOR DATA RATES BELOW 9 ...
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... Figure 6 shows a typical 5V to isolated 5V application circuit that delivers up to 200mA of isolated 5V power. In Figure 7, the MAX253 is configured to operate from a 3.3V supply, deriving a “boost” V connecting diodes to both ends of the transformer pri- mary. This produces nearly double the input supply, and may be useful for other applications, as shown in Figure 4 ...
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... MAX253 3 FS FREQUENCY SWITCH GND1 GND2 2 7 *SEE TABLE 2 Figure 7. 3.3V to Isolated 5V Application Circuit 10 ______________________________________________________________________________________ 1N5817 ICT:1.3CT 0.1µF MAX253 8 D2 1N5817 OPTIONAL 21kHz LOWPASS OUTPUT FILTER GND2 2 7 OUTPUT 1N5817 ICT:2.1CT 0.1µ 1N5817 OPTIONAL 21kHz LOWPASS OUTPUT FILTER 1N5817 ...
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... MAX253 GND1 GND2 0.1V to 0.5V 6 MAX480 2 4 49.9k *SEE TABLE 2 Figure 8. Typical 4mA to 20mA Application Circuit Output-Ripple Filtering A simple lowpass pi-filter (Figures 6 and 7) can be added to the output to reduce output ripple noise to about 10mVp-p. The cutoff frequency shown is 21kHz. Since the filter inductor is in series with the circuit output, minimize its resistance so the voltage drop across it is not excessive ...
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... TABLE 2 Figure 9a. Half-Wave Rectifier—Bipolar V IN INPUT MAX253 8 D2 GND1 GND2 2 7 *SEE TABLE 2 Figure 9b. Full-Wave Rectifier—Bipolar V IN INPUT MAX253 8 D2 GND1 GND2 2 7 *SEE TABLE 2 Figure 9c. Full-Wave Rectifier—Unipolar 12 ______________________________________________________________________________________ 1N5817 1CT:1CT* +V OUTPUT + OUTPUT 1N5817 4 x 1N5817 1CT:1CT* ...
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... Transformer Driver for Isolated RS-485 Interface V IN ISOLATION 5V BARRIER 1CT : 1.5CT : 3CT 1N5817 79 L12 10µF 6N136 8 1 200 6N136 8 1 200 470 5 4 6N136 8. MAX253 ON/OFF D2 SD GND1 GND2 2 7 +5V 74HC04 START INPUT CLOCK SER 5 74HC595 SCK 3 D11(MSB D10 RCK +5V D8 SCLR QA 16 +5V 0.1µ ...
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... For +5V only applica- tions, the MAX187 is recommended. ______________Component Selection Transformer Selection The transformer primary used with the MAX253 must be a center-tapped winding with sufficient ET product to prevent saturation at the worst-case lowest selected frequency. The MAX253’s guaranteed minimum fre- quency with the FS pin held low is 150kHz, equating to a maximum period of 6.67µ ...
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... Output Voltage vs. Load Current in the Typical Operating Characteristics ). Transformers used with the MAX253 will ordinarily be wound on high-permeability magnetic material. To min- imize radiated noise, use common closed-magnetic- path physical shapes (e.g., pot cores, toroids, E/I/U cores). A typical core is the Philips 213CT050-3B7, which is a toroid 0.190” ...
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... Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 16 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 © 1994 Maxim Integrated Products 0.085" ...