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ADDC02805SA データシート(PDF) 10 Page - Analog Devices |
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ADDC02805SA データシート(HTML) 10 Page - Analog Devices |
10 / 18 page ADDC02803SC/ADDC02805SA REV. A –10– Pin 6 (INHIBIT) Pin 6 is active low and is referenced to the input return of the converter. Connecting it to the input return will turn the con- verter off. For normal operation, the inhibit pin is internally pulled up to 12 V. Use of an open collector circuit is recommended. When Pin 6 is disconnected from input return, the converter will restart in the soft-start mode. Pin 6 must be kept low for at least 2 milliseconds to initiate a full soft start. Shorter off times will result in a partial soft start. Figure 31 shows the input characteristics of Pin 6. VIL – V 1.2 1.1 0.7 0.5 2.0 1.0 1.5 1.0 0.9 0.8 Figure 31. Input Characteristics of Pin 6 When Pulled Low Pin 7 (SYNC) Pin 7 can be used for connecting multiple converters to a mas- ter clock. This master clock can be either an externally user- supplied clock or a converter that has been modified and designated as a master unit. Capacitive coupling of the clock signal will ensure that if the master clock stops working the individual units will continue to operate at their own internal clock frequency, thereby eliminating a potential single point failure. Capacitive coupling will also permit a wider duty cycle to be used. Consult factory for more information. The SYNC pin has an internal pull-down so it is not necessary to sink any current when driving the pin low. Reference Figure 38 for a fault tolerant, secondary side powered SYNC drive circuit. For user-supplied master clocks with no external circuitry, the following specifications must be met: a. Frequency: 1.00 MHz min b. Duty cycle: 7% min, 14% max c. High state voltage high level: 4 V min to 7 V max d. Low state voltage low level: 0 V min to 3.0 V max Users should note that the SYNC pin is referenced to the input return of the converter. If the user-supplied master clock is generated on the output side of the converter, the signal should be isolated. Users should be careful about the frequency selected for the external master clock. Higher switching frequencies will reduce efficiency and may reduce the amount of output power available at minimum input line. Consult factory for modi- fied standard switching frequency to accommodate system clock characteristics. Pin 8 (ISHARE) Pin 8 allows paralleled converters to share the total load cur- rent, typically within ±5% at full load. To use the current share feature, connect all current share pins to each other and con- nect the SENSE pins on each of the converters. The current sharing function is sensitive to the differential voltage between the input return pins of paralleled converters. The current sharing function is also sensitive to noise, and care should be taken in the routing of connections. Refer to Figure 37 for typical appli- cation circuits using paralleled converters. Pin 9 (TEMP) Pin 9 can be used to indicate case temperature or to raise or disable the temperature at which thermal shutdown occurs. Typically, 3.90 V corresponds to +25 °C, with a +13.1 mV/°C change for every 1 °C rise. The sensor IC (connected from Pin 9 to the input return [Pin 10]) has a 13.1 k Ω impedance. The thermal shutdown feature has been set to shut down the converter when the case temperature is nominally 110 °C to 115 °C. To raise the temperature at which shutdown occurs, connect a resistor with the value shown in Figure 32 from Pin 9 to the input return (Pin 10). To completely disable the tempera- ture shutdown feature, connect a 50 k Ω resistor from Pin 9 to the input return (Pin 10). SHUTDOWN CASE TEMPERATURE – C 1400 0 120 150 125 130 135 140 145 1200 1000 800 400 200 600 Figure 32. External Resistor Value for Raising Temperature Shutdown Point INPUT VOLTAGE RANGE The steady state operating input voltage range for the converter is defined as 18 V to 40 V. The abnormal operating input voltage range is defined as 16 V to 50 V. In accordance with MIL-STD-704D, the converter can operate up to 50 V dc input for transient conditions as long as 50 milliseconds, and it can operate down to 16 V dc input for continuous operation during emergency conditions. Figure 4 (typical low line dropout vs. load) shows that the converter can work continuously down to and below 16 V dc under reduced load conditions. The ADDC02803SC and ADDC02805SA can be modified to survive, but not work through, the upper limit input voltages defined in MIL-STD-704A (aircraft) and MIL-STD-1275A (military vehicles). MIL-STD-704A defines an 80 V surge that lasts for 1 second before it falls below 50 V, while MIL-STD- 1275A defines a 100 V surge that lasts for 200 milliseconds |
同様の部品番号 - ADDC02805SA |
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同様の説明 - ADDC02805SA |
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