100_V_output_with_shunt_regulation

Published:2009/7/24 3:33:00 Author:Jessie | From:SeekIC

Figure 7-76 shows the MAX773 connected to provide 100-V output at 10 mA, with 24-V to 28-V input. Figure 7-77 shows the calculations for selecting the RSHUNT vaLue. RSHUNT should be selected so that ISHUNT is greater than 1 mA, but less than 20 mA. If the calculated shunt regulator current exceeds 20 mA, or if the shunt current exceeds 5 mA, and less shunt-regulator current is desired, use the circuit of Fig. 7-78. This provides increased drive and reduced shunt current when driving N-FETs with large gate capacitances. Use an ISHUNT of 3 mA. This provides adequate biasing current for the circuit, although higher shunt currents can be used. Notice that the shunt regulator is not disabled in the shutdown mode, and continues to draw the calculated shunt current. To prevent the shunt regulator from drawing current in the shutdown mode, place a switch in series with the shunt resistor.See Fig. 7-68 for component suppliers. MAXIM NEW RELEASES DATA Book, 1995, P. 4-152, 4-154.



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