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XTR111 Noise/Slew Rate Follow-up Testing. Ian Williams 2/23/11. Background. “Customer X” desires the following performance: ≤ 100 µ s slew from 10%-90% ≤ 5mVp (10mVpp) AC noise No RC filter required at load
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XTR111 Noise/Slew Rate Follow-up Testing Ian Williams 2/23/11
Background • “Customer X” desires the following performance: • ≤ 100µs slew from 10%-90% • ≤ 5mVp (10mVpp) AC noise • No RC filter required at load • Multiple transmitter-side capacitor values were tested to determine if this is possible
Test Circuit 50-94nF • Changing R8 alters the output current/voltage, so only C3 was varied in these tests • Capacitance values tested: 50nF, 60nF, 70nF, 77nF, 94nF
Slew Rate Test #1C3 = 50nF (5*10nF) • 10% to 90% slew time: 72µs
Noise Test #1C3 = 50nF (5*10nF) • AC noise: 20.21mVpp
Slew Rate Test #2C3 = 60nF (6*10nF) • 10% to 90% slew time: 82µs
Noise Test #2C3 = 60nF (6*10nF) • AC noise: 18.00mVpp
Slew Rate Test #3C3 = 70nF (7*10nF) • 10% to 90% slew time: 92µs
Noise Test #3C3 = 70nF (7*10nF) • AC noise: 16.59mVpp
Slew Rate Test #4C3 = 77nF (47nF + 3*10nF) • 10% to 90% slew time: 100µs
Noise Test #4C3 = 77nF (47nF + 3*10nF) • AC noise: 15.99mVpp
Slew Rate Test #5C3 = 94nF (2*47nF) • 10% to 90% slew time: 123µs
Noise Test #5C3 = 94nF (2*47nF) • AC noise: 13.47mVpp
Conclusion • Using C3 = 77nF provided the best noise performance (8mVp) while still meeting the 100µs 10% to 90% slew requirement • If the slew rate requirement is relaxed slightly, the 5mVp noise requirement can be met with a larger C3 value