XTR111 Noise/Slew RateFollow-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

• Changing R8 alters the output current/voltage, so only C3 was varied in these tests• Capacitance values tested: 50nF, 60nF, 70nF, 77nF, 94nF

50-94nF

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

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