Datasheet ADR1500 (Analog Devices) - 7

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ADR1500 2.4V TRANSIENT RESPONSE
Many ADCs and DACs present transient current loads to the
V 0V IN
reference. Poor reference response can degrade the converter’s
OUTPUT ERROR
performance. Figure 12 displays both the coarse and fine
1mV/DIV 2µs/DIV
settling characteristics of the device to load transient of ±50 μA. It shows the settling characteristics of the device for an increased reverse current of 50 μA and the response when the reverse current is decreased by 50 μA. The transients settle to 1 mV in about 3 μs.
OUTPUT
11 0
0.5mV/DIV 2ms/DIV
9- 574
20mV/DIV 1mV/DIV
0 Figure 10. Turn-On Settling Time
IR = 100µA + 50µA STEP
Attempts to drive a large capacitive load (in excess of 1000 pF) can result in ringing. This is due to the additional poles formed by the load capacitance and the output impedance of the reference. A recommended method for driving capacitive loads of this magnitude is shown in Figure 11.
RS = 11.5kΩ RL IR = 100µA – 50µA STEP + VIN VR CL VOUT
-012 13 49
–
0 9-
20mV/DIV 1mV/DIV 1µs/DIV
057 574 0 Figure 11. Turn-On, Settling, and Transient Test Circuit Figure 12. Transient Settling Time A resistor isolates the capacitive load from the output stage, while the capacitor provides a single-pole, low-pass filter and lowers the output noise. Rev. 0 | Page 7 of 8 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION PIN CONFIGURATION TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ELECTRICAL CHARACTERISTICS ABSOLUTE MAXIMUM RATINGS ESD CAUTION TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION APPLYING THE ADR1500 TURN-ON TIME TRANSIENT RESPONSE OUTLINE DIMENSIONS ORDERING GUIDE