link to page 7 link to page 7 ADR15002.4VTRANSIENT RESPONSE Many ADCs and DACs present transient current loads to the V0VIN 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/DIV1mV/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 = 11.5kΩRLIR = 100µA – 50µA STEP+VINVRCL VOUT -012 13 49 – 0 9- 20mV/DIV1mV/DIV1µs/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