Datasheet AD8615, AD8616, AD8618 (Analog Devices) - 12

link to page 12 link to page 12 link to page 12 link to page 12
AD8615/AD8616/AD8618 Data Sheet OVERLOAD RECOVERY TIME 5V 2.5V 10µF +
Overload recovery time is the time it takes the output of the
0.1µF 0.1µF
amplifier to come out of saturation and recover to its linear region. Overload recovery is particularly important in applications where
SERIAL V REFF REFS
small signals must be amplified in the presence of large transients.
DD INTERFACE 1/2 CS AD8616
Figure 40 and Figure 41 show the positive and negative overload
UNIPOLAR DIN AD5542 V OUTPUT
recovery times of the AD8616. In both cases, the time elapsed
OUT SCLK
before the AD8616 comes out of saturation is less than 1 μs. In
LDAC DGND AGND
addition, the symmetry between the positive and negative recovery 42 -0 48 times allows excellent signal rectification without distortion to the 46 0 output signal. Figure 42. Buffering DAC Output
LOW NOISE APPLICATIONS VS = ±2.5V RL = 10kΩ A
Although the AD8618 typically has less than 8 nV/√Hz of voltage
V = 100 +2.5V VIN = 50mV
noise density at 1 kHz, it is possible to reduce it further. A simple method is to connect the amplifiers in parallel, as shown in
0V
Figure 43. The total noise at the output is divided by the square root of the number of amplifiers. In this case, the total noise is
0V
approximately 4 nV/√Hz at room temperature. The 100 Ω resistor limits the current and provides an effective output resistance of 50 Ω.
3 VIN R3 –50mV V+ 1 R1 2 V– 100Ω
0 -04
10Ω
48
TIME (1µs/DIV)
46 0
R2
Figure 40. Positive Overload Recovery
1kΩ 3 R6 V V+ 1 S = ±2.5V RL = 10kΩ R4 2 V– 100Ω AV = 100 VIN = 50mV 10Ω R5 –2.5V VOUT 0V 1kΩ 0V 3 R9 V+ 1 R7 2 V– 100Ω 10Ω R8 1kΩ +50mV 3
1
R12
04
V+ 1
8-
TIME (1µs/DIV)
64
R10 2 V– 100Ω
04 Figure 41. Negative Overload Recovery
10Ω R11 D/A CONVERSION
3 04 8-
1kΩ
64 The AD8616 can be used at the output of high resolution DACs. 04 Figure 43. Noise Reduction The low offset voltage, fast slew rate, and fast settling time make the part suitable to buffer voltage output or current output DACs. Figure 42 shows an example of the AD8616 at the output of the AD5542. The AD8616’s rail-to-rail output and low distortion help maintain the accuracy needed in data acquisition systems and automated test equipment. Rev. G | Page 12 of 20 Document Outline Features Applications General Description Pin Configuration Table of Contents Revision History Specifications Absolute Maximum Ratings Thermal Resistance ESD Caution Typical Performance Characteristics Applications Information Input Overvoltage Protection Output Phase Reversal Driving Capacitive Loads Overload Recovery Time D/A Conversion Low Noise Applications High Speed Photodiode Preamplifier Active Filters Power Dissipation Power Calculations for Varying or Unknown Loads Calculating Power by Measuring Ambient Temperature and Case Temperature Calculating Power by Measuring Supply Current Outline Dimensions Ordering Guide