PRECISION VOLTAGE REFERENCE FOR DATA
The ADR42x family has a number of features that make it ideal
for use with ADCs and DACs. The exceptionally low noise,
tight temperature coefficient, and high accuracy characteristics
make the ADR42x ideal for low noise applications such as
cellular base station applications.
AD7701 is an example of an ADC that is well suited for the
ADR42x. The ADR421 is used as the precision reference for
the converter in Figure 49. The AD7701 is a 16-bit ADC with
on-chip digital filtering intended for measuring wide dynamic
range and low frequency signals, such as those representing
chemical, physical, or biological processes. It contains a charge-
balancing (Σ-Δ) ADC, calibration microcontroller with on-chip
static RAM, clock oscillator, and serial communications port.
Figure 49. Voltage Reference for 16-Bit ADC AD7701
PRECISION BOOSTED OUTPUT REGULATOR
A precision voltage output with boosted current capability
can be realized with the circuit shown in Figure 50. In this
circuit, U2 forces VOUT to be equal to VREF by regulating the turn
on of N1. Therefore, the load current is furnished by VIN. In
this configuration, a 50 mA load is achievable at VIN of 5 V.
Moderate heat is generated on the MOSFET, and higher current
can be achieved by replacing the larger device. In addition, for
a heavy capacitive load with step input, a buffer may be added
at the output to enhance the transient response.
Figure 50. Precision Boosted Output Regulator
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