EVAL-AD5700-1EBZ Просмотр технического описания (PDF) - Analog Devices

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EVAL-AD5700-1EBZ

Low Power HART Modem

Analog Devices 

AD5700/AD5700-1

TERMINOLOGY

VCC and IOVCC Current Consumption

This specification gives a summation of the current consump-

tion of both the VCC and the IOVCC supplies. Figure 11 shows

separate measurements for VCC and IOVCC currents vs. varying

capacitive loads, in transmit mode.

Load Regulation

Load regulation is the change in reference output voltage due to

a specified change in load current. It is expressed in ppm/µA.

CD Assert

The minimum value at which the carrier detect signal asserts is

85 mV p-p and the maximumvalue it asserts at is 110 mV p-p. CD

is already high (asserted) for HART input signals greater than

110 mV p-p. This specification was set assuming a sinusoidal

input signal containing preamble characters at the input and an

ideal external filter (see Figure 23).

Data Sheet

HART_OUT Output Voltage

This is the peak-to-peak HART_OUT output voltage. The

specification in Table 2 was set using a worst-case load of 160 Ω,

ac-coupled with a 2.2 µF capacitor. Figure 17 and Figure 18 show

HART_OUT output voltages for both resistive and purely

capacitive loads.

Mark/Space Frequency

A 1.2 kHz signal represents a digital 1, or mark, whereas a

2.2 kHz signal represents a 0, or space.

Phase Continuity Error

The DDS engine in this design inherently generates continuous

phase signals, thus avoiding any output discontinuity when

switching between frequencies. This attribute is desirable for

signals that are to be transmitted over a band limited channel,

because discontinuities in a signal introduce wideband fre-

quency components. As the name suggests, for a signal to be

continuous, the phase continuity error must be 0o.

Rev. G | Page 12 of 24

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