AS3911B datasheet(32/155 Pages) AMSCO

32 / 155 page

AS3911B – 32

ams Datasheet: 2014-Jun-12 [v1-08]

A p pl i c at io n I n f o r m at i o n

A/D Converter

The AS3911B contains an 8-bit successive approximation A/D

converter. Input to A/D converter can be multiplexed from

different sources to be used in several direct commands and

adjustment procedures. The result of last A/D conversion is

stored in the A/D Converter Output Register. Typical conversion

time is 224/fc (16.5 μs).

The A/D converter has two operating modes, absolute and

relative.

• In absolute mode the low reference is 0V and the high

reference is 2 V. This means that A/D converter input range

is from 0 to 2 V, 00h code means input is 0 V or lower, FFh

means that input is 2 V - 1LSB or higher, LSB is 7.8125 mV.

• In relative mode low reference is 1/6 of VSP_A and high

reference is 5/6 of VSP_A, so the input range is from 1/6

VSP_A to 5/6 VSP_A.

Relative mode is only used in phase measurement (phase

detector output is proportional to power supply). In all other

cases absolute mode is used.

Phase and Amplitude Detector

This block is used to provide input to A/D Converter to perform

measurements of amplitude and phase, expected by direct

commands Measure Amplitude and Measure Phase. Several

phase and amplitude measurements are also performed by

direct commands Calibrate Modulation Depth and Calibrate

Antenna.

Phase Detector

The phase detector is observing phase difference between the

transmitter output signals (RFO1 and RFO2) and the receiver

input signals RFI1 and RFI2, which are proportional to the signal

on the antenna LC tank. These signals are first passed by

digitizing comparators. Digitized signals are processed by a

phase detector with a strong low pass filter characteristics to

get average phase difference. The Phase Detector output is

inversely proportional to the phase difference between the two

inputs. The 90° phase shift results in VSP_A/2 output voltage,

in case both inputs are in phase output voltage is VSP_A in case

they are in opposite phase output voltage is zero. During

execution of direct command Measure Phase this output is

multiplexed to A/D Converter input (A/D Converter is in relative

mode during execution of command Measure Phase). Since the

A/D converter range is from 1/6 VSP_A to 5/6 VSP_A the actual

phase detector range is from 30º to 150º. Figures below depict

the two inputs and output of phase detector in case of 90º and

135º phase shift.

AS3911B датащи(PDF) 32 Page - ams AG

AS3911B датащи(HTML) 32 Page - ams AG

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

датащи скачать

ссылки URL