Electronic Components Datasheet Search
  English  ▼
ALLDATASHEET.COM

X  

ADS7844NG4 Datasheet(PDF) 10 Page - Texas Instruments

Click here to check the latest version.
Part # ADS7844NG4
Description  ANALOG-TO-DIGITAL CONVERTER
Download  22 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Manufacturer  TI1 [Texas Instruments]
Direct Link  http://www.ti.com
Logo TI1 - Texas Instruments

ADS7844NG4 Datasheet(HTML) 10 Page - Texas Instruments

Back Button ADS7844NG4 Datasheet HTML 6Page - Texas Instruments ADS7844NG4 Datasheet HTML 7Page - Texas Instruments ADS7844NG4 Datasheet HTML 8Page - Texas Instruments ADS7844NG4 Datasheet HTML 9Page - Texas Instruments ADS7844NG4 Datasheet HTML 10Page - Texas Instruments ADS7844NG4 Datasheet HTML 11Page - Texas Instruments ADS7844NG4 Datasheet HTML 12Page - Texas Instruments ADS7844NG4 Datasheet HTML 13Page - Texas Instruments ADS7844NG4 Datasheet HTML 14Page - Texas Instruments Next Button
Zoom Inzoom in Zoom Outzoom out
 10 / 22 page
background image
ADS7844
10
SBAS100A
www.ti.com
cally 25pF). After the capacitor has been fully charged, there
is no further input current. The rate of charge transfer from
the analog source to the converter is a function of conversion
rate.
REFERENCE INPUT
The external reference sets the analog input range. The
ADS7844 will operate with a reference in the range of
100mV to +VCC. Keep in mind that the analog input is the
difference between the +IN input and the –IN input as shown
in Figure 2. For example, in the single-ended mode, a 1.25V
reference, and with the COM pin grounded, the selected input
channel (CH0 - CH7) will properly digitize a signal in the
range of 0V to 1.25V. If the COM pin is connected to 0.5V,
the input range on the selected channel is 0.5V to 1.75V.
There are several critical items concerning the reference input
and its wide voltage range. As the reference voltage is re-
duced, the analog voltage weight of each digital output code
is also reduced. This is often referred to as the LSB (least
significant bit) size and is equal to the reference voltage
divided by 4096. Any offset or gain error inherent in the A/D
converter will appear to increase, in terms of LSB size, as the
reference voltage is reduced. For example, if the offset of a
given converter is 2 LSBs with a 2.5V reference, then it will
typically be 10 LSBs with a 0.5V reference. In each case, the
actual offset of the device is the same, 1.22mV.
Likewise, the noise or uncertainty of the digitized output will
increase with lower LSB size. With a reference voltage of
100mV, the LSB size is 24
µV. This level is below the
internal noise of the device. As a result, the digital output
code will not be stable and vary around a mean value by a
number of LSBs. The distribution of output codes will be
gaussian and the noise can be reduced by simply averaging
consecutive conversion results or applying a digital filter.
With a lower reference voltage, care should be taken to
provide a clean layout including adequate bypassing, a clean
(low noise, low ripple) power supply, a low-noise reference,
and a low-noise input signal. Because the LSB size is lower,
the converter will also be more sensitive to nearby digital
signals and electromagnetic interference.
The voltage into the VREF input is not buffered and directly
drives the capacitor digital-to-analog converter (CDAC)
portion of the ADS7844. Typically, the input current is
13
µA with a 2.5V reference. This value will vary by
microamps depending on the result of the conversion. The
reference current diminishes directly with both conversion
rate and reference voltage. As the current from the reference
is drawn on each bit decision, clocking the converter more
quickly during a given conversion period will not reduce
overall current drain from the reference.
DIGITAL INTERFACE
Figure 3 shows the typical operation of the ADS7844’s
digital interface. This diagram assumes that the source of the
digital signals is a microcontroller or digital signal processor
with a basic serial interface (note that the digital inputs are
over-voltage tolerant up to 5.5V, regardless of +VCC). Each
communication between the processor and the converter
consists of eight clock cycles. One complete conversion can
be accomplished with three serial communications, for a
total of 24 clock cycles on the DCLK input.
The first eight clock cycles are used to provide the control
byte via the DIN pin. When the converter has enough
information about the following conversion to set the input
multiplexer appropriately, it enters the acquisition (sample)
mode. After three more clock cycles, the control byte is
complete and the converter enters the conversion mode. At
this point, the input sample/hold goes into the hold mode.
The next twelve clock cycles accomplish the actual analog-
to-digital conversion. A thirteenth clock cycle is needed for
the last bit of the conversion result. Three more clock cycles
are needed to complete the last byte (DOUT will be LOW).
These will be ignored by the converter.
Control Byte
Also shown in Figure 3 is the placement and order of the
control bits within the control byte. Tables III and IV give
detailed information about these bits. The first bit, the ‘S’ bit,
must always be HIGH and indicates the start of the control
byte. The ADS7844 will ignore inputs on the DIN pin until
the start bit is detected. The next three bits (A2 - A0) select
the active input channel or channels of the input multiplexer
(see Tables I and II and Figure 2).
FIGURE 2. Simplified Diagram of the Analog Input.
Converter
+IN
IN
CH0
CH1
CH2
CH3
A2-A0
(shown 000
B)
(1)
SGL/DIF
(shown HIGH)
CH4
CH5
CH6
CH7
COM
NOTE: (1) See Truth Tables, Table 1,
and Table 2 for address coding.


Similar Part No. - ADS7844NG4

ManufacturerPart #DatasheetDescription
logo
Burr-Brown (TI)
ADS7844N BURR-BROWN-ADS7844N Datasheet
204Kb / 14P
   12-Bit, 8-Channel Serial Output Sampling ANALOG-TO-DIGITAL CONVERTER
ADS7844NB BURR-BROWN-ADS7844NB Datasheet
204Kb / 14P
   12-Bit, 8-Channel Serial Output Sampling ANALOG-TO-DIGITAL CONVERTER
More results

Similar Description - ADS7844NG4

ManufacturerPart #DatasheetDescription
logo
Texas Instruments
TL505C TI-TL505C Datasheet
316Kb / 7P
[Old version datasheet]   ANALOG-TO-DIGITAL CONVERTER
ADS820 TI1-ADS820_13 Datasheet
409Kb / 20P
[Old version datasheet]   ANALOG-TO-DIGITAL CONVERTER
PCM2702 TI1-PCM2702_09 Datasheet
427Kb / 17P
[Old version datasheet]   DIGITAL-TO-ANALOG CONVERTER
PCM4201 TI1-PCM4201_16 Datasheet
847Kb / 26P
[Old version datasheet]   Analog-to-Digital Converter
PCM4204 TI1-PCM4204_16 Datasheet
1Mb / 38P
[Old version datasheet]   Analog-to-Digital Converter
ADS7821 TI1-ADS7821 Datasheet
201Kb / 11P
[Old version datasheet]   ANALOG-to-DIGITAL CONVERTER
ADS7805 TI1-ADS7805 Datasheet
949Kb / 20P
[Old version datasheet]   ANALOG-to-DIGITAL CONVERTER
ADS7809 TI1-ADS7809 Datasheet
1Mb / 20P
[Old version datasheet]   ANALOG-TO-DIGITAL CONVERTER
PCM1741 TI1-PCM1741_08 Datasheet
496Kb / 24P
[Old version datasheet]   DIGITAL-TO-ANALOG CONVERTER
PCM1718E TI1-PCM1718E_15 Datasheet
347Kb / 14P
[Old version datasheet]   DIGITAL-TO-ANALOG CONVERTER
PCM1728 TI1-PCM1728_15 Datasheet
328Kb / 16P
[Old version datasheet]   DIGITAL-TO-ANALOG CONVERTER
More results


Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22


Datasheet Download

Go To PDF Page


Link URL




Privacy Policy
ALLDATASHEET.COM
Does ALLDATASHEET help your business so far?  [ DONATE ] 

About Alldatasheet   |   Advertisement   |   Datasheet Upload   |   Contact us   |   Privacy Policy   |   Link Exchange   |   Manufacturer List
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com