Electronic Components Datasheet Search
  English  ▼

Delete All
ON OFF
ALLDATASHEET.COM

X  

Preview PDF Download HTML

AD5678 Datasheet(PDF) 25 Page - Analog Devices

Part No. AD5678
Description  On-Chip Reference in 14-Lead TSSOP
Download  28 Pages
Scroll/Zoom Zoom In 100% Zoom Out
Maker  AD [Analog Devices]
Homepage  http://www.analog.com
Logo AD - Analog Devices

AD5678 Datasheet(HTML) 25 Page - Analog Devices

Back Button AD5678_15 Datasheet HTML 20Page - Analog Devices AD5678_15 Datasheet HTML 21Page - Analog Devices AD5678_15 Datasheet HTML 22Page - Analog Devices AD5678_15 Datasheet HTML 23Page - Analog Devices AD5678_15 Datasheet HTML 24Page - Analog Devices AD5678_15 Datasheet HTML 25Page - Analog Devices AD5678_15 Datasheet HTML 26Page - Analog Devices AD5678_15 Datasheet HTML 27Page - Analog Devices AD5678_15 Datasheet HTML 28Page - Analog Devices  
Zoom Inzoom in Zoom Outzoom out
 25 / 28 page
background image
AD5678
Rev. C | Page 25 of 28
LDAC FUNCTION
The outputs of all DACs can be updated simultaneously using
the hardware LDAC pin.
Synchronous LDAC: After new data is read, the DAC registers
are updated on the falling edge of the 32nd SCLK pulse. LDAC
can be permanently low or pulsed as in
.
Figure 2
Asynchronous LDAC: The outputs are not updated at the same
time that the input registers are written to. When LDAC goes low,
the DAC registers are updated with the contents of the input register.
Alternatively, the outputs of all DACs can be updated simulta-
neously using the software LDAC function by writing to Input
Register n and updating all DAC registers. Command 0011 is
reserved for this software LDAC function.
An LDAC register gives the user extra flexibility and control
over the hardware LDAC pin. This register allows the user to
select which combination of channels to simultaneously update
when the hardware LDAC pin is executed. Setting the LDAC bit
register to 0 for a DAC channel means that this channel’s update
is controlled by the LDAC pin. If this bit is set to 1, this channel
updates synchronously; that is, the DAC register is updated
after new data is read, regardless of the state of the LDAC pin. It
effectively sees the LDAC pin as being tied low. (See
for the
Table 15
LDAC register mode of operation.) This flexibility is
useful in applications where the user wants to simultaneously
update select channels while the rest of the channels are
synchronously updating.
Writing to the DAC using command 0110 loads the 8-bit LDAC
register (DB7 to DB0). The default for each channel is 0; that is,
the LDAC pin works normally. Setting the bits to 1 means the
DAC channel is updated regardless of the state of the LDAC
pin. See
for the contents of the input shift register
during the load
Table 16
LDAC register mode of operation.
POWER SUPPLY BYPASSING AND GROUNDING
When accuracy is important in a circuit, it is helpful to carefully
consider the power supply and ground return layout on the
board. The printed circuit board containing the AD5678 should
have separate analog and digital sections. If the AD5678 is in a
system where other devices require an AGND-to-DGND
connection, the connection should be made at one point only.
This ground point should be as close as possible to the AD5678.
The power supply to the AD5678 should be bypassed with 10 μF
and 0.1 μF capacitors. The capacitors should physically be as
close as possible to the device, with the 0.1 μF capacitor ideally
right up against the device. The 10 μF capacitors are the tantalum
bead type. It is important that the 0.1 μF capacitor has low effective
series resistance (ESR) and low effective series inductance (ESI),
such as is typical of common ceramic types of capacitors. This
0.1 μF capacitor provides a low impedance path to ground for
high frequencies caused by transient currents due to internal
logic switching.
The power supply line should have as large a trace as possible to
provide a low impedance path and reduce glitch effects on the
supply line. Clocks and other fast switching digital signals should
be shielded from other parts of the board by digital ground. Avoid
crossover of digital and analog signals if possible. When traces
cross on opposite sides of the board, ensure that they run at right
angles to each other to reduce feedthrough effects through the
board. The best board layout technique is the microstrip technique,
where the component side of the board is dedicated to the ground
plane only and the signal traces are placed on the solder side.
However, this is not always possible with a 2-layer board.
Table 15. LDAC Register
Load DAC Register
LDAC Bits (DB7 to DB0)
LDAC Pin
LDAC Operation
0
1/0
Determined by LDAC pin
1
X—don’t care
DAC channels update, overriding the LDAC pin. DAC channels see LDAC as 0.
Table 16. 32-Bit Input Shift Register Contents for LDAC Overwrite Function
MSB
LSB
DB31
to
DB28
DB27
DB26
DB25
DB24
DB23
DB22
DB21
DB20
DB19
to
DB8
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
X
0
1
1
0
X
X
X
X
X
DAC
H
DAC
G
DAC
F
DAC
E
DAC
D
DAC
C
DAC
B
DAC
A
Don’t
cares
Command bits (C3 to C0)
Address bits (A3 to A0)—
don’t cares
Don’t
cares
Setting LDAC bit to 1 overrides LDAC pin


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 


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   |   Alldatasheet API   |   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