AD7233(RevA) Ver la hoja de datos (PDF) - Analog Devices
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AD7233 Datasheet PDF : 8 Pages
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AD7233
Pin
Mnemonic
1
VDD
2
SCLK
3
SDIN
4
SYNC
5
LDAC
6
GND
7
VOUT
8
VSS
PIN FUNCTION DESCRIPTION
Description
Positive Supply (+12 V to +15 V).
Serial Clock, Logic Input. Data is clocked into the input register on each falling SCLK edge.
Serial Data In, Logic Input. The 16-bit serial data word is applied to this input.
Data Synchronization Pulse, Logic Input. Taking this input low initializes the internal logic in
readiness for a new data word.
Load DAC, Logic Input. Updates the DAC output. The DAC output is updated on the falling edge of
this signal, or alternatively if this line in permanently low, an automatic update mode is selected whereby
the DAC is updated on the 16th falling SCLK pulse.
Ground Pin = 0 V.
Analog Output Voltage. This is the buffered DAC output voltage (–5 V to +5 V).
Negative Supply (–12 V to –15 V).
VDD 1
SCLK 2
SDIN 3
SYNC 4
AD7233
TOP VIEW
(Not to Scale)
8 VSS
7 VOUT
6 GND
5 LDAC
CIRCUIT INFORMATION
D/A Section
The AD7233 contains a 12-bit voltage-mode D/A converter
consisting of highly stable thin-film resistors and high speed
NMOS single-pole, double-throw switches.
Op Amp Section
The output of the voltage-mode D/A converter is buffered by a
noninverting CMOS amplifier. The buffer amplifier is capable
of developing ± 5 V across a 2 kΩ load to GND.
R
R
2R 2R 2R
RR R
2R 2R 2R
2R
VOUT
INTERNAL
DB0 DB1
DB9 DB10 DB11
2R
REFERENCE
5V
GND
Figure 1. Simplified D/A Converter
DIGITAL INTERFACE
The AD7233 contains an input serial to parallel shift register
and a DAC latch. A simplified diagram of the input loading cir-
cuitry is shown in Figure 2. Serial data on the SDIN input is
loaded to the input register under control of SYNC and SCLK.
When a complete word is held in the shift register it may then be
loaded into the DAC latch under control of LDAC. Only the
data in the DAC latch determines the analog output on the
AD7233.
A low SYNC input provides the frame synchronization signal
which tells the AD7233 that valid serial data on the SDIN input
will be available for the next 16 falling edges of SCLK. An inter-
nal counter/decoder circuit provides a low gating signal so that
only 16 data bits are clocked into the input shift register. After
16 SCLK pulses the internal gating signal goes inactive (high)
thus locking out any further clock pulses. Therefore, either a
continuous clock or a burst clock source may be used to clock in
the data.
The SYNC input should be taken high after the complete 16-bit
word is loaded in.
Although 16 bits of data are clocked into the input register, only
the latter 12 bits get transferred into the DAC latch. The first 4
bits in the 16-bit stream are don’t cares since their value does
not affect the DAC latch data. Therefore the data format is 4
don’t cares followed by the 12-bit data word with the LSB as the
last bit in the serial stream.
–4–
REV. A
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