AD7839 Analog Devices, AD7839 Datasheet - Page 9

• Manufacturer Part Number: AD7839
• Description: Octal 13-Bit, Parallel Input, Voltage-Output D/A Converter
• Manufacturer: Analog Devices

Specifications of AD7839

• Resolution (bits): 13bit
• Dac Update Rate: 33kSPS
• Dac Settling Time: 30µs
• Max Pos Supply (v): +15.75V
• Single-supply: No
• Dac Type: Voltage Out
• Dac Input Format: Par

Power-On with CLR Low
The output stage of the AD7839 has been designed to allow
output stability during power-on. If CLR is kept low during
power-on, then just after power is applied to the AD7839, the
situation is as depicted in Figure 14. G
while G
V
G
parallel with the gain resistors of the output amplifier. The
output amplifier is connected as a unity gain buffer via G
the DUTGND voltage is applied to the buffer input via G
amplifier’s output is thus at the same voltage as the DUTGND
pin. The output stage remains configured as in Figure 14 until
the voltage at V
–3 V. By now the output amplifier has enough headroom to
handle signals at its input and has also had time to settle. The
internal power-on circuitry opens G
G
fier is configured in its noise gain configuration via G
The DUTGND voltage is still connected to the noninverting
input via G
V
opening of G
via the configuration shown in Figure 15.
When CLR is taken back high, the output stage is configured as
shown in Figure 16. The internal control logic closes G
opens G
gain-of-two configuration. The voltage that appears on the V
pins is determined by the data present in the DAC registers.
REV. 0
OUT
OUT
Figure 14. Output Stage with V
CLR Low
5
6
Figure 15. Output Stage with V
CLR Low
. This situation is shown in Figure 15. Now the output ampli-
and a 14 k resistor. This thin-film resistor is connected in
is kept within a few hundred millivolts of DUTGND via
has been disconnected from the DUTGND pin by the
2
DAC
DAC
2
, G
. The output amplifier is connected in a noninverting
2
3
and this voltage appears at V
5
and G
, but will track the voltage present at DUTGND
DD
G
G
G
G
1
1
2
exceeds 7 V and V
2
5
are closed.
DUTGND
DUTGND
R
R
G
G
4
4
G
G
G
G
3
5
3
5
R
R
3
DD
14k
DD
14k
and G
SS
1
< 7 V or V
> 7 V and V
, G
G
G
is more negative than
6
OUT
6
4
5
and G
and closes G
.
SS
6
SS
are open
> –3 V;
4
V
V
OUT
and G
OUT
< –3 V;
1
2
. The
and
3
, and
4
and
OUT
6
.
–9–
Power-On with CLR High
If CLR is high on the application of power to the device, the
output stages of the AD7839 are configured as in Figure 17
while V
G
DAC to the input of its output amplifier. G
while G
a unity gain buffer. V
through a 14 k resistor until V
negative than –3 V.
When the difference between the supply voltages reaches +10 V,
the internal power-on circuitry opens G
and G
1
Figure 18. Output Stage Powering Up with CLR High;
V
Figure 17. Output Stage Powering Up with CLR High
While V
is closed and G
DD
Figure 16. Output Stage After CLR Is Taken High
6
> 7 V and V
DD
4
configuring the output stage as shown in Figure 18.
DAC
DAC
DAC
and G
is less than 7 V and V
DD
< 7 V or V
6
are open, thus connecting the output amplifier as
G
G
G
G
2
G
G
1
1
1
SS
2
2
is open, thereby connecting the output of the
2
OUT
< –3 V
DUTGND
DUTGND
DUTGND
R
R
R
SS
is connected to DUTGND via G
> –3 V
G
G
G
4
4
4
SS
DD
G
G
G
G
G
G
3
5
3
5
3
5
is more positive than –3 V.
exceeds 7 V and V
R
R
R
14k
14k
14k
3
G
G
G
and G
6
6
6
3
and G
5
AD7839
and closes G
5
are closed
V
V
V
SS
OUT
OUT
OUT
is more
5
4