AD9712BAN Analog Devices, AD9712BAN Datasheet - Page 6

• Manufacturer Part Number: AD9712BAN
• Description: 12-Bit/ 100 MSPS D/A Converters
• Manufacturer: Analog Devices

AD9712B/AD9713B
Full-scale output current is determined by CONTROL AMP
IN and R
The internal reference is nominally –1.18 V with a tolerance of
greater accuracy or better temperature stability is required, an
external reference can be utilized. The AD589 reference shown
in Figure 1 features 10 ppm/ C drift over temperatures from
0 C to +70 C.
Two modes of multiplying operation are possible with the
AD9712B/AD9713B. Signals with small signal bandwidths up
to 300 kHz and input swings of 100 mV, or dc signals from
–0.6 V to –1.2 V can be applied to the CONTROL AMP input
as shown in Figure 2. Because the control amplifier is internally
compensated, the 0.1 F capacitor at Pin 17 can be reduced to
0.01 F to maximize the multiplying bandwidth. However, it
should be noted that settling time for changes to the digital in-
puts will be degraded.
3.5% and typical drift over temperature of 50 ppm/ C. If
–0.6V TO –1.2V
300 kHz MAX
Figure 1. Use of AD589 as External Reference
Figure 2. Low Frequency Multiplying Circuit
I
SET
OUT
AD589
according to the equation:
(FS) = (CONTROL AMP IN/R
–V
S
+
–
~ – 11k
R
1
18
R
R
T
SET
19
CONTROL
AMP IN
19
17
24
18
AD9712B
AD9713B
R
CONTROL
AMP OUT
REFERENCE
IN
CONTROL
AMP IN
SET
SET
AD9712B
AD9713B
)
128
–6–
The REFERENCE IN pin can also be driven directly for wider
bandwidth multiplying operation. The analog signal for this
mode of operation must have a signal swing in the range of
–3.75 V to –4.25 V. This can be implemented by capacitively
coupling into REFERENCE IN a signal with a dc bias of –3.75 V
to –4.25 V, as shown in Figure 3; or by driving REFERENCE
IN with a low impedance op amp whose signal swing is limited
to the stated range.
Outputs
As indicated earlier, D
15 discrete current sinks. D5 and D6 are binarily weighted; and
D
tecture reduces frequency domain errors due to glitch impulse.
The Switch Network provides complementary current outputs
I
current source matching which provides 12-bit linearity without
trim. Current is steered to either I
the digital input code. The sum of the two currents is always
equal to the full-scale output current minus one LSB.
The current output can be converted to a voltage by resistive
loading as shown in Figure 4. Both I
loaded equally for best overall performance. The voltage which
is developed is the product of the output current and the value
of the load resistor.
OUT
7
–D
and I
12
are applied to the R-2R network. This segmented archi-
OUT
Figure 3. Wideband Multiplying Circuit
. These current outputs are based on statistical
–V
S
REFERENCE
~
–
1
IN
–D
–4V
4
(four MSBs) are decoded and drive
17
–V
OUT
S
OUT
or I
and I
AD9712B
AD9713B
OUT
OUT
in proportion to
should be
REV. B