max5893egk-d Maxim Integrated Products, Inc., max5893egk-d Datasheet - Page 28

• Manufacturer Part Number: max5893egk-d
• Description: Max5893 12-bit, 500msps Interpolating And Modulating Dual Dac With Cmos Inputs
• Manufacturer: Maxim Integrated Products, Inc.

For stable operation with the internal reference, REFIO
should be decoupled to GND with a 1µF capacitor.
REFIO must be buffered with an external amplifier, if
heavy loading is required, due to its 10kΩ output resis-
tance.
Alternatively, apply a temperature-stable external refer-
ence to REFIO (Figure 18). The internal reference is over-
driven by the external reference. For improved accuracy
and drift performance, choose a fixed output voltage ref-
erence such as the MAX6520 bandgap reference.
The MAX5893’s reference circuit (Figure 19) employs a
control amplifier, designed to regulate the full-scale
12-Bit, 500Msps Interpolating and Modulating
Dual DAC with CMOS Inputs
Figure 18. Typical External Reference Circuit
28
Table 5. I
*Terminated into a 50Ω load.
REFERENCE
EXTERNAL
______________________________________________________________________________________
1.25V
FULL-SCALE
I
OUTFS
CURRENT
10
15
20
I
REF
2
5
OUTFS
(mA)
R
1µF
SET
DACREF
FSADJ
REFIO
and R
REFERENCE
REFERENCE
SET
CURRENT
1.2V
I
REF
156.26
312.50
468.75
625.00
62.50
10kΩ
Selection Matrix Based on a Typical 1.20V Reference Voltage
(µA)
MAX5893
ARRAY DAC
CURRENT-
SOURCE
CALCULATED
19.2k
7.68k
3.84k
2.56k
1.92k
current I
DAC. The output current can be calculated as:
where I
V
of the DAC. Located between FSADJ and DACREF,
R
amplifier’s output current for the DAC. Use Table 5 for a
matrix of different I
Figure 19. MAX5893 Internal Reference Architecture
R
REFIO
SET
SET
1µF
I
REF
(Ω)
is the reference resistor, which determines the
REFIO
/ R
OUT
R
SET
I
SET
DACREF
1% EIA STD
OUTFS
FSADJ
REFIO
for the differential current outputs of the
I
is the reference output current (I
) and I
19.1k
3.83k
2.55k
1.91k
OUTFS
7.5k
= 32 x I
OUTFS
REFERENCE
OUT
= 32 x I
1.2V
10kΩ
is the full-scale output current
and R
REFIO
REFIO
SET
- (I
OUTPUT VOLTAGE
V
IOUTP/N
- 1LSB
OUT
selections.
MAX5893
ARRAY DAC
CURRENT-
/ 2
1000
SOURCE
100
250
500
750
* (mV
12
)
P-P
REFIO
)
=