Rainbow Electronics MAX5887 - Manual (Page 8)

MAX5887
3.3V, 14-Bit, 500Msps High Dynamic
Performance DAC with Differential LVDS Inputs
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Detailed Description
Architecture
The MAX5887 is a high-performance, 14-bit, current-
steering DAC (Figure 1) capable of operating with clock
speeds up to 500MHz. The converter consists of sepa-
rate input and DAC registers, followed by a current-
steering circuit. This circuit is capable of generating
differential full-scale currents in the range of 2mA to
20mA. An internal current-switching network in combi-
nation with external 50Ω termination resistors convert
the differential output currents into a differential output
voltage with a peak-to-peak output voltage range of
0.1V to 1V. An integrated 1.2V bandgap reference, con-
trol amplifier, and user-selectable external resistor
determine the data converter’s full-scale output range.
Reference Architecture and Operation
The MAX5887 supports operation with the on-chip 1.2V
bandgap reference or an external reference voltage
source. REFIO serves as the input for an external, low-
impedance reference source, and as the output if the
DAC is operating with the internal reference. For stable
operation with the internal reference, REFIO should be
decoupled to AGND with a 0.1µF capacitor. Due to its
limited output drive capability, REFIO must be buffered
with an external amplifier, if heavier loading is required.
The MAX5887’s reference circuit (Figure 2) employs a
control amplifier, designed to regulate the full-scale
current I
OUT for the differential current outputs of the
DAC. Configured as a voltage-to-current amplifier, the
output current can be calculated as follows:
I OUT = 32 ✕ I REFIO - 1LSB
I OUT = 32 ✕ I REFIO - (I OUT / 2 14 )
where I REFIO is the reference output current (I REFIO =
V
REFIO
/R
SET
) and I
OUT
is the full-scale output current of
the DAC. Located between FSADJ and DACREF, R SET
is the reference resistor, which determines the amplifi-
er’s output current for the DAC. See Table 1 for a matrix
of different I
OUT and R SET selections.
PIN NAME FUNCTION
45 B12N Complementary Data Bit 12
46 B11P Data Bit 11
47 B11N Complementary Data Bit 11
48 B10P Data Bit 10
49 B10N Complementary Data Bit 10
50 B9P Data Bit 9
51 B9N Complementary Data Bit 9
52 B8P Data Bit 8
53 B8N Complementary Data Bit 8
54 B7P Data Bit 7
55 B7N Complementary Data Bit 7
56 B6P Data Bit 6
57 B6N Complementary Data Bit 6
58 B5P Data Bit 5
59 B5N Complementary Data Bit 5
63 B4P Data Bit 4
64 B4N Complementary Data Bit 4
65 B3P Data Bit 3
66 B3N Complementary Data Bit 3
67 B2P Data Bit 2
68 B2N Complementary Data Bit 2
Pin Description (continued)