max5480aeeet Maxim Integrated Products, Inc., max5480aeeet Datasheet - Page 4

• Manufacturer Part Number: max5480aeeet
• Description: Max5480 8-bit Parallel Dac In Qsop-16 Package
• Manufacturer: Maxim Integrated Products, Inc.

The MAX5480 is an 8-bit multiplying digital-to-analog
converter (DAC) that consists of a thin-film R-2R resistor
array with CMOS current steering switches. Figure 3
shows a simplified schematic of the DAC. The inverted
R-2R ladder divides the voltage or current reference in
a binary manner among the eight steering switches.
The magnitude of the current appearing at either OUT
terminal depends on the number of switches selected;
therefore, the output is an analog representation of the
digital input. The two OUT terminals must be held at the
same potential so a constant current is maintained in
each ladder leg. This makes the REF input current inde-
pendent of switch state and also ensures that the
MAX5480 maintains its excellent linearity performance.
The inputs CS and WR control the MAX5480’s operat-
ing mode (see Table 1).
When CS and WR are both low, the MAX5480 is in write
mode, and its analog output responds to data activity at
the D0–D7 data-bus inputs. In this mode, the data
latches are transparent (see Tables 2 and 3).
In hold mode, the MAX5480 retains the data that was
present on D0–D7 just prior to CS or WR assuming a
high state. The analog output remains at the value cor-
responding to the digital code locked in the data latch.
The MAX5480 can be used either as a current-output
DAC (Figures 1 and 6) or as a voltage-output DAC
(Figures 2 and 5).
To use the MAX5480 in voltage mode, connect OUT1 to
the reference input and connect OUT2 to ground. REF,
now the DAC output, is a voltage source with a con-
stant output resistance of 10kΩ (nominally). This output
is often buffered with an op amp (Figure 5).
An advantage of voltage-mode operation is single-
supply operation for the complete circuit; i.e., a nega-
tive reference is not required for a positive output. It is
important to note that the range of the reference is
restricted in voltage mode. The reference input (voltage
at OUT1) must always be positive and is limited to no
more than V
this value, linearity is degraded.
8-Bit Parallel DAC in
QSOP-16 Package
4
_______________Detailed Description
__________Applications Information
_______________________________________________________________________________________
DD
Using the MAX5480 in Voltage-
- 3V. If the reference voltage exceeds
Output Mode (Single Supply)
Interface-Logic Information
Mode Selection
Write Mode
Hold Mode
Figure 1. Unipolar Binary Operation (Two-Quadrant Multiplication)
Figure 2. Typical Operating Circuit (Voltage Mode—Unbuffered)
Table 1. Mode-Selection Table
L = Low State, H = High State, X = Don’t Care
INPUTS 4–11
DATA
CS
H
L
X
INPUT*
*(V
REF
DD
- 3V, max)
12
13
WR
2
H
X
L
1
D7–D0
CS
WR
15
OUT1
OUT2
REF
V
REF
MAX5480
16
MODE
R1
2k
13
Write
Hold
Hold
RFB
WR
3
GND
V
V
DD
DD
12
14
CS
MAX5480
R
FB
OUT1
OUT2
GND
3
16
DAC responds to data bus
(D0–D7) inputs.
Data bus (D0–D7) is locked out;
DAC holds last data present
when CS or WR assumed high
state.
1
2
R2
1k
R1 AND R2 USED ONLY IF GAIN
ADJUSTMENT IS REQUIRED.
10pF
DATA IN
DAC Response
D7–D0
4–11
+5V
V
DD
14
REF
MAX4330
15
OUTPUT
VOLTAGE
(10k OUTPUT
RESISTANCE)
V
OUT