Datasheet

MAX5234/MAX5235
Detailed Description
The MAX5234/MAX5235 12-bit, voltage-output DACs
are easily configured with a 3-wire SPI, QSPI,
MICROWIRE serial interface. The devices include a 16-
bit data-in/data-out shift register and have an input con-
sisting of an input register and a DAC register. In
addition, these devices employ precision trimmed inter-
nal resistors to produce a gain of 1.6384V/V, maximizing
the output voltage swing, and a programmable shut-
down output impedance of 1kΩ or 200kΩ. The full-scale
output voltage is 4.095V for the MAX5235 and 2.0475V
for the MAX5234. These devices produce a weighted
output voltage proportional to the digital input code with
an inverted rail-to-rail ladder network (Figure 3).
External Reference
The reference inputs accept both AC and DC values
with a voltage range extending from 0.25V to 2.6V for
the MAX5235 and 0.25V to 1.5V for the MAX5234. For
proper operation do not exceed the input voltage
range limits. Determine the output voltage using the fol-
lowing equation:
V
OUT
_ = (V
REF
_ x NB / 4096) x 1.6384V/V
where NB is the numeric value of the DACs binary input
code (0 to 4095), V
REF
_ is the reference voltage, and
1.6384V/V is the gain of the internal output amplifier.
The code-dependent reference input impedance
ranges from a minimum of 28kΩ to several GΩ at code
0. The code-dependent reference input capacitance is
typically 23pF.
Output Amplifier
The output amplifiers have internal resistors that pro-
vide for a gain of 1.6384V/V. These trimmed resistors
minimize gain error. The output amplifiers have a typi-
cal slew rate of 0.6V/µs and settle to 1/2LSB within 10µs
(typ) with a load of 5kΩ in parallel with 100pF. Use the
serial interface to set the shutdown output impedance
of the amplifiers to 1kΩ or 200kΩ.
Single-Supply 3V/5V, Voltage-Output, Dual,
Precision 12-Bit DACs
10 ______________________________________________________________________________________
Pin Description
PIN NAME FUNCTION
1 OUTA DAC A Output
2 REFA Reference for DAC A
3 GND Ground
4 LDAC Load DACs A and B
5 CS Chip Select Input
6 SCLK Shift Register Serial Clock Input
7 DIN Serial Data Input
8V
DD
Positive Supply
9 REFB Reference for DAC B
10 OUTB DAC B Output
2µs/div
MAX5235
MAJOR-CARRY GLITCH
CS
2V/div
MAX5234 toc28
OUT_
50mV/div
AC-COUPLED
0
0.50
0.25
1.25
1.00
0.75
2.00
1.75
1.50
2.25
0 0.500.25 0.75 1.00 1.25
MAX5234
FULL-SCALE OUTPUT VOLTAGE
vs. REFERENCE VOLTAGE
MAX5234 toc29
V
REF
(V)
V
OUT
(V)
0
1.0
0.5
2.5
2.0
1.5
4.0
3.5
3.0
4.5
0 1.00.5 1.5 2.0 2.5
MAX5235
FULL-SCALE OUTPUT VOLTAGE
vs. REFERENCE VOLTAGE
MAX5234 toc30
V
REF
(V)
V
OUT
(V)
Typical Operating Characteristics (continued)
(V
DD
= +5V (MAX5235) V
DD
= +3V (MAX5234), R
L
= 5kΩ, C
L
= 100pF, V
REF
= +1.25V (MAX5234), V
REF
= +2.5V (MAX5235), C
REF
= 0.1µF ceramic || 2.2µF electrolytic, both DACs on, V
OUT
= full scale, T
A
= +25°C, unless otherwise noted.)