max5235 Maxim Integrated Products, Inc., max5235 Datasheet - Page 10

• Manufacturer Part Number: max5235
• Description: Single-supply 3v/5v, Voltage-output, Dual, Precision 12-bit Dacs
• Manufacturer: Maxim Integrated Products, Inc.

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
Single-Supply 3V/5V, Voltage-Output, Dual,
Precision 12-Bit DACs
(V
= 0.1µF ceramic || 2.2µF electrolytic, both DACs on, V
10
AC-COUPLED
DD
50mV/div
PIN
______________________________________________________________________________________
10
= +5V (MAX5235) V
1
2
3
4
5
6
7
8
9
2V/div
OUT_
CS
NAME
OUTA
LDAC
OUTB
REFA
SCLK
REFB
MAJOR-CARRY GLITCH
GND
V
DIN
CS
DD
MAX5235
2µs/div
Detailed Description
DD
= +3V (MAX5234), R
DAC A Output
Reference for DAC A
Ground
Load DACs A and B
Chip Select Input
Shift Register Serial Clock Input
Serial Data Input
Positive Supply
Reference for DAC B
DAC B Output
Pin Description
MAX5234 toc28
FUNCTION
Typical Operating Characteristics (continued)
2.25
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
L
0
= 5kΩ, C
OUT
0
FULL-SCALE OUTPUT VOLTAGE
= full scale, T
0.25
vs. REFERENCE VOLTAGE
L
= 100pF, V
0.50
MAX5234
V
REF
output voltage proportional to the digital input code with
an inverted rail-to-rail ladder network (Figure 3).
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:
where NB is the numeric value of the DACs binary input
code (0 to 4095), V
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.
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.
(V)
A
0.75
= +25°C, unless otherwise noted.)
REF
V
= +1.25V (MAX5234), V
1.00
OUT
_ = (V
1.25
REF
REF
_ x NB / 4096) x 1.6384V/V
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
_ is the reference voltage, and
0
FULL-SCALE OUTPUT VOLTAGE
REF
0.5
vs. REFERENCE VOLTAGE
External Reference
= +2.5V (MAX5235), C
Output Amplifier
1.0
MAX5235
V
REF
(V)
1.5
2.0
REF
2.5