MAX5130 Maxim Integrated Products, MAX5130 Datasheet - Page 10

• Manufacturer Part Number: MAX5130
• Description: (MAX5130 / MAX5131) Voltage-output DACs
• Manufacturer: Maxim Integrated Products

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reference voltage. Use the circuits shown in Figure 3a
(MAX5130) and Figure 3b (MAX5131) to achieve these
adjustments. Connect a 33nF capacitor from REFADJ
to AGND to establish low-noise operation of the DAC.
Larger capacitor values may be used, but will result in
increased start-up delay. The time constant (
start-up delay is determined by the REFADJ input
impedance of 4kΩ and C
An external reference may be applied to the REF pin.
Disable the internal reference by pulling REFADJ to
V
DC-based) to be fed into the REF pin. For proper oper-
ation, do not exceed the input voltage range limits of
0V to (V
Determine the output voltage using the following equa-
tion (REFADJ = V
where NB is the numeric value of the MAX5130/
MAX5131 input code (0 to 8191), V
reference voltage, and 1.6384V/V is the gain of the
internal output amplifier. The REF pin has a minimum
input resistance of 40kΩ and is code-dependent.
The output amplifier of the MAX5130/MAX5131
employs a trimmed resistor-divider to set a gain of
+1.6384V/V and minimize the gain error. With its on-
board laser-trimmed +1.25V reference and the output
+3V/+5V, 13-Bit, Serial Voltage-Output DACs
with Internal Reference
Figure 3a. MAX5130 Reference Adjust Circuit
10
DD
. This allows an external reference signal (AC- or
______________________________________________________________________________________
100k
90k
DD
V
+5V
OUT
- 1.4V) for V
= [V
400k
DD
REF
33nF
; OS = AGND):
= 4kΩ · C
· (NB / 8192)] · 1.6384V/V
REF
REFADJ
.
REFADJ
REFADJ
External Reference
:
Output Amplifier
MAX5130
REF
is the external
for the
buffer gain, the MAX5131 achieves a full-scale output
of +2.04775V, while the MAX5130 provides a +4.0955V
full-scale output with a +2.5V reference.
The output amplifier has a typical slew rate of 0.6V/µs
and settles to ±0.5LSB within 20µs, with a load of 5kΩ
in parallel with 100pF. Loads less than 1kΩ may result
in degraded performance.
The OS pin may be used to adjust the output offset volt-
age. For instance, to achieve a +1V offset, apply
-1.566V (Offset = -[Output Buffer Gain - 1] · V
to produce an output voltage range from +1V to (1V +
V
still limited by the maximum output voltage specification.
The MAX5130/MAX5131 feature software- and hard-
ware-programmable (PD pin) shutdown modes that
reduce the typical supply current to 3µA. To enter soft-
ware shutdown mode, program the control sequence
for the DAC as shown in Table 1.
In shutdown mode, the amplifier output becomes high-
impedance and the serial interface remains active.
Data in the input registers is saved, allowing the
MAX5130/MAX5131 to recall the output state prior to
entering shutdown when returning to normal operation
mode. To exit shutdown mode, load both input and
DAC registers simultaneously or update the DAC regis-
ter from the input register. When returning from shut-
down mode, wait 2ms for the reference to settle. When
using an external reference, the DAC requires only
20µs for the output to stabilize.
Figure 3b. MAX5131 Reference Adjust Circuit
REF
· 1.6384V/V). Note that the DAC’s output range is
100k
15k
+3V
400k
33nF
REFADJ
Power-Down Mode
MAX5131
OS
) to OS