Rainbow Electronics MAX5661 - Manual (Page 27)

MAX5661
Single 16-Bit DAC with Current and Voltage
Outputs for Industrial Analog Output Modules
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TO OUTPUT
CIRCUITRY
FULL-SCALE
OUTPUT ADJUST
OUTI
OUTV
SCLK
DIN
DAC
REGISTER
CONTROL
REGISTER
SHIFT
REGISTER
INPUT
REGISTER
FULL-SCALE
ADJUST
REGISTER
CLEAR
REGISTER
LDAC
DAC
DOUT
SOFTWARE
LOAD DAC
2-TO-1
MUX
CS
MAX5661
Figure 7. Functional Diagram
± 2 LSB
LDAC
OUT_
t LDL
t DELAY
Figure 8. LDAC Timing
Reference Input
Connect an external voltage reference in the +4V to
+4.2V range through a 1kΩ series resistor to
the buffered REF input. Use a high-accuracy, low-
noise +4.096V voltage reference such as the
MAX6126AASA41 (3ppm/°C temperature drift and
0.02% initial accuracy) for best 16-bit static accuracy.
REF does not accept AC signals. See Table 17 for a list-
ing of +4.096V references.
LDAC Input
The MAX5661 features an active-low load DAC (LDAC)
logic input that allows asynchronous updates to the
DAC outputs. Drive LDAC high to V
CC during normal
operation while controlling the MAX5661 using only the
serial interface. Drive LDAC low to update the DAC out-
put with the input register data. Hold LDAC low to make
the input register transparent and immediately update
the DAC output with the input register data. Figure 8
shows the LDAC timing with respect to OUT_.