max5722 Maxim Integrated Products, Inc., max5722 Datasheet - Page 9

• Manufacturer Part Number: max5722
• Description: Max5722 12-bit, Low-power, Dual, Voltage-output Dac With Serial Interface
• Manufacturer: Maxim Integrated Products, Inc.

The MAX5722 contains two 12-bit, voltage-output, low-
power, digital-to-analog converters (DACs). Each DAC
employs a resistor string architecture that converts a
12-bit digital input word to an equivalent analog output
voltage proportional to the applied reference voltage.
The MAX5722 shares one reference input (REF)
between both DACs. The MAX5722 includes rail-to-rail
output buffer amplifiers for each DAC, and input logic
for simple microprocessor (µP), and CMOS interfaces.
The power-supply range is from +2.7V to +5.5V
(Functional Diagram). The MAX5722’s reference input
accepts a voltage range from 0 to V
mode the reference input is high impedance. The
MAX5722 is compatible with the 3-wire SPI, QSPI,
MICROWIRE, and DSP serial interface with Schmitt-trig-
gered logic inputs.
The reference input accepts positive DC and AC sig-
nals. The voltage at REF sets the full-scale output volt-
age of both DACs. The reference input voltage range is
0 to V
at REF can vary from GND to V
(V
voltage source as:
where D is the decimal equivalent of binary DAC input
code ranging from 0 to 4095. V
REF.
All DACs are internally buffered at the output. The
buffer amplifiers have both rail-to-rail common mode
OUT_
Reference Input and DAC Output Range
DD
PIN
7, 8
) are represented by a digitally programmable
1
2
3
4
5
6
. The impedance at REF is 90k . The voltage
V
OUTA, OUTB
OUT_
_______________________________________________________________________________________
12-Bit, Low-Power, Dual, Voltage-Output
NAME
SCLK
GND
V
REF
DIN
CS
DD
Detailed Description
= (V
Output Buffer Amplifiers
REF
✕
Power-Supply Input
Ground
Chip-Select Input
Serial-Clock Input
Serial Data Input
External Reference Voltage Input
DAC Voltage Outputs. Power-on reset sets DAC register to zero, and internally connects
OUT to GND with 100k resistor.
DD
D) / 2
REF
. The output voltages
DD
12
is the voltage at
. In power-down
DAC with Serial Interface
and (GND to V
are unity-gain stable with C
Buffer amplifiers are disabled during power-up and
individual DAC outputs are shorted to GND through a
100k
gether be powered-down by programming the input
register control bits. During power-down, contents of
the input and DAC registers remain the same. On
wake-up, all DAC outputs are restored to their pre-
power-down voltage values.
In power-down mode, the DAC outputs are pro-
grammed to one of three output states, 1k , 100k , or
floating (Table 1). The REF input is high impedance
(2M
reference; therefore, the system reference does not
have to be powered-down. The DAC outputs return to
the values contained in the registers when brought out
of power-down. The recovery time, from total power-
down to power-up, is 8µs. This extra time is needed to
allow the internal bias to wake-up. Power-down mode
reduces current consumption to 0.3µA.
The MAX5722 digital interface is a standard 3-wire con-
nection compatible with SPI/QSPI/MICROWIRE/DSP
interfaces. The chip-select input (CS) frames the serial
data loading at DIN. Immediately following CS high-to-
low transition, the data is shifted synchronously and
latched into the input register on the falling edge of the
serial clock input (SCLK). After 16 bits have been
loaded into the serial input register, it transfers its con-
tents to the DAC latch. CS may then either be held low
or brought high. CS must be brought high for a mini-
mum of 80ns before the next write sequence, since a
write sequence is initiated on a falling edge of CS. Not
typ), to conserve current drain from the system
resistor. Buffer amplifiers can individually or alto-
FUNCTION
REF
) output voltage range. The buffers
3-Wire Serial Interface
L
= 200pF and R
Pin Description
Power-Down Mode
L
= 5k .
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