MAX548AEUA+ Maxim Integrated Products, MAX548AEUA+ Datasheet - Page 6

• Manufacturer Part Number: MAX548AEUA+
• Description: IC DAC 8BIT DUAL ASYNCH 8-UMAX
• Manufacturer: Maxim Integrated Products

Specifications of MAX548AEUA+

• Settling Time: 4µs
• Number Of Bits: 8
• Data Interface: Serial
• Number Of Converters: 1
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Number Of Dac Outputs: 2
• Resolution: 8 bit
• Interface Type: Serial (SPI)
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 2.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Supply Current: 0.55 mA
• Voltage Reference: External
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power Dissipation (max): -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

The MAX548A/MAX549A/MAX550A are 8-bit, voltage-
output digital-to-analog converters (DACs). The
MAX548A/MAX549A are dual DACs, and the MAX550A
is a single DAC. Each DAC consists of an R-2R ladder
network that converts 8-bit digital inputs into equivalent
analog output voltages in proportion to the applied ref-
erence voltage (Figure 1).
The DACs feature double-buffered inputs and
unbuffered outputs. The MAX549A/MAX550A require
an external reference. The MAX548A’s reference inputs
are internally connected to V
range is from +2.5V to +5.5V.
The voltage applied at REF (V
the full-scale output for all the DACs and may range
from +2.5V to V
dependent, with the lowest value occurring with code
01010101 (55 hex). To minimize INL errors, the refer-
ence voltage source should have less than 3Ω output
impedance.
The MAX548A/MAX549A/MAX550A contain DACs with
unbuffered outputs; each output connects directly to an
R-2R ladder. Typical output impedance is 33.3kΩ. This
configuration minimizes power consumption and
reduces offset errors. For highest accuracy, apply high
resistive loads (1MΩ and up). Lower resistive loads can
be driven, but output loading increases full-scale error.
+2.5V to +5.5V, Low-Power, Single/Dual,
8-Bit Voltage-Output DACs in µMAX Package
Figure 1. DAC Simplified Circuit Diagram
6
_______________Detailed Description
_______________________________________________________________________________________
GND
NOTE: SWITCH POSITIONS SHOWN FOR DAC CODE FF HEX.
REF
2R
DD
LSB
. The REF input resistance is code
2R
R
DD
DD
for the MAX548A) sets
2R
. The power-supply
Analog Section
R
Reference Input
DAC Output
2R
R
DAC_ REGISTER
2R
2R
R
The magnitude of the expected error is the ratio of the
DAC output resistance to the DC load resistance at the
output.
Typically, an energy pulse is coupled into the DAC out-
put on CS’s rising edge. Since each DAC output is
unbuffered, connecting a small capacitor (200pF to
1000pF) from the output to ground creates a lowpass
filter that effectively suppresses the pulse for sensitive
applications (see Typical Operating Characteristics ).
When the MAX548A/MAX549A/MAX550A are in shut-
down mode, the R-2R ladder disconnects from the refer-
ence source. The MAX549A/MAX550A supply current
does not change, but the REF input current decreases to
less than 1µA. This allows the externally applied system
reference to remain active with minimal power
consumption. The MAX548A supply current also
decreases to less than 1µA in shutdown mode. When the
MAX548A/MAX549A/MAX550A exit shutdown mode,
recovery time is equivalent to the DAC’s settling time.
The serial interface is SPI/QSPI and Microwire compati-
ble. An active-low chip select (CS) enables the input
shift register to receive data from the serial input (DIN).
Data is clocked into the shift register on the rising edge
of the serial-clock signal (SCLK). The clock frequency
can be as high as 10MHz.
Transmit data MSB first in one 16-bit word or two 8-bit
bytes. The write cycle can be segmented to allow two
8-bit-wide transfers when CS remains low. After all 16
bits are clocked into the input shift register, a rising
2R
R
2R
R
2R
R
MSB
2R
2R
Serial Interface
Shutdown Mode
OUT_
GND