MAX5100 Datasheet, PDF (6/8 Pages) Maxim Integrated Products – +2.7V to +5.5V, Low-Power, Quad, Parallel 8-Bit DAC with Rail-to-Rail Voltage Outputs

+2.7V to +5.5V, Low-Power, Quad, Parallel
8-Bit DAC with Rail-to-Rail Voltage Outputs
PIN
1
2
3
4
5
6
7–14
15
16
17
18
19
20
NAME
OUTB
OUTA
V_DD
REF
SHDN
WR
D7–D0
LDAC
A1
A0
GND
OUTD
OUTC
Pin Description
FUNCTION
DAC B Voltage Output
DAC A Voltage Output
Positive Supply Voltage. Bypass V_DD to GND using a 0.1µF capacitor.
Reference Voltage Input
Shutdown. Connect SHDN to GND for normal operation.
Write Input (active low). Use WR to load data into the DAC input latch selected by A0 and A1.
Data Inputs 7–0
Load DAC Input (active low). Drive the asynchronous LDAC input low to transfer the contents of all input
latches to their respective DAC latch.
DAC Address Select Bit (MSB)
DAC Address Select Bit (LSB)
Ground
DAC D Voltage Output
DAC C Voltage Output
Detailed Description
Digital-to-Analog Section
The MAX5100 uses a matrix decoding architecture for
the DACs. The external reference voltage is divided
down by a resistor string placed in a matrix fashion.
Row and column decoders select the appropriate tab
from the resistor string to provide the needed analog
voltages. The resistor network converts the 8-bit digital
input into an equivalent analog output voltage in pro-
portion to the applied reference voltage input. The
resistor string presents a code-independent input
impedance to the reference and guarantees a monoton-
ic output.
The device can be used in multiplying applications.
The voltages are buffered by rail-to-rail op amps con-
nected in a follower configuration to provide a rail-to-rail
output. The functional block diagram for the MAX5100
is shown in Figure 2.
Low-Power Shutdown Mode
The MAX5100 features a shutdown mode that reduces
current consumption to 1nA. A high voltage on the
shutdown pin shuts down the DACs and the output
amplifiers. In shutdown mode, the output amplifiers
enter a high-impedance state. When bringing the
device out of shutdown, allow 13µs for the output to
stabilize.
Output Buffer Amplifiers
The DAC outputs are internally buffered by precision
amplifiers with a typical slew rate of 0.6V/µs. The typical
settling time to ±1/2LSB at the output is 6µs when
loaded with 10kΩ in parallel with 100pF.
Reference Input
The MAX5100 provides a code-independent input
impedance on the REF input. The input impedance is
typically 460kΩ in parallel with 15pF, and the reference
input voltage range is 0 to V_DD. The reference input
accepts positive DC signals as well as AC signals with
peak values between 0 and V_DD. The voltage at REF
sets the full-scale output voltage for the DAC. The out-
put voltage (V_OUT) for any DAC is represented by a
digitally programmable voltage source as follows:
V_OUT = (N_B · V_REF) / 256
where N_B is the numeric value of the DAC binary input
code.
Digital Inputs and Interface Logic
In the MAX5100, address lines A0 and A1 select the
DAC that receives data from D0–D7, as shown in Table 1.
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