Rainbow Electronics MAX5541 - Manual (Page 6)

MAX5541
Low-Cost, +5V, Serial-Input,
Voltage-Output, 16-Bit DAC
6 _______________________________________________________________________________________
;; ;; ;;;;;;;;; ;; ;;
t CSHO
t CH t CSSO t CL
t DH
t DS
t
CSH1
t CSS1
CS
SCLK
DIN D15 D14 D0
Figure 1. Timing Diagram
; ; ;;
CS
SCLK
DIN
MSB LSB
D15 D8 D7 D6 D5 D4 D3 D2 D1 D0
DAC
UPDATED
D14 D13 D12 D11 D10 D9
Figure 2. 3-Wire Interface Timing Diagram
Detailed Description
The MAX5541 voltage-output, 16-bit digital-to-analog
converter (DAC) offers 16-bit monotonicity with less
than 1LSB differential linearity error. Serial-data transfer
minimizes the number of package pins required.
The MAX5541 is composed of two matched DAC sec-
tions, with a 12-bit inverted R-2R DAC forming the
twelve LSBs and the four MSBs derived from fifteen
identically matched resistors. This architecture allows
the lowest glitch energy to be transferred to the DAC
output on major-carry transitions. It also decreases the
DAC output impedance by a factor of eight compared
to a standard R-2R ladder, allowing unbuffered opera-
tion in medium-load applications. Figure 1 is the Timing
Diagram.
Digital Interface
The MAX5541 digital interface is a standard 3-wire con-
nection compatible with SPI/QSPI/MICROWIRE inter-
faces. The chip-select input (CS) frames the serial data
loading at the data input pin (DIN). Immediately follow-
ing CSs high-to-low transition, the data is shifted
synchronously and latched into the input register on the
rising edge of the serial-clock input (SCLK). After 16
data bits have been loaded into the serial input regis-
ter, it transfers its contents to the DAC latch on CSs
low-to-high transition (Figure 2). Note that if CS does
not remain low during the entire sixteen SCLK cycles,
data will be corrupted. In this case, reload the DAC
latch with a new 16-bit word.
External Reference
The MAX5541 operates with external voltage refer-
ences from 2V to 3V. The reference voltage determines
the DACs full-scale output voltage.
Power-On Reset
The MAX5541 has a power-on reset (POR) circuit to set
the DACs output to 0V in unipolar mode when V
DD is
first applied. This ensures that unwanted DAC output
voltages will not occur immediately following a system
power-up, such as after power loss. In bipolar mode,
the DAC output is set to -V
REF .