Datasheet

MAX5803/MAX5804/MAX5805
Ultra-Small, Single-Channel, 8-/10-/12-Bit Buffered Output
Voltage DACs with Internal Reference and I
2
C Interface
15Maxim Integrated
Detailed Description
The MAX5803/MAX5804/MAX5805 are single-channel,
low-power, 8-/10-/12-bit voltage-output digital-to-analog
converters (DACs) with an internal output buffer. The
wide supply voltage range of 2.7V to 5.5V and low
power consumption accommodate low-power and low-
voltage applications. The devices present a 100kI
(typ) load to the external reference. The internal output
buffer allows rail-to-rail operation. An internal voltage
reference is available with software selectable options
of 2.048V, 2.500V, or 4.096V. The devices feature a
fast 400kHz I
2
C-compatible interface. The MAX5803/
MAX5804/MAX5805 include a serial-in/parallel-out shift
register, internal CODE and DAC registers, a power-on-
reset (POR) circuit to initialize the DAC output to code
zero, and control logic. A user-configurable AUX pin
is available to asynchronously clear or gate the device
output independent of the serial interface.
DAC Output (OUT)
The MAX5803/MAX5804/MAX5805 include an internal
buffer on the DAC output. The internal output buffer
provides improved load regulation for the DAC output.
The output buffer slews at 1V/Fs (typ) and drives up to
2kI in parallel with 500pF. The analog supply voltage
(V
DD
) determines the maximum output voltage range
of the devices as V
DD
powers the output buffer. Under
no-load conditions, the output buffer drives from GND to
V
DD
, subject to offset and gain errors. With a 2kI load
to GND, the output buffer drives from GND to within and
200mV of V
DD
. With a 2kI load to V
DD
, the output buffer
drives from V
DD
to within 200mV of GND.
The DAC ideal output voltage is defined by:
OUT REF
N
D
VV
2
= ×
Where D = code loaded into the DAC register, V
REF
=
reference voltage, N = resolution.
Internal Register Structure
The user interface is separated from the DAC logic to
minimize digital feedthrough. Within the serial interface
is an input shift register, the contents of which can
be routed to control registers or the DAC itself, as
determined by the user command.
Within the device there is a CODE register followed by
a DAC Latch register (see the Functional Diagram).
The contents of the CODE register hold pending DAC
output settings which can later be loaded into the DAC
registers. The CODE register can be updated using both
CODE and CODE_LOAD user commands. The contents
of the DAC register hold the current DAC output settings.
The DAC register can be updated directly from the serial
interface using the CODE_LOAD commands or can
upload the current contents of the CODE register using
LOAD commands or the LDAC input.
The contents of both CODE and DAC registers are
maintained during all software power-down states, so that
when the DAC is returned to a normal operating mode, it
returns to its previously stored output settings. Any CODE
or LOAD commands issued during software power-down
states continue to update the register contents. The
SW_CLEAR command clears the contents of the CODE
and DAC registers to the user-programmable default
values. The SW_RESET command resets all configuration
registers to their power-on default states, while resetting
the CODE and DAC registers to zero scale.
Internal Reference
The MAX5803/MAX5804/MAX5805 include an internal
precision voltage reference that is software selectable to
be 2.048V, 2.500V, or 4.096V. When an internal reference
is selected, that voltage is available on the REF pin
for other external circuitry (see the Typical Operating
Circuits) and can drive a 25kI load.
External Reference
The external reference input features a typical input
impedance of 100kI and accepts an input voltage
from +1.24V to V
DD
. Connect an external voltage
supply between REF and GND to apply an external
reference. The MAX5803/4/5 power up and reset to
external reference mode. Visit www.maximintegrated.
com/products/references for a list of available external
voltage-reference devices.
AUX Input
The MAX5803/MAX5804/MAX5805 provide an asynchro-
nous AUX (active-low) input. Use the CONFIG command
to program the device to use the input in one of the fol-
lowing modes: CLR (default), GATE, or disabled. If not
using the AUX functions, connect this input to V
DDIO
.
CLR Mode
In CLR mode, the AUX input performs an asynchronous
level sensitive CLEAR operation when pulled low. If
CLR is configured and asserted, all CODE and DAC