DA C
Austin Semiconductor, Inc.
External Reference
To disable the AS5181 internal reference, connect REN\ to
DV
DD
. A temperature-stable, external reference may now be
applied to drive the REFO pin to set the full-scale output
(Figure 3). Choose a reference capable of supplying at least
150µA to drive the bias circuit that generates the cascode
current for the current array. For improved accuracy and drift
performance, choose a fixed output voltage reference.
AS5181
and current array are inactive and the DAC supply current is
reduced to 1µA. To enter this mode, connect PD to DV
DD
. To
return to active mode, connect PD to DGND and DACEN to
DV
DD
. About 50µs are required for the parts to leave shutdown
mode and settle to their outputs’ values prior to shutdown.
The “Power-Down Mode Selection” table lists the power-down
mode selection.
Timing Information
Standby Mode
To enter the lower-power standby mode, connect digital
inputs PD and DACEN to DGND. In standby, both the refer-
ence and the control amplifier are active with the current array
inactive. To exit this condition, DACEN must be pulled high
with PD held at DGND. The AS5181 typically require 50µs to
wake up and let both outputs and the reference settle.
Figure 4 shows a detailed timing diagram for the AS5181.
With each high transition of the clock, the input latch is loaded
with the digital value set by bits D9 through D0. The content of
the input latch is then shifted to the DAC register, and the
output updates at the rising edge of the next clock.
Outputs
The AS5181 output is designed to supply full-scale
output currents of 1mA into 400Ω loads in parallel with a
capacitive load of 5pF.
Shutdown Mode
For lowest power consumption, the AS5181 provide a
power-down mode in which the reference, control amplifier,
FIGURE 2: Setting I
FS
with the Internal +1.2V Reference and
the Control Amplifier
AS5181
Rev. 0.3 6/05
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
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AUSTIN [ AUSTIN SEMICONDUCTOR ]
