as5043 austriamicrosystems, as5043 Datasheet - Page 7

• Manufacturer Part Number: as5043
• Description: 10-bit Programmable 360? Magnetic Angle Encoder With Absolute Digital And Analog Outputs
• Manufacturer: austriamicrosystems

AS5043 Programmable 360° Magnetic Angle Encoder
11 Analog Output
The analog output V
proportional to the angle of the rotating magnet and
ratiometric to the supply voltage VDD5V (max.5.5V). It
can source or sink currents up to ±1mA in normal
operation (up to 66mA short circuit current).
The analog output block consists of a digital angular
range selector, a 10-bit Digital-to-Analog converter and
an OPAMP buffer stage (see Figure 14).
The digital range selector allows a preselection of the
angular range for 360°,180°,90° or 45° (see Table 5).
Fine-tuning of the angular range can be accomplished by
adjusting the gain of the OPAMP buffer stage.
The reference voltage for the Digital-to-Analog converter
(DAC) can be taken internally from VDD5V / 2. In this
mode, the output voltage is ratiometric to the supply
voltage.
Alternatively, an external DAC reference can be applied
at pin DACref (#9). In this mode, the analog output is
ratiometric to the external reference voltage.
An on-chip diagnostic feature turns the analog output off
in case of an error (broken supply or magnetic field out of
range; see Table 3).
11.1 Analog output voltage modes
The Analog output voltage modes are programmable by OTP. Depending on the application, the analog output can be
selected as rail-to-rail output or as clamped output with 10%-90% VDD5V.
The output is ratiometric to the supply voltage (VDD5V), which can range from 3.0V to 5.5V. If the DAC reference is
switched to an external reference (pin DACref), the output is ratiometric to the external reference.
11.1.1
This output mode provides a ratiometric DAC output of (0% to 100%)x Vref
internal 2x gain, see Figure 14)
Revision 1.6, 3-Oct-06
analog
output
voltage
100%
Vref
0V
Full Scale Mode
0°
out
90°
provides an analog voltage that is
Figure 8: Analog output, full scale mode (shown for 360°mode)
180°
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270°
The DAC output can be accessed directly at pin #10
DACout.
The addition of an OPAMP to the DAC output allows a
variety of user configurable options, such as variable
output voltage ranges and variable output voltage versus
angle response. By adding an external transistor, the
analog voltage output can be buffered to allow output
currents up to hundred milliamperes or more.
Furthermore, the OPAMP can be configured as constant
current source.
As an OTP option, the DAC can be configured
different output ranges:
a) 0……100% V
taken from VDD5V/2 or from the external DACref input.
The 0…100% range allows easy replacement of
potentiometers. Due to the nature of rail-to-rail outputs,
the linearity will degrade at output voltages that are close
to the supply rails.
b) 10…..90% V
as the OPAMP is not driven to the rails. Furthermore, this
mode allows failure detection, when the analog output
voltage is outside of the normal operating range of
10…90%VDD, as in the case of broken supply or when
the magnetic field is out of range and the analog output
is turned off.
360°
angle
*)
, amplified by the OPAMP stage (default =
DACref
DACref
Note:
describes a linear output voltage from
rail to rail (0V to VDD). In practice, this
is not feasible due to saturation effects
of the OPAMP output driver transistors.
The actual curve will be rounded
towards the supply rails (as indicated in
Figure 8).
. This range allows better linearity,
. The reference point may be either
For
simplification,
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Figure
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