Alternate External High Voltage Supply - Analog Devices ADXRS800 User Manual

Evaluation Board User Guide

ALTERNATE EXTERNAL HIGH VOLTAGE SUPPLY

As discussed in the COM Port Verification section, and shown
again in Figure 24, the default jumper positions configure the
part to use an on-board boost converter to generate a high
voltage (approximately 24 V) input signal. This boost converter
is supported through circuitry internal to the ADXRS800 and
requires an external inductor and a diode for proper operation.
See the ADXRS800 data sheet for a full description of the boost
converter operation.
DEFAULT
JUMPER
POSITIONS
Figure 24. Default Jumper Configuration
If the end application has an external high voltage supply
available, and you want to omit the inductor and diode, you can
modify the satellite board to accept this supply. Figure 25 shows
the required jumper configuration when using an external high
voltage supply. Additionally, a footprint for a through-hole
resistor has been included. This resistor must be populated such
that, when combined with the high voltage supply, the proper
current is sourced to the ADXRS800.
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ANALOG DEVICES
ADXRS800 SATELLITE
DO NOT
POPULATE
RESISTOR
The supply requirements are described in detail in the
ADXRS800 data sheet. The main requirement for the external
high voltage supply is that 0.1 mA to 1mA of current be
supplied to the device. The nominal internal voltage is 22.5 V.
As an example, assume that a 30 V supply is available in the end
application. Then 22.5 V (typical) is required internally, and 30 V
is available externally. For this condition, 7.5 V is dropped
across the external resistor. To ensure that between 0.1 mA and
1 mA of current is sourced, a 12 kΩ resistor can be chosen. This
sources 0.625 mA to the ADXRS800.
You can then test the satellite board in exactly the same way as
described throughout this user guide and be able to verify that
your external supply meets the requirements of the ADXRS800,
accounting for supply tolerances and temperature effects.
REMOVE
JUMPER
(APPLICATION SPECIFIC)
Figure 25. Jumper Configuration for External High Voltage Supply
Rev. 0 | Page 15 of 16
ANALOG DEVICES
ADXRS800 SATELLITE
EXTERNAL
HV SUPPLY
JUMPER
POSITION
POPULATE
RESISTOR
UG-154