Evaluation Board User Guide
ADXRS450 - UG
Rev. 0 | Page 15 of 17
ALTERNATE EXTERNAL HIGH VOLTAGE SUPPLY
As described in the Hardware Configuration section, and
shown again in Figure 21, the default jumper positions
configures the part to use an on board boost converter in order
to generate a high voltage (approx. 24V) input signal. This
boost converter is supported through circuitry internal to the
ADXRS450, and requires an external inductor and diode for
proper operation. Refer to the ADXRS450 datasheet for a full
description of the boost converter operation.
Figure 24:Default Jumper Configuration
If the end application has an external high voltage supply
available, and the user would like to omit the inductor and
diode, then the satellite board can be modified in order to
accept this supply. Figure 22 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 ADXRS450.
The supply requirements are described in detail in the
ADXRS450 datasheet. In short, the main requirement for the
external high voltage supply is to ensure that 0.1mA to 1mA of
current is supplied to the device. The nominal internal voltage
is 22.5V. As an example, assume that a 30V supply is available
in the end application.
1.
22.5V (typ) is required internally
2.
30V is available externally
3.
Therefore, 7.5V will be dropped across the external
resistor
4.
In order to ensure between 0.1mA and 1mA, a
12kOhm resistor can be chosen.
a.
This will source 0.625mA to the ADXRS450
The user can then test the satellite board, in exactly the same
ways described throughout this user guide. This will allow the
user to verify that their external supply will satisfy the
requirements of the ADXRS450 accounting for both supply
tolerances and temperature effects.
Figure 25: Jumper Configuration for External High Voltage Supply
Analog Devices
ADXRS800 Satellite
C
onne
c
tor
Default
Jumper
Positions
Do Not
Populate
Resistor
Analog Devices
ADXRS800 Satellite
C
onne
c
tor
External
HV Supply
Jumper
Position
Remove
Jumper
Populate
Resistor
(Application Specific)
