The onboard excitation current section
requires high voltage to satisfy high compliance range. The board features an
onboard booster stage that generates 24 V out of the input which can range from 1.8
V to 5.5 V, best practice is using the use of the same source of the analog LDO, 5.2
V.
To use the onboard booster:
- Make sure the analog supply is
connected (D2 is on)
- Connect the external source (5.2
V) to J3
- Short J11, verify that J12 is
unconnected, D3 turns on when the supply is active
- Current can be measured using an
ammeter instead of the short on J11. The estimated current is about 16 mA. The
voltage when measured at J11 is not exactly 24 V but is about 23.8 V due to LDO
drop.
The estimated current from the 5.2-V
analog supply of the booster is below 100 mA.
If external supply is used:
- Make sure the analog supply is
connected
- Make sure J11 is open
- Connect the external high voltage
source (8 V to 36 V, typical 24 V) to J12, D3 turns on
The estimated current from the high
voltage external supply is 16 mA.
Note: To measure the input and output ripples of the booster stage, use test points TP5,
TP6.