Digi JACKRABBIT BL1800 - Manual (Page 23)

User’s Manual 19
3.2.2.1 Configurable High-Power Output (HV3)
HV3, shown schematically in Figure 7, is factory-configured to be a sourcing output.
Figure 7. Configurable High-Current Output
When used as a sourcing output, HV3 is switched to K when PE3 on the Rabbit 2000 goes
high, and the two transistors shown in Figure 7 are turned on. The maximum sourcing cur-
rent is 100 mA (BL1810 and BL1820) or 500 mA (BL1800), and the maximum K is 30 V.
This voltage limit on K arises because R51 and R52 at the base of Q28 can each dissipate
500 mW for a total of 1 W. The 30 V limit then constrains the sinking outputs as well
because K is common to all four high-current outputs.
HV3
PE3
D24
C28
100 nF
MMBT3906
Q28
R52
1.8 kW
MMBT4401
Q25
R48
470 W
R50
100 kW
R51
1.8 kW
R56
0 W
K
(sourcing)
HV3
0 W (sinking
option)
R55
C27
100 nF