User’s Manual
73
A
PPENDIX
C. P
OWER
S
UPPLY
Appendix C describes the power circuitry distributed on the
BL2000.
C.1 Power Supplies
Power is supplied to the BL2000 via a mini phone jack located at J7 or through the screw
terminal strip, header J2. The BL2000 itself is protected against reverse polarity by a
diode at D1 as shown in Figure C-1.
Figure C-1. BL2000 Power Supply
Capacitor C28 provides surge current protection for the voltage regulator, and allows the
external power supply to be located some distance away from the BL2000. A switching
power regulator is used. The input voltage range is from 9 V to 40 V.
The BL2000 can alternatively be powered by 24 V AC. In this case D1 and C28 act as a
half-wave rectifier to produce approximately 40 V DC at the input of the switching regula-
tor, U12. Although a significant drop will be measured at DCIN, the voltage will never
drop below +9 V DC. As long as the minimum input level is maintained at the input to the
regulator, Vcc will be held at +5 V DC.
Pin 12 on header J9 can be configured to either supply Vcc (0
Ω
surface-mounted resistor
installed at R160) or GND (0
Ω
surface-mounted resistor installed at R161). When using
pin 12 on header J9 to supply Vcc, take care not to draw more than 25 mA current from
this pin, especially if you are using 24 V AC as your +RAW input power supply. The R160
and R161 locations are shown in Figure A-4.
POWER
IN
J2 orJ7
47 µF
330 µF
U12
+RAW
Vcc
L1
C29
C28
330 µH
D1
D2
1N5819
14
15
8
1
12
7
17
18
10
2
3
4
1
SWITCHING POWER REGULATOR
TVS1
DCIN
LM2575
Summary of Contents for BL2020
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