Z-World RabbitCore, Руководство пользователя

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User’s Manual 123
A
PPENDIX
D. P
OWER
S
UPPLY
Appendix D provides information on the current requirements
of the RCM3600, and includes some background on the chip
select circuit used in power management.
D.1 Power Supplies
Power is supplied from the motherboard to which the RCM3600 is connected via header
J1. The RCM3600 has an o3.3 V linear power regulator that provides the +3.3 V
supply to operate the RCM3600. Figure D-1 shows the power-supply circuit.
Figure D-1. RCM3600 Power Supply
The input voltage should be 5 V ± 0.25 V DC. An RCM3600 with no loading at the outputs
typically draws 60 mA when operating at 22.1 MHz. Take care that any DC loading (for
example, sourcing digital outputs) does not increase the overall current to more than 190
mA to keep the +3.3 V linear regulator from overheating.
D.1.1 Battery-Backup Circuits
The RCM3600 does not have a battery, but there is provision for a customer-supplied bat-
tery to back up the data SRAM and keep the internal Rabbit 3000 real-time clock running.
Header J1, shown in Figure D-1, allows access to the external battery. This header makes
it possible to connect an external 3 V battery. This allows the SRAM and the internal Rab-
bit 3000 real-time clock to retain data with the RCM3600 powered down.
LINEAR POWER REGULATOR
POWER
IN
J1
10 µF
LM1117
U7
+3.3 V
3
1
2
38
39
40
10 µF
VIN
37
VBAT_EXT
External
Battery