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Appendix D provides information on the current requirements
of the RCM3700, 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 RCM3700 is connected via header
J1. The RCM3700 has an onboard +3.3 V linear power regulator that provides the +3.3 V
supply to operate the microprocessor-related circuitry of the RCM3700, but not the Ether-
net circuit, which requires + 5 V. Figure D-1 shows the power-supply circuit.
J1
VBAT_EXT
37
External
Battery
38
VIN
39
40
The RCM3700 requires a regulated 4.75 V to 5.25 V DC power source. An RCM3700 with
no loading at the outputs operating at 22.1 MHz typically draws 100 mA.
CAUTION: Be sure that the input to pin 39 on header J1 is connected to a regulated 5 V
supply. The regulated 5 V supply is required for the Ethernet circuitry, which is not
protected against overvoltage conditions.
RabbitCore RCM3700 User's Manual
A
PPENDIX
+5 V
Figure D-1. RCM3700 Power Supply
D. P
OWER
LINEAR POWER REGULATOR
LM1117
U7
2
3
1
10 µF
S
UPPLY
+3.3 V
10 µF
158
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