User`s manual

Am186
TM
CC Microcontroller ISDN TA Reference Design Manual
2-12
Power Supply
This design requires only two voltages, +5 V and +3.3 V. The associated currents
and power estimates are included in Table 2-2. A 5-V, 500-mA, regulated, wall-
mount AC adapter is used to supply system power. The AC adapter is connected
to the system using a standard 5.5-mm barrel connector. A Raychem 750-mA fuse
is used to protect the circuit from any surge in current. To reset the fuse, unplug
the board and allow the fuse to cool. Most of the devices on the board require 5 V.
The 5 V is used directly from the regulated supply. The Am186CC microcontroller
and the inverter chip are the only 3.3-V devices on this board. The 3.3 V is obtained
from the LDO (Low Drop Out) linear regulator. The power supply and reset
schematics are shown in Figure 2-9.
Table 2-2. Current and Power Estimates for the ISDN TA
Volt (V) Device I
typ
(ma) I
max
(ma) P
typ
(mw) P
max
(mw)
3.3 Am186CC
controller
- 288 - 950
5 DRAM 65 99 650 990
5 Flash memory - 60 - 300
5 UART Xcvr 20 30 100 150
5 ISDN S/T Xcvr 31 38 155 190
5 ISDN U Xcvr 54 70 270 350
3.3 Total - 288 - 950
5 Total - 297 - 1980
about.book Page 12 Friday, December 18, 1998 9:41 AM