User`s guide

4-26 Intel
®
StrongARM
®
SA-1110 Microprocessor Development Board User’s Guide
Hardware Considerations
4.11.2.4 Radio Power
The SA-1110 Development Board supports CDMA or GSM radio module daughter boards. The
CDMA board electro-mechanical interface is supported on the SA-1110 Development Board radio
connector. The GSM radio module is supported with the addition of a small adaptor board that
provides a smart card slot and connector type conversion.
Note: The GSM adapter is not available in Phase 4.
The CDMA power requirements are matched to a two cell Li-ion battery that must be capable of
supplying up to 850 mA (worst case) during maximum power transmission.
The GSM power requirements are matched to a single cell Li-ion battery with a maximum current
of up to 2.5 A at a 12.5% duty cycle. The 0.33 F supercap used in the virtual backup battery design
also assists the main battery in meeting this very high current pulse demand.
The GSM power requirements are easily met by providing a connection to the single Li-ion main
battery.
The CDMA requirements are for a nominal 7.2 V two cell Li-ion supply. The discharge curves for
a two cell Li-ion battery run from 8.2 V fully charged, down to 5.4 V at the end of charge. A simple
solution was to use the high power MAX1705 boost output, which is designed to be adjustable
from 2.5 V to 5.5 V. Setting the MAX1705 boost output to 5.5 V allows powering the CDMA
module which requires a minimum of 5.4 V input. The current requirements of the CDMA module
are a maximum of 850 ma, which matches the maximum performance of the MAX1705.
Figure 4-2. Linear Boost Bootstrap Power System
A7297-01
MAX
1705
LDO
3.3 V
LDO
5.0 V
0.33 F
SuperCap
MAX
1602
5.5 V Radio Power
or
3.5 V During Sleep
Li-ion
4.1 V to
2.7 V
5.0 V
LCD
Power
3.3 V Main
1.5 V Core
SA_PWR_EN
BATT LOCKOUT
track
off
LDO
3.2 V