User`s guide

4-20 Intel
®
StrongARM
®
SA-1110 Microprocessor Development Board User’s Guide
Hardware Considerations
Note: The nine-pin RS232 cable connected to the Base Station serial port (J10) on the SA-1110
Development Board cannot be connected at the same time as the UART1 connector on the
SA-1111 Development Module. Failure to do so will corrupt the data on the UART1.
4.10 Power System
The SA-1110 development system has a unique, highly efficient and cost effective battery power
system.
4.10.1 Power System Design Benefits
The SA-1110 Development Platform provides the following benefits:
• Requires only a single cell Li-ion 3.6 V battery
• Greater then 90% efficiency on 3.3 V, 1.5 Vcore, and radio power rails in operating mode
• Greater then 90% efficiency on 3.3V rail in sleep mode
• Supports high power, high efficiency radio power rail for radio modules requiring either two
cell Li-ion batteries providing 7.2 V power or a single cell Li-ion battery providing 3.6 V
power
• Control of pulse width modulation (PWM) or pulse frequency modulation (PFM) and power
switching synchronization modes of main switching regulators
• Very clean power rails for audio and LCD systems
• Allows charging from AC power adapter or USB power input using a Maxim MAX846*
Li-ion charge controller
• Provides battery temperature monitoring
• Provides battery voltage and charger voltage monitoring
• Provides automatic battery lockout to prevent over-discharge and possible battery damage
• Provides low battery interrupt to SA-1110 processor
• Provides power switches for Compact Flash socket, audio subsystem and LCD display
subsystems
4.10.2 Power System Design
There are two main power rails in any SA-1110 design; are the 3.3 V main power and the
1.5 V core power. The 3.3 V rail must be on all the time to support sleep mode and preserve
SDRAM contents and system timer. In addition, a medium power 5 V rail is needed for the LCD as
well as a 7.6 V (two Li-ion cell equivalent) high power rail for the CDMA radio module.
As shown in Figure 4-1, the battery charge and discharge rates are quoted in relative terms related
to the rated capacity of the battery. As an example, a 1000 mA hour battery may be discharged at a
2 C rate where C is the rated battery current or 1000 mA in this example. A 0.2 C rate would be
200 mA for a 1000mAh battery. A Li-ion battery with a 100% charge starts at a terminal voltage of
4. 1 V and quickly discharges to about 3.6 V where it remains for most of the discharge cycle.
Toward the end of the discharge cycle the Li-ion terminal voltage falls rapidly from 3.6 V to 2.7 V
where the discharge must be stopped or battery damage (loss of capacity) may result. Two Li-ion