User's Manual
HiLo3G-850 User Manual
04 March 2011 - Page 22 / 36
The resistor R depends on the charging current value provided by the battery manufacturer.
3.8.3 Backup Battery Technology
3.8.3.1 Capacitor Battery
These kinds of backup battery do not have the drawbacks of the Lithium Ion rechargeable battery.
As there are only capacitors:
• The maximum discharge current is generally bigger,
• There is no need to regulate the charging current.
Moreover, this kind of battery is available in the same kind of package than the Lithium Ion cell and fully compatible on a
mechanical perspective. The only disadvantage is that the capacity of this kind of battery is significantly smaller than
Manganese Silicon Lithium Ion battery. But for this kind of use (supply internal RTC when the main battery is removed),
the capacity is generally enough.
3.9 USB
There is one set USB_DP and USB_DN bi-directional differential USB data lines are compliant to the USB2.0
specification.
HiLo3G-850 is USB-Slave while customer application is USB-Master.
• Integrated high-speed USB PHY
• USB 2.0 specification-compliant as a peripheral
•The USB 2.0 specification requires hosts such as PCs to support all three USB speeds, namely low-speed (1.5 Mbps), full-
speed (12 Mbps) and high-speed (480 Mbps). The USB 2.0 specification allows peripherals to support any one or more of
these speeds.
• USB selective suspend and remote wake-up
The USB_DP and USB_DN signals are routed as a ~90 Ω differential pair. These signals must be routed side by side
and on the same layer and their trace length should match as close as possible.
2 pF capacitor is required to be installed between USB_DP and USB_DN and put close to the HiLo3G-850.
These signals have relatively fast edges, so they should be routed away from sensitive circuits and signals such as the
19.2 MHz TCXO, sleep XTAL, and RF. Therefore, do not route these signals on surface layers, it is preferred to be routed
in the inner layer routing sandwiched between power and ground.
4. Power Management
The host system shall supply 3.2V~4.4V to VBAT for powering the baseband, logics circuit and RF circuit.
4.1 Power Modes
Depending on the state of the HiLo3G-850, different power consumption modes can be identified.
Active mode (Active communication)
All systems on HiLo3G-850 are active. In this mode, the module is registered to the network and a voice/data call is
actively transmitting data.
Sleep mode (Active idle)
All systems on HiLo3G-850 are active including the USB bus. In this mode, the module is registered to the network but it
is idle/paging only. No voice/data call connection is established.
Fly mode
The processor is still active but the radio section is powered down. This mode can be controlled by sending an AT
command to the module.