SE868-V3 Product User Guide
1VV0301205 r4 – 2016-01-20
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights Reserved.
Page 37 of 76
Mod. 0805 2015-02 Rev.4
9.4.
Power Supply
9.4.1.
Voltage Supply Design
The DC voltage supply (including regulators, capacitors, etc.) must be designed to insure that
the power is maintained within the below specifications.
9.4.2.
1.8 V Supply Voltage
Unlike some previous GNSS receiver modules, the SE868-V3 requires a single always-on 1.8
V supply. Rather than having a “split” power supply design of main and backup, the module
manages all of its power modes internally. The module will power up into the state determined
by the ON-OFF pin (High: RUN; Low: HIBERNATE).
The current state of the SE868-V3 can be determined by monitoring the “SYSTEM-ON” signal.
See
section 9.4.4 ON-OFF (input) and SYSTEM-ON (output).
If the 1.8 volt DC supply is removed from the module (regardless of power state) it will lose
current RTC time and the contents of the internal SRAM. To execute an orderly shutdown, first
place the module into the HIBERNATE state, then remove power. To prevent improper startup,
keep the power removed for approximately 10 seconds to reliably clear the SRAM contents.
The module monitors the 1.8 volt supply and issues an internal hardware reset if the supply
drops below 1.7 volts. This reset protects the memory from accidental writes during a power
down condition
.
The reset forces the module into a low power state.
To prevent the reset, the 1.8 volt supply must be regulated to be within ±50 mV of nominal
voltage (including load regulation and power supply noise and ripple). Noise and ripple outside
of these limits can affect GNSS sensitivity and also risk tripping the internal voltage supervisors,
thereby shutting down the module unexpectedly. Regulators with very good load regulation are
strongly recommended along with adequate power supply filtering to prevent power supply
glitches as the module transitions between power states.
The power supply voltage, noise and ripple must be between 1.75V and 1.85V for all
frequencies. To help meet these requirements, a separate LDO for the module is suggested.
9.4.3.
DC Power Requirements
Name
Min
Typ
Max
Units
V18
1.75
1.8
1.85
V
Max ripple: 54 mV (0 to 3 MHz), 15 mV (> 3 MHz)
Table 9-4 DC Supply Voltage