AMY-6M - Hardware Integration Manual
UBX-17021971 – R07
Design-in
Page 9 of 57
u-blox 6 supports use of an external DC/DC converter for improved power efficiency supplying V_DCDC and
eventually the RF section. The DCDC_EN signal allows shutting down this external DC/DC converter when
V_DCDC is not needed. If the DCDC_EN signal shall be used, VDD_IO must be supplied independently of the
DC/DC converter, i.e. these voltages must be supplied even if the DC/DC converter is disabled.
2.1.1.2
Base-band I/O supply voltage
The digital I/Os of the base-band part are supplied with VDD_IO from the host system. The wide range of
VDD_IO allows seamless interfacing to standard logic voltage levels.
VDD_IO must be supplied in order for the system to boot.
2.1.1.3
Base-band core voltages
The core voltages VDD_B and VDD_C core are generated separately to enable main supply VDD_C switch off
while the back-up domain VDD_B remains alive. The core voltages are generated by means of internal LDOs. The
input voltage range of the LDOs is wide and allows the use of several types of batteries.
2.1.1.4
Backup power supply
A backup battery can be connected to V_BCKP to supply the RTC and backup RAM in case of power failure at
the main battery for backup domain (VDD_IO). An internal switch supplies the internal VDD_B power domain in
case VDD_IO drops below the specified minimum value. VDD_IO will supply the VDD_B power domain if a
sufficiently high input voltage is detected. See Figure 3 below and see also section 2.1.1.6.
Figure 3: Supply of Backup Domain (VDD_B)
Limit V_BCKP and VDD_IO to 3.6 V.
2.1.1.5
RF supply voltages
The RF unit is supplied through the VDD_RF pin. This supply voltage can optionally be generated internally with
an LDO from the VDD_3V input. If the supply voltage is 1.8 V, then the VDD_3V must be shorted to the VDD_RF
pin, so that the internal LDO is shorted and there is no voltage drop.
Depending on the application, the RF supply voltage can be supplied from 3 different sources:
1.
From the V_DCDC node of the baseband power supply, taking advantage of the optional DC/DC
converter.
2.
From the VDD_IO node, in cases where the Main Battery voltage and/or V_DCDC are lower than the
minimum RF supply voltage.
3.
From a source independent of the baseband power management pins, e.g. the Main Battery node or a
totally independent voltage source.
In all 3 cases, the connections to VDD_3V and VDD_RF must be made according to the supply voltage range that
is actually supplied.
The RF supply voltage shall be free of noise and low frequency modulations.
There are two other LDOs in the RF unit providing improved supply rejection at very low dropout voltage for the
noise sensitive parts of the RF-circuits.
Insert a ferrite bead (FB1) to isolate the RF supply from digital noise.
