4117047
Rev 2.2
December 18, 2015
19
Product Technical Specification
Detailed Interface Specifications
2.1.4.
Power Input (VBATT)
An external power supply uses the VBATT pins to:
Supply the AirPrime HL8518, HL8528 and HL8529 modules.
Directly supply the RF components.
It is essential to keep the voltage ripple to a minimum at this connection to avoid any
phase error or spectrum modulation degradation.
An inadequate power supply can significantly affect RF performance (TX power,
modulation spectrum, EMC performance, spurious emission, frequency error, etc.).
Provide reference voltage VGPIO (through internal regulators) for the baseband signals.
When the AirPrime HL8518, HL8528 and HL8529 modules are supplied with a battery, the total
impedance (b prote PCB) should be such that the supply will be >= 3.2 V during GSM
burst mode operation drawing a maximum peak current of 2.2 A for 577 µs (one slot) or 1154 µs (two
slots) TX.
2.2. Ground Connection
The AirPrime HL8518, HL8528 and HL8529 modules shielding case is the grounding. The ground
must be connected on the motherboard through a complete layer on the PCB.
The ground connection is made by soldering the LGA ground pins and rectangular ground pad to the
ground plane of the application board.
2.3. Decoupling of Power Supply Signals
The ETSI standard defines specific requirements for phase error and spectrum modulation. Both are
mandatory and can be affected by the choice of power supply filtering. It is highly recommended to
provide multiple capacitor values to solve an eventual Amplitude and Phase Modulation issue.
AirPrime HL8518, HL8528 and HL8529 modules already here embedded decoupling capacitors on
the VBATT lines, but additional external decoupling may be required.
EMI/RFI issues – Add a capacitor (10pF~33pF) close to the VBATT pins.
TDMA noise (217 Hz) – Place a low ESR decoupling capacitors (at least 100 µF) as close to
the module as possible to reduce noise.
Figure 4.
Power Supply Requirements
