4117047
Rev 2.2
December 18, 2015
34
Product Technical Specification
Design Guidelines
3.5. Power Supply Design
The AirPrime HL8518, HL8528 and HL8529 modules should not be supplied with voltage over 4.5V
even temporarily or however briefly.
If the system’s main board power supply unit is unstable or if the system’s main board is supplied with
over 4.5V, even in the case of transient voltage presence on the circuit, the module’s power amplifier
may be severely damaged.
To avoid such issues, add a voltage limiter to the module’s power supply lines so that VBATT and
VBATT_PA signal pads will never receive a voltage surge over 4.5V. The voltage limiter can be as
simple as a Zener diode with decoupling capacitors as shown in the diagram below.
Figure 14. Voltage Limiter Example
3.6. ESD Guidelines for SIM Card
Decoupling capacitors must be added as close as possible to the SIM card connectors on UIM1_CLK,
UIM1_RST, UIM1_VCC and UIM1_DATA signals to avoid EMC issues and to pass the SIM card type
approval tests, according to the drawings below.
A typical schematic for hardware SIM detection is provided below.
Figure 15. EMC and ESD Components Close to the SIM
