41110555
Rev 1.0
November 01, 2017
40
Product Technical Specification
Design Guidelines
5.4. Power Supply Design
The AirPrime HL77xx module 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 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.
Power Supply
VBATT/VBATT_PA
D404
0.5 pF
D405
C404
1.5 m
F
+
+
C405
150 µF
C407
100 n
F
Figure 11.
Voltage Limiter Example
5.5. Power On Connection Examples
Refer to the following figures for PWR_ON_N connection examples using a switch and an open
collector transistor.
PWR_ON
X
GND
Switch
1
2
3
Figure 12.
PWR_ON_N Connection Example with Switch
PWR_ON
GND
From application
MCU GPIO control
T1
Rohm DTC144EE
Figure 13.
PWR_ON_N Connection Example with an Open Collector Transistor
