User's Manual

LISA-U1/LISA-H1 series - System Integration Manual

3G.G2-HW-10002-2 Advance Information System description

Page 31 of 116

V_INT can only be used as an output; don’t connect any external regulator on V_INT. If not used, this

pin should be left unconnected.

The V_INT digital interfaces supply output is mainly used to:

 Pull-up DDC (I

C) interface signals (see section 1.10 for more details)

 Pull-up SIM detection signal (see section 1.8 for more details)

 Indicate when the module is switched on and the RESET_N (external reset input pin) is not forced to the low

level

1.6 System functions

1.6.1 Module power on

The module power on sequence is initiated in one of 3 ways:

 Rising edge on the VCC pin to a valid voltage for module supply

 Falling edge on the PWR_ON pin

 Rising edge on the RESET_N pin

 RTC alarm

Name

Description

Remarks

PWR_ON

Power on input

PWR_ON pin has high input impedance.

Do not keep floating in noisy environment: external pull-up

required.

Table 10: Power on pin

The PWR_ON pin ESD rating is 1 kV (contact discharge). A higher protection level could be required if

the line is externally accessible on the application board. A higher protection level can be achieved

mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) on the line connected to this

pin.

1.6.1.1 Rising edge on VCC

When a supply is connected to VCC pins, the module supply supervision circuit controls the subsequent

activation of the power up state machines: the module is switched on when the voltage rises up to the VCC

operating range minimum limit (3.4 V) starting from a voltage value lower than 2.25 V (See LISA-U1/LISA-H1

series Data Sheet [1]).

The voltage at the VCC pins must ramp from 2.5 V to 3.2 V within 1 ms to switch on the module.

1.6.1.2 Falling edge on PWR_ON

The module power on sequence starts when a falling edge is forced on the PWR_ON input pin. After applying a

falling edge, it is suggested to hold a low level on the PWR_ON signal for at least 5 ms to properly switch on the

module.

The electrical characteristics of the PWR_ON input pin are different from the other digital I/O interfaces: the high

and the low logic levels have different operating ranges and the pin is tolerant to voltages up to the battery

voltage. The detailed electrical characteristics are described in the LISA-U1/LISA-H1 series Data Sheet [1].