Vref As Input In Gr64002; Figure 7: Interface Circuit Implementation For Gs64 - Wavecom Gx64 Application Note

Figure 7: Interface circuit implementation for GS64

The level translator type used in Figure 7 can be either ST2378E from ST
Microelectronics, MAX3001E from Maxim, or any other applicable type.
shows a GS64 implementation, but the same figure can be used for a GR64001
solution if the 1.8V regulator is replaced with a 2.8V regulator.
VREF can furthermore be used by the application as an indicator whether the Wireless
CPU is powered on or not. An active high >1.65V indicates power on, while a low
<0.4V indicates power off.
If PON_H or ON/OFF are held active (high and low respectively) while VCC is slowly
increased from <2.7V to 3.3V, VREF will go active when VCC is at 3.050V, while the
SW starts executing when VCC is at 3.135V. This hysteresis is built-in to ensure that
the VREF is within specified levels when SW starts executing.
3.5.2

VREF as input in GR64002

In this variant of GR64 using VREF as an input offers the integrator a flexible interface
solution. The application should apply its logic interface voltage directly onto VREF as
long as it is between 1.8V and 5.0V. The application does not have to implement its
own level translation. It is all done inside the Wireless CPU.
Gx64 APPLICATION NOTE
Power Management
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Figure 7