LM3S5956-IQR80-C1 Datasheet, PDF (294/1144 Pages) Texas Instruments – Stellaris® LM3S5956 Microcontroller

Hibernation Module
NRND: Not recommended for new designs.
Figure 6-3. Using a Dedicated Oscillator as the Hibernation Clock Source with VDD3ON Mode
Input
Voltage
Regulator
Stellaris® Microcontroller
IN OUT
Clock
Source
(f_{EXT_OSC})
N.C.
VDD
XOSC0
XOSC1
Open drain
external wake
up circuit
HIB
WAKE
R_PU
GND
VBAT
3V
Battery
6.3.3
6.3.4
Note: R_PU = Pull-up resistor is 1 MΩ
System Implementation
Several different system configurations are possible when using the Hibernation module:
■ Using a single battery source, where the battery provides both V_DD and V_BAT.
■ Using the VDD3ON mode, where V_DD continues to be powered in hibernation, allowing the GPIO
pins to retain their states, as shown in Figure 6-3 on page 294. In this mode, V_DDC is powered off
internally.
■ Using separate sources for V_DD and V_BAT, as shown in Figure 6-2 on page 293.
■ Using a regulator to provide both V_DD and V_BAT with a switch enabled by HIB to remove V_DD
during hibernation.
Adding external capacitance to the V_BAT supply reduces the accuracy of the low-battery measurement
and should be avoided if possible. The diagrams referenced in this section only show the connection
to the Hibernation pins and not to the full system.
If the application does not require the use of the Hibernation module, refer to “Connections for
Unused Signals” on page 1065. In this situation, the HIB bit in the Run Mode Clock Gating Control
Register 0 (RCGC0) register must be cleared, disabling the system clock to the Hibernation module
and Hibernation module registers are not accessible.
Battery Management
Important: System-level factors may affect the accuracy of the low battery detect circuit. The
designer should consider battery type, discharge characteristics, and a test load during
battery voltage measurements.
The Hibernation module can be independently powered by a battery or an auxiliary power source
using the VBAT pin. The module can monitor the voltage level of the battery and detect when the
voltage drops below V_LOWBAT. The module can also be configured so that it does not go into Hibernate
mode if the battery voltage drops below this threshold. Battery voltage is not measured while in
Hibernate mode.
294
October 06, 2012
Texas Instruments-Production Data