TM4C123GH6ZRB Datasheet, PDF (512/1471 Pages) Texas Instruments – Tiva Microcontroller

Hibernation Module
■ Using a single battery source, where the battery provides both V_DD and V_BAT, as shown in Figure
7-2 on page 511.
■ 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 7-3 on page 511. In this mode, V_DDC is powered off
internally. The GPIO retention will be released when power is reapplied and the GPIOs will be
initialized to their default values.
■ Using separate sources for V_DD and V_BAT. In this mode, additional circuitry is required for system
start-up without a battery or with a depleted battery.
■ Using a regulator to provide both V_DD and V_BAT with a switch enabled by HIB to remove V_DD
during hibernation as shown in Figure 7-4 on page 512.
Figure 7-4. Using a Regulator for Both V_DD and V_BAT
Input
Voltage
Regulator
IN OUT
Switch
IN OUT
EN
C₁
X₁
C₂
Tiva™ Microcontroller
VDD
XOSC0
XOSC1
GNDX
Open drain
external wake
up circuit
HIB
WAKE
VBAT
R_PU
GND
7.3.4
Note: Some devices may not supply a GNDX signal. See “Signal Tables” on page 1368 for pins specific to
your device.
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 1417. In this situation, the HIB bit in the Run Mode Clock Gating Control
Register 0 (RCGC0) and the Hibernation Run Mode Clock Gating Control (RCGCHIB) registers
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 voltage threshold can be between 1.9 V and 2.5 V and is
configured using the VBATSEL field in the HIBCTL register. The module can also be configured so
that it does not go into Hibernate mode if the battery voltage drops below this threshold. In addition,
512
June 12, 2014
Texas Instruments-Production Data