Open drain
external wake
up circuit
GND
C 2
C 1
X 1
VBAT
EN
Input
Voltage
Regulator
or Switch
XOSC1
XOSC0
VDD
HIB
WAKE
OUT
IN
GNDX
7LYDŒ 0LFURFRQWUROOHU
R
PU
Functional Description
481
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Hibernation Module
•
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 6-4. Using a Regulator for Both V
DD
and V
BAT
NOTE:
Some devices may not supply a GNDX signal. See 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, see . In this situation, the HIB bit in
the Hibernation Run Mode Clock Gating Control (RCGCHIB) register must be cleared, disabling the
system clock to the Hibernation module and Hibernation module registers are not accessible.
6.3.4 Battery Management
NOTE:
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, battery voltage is monitored
while in hibernation, and the microcontroller can be configured to wake from hibernation if the battery
voltage goes below the threshold using the BATWKEN bit in the HIBCTL register.
The Hibernation module is designed to detect a low-battery condition and set the LOWBAT bit of the
Hibernation Raw Interrupt Status (HIBRIS) register when this occurs. If the VABORT bit in the HIBCTL
register is also set, then the module is prevented from entering Hibernate mode when a low-battery is
detected. The module can also be configured to generate an interrupt for the low-battery condition (see
).