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BQ77307
SLUSF60 – DECEMBER 2023
The REGOUT LDO can be programmed to either remain disabled or power up automatically whenever the
device exits SHUTDOWN mode, depending on OTP configuration. The LDO output voltage can be programmed
to 1.8 V, 2.5 V, 3.0 V, 3.3 V, or 5.0 V by modifying configuration settings. When the REGOUT LDO is disabled
and the device is in NORMAL mode, its output is pulled to VSS with an internal resistance of approximately 2.5
kΩ. If the LDO is configured based on OTP settings to be powered, then at each later power-up the device will
autonomously load the OTP settings and enable the LDO as configured, without requiring communications first.
The BQ77307 is designed to operate properly with a die temperature up to 110°C, therefore the system design
must avoid drawing excessive current from the REGOUT LDO if it could result in the die temperature exceeding
this level. For example, with a stack voltage of 22.5 V, and REGOUT programmed to an output voltage of 2.5
V, the device will dissipate approximately 400 mW when supplying 20 mA of load current. The package thermal
impedance can be used to calculate the resulting die temperature based on the maximum ambient temperature
expected. If this exceeds the device's specified temperature range, the load current may need to be limited in the
system.
The BQ77307 includes a die temperature monitor which detects if the die temperature exceeds approximately
120°C. If this occurs, the REGOUT LDO is disabled, and depending on the configuration setting, the device will
also enter SHUTDOWN mode. If the REGOUT LDO is disabled due to overtemperature (but the device is not
shut down) and the die temperature reduces below the threshold, the REGOUT LDO will automatically power on
again.
7.4.10 Standalone Versus Host Interface
The BQ77307 can be configured to operate in a completely standalone mode, without any host processor
in the system, or together with a host processor. If in standalone mode, the device can monitor conditions,
control FETs based on threshold settings, and recover FETs when conditions allow, all without requiring any
interaction with an external processor. If a host processor is present, the device can still be configured to operate
fully autonomously, while the host processor can read status information and exercise control as desired.
Alternatively, the device can be configured for manual host control, such that the device can monitor and provide
a flag when a protection alert or fault has occurred, but will rely on the host to disable FETs. Using the device
in standalone mode requires that all settings are programmed into the OTP by TI. This is only available for
cases involving a significant shipment volume. Please contact your TI sales representative for information on this
option.
The BQ77307 can also be entirely configured by a host processor writing all settings to the device's internal
registers across the serial communications interface, without requiring any OTP programming. Using this
approach, settings must be reloaded from the host each time the device is reset or enters SHUTDOWN mode
and is restarted.
7.4.11 ALERT Pin Operation
The BQ77307 includes functionality to generate an alarm signal at the ALERT pin, which can be used as
an interrupt to a host processor. The ALERT pin is an open-drain pin which will be pulled low by the device
whenever an alarm signal is generated. The alarm function includes a programmable mask, to allow the
customer to decide which flags or events can trigger an alarm. The selected alarm flags remain latched until the
host processor reads their status and clears the triggered alarm bits. The alarm mask can be changed during
field operation, to mask or unmask individual flags from generating an alarm signal. The device also provides
the unlatched, instantaneous value of each flag, in addition to the latched version. See the
Reference Manual
for more details on this function.
7.4.12 Low Frequency Oscillator
The low frequency oscillator (LFO) in the BQ77307 operates continuously while in NORMAL mode. The LFO
runs at approximately 32.768 kHz in NORMAL mode. The LFO is trimmed during manufacturing to meet the
specified accuracy across temperatures.
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