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This fault flag can be reset to '0' by reading back the Flags1 Register (0x0A), or by setting HWEN to '0', or by
setting the SW RESET bit to a '1', or by removing power to the AW3643.
NTC THERMISTOR INPUT (TORCH/TEMP)
The TORCH/TEMP pin, when set to TEMP mode, serves as a threshold detector and bias source for negative
temperature coefficient (NTC) thermistors. When the voltage at TEMP goes below the programmed threshold,
bit[0] is set to a ‘1’, and the AW3643 is placed into standby mode. The NTC threshold voltage is adjustable
from 200 mV to 900 mV in 100-mV steps. The NTC bias current is set to 50µA. The NTC detection circuitry
can be enabled or disabled via the Enable Register. If enabled, the NTC block turns on and off during the start
and stop of a Flash/Torch event.
Additionally, the NTC input looks for an open NTC connection and a shorted NTC connection. If the NTC input
falls below 100 mV, the NTC short flag is set(bit[4] in the Flags2 Register), and the AW3643 is forced into
standby mode. If the NTC input rises above 2.3 V, the NTC Open flag is set(bit[3] in the Flags2 Register), and
the AW3643 is forced into standby mode. These fault detections can be individually disabled/enabled via the
NTC Open Fault Enable bit and the NTC Short Fault Enable bit in Temp register(0x09)
V
TRIP
V
SHORT
V
OPEN
Control
Logic
VIN
TORCH/
TEMP
I
NTC
R
NTC
Fig 51 Temp Detection Diagram
The AW3643 is not available for operation until Flags2 register is cleared. The three NTC fault flags can be
reset to '0' by reading back the Flags2 Register (0x0B), or by setting HWEN to '0', or by setting the SW
RESET bit to a '1', or by removing power to the AW3643.
UNDERVOLTAGE LOCKOUT (UVLO)
The AW3643 has an internal comparator that monitors the voltage at IN and forces the AW3643 into standby
if the input voltage drops to 2.5 V. If the UVLO monitor threshold is tripped, the UVLO flag bit is set in the
Flags1 Register (0x0A). If the input voltage rises above 2.5 V, the AW3643 is not available for operation until
there is an I
2
C read of the Flags1 Register (0x0A). Upon a read, the Flags1 register is cleared, and normal
operation can resume if the input voltage is greater than 2.5 V.
VOUT SHORT FAULT
The Output Short Fault flag reads back a '1' if the device is active in Flash or Torch mode and the boost output
experiences a short condition. VOUT short condition occurs if the voltage at OUT goes below 2.3V (typ.) while
the device is in Torch or Flash mode. There is a deglitch time of 2.048ms before the VOUT Short flag is valid.
The mode bits are cleared upon an the VOUT short fault. The AW3643 is not available for operation until
VOUT Fault flags is cleared. The VOUT Short Faults can be reset to '0' by reading back the Flags1 Register
(0x0A), or by setting HWEN to '0', or by setting the SW RESET bit to a '1', or by removing power to the
AW3643.
