LV8731V
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23
Auto Reset Type
In the automatic reset mode, when the output current
exceeds the detection current level, the output waveform
changes to the switching waveform.
As with the latch system, when the output short−circuited
state is detected, the short−circuit protection circuit is
activated. When the operation of the short−circuit detection
circuit exceeds the timer latch time (Tcem) described later,
the output is changed over to the standby mode and is reset
to the ON mode again in 2 ms (typ). In this event, if the over
current mode still continues, the switching mode described
above is repeated until the over current mode is canceled.
Unusual Condition Warning Output Pins (EMO, MONI)
The LV8731V is provided with the EMO pin which
notifies the CPU of an unusual condition if the protection
circuit operates by detecting an unusual condition of the IC.
This pin is of the open−drain output type and when an
unusual condition is detected, the EMO output is placed in
the ON (EMO = Low) state.
In the DC motor driver mode (DM = High), the MONI pin
also functions as a warning output pin.
The functions of the EMO pin and MONI pin change as
shown below depending on the state of the DM pin.
When the DM is low (STM mode) :
− EMO: Unusual condition warning output pin
− MONI: Excitation initial position detection monitoring
When the DM is high (DCM) mode) :
− EMO: Channel 1 warning output pin
− MONI: Channel 2 warning output pin
Furthermore, the EMO (MONI) pin is placed in the ON
state when one of the following conditions occurs.
1. Shorting−to−power, shorting−to−ground, or
shorting−to−load occurs at the output pin and the
output short−circuit protection circuit is activated
2. The IC junction temperature rises and the thermal
protection circuit is activated
Unusual Condition DM = L (STM Mode) DM = H (DCM Mode)
EMO MONI EMO MONI
Channel 1 Short−circuit Detected ON − ON −
Channel 2 Short−circuit Detected ON − − ON
Overheating Condition Detected ON − ON ON
Timer Latch Time (Tcem)
The time taken for the output to be set to OFF when the
output has been short−circuited can be set using capacitor
Ccem, connected between the CEM pin and GND. The value
of capacitor Ccem is determined by the formula given
below.
Timer latch : Tcem
Tcem ≈ Ccem × Vtcem / Icem [sec]
Vtcem: Comparator threshold voltage, typ 1 V
Icem: CEM pin charge current, typ 10 μA
