FAN7093_12 Datasheet, PDF (8/14 Pages) Fairchild Semiconductor – High-Current PN Half-Bridge Driver

Protection Functions
The device provides several integrated protection
functions designed to prevent IC damage in fault
conditions. Fault conditions are considered as “outside”
the normal operating range. Protection functions are not
for continuous or repetitive operation, with the exception
of current-limit protection. In a fault condition, the
FAN7093 applies the highest slew rate possible,
independent of the connected slew rate resistor (R_SR).
Over-voltage, over-temperature, and over-current
situations are indicated by a fault current flag I_IS(LIM) at
the IS pin. The following describes the protection
functions in order of priority. Over-voltage protection
overrides all other protections.
Over-Voltage Protection (OVP)
To ensure a high immunity against over-voltage
conditions like load dump, the device turns off the low-
side MOSFET and turns on the high-side MOSFET
when the supply voltage exceeds the over-voltage
protection level V_OV(OFF). The control IC returns to
normal operation t_lock=140 µs (Typ.) after the supply
voltage decreases below the over-voltage lockout level,
V_OV(ON). In H-bridge configurations, this behavior leads to
freewheeling in the high side during over-voltage
condition. If the load current exceeds I_CP in over-voltage
lockout, the IC turns off the high-side driver and latches
this state. See Table 1, which shows the condition of the
IS pin flag. This state can be reset (if the conditions no
longer exist) when /INH goes from HIGH to LOW to
HIGH again.
Under-Voltage Protection (UVP)
To avoid uncontrolled motion; for example, a driven
motor at low voltages; the control IC turns off all
MOSFETS when the supply voltage drops below the
turn-off voltage, V_UV(OFF). The control IC resumes to
normal operation when the supply voltage rises above
the turn-on voltage V_UV(ON). Notice that the IS pin does
NOT flag this fault condition.
Over-Temperature Protection (OTP)
The FAN7093 is protected against over-temperature by
an integrated temperature sensor in the control IC.
Over-temperature protection turns off both output
stages. This state is latched until the device is reset by a
LOW signal with a minimum pulse length of t_reset at the
/INH pin, assuming the control IC temperature
decreased by at least the thermal hysteresis. Repetitive
use of the over-temperature protection decreases
product life.
Current Limitation
The current is measured in both MOSFETS. As soon as
the current reaches the limit I_CL, the low-side or high-
side MOSFET is deactivated and the other MOSFET
activated for t_CLS. During that time, changes at the IN pin
are ignored. The /INH pin can still be used to turn off
both MOSFETs. After t_CLS, the MOSFETS return to their
initial setting. The error signal at the IS pin is reset after
2 x t_CLS. Unintentional triggering of the current-limit
circuitry through short current spikes (e.g. inflicted by
EMI coming from a motor) is suppressed by an internal
filter. Reaction delay of the filter circuitry affects the
current limit level I_CL, depending on slew rate of the load
current dI/dt.
Figure 5. Current Limitation Timing Diagram
(Inductive Load)
In combination with a typical inductive load, such as a
motor, this results in a switched-mode current limitation.
This method of limiting current has the advantage of
greatly reduced power dissipation compared to driving
the MOSFET in linear mode. Therefore, it is possible to
use the current limitation for a short time without
exceeding the maximum allowed junction temperature
(e.g. for limiting the inrush current during motor startup).
However, regular use of the current limitation is only
allowed as long as the specified maximum junction
temperature is not exceeded. Exceeding this
temperature reduces the life of the device.
Short-Circuit Protection (SCP)
The device is short-circuit protected against:
 Output Shorted to Ground
 Output Shorted to Battery Voltage
 Short-Circuit between the Load Connections
The short-circuit protection is a combination of current
limit and over-temperature shutdown of the device.
© 2011 Fairchild Semiconductor Corporation
FAN7093 • Rev. 1.0.4
8
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