TD340 데이터 시트보기 (PDF) - STMicroelectronics
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TD340 Datasheet PDF : 21 Pages
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TD340
Reversed battery active protection
In full H-bridge configuration, there is a risk in case of power voltage reversal due to the intrinsic diodes
inside the MOS. A passive protection solution is to wire a diode between the H-bridge and the power
supply. Disadvantages are voltage drop and power dissipation.
The TD340 provides support for reversed battery active protection.
An oscillator OSC output is available to allow proper command of a 5th MOS connected upside down.
The MOS must have low threshold voltage because the oscillator output swing is about 6.5V.
In normal conditions, the MOS intrinsic diode supplies power to the driver at startup. When the TD340 is
started, the OSC output enables the MOS to switch on, providing lower voltage drop and lower power
dissipation.
In case of reversed battery, the 5th MOS remains off, and no dangerous voltages can reach the driver nor
the power MOS.
The OSC oscillator can only supply a few mA. It must be loaded with a large impedance, typically 100pF
and 680k.
Figure 5 : Reversed Battery Active Protection Principle
Normal Conditions
VBATT
Osc Vbatt
Vbatt+6V
~Vbatt
1
2
3
TD340 4
2
M
3
GND
REVERSED BATTERY
5
Driver is not supplied
GND
MOSFET 5
REMAINS
OFF
Osc Vbatt
1
2
2
M
3
TD340 4
3
VBATT
ALL MOSFETS AND DRIVER ARE PROTECTED
UVLO and OVLO protections
The TD340 includes protections again overvoltage and undervoltage conditions.
Overvoltage is dangerous for the MOS and for the load due to possible excessive currents and power
dissipation.
Undervoltage is dangerous because MOS driving is no more reliable. MOS could be in linear mode with
high ohmic dissipation.
TD340 Under Voltage LockOut and Over Voltage LockOut features protect the system from no
operational power voltage. UVLO and OVLO thresholds are 6.2V and 20V. Hysteresis provides reliable
behavior near the thresholds.
During UVLO and OVLO, MOS are switched off (TD340 in disable state).
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