L6743D ,High current MOSFET driverApplicationsThe bootstrap diode is embedded saving the use ■ High current VRM / VRD for desktop / s ..
L6743DTR ,High current MOSFET driverBlock diagramVCCBOOTEN15kUGATEHSGNDPHASEL6743DVCCCONTROL LOGIC PWM PWM LGATELS& PROTECTIONSGND 3/16 ..
L6743Q ,High current MOSFET driverBlock diagramVCCBOOTEN15kUGATEHSGNDPHASEL6743VCCCONTROL LOGIC PWM PWM LGATELS& PROTECTIONSGND 3/17L ..
L6743QTR ,High current MOSFET driverApplicationsmanagement avoids high-side and low-side MOSFET to conduct simultaneously and, ■ High c ..
L6743TR , High current MOSFET driver
L6747ATR ,High current MOSFET driverblock diagramVCCBOOTEN70kUGATEHSPHASEL6747AVCCCONTROL LOGIC PWM PWM LGATELS& PROTECTIONS7kGNDDoc ID ..
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L6743D-L6743DTR
High current MOSFET driver
December 2008 Rev 1 1/16
L6743DHigh current MOSFET driver
Features Dual MOSFET driver for synchronous rectified
converters High driving current for fast external MOSFET
switching Integrated bootstrap diode High frequency operation Enable pin Adaptive dead-time management Flexible gate-drive: 5 V to 12 V compatible High-impedance (HiZ) management for output
stage shutdown Preliminary OV protection SO8 package
Applications High current VRM / VRD for desktop / server /
workstation CPUs High current and high efficiency DC / DC
converter
DescriptionL6743D is a flexible, high-frequency dual-driver
specifically designed to drive N-channel
MOSFETs connected in synchronous-rectified
buck topology.
Combined with ST PWM controllers, the driver
allows implementing complete voltage regulator
solutions for modern high-current CPUs and
DCDC conversion in general. L6743D embeds
high-current drivers for both high-side and low-
side MOSFETS. The device accepts flexible
power supply (5 V to 12 V) to optimize the gate-
drive voltage for high-side and low-side
maximizing the system efficiency.
The bootstrap diode is embedded saving the use
of external diodes. Anti shoot-through
management avoids high-side and low-side
MOSFET to conduct simultaneously and,
combined with adaptive dead-time control,
minimizes the LS body diode conduction time.
L6743D embeds preliminary OV protection: after
Vcc overcomes the UVLO and while the device is
in HiZ, the LS MOSFET is turned ON to protect
the load in case the output voltage overcomes a
warning threshold protecting the output against
HS failures.
The driver is available is SO8 package.
Table 1. Device summary
Contents L6743D2/16
Contents Typical application circuit and block diagram . . . . . . . . . . . . . . . . . . . . 31.1 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pins description and connection diagrams . . . . . . . . . . . . . . . . . . . . . . 42.1 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63.1 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Device description and operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.1 High-impedance (HiZ) management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.2 Preliminary OV protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.3 Internal BOOT diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.4 Power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.5 Layout guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
L6743D Typical application circuit and block diagram
3/16 Typical application circuit and block diagram
1.1 Application circuit
Figure 1. Typical application circuit
1.2 Block diagram
Figure 2. Block diagram
Pins description and connection diagrams L6743D
4/16 Pins description and connection diagrams
Figure 3. Pins connection (Top view)
2.1 Pin description
Table 2. Pins descriptions
L6743D Pins description and connection diagrams
5/16
2.2 Thermal data
Table 3. Thermal data
Electrical specifications L6743D
6/16
3 Electrical specifications
3.1 Absolute maximum ratings
Table 4. Absolute maximum ratings
3.2 Electrical characteristics
Table 5. Electrical characteristics
(VCC = 12 V±15 %, Tj = 0 °C to 70 °C unless otherwise specified).
L6743D Electrical specifications
7/16 Parameter(s) guaranteed by designed, not fully tested in production
Table 5. Electrical characteristics (continued)
(VCC = 12 V±15 %, Tj = 0 °C to 70 °C unless otherwise specified).
Device description and operation L6743D
8/16 Device description and operation
L6743D provides high-current driving control for both high-side and low-side N-channel
MOSFETS connected as step-down DC-DC converter driven by an external PWM signal.
The integrated high-current drivers allow using different types of power MOSFETs (also
multiple MOS to reduce the equivalent RDS(on)), maintaining fast switching transition.
The driver for the high-side MOSFET use BOOT pin for supply and PHASE pin for return.
The driver for the low-side MOSFET use the VCC pin for supply and PGND pin for return.
The driver embodies a anti-shoot-through and adaptive dead-time control to minimize low-
side body diode conduction time maintaining good efficiency saving the use of Schottky
diodes: when the high-side MOSFET turns off, the voltage on its source begins to fall; when
the voltage reaches about 2 V, the low-side MOSFET gate drive voltage is suddenly applied.
When the low-side MOSFET turns off, the voltage at LGATE pin is sensed. When it drops
below about 1 V, the high-side MOSFET gate drive voltage is suddenly applied. If the
current flowing in the inductor is negative, the source of high-side MOSFET will never drop. o allow the low-side MOSFET to turn-on even in this case, a watchdog controller is
enabled: if the source of the high-side MOSFET doesn't drop, the low-side MOSFET is
switched on so allowing the negative current of the inductor to recirculate. This mechanism
allows the system to regulate even if the current is negative.
Before VCC to overcome the UVLO threshold, L6743D keeps firmly-OFF both high-side and
low-side MOSFETS then, after the UVLO has been crossed, the EN and PWM inputs take
the control over driver’s operations. EN pin enables the driver: if low will keep all MOSFET
OFF (HiZ) regardless of the status of PWM. When EN is high, the PWM input takes the
control: if left floating, the internal resistor divider sets the HiZ State: both MOSFETS are
kept in the OFF state until PWM transition.
After UVLO crossing and while in HiZ, the preliminary-OV protection is activated: if the
voltage senses through the PHASE pin overcomes about 1.8 V, the low-side MOSFET is
latched ON in order to protect the load from dangerous over-voltage. The driver status is
reset from a PWM transition.
Driver power supply as well as power conversion input are flexible: 5 V and 12 V can be
chosen for high-side and low-side MOSFET voltage drive.
Figure 4. Timing diagram (EN = high)
