ST L6741 User Manual
Features
■ Dual MOSFET driver for synchronous rectified
converters
■ High driving current for fast external MOSFET
switching
■ High frequency operation
■ Integrated bootstrap diode
■ Adaptive dead-time management
■ Flexible gate-drive: 5V to 12V compatible
■ High-impedance (HiZ) management for output
stage shutdown
■ Preliminary OV protection
■ SO-8 package
Applications
■ High current VRM / VRD for Desktop / Server /
Workstation CPUs
■ High current DC / DC converters
L6741
High current MOSFET driver
SO-8
Description
L6741 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. L6741 embeds high-current
drivers for both high-side and low-side
MOSFETS. The device accepts flexible power
supply (5V to 12V) 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.
L6741 embeds Preliminary OV Protection: after
Vcc overcomes the UVLO and while the device is
in HiZ, the Low-Side MOSFET is turned ON to
protect the load in case the output voltage
overcomes a warning threshold protecting the
load from High-Side MOSFET failures.
The driver is available is SOP8 package.
Table 1. Device summary
Order code Package Packaging
L6741 SO-8 Tube
L6741TR SO-8 Tape & Reel
August 2007 Rev 1 1/16
www.st.com
1
Contents L6741
Contents
1 Typical application circuit and block diagram . . . . . . . . . . . . . . . . . . . . 3
1.1 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Pins description and connection diagrams . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5 Device description and operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1 High-impedance (HiZ) management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.2 Preliminary OV protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.3 Internal BOOT diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.4 Gate driver voltage flexibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.5 Power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.6 Layout guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2/16
L6741 Typical application circuit and block diagram
1 Typical application circuit and block diagram
1.1 Application circuit
Figure 1. Typical application circuit
VCC = 5V to 12V
C
PWM Input
3
DEC
PWM
VCC
6
PVCC
BOOT
UGATE
7
2
C
1
HS
HF
VIN = 5V to 12V
C
BULK
4
GND
L6741 Reference Schematic
1.2 Block diagram
Figure 2. Block diagram
PVCC
VCC
PWM
PHASE
L6741
LGATE
8
5
L6741
CONTROL LOGIC
& PROTECTIONS
PWM
L
LS
CROSS CONDUCTION
ADAPTIVE ANTI
HS
VCC
LS
Vout
C
OUT
BOOT
UGATE
PHASE
LGATE
GND
3/16
Pins description and connection diagrams L6741
2 Pins description and connection diagrams
Figure 3. Pins connection (Top view)
2.1 Pin description
Table 2. Pins descriptions
Pin n Name Function
1UGATE
2BOOT
3PWM
4GND
High-side driver output.
Connect to High-Side MOSFET gate.
High-side driver supply. this pin supplies the high-side floating driver. Connect
through a R
Internally connected to the cathode of the integrated Bootstrap diode. See
Section 5.3 for guidance in designing the capacitor value.
Control input for the driver (5V compatible).
This pin controls the state of the driver and which external MOSFET have to be
turned-ON.
If left floating, it causes the driver to enter the High-Impedance (HiZ) state
which causes all mosfets to be OFF. See Section 5.1 for details about HiZ.
All internal references, logic and drivers are referenced to this pin. Connect to
the PCB ground plane.
UGATE
BOOT
PWM
GND
BOOT
1
2
3
4
- C
8
7
L6741
capacitor to the PHASE pin.
BOOT
6
5
PHASE
PVCC
VCC
LGATE
Low-side driver output.
5LGATE
6VCC
7 PVCC
8 PHASE
4/16
Connect directly to the Low-Side MOSFET gate. A small series resistor can be
useful to reduce dissipated power especially in high frequency applications.
Device and LS driver power supply. Connect to any voltage between 5V and
12V. Bypass with low-ESR MLCC capacitor to GND.
Integrated bootstrap diode anode supply.
Connect to any voltage between 5V and 12V to supply the HS driver
accordingly.
High-side driver return path. Connect to the high-side MOSFET source.
This pin is also monitored for the adaptive dead-time management and Pre-OV
protection.
L6741 Thermal data
3 Thermal data
Table 3. Thermal data
Symbol Parameter Value Unit
R
T
T
P
thJA
MAX
STG
T
J
TOT
Thermal resistance junction to ambient
(Device soldered on 2s2p PC Board - 67mm x 67mm)
Maximum junction temperature 150 °C
Storage temperature range 0 to 150 °C
Junction temperature range 0 to 125 °C
Maximum power dissipation at 25°C
(Device soldered on 2s2p PC Board)
4 Electrical specifications
4.1 Absolute maximum ratings
Table 4. Absolute maximum ratings
Symbol Parameter Value Unit
V
CC,VPVCC
, V
V
BOOT
V
PHASE
V
LGATE
V
PWM
V
CC,VPVCC
UGATE
to GND -0.3 to 15 V
to GND
to PHASE
to GND -8 to 26 V
to GND -0.3 to VCC + 0.3 V
to GND -0.3 to 7 V
to GND -0.3 to 15 V
85 °C/W
1.15 W
41
15
V
5/16
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