Datasheet

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December 2008 Rev 1 1/16

L6743D

High 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

Description

L6743D 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.

SO8

Table 1. Device summary

Order codes Package Packing

L6743D

SO8

Tube

L6743DTR Tape and reel

www.st.com

Summary of content (16 pages)

PAGE 1
L6743D High 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 SO8 Combined with ST PWM controllers, the driver allows implementing complete volta
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Contents L6743D Contents 1 2 3 4 Typical application circuit and block diagram . . . . . . . . . . . . . . . . . . . . 3 1.1 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pins description and connection diagrams . . . . . . . . . . . . . . . . . . . . . . 4 2.1 Pin description . . . . . . . . . . . . . . . . . . . . . . .
PAGE 3
L6743D 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 CDEC VIN = 5V to 12V VCC BOOT EN Input L6743D CHF PWM Input PWM EN GND Vout L PHASE COUT LS LGATE NC* CBULK HS UGATE NC* L6743D Reference Schematic 1.2 Block diagram Figure 2.
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Pins description and connection diagrams 2 Pins description and connection diagrams Figure 3. Pins connection (Top view) BOOT PWM EN VCC 2.1 1 2 3 4 8 L6743D 7 6 5 UGATE PHASE GND LGATE Pin description Table 2. Pin # 1 2 4/16 L6743D Pins descriptions Name Function BOOT high-side driver supply. This pin supplies the high-side floating driver. Connect through a RBOOT - CBOOT capacitor to the PHASE pin. Internally connected to the cathode of the integrated bootstrap diode. See Section 4.
PAGE 5
L6743D 2.2 Pins description and connection diagrams Thermal data Table 3. Symbol Thermal data Parameter Value Unit RTHJA Thermal resistance junction to ambient (Device soldered on 2s2p, 67 mm x 69 mm board) 85 °C/W TMAX Maximum junction temperature 150 °C TSTG Storage temperature range 0 to 150 °C TJ Junction temperature range 0 to 125 °C 1.
PAGE 6
Electrical specifications L6743D 3 Electrical specifications 3.1 Absolute maximum ratings Table 4. Absolute maximum ratings Symbol Parameter Value Unit -0.3 to 15 V 41 15 V VCC,VPVCC to GND VBOOT, VUGATE to GND to PHASE VPHASE to GND -8 to 26 V VLGATE to GND -0.3 to VCC + 0.3 V VPWM, VEN to GND -0.3 to 7 V VCC,VPVCC to GND -0.3 to 15 V 3.2 Electrical characteristics Table 5. Electrical characteristics (VCC = 12 V±15 %, Tj = 0 °C to 70 °C unless otherwise specified).
PAGE 7
L6743D Table 5. Symbol Electrical specifications Electrical characteristics (continued) (VCC = 12 V±15 %, Tj = 0 °C to 70 °C unless otherwise specified). Parameter Test conditions Min. Typ. Max. Unit 2.3 2.8 Ω Gate drivers RHIHS HS source resistance BOOT - PHASE = 12 V; 100 mA IUGATE HS source current (1) BOOT - PHASE = 12 V; CUGATE to PHASE = 3.3 nF 2 RLOHS HS sink resistance BOOT - PHASE = 12 V; 100 mA 2 2.5 Ω RHILS LS source resistance 100 mA 1.3 1.
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Device description and operation 4 L6743D 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.
PAGE 9
L6743D 4.1 Device description and operation High-impedance (HiZ) management The driver is able to manage high-impedance state by keeping all MOSFETs in off state in two different ways. ● If the EN signal is pulled low, the device will keep all MOSFETs OFF careless of the PWM status. ● When EN is asserted, if the PWM signal remains in the HiZ window for a time longer than the hold-off time, the device detects the HiZ condition so turning off all the MOSFETs.
PAGE 10
Device description and operation L6743D To prevent bootstrap capacitor to extra-charge as a consequence of large negative spikes, an external series resistance RBOOT (in the range of few ohms) may be required in series to BOOT pin. Bootstrap capacitor needs to be designed in order to show a negligible discharge due to the high-side MOSFET turn-on. In fact it must give a stable voltage supply to the high-side driver during the MOSFET turn-on also minimizing the power dissipated by the embedded Boot Diode.
PAGE 11
L6743D Device description and operation Referring to Figure 6, classical MOSFET driver can be represented by a push-pull output stage with two different MOSFETs: P-MOSFET to drive the external gate high and NMOSFET to drive the external gate low (with their own RdsON: Rhi_HS, Rlo_HS, Rhi_LS, Rlo_LS).
PAGE 12
Device description and operation L6743D The use of multi-layer printed circuit board is recommended. Small signal components and connections to critical nodes of the application as well as bypass capacitors for the device supply are also important. Locate the bypass capacitor (VCC, PVCC and BOOT capacitors) close to the device with the shortest possible loop and use wide copper traces to minimize parasitic inductance.
PAGE 13
L6743D 5 Package mechanical data Package mechanical data In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK® specifications, grade definitions and product status are available at: www.st.com. ECOPACK® is an ST trademark.
PAGE 14
Package mechanical data Table 6. L6743D SO8 mechanical data Mm Inch Dim. Min. Typ. Max. Min. Typ. Max. A 1.35 1.75 0.053 0.069 A1 0.10 0.25 0.004 0.010 A2 1.10 1.65 0.043 0.065 B 0.33 0.51 0.013 0.020 C 0.19 0.25 0.007 0.010 4.80 5.00 0.189 0.197 3.80 4.00 0.15 0.157 D (1) E e 1.27 0.050 H 5.80 6.20 0.228 0.244 h 0.25 0.50 0.010 0.020 L 0.40 1.27 0.016 0.050 k 0° (min.), 8° (max.) ddd 0.10 0.004 1.
PAGE 15
L6743D 6 Revision history Revision history Table 7.
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L6743D Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale.