Datasheet

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LTC4442/LTC4442-1

4442fb

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

High Speed Synchronous

N-Channel MOSFET Drivers

The LTC

4442 is a high frequency gate driver designed

to drive two N-channel MOSFETs in a synchronous buck

DC/DC converter topology. The powerful driver capabil-

ity reduces switching losses in MOSFETs with high gate

capacitance.

The LTC4442 features a separate supply for the input

logic to match the signal swing of the controller IC. If the

input signal is not being driven, the LTC4442 activates a

shutdown mode that turns off both external MOSFETs.

The input logic signal is internally level-shifted to the

bootstrapped supply, which may function at up to 42V

above ground.

The LTC4442 contains undervoltage lockout circuits on

both the driver and logic supplies that turn off the external

MOSFETs when an undervoltage condition is present.

The LTC4442 and LTC4442-1 have different undervoltage

lockout thresholds to accommodate a wide variety of ap-

plications. An adaptive shoot-through protection feature is

also built-in to prevent power loss resulting from MOSFET

cross-conduction current.

The LTC4442/LTC4442-1 are available in the thermally

enhanced 8-lead MSOP package.

Synchronous Buck Converter Driver

■

Wide V

Range: 6V to 9.5V

■

38V Maximum Input Supply Voltage

■

Adaptive Shoot-Through Protection

■

2.4A Peak Pull-Up Current

■

5A Peak Pull-Down Current

■

8ns TG Fall Time Driving 3000pF Load

■

12ns TG Rise Time Driving 3000pF Load

■

Separate Supply to Match PWM Controller

■

Drives Dual N-Channel MOSFETs

■

Undervoltage Lockout

■

Thermally Enhanced MSOP Package

■

Distributed Power Architectures

■

High Density Power Modules

LTC4442 Driving 3000pF Capacitive Loads

BOOST

32V

GND

LOGIC

LTC4442

BGPWM

OUT

4442 TA01a

INPUT (IN)

5V/DIV

BOTTOM

GATE (BG)

5V/DIV

TOP GATE

(TG-TS)

5V/DIV

10ns/DIV

4442 TA01b

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

Summary of content (14 pages)

PAGE 1
LTC4442/LTC4442-1 High Speed Synchronous N-Channel MOSFET Drivers FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTION The LTC®4442 is a high frequency gate driver designed to drive two N-channel MOSFETs in a synchronous buck DC/DC converter topology. The powerful driver capability reduces switching losses in MOSFETs with high gate capacitance. Wide VCC Range: 6V to 9.5V 38V Maximum Input Supply Voltage Adaptive Shoot-Through Protection 2.
PAGE 2
LTC4442/LTC4442-1 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) Supply Voltage VCC......................................................... –0.3V to 10V VLOGIC .................................................... –0.3V to 10V BOOST – TS ........................................... –0.3V to 10V IN Voltage .................................................. –0.3V to 10V BOOST Voltage .......................................... –0.3V to 42V TS Voltage.....................................................
PAGE 3
LTC4442/LTC4442-1 ELECTRICAL CHARACTERISTICS The ● denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VCC = VBOOST = 7V, VTS = GND = 0V, VLOGIC = 5V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS UVLO Undervoltage Lockout Threshold VCC Rising (LTC4442) VCC Falling (LTC4442) Hysteresis (LTC4442) ● ● 2.75 2.60 3.20 3.04 160 3.65 3.
PAGE 4
LTC4442/LTC4442-1 TYPICAL PERFORMANCE CHARACTERISTICS Input Thresholds for VLOGIC = 3.3V vs Temperature 5 3.0 INPUT THRESHOLD (V) VIL(BG) VIH(BG) 1 4 VIL(TG) 1.5 VIL(BG) 1.0 VIH(BG) 7 6 5 8 VLOGIC SUPPLY (V ) 0 –40 10 9 –10 20 50 80 TEMPERATURE (°C) 4442 G01 0.3 0.2 0.1 0 3 4 7 6 5 8 VLOGIC SUPPLY (V) 10 9 VLOGIC UVLO THRESHOLD (V) SUPPLY CURRENT (mA) 0.5 IBOOST 0.3 IVLOGIC 0.8 0.30 VLOGIC = 5V 0.25 0.20 VLOGIC = 3.3V 0.15 0.10 0.7 0.6 0.5 0.4 IVCC 0.3 IBOOST 0.2 0.
PAGE 5
LTC4442/LTC4442-1 TYPICAL PERFORMANCE CHARACTERISTICS Undervoltage Lockout Threshold Hysteresis vs Temperature Switching Supply Current vs Input Frequency 4 800 700 600 500 400 300 LTC4442 VCC UVLO 200 100 0 –40 VLOGIC UVLO –10 20 80 50 TEMPERATURE (°C) 3 IVCC 2 IBOOST 1 0 110 IVLOGIC 0 200k 600k 400k FREQUENCY (Hz) 800k 4442 G10 tPLH(BG) tPHL(TG) 15 tPHL(BG) 10 NO LOAD VLOGIC = 5V BOOST-TS = VCC tPLH(TG) 25 tPLH(BG) 20 tPHL(TG) 15 tPHL(BG) 10 7 8 9 6 VLOGIC SUPPLY VOLTAGE (V) 5 8
PAGE 6
LTC4442/LTC4442-1 PIN FUNCTIONS TG (Pin 1): High Side Gate Driver Output (Top Gate). This pin swings between TS and BOOST. TS (Pin 2): High Side MOSFET Source Connection (Top Source). VLOGIC (Pin 6): Logic Supply. This pin powers the input buffer and logic. Connect this pin to the power supply of the controller that is driving IN (Pin 5) to match input thresholds or to VCC (Pin 7) to simplify PCB routing. GND (Pin 4, Exposed Pad Pin 9): Chip Ground.
PAGE 7
LTC4442/LTC4442-1 BLOCK DIAGRAM 7 VCC UNDERVOLTAGE LOCKOUT BOOST 6 VLOGIC TG LEVEL SHIFTER UNDERVOLTAGE LOCKOUT TS INTERNAL SUPPLY 1 2 SHOOTTHROUGH PROTECTION 7k 5 8 VCC THREE-STATE INPUT BUFFER IN BG 3 7k 4 GND 9 GND 4442 BD TIMING DIAGRAM IN TG BG VIL(TG) VIL(BG) 90% 10% 90% 4442 TD 10% tr(TG) tpLH(TG) tf(BG) tpHL(BG) tr(BG) tpLH(BG) tf(TG) tpHL(TG) 4442fb 7
PAGE 8
LTC4442/LTC4442-1 OPERATION Overview The LTC4442 receives a ground-referenced, low voltage digital input signal to drive two N-channel power MOSFETs in a synchronous buck power supply conﬁguration. The gate of the low side MOSFET is driven either to VCC or GND, depending on the state of the input. Similarly, the gate of the high side MOSFET is driven to either BOOST or TS by a supply bootstrapped off of the switch node (TS).
PAGE 9
LTC4442/LTC4442-1 OPERATION eliminating cross-conduction current from ﬂowing from the VIN supply through the MOSFETs to ground during a switch transition. Output Stage A simpliﬁed version of the LTC4442’s output stage is shown in Figure 2. The pull-up device on both the BG and TG outputs is an NPN bipolar junction transistor (Q1 and Q2). The BG and TG outputs are pulled up to within an NPN VBE (~0.7V) of their positive rails (VCC and BOOST, respectively).
PAGE 10
LTC4442/LTC4442-1 APPLICATIONS INFORMATION Power Dissipation To ensure proper operation and long-term reliability, the LTC4442 must not operate beyond its maximum temperature rating.
PAGE 11
LTC4442/LTC4442-1 APPLICATIONS INFORMATION To obtain the optimum performance from the LTC4442: A. Mount the bypass capacitors as close as possible between the VLOGIC and GND pins, the VCC and GND pins, and the BOOST and TS pins. The leads should be shortened as much as possible to reduce lead inductance. B. Use a low inductance, low impedance ground plane to reduce any ground drop and stray capacitance.
PAGE 12
LTC4442/LTC4442-1 PACKAGE DESCRIPTION MS8E Package 8-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1662 Rev E) BOTTOM VIEW OF EXPOSED PAD OPTION 2.06 p 0.102 (.081 p .004) 1 0.889 p 0.127 (.035 p .005) 2.794 p 0.102 (.110 p .004) 0.29 REF 1.83 p 0.102 (.072 p .004) 0.05 REF 5.23 (.206) MIN DETAIL “B” CORNER TAIL IS PART OF DETAIL “B” THE LEADFRAME FEATURE. FOR REFERENCE ONLY NO MEASUREMENT PURPOSE 2.083 p 0.102 3.20 – 3.45 (.082 p .004) (.126 – .136) 8 0.42 p 0.038 (.0165 p .
PAGE 13
LTC4442/LTC4442-1 REVISION HISTORY (Revision history begins at Rev B) REV DATE DESCRIPTION B 4/10 Updated Pin Conﬁguration PAGE NUMBER 2 Updated GND (Pin 4) in Pin Functions 6 Updated Related Parts 14 4442fb Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use.
PAGE 14
LTC4442/LTC4442-1 TYPICAL APPLICATION LTC7510/LTC4442-1 12V to 1.5V/30A Digital Step-Down DC/DC Converter with PMBus Serial Interface 7V VDRIVE 12V 5V R1 SDATA PMBus INTERFACE SCLK LTC7510 VD25 C2 BOOST R2 + PWRGD OUTEN C4 C1 C3 GND PWM MULTIPHASE INTERFACE C5 0.22μF VD33 SMB_AL_N POWER MANAGEMENT INTERFACE D2 CMDSH3 V12SEN VCC TG VLOGIC LTC4442-1 VCC TS IN 1μF SYNC_IN RCM SYNC_OUT BG GND M1 RJK0305 ×2 M2 RJK0301 ×2 L1 0.