Datasheet

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LTC4446

4446f

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

High Voltage High Side/

Low Side N-Channel

MOSFET Driver

The LTC

4446 is a high frequency high voltage gate driver

that drives two N-channel MOSFETs in a DC/DC converter

with supply voltages up to 100V. The powerful driver ca-

pability reduces switching losses in MOSFETs with high

gate capacitance. The LTC4446’s pull-up for the top gate

driver has a peak output current of 2.5A and its pull-down

has an output impedance of 1.2Ω. The pull-up for the bot-

tom gate driver has a peak output current of 3A and the

pull-down has an output impedance of 0.55Ω.

The LTC4446 is conﬁ gured for two supply-independent

inputs. The high side input logic signal is internally

level-shifted to the bootstrapped supply, which may

function at up to 114V above ground.

The LTC4446 contains undervoltage lockout circuits that

disable the external MOSFETs when activated.

The LTC4446 is available in the thermally enhanced 8-lead

MSOP package.

The LTC4446 does not have adaptive shoot-through pro-

tection. For similar drivers with adaptive shoot-through

protection, please refer to the chart below.

PARAMETER LTC4446 LTC4444 LTC4444-5

Shoot-Through Protection No Yes Yes

Absolute Max TS 100V 100V 100V

MOSFET Gate Drive 7.2V to 13.5V 7.2V to 13.5V 4.5V to 13.5V

6.6V 6.6V 4V

–

6.15V 6.15V 3.55V

Bootstrap Supply Voltage Up to 114V

Wide V

Voltage: 7.2V to 13.5V

2.5A Peak Top Gate Pull-Up Current

3A Peak Bottom Gate Pull-Up Current

1.2Ω Top Gate Driver Pull-Down

0.55Ω Bottom Gate Driver Pull-Down

5ns Top Gate Fall Time Driving 1nF Load

8ns Top Gate Rise Time Driving 1nF Load

3ns Bottom Gate Fall Time Driving 1nF Load

6ns Bottom Gate Rise Time Driving 1nF Load

Drives Both High and Low Side N-Channel MOSFETs

Undervoltage Lockout

Thermally Enhanced 8-Pin MSOP Package

Distributed Power Architectures

Automotive Power Supplies

High Density Power Modules

Telecommunication Systems

Two Switch Forward Converter LTC4446 Driving a 1000pF Capacitive Load

L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

Protected by U.S. Patents including 6677210.

BOOST

36V TO 72V

(100V ABS MAX)

GND

SECONDARY

CIRCUIT

•

TINP

LTC4446

PWM2

(FROM CONTROLLER IC)

PWM1

(FROM CONTROLLER IC)

7.2V TO 13.5V

BINP

4446 TA01a

•

BINP

5V/DIV

10V/DIV

TINP

5V/DIV

TG-TS

10V/DIV

20ns/DIV

4446 TA01b

Summary of content (12 pages)

PAGE 1
LTC4446 High Voltage High Side/ Low Side N-Channel MOSFET Driver DESCRIPTION FEATURES n n n n n n n n n n n n n Bootstrap Supply Voltage Up to 114V Wide VCC Voltage: 7.2V to 13.5V 2.5A Peak Top Gate Pull-Up Current 3A Peak Bottom Gate Pull-Up Current 1.2Ω Top Gate Driver Pull-Down 0.
PAGE 2
LTC4446 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) Supply Voltage VCC......................................................... –0.3V to 14V BOOST – TS ........................................... –0.3V to 14V TINP Voltage ................................................. –2V to 14V BINP Voltage ................................................. –2V to 14V BOOST Voltage ........................................ –0.3V to 114V TS Voltage...................................................
PAGE 3
LTC4446 ELECTRICAL CHARACTERISTICS The l denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VCC = VBOOST = 12V, VTS = GND = 0V, unless otherwise noted.
PAGE 4
LTC4446 TYPICAL PERFORMANCE CHARACTERISTICS Boost Supply Current vs Temperature TINP = 0V BINP = 12V 200 150 100 VOL(TG) 120 100 80 VOL(BG) 60 40 TA = 25°C ITG(BG) = 100mA BOOST = VCC TS = GND 20 50 TINP = BINP = 0V 3.1 8 12 11 10 SUPPLY VOLTAGE (V) 9 TG OR BG INPUT THRESHOLD (V) 2.7 2.6 2.5 2.4 VIL(TG,BG) 2.3 2.2 VCC = BOOST = 12V 2.9 TS = GND VIH(TG,BG) 2.8 2.7 2.6 2.5 2.4 VIL(TG,BG) 2.3 2.2 2.1 2.1 7 8 11 10 9 12 SUPPLY VOLTAGE (V) 13 2.
PAGE 5
LTC4446 TYPICAL PERFORMANCE CHARACTERISTICS 60 tr(TG) 50 tr(BG) 40 30 tf(TG) 20 5 6 3 4 7 8 LOAD CAPACITANCE (nF) 2.8 2.6 IPU(TG) 2.4 2.2 9 2.0 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 10 4445 G13 30 26 24 tPHL(TG) 22 37 TA = 25°C BOOST = VCC TS = GND tPLH(TG) 1.8 BOOST-TS = 12V 1.6 1.4 1.2 BOOST-TS = 7V RDS(TG) BOOST-TS = 14V 1.0 VCC = 12V 0.8 VCC = 7V 0.6 0.4 0.
PAGE 6
LTC4446 PIN FUNCTIONS TINP (Pin 1): High Side Input Signal. Input referenced to GND. This input controls the high side driver output (TG). BINP (Pin 2): Low Side Input Signal. This input controls the low side driver output (BG). VCC (Pin 3): Supply. This pin powers input buffers, logic and the low side gate driver output directly and the high side gate driver output through an external diode connected between this pin and BOOST (Pin 6).
PAGE 7
LTC4446 OPERATION Overview LTC4446 BOOST The LTC4446 receives ground-referenced, low voltage digital input signals 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 switching node (TS).
PAGE 8
LTC4446 OPERATION both the high side and low side MOSFETs conducting, signiﬁcant cross-conduction current will ﬂow through the MOSFETs from VIN to ground and will cause substantial power loss. A similar effect occurs on TG due to the CGS and CGD capacitances of the high side MOSFET. The powerful output driver of the LTC4446 reduces the switching losses of the power MOSFET, which increase with transition time.
PAGE 9
LTC4446 APPLICATIONS INFORMATION Unlike a pure capacitive load, a power MOSFET’s gate capacitance seen by the driver output varies with its VGS voltage level during switching. A MOSFET’s capacitive load power dissipation can be calculated using its gate charge, QG. The QG value corresponding to the MOSFET’s VGS value (VCC in this case) can be readily obtained from the manufacturer’s QG vs VGS curves.
PAGE 10
12V 1μF 220pF 150Ω 20k 1/4W D2 A 1 4 9 0.47μF 11 2 C 9 220pF 8 180pF 5.1k 1 L2 150nH 21 B 20 9 C ISNS 4 33k 6.19k 5 6 1M 23 D 17 68nF 8.25k 22 MMBT3904 CT SPRG RLEB FB GND PGND 24 13 19 8 0.22μF 15 C3 68μF 20V 16 + 7 D11 3 330pF 4 SS COMP CS 5VREF 750Ω 200k ISNS 22Ω D4 2.2nF 6 8 2 4 2 4 D8 D7 330Ω 5 C4 2.2nF 250V 8 MOC207 5 9 2 1 6 CSE+ VH 1.5k 5 D12 5.1V 3 11 8 3 2.7k 6 5 Q4 12 14 15 Q2 16 VOUT VOUT –VOUT 2.
PAGE 11
LTC4446 PACKAGE DESCRIPTION MS8E Package 8-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1662 Rev D) BOTTOM VIEW OF EXPOSED PAD OPTION 2.06 ± 0.102 (.081 ± .004) 1 5.23 (.206) MIN 1.83 ± 0.102 (.072 ± .004) 0.889 ± 0.127 (.035 ± .005) 2.794 ± 0.102 (.110 ± .004) 2.083 ± 0.102 3.20 – 3.45 (.082 ± .004) (.126 – .136) 8 0.42 ± 0.038 (.0165 ± .0015) TYP 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.65 (.0256) BSC 8 7 6 5 0.52 (.0205) REF RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 3.
PAGE 12
LTC4446 TYPICAL APPLICATION LTC4446 Fast Turn-On/Turn-Off DC Switch 12V BZX84C12L 12V 0.01μF BAS21 100V 3 15k 200Ω 4.7k 100k BAS21 MMBT2369 4.7nF VIN 0V TO 100V 6 0.33μF VCC BOOST 7 TG TINP LTC4446 2 8 TS BINP 1 BG GND 9 BAS21 3.