LM74670-Q1 [TI]

具有 70uA 栅极驱动器的 0.48V 至 42V、零 IQ 汽车理想二极管整流器控制器;


型号：	LM74670-Q1
厂家：	TEXAS INSTRUMENTS
描述：	具有 70uA 栅极驱动器的 0.48V 至 42V、零 IQ 汽车理想二极管整流器控制器栅极驱动控制器二极管驱动器
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中文：	中文翻译
下载：	下载PDF数据表文档文件

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LM74670-Q1

ZHCSGN3A –SEPTEMBER 2015–REVISED OCTOBER 2015

LM74670-Q1 零 I_Q智能二极管整流器控制器

1 特性

3 说明

•

符合 AEC-Q100 标准，其中包括以下内容：

LM74670-Q1 是一种控制器器件，可在交流发电机的

全桥或半桥整流器架构中与 N 通道 MOSFET 搭配使

用。它旨在驱动外部 MOSFET 以模拟理想二极管。此

方案独一无二的优势在于其并无接地基准，因此其具有

零 I_Q。采用全桥或半桥整流器和交流发电机的肖特基

二极管可以替换为 LM74670-Q1 解决方案，以避免正

向导电二极管损耗并使交流/直流转换器更加高效。

–

器件温度 1 级：-40℃ 至 +125℃ 的环境工作温

度范围

超出人体模型 (HBM) 静电放电 (ESD) 分类等级

器件充电器件模型 (CDM) ESD 分类等级 C4B

•

峰值输入交流电压：42V

零 I_Q

LM74670-Q1 控制器为外部 N 通道 MOSFET 提供栅

极驱动，并配有快速响应内部比较器，可使 MOSFET

栅极在反极性情况下放电。此器件支持频率高达

300Hz 的交流信号。

适用于外部 N 通道 MOSFET 的电荷泵栅极驱动器

与肖特基二极管相比，正向压降和功耗更低

能够处理频率高达 300Hz 的交流信号

2 应用

器件信息⁽¹⁾

•

交流整流器

器件型号

封装

VSSOP (8)

封装尺寸（标称值）

交流发电机

电动工具

LM74670-Q1

3.00mm x 5.00mm

(1) 如需了解所有可用封装，请参阅产品说明书末尾的可订购产品

附录。

反极性保护

智能二极管全桥整流器应用

智能二极管配置

VIN

VOUT

AC Input

GATE DRIVE GATE PULL DOWN

ANODE

CATHODE

LM74670

V_CAPH

V_CAPL

V_CAP

OUT

LOAD

An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. PRODUCTION DATA.

English Data Sheet: SNOSD08

LM74670-Q1

ZHCSGN3A –SEPTEMBER 2015–REVISED OCTOBER 2015

www.ti.com.cn

7.3 Feature Description .................................................. 7

7.4 Device Functional Modes........................................ 10

Application and Implementation ........................ 12

8.1 Typical Rectifier Application ................................... 12

8.2 Design Requirements.............................................. 16

Power Supply Recommendations...................... 17

特性.......................................................................... 1

应用.......................................................................... 1

说明.......................................................................... 1

修订历史记录 ........................................................... 2

Pin Configuration and Functions......................... 3

Specifications......................................................... 4

6.1 Absolute Maximum Ratings ...................................... 4

6.2 ESD Ratings.............................................................. 4

6.3 Recommended Operating Conditions....................... 4

6.4 Thermal Information ................................................. 4

6.5 Electrical Characteristics........................................... 4

6.6 Typical Characteristics.............................................. 6

Detailed Description .............................................. 7

7.1 Overview ................................................................... 7

7.2 Functional Block Diagram ......................................... 7

10 Layout................................................................... 17

10.1 Layout Guidelines ................................................. 17

10.2 Layout Example .................................................... 18

11 器件和文档支持 ..................................................... 19

11.1 社区资源................................................................ 19

11.2 商标....................................................................... 19

11.3 静电放电警告......................................................... 19

11.4 Glossary................................................................ 19

12 机械、封装和可订购信息....................................... 19

4 修订历史记录

注：之前版本的页码可能与当前版本有所不同。

Changes from Original (September 2015) to Revision A

Page

•

将“产品预览”更改为“生产数据”................................................................................................................................................ 1

LM74670-Q1

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ZHCSGN3A –SEPTEMBER 2015–REVISED OCTOBER 2015

5 Pin Configuration and Functions

DGK Package

8-Pin VSSOP

Top View

V_CAP

Cathode

Gate Pull Down

V_CAPH

LM74670-Q1

Gate Drive

Anode

Pin Functions

PIN NO.

NAME

I/O

DESCRIPTION

VcapL

Charge Pump Output, connect to an external charge pump capacitor

Gate Pull Down

Connect to the gate of the external MOSFET for fast turn OFF in the case of

reverse polarity

No connect. Leave floating or connect to Anode pin

Anode

Anode of the diode, connect to source of the external MOSFET

No connect. Leave floating or connect to gate drive pin

Gate Drive

VcapH

Cathode

Gate Drive output, Connect to the Gate of the external MOSFET

Charge Pump Output, connect to an external charge pump capacitor

Cathode of the diode, connect to Drain of the external MOSFET

LM74670-Q1

ZHCSGN3A –SEPTEMBER 2015–REVISED OCTOBER 2015

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6 Specifications

6.1 Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted)

(1)

MIN

-3

MAX

UNIT

(2) (3)

Cathode to Anode (For a 2ms time duration)

Cathode to Anode (Continuous)⁽³⁾

VcapH to VcapL

-3

-0.3

-40

-65

Anode to VcapL

Gate Drive, Gate Pull Down to VcapL

(4)

Ambient Temperature (TA-MAX)

125

150

°C

Case Temperature (TC-MAX)

Storage temperature range, T_stg

(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings

only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended

Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

(2) 42V continuous (and 45V transients for 2ms) absmax condition from Cathode to Anode. Suitable to use with TVS SMBJ28A and

SMBJ14A at the anode.

(3) Reverse voltage rating only. There is no positive voltage limitation for the LM74670-Q1 Anode terminal.

(4) The device performance is ensured over this Ambient Temperature range as long the Case Temperature does not exceed the MAX

value.

6.2 ESD Ratings

VALUE

±4000

±750

UNIT

Human body model (HBM), per AEC Q100-002⁽²⁾

Charged-device model (CDM), per AEC Q100-011

V_(ESD)

Electrostatic discharge⁽¹⁾

(1) AEC Q100-002 indicates that HBM stressing shall be in accordance with the ANSI/ESDA/JEDEC JS-001 specification.

(2) The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.

6.3 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)

MIN

NOM

MAX

UNIT

Cathode To Anode

Ambient Temperature (TA-MAX)

Case Temperature (TC-MAX)

-40

125

°C

6.4 Thermal Information

LM74670-Q1

THERMAL METRIC⁽¹⁾

DGK (VSSOP)

UNIT

8 PINS

181

R_θJA

R_θJC(top)

R_θJB

ψ_JT

Junction-to-ambient thermal resistance

Junction-to-case (top) thermal resistance

Junction-to-board thermal resistance

102

°C/W

Junction-to-top characterization parameter

Junction-to-board characterization parameter

ψ_JB

100

(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953

6.5 Electrical Characteristics

⁽¹⁾T_A= 25°C unless otherwise noted. Minimum and Maximum limits are specified through test, design, validation or statistical

correlation. Typical values represent the most likely parametric norm at T_A= 25°C and are provided for reference purpose

(1) Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which

operation of the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits

and associated test conditions, see the table of Electrical Characteristics.

LM74670-Q1

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ZHCSGN3A –SEPTEMBER 2015–REVISED OCTOBER 2015

Electrical Characteristics (continued)

⁽¹⁾T_A= 25°C unless otherwise noted. Minimum and Maximum limits are specified through test, design, validation or statistical

correlation. Typical values represent the most likely parametric norm at T_A= 25°C and are provided for reference purpose

only. V_{Anode-Cathode}= 0.55V for all tests.

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

V_{Anode to Cathode}

V_capThreshold

Minimum Startup Voltage across External MOSFET V_GS= 0V

External MOSFET's Body Diode

0.48

Charge Pump Capacitor Drive

Thresholds

Vcap Upper Threshold

Vcap Lower Threshold

V_{Gate to Anode}= 2V

6.3

5.15

I_{Gate up}

Gate Drive Pull up current

µA

I_{Gate down}

Gate Drive pull down current

during forward voltage

V_{Gate to Anode}= 4V

I_{Gate pull down}

I_Charge

Gate drive pull down current

when reverse voltage is sensed

V_{Gate Pull Down}= V_Anode+ 2V

V_{Anode to Cathode}= 0.55 V

V_cap= 6.6V

160

µA

Charging current for the charge

pump capacitor

I_Discharge

VCAP Current Consumption to

power the controller when

MOSFET is ON

0.95

T_Recovery

Time to shut off MOSFET when

V_{Anode to Cathode}= -20 mV

2.2

5⁽²⁾

µs

voltage is reversed (Equivalent to Cgate = 4 nF

diode reverse recovery time)

Duty Cycle

Iload = 3 A, T_A= 25°C

98%

92%

Iload = 3 A, T_A= 125°C

V_{Anode to Cathode}= -13.5 V

I_LKG

Reverse Leakage Current

Quiescent Current to GND

Current into Anode pin

110⁽²⁾

µA

I_Anode

Current into Anode pin when V_{Anode -}

_Cathode= 0.3V.

(2) Limit applies over the full Operating Temperature Range T_A= -40°C to +125°C.

30 mV

V_ANODE> V_CATHODE

V_CATHODE> V_ANODE

0 mV

-20 mV

tT_RECOVERY

V_GATE

0 V

Figure 1. Gate Shut Down Timing in the Event of Reverse Polarity

LM74670-Q1

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6.6 Typical Characteristics

300

0.465

0.46

V_Reverse = 13.5 V

V_Reverse = 37 V

250

200

150

100

0.455

0.45

0.445

0.44

0.435

-40

-20

100 120 140

-40

-20

100 120 140

Temperature (èC)

D001

D002

Figure 2. Reverse Leakage at Negative Voltages

Figure 3. Anode to Cathode Startup Voltage

3.25

6.5

6.25

VCAP H

VCAP L

2.75

2.5

2.25

5.75

5.5

5.25

-40

-20

100 120 140

-40

-20

100 120 140

Temperature (°C)

Temperature (èC)

D009

D003

Figure 4. Reverse Recovery Time (T_Recovery

)

Figure 5. VcapH and VcapL Voltage Threshold

100

-40èC

25èC

85èC

125èC

-40èC

25èC

85èC

125èC

-20

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Current (A)

D005

D004

Figure 6. Duty Cycle of the Output Voltage at Startup

Figure 7. Duty Cycle of the Output Voltage

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ZHCSGN3A –SEPTEMBER 2015–REVISED OCTOBER 2015

7 Detailed Description

7.1 Overview

Using N-Channel MOSFETs with controller ICs can be highly effective and more efficient substitutes of lossy

diodes in a bridge rectifier application. The LM74670-Q1 is designed to control a single N-Channel MOSFET in a

full or half bridge rectifier as replacement for diode. In a full bridge rectifier, each diode can be replaced by the

LM74670-Q1 and a MOSFET. Diodes used in bridge rectifiers cause high power losses associated with the

forward voltage drop of each diode. In each cycle of sinusoidal AC voltage, two diodes conduct at the same time.

Power losses during diode forward conduction increase as the output current increases. Diode rectification also

increases peak current for applications that require high value output capacitance due to charge and discharge

with the diode drop voltage. The ON state forward voltage loss in a MOSFET depends upon the R_DSONof the

MOSFET. The power losses become substantially lower than diodes for the equivalent current. This solution has

a small increase in complexity; however it eliminates the need for diode heatsinks and thermal management for

high power AC bridge rectifier applications.

The LM74670-Q1 is a zero Iq controller that is combined with an external N-channel MOSFET to replace each

diode in a bridge rectifier. The voltage across the MOSFET source and drain is constantly monitored by the

LM74670-Q1 Anode and Cathode pins. An internal charge pump is used to provide the GATE drive for the

external MOSFET. The forward conduction is through the MOSFET 98% of the time. The forward conduction is

through the MOSFET body diode for 2% of time when energy is stored in an external charge pump capacitor

Vcap Figure 9. This stored energy is used to drive the gate of MOSFET. The voltage drop and power losses

depend on the R_DSONof MOSFETs used to replace the rectifier diodes. The LM74670-Q1 has no ground

reference which makes it identical to a diode.

7.2 Functional Block Diagram

Input

Output

ANODE

GATE DRIVE GATE PULL DOWN

11.5 V

CATHODE

V_CAP

LOGIC

Reverse Batt

Shut Off

V_CAP

Charge

Pump

7.3 Feature Description

7.3.1 During T0

When power is initially applied, the load current (I_D) will flow through the body diode of the MOSFET and produce

a voltage drop (V_f) during T0 in Figure 8. This forward voltage drop (V_f) across the body diode of the MOSFET is

used to charge up the charge pump capacitor Vcap. During this time, the charge pump capacitor Vcap is

charged to a higher threshold of 6.3V (typical).

LM74670-Q1

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Feature Description (continued)

VOUT

Body Diode Voltage Drop

tT1t

FET is ON

V_GS

FET is OFF

0 V

Figure 8. Output Voltage and V_GSOperation at 1A Output Current

7.3.2 During T1

Once the voltage on the capacitor reaches a higher voltage level of 6.3V (typical), the charge pump is disabled

and the MOSFET turns ON. The energy stored in the capacitor is used to provide the gate drive for the MOSFET

(T1 in Figure 8). When the MOSFET is ON, it provides a low resistive path for the drain current to flow and

minimizes the power dissipation associated with forward conduction. The power losses during the MOSFET ON

state depend primarily on the R_DSONof the selected MOSFET and load current. At time when the capacitor

voltage reaches its lower threshold VcapL 5.15V (typical), the MOSFET gate turns OFF. The drain current I_Dwill

then begin to flow through the body diode of the MOSFET, causing the MOSFET body diode voltage drop to

appear across Anode and Cathode pins. The charge pump circuitry is re-activated and begins charging the Vcap.

The LM74670-Q1 operation keeps the MOSFET ON at approximately 98% duty cycle (typical) regardless of the

external charge pump capacitor value. This is the key factor to minimizing the power losses. The forward voltage

drop during this time is limited by the R_DSONof the MOSFET.

7.3.3 Pin Operation

7.3.3.1 Anode and Cathode Pins

The LM74670-Q1 Anode and Cathode pins are connected to the source and drain of the external MOSFET. The

current into the Anode pin is 30 µA (typical). When power is initially applied, the load current flows through the

body diode of the external MOSFET, the voltage across Anode and Cathode pins is equal to the forward diode

drop . The minimum value of diode voltage drop required to enable the charge pump circuitry is 0.48V. Once the

MOSFET is turned ON, the Anode and Cathode pins constantly sense the voltage difference across the

MOSFET to determine the magnitude and polarity of the voltage across it. When the MOSFET is on, the voltage

difference across Anode and Cathode pins depends on the R_DSONand load current. If voltage difference across

source and drain of the external MOSFET becomes negative, this is sensed as a fault condition by Anode and

Cathode pins and gate is turned off by Gate Pull Down pin as shown in Figure 1. The reverse voltage threshold

across Anode and Cathode to detect the fault condition is -20 mV. The consistent sensing of voltage polarity

across the MOSFET enables the LM74670-Q1 to provide a fast response to the power source failure and limit

the amount and duration of the reverse current flow.

7.3.3.2 VcapH and VcapL Pins

VcapH and VcapL are high and low voltage thresholds respectively that the LM74670-Q1 uses to detect when to

turn the charge pump circuitry ON and OFF. The capacitor charging and discharging time can be correlated to

the duty cycle of the MOSFET gate. Figure 9 shows the voltage behavior across the Vcap. During the time

period T0, the capacitor is storing energy from the charge pump. The MOSFET is turned off and current flow is

only through the body diode during this time period. The conduction though body diode of the MOSFET is for a

LM74670-Q1

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ZHCSGN3A –SEPTEMBER 2015–REVISED OCTOBER 2015

Feature Description (continued)

very small period of time (2% typical) which rules out the chances of overheating the MOSFET, regardless of the

output current. Once the capacitor voltage reaches its high threshold, the MOSFET is turned off and charge

pump circuity is deactivated until the Vcap reaches its low voltage threshold (T1). The voltage difference between

Vcap high and low threshold is typically 1.15V. The LM74670-Q1 charge pump has 46µA charging capability with

5-8MHz frequency.

V_CAP

1.1 V

V_CAP

VOUT

Body Diode Voltage Drop

tT1t

Figure 9. Vcap Charging and Discarding by the Charge Pump

The Vcap current consumption is 0.95µA (typical) to drive the gate. The MOSFET OFF time (T0) and ON time

(T1) can be calculated using the following expression

DT = C

(1)

Where:

•

C = Vcap Capacitance

dV = 1.15V

dI = 46 µA for charging

dI = 0.95 µA for discharging

Note: Temperature dependence of these parameters – The duty cycle is dependent on temperature since the

capacitance variation over temperature has a direct correlation to the MOSFET OFF and ON periods and the

frequency. If the capacitor varies 20% the periods and the frequency will also vary by 20% so it is recommended

to use a quality X7R/COG cap and not to place the cap in close proximity to high temperature devices. The

variation of the capacitor does not have a thermal impact in the application as the duty cycle does not change.

7.3.3.3 Gate Drive Pin

When the charge pump capacitor is charged to the high voltage level of 6.3V (typ), the Gate Drive pin provides a

67µA (typ) of drive current. When the charge pump capacitor reaches its lower voltage threshold of 5.15V (typ),

Gate is pulled down to the Anode voltage (Vin). During the positive cycle of AC sinusoid, the MOSFET gate is

turned ON by the LM74670-Q1 gate drive to ensure the forward conduction through the MOSFET.

7.3.3.4 Gate Pull Down Pin

The Gate Pull Down pin of the LM74670-Q1 is connected to the Gate Drive pin in a bridge rectifier application.

When the controller detects negative polarity during the negative cycle of AC sinusoidal, the Pull-Down quickly

discharges the MOSFET gate through a discharge transistor. This fast pull down reacts regardless of the Vcap

charge level. When the negative voltage across the Anode and Cathode pins due to reverse current reaches

-20mV (typical), the LM74670-Q1 immediately reacts and discharges the MOSFET gate capacitance as shown in

Figure 10 . The Gate voltage is pulled down to Anode voltage with 160mA pull down current when the negative

LM74670-Q1

ZHCSGN3A –SEPTEMBER 2015–REVISED OCTOBER 2015

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Feature Description (continued)

cycle of the AC input starts. . A MOSFET with 4nF of effective gate capacitance can be turned off by the

LM74670-Q1 within 2.2µs (typical). The fast turnoff time minimizes the reverse current flow from MOSFET drain

by opening the circuit. The reverse leakage current does not exceed 110µA for a constant 13.5V reverse voltage

across Anode and Cathode pins. The reverse leakage current for a Schottky diode is 15mA under the same

voltage and temperature conditions.

Figure 10. Gate Pull Down in the Event of Reverse Polarity

7.4 Device Functional Modes

The LM74670-Q1 operates in two modes:

•

Body Diode Conduction Mode

The LM74670-Q1 solution works like a conventional diode during this time with higher forward voltage drop.

The power dissipation during this time can be given as:

P_Dissipation= V

ì I

(

_ForwardDrop

) (

_{Drain Current}

)

(2)

However, the current only flows through the body diode while the MOSFET gate is being charged to V_GS(TH)

This conduction is only for 2% duty cycle, therefore it does not cause any thermal issues.

Cì(VcapH- VcapL)

Body Diode ON Time =

I_{Charge Current}

(3)

•

The MOSFET Conduction Mode

The MOSFET is turned on during this time and current flow is only through the MOSFET. The forward voltage

drop and power losses are limited by the R_DSONof the specific MOSFET used in the solution. The LM74670-

Q1 solution output is comprised of the MOSFET conduction mode for 98% of its duty cycle. This time period

is given by the following expression:

Cì(VcapH - VcapL)

MOSFET ON Time =

I_{Discharge Current}

(4)

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ZHCSGN3A –SEPTEMBER 2015–REVISED OCTOBER 2015

Device Functional Modes (continued)

7.4.1 Duty Cycle Calculation

The LM74670-Q1 has an operating duty cycle of 98% at 25 C̊ and >90% at 125 C̊ . The duty cycle doesn’t

depend on the Vcap capacitance value. However, the variation in capacitance value over temperature has direct

correlation to the switching frequency between the MOSFET and body diode. If the capacitance value decreases,

the charging and discharging time will also decrease, causing more frequent switching between body diode and

the MOSFET condition. The following expression can be used to calculate the duty cycle of the LM74670-Q1:

(MOSFET ON Time)

Duty Cycle (%) =

ì100

(MOSFET ON Time + Body Diode ON Time)

(5)

7.4.2 Startup Voltage

The LM74670-Q1 will not initiate the charge pump operation if a closed loop system is in standby mode or the

drain current is smaller than 1mA (typical). This is due to a minimum body diode voltage requirement of the

LM74670-Q1 controller. If the drain current is too small to produce a minimum voltage drop of 0.48V at 25 ͦC, the

charge pump circuitry will remain off and the MOSFET will act just like a diode. It is very important to know the

body diode voltage parameter of a MOSFET before implementing it into the Smart Diode solution. Some N-

channels MOSFETs have very low body diode voltage at higher temperature. This makes their drain current

requirement higher to achieve 0.48V across the body diode in order to initiate the LM74670-Q1 controller at

higher temperatures.

LM74670-Q1

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8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Typical Rectifier Application

The LM74670-Q1 can be used with appropriate N-channel MOSFET to replace a diode in a typical rectifier

application. The rectifier could be industrial for a 12/24AC supply or an automotive rectifier for a single phase or

three phase field winding controlled alternator. The schematic for a typical implementation is shown in Figure 11

to implement a full bridge rectifier. The same schematic can also be extended to six legs for a three phase

alternator rectification. Following considerations need to be made when selecting the appropriate MOSFET for

this application:

1. An input voltage of 24V AC can reach a 34V peak. The MOSFET selected should have a V_DSgreater than

this voltage.

2. The Continuous drain current of the MOSFET should be nearly 2.5X I_AVGto cover peak currents during

rectification.

3. The V_GS(TH)threshold voltage of the selected MOSFET should be ≤3V to ensure error-free operation.

+OUT

LM74670-Q1

V_CAP

V_CAPH

V_CAP

V_CAPH

1 µF

IN~

LM74670-Q1

V_CAP

V_CAPH

V_CAP

V_CAPH

1 µF

œOUT

Figure 11. Typical Full Bridge Rectifier Application

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Typical Rectifier Application (continued)

8.1.1 Design Requirements

For this design example, use the parameters listed in Table 1 as the input parameters

Table 1. Design Parameters

DESIGN PARAMETER

Input Voltage Range

Output Voltage

EXAMPLE VALUE

4 – 42V peak AC

rectified positive amplitude

Maximum Drain current of MOSFET

3V Max

Output current range

Threshold voltage of FET V_GS(TH)

Vcap value

1µF

8.1.2 Detailed Design Procedure

To begin the design process, determine the following:

8.1.2.1 Design Considerations

•

Input voltage range

Output current range

Body Diode forward voltage drop for the selected MOSFET

MOSFET Gate threshold voltage

8.1.2.2 Capacitor Selection

A ceramic capacitor should be placed between VcapL and VcapH. The capacitor acts as a holding tank to power

up the control circuitry when the MOSFET is on.

When the MOSFET is off, this capacitor is charged up to higher voltage threshold of ~6.3V. Once this voltage is

reached, the Gate Drive of LM74670-Q1 will provide drive for the external MOSFET. When the MOSFET is ON,

the voltage across its body diode is collapsed because the forward conduction is through the MOSFET. During

this time, the capacitor acts as a supply for the Gate Drive to keep the MOSFET ON.

The capacitor voltage will gradually decay when the MOSFET is ON. Once the capacitor voltage reaches a lower

voltage threshold of 5.15V, the MOSFET is turned off and the capacitor gets recharged again for the next cycle.

A capacitor value of 220nF to 2.2uF with X7R/COG characteristic and 16V rating or higher is recommended for

this application. A higher value capacitor sets longer MOSFET ON time and OFF time; however, the duty cycle

remains at ~98% for MOSFET ON time irrespective of capacitor value.

If the Vcap value is 1µF, the MOSFET ON time and OFF time can be calculated using Equation 1 :

MOSFET ON Time = (1µF x 1.15V)/0.95µA = 1.21 seconds

Body Diode ON Time = (1µF x 1.15V)/46µA = 25 miliseconds

(6)

(7)

The duty cycle can be calculated using Equation 5 :

Duty Cycle % = 1.21 sec / (1.21 sec + 0.025sec) = 98%

(8)

8.1.2.3 MOSFET Selection

The important MOSFET electrical parameters are the maximum continuous Drain current I_D, the maximum drain-

to-source voltage V_DS(MAX), the gate-to-source threshold voltage V_GS(TH)and the drain-to-source On resistance

R_DSON. The maximum continuous drain current, I_D, rating must exceed the maximum continuous load current.

The rating for the maximum current through the body diode, I_S, is typically rated the same as, or slightly higher

than the drain current, but body diode current only flows for a small period while the MOSFET gate is being

charged to V_GS(TH).The LM74670-Q1 can provide up to 5V V_GSto drive the external MOSFET, therefore the V_GS

threshold of the selected MOSFET must be ≤ 3V.

LM74670-Q1

ZHCSGN3A –SEPTEMBER 2015–REVISED OCTOBER 2015

www.ti.com.cn

The voltage across the MOSFET's body diode must be higher than 0.48V at low current. The body diode voltage

for MOFETS typically decreases as the ambient temperature increases. This will increase the source current

requirement to achieve the minimum body diode drain-to-source voltage for the charge pump to initiate. The

maximum drain-to-source voltage, V_DS(MAX), must be high enough to withstand the highest differential voltage

seen in the application. This would include any anticipated fault conditions. Although there are no positive V_DS

limitation. However, it is recommended to use MOSFETS with voltage rating up to 45V for automotive

applications, since the LM74670-Q1 has a reverse voltage limit of -45V. Table 2 shows the examples of

recommended MOSFETs to be used with the LM74670-Q1.

8.1.3 Application Curves

In the following plots, the input voltage is 20V AC. The output current is 5A for all frequencies.

V_IN(5 V/DIV)

V_GSof Q1 (5 V/DIV)

V_OUT(5 V/DIV)

Time (5 ms/DIV)

Figure 12. Response to 60Hz AC Input

V_IN(5 V/DIV)

V_GSof Q1 (5 V/DIV)

V_OUT(5 V/DIV)

Time (5 ms/DIV)

Figure 13. Response to 100Hz AC Input

LM74670-Q1

www.ti.com.cn

ZHCSGN3A –SEPTEMBER 2015–REVISED OCTOBER 2015

V_IN(5 V/DIV)

V_GSof Q1 (5 V/DIV)

V_OUT(5 V/DIV)

Time (2 ms/DIV)

Figure 14. Response to a 300Hz AC Input

LM74670-Q1

ZHCSGN3A –SEPTEMBER 2015–REVISED OCTOBER 2015

www.ti.com.cn

8.2 Design Requirements

NOTE

Startup voltage is the voltage drop is needed for the controller to turn ON. It directly

influences the Minimum output current at which the MOSFET turns ON.

Table 2. Recommended MOSFET Examples⁽¹⁾

Diode

Voltage

@ 2A at

Voltage Drain

Vgs

Threshold

(V)

Rdson

mΩ @ 4.5V

Part No

(V)

Current

Package; Footprint

Qual

Current at 25C

125C/175C

CSD17313Q2Q1

SQJ886EP

23.5

5.5

5.6

1.8

2.5

2.3

2.5

2.2

3.3

2.2

0.65

0.5

SON; 2 x 2

Auto

PowerPAK SO-8L; 5 x 6

SO-8; 5 x 6

Auto

SQ4184EY

0.5

Auto

Si4122DY

0.5

SO-8; 5 x 6

Auto

RS1G120MN

RS1G300GN

CSD18501Q5A

SQD40N06-14L

SQ4850EY

20.7

2.5

3.3

0.6

HSOP8; 5 x 6

Auto

0.5

HSOP8; 5 x 6

Auto

0.53

0.5

SON; 5 x 6

Industrial

Auto

TO-252; 6 x 10

SO-8; 5 x 6

0.55

0.53

0.48

0.55

0.50

Auto

CSD18532Q5B

IPG20N04S4L-07A

IPB057N06N

IPD50N04S4L

3.3

7.2

5.7

7.3

SON;5 x 6

Industrial

Auto

PG-TDSON-8-10; 5 x 6

PG-TO263-3; 10 x 15

PG-TO252-3-313; 6 x10

Auto

LFPAK56; Power-SO8

(SOT669); 5 x 6

BUK9Y3R5-40E

100

3.8

2.1

0.48

Auto

IRF7478PbF-1

SQJ422EP

IRL1004

4.3

6.5

2.2

2.5

0.55

0.50

0.60

0.65

SO-8; 5 x 6

Industrial

Auto

PowerPAK SO-8L; 5 x 6

TO-220AB

130

112

Auto

AUIRL7736

DirectFET®; 5 x 6

Auto

(1) The LM74670-Q1 solution is not limited to the MOSFETs included in this table. It only shows examples of compatible MOSFETs.

LM74670-Q1

www.ti.com.cn

ZHCSGN3A –SEPTEMBER 2015–REVISED OCTOBER 2015

9 Power Supply Recommendations

While testing the LM74670-Q1 solution, it is important to use low impedance power supply which allows current

sinking. If the power supply does not allow current sinking, it would prevent the current flow in the reverse

direction in the event of reverse polarity. The MOSFET gate won't get pulled down immediately due to the

absence of reverse current flow.

10 Layout

10.1 Layout Guidelines

•

The VIN terminal is recommended to have a low-ESR ceramic bypass-capacitor. The typical recommended

bypass capacitance is a 10-μF ceramic capacitor with a X5R or X7R dielectric.

•

The VIN terminal must be tied to the source of the MOSFET using a thick trace or polygon.

The Anode pin of the LM74670-Q1 is connected to the Source of the MOSFET for sensing.

The Cathode pin of the LM74670-Q1 is connected to the drain of the MOSFET for sensing.

The high current path of for this solution is through the MOSFET, therefor it is important to use thick traces for

source and drain of the MOSFET.

•

The charge pump capacitor Vcap must be kept away from the MOSFET to lower the thermal effects on the

capacitance value.

The Gate Drive and Gate pull down pins of the LM74670-Q1 must be connected to the MOSFET gate without

using vias.

Obtaining acceptable performance with alternate layout schemes is possible, however this layout has been

shown to produce good results and is intended as a guideline.

LM74670-Q1

ZHCSGN3A –SEPTEMBER 2015–REVISED OCTOBER 2015

www.ti.com.cn

10.2 Layout Example

1. VcapL

2. PullDown

3. NC

8. Cathode

7. VcapH

6. Gate Drive

5. NC

4. Anode

Figure 15. Layout Example

LM74670-Q1

www.ti.com.cn

ZHCSGN3A –SEPTEMBER 2015–REVISED OCTOBER 2015

11 器件和文档支持

11.1 社区资源

下列链接提供到 TI 社区资源的连接。链接的内容由各个分销商“按照原样”提供。这些内容并不构成 TI 技术规范，

并且不一定反映 TI 的观点；请参阅 TI 的《使用条款》。

TI E2E™ 在线社区 TI 的工程师对工程师 (E2E) 社区。此社区的创建目的在于促进工程师之间的协作。在

e2e.ti.com 中，您可以咨询问题、分享知识、拓展思路并与同行工程师一道帮助解决问题。

设计支持

TI 参考设计支持可帮助您快速查找有帮助的 E2E 论坛、设计支持工具以及技术支持的联系信息。

11.2 商标

E2E is a trademark of Texas Instruments.

All other trademarks are the property of their respective owners.

11.3 静电放电警告

这些装置包含有限的内置 ESD 保护。存储或装卸时，应将导线一起截短或将装置放置于导电泡棉中，以防止 MOS 门极遭受静电损

伤。

11.4 Glossary

SLYZ022 — TI Glossary.

This glossary lists and explains terms, acronyms, and definitions.

12 机械、封装和可订购信息

以下页面包括机械、封装和可订购信息。这些信息是指定器件的最新可用数据。这些数据发生变化时，我们可能不

会另行通知或修订此文档。如欲获取此产品说明书的浏览器版本，请参阅左侧的导航栏。

PACKAGE OPTION ADDENDUM

www.ti.com

10-Dec-2020

PACKAGING INFORMATION

Orderable Device

Status Package Type Package Pins Package

Eco Plan

Lead finish/

Ball material

MSL Peak Temp

Op Temp (°C)

Device Marking

Samples

Drawing

Qty

(1)

(2)

(3)

(4/5)

(6)

LM74670QDGKRQ1

LM74670QDGKTQ1

ACTIVE

VSSOP

DGK

2500 RoHS & Green

250 RoHS & Green

NIPDAUAG

Level-2-260C-1 YEAR

-40 to 125

ZGPK

NIPDAUAG

⁽¹⁾The marketing status values are defined as follows:

ACTIVE: Product device recommended for new designs.

LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.

NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.

PREVIEW: Device has been announced but is not in production. Samples may or may not be available.

OBSOLETE: TI has discontinued the production of the device.

⁽²⁾RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance

do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may

reference these types of products as "Pb-Free".

RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.

Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based

flame retardants must also meet the <=1000ppm threshold requirement.

⁽³⁾MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

⁽⁴⁾There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.

⁽⁵⁾Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation

of the previous line and the two combined represent the entire Device Marking for that device.

(6)

Lead finish/Ball material - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead finish/Ball material values may wrap to two

lines if the finish value exceeds the maximum column width.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information

provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and

continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.

TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

Addendum-Page 1

PACKAGE OPTION ADDENDUM

www.ti.com

10-Dec-2020

Addendum-Page 2

PACKAGE MATERIALS INFORMATION

www.ti.com

17-Jul-2020

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device

Package Package Pins

Type Drawing

SPQ

Reel

Pin1

Diameter Width (mm) (mm) (mm) (mm) (mm) Quadrant

(mm) W1 (mm)

LM74670QDGKRQ1

LM74670QDGKTQ1

VSSOP

DGK

2500

250

330.0

12.4

5.3

3.4

1.4

8.0

12.0

Pack Materials-Page 1

PACKAGE MATERIALS INFORMATION

www.ti.com

17-Jul-2020

*All dimensions are nominal

Device

Package Type Package Drawing Pins

SPQ

Length (mm) Width (mm) Height (mm)

LM74670QDGKRQ1

LM74670QDGKTQ1

VSSOP

DGK

2500

250

366.0

364.0

50.0

Pack Materials-Page 2

重要声明和免责声明

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LM74670-Q1 [TI]

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