品牌是'Microchip' (10000)

对比

图片

产品型号

品牌

数据表

库存

价格(含增值税)

数量

Rohs

工厂交货时间

触点镀层

底架

安装类型

包装/外壳

表面安装

引脚数

供应商器件包装

终端数量

操作温度

包装

已出版

JESD-609代码

无铅代码

零件状态

湿度敏感性等级(MSL)

终止次数

终端

ECCN 代码

端子表面处理

最高工作温度

最小工作温度

附加功能

HTS代码

子类别

技术

电压 - 供电

端子位置

终端形式

峰值回流焊温度(摄氏度)

功能数量

电源电压

端子间距

Reach合规守则

频率

时间@峰值回流温度-最大值(s)

基本部件号

引脚数量

JESD-30代码

资历状况

工作电源电压

电源电压-最大值(Vsup)

电源

温度等级

电源电压-最小值(Vsup)

界面

最大电源电压

最小电源电压

内存大小

电源电流

操作模式

时钟频率

电源电流-最大值

访问时间

内存格式

内存接口

组织结构

输出特性

座位高度-最大

内存宽度

写入周期时间 - 字符、页面

密度

待机电流-最大值

记忆密度

最高频率

筛选水平

并行/串行

内存IC类型

编程电压

串行总线类型

耐力

写入周期时间 - 最大值

数据保持时间

写入保护

备用内存宽度

数据轮询

拨动位

命令用户界面

页面尺寸

I2C控制字节

高度

座位高度(最大)

长度

宽度

辐射硬化

达到SVHC

RoHS状态

无铅

24AA02-I/PG
24AA02-I/PG
Microchip 数据表

N/A

-

最小起订量: 1

最小包装量: 1

NO

8

Compliant

0.300 INCH, ROHS COMPLIANT, PLASTIC, DIP-8

IN-LINE

256

PLASTIC/EPOXY

DIP8,.3

-40 °C

未说明

85 °C

24AA02-I/PG

0.1 MHz

256 words

2.5 V

DIP

RECTANGULAR

Microchip Technology Inc

活跃

MICROCHIP TECHNOLOGY INC

5.28

DIP

Bulk

e3

EAR99

Matte Tin (Sn)

85 °C

-40 °C

8542.32.00.51

EEPROMs

CMOS

DUAL

THROUGH-HOLE

未说明

1

2.54 mm

compliant

400 kHz

8

R-PDIP-T8

不合格

5.5 V

2/5 V

INDUSTRIAL

1.7 V

I2C

5.5 V

1.7 V

256 B

SYNCHRONOUS

0.003 mA

900 ns

256X8

5.334 mm

8

0.000001 A

2048 bit

400 kHz

SERIAL

EEPROM

I2C

1000000 Write/Erase Cycles

5 ms

200

HARDWARE

1010XXXR

9.27 mm

7.62 mm

无铅

24AA02-I/MSG
24AA02-I/MSG
Microchip 数据表

N/A

-

最小起订量: 1

最小包装量: 1

YES

8

8

Compliant

ROHS COMPLIANT, PLASTIC, MSOP-8

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

1

256

PLASTIC/EPOXY

TSSOP8,.19

-40 °C

40

85 °C

24AA02-I/MSG

0.1 MHz

256 words

2.5 V

TSSOP

SQUARE

Microchip Technology Inc

活跃

MICROCHIP TECHNOLOGY INC

5.23

MSOP

Bulk

e3

EAR99

Matte Tin (Sn)

85 °C

-40 °C

8542.32.00.51

EEPROMs

CMOS

DUAL

鸥翼

260

1

0.65 mm

compliant

8

S-PDSO-G8

不合格

5.5 V

2/5 V

INDUSTRIAL

1.7 V

I2C, Serial

5.5 V

1.8 V

256 B

SYNCHRONOUS

0.003 mA

900 ns

256X8

1.1 mm

8

2 kb

0.000001 A

2048 bit

400 kHz

SERIAL

EEPROM

I2C

1000000 Write/Erase Cycles

5 ms

200

HARDWARE

1010XXXR

3 mm

3 mm

无铅

24AA08-I/SNG
24AA08-I/SNG
Microchip 数据表

N/A

-

最小起订量: 1

最小包装量: 1

YES

8

Compliant

3.90 MM, ROHS COMPLIANT, PLASTIC, SOIC-8

小概要

1

1000

PLASTIC/EPOXY

SOP8,.25

-40 °C

40

85 °C

24AA08-I/SNG

0.1 MHz

1024 words

2.5 V

SOP

RECTANGULAR

Microchip Technology Inc

活跃

MICROCHIP TECHNOLOGY INC

5.2

SOIC

Bulk

e3

EAR99

Matte Tin (Sn)

85 °C

-40 °C

8542.32.00.51

EEPROMs

CMOS

DUAL

鸥翼

260

1

1.27 mm

compliant

8

R-PDSO-G8

不合格

5.5 V

2/5 V

INDUSTRIAL

1.7 V

I2C, Serial

5.5 V

1.8 V

1 kB

SYNCHRONOUS

0.003 mA

900 ns

1KX8

1.75 mm

8

8 kb

0.000001 A

8192 bit

400 kHz

SERIAL

EEPROM

I2C

1000000 Write/Erase Cycles

5 ms

200

HARDWARE

1010XMMR

4.9 mm

3.9 mm

无铅

24AA16T-I/MSG
24AA16T-I/MSG
Microchip 数据表

N/A

-

最小起订量: 1

最小包装量: 1

YES

8

8

Compliant

TSSOP, TSSOP8,.19

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

1

2000

PLASTIC/EPOXY

TSSOP

5.15

MICROCHIP TECHNOLOGY INC

活跃

Microchip Technology Inc

SQUARE

TSSOP

2.5 V

2048 words

0.1 MHz

24AA16T-I/MSG

85 °C

40

-40 °C

TSSOP8,.19

Tape & Reel (TR)

e3

EAR99

Matte Tin (Sn)

85 °C

-40 °C

1 MILLION ERASE/WRITE CYCLES

8542.32.00.51

EEPROMs

CMOS

DUAL

鸥翼

260

1

0.65 mm

compliant

8

S-PDSO-G8

不合格

5.5 V

2/5 V

INDUSTRIAL

1.7 V

I2C, Serial

5.5 V

1.7 V

2 kB

SYNCHRONOUS

0.003 mA

900 ns

2KX8

1.1 mm

8

16 kb

0.000001 A

16384 bit

400 kHz

SERIAL

EEPROM

I2C

1000000 Write/Erase Cycles

5 ms

200

HARDWARE

1010MMMR

3 mm

3 mm

无铅

24LC08B/SM
24LC08B/SM
Microchip 数据表

N/A

-

最小起订量: 1

最小包装量: 1

11AA020T-I/CS16K
11AA020T-I/CS16K
Microchip Technology 数据表

N/A

-

最小起订量: 1

最小包装量: 1

16 Weeks

Copper, Silver, Tin

表面贴装

表面贴装

4-UFBGA, CSPBGA

4

Non-Volatile

-40°C~85°C TA

Tape & Reel (TR)

2010

e1

活跃

1 (Unlimited)

4

EAR99

Tin/Silver/Copper (Sn/Ag/Cu)

1.8V~5.5V

BOTTOM

1

5V

11AA020

4

5.5V

2/5V

1.8V

Serial

2Kb 256 x 8

5mA

100kHz

EEPROM

单线

256X8

8

5ms

2 kb

0.000005A

1-WIRE

1000000 Write/Erase Cycles

10ms

200

SOFTWARE

0.55mm

ROHS3 Compliant

24LC164-I/SN
24LC164-I/SN
Microchip 数据表

N/A

-

最小起订量: 1

最小包装量: 1

YES

8

Non-Compliant

SOP, SOP8,.25

小概要

2000

PLASTIC/EPOXY

SOP8,.25

-40 °C

未说明

85 °C

24LC164-I/SN

0.1 MHz

2048 words

3 V

SOP

RECTANGULAR

Microchip Technology Inc

Obsolete

MICROCHIP TECHNOLOGY INC

5.87

SOIC

e0

Tin/Lead (Sn/Pb)

DATA RETENTION > 200 YEARS; 1000000 ERASE/WRITE CYCLES GUARANTEED

EEPROMs

CMOS

DUAL

鸥翼

未说明

1

1.27 mm

unknown

8

R-PDSO-G8

不合格

5.5 V

3/5 V

INDUSTRIAL

2.5 V

SYNCHRONOUS

0.003 mA

2KX8

OPEN-DRAIN

1.75 mm

8

0.00003 A

16384 bit

SERIAL

EEPROM

I2C

1000000 Write/Erase Cycles

10 ms

200

HARDWARE

1DDDMMMR

4.9 mm

3.9 mm

93AA56C-I/SNG
93AA56C-I/SNG
Microchip 数据表

N/A

-

最小起订量: 1

最小包装量: 1

YES

8

Compliant

3.90 MM, ROHS COMPLIANT, PLASTIC, SOIC-8

小概要

1

128

PLASTIC/EPOXY

SOP8,.25

-40 °C

40

85 °C

93AA56C-I/SNG

1 MHz

128 words

5 V

SOP

RECTANGULAR

Microchip Technology Inc

活跃

MICROCHIP TECHNOLOGY INC

5.2

SOIC

Bulk

e3

EAR99

Matte Tin (Sn)

85 °C

-40 °C

8542.32.00.51

EEPROMs

CMOS

DUAL

鸥翼

260

1

1.27 mm

compliant

8

R-PDSO-G8

不合格

5.5 V

2/5 V

INDUSTRIAL

1.8 V

Serial

5.5 V

1.8 V

256 B

SYNCHRONOUS

0.002 mA

128X16

1.75 mm

16

2 kb

0.000001 A

2048 bit

1 MHz

SERIAL

EEPROM

MICROWIRE

1000000 Write/Erase Cycles

6 ms

200

SOFTWARE

8

4.9 mm

3.9 mm

无铅

25LC080B-I/MSG
25LC080B-I/MSG
Microchip 数据表

N/A

-

最小起订量: 1

最小包装量: 1

YES

8

TSSOP, TSSOP8,.19

SMALL OUTLINE, THIN PROFILE, SHRINK PITCH

1

1000

PLASTIC/EPOXY

TSSOP8,.19

-40 °C

40

85 °C

25LC080B-I/MSG

10 MHz

1024 words

5 V

TSSOP

SQUARE

Microchip Technology Inc

不推荐

MICROCHIP TECHNOLOGY INC

5.26

MSOP

e3

EAR99

Matte Tin (Sn)

8542.32.00.51

EEPROMs

CMOS

DUAL

鸥翼

260

1

0.65 mm

compliant

8

S-PDSO-G8

不合格

5.5 V

3/5 V

INDUSTRIAL

2.5 V

SYNCHRONOUS

0.006 mA

1KX8

1.1 mm

8

0.000001 A

8192 bit

SERIAL

EEPROM

SPI

1000000 Write/Erase Cycles

5 ms

200

HARDWARE/SOFTWARE

3 mm

3 mm

93C66CX-E/SN
93C66CX-E/SN
Microchip 数据表

N/A

-

最小起订量: 1

最小包装量: 1

YES

8

SOP, SOP8,.25

小概要

1

256

PLASTIC/EPOXY

SOP8,.25

-40 °C

40

125 °C

93C66CX-E/SN

2 MHz

256 words

5 V

SOP

RECTANGULAR

Microchip Technology Inc

活跃

MICROCHIP TECHNOLOGY INC

5.21

SOIC

e3

EAR99

Matte Tin (Sn)

ALSO CONFIGURABLE AS 512 X 8

8542.32.00.51

EEPROMs

CMOS

DUAL

鸥翼

260

1

1.27 mm

compliant

8

R-PDSO-G8

不合格

5.5 V

5 V

AUTOMOTIVE

4.5 V

SYNCHRONOUS

0.002 mA

256X16

1.75 mm

16

0.000005 A

4096 bit

SERIAL

EEPROM

MICROWIRE

1000000 Write/Erase Cycles

2 ms

200

SOFTWARE

8

4.9 mm

3.9 mm

24C02A/SN
24C02A/SN
Microchip 数据表

50000 In Stock

-

最小起订量: 1

最小包装量: 1

YES

8

Non-Compliant

SOP, SOP8,.25

小概要

1

256

PLASTIC/EPOXY

SOP8,.25

40

70 °C

24C02A/SN

0.1 MHz

256 words

5 V

SOP

RECTANGULAR

Microchip Technology Inc

Obsolete

MICROCHIP TECHNOLOGY INC

8.44

SOIC

e3

EAR99

Matte Tin (Sn)

8542.32.00.51

EEPROMs

CMOS

DUAL

鸥翼

260

1

1.27 mm

unknown

8

R-PDSO-G8

不合格

5.5 V

5 V

COMMERCIAL

4.5 V

SYNCHRONOUS

0.0035 mA

256X8

OPEN-DRAIN

8

0.0001 A

2048 bit

SERIAL

EEPROM

I2C

1000000 Write/Erase Cycles

1 ms

200

HARDWARE

1010DDDR

AT25160BY6-YH-T
AT25160BY6-YH-T
Microchip Technology 数据表

N/A

-

最小起订量: 1

最小包装量: 1

表面贴装

表面贴装

8-UFDFN Exposed Pad

8

8-Mini Map (2x3)

Non-Volatile

-40°C~85°C TA

Tape & Reel (TR)

1997

Obsolete

1 (Unlimited)

85°C

-40°C

1.8V~5.5V

20MHz

AT25160

5V

SPI, Serial

5.5V

1.8V

16Kb 2K x 8

10mA

20MHz

80 ns

EEPROM

SPI

5ms

16 kb

5MHz

ROHS3 Compliant

93LC76CT-I/MS
93LC76CT-I/MS
Microchip Technology 数据表

55 In Stock

-

最小起订量: 1

最小包装量: 1

7 Weeks

Tin

表面贴装

表面贴装

8-TSSOP, 8-MSOP (0.118, 3.00mm Width)

8

Non-Volatile

-40°C~85°C TA

Tape & Reel (TR)

2012

e3

yes

活跃

1 (Unlimited)

8

2.5V~5.5V

DUAL

260

1

3V

0.65mm

40

93LC76C

8

5.5V

3/5V

2.5V

Serial

8Kb 1K x 8 512 x 16

3mA

3MHz

100 ns

EEPROM

SPI

512X16

16

5ms

8 kb

0.000001A

MICROWIRE

1000000 Write/Erase Cycles

5ms

200

HARDWARE/SOFTWARE

8

1.1mm

3mm

3mm

ROHS3 Compliant

无铅

AT28C256-15LM/883
AT28C256-15LM/883
Microchip Technology 数据表

2420 In Stock

-

最小起订量: 1

最小包装量: 1

23 Weeks

Lead, Tin

表面贴装

表面贴装

32-CLCC

32

Non-Volatile

Military grade

-55°C~125°C TC

Tube

1997

e0

no

活跃

1 (Unlimited)

32

Tin/Lead (Sn/Pb)

自动写入

4.5V~5.5V

QUAD

225

1

5V

1.27mm

150GHz

30

AT28C256

5V

5V

Parallel, SPI

256Kb 32K x 8

150ns

EEPROM

Parallel

3-STATE

8

10ms

256 kb

0.0003A

MIL-STD-883 Class C

5V

10000 Write/Erase Cycles

10ms

YES

YES

64words

2.54mm

13.97mm

11.43mm

Non-RoHS Compliant

含铅

93LC46A-I/SN
93LC46A-I/SN
Microchip Technology 数据表

5 In Stock

-

最小起订量: 1

最小包装量: 1

6 Weeks

表面贴装

表面贴装

8-SOIC (0.154, 3.90mm Width)

8

Non-Volatile

-40°C~85°C TA

Tube

e3

yes

活跃

1 (Unlimited)

8

EAR99

Matte Tin (Sn) - annealed

1000000 ERASE/WRITE CYCLES MIN; DATA RETENTION > 200 YEARS

2.5V~5.5V

DUAL

260

1

3V

1.27mm

40

93LC46A

8

5.5V

3/5V

2.5V

Serial

1Kb 128 x 8

2mA

2MHz

250 ns

EEPROM

SPI

6ms

1 kb

0.000001A

MICROWIRE

1000000 Write/Erase Cycles

6ms

200

SOFTWARE

1.25mm

4.9mm

3.9mm

无SVHC

ROHS3 Compliant

无铅

24LC08BT-I/SN
24LC08BT-I/SN
Microchip Technology 数据表

13200 In Stock

-

最小起订量: 1

最小包装量: 1

7 Weeks

表面贴装

表面贴装

8-SOIC (0.154, 3.90mm Width)

8

8-SOIC

Non-Volatile

-40°C~85°C TA

Tape & Reel (TR)

2005

活跃

1 (Unlimited)

85°C

-40°C

2.5V~5.5V

400kHz

24LC08B

2-Wire, I2C, Serial

5.5V

2.5V

8Kb 256 x 8 x 4

3mA

400kHz

900ns

EEPROM

I2C

5ms

8 kb

400kHz

无SVHC

ROHS3 Compliant

无铅

AT28HC256-12JU
AT28HC256-12JU
Microchip Technology 数据表

900 In Stock

-

最小起订量: 1

最小包装量: 1

8 Weeks

Tin

表面贴装

表面贴装

32-LCC (J-Lead)

32

Non-Volatile

Military grade

-40°C~85°C TC

Tube

1997

e3

yes

活跃

2 (1 Year)

32

自动写入

4.5V~5.5V

QUAD

245

1

5V

1.27mm

5MHz

40

AT28HC256

5V

5V

256Kb 32K x 8

80mA

120ns

EEPROM

Parallel

3-STATE

8

10ms

256 kb

0.0003A

MIL-STD-883

5V

10000 Write/Erase Cycles

10ms

YES

YES

NO

64words

3.556mm

13.97mm

11.43mm

ROHS3 Compliant

无铅

25LC080B-I/MS
25LC080B-I/MS
Microchip Technology 数据表

500 In Stock

-

最小起订量: 1

最小包装量: 1

7 Weeks

表面贴装

表面贴装

8-TSSOP, 8-MSOP (0.118, 3.00mm Width)

8

Non-Volatile

-40°C~85°C TA

Tube

2007

e3

yes

活跃

1 (Unlimited)

8

SMD/SMT

EAR99

Matte Tin (Sn)

2.5V~5.5V

DUAL

260

1

5V

0.65mm

40

25LC080B

8

5.5V

3/5V

2.5V

SPI, Serial

8Kb 1K x 8

6mA

10MHz

100 ns

EEPROM

SPI

5ms

8 kb

0.000001A

SPI

1000000 Write/Erase Cycles

5ms

200

HARDWARE/SOFTWARE

950μm

3mm

3mm

无SVHC

ROHS3 Compliant

93C46AT-E/MS
93C46AT-E/MS
Microchip Technology 数据表

25 In Stock

-

最小起订量: 1

最小包装量: 1

9 Weeks

Tin

表面贴装

表面贴装

8-TSSOP, 8-MSOP (0.118, 3.00mm Width)

8

Non-Volatile

-40°C~125°C TA

Tape & Reel (TR)

2002

e3

yes

活跃

1 (Unlimited)

8

EAR99

4.5V~5.5V

DUAL

260

1

5V

0.65mm

40

93C46A

8

5V

5V

Serial

1Kb 128 x 8

2mA

2MHz

250 ns

EEPROM

SPI

8

2ms

1 kb

0.000005A

MICROWIRE

1000000 Write/Erase Cycles

6ms

200

SOFTWARE

1.1mm

3mm

3mm

ROHS3 Compliant

无铅

AT28C256-25FM/883
AT28C256-25FM/883
Microchip Technology 数据表

2965 In Stock

-

最小起订量: 1

最小包装量: 1

23 Weeks

Lead, Tin

表面贴装

表面贴装

28-CFlatPack

28

Non-Volatile

Military grade

-55°C~125°C TC

Tube

1997

e0

no

活跃

3 (168 Hours)

28

锡铅

自动写入

4.5V~5.5V

DUAL

240

1

5V

1.27mm

30

AT28C256

5V

5V

Parallel, SPI

256Kb 32K x 8

50mA

250ns

EEPROM

Parallel

32KX8

3-STATE

8

10ms

256 kb

0.0003A

MIL-STD-883 Class C

5V

10000 Write/Erase Cycles

10ms

YES

YES

64words

3.02mm

10.16mm

Non-RoHS Compliant

AT28C010-15LM/883
AT28C010-15LM/883
Microchip Technology 数据表

N/A

-

最小起订量: 1

最小包装量: 1

Lead, Tin

表面贴装

表面贴装

44-CLCC

44

Non-Volatile

Military grade

-55°C~125°C TC

Tube

1998

e0

活跃

1 (Unlimited)

44

3A001.A.2.C

Tin/Lead (Sn/Pb)

AUTOMATIC WRITE; DATA RETENTION: 10 YEARS

8542.32.00.51

4.5V~5.5V

QUAD

未说明

1

5V

1.27mm

not_compliant

150GHz

未说明

AT28C010

不合格

5V

5V

1Mb 128K x 8

80mA

ASYNCHRONOUS

150ns

EEPROM

Parallel

128KX8

3-STATE

8

10ms

1 Mb

0.0003A

MIL-STD-883

5V

10000 Write/Erase Cycles

10ms

YES

YES

NO

128words

2.74mm

16.55mm

16.55mm

Non-RoHS Compliant

含铅

93LC46AX-E/SN
93LC46AX-E/SN
Microchip Technology 数据表

25 In Stock

-

最小起订量: 1

最小包装量: 1

6 Weeks

Tin

表面贴装

表面贴装

8-SOIC (0.154, 3.90mm Width)

8

Non-Volatile

-40°C~125°C TA

Tube

2003

e3

yes

活跃

1 (Unlimited)

8

EAR99

2.5V~5.5V

DUAL

260

1

3V

1.27mm

40

93LC46A

8

5.5V

3/5V

2.5V

Serial

1Kb 128 x 8

2mA

2MHz

250 ns

EEPROM

SPI

8

6ms

1 kb

0.000005A

MICROWIRE

1000000 Write/Erase Cycles

6ms

200

SOFTWARE

1.75mm

4.9mm

3.9mm

ROHS3 Compliant

无铅

AT28HC256F-90SU
AT28HC256F-90SU
Microchip Technology 数据表

5000 In Stock

-

最小起订量: 1

最小包装量: 1

14 Weeks

Tin

表面贴装

表面贴装

28-SOIC (0.295, 7.50mm Width)

28

Non-Volatile

-40°C~85°C TC

Tube

1997

e3

yes

活跃

2 (1 Year)

28

4.5V~5.5V

DUAL

1

5V

1.27mm

5MHz

AT28HC256

5V

256Kb 32K x 8

80mA

90ns

EEPROM

Parallel

32KX8

8

3ms

256 kb

5V

3ms

2.65mm

17.9mm

7.5mm

ROHS3 Compliant

无铅

93C46BXT-I/SN
93C46BXT-I/SN
Microchip Technology 数据表

1595 In Stock

-

最小起订量: 1

最小包装量: 1

6 Weeks

Tin

表面贴装

表面贴装

8-SOIC (0.154, 3.90mm Width)

8

Non-Volatile

-40°C~85°C TA

Tape & Reel (TR)

2008

e3

yes

活跃

1 (Unlimited)

8

EAR99

1000000 ERASE/WRITE CYCLES; DATA RETENTION > 200 YEARS

4.5V~5.5V

DUAL

260

1

5V

1.27mm

40

93C46B

8

5V

5V

Serial

1Kb 64 x 16

2mA

2MHz

250 ns

EEPROM

SPI

64X16

16

2ms

1 kb

0.000001A

MICROWIRE

1000000 Write/Erase Cycles

6ms

200

SOFTWARE

1.75mm

4.9mm

3.9mm

ROHS3 Compliant

无铅

93LC46AXT-I/SN
93LC46AXT-I/SN
Microchip Technology 数据表

3461 In Stock

-

最小起订量: 1

最小包装量: 1

6 Weeks

表面贴装

表面贴装

8-SOIC (0.154, 3.90mm Width)

8

Non-Volatile

-40°C~85°C TA

Tape & Reel (TR)

2003

e3

yes

活跃

1 (Unlimited)

8

EAR99

Matte Tin (Sn)

1000000 ERASE/WRITE CYCLES MIN; DATA RETENTION > 200 YEARS

2.5V~5.5V

DUAL

260

1

3V

1.27mm

40

93LC46A

8

5.5V

3/5V

2.5V

Serial

1Kb 128 x 8

2mA

2MHz

250 ns

EEPROM

SPI

8

6ms

1 kb

0.000001A

MICROWIRE

1000000 Write/Erase Cycles

6ms

200

SOFTWARE

1.75mm

4.9mm

3.9mm

ROHS3 Compliant

无铅