SDRAM技术详解：MT48LC系列内存规格与特性

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SDRAM,全称同步动态随机访问存储器(Synchronous Dynamic Random Access Memory)，是一种广泛应用于个人计算机和嵌入式系统中的内存类型。本文档介绍的是三种不同容量的MT系列SDRAM产品：MT48LC128M4A2（32MB x 4 banks）、MT48LC64M8A2（16MB x 8 banks）和MT48LC32M16A2（8MB x 16 banks）。这些器件符合PC100和PC133标准，这意味着它们能在时钟信号的上升沿进行全同步操作，并且数据传输在每个时钟周期内完成。 SDRAM的特点包括： 1. **兼容性**：支持多种工作模式，如PC100和PC133，确保与系统时钟同步。 2. **内部操作**：采用内部数据缓存和流水线设计，允许列地址在每个时钟周期内改变，提高了读写效率。 3. **银行结构**：内置银行机制有助于隐藏行访问时间和预充电时间，提高整体性能。 4. **可编程突发长度**：支持1、2、4、8或整页的突发读取，增加了灵活性。 5. **自动预充与自动刷新**：具备多种刷新模式，如同时预充电和自动刷新，以及自刷新功能，提供低功耗选项。 6. **低电压接口**：采用LVTTL兼容输入输出，便于与其他电路集成。 7. **电源需求**：单一3.3V±0.3V电源供电。 8. **封装形式**：包括标准塑料封装OCPL2-54针TSOP-II (400 mil) 和无铅版本TG-54针TSOP-II (400 mil)。 9. **时序参数**：例如，7.5ns的循环时间在CL=3 (PC133)下，以及不同的时钟周期对于不同工作模式。 10. **温度范围**：商业级适用于0°C至+70°C，工业级则扩展到-40°C至+85°C。选择选项包括不同的配置（如128M4、64M8和32M16），以及写入恢复时间（tWR）的具体值。此外，文档还提到两种自刷新模式：标准模式和低功耗模式，以及相应的功耗特性。总结来说，这份文档详细介绍了MT系列SDRAM产品的规格、性能指标和操作特性，是设计工程师在选择和使用SDRAM作为系统内存时的重要参考资料。了解并掌握这些技术细节，能够帮助开发者优化系统设计，提升设备运行速度和稳定性。

Temperature and Thermal Impedance

It is imperative that the SDRAM device’s temperature specifications, shown in Table 6

(page 14), be maintained to ensure the junction temperature is in the proper operat-

ing range to meet data sheet specifications. An important step in maintaining the prop-

er junction temperature is using the device’s thermal impedances correctly. The ther-

mal impedances are listed in Table 6 (page 14) for the applicable die revision and

packages being made available. These thermal impedance values vary according to the

density, package, and particular design used for each device.

Incorrectly using thermal impedances can produce significant errors. Read Micron

technical note TN-00-08, “Thermal Applications” prior to using the thermal impedan-

ces listed in Table 6 (page 14). To ensure the compatibility of current and future de-

signs, contact Micron Applications Engineering to confirm thermal impedance values.

The SDRAM device’s safe junction temperature range can be maintained when the T

specification is not exceeded. In applications where the device’s ambient temperature

is too high, use of forced air and/or heat sinks may be required to satisfy the case tem-

perature specifications.

Table 5: Temperature Limits

Parameter Symbol Min Max Unit Notes

Operating case temperature Commercial T

0 80 °C 1, 2, 3, 4

Industrial –40 90

Junction temperature Commercial T

0 85 °C 3

Industrial –40 95

Ambient temperature Commercial T

0 70 °C 3, 5

Industrial –40 85

Peak reflow temperature T

PEAK

– 260 °C

Notes:

1. MAX operating case temperature, TC, is measured in the center of the package on the

top side of the device, as shown in Figure 6 (page 14).

2. Device functionality is not guaranteed if the device exceeds maximum T

during opera-

tion.

3. All temperature specifications must be satisfied.

4. The case temperature should be measured by gluing a thermocouple to the top-center

of the component. This should be done with a 1mm bead of conductive epoxy, as de-

fined by the JEDEC EIA/JESD51 standards. Take care to ensure that the thermocouple

bead is touching the case.

5. Operating ambient temperature surrounding the package.

512Mb: x4, x8, x16 SDRAM

Temperature and Thermal Impedance

PDF: 09005aef809bf8f3

512Mb_sdr.pdf - Rev. O 2/12 EN

Micron Technology, Inc. reserves the right to change products or specifications without notice.

Electrical Specifications

Stresses greater than those listed may cause permanent damage to the device. This is a

stress rating only, and functional operation of the device at these or any other condi-

tions above those indicated in the operational sections of this specification is not im-

plied. Exposure to absolute maximum rating conditions for extended periods may affect

reliability.

Table 7: Absolute Maximum Ratings

Voltage/Temperature Symbol Min Max Unit Notes

Voltage on V

DDQ

supply relative to V

DDQ

–1 +4.6 V 1

Voltage on inputs, NC, or I/O balls relative to V

–1 +4.6

Storage temperature (plastic) T

STG

–55 +155 °C

Power dissipation – – 1 W

Note:

1. V

and V

DDQ

must be within 300mV of each other at all times. V

DDQ

must not exceed

Table 8: DC Electrical Characteristics and Operating Conditions

Notes 1–3 apply to all parameters and conditions; V

DDQ

= +3.3V ±0.3V

Parameter/Condition Symbol Min Max Unit Notes

Supply voltage V

, V

DDQ

3 3.6 V

Input high voltage: Logic 1; All inputs V

2 V

+ 0.3 V 4

Input low voltage: Logic 0; All inputs V

–0.3 +0.8 V 4

Output high voltage: I

OUT

= –4mA V

2.4 – V

Output low voltage: I

OUT

= 4mA V

– 0.4 V

Input leakage current:

Any input 0V ≤ V

≤ V

(All other balls not under test = 0V)

–5 5 μA

Output leakage current: DQ are disabled; 0V ≤ V

OUT

≤ V

DDQ

–5 –5 μA

Operating temperature: Commercial T

0 +70 ˚C

Industrial T

–40 +85 ˚C

Notes:

1. All voltages referenced to V

2. The minimum specifications are used only to indicate cycle time at which proper opera-

tion over the full temperature range is ensured; (0°C ≤ TA ≤ +70°C (commercial), –40°C ≤

TA ≤ +85°C (industrial), and –40°C ≤ TA ≤ +105°C (automotive)).

3. An initial pause of 100μs is required after power-up, followed by two AUTO REFRESH

commands, before proper device operation is ensured. (V

and V

DDQ

must be powered

up simultaneously. V

and V

SSQ

must be at same potential.) The two AUTO REFRESH

command wake-ups should be repeated any time the

REF refresh requirement is excee-

ded.

4. V

overshoot: V

IH,max

= V

DDQ

+ 2V for a pulse width ≤ 3ns, and the pulse width cannot

be greater than one-third of the cycle rate. V

undershoot: V

IL,min

= –2V for a pulse

width ≤3ns.

512Mb: x4, x8, x16 SDRAM

Electrical Specifications

PDF: 09005aef809bf8f3

512Mb_sdr.pdf - Rev. O 2/12 EN

Micron Technology, Inc. reserves the right to change products or specifications without notice.

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