参数资料
| 型号： | NE57811S/N1,518 |
| 厂商： | NXP Semiconductors |
| 文件页数： | 7/13页 |
| 文件大小： | 0K |
| 描述： | IC DDR TERMINATION SPAK-5 |
| 标准包装： | 2,000 |
| 应用： | 转换器，DDR，DDR2 |
| 输入电压： | 1.6 V ~ 3.6 V |
| 输出数： | 1 |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | SPAK-5 |
| 供应商设备封装： | 5-SPAK |
| 包装： | 带卷 (TR) |
| 其它名称： | 935284748518 NE57811S/N1-T NE57811S/N1-T-ND |
Philips Semiconductors
Advanced DDR memory termination power
with shutdown
THERMAL DESIGN
Product data
NE57811
Designing the proper thermal system for the NE57811 is important
to its reliable operation. The NE57811 will be operating at an
average power level less than the maximum rating of the part. In a
typical DDR terminator system the average power dissipation is
between 0.8 and 1.5 watts. The termination power will vary as the
average number of ‘1s’ and ‘0s’ changes during normal operation of
the DDR memory. The load current will assume a new value for
dimension as given on the X axis. If you use a double-sided PCB
with some plated-through holes to help transfer heat to the bottom
side, the thermal resistance only improves by about 3 – 4 ° C/W.
After the power is estimated, the minimum PCB area can be
determined by calculating the worst case thermal resistance and
referring to Figure 8 to determine the PCB area. This is done by:
each bus cycle at a 266 MHz rate, and will increase and decrease
as the statistical average of bus states change.
R qJA(min) +
T j * T amb
P D
Eqn. (2)
P D + I DD(VTT) Watts
The terminator heatsink must be designed to accommodate the
average power as a steady state condition and be able to withstand
momentary periods of increased dissipation, typically 2 – 5 seconds
duration. For the typical NE57811 application, the power dissipated
by the terminator can be calculated:
Eqn. (1)
The thermal resistance of a surface mount package is given as
R th(j-a ), the thermal resistance from the junction to air. JESD51-7
specifies a 4-layer multiplayer PCB (2oz/1oz/1oz/2oz copper) that is
4 inches on each side. This is probably the best (or lowest) thermal
resistance you will see in any application. Most applications cannot
Where:
T j is the maximum desired junction temperature
T amb is the highest expected local ambient temperature
P D is the estimated average power
The junction temperature should be kept well away from the
over-temperature cutoff threshold temperature (+150 ° C) in normal
operation.
Using the above power dissipation, the highest ambient temperature
and a junction temperature of +125 ° C, calculate the maximum
thermal resistance (1.5 watts is used only as an example).
R th(j–a)(min) + 125 C * 70 C + 36.6 o C W
afford the PCB area to create this situation, but the thermal
performance of a multilayer PCB will still provide a significant
o o
1.5W
Eqn. (3)
heatsinking effect. The actual thermal resistance will be higher than
the 16.5 ° C/W given for the 4-layer JEDEC PCB.
Figure 8 shows the thermal resistance you can expect for
heatsinking PCB areas less than the JEDEC specification. The
graph is for a 2 oz. single-sided PCB with a square area of the side
40.0
35.0
30.0
Looking at Figure 8, you see that this power dissipation requires a
minimum PCB island area of 225 mm 2 (15 mm on each side). This
is the smallest area you could use at this power dissipation. Of
course, increasing this area will allow the NE57811 to operate at
cooler temperatures, thus enhancing its long-term reliability.
10
0.25 s
0.5 s
25.0
DC
20.0
15.0
10.0
5.0
0.0
1
0.1
0
20
40
60
80
100
1
2
3
4
5
6
7
8
9 10
LENGTH OF SIDE OF 2 oz. COPPER AREA (mm)
SL01670
Figure 8. PCB heatsink area versus thermal resistance.
2003 Apr 02
7
V DD (V)
SL01678
Figure 9. Safe operating area for the NE57811.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| NE57814 | 制造商:PHILIPS 制造商全称:NXP Semiconductors 功能描述:DDR memory termination regulator with standby mode and enhanced efficiency |
| NE57814DD | 制造商:NXP Semiconductors 功能描述: 制造商:NXP Semiconductors 功能描述:DDR TERM W/STANDBY 8SOIC |
| NE57814DD,518 | 功能描述:线性稳压器 - 标准 DDR TERMINATOR REG RoHS:否 制造商:STMicroelectronics 输出类型: 极性: 输出电压:1.8 V 输出电流:150 mA 负载调节: 最大输入电压:5.5 V 线路调整率: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOT-323-5L |
| NE57814DD518 | 制造商:Rochester Electronics LLC 功能描述: 制造商:NXP 功能描述: 制造商:NXP Semiconductors 功能描述: |
| NE57835 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:TRANSISTOR | BJT | NPN | 11V V(BR)CEO | 30MA I(C) | SOT-173 |
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