Datasheet > AS2954BT3-3.3

AS2954BT3-3.3

更新时间： 2024-01-01 20:56:51

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其他 - ETC		模拟IC
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AS2954BT3-3.3 技术参数

是否Rohs认证：	不符合	生命周期：	Obsolete
包装说明：	TO-263, 3 PIN	Reach Compliance Code：	unknown
风险等级：	5.75	Is Samacsys：	N
最大回动电压 1：	0.6 V	最大输入电压：	30 V
最小输入电压：	6 V	JESD-30 代码：	R-PSSO-G2
长度：	10.287 mm	湿度敏感等级：	1
功能数量：	1	端子数量：	2
工作温度TJ-Max：	125 °C	工作温度TJ-Min：	-40 °C
最大输出电流 1：	0.25 A	最大输出电压 1：	3.432 V
最小输出电压 1：	3.168 V	标称输出电压 1：	3.3 V
封装主体材料：	PLASTIC/EPOXY	封装代码：	TO-263
封装形状：	RECTANGULAR	封装形式：	SMALL OUTLINE
峰值回流温度（摄氏度）：	225	认证状态：	Not Qualified
调节器类型：	FIXED POSITIVE SINGLE OUTPUT LDO REGULATOR	座面最大高度：	4.597 mm
表面贴装：	YES	端子形式：	GULL WING
端子节距：	2.6 mm	端子位置：	SINGLE
处于峰值回流温度下的最长时间：	NOT SPECIFIED	宽度：	9.04 mm
Base Number Matches：	1

AS2954BT3-3.3 数据手册

AS2954

Also, it may be programmed for any output voltage between its

1.235V reference and its 30V maximum rating. As seen in

Figure 2, an external pair of resistors is required.

Refer to the below equation for the programming of the output

voltage:

REDUCING OUTPUT NOISE

It may be an advantage to reduce the AC noise present at the output.

One way is to reduce the regulator bandwidth by increasing the size of

the output capacitor. This is the only way that noise can be reduced

on the 3 lead AS2954 but is relatively inefficient, as increasing the

capacitor from 1µF to 220µF only decreases the noise from 430µV to

160µV rms for a 100kHz bandwidth at 5V output.

_OUT= V_REF× ( 1 + R₁\ R₂)+ I_FBR₁

Noise could also be reduced fourfold by a bypass capacitor across R₁,

since it reduces the high frequency gain from 4 to unity. Pick

The V_REFis 1.235 and I_FBis the feedback bias current, nominally

-20nA. The minimum recommended load current of 1µA forces

an upper limit of 1.2 MΩ on value of R₂. If no load is presented

the I_FBproduces an error of typically 2% in V_OUT, which may be

eliminated at room temperature by trimming R₁. To improve the

accuracy choose the value of R₂= 100k this reduces the error by

0.17% and increases the resistor program current by 12µA. Since

the LP2951 typically draws 60µA at no load with Pin 2 open-

circuited this is a small price to pay

_BYPASS≅ 1 / 2πR₁× 200 Hz

or choose 0.01µF. When doing this, the output capacitor must be

increased to 3.3µF to maintain stability. These changes reduce the

output noise from 430µV to 100µV_RMSfor a 100kHz bandwidth at 5V

output. With the bypass capacitor added, noise no longer scales with

output voltage so that improvements are more dramatic at higher

output voltages.

HEATSINK REQUIREMENTS

Depending on the maximum ambient temperature and maximum

power dissipation a heatsink may be required with the AS2954.

The junction temperature range has to be within the range

specified under Absolute Maximum Ratings under all possible

operating conditions. To find out if a heatsink is required, the

maximum power dissipation of the device needs to be calculated.

This is the maximum specific AC voltage that must be taken into

consideration at input. Figure 3 shows the condition and power

dissipation which should be calculated with the following

formula:

I_IN

V_IN

OUT

I_L

_TOTAL= (V_IN- 5) I_L+ (V_IN)I_G

AS2954

LOAD

Next step is to calculate the temperature rise T_R(_MAX). T_J(_MAX

)

maximum allowable junction temperature, T_A

ambient temperature :

(_MAX) maximum

2.2 uF

GND

T_R(_MAX) = T_J(_MAX) - T_A(_MAX

)

I_G

I_IN= I_L+ I_G

Junction to ambient thermal resistance θ_(j-A)can be calculated

after determining of P_{TOTAL &}T_R(_MAX):

Figure 3. 5V Regulator Circuit

θ_(J-A)= T_R(max)/P_(MAX)

If the θ_(J-A)is 60°C/W or higher, the device could be operated

without a heatsink. If the value is below 60°C/W then the

heatsink is required and the thermal resistance of the heatsink can

be calculated by the following formula, θ_(J-C)junction to case,

θ_(C-H)case to heatsink, θ_(H-A)heatsink to ambient:

θ_(J-A)= θ_(J-C)+ θ_(C-H)+ θ_(H-A)

Rev.9/29/00

1 2 3 456

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与AS2954BT3-3.3相关器件

型号	品牌	描述	获取价格	数据表
AS2954BT3-5.0	SIPEX	Fixed Positive LDO Regulator, 5V, 0.6V Dropout, PSSO2, TO-263, 3 PIN	获取价格
AS2954BT5-3.3	SIPEX	Fixed/Adjustable Positive LDO Regulator, 1.24V Min, 29V Max, 0.6V Dropout, PSSO5, TO-263,	获取价格
AS2954BT5-5.0	SIPEX	Fixed/Adjustable Positive LDO Regulator, 1.24V Min, 29V Max, 0.6V Dropout, PSSO5, TO-263,	获取价格
AS2954BU3-3.3	SIPEX	Fixed Positive LDO Regulator, 3.3V, 0.6V Dropout, PSFM3, TO-220, 3 PIN	获取价格
AS2954BU3-5.0	SIPEX	Fixed Positive LDO Regulator, 5V, 0.6V Dropout, PSFM3, TO-220, 3 PIN	获取价格
AS2954BU5.0	CALOGIC	Fixed Positive LDO Regulator, 5V, 0.6V Dropout, PSFM3, TO-220, 3 PIN	获取价格

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