参数资料
| 型号： | SC2446ITETRT |
| 厂商： | Semtech |
| 文件页数： | 20/38页 |
| 文件大小： | 0K |
| 描述： | IC SYNC STEP DOWN CTRLR 28-TSSOP |
| 标准包装： | 1 |
| 应用： | 控制器，DDR |
| 输入电压： | 4.7 V ~ 16 V |
| 输出数： | 2 |
| 输出电压： | 可调至 0.5V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-SOIC（0.173"，4.40mm 宽）裸露焊盘 |
| 供应商设备封装： | 28-TSSOP 裸露焊盘 |
| 包装： | 标准包装 |
| 产品目录页面： | 1358 (CN2011-ZH PDF) |
| 其它名称： | SC2446ITEDKR |
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SC2446
POWER MANAGEMENT
Application Information (Cont.)
parameter sensitive operation. A good engineering
compromise is to make
? V Cs ~R eq δ I o .
The prerequisite for such relation is the so called time
constant matching condition
In the following design steps, the capacitor C S in the
current sensing part is commonly selected in the range
of 22nF ~ 68nF.
Vin
L
R eq
≈ R s C s .
V gs1
PN
Q1
iL(t)
L
RL
Cin
Rs
Rs 1
When Rds1=Rds2, the above relations become
equations.
For an example of application circuit, L=1.3μH,
RL=1.56m ? and Rds1=Rds2=8m ? , the time constant
R s C s should be set as 136μs. If one selects C s =33 nF,
then R s =4.12 k ? .
V gs2
V be3
VP N
V be4
Q3
Q4
Q2
Cs
vC(t)
C out
Rload
Vo
Scaling the Current Limit
+ 1
Rs 2
Over-current is handled differently in the SC2446
ISEN
- 2
R s3
depending on the direction of the inductor current. If the
differential sense voltage between CS+ and CS- exceeds
+75mV, the top MOSFET will be turned off and the bottom
MOSFET will be turned on to limit the inductor current.
This +75mV is the cycle-by-cycle peak current limit when
the load is drawing current from the converter. There is
no cycle-by-cycle current limit when the inductor current
flows in the reverse direction. If the voltage between
Figure 16. Scaling the equivalent current limit.
a) When the required current limit value I LM is greater
than I LMcp , one just needs to remove R s3 , and solve the
following equations
CS1+ and CS- falls below -113mV, the controller will
undergo overload shutdown and time-out with both the
top and the bottom MOSFETs shut off. (See the section
( R s // R s 1 ) C s =
L
R eq
,
Overload Protection and Hiccup).
In the circuit of Figure 14, the equivalent inductor current
limits are set according to
I LM R eq
R s 1
R s + R s 1
= 75 mV ,
I LMcp =
75mV
R eq
,
and
R s 2 = R s // R s 1 .
when the load is sourcing current from the converter and
for
R s , R s 1 and R s 2 .
I LMcn = ?
,
110mV
R eq
when the load is forcing current back to the input power
source. If R eq = 9.56mW, then I LM = 7.8/-11.8A. The circuit
in Figure 16 allows the user to scale the equivalent current
limit with the same R eq .
Note that R S2 is selected as R S //R S1 in order to reduce
the bias current effect of the current amplifier in SC2446.
If the current limit is to be set to I LM = 15A with the existing
power circuit parameter and C s = 33nF, it is calculated
that R s2 = 4.12 k ? , R s = 7.87 k ? and R s1 = 8.66 k ? .
b) When the required current limit I LM is less than I LMcp ,
one just needs to remove R s1 and solve
? 2004 Semtech Corp.
20
www.semtech.com
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SC2446ITSTRT | 制造商:Semtech Corporation 功能描述:Controller IC 制造商:Semtech Corporation 功能描述:SC Series 4.7 to 16 V 1 MHz Dual-Phase Synchronous Step-Down Controller TSSOP-28 |
| SC2447 | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:Dual-Phase, Single or Dual Output Synchronous Step-Down Controller |
| SC24-470-R | 功能描述:INDUCTOR SHIELD 47UH 150MA SMD RoHS:是 类别:电感器，线圈，扼流圈 >> 固定式 系列:SC24 标准包装:500 系列:1331 电感:1.2µH 电流:247mA 电流 - 饱和:247mA 电流 - 温升:- 类型:铁芯体 容差:±10% 屏蔽:屏蔽 DC 电阻(DCR):最大 730 毫欧 Q因子@频率:40 @ 7.9MHz 频率 - 自谐振:130MHz 材料 - 芯体:铁 封装/外壳:0.312" L x 0.115" W x 0.135" H（7.94mm x 2.92mm x 3.43mm） 安装类型:表面贴装 包装:带卷 (TR) 工作温度:-55°C ~ 105°C 频率 - 测试:7.9MHz |
| SC24-471-R | 功能描述:INDUCTOR SHIELD 470UH 50MA SMD RoHS:是 类别:电感器，线圈，扼流圈 >> 固定式 系列:SC24 标准包装:500 系列:1331 电感:1.2µH 电流:247mA 电流 - 饱和:247mA 电流 - 温升:- 类型:铁芯体 容差:±10% 屏蔽:屏蔽 DC 电阻(DCR):最大 730 毫欧 Q因子@频率:40 @ 7.9MHz 频率 - 自谐振:130MHz 材料 - 芯体:铁 封装/外壳:0.312" L x 0.115" W x 0.135" H（7.94mm x 2.92mm x 3.43mm） 安装类型:表面贴装 包装:带卷 (TR) 工作温度:-55°C ~ 105°C 频率 - 测试:7.9MHz |
| SC2447EVB | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:Dual-Phase, Single or Dual Output Synchronous Step-Down Controller |
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