参数资料
| 型号： | SC4508AMLTRT |
| 厂商： | Semtech |
| 文件页数： | 14/21页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST INV PWM 12-MLPQ |
| 标准包装： | 1 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 1.5MHz |
| 占空比： | 97% |
| 电源电压： | 2.7 V ~ 15 V |
| 降压： | 是 |
| 升压： | 是 |
| 回扫： | 无 |
| 反相： | 是 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 12-VQFN 裸露焊盘 |
| 包装： | 标准包装 |
| 产品目录页面： | 1358 (CN2011-ZH PDF) |
| 其它名称： | SC4508AMLDKR |
SC4508A
POWER MANAGEMENT
h =
k =
Application Information (Cont.)
The inner current-loop is unstable (sub-harmonic
oscillation) unless the inductor current up-slope is steeper
than the inductor current down-slope. For stable
operation above 50% duty-cycle, a compensation ramp
is added to the sensed-current. In the SC4508A the
compensation ramp is made switching frequency
dependent. The slope of the compensation ramp is:
S e = 500 * f s mV
0 .5
V o
For the rated output current I o , the current sensing gain
k is fixed as:
1
8 ? R S
From Figure 7, the transfer function from the voltage
error amplifier output (v c ) to the converter output (v o )is:
The slope of the internal compensation ramp is above
the minimal slope requirement for current loop stability
and is sufficient for all the applications. With the inner
current loop stable, the output voltage is then regulated
V o ( s )
V c ( s )
: = G vc ( s ) = kR o
1 +
1 +
s
s z 1
s
s p 1
with the outer voltage feedback loop. A simplified
equivalent circuit model of the buck converter with
where, the single dominant pole is:
current mode control is shown in Figure 7.
s p 1 =
1
( R o + R oesr ) C o
and the zero due to the output capacitor ESR is:
s z 1 =
1
R oesr C o
The dominant pole moves as output load varies.
The controller transfer function (from the converter
output (v o ) to the voltage error amplifier output (v c ) is:
1 +
k
where
G c ( s ) =
s
g m s z 2
s ( C 2 + C 3 ) 1 + s
s p 2
1
s z 2 =
R 2 C 2
Figure 7. A simple model of buck converter with current
mode control.
The transconductance error amplifier (in the SC4508A)
and
s p 2 =
R 2
1
C 2 C 3
C 2 + C 3
has a gain (g m ) of 100μA/V. The target of the
compensation design is to select the compensation
network consisting of C 2 , C 3 and R 2 , along with the
feedback resistors R o1 , R o2 and the current sensing gain,
such that the converter output voltage is regulated with
satisfactory dynamic performance.
With the output voltage V o known, the feedback gain h
and the feedback resistor values are determined using
the equations given in the “Output Voltage Setting”
section with:
The loop transfer function is then:
T(s)=G vc (s)G C (s)h
To simplify design, we assume that C 3 <<C 2 , R oesr <<R o,
selects S p1 =S z2 and specifies the loop crossover
frequency (f c ). It is noted that the crossover frequency
determines the converter dynamic bandwidth. With these
? 2007 Semtech Corp.
14
www.semtech.com
相关PDF资料 |
PDF描述 |
|---|---|
| SC4517AIMSTRT | IC REG BUCK ADJ 1.5A 8MSOP |
| SC4518HSETRT | IC REG BUCK 2A 8-SOIC |
| SC4519HSETRT | IC REG BUCK 3A 8-SOIC |
| SC4524ASETRT | IC REG BUCK 2A 8SOIC |
| SC4524BSETRT | IC REG BUCK 2A 8SOIC |
相关代理商/技术参数 |
参数描述 |
|---|---|
| SC4508IMLTRT | 制造商:Semtech Corporation 功能描述:DC/DC Converter (DC-DC) / Switching Regu |
| SC4509 | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:Highly Integrated Step-Up Converter for White LED Applications in MLPD-W8-2x2 |
| SC4509EVB | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:Highly Integrated Step-Up Converter for White LED Applications in MLPD-W8-2x2 |
| SC4509SK.TRT | 制造商:SEMTECH 功能描述:I.C. |
| SC4509SKTRT | 功能描述:IC LED DRVR WT/OLED BCKLT SOT236 RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:60 系列:- 恒定电流:- 恒定电压:- 拓扑:线性（LDO），PWM，升压（升压） 输出数:8 内部驱动器:是 类型 - 主要:背光 类型 - 次要:RGB，白色 LED 频率:500kHz ~ 1.5MHz 电源电压:4.75 V ~ 26 V 输出电压:45V 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* 工作温度:-40°C ~ 85°C |
发布紧急采购，3分钟左右您将得到回复。