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L6997

更新时间: 2024-01-29 23:57:17
品牌 Logo 应用领域
意法半导体 - STMICROELECTRONICS 控制器
页数 文件大小 规格书
23页 292K
描述
STEP DOWN CONTROLLER FOR LOW VOLTAGE OPERATIONS

L6997 技术参数

是否Rohs认证: 符合生命周期:Obsolete
零件包装代码:TSSOP包装说明:MO-153-AC, TSSOP-20
针数:20Reach Compliance Code:compliant
ECCN代码:EAR99HTS代码:8542.39.00.01
风险等级:8.01Samacsys Confidence:3
Samacsys Status:ReleasedSamacsys PartID:235356
Samacsys Pin Count:20Samacsys Part Category:Integrated Circuit
Samacsys Package Category:Small Outline PackagesSamacsys Footprint Name:TSSOP20
Samacsys Released Date:2015-11-23 08:23:37Is Samacsys:N
模拟集成电路 - 其他类型:SWITCHING CONTROLLER控制模式:VOLTAGE-MODE
控制技术:PULSE WIDTH MODULATION最大输入电压:5.5 V
最小输入电压:3 V标称输入电压:3.3 V
JESD-30 代码:R-PDSO-G20JESD-609代码:e4
长度:6.5 mm湿度敏感等级:3
功能数量:1端子数量:20
最高工作温度:125 °C最低工作温度:-40 °C
封装主体材料:PLASTIC/EPOXY封装代码:TSSOP
封装等效代码:TSSOP20,.25封装形状:RECTANGULAR
封装形式:SMALL OUTLINE, THIN PROFILE, SHRINK PITCH认证状态:Not Qualified
座面最大高度:1.2 mm子类别:Switching Regulator or Controllers
表面贴装:YES切换器配置:PUSH-PULL
温度等级:AUTOMOTIVE端子面层:Nickel/Palladium/Gold (Ni/Pd/Au)
端子形式:GULL WING端子节距:0.65 mm
端子位置:DUAL宽度:4.4 mm
Base Number Matches:1

L6997 数据手册

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L6997  
1
DEVICE DESCRIPTION  
1.1 Constant On Time PWM topology  
Figure 2. Loop block schematic diagram  
Vin  
R1  
One-shot generator  
OSC  
FFSR  
Q
R
R2  
HS  
LS  
Vsense  
Vout  
HGATE  
LGATE  
S
Q
Vref  
DS  
+
-
PWM comparator  
FB  
R4  
R3  
The device implements a Constant On Time control scheme, where the Ton is the high side MOSFET on time  
duration forced by the one-shot generator. The on time is directly proportional to VSENSE pin voltage and in-  
verse to OSC pin voltage as in Eq1:  
V
SENSE  
---------------------  
Eq 1  
T
= K  
+ τ  
ON  
OSC  
V
OSC  
where K  
= 250ns and  
τ
is the internal propagation delay time (typ. 70ns). The system imposes in steady  
OSC  
state a minimum on time corresponding to V  
= 1V. In fact if the V  
voltage increases above 1V the cor-  
OSC  
OSC  
responding Ton will not decrease. Connecting the OSC pin to a voltage partition from V to GND, it allows a  
IN  
steady-state switching frequency F  
independent of V . It results:  
SW  
IN  
V
α
OSC  
1
1
OUT  
-------------- ----------  
-------------- --------------  
Eq 2  
f
=
=
→ α  
= f K α  
SW OSC OUT  
SW  
OSC  
V
T
α
K
IN  
ON  
OUT OSC  
where  
Eq 3  
V
R
OSC  
2
α
α
= -------------- = --------------------  
OSC  
V
R + R  
IN  
2
1
V
R
FB  
4
Eq 4  
= -------------- = --------------------  
OUT  
V
R + R  
3 4  
OUT  
The above equations allow setting the frequency divider ratio  
α
once output voltage has been set; note that  
OSC  
such equations hold only if V  
<1V. Further the Eq2 shows how the system has a switching frequency ideally  
OSC  
independent from the input voltage. The delay introduces a light dependence from VIN. A minimum off-time con-  
strain of about 500ns is introduced in order to assure the boot capacitor charge and to limit the switching fre-  
6/23  

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