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| 型号： | PM6670STR |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 稳压器 |
| 英文描述： | 3 A SWITCHING CONTROLLER, QCC24 |
| 封装： | 4 X 4 MM, LEAD FREE, VFQFPN-24 |
| 文件页数： | 33/54页 |
| 文件大小： | 742K |
| 代理商： | PM6670STR |
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PM6670S
Application information
Doc ID 14432 Rev 4
39/54
8
Application information
The purpose of this chapter is to show the design procedure of the switching section.
The design starts from three main specifications:
●
The input voltage range, provided by the battery or the AC adapter. The two extreme
values (VINMAX and VINmin) are important for the design.
●
The maximum load current, indicated by ILOAD,MAX.
●
The maximum allowed output voltage ripple VRIPPLE,MAX.
It's also possible that specific designs should involve other specifications.
The following paragraphs will guide the user into a step-by-step design.
8.1
External components selection
The PM6670S uses a pseudo-fixed frequency, constant on-time (COT) controller as the core
of the switching section. The switching frequency can be set by connecting an external
divider to the VOSC pin. The voltage seen at this pin must be greater than 0.8 V and lower
than 2 V in order to ensure system's linearity.
Nearly constant switching frequency is achieved by the system's loop in steady-state
operating conditions by varying the on-time duration, avoiding thus the need for a clock
generator. The On-Time one shot duration is directly proportional to the output voltage,
sensed at VSNS pin, and inversely proportional to the input voltage, sensed at the VOSC
pin, as follows:
Equation 24
where KOSC is a constant value (130 ns typ.) and τ is the internal propagation delay
(40 ns typ.).
The duty cycle of the buck converter is, under steady state conditions, given by
Equation 25
The switching frequency is thus calculated as
Equation 26
τ
+
=
OSC
SNS
OSC
ON
V
K
T
IN
OUT
V
D
=
OSC
OUT
OSC
SNS
OSC
IN
OUT
ON
SW
K
1
V
K
V
T
D
f
α
=
=
相关PDF资料 |
PDF描述 |
|---|---|
| PM6670S | 3 A SWITCHING CONTROLLER, QCC24 |
| PM6670TR | 1.4 A SWITCHING CONTROLLER, QCC24 |
| PM6670ATR | 1.4 A SWITCHING CONTROLLER, QCC24 |
| PM6670 | 1.4 A SWITCHING CONTROLLER, QCC24 |
| PM6675ASTR | 3 A SWITCHING CONTROLLER, QCC24 |
相关代理商/技术参数 |
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| PM6670TR | 功能描述:直流/直流开关调节器 Complete DDR2/3 Mem Pwr supply controllr RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| PM6675 | 制造商:STMicroelectronics 功能描述: 制造商:STMicroelectronics 功能描述:LDO CNTRLR STDN 0.6V TO 3.3V/1.5V 24PIN VFQFPN - Rail/Tube |
| PM6675AS | 功能描述:DC/DC 开关控制器 DDR 2/3 Memory Pwr Cntrl RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| PM6675ASTR | 功能描述:低压差控制器 - LDO Complete DDR2/3 Mem Pwr supply controllr RoHS:否 制造商:Micrel 最大输入电压:5.5 V 输出电压:Adjustable 输出电流:10 mA 负载调节: 输出类型:Adjustable, Fixed 输出端数量:1 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOT-23-6 |
| PM6675ATR | 功能描述:低压差控制器 - LDO High eff SD CNRL RoHS:否 制造商:Micrel 最大输入电压:5.5 V 输出电压:Adjustable 输出电流:10 mA 负载调节: 输出类型:Adjustable, Fixed 输出端数量:1 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOT-23-6 |
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