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| 型号： | PM6675S |
| 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： | 13/53页 |
| 文件大小： | 2632K |
| 代理商： | PM6675S |
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Device description
PM6675S
20/53
7.1
Switching section - constant on-time PWM controller
The PM6675S employes a pseudo-fixed frequency, Constant On-Time (COT) controller as
the core of the switching section. It is well known that the COT controller uses a relatively
simple algorithm and uses the ripple voltage derived across the output capacitor ESR to
trigger the On-Time one-shot generator. In this way, the output capacitor ESR acts as a
current sense resistor providing the appropriate ramp signal to the PWM comparator.
Nearly constant switching frequency is achieved by the system 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,
detected by theVSNS pin, and inversely proportional to the input voltage, detected by the
the VOSC pin, as follows:
Equation 1
where KOSC is a constant value (130 ns typ.) and τ is the internal propagation delay
(40ns typ.). The one-shot generator directly drives the high-side MOSFET at the beginning
of each switching cycle allowing the inductor current to increase; after the On-Time has
expired, an Off-Time phase, in which the low-side MOSFET is turned on, follows. The Off-
Time duration is solely determined by the output voltage: when lower than the set value (i.e.
the voltage at VSNS pin is lower than the internal reference VR = 0.6 V), the synchronous
rectifier is turned off and a new cycle begins (Figure 32).
Figure 32.
Inductor current and output voltage in steady state conditions
τ
+
=
OSC
SNS
OSC
ON
V
K
T
Ton
Toff
Inductor
current
t
Output
voltage
Vreg
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相关代理商/技术参数 |
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| PM6675STR | 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 |
| PM6675TR | 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 |
| PM6680 | 功能描述:DC/DC 开关控制器 No Rsense dual StepDwn Controller 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 |
| PM6680_08 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:No Rsense dual step-down controller with adjustable voltages for notebook system power |
| PM6680A | 功能描述:DC/DC 开关控制器 Dual sync controller 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 |
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