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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： | 14/54页 |
| 文件大小： | 742K |
| 代理商： | PM6670STR |
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PM6670S
Device description
Doc ID 14432 Rev 4
21/54
7.1
VDDQ section - constant on-time PWM controller
The PM6670S uses 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’s ESR to trigger
the on-time one-shot generator. In this way, the output capacitor’s 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’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 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 = 0.9 V), the synchronous rectifier is turned
off and a new cycle begins (Figure 28).
Figure 28.
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
Ton
Toff
Inductor
current
t
Output
voltage
Vreg
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| PM6670S | 3 A SWITCHING CONTROLLER, QCC24 |
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| PM6670 | 1.4 A SWITCHING CONTROLLER, QCC24 |
| PM6675ASTR | 3 A SWITCHING CONTROLLER, QCC24 |
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| 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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