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参数资料
| 型号： | L6996DTR |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO24 |
| 封装： | MO-153AD, TSSOP-24 |
| 文件页数： | 2/26页 |
| 文件大小： | 272K |
| 代理商： | L6996DTR |
L6996
10/26
1
DEVICE DESCRIPTION
1.1 Constant On Time PWM Topology
Figure 12. Loop block schematic diagram
This device implements a Constant On Time control, where the Ton is the on time duration forced by a one-shot
circuit. The controller calculates the one-shot time directly proportional to the VCS- pin voltage and inversely to
the OSC pin voltage as in Eq 1:
Eq 1
where KOSC=180ns and τ is the internal propagation delay time (Typ. 40ns). The system imposes in steady
state a minimum on time corresponding to VOSC = 2V. In fact if the VOSC voltage increases above 2V the cor-
responding Ton will not decrease. Connecting OSC pin to a voltage partition from VIN to GND, it allows steady-
state switching frequency FSW independent of VIN. It results:
Eq 2
where
Eq 3
The above equations allow setting the frequency divider ratio aOSC once output voltage has been set; note that
such equations hold only if VOSC<2.A minimum off-time constrain of about 500nS is introduced in order to as-
sure the boot capacitor charge and to limit switching frequency after a load transient as well as to mask PWM
comparator output against switching noise and spikes.
The system has not an internal clock, because this is a hysteretic controller, so the turn on pulse will start if three
Q
Vprog
LS
HS
VFB+
DS
CS-
VID0-4
Rsense
R1
R
S
Vout
Vin
HGATE
LGATE
Q
R2
PWM comparator
VFB-
FFSR
One-shot generator
OSC
-
+
-
DAC
T
ON
K
OS C
V
CS -
V
OS C
---------------
τ
+
=
F
SW
V
OU T
V
IN
---------------
1
T
ON
-----------
α
OS C
→
F
SW KOS C
==
α
OS C
V
OS C
V
IN
---------------
R
2
R
2
R
1
+
--------------------
==
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相关代理商/技术参数 |
参数描述 |
|---|---|
| L6997 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:STEP DOWN CONTROLLER FOR LOW VOLTAGE OPERATIONS |
| L6997-28 | 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT |
| L6997-5 | 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT; Accessory Type:Tuning Element; For Use With:High Quality Variable Reactance Tuning Microwave Cavities, Filters & other Resonant Structures |
| L6997-9 | 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT |
| L6997D | 功能描述:DC/DC 开关控制器 Adjustable Step-Down 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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