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參數(shù)資料
| 型號： | L6996D |
| 廠商： | STMICROELECTRONICS |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO24 |
| 封裝： | MO-153AD, TSSOP-24 |
| 文件頁數(shù)： | 2/26頁 |
| 文件大?。?/td> | 272K |
| 代理商： | L6996D |
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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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| L6996DTR | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:DINAMICALLY PROGRAMMABLE SYNCHRONOUS STEP DOWN CONTROLLER FOR MOBILE CPUs |
| L6997 | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:STEP DOWN CONTROLLER FOR LOW VOLTAGE OPERATIONS |
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| 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 |
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