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参数资料
| 型号： | LX1673-06CLQT |
| 厂商： | MICROSEMI CORP-ANALOG MIXED SIGNAL GROUP |
| 元件分类： | 稳压器 |
| 英文描述： | 1 A SWITCHING CONTROLLER, 690 kHz SWITCHING FREQ-MAX, PQCC20 |
| 封装： | PLASTIC, MLPQ-20 |
| 文件页数： | 3/15页 |
| 文件大小： | 302K |
| 代理商： | LX1673-06CLQT |
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 11
Copyright
2000
Rev. 0.2j, 2002-07-17
WWW
.M
ic
ro
sem
i
.COM
LX1673
High Frequency PWM Regulator
PRELIMINARY
INTEGR A T E D
PR ODU C T S
APPLI CATION NOT E
APPLI CATION NOT E (CON T I NUE D)
(CON T I NUE D)
INPUT CAPACITOR
The input capacitor and the input inductor, if used, are to filter
the pulsating current generated by the buck converter to reduce
interference to other circuits connected to the same 5V rail. In
addition, the input capacitor provides local de-coupling for the
buck converter. The capacitor should be rated to handle the RMS
current requirements. The RMS current is:
d)
d(1
I
L
RMS
=
Where IL is the inductor current and d is the duty cycle. The
maximum value occurs when d = 50%, then IRMS =0.5IL. For a
5V input and output voltages in the range of 2 to 3V, the required
RMS current is very close to 0.5IL.
SOFT-START CAPACITOR
The value of the soft-start capacitor determines how fast the
output voltage rises and how large the inductor current is required
to charge the output capacitor. The output voltage will follow the
voltage at the SS pin if the required inductor current does not
exceed the maximum allowable current for the inductor. The SS
pin voltage can be expressed as:
(
)SS
SS
C
t/R
e
1
V
=
ref
Where RSS and CSS are the soft-start resistor and capacitor.
The current required to charge the output capacitor during the soft
start interval is.
dt
dVss
Cout
Iout
=
Taking the derivative with respect to time results in
SS
SS C
t/R
e
RssCss
VrefCout
Iout
=
and at t=0
RssCss
VrefCout
ax
Im
=
The required inductor current for the output capacitor to follow
the soft start voltage equals the required capacitor current plus the
load current.
The soft-start capacitor should be selected to
provide the desired power on sequencing and insure that the
overall inductor current does not exceed its maximum allowable
rating.
Values of Css equal to .1uf or greater are unlikely to result in
saturation of the output inductor unless very large output
capacitors are used.
OVER-CURRENT PROTECTION
Current limiting occurs at current level ICL when the voltage
detected by the current sense comparator is greater than the current
sense comparator threshold, VTRIP (300mV).
TRIP
SET
DS(ON)
CL
V
R
I
R
I
=
×
+
×
So,
A
50
R
I
mV
00
3
I
R
I
V
R
DS(ON)
CL
SET
DS(ON)
CL
TRIP
SET
×
=
×
=
Example:
For 10A current limit, using FDS6670A MOSFET (10m
RDS(ON)):
%
1
k
02
.
4
10
50
10
0.0
10
3
0.
R
6
SET
=
×
=
Note: Maximum RSET is 6K. Any resistor 6K or greater will not
allow startup since ICL will equal zero (50uA x 6K=300mV).
At higher PWM frequencies or low duty cycles where the upper
gate drive is less than 350nS wide the 350nS delay for current
limit enable may result in current pulses exceeding the desired
current limit set point. If the upper MOSFET on time is less than
350nS and a short circuit condition occurs the duty cycle will
increase, since Vout will be forced low. The current limit circuit
will be enabled when the upper gate drive exceeds 350nS although
the actual peak current limit value will be higher than calculated
with the above equation.
Short circuit protection still exists due to the narrow pulse width
even though the magnitude of the current pulses will be higher than
the calculated value.
If OCP is not desired connect both VSX and VCX to VCC. Do
not leave them floating.
AA
PP
LL
IICC
AA
TT
IIOO
NN
SS
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| LX1673-06CLQ-TR | 制造商:Microsemi Corporation 功能描述:VOLT MODE PWM CNTRLR 0.8V TO 5.5V 1A 20MLPQ - Tape and Reel |
| LX1673-06CPW | 功能描述:IC REG DL BCK/LINEAR 20TSSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 + 切换式 系列:- 标准包装:2,500 系列:- 拓扑:降压（降压）同步（3），线性（LDO）（2） 功能:任何功能 输出数:5 频率 - 开关:300kHz 电压/电流 - 输出 1:控制器 电压/电流 - 输出 2:控制器 电压/电流 - 输出 3:控制器 带 LED 驱动器:无 带监控器:无 带序列发生器:是 电源电压:5.6 V ~ 24 V 工作温度:-40°C ~ 85°C 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* |
| LX1673-06CPW-TR | 制造商:Microsemi Corporation 功能描述:VOLT MODE PWM CNTRLR 0.8V TO 5.5V 1A 20TSSOP - Tape and Reel |
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