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参数资料
| 型号： | LX1673-06CLQ-TR |
| 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： | ROHS COMPLIANT, PLASTIC, MLPQ-20 |
| 文件页数： | 2/13页 |
| 文件大小： | 286K |
| 代理商： | LX1673-06CLQ-TR |
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 10
Copyright
2004
Rev 1.0, 3/18/2005
WWW
.Microse
m
i
.CO
M
LX1673
High Frequency PWM Regulator
PRODUCTION DATA SHEET
TM
APPLICATION NOTE ( C ONTINU E D )
The SS pin voltage can be expressed as:
(
)
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 0.1f 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)):
K
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 (50A 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.
OUTPUT DISABLE
The LX1673 PWM MOSFET driver outputs are shut off by
pulling the disable (DIS) pin above 1.2V. There is a
80K
pull
down resistor on this input.
The LDO voltage regulator has its own Disable pin (LDDIS) for
control of this output voltage. Pulling this pin above 3 V disables
the LDO. There is a
100K
pull down resistor on this input.
PROGRAMMING THE OUTPUT VOLTAGE
The output Voltage is sensed by the feedback pin (FBX) which is
compared to a 0.8V reference. The output voltage can be set to any
voltage above 0.8V (and lower than the input voltage) by means of
a resistor divider (see Figure 1).
)
/R
R
(1
V
2
1
REF
OUT
+
=
Note: This equation is simplified and does not account for error
amplifier input current. Keep R1 and R2 close to
1K (order of
magnitude).
DDR VTT TERMINATION VOLTAGE
Double Data Rate (DDR) SDRAM requires a termination
voltage (VTT) in addition to the line driver supply voltage (VDDQ)
and receiver supply voltage (VDD).
VTT for DDR memory can be generated with the LX1673 by
using the positive input of the phase 2 error amplifier RF2 as a
reference input from an external reference voltage VREF which is
defined as one half of VDDQ. Using VREF as the reference input
will insure that all voltages are correct and track each other as
specified in the JEDEC (EIA/JESD8-9A) specification. The phase 2
output will then be equal to VREF and track the VDDQ supply as
required.
When an external reference is used the connection between the
error amplifier positive input and the Soft Start pin is lost and Soft
Start will not function. It is recommended that the external
reference voltage have an R-C time constant that will be long
enough to allow the output capacitor to charge slowly.
See Microsemi Application Note 17 for more details
AA
PP
LL
IICC
AA
TT
IIOO
NN
SS
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 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 |
| LX1673-09CLQ | 功能描述:IC REG DL BCK/LINEAR SYNC 20MLPQ RoHS:是 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（2），线性（LDO）（1） 功能:任何功能 输出数:3 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:4.5 V ~ 24 V 工作温度:-40°C ~ 85°C 安装类型:* 封装/外壳:28-TSSOP（0.173"，4.40mm 宽） 供应商设备封装:* 包装:带卷 (TR) 其它名称:ISL6402IVZ-TTR |
| LX1673-09CLQ-TR | 制造商:Microsemi Corporation 功能描述:VOLT MODE PWM CNTRLR 0.8V TO 5.5V 1A 20MLPQ - Tape and Reel |
| LX1673-09CPW | 功能描述:IC REG DL BCK/LINEAR 20TSSOP RoHS:是 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（2），线性（LDO）（1） 功能:任何功能 输出数:3 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:4.5 V ~ 24 V 工作温度:-40°C ~ 85°C 安装类型:* 封装/外壳:28-TSSOP（0.173"，4.40mm 宽） 供应商设备封装:* 包装:带卷 (TR) 其它名称:ISL6402IVZ-TTR |
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