- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄374714 > SC1404 (Semtech Corporation) Mobile Multi-Output PWM Controller with Virtual Current Sense PDF資料下載
參數(shù)資料
| 型號： | SC1404 |
| 廠商： | Semtech Corporation |
| 英文描述： | Mobile Multi-Output PWM Controller with Virtual Current Sense |
| 中文描述： | 移動多輸出與虛擬PWM控制器電流檢測 |
| 文件頁數(shù)： | 18/27頁 |
| 文件大小： | 515K |
| 代理商： | SC1404 |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁第14頁第15頁第16頁第17頁當(dāng)前第18頁第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁
18
2003 Semtech Corp.
www.semtech.com
SC1404
PRELIMINARY
POWER MANAGEMENT
5V Start-up with slow Vin ramp.
Proper startup of the 5V output can be hampered by slow dV/dt on
the input. The SC1404 will power up and attempt to generate an
output when the input voltage exceeds 4.5 volts. If the input has
a slow dV/dt, the input voltage will not rise significantly during the
start-up sequence, leading to two conditions. First, the VL supply
can be hundreds of mV below 5V, since the input may not yet be
above 5V. Second, the duty cycle will be at maximum, leading to
very small off-times. These two conditions tend to reduce the
BOOST voltage; if continued indefinitely, the BOOST capacitor may
be unable to recharge fully, and eventually the high-side driver
loses its BOOST bias.
To avoid this the following steps should be taken:
1. If possible the dV/dt of the input supply should exceed .02V/
usec. This dV/dt condition only applies when the input passes
between 4 and 6 volts, the point at which the SC1404 begins a
startup sequence. An alternative is to make sure the input voltage
reaches 6 volts within 100 usec of SC1404 startup at
approximately 4.2 volts. This is sufficiently fast to allow VL and
duty cycle to achieve normal levels and will prevents the BOOST
voltage from falling.
2. If the dV/dt of the input cannot meet condition 1, the startup of
the SC1404 should be delayed until the input voltage reaches 6V.
This can be done using either the SHDN# or ON5 pin. If the dV/dt
is moderate (slews from 4 to 6 volts in several msecs), an RC
delay on either the SHDN# or ON5 pin should be enough to delay
turn-on until the input reaches 6V.
3. For slow dV/dt on the input (10’s of msec), the SC1404 should
be held off until the input reaches 6V. This can be done using a
comparator or external logic to hold the SHDN# or ON5 pin low
until the input reaches 6V.
12V Load Limitations
The 12V regulator derives input power from a secondary winding
on the 5V inductor. During the 5V off-time, the inductor transfers
energy from the 5V winding to the secondary winding, thereby
providing a crudely regulated 15V that feeds the 12V regulator.
Note that duty cycle increases at low input voltages, and therefore
the on-time decreases.
At low input voltages, the duty cycle increases to maintain the 5V
output. The off-time consequently decreases, which has two
detrimental effects. It allows less time to recharge the raw 15V
capacitor, and it also raises the peak 15V current required to
maintain the average 12V load. The 15V winding needs higher
peak current, delivered in less time. But the stray (leakage)
inductance of the inductor resists rapid changes in winding current,
and ultimately limits how much current can be drawn from 15V
before the voltage falls.
e
g
n
a
n
s
n
n
o
o
n
c
d
a
o
V
V
2
1
>
V
0
1
d
a
a
o
o
V
2
1
V
2
1
<
d
a
x
a
o
m
V
5
A
*
m
0
0
2
2
/
1
=
d
V
0
1
-
V
7
d
a
o
y
e
V
2
n
1
<
d
0
0
1
d
:
a
a
o
o
V
V
7
V
V
0
5
2
1
*
2
/
1
1
e
m
0
m
0
t
t
A
A
2
V
7
-
V
6
d
a
o
y
e
1
V
2
n
1
<
d
m
m
d
:
a
a
o
o
V
V
5
2
V
0
1
V
7
*
2
/
1
1
e
t
A
t
A
0
5
0
2
The following guidelines for 12V loading apply to the typical
circuit, page 22.
PSAVE operation
The SC1404 enters power-save operation if the load is sufficiently
light, and if PSAVE is tied low. In PSAVE operation, the switching
frequency is no longer fixed, and the converter operates as a
hysteretic converter. This reduces gate drive losses and other
switching losses to improve efficiency. Each converter willl enter
or exit PSAVE operation independently, based on load current. The
hysteresis (output ripple) on the 5V output is typically 70mV, and
the 3V hysteresis is typically 35mV.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SC1404ISSTR | Mobile Multi-Output PWM Controller with Virtual Current Sense |
| SC1404ITSTR | Mobile Multi-Output PWM Controller with Virtual Current Sense |
| SC1405B | HIGH SPEED SYNCHRONOUS POWER MOSFET SMART DRIVER |
| SC1405BTS.TR | High Speed Synchronous Power MOSFET Smart Driver |
| SC1405D | Differential Input, Dual, Simultaneous Sampling, 4.25 MSPS, 14-Bit, SAR ADC, 16-TSSOP, Auto Temp |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SC1404_05 | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Mobile Multi-Output PWM Controller with Virtual Current SenseTM |
| SC1404ISSTR | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Mobile Multi-Output PWM Controller with Virtual Current SenseTM |
| SC1404ITSTR | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Mobile Multi-Output PWM Controller with Virtual Current SenseTM |
| SC1405 | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:HIGH SPEED SYNCHRONOUS POWER MOSFET SMART DRIVER |
| SC1405B | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:HIGH SPEED SYNCHRONOUS POWER MOSFET SMART DRIVER |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。