- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄374732 > SC4905BIMSTR (Semtech Corporation) High Performance Voltage Mode PWM Controller PDF資料下載
參數(shù)資料
| 型號(hào)： | SC4905BIMSTR |
| 廠商： | Semtech Corporation |
| 英文描述： | High Performance Voltage Mode PWM Controller |
| 中文描述： | 高性能電壓模式PWM控制器 |
| 文件頁數(shù)： | 8/24頁 |
| 文件大?。?/td> | 378K |
| 代理商： | SC4905BIMSTR |
SC4905A/B
POWER MANAGEMENT
Application Information (Cont.)
2006 Semtech Corp.
www.semtech.com
8
VDD UNDER VOLTAGE LOCK OUT
According to the application, and the voltages available,
the SC4905A (UVLO = 4.4V), or the SC4905B (UVLO =
11.6V) can be used to provide the VDD undervoltage
lock out function to ensure the converters controlled
start up.
Before the VDD UVLO has been reached, the internal ref-
erence, oscillator, OUT driver, and logic are disabled.
REFERENCE
A 4V (SC4905A) or a 5V(SC4905B) reference voltage is
available that can be used to source a typical current
up to 5mA to the external circuitry. The REF can be used
to provide the feed back circuitry with a regulated bias.
OSCILLATOR
The oscillator frequency is set by connecting a RC network
as shown below.
U1
SC4905
4
5
3
2
10
1
6
7
8
9
DMAX
RC
VFF
FB
REF
VDD
SYNC
ILIM
GND
OUT
RB
8.25k
RT
280k
RM
2k
Rosc
499k
Cosc
220p, 16V
Vin
The oscillator has a ramp voltage that will track the volt-
age at the VFF pin (1.2V<VFF<3.6V). The oscillator peak
voltage is derived by charging the oscillator capacitor (Cosc)
to the VFF voltage via the oscillator resistor (Rosc). The
bias current to charge the Cosc is controlled by the Rosc.
Once the RC pin has reached the VFF voltage, the oscil-
lator ramp is discharged by an internal switch hence cre-
ating the triangle oscillator ramp.
Since the Rosc is referenced to the input supply voltage,
any variation in the supply is directly translated into a
variation in the duty cycle, while maintaining the fixed
frequency operation.
Following equation can be used to calculate the oscilla-
tor frequency:
(
)
05
.
VFF
C
R
2
VFF
Vin
F
OSC
OSC
OSC
The recommended range if timing resistors is between
10 kohm and 500kohm and range of timing capacitors
is between 100pF and 1000pF. Timing resistors less
than 10 kohm should be avoided.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SC4905BIMSTRT | High Performance Voltage Mode PWM Controller |
| SC4905A | High Performance Voltage Mode PWM Controller |
| SC4910A | High Performance Secondary Side Controller with Synchronous Rectifier |
| SC4910AITSTRT | High Performance Secondary Side Controller with Synchronous Rectifier |
| SC4910B | High Performance Secondary Side Controller with Synchronous Rectifier |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SC4905BIMSTRT | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:High Performance Voltage Mode PWM Controller |
| SC4905BMSTR | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:HIGH PERFORMANCE VOLTAGE MODE PWM CONTROLLER |
| SC490AULTRT | 制造商:Semtech Corporation 功能描述:I2C BUCK CONTRO |
| SC490BULTRT | 制造商:Semtech Corporation 功能描述:DCDC power |
| SC4910A | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:High Performance Secondary Side Controller with Synchronous Rectifier |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。