- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄376345 > SG2526B (Microsemi Corporation) REGULATING PULSE WIDTH MODULATOR PDF資料下載
參數(shù)資料
| 型號： | SG2526B |
| 廠商： | Microsemi Corporation |
| 英文描述： | REGULATING PULSE WIDTH MODULATOR |
| 中文描述： | 調(diào)控脈寬調(diào)制器 |
| 文件頁數(shù)： | 6/9頁 |
| 文件大小： | 209K |
| 代理商： | SG2526B |
4/90 Rev 1.1 2/94
Copyright
1994
L
IN
F
IN
ITY
Microelectronics Inc.
11861 Western Avenue
∞
∞
Garden Grove, CA 92841
(714) 898-8121
∞
FAX: (714) 893-2570
6
SG1526B/SG2526B/SG3526B
FIGURE 19.
OSCILLATOR PERIOD VS. R
T
AND C
T
APPLICATION INFORMATION
CHARACTERISTIC CURVES
(continued)
VOLTAGE REFERENCE
The reference regulator of the SG1526B is a “band-gap” type; that is, the precision +5 volt
output is derived from the very predictable base-emitter voltage of an NPN transistor.
Since this is a sub-surface phenomenon, the resulting output exhibits excellent stability
compared to earlier surface-breakdown zener designs.
The reference output is stabilized at input voltages as low as +8 volts, and can provide
up to 20mA of load current to external circuitry. An external PNP transistor can be used
to boost the available current to many hundreds of mA. A rugged low-frequency audio-
type transistor should be used, and lead lengths between the PWM and transistor should
be as short as possible to minimize the risk of oscillation.
UNDERVOLTAGE LOCKOUT
The undervoltage lockout circuit protects the SG1526B and the power devices it controls
from inadequate supply voltage. If +V
is too low, the circuit disables the output drivers
and holds the RESET pin LOW. This prevents spurious output pulses while the control
circuitry is stabilizing, and holds the soft-start timing capacitor in a discharged state.
The circuit consists of a merged bandgap reference and comparator circuit which is
active when the reference voltage has risen to 2V
or 1.2 volts at 25
o
C. When the
reference voltage rises to approximately +4.4 volts, the circuit enables the output drivers
and releases the RESET pin, allowing a normal softstart. The comparator has 200mV
of hysteresis to minimize oscillation at the trip point. When +V
to the PWM is removed
and the reference drops to +4.2 volts, the undervoltage circuit pulls RESET LOW again.
The soft-start capacitor is immediately discharged, and the PWM is ready for another
soft-start cycle.
The SG1526B can operate from a +5 volt supply regulated to within ±4% by connecting
the V
REF
pin to the +V
IN
pin.
FIGURE 21.
SIMPLIFIED UNDERVOLTAGE LOCKOUT
The soft-start circuit protects the power transistors and rectifier diodes from high current
surges during power supply turn-on. When supply voltage is first applied to the
SG1526B, the undervoltage lockout circuit holds RESET LOW with Q3. Q1 is turned on,
which holds the soft-start capacitor voltage at zero. The second collector of Q1 clamps
the output of the error amplifier to ground, guaranteeing zero duty cycle at the driver
outputs. When the supply voltage reaches normal operating range, RESET will go HIGH.
Q1 turns off, allowing the internal 100
μ
A current source to charge C
. Q2 clamps the error
amplifier output to 1.0 V
above the voltage on C
. As the soft-start voltage ramps up
to +5 volts, the duty cycle of the PWM linearly increases to whatever value the voltage
regulation loop requires for an error null. Figure 7 gives the timing relationship between
C
S
ramp time to 100% duty cycle.
FIGURE 20.
EXTENDING REFERENCE OUTPUT CURRENT
FIGURE 22.
SOFT-START CIRCUIT SCHEMATIC
SOFT-START CIRCUIT
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SG2526BDW | REGULATING PULSE WIDTH MODULATOR |
| SG2526BJ | REGULATING PULSE WIDTH MODULATOR |
| SG2526BN | REGULATING PULSE WIDTH MODULATOR |
| SG1526 | REGULATING PULSE WIDTH MODULATOR |
| SG1526J | REGULATING PULSE WIDTH MODULATOR |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SG2526BDW | 功能描述:IC REG CTRLR BUCK PWM VM 18-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 特色產(chǎn)品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標(biāo)準(zhǔn)包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:81% 電源電壓:4.5 V ~ 18 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產(chǎn)品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
| SG2526BDW-12591 | 制造商:Microsemi Corporation 功能描述:REGULATING PULSE WIDTH MODULATOR - Tape and Reel |
| SG2526BDW-12900 | 制造商:Microsemi Corporation 功能描述:REGULATING PULSE WIDTH MODULATOR - Tape and Reel |
| SG2526BDW-TR | 制造商:Microsemi Corporation 功能描述:VOLT MODE PWM CNTRLR 100MA 18SOIC W - Tape and Reel |
| SG2526BJ | 制造商:Microsemi Corporation 功能描述:SG2526BJ - Bulk |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。