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| 型號(hào)： | LX1554CPW-TR |
| 廠商： | MICROSEMI CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1 A SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | ROHS COMPLIANT, PLASTIC, TSSOP-20 |
| 文件頁(yè)數(shù)： | 4/18頁(yè) |
| 文件大?。?/td> | 475K |
| 代理商： | LX1554CPW-TR |
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O
B
SO
LETE
PRO
D
UCT
NOT
RECOMMENDED
FOR
NEW
DESIGNS
ULTRA-LOW START-UP CURRENT, CURRENT-MODE PWM
LX1552/3/4/5
PRODUCT D A T ABOOK 1996/1997
Copyright 1994
Rev. 1.0b
12
P RODUCTIO N D ATA
S HEET
THEO R Y OF OPER A TION
IC DESCRIPTION
The LX1552/3/4/5 series of current mode PWM controller IC's are
designed to offer substantial improvements in the areas of start-
up current and oscillator accuracy when compared to the first
generation products, the UC184x series. While they can be used
in most DC-DC applications, they are optimized for single-ended
designs such as Flyback and Forward converters. The LX1552/
54 series are best suited for off-line applications, whereas the
1553/55 series are mostly used in power supplies with low input
voltages. The IC can be divided into six main sections as shown
in the Block Diagram (page 4): undervoltage lockout and start-
up circuit; voltage reference; oscillator; current sense comparator
and PWM latch; error amplifier; and the output stage.
The
operation of each section is described in the following sections.
The differences between the members of this family are summa-
rized in Table 1.
The start-up capacitor (C1) is charged by current through resistor
(R1) minus the start-up current. Resistor (R1) is designed such
that it provides more than 250A of current (typically 2x I
ST(max) ).
Once this voltage reaches the start-up threshold, the IC turns on,
starting the switching cycle.
This causes an increase in IC
operating current, resulting in discharging the start-up capacitor.
During this time, the auxiliary winding flyback voltage gets
rectified & filtered via (D1) and (C1) and provides sufficient
voltage to continue to operate the IC and support its required
supply current. The start-up capacitor must be large enough such
that during the discharge period, the bootsrap voltage exceeds
the shutdown threshold of the IC.
Table 2 below shows a comparison of start-up resistor power
dissipation vs. maximum start-up current for different devices.
Max. Start-up Current
Specification (I
ST)
Typical Start-Up
Resistor Value (R
ST)
Max. Start-Up Resistor
Power Dissipation (P
R)
Design Using
SG384x
UC384xA
LX155x
2.26W
1.13W
0.56W
62K
124K
248K
1000A
500A
250A
(Resistor R1 is designed such that it provides 2X maximum
start-up current under low line conditions.
Maximum power
dissipation is calculated under maximum line conditions. Ex-
ample assumes 90 to 265VAC universal input application.)
FIGURE 23 — TYPICAL APPLICATION OF START-UP CIRCUITRY
UNDERVOLTAGE LOCKOUT
The LX155x undervoltage lock-out is designed to maintain an
ultra low quiescent current of less than 250A, while guarantee-
ing the IC is fully functional before the output stage is activated.
Comparing this to the SG384x series, a 4x reduction in start-up
current is achieved resulting in 75% less power dissipation in the
start-up resistor. This is especially important in off-line power
supplies which are designed to operate for universal input
voltages of 90 to 265V AC.
Figure 23 shows an efficient supply voltage using the ultra low
start-up current of the LX1554 in conjunction with a bootstrap
winding off of the power transformer. Circuit operation is as
follows.
Hysterises Voltage
(V
HYS)
PART #
Start-up Voltage
(V
ST)
LX1552
LX1553
LX1554
LX1555
16V
8.4V
16V
8.4V
6V
0.8V
6V
0.8V
<100%
<50%
UVLO
MAXIMUM
DUTY CYCLE
TABLE 1
R
S
GND
DC BUS
C
1
D
1
I
1 > 250A
1
ST < 250A
V
IN
REF
R
T/CT
V
O
GND
R
T
C
T
LX1554
TABLE 2
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LX1554ID | 功能描述:IC REG CTRLR PWM CM 14-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| LX1554IDM | 功能描述:IC REG CTRLR BST FLYBK ISO 8SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| LX1554IM | 功能描述:IC REG CTRLR BST FLYBK ISO 8-DIP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| LX1554MY | 功能描述:IC REG CTRLR BST FLYBK ISO 8-DIP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| LX1555 | 制造商:MICROSEMI 制造商全稱:Microsemi Corporation 功能描述:ULTRA-LOW START-UP CURRENT, CURRENT-MODE PWM |
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