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参数资料
| 型号： | LT1572CS |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 100kHz, 1.25A Switching Regulator with Catch Diode |
| 中文描述： | 1.25 A SWITCHING REGULATOR, 100 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | 0.150 INCH, PLASTIC, SO-16 |
| 文件页数： | 8/12页 |
| 文件大小： | 257K |
| 代理商： | LT1572CS |
8
LT1572
OPERATIOU
to the comparator input. The LT1572 will then regulate the
value of the flyback pulse with respect to the supply
voltage.
1
This flyback pulse is directly proportional to
output voltage in the traditional transformer coupled flyback
topology regulator. By regulating the amplitude of the
flyback pulse, the output voltage can be regulated with no
direct connection between input and output. The output is
fully floating up to the breakdown voltage of the trans-
former windings. Multiple floating outputs are easily ob-
tained with additional windings. A special delay network
inside the LT1572 ignores the leakage inductance spike at
the leading edge of the flyback pulse to improve output
regulation.
The error signal developed at the comparator input is
brought out externally. This pin (V
C
) has four different
functions. It is used for frequency compensation, current
limit adjustment, soft starting, and total regulator shut-
down. During normal regulator operation this pin sits at a
voltage between 0.9V (low output current) and 2.0V (high
output current). The error amplifiers are current output
(g
m
) types, so this voltage can be externally clamped for
adjusting current limit. Likewise, a capacitor coupled
external clamp will provide soft start. Switch duty cycle
goes to zero if the V
C
pin is pulled to ground through a
diode, placing the LT1572 in an idle mode. Pulling the V
C
pin below 0.15V causes total regulator shutdown, with
only 50
μ
A supply current for shutdown circuitry biasing.
See AN19 for full application details.
E1 and E2 Pins
The LT1572 has the emitters of the power transistor
brought out separately from the ground pin. This elimi-
nates errors due to ground pin voltage drops and allows
the user to reduce switch current limit 2:1 by leaving the
second emitter (E2) disconnected. The first emitter (E1)
should always be connected to the ground pin. Note that
switch “on” resistance doubles when E2 is left open, so
efficiency will suffer somewhat when switch currents
exceed 300mA. Also, note that chip dissipation will actu-
ally increasewith E2 open during normal load operation,
even though dissipation in current limit mode will de-
crease
1
See note under block diagram.
Other Application Help
More circuits and application help for the LT1572 can be
found in the LT1172 data sheet, both in loose form and in
the 1994 Linear Databook Volume III Extensive additional
help is contained in Application Note 19. All application
circuits using the LT1172 can also use the LT1572 as long
as the 20V maximum reverse voltage of the diode is not
exceeded. A CAD program called SwitcherCAD is also
available. This program can be used with the LT1572 by
simply treating the LT1572 as an LT1172 and ignoring the
predicted die temperature results obtained from
SwitcherCAD itself.
Thermal Management
Thermal management is particularly important with the
LT1572 because both switch and diode power dissipation
increase rapidly at low input voltage when using the
popular boost topology. Regulator and diode die tempera-
ture must be calculated separatelybecause they are not
connected to an isothermal plane inside the package.
Diode plusregulator thermal resistance is approximately
70
°
C/W when the LT1572 is soldered to 1oz copper traces
over an internal or backside copper plane using FR4 board
material. However, individual calculation of die tempera-
ture must take thermal coupling into account. To accom-
plish this, thermal resistance is broken into two sections,
a common (coupled) section and a second uncoupled
section. Die temperatures are calculated from:
T
REG
= T
A
+ P
REG
(90
°
C/W) + P
DIODE
(45
°
C/W)
T
DIODE
= T
A
+ P
DIODE
(90
°
C/W) + P
REG
(45
°
C/W)
T
A
= ambient temperature
T
REG
= regulator die temperature
T
DIODE
= diode die temperature
P
REG
= total regulator power dissipation
P
DIODE
= diode power dissipation
The following formulas can be used as a rough guide to
calculate LT1572 power dissipation. For more details, the
reader is referred to Application Note 19 (AN19), “Effi-
ciency Calculations” section.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1572CS#PBF | 功能描述:IC REG MULTI CONFIG 1.25A 16SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT1572CS#TR | 功能描述:IC REG MULTI CONFIG 1.25A 16SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT1572CS#TRPBF | 功能描述:IC REG MULTI CONFIG 1.25A 16SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT1573 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Low Dropout PNP Regulator Driver |
| LT-1573-111-024 | 制造商:Carling Technologies 功能描述:LT-SERIES TOGGLE SWITCH - Bulk |
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