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參數(shù)資料
| 型號： | LTC1735CGN-1 |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| 中文描述： | 3 A SWITCHING CONTROLLER, 550 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 0.150 INCH, PLASTIC, SSOP-16 |
| 文件頁數(shù)： | 10/32頁 |
| 文件大?。?/td> | 373K |
| 代理商： | LTC1735CGN-1 |
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10
LTC1735
Foldback Current, Short-Circuit Detection and
Short-Circuit Latchoff
The RUN/SS capacitor, C
SS
, is used initially to limit the
inrush current of the switching regulator. After the con-
troller has been started and been given adequate time to
charge up the output capacitors and provide full load cur-
rent, C
SS
is used as a short-circuit time-out circuit. If the
output voltage falls to less than 70% of its nominal output
voltage, C
SS
begins discharging on the assumption that
the output is in an overcurrent and/or short-circuit condi-
tion. If the condition lasts for a long enough period as
determined by the size of C
SS
, the controller will be shut
down until the RUN/SS pin voltage is recycled. This built-
in latchoff can be overridden by providing a current >5
μ
A
at a compliance of 5V to the RUN/SS pin. This current
shortens the soft-start period but also prevents net dis-
charge of C
SS
during an overcurrent and/or short-circuit
condition. Foldback current limiting is activated when the
output voltage falls below 70% of its nominal level whether
or not the short-circuit latchoff circuit is enabled.
INTV
CC
/EXTV
CC
POWER
Power for the top and bottom MOSFET drivers and most
of the internal circuitry of the LTC1735 is derived from the
INTV
CC
pin. When the EXTV
CC
pin is left open, an internal
5.2V low dropout regulator supplies the INTV
CC
power
from V
IN
. If EXTV
CC
is raised above 4.7V, the internal
regulator is turned off and an internal switch connects
EXTV
CC
to INTV
CC
. This allows a high efficiency source,
such as the primary or a secondary output of the converter
itself, to provide the INTV
CC
power. Voltages up to 7V can
be applied to EXTV
CC
for additional gate drive capability.
To provide clean start-up and to protect the MOSFETs,
undervoltage lockout is used to keep both MOSFETs off
until the input voltage is above 3.5V.
OPERATIOU
(Refer to Functional Diagram)
APPLICATIU
W
U
U
The basic LTC1735 application circuit is shown in Figure1
on the first page. External component selection is driven
by the load requirement and begins with the selection of
R
SENSE
. Once R
SENSE
is known, C
OSC
and L can be chosen.
Next, the power MOSFETs and D1 are selected. The
operating frequency and the inductor are chosen based
largely on the desired amount of ripple current. Finally, C
IN
is selected for its ability to handle the large RMS current
into the converter and C
OUT
is chosen with low enough
ESR to meet the output voltage ripple and transient speci-
fications. The circuit shown in Figure 1 can be configured
for operation up to an input voltage of 28V (limited by the
external MOSFETs).
R
SENSE
Selection for Output Current
R
SENSE
is chosen based on the required output current.
The LTC1735 current comparator has a maximum thresh-
old of 75mV/R
SENSE
and an input common mode range of
SGND to 1.1(INTV
CC
). The current comparator threshold
sets the peak of the inductor current, yielding a maximum
average output current I
MAX
equal to the peak value less
half the peak-to-peak ripple current,
I
L
.
Allowing a margin for variations in the LTC1735 and
external component values yields:
R
mV
I
SENSE
MAX
=
50
C
OSC
Selection for Operating Frequency and
Synchronization
The choice of operating frequency and inductor value is a
trade-off between efficiency and component size. Low
frequency operation improves efficiency by reducing
MOSFET switching losses, both gate charge loss and
transition loss. However, lower frequency operation re-
quires more inductance for a given amount of ripple
current.
The LTC1735 uses a constant frequency architecture with
the frequency determined by an external oscillator capaci-
tor C
OSC
. Each time the topside MOSFET turns on, the
voltage on C
OSC
is reset to ground. During the on-time,
C
OSC
is charged by a fixed current. When the voltage on the
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相關(guān)代理商/技術(shù)參數(shù) |
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|---|---|
| LTC1735CGN-1#25121 | 制造商:Linear Technology 功能描述: |
| LTC1735CGN-1#25121#TR | 制造商:Linear Technology 功能描述: |
| LTC1735CGN-1#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:2,000 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:50% 電源電壓:9 V ~ 10 V 降壓:無 升壓:是 回掃:是 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:8-TSSOP（0.173"，4.40mm 寬） 包裝:帶卷 (TR) |
| LTC1735CGN-1#TR | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC1735CGN-1#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
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