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參數(shù)資料
| 型號： | LTC1873EG |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Quadruple 2-Input Positive-AND Gate 14-TSSOP -40 to 85 |
| 中文描述： | 5 A SWITCHING CONTROLLER, 750 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封裝： | 0.209 INCH, PLASTIC, SSOP-28 |
| 文件頁數(shù)： | 12/32頁 |
| 文件大?。?/td> | 308K |
| 代理商： | LTC1873EG |
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12
LTC1873
Each RUN/SS pin shuts down its half of the LTC1873 when
it falls below about 0.5V (Figure 4). Between 0.5V and
about 1V, that half is active, but the maximum duty cycle
is limited to 10%. The maximum duty cycle limit increases
linearly between 1V and 2.5V, reaching its final value of
90% when RUN/SS is above 2.5V. Somewhere before this
point, the feedback amplifier will assume control of the
loop and the output will come into regulation. When RUN/
SS rises to 0.5V below V
CC
, the MIN feedback comparator
is enabled, and the LTC1873 is in full operation.
CURRENT LIMIT
The LTC1873 includes an onboard current limit circuit that
limits the maximum output current to a user-programmed
level. It works by sensing the voltage drop across QB
during the time that QB is on and comparing that voltage
to a user-programmed voltage at I
MAX
. Since QB looks like
a low value resistor during its on-time, the voltage drop
across it is proportional to the current flowing in it. In a
buck converter, the average current in the inductor is equal
to the output current. This current also flows through QB
during its on-time. Thus, by watching the voltage across
QB, the LTC1873 can monitor the output current.
Any time QB is on and the current flowing to the output is
reasonably large, the SW node at the drain of QB will be
somewhat negative with respect to PGND. The LTC1873
senses this voltage and inverts it to allow it to compare the
sensed voltage with a positive voltage at the I
MAX
pin. The
I
MAX
pin includes a trimmed 10
μ
A pull-up, enabling the
user to set the voltage at I
MAX
with a single resistor, R
IMAX
,
to ground. The LTC1873 compares the two inputs and
begins limiting the output current when the magnitude of
the negative voltage at the SW pin is greater than the
voltage at I
MAX
.
The current limit detector is connected to an internal g
m
amplifier that pulls a current from the RUN/SS pin propor-
tional to the difference in voltage magnitudes between the
SW and I
MAX
pins. This current begins to discharge the
soft-start capacitor at RUN/SS, reducing the duty cycle
and controlling the output voltage until the current drops
below the limit. The soft-start capacitor needs to move a
fair amount before it has any effect on the duty cycle,
adding a delay until the current limit takes effect (Figure 4).
This allows the LTC1873 to experience brief overload
conditions without affecting the output voltage regulation.
The delay also acts as a pole in the current limit loop to
2.5V
2.5V
1.0V
0V
5V
0V
V
OUT
V
RUN/SS
4.5V
RUN/SS CONTROLS
DUTY CYCLE
MIN COMPARATOR ENABLED
RUN/SS CONTROLS
DUTY CYCLE
START-UP
NORMAL OPERATION
CURRENT LIMIT
1873 F04
COMP CONTROLS DUTY CYCLE
LTC1873 ENABLED
0.5V
Figure 4. Soft-Start Operation in Start-Up and Current Limit
APPLICATIOU
W
U
U
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC1873EG#PBF | 功能描述:IC REG CTRLR BUCK PWM VM 28-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:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 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:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC1873EG#TR | 功能描述:IC REG CTRLR BUCK PWM VM 28-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:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 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:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC1873EG#TRPBF | 功能描述:IC REG CTRLR BUCK PWM VM 28-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:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 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:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC1874EGN | 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) |
| LTC1874EGN#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:2,500 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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