- 您現在的位置：買賣IC網 > PDF目錄98003 > LTC3728LZEUH (LINEAR TECHNOLOGY CORP) 3 A DUAL SWITCHING CONTROLLER, 590 kHz SWITCHING FREQ-MAX, PQCC28 PDF資料下載
參數資料
| 型號： | LTC3728LZEUH |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 3 A DUAL SWITCHING CONTROLLER, 590 kHz SWITCHING FREQ-MAX, PQCC28 |
| 封裝： | 5 X 5 MM, PLASTIC, MO-220WHHD, QFN-28 |
| 文件頁數： | 11/32頁 |
| 文件大?。?/td> | 467K |
| 代理商： | LTC3728LZEUH |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁當前第11頁第12頁第13頁第14頁第15頁第16頁第17頁第18頁第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁第28頁第29頁第30頁第31頁第32頁
LTC3728LZ
19
3728lzf
Since VOSENSE is servoed to the 0.8V reference voltage,
we can choose R1 in Figure 2 to have a maximum value
to absorb this current.
Rk
V
VV
MAX
OUT
124
08
24
()
.
.–
=
for VOUT < 2.4V
Regulating an output voltage of 1.8V, the maximum value
of R1 should be 32k. Note that for an output voltage above
2.4V, R1 has no maximum value necessary to absorb
the sense currents; however, R1 is still bounded by the
VOSENSE feedback current.
Soft-Start/Run Function
The RUN/SS1 and RUN/SS2 pins are multipurpose pins that
provide a soft-start function and a means to shut down the
LTC3728LZ. Soft-start reduces the input power source’s
surge currents by gradually increasing the controller’s
current limit (proportional to VITH). This pin can also be
used for power supply sequencing.
An internal 1.2μA current source charges up the CSScapaci-
tor. When the voltage on RUN/SS1 (RUN/SS2) reaches 1.5V,
the particular controller is permitted to start operating. As
the voltage on RUN/SS increases from 1.5V to 3.0V, the
internal current limit is increased from 25mV/RSENSE to
75mV/RSENSE. The output current limit ramps up slowly,
taking an additional 1.25s/μF to reach full current. The
output current thus ramps up slowly, reducing the start-
ing surge current required from the input power supply.
If RUN/SS has been pulled all the way to ground there is
a delay before starting of approximately:
t
V
A
Cs
F C
DELAY
SS
=
=
()
15
12
125
.
./
t
VV
A
Cs
F C
IRAMP
SS
=
=
()
31 5
12
125
.
./
By pulling both RUN/SS pins below 1V, the IC is put into
low current shutdown (IQ = 20μA). The RUN/SS pins
can be driven directly from logic as shown in Figure 7.
Diode D1 in Figure 7 reduces the start delay but allows
CSS to ramp up slowly providing the soft-start function.
Each RUN/SS pin has an internal 6V zener clamp (See
Functional Diagram).
Fault Conditions: Overcurrent Latchoff
The RUN/SS pins also provide the ability to latch off the
controller(s) when an overcurrent condition is detected.
The RUN/SS capacitor, CSS, is used initially to turn on
and limit the inrush current. After the controller has been
started and been given adequate time to charge up the
output capacitor and provide full load current, the RUN/SS
capacitor is used for a short-circuit timer. If the regulator’s
output voltage falls to less than 70% of its nominal value
after CSS reaches 4.1V, CSS begins discharging on the as-
sumption that the output is in an overcurrent condition. If
the condition lasts for a long enough period as determined
by the size of the CSS and the specied discharge current,
the controller will be shut down until the RUN/SS pin volt-
age is recycled. If the overload occurs during start-up, the
time can be approximated by:
tLO1 ≈ [CSS(4.1 – 1.5 + 4.1 – 3.5)]/(1.2μA)
= 2.7 106 (CSS)
If the overload occurs after start-up the voltage on CSS will
begin discharging from the zener clamp voltage:
tLO2 ≈ [CSS (6 – 3.5)]/(1.2μA) = 2.1 10
6 (CSS)
This built-in overcurrent latchoff can be overridden by
providing a pull-up resistor to the RUN/SS pin as shown
in Figure 7. This resistance shortens the soft-start period
and prevents the discharge of the RUN/SS capacitor during
an over current condition. Tying this pull-up resistor to
VIN, as in Figure 7a, defeats overcurrent latchoff.
Figure 7. RUN/SS Pin Interfacing
3.3V OR 5V
RUN/SS
VIN
RUN/SS
D1
CSS
RSS*
CSS
3728LZ F07
(a)
(b)
*OPTIONAL TO DEFEAT OVERCURRENT LATCHOFF
APPLICATIONS INFORMATION
相關PDF資料 |
PDF描述 |
|---|---|
| LTC3773EUHF | SWITCHING CONTROLLER, 700 kHz SWITCHING FREQ-MAX, PQCC38 |
| LTC3773EG | SWITCHING CONTROLLER, 700 kHz SWITCHING FREQ-MAX, PDSO36 |
| LTC3801ES6#PBF | 1 A SWITCHING CONTROLLER, 650 kHz SWITCHING FREQ-MAX, PDSO6 |
| LTC3803ES6-3 | 1 A SWITCHING CONTROLLER, 330 kHz SWITCHING FREQ-MAX, PDSO6 |
| LTC3803IS6-3 | 1 A SWITCHING CONTROLLER, 330 kHz SWITCHING FREQ-MAX, PDSO6 |
相關代理商/技術參數 |
參數描述 |
|---|---|
| LTC3728LZEUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標準包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數: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 |
| LTC3728LZEUH#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標準包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數: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 |
| LTC3729EG | 功能描述:IC REG CTRLR BUCK PWM CM 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:PolyPhase® 標準包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數: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 |
| LTC3729EG#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 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:PolyPhase® 特色產品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標準包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數: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® 產品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
| LTC3729EG#PBF-ND | 制造商: 功能描述: 制造商:undefined 功能描述: |
發(fā)布緊急采購，3分鐘左右您將得到回復。