- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄377763 > LTC1772 (Linear Technology Corporation) Constant Frequency Current Mode Step-Down DC/DC Controller in SOT-23 PDF資料下載
參數(shù)資料
| 型號： | LTC1772 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | Constant Frequency Current Mode Step-Down DC/DC Controller in SOT-23 |
| 中文描述： | 恒定頻率電流模式降壓DC / DC控制器，采用SOT - 23 |
| 文件頁數(shù)： | 5/16頁 |
| 文件大小： | 188K |
| 代理商： | LTC1772 |
5
LTC1772
OPERATIOU
up, the corre
sponding output current trip level follows,
allowing normal operation.
Comparator OVP guards against transient overshoots
>7.5% by turning off the external P-channel power
MOSFET and keeping it off until the fault is removed.
(Refer to Functional Diagram)
Burst Mode Operation
The LTC1772 enters Burst Mode operation at low load
currents. In this mode, the peak current of the inductor is
set as if V
ITH
/RUN = 1V (at low duty cycles) even though
the voltage at the I
TH
/RUN pin is at a lower value. If the
inductor’s average current is greater than the load require-
ment, the voltage at the I
TH
/RUN pin will drop. When the
I
TH
/RUN voltage goes below 0.85V, the sleep signal goes
high, turning off the external MOSFET. The sleep signal
goes low when the I
TH
/RUN voltage goes above 0.925V
and the LTC1772 resumes normal operation. The next
oscillator cycle will turn the external MOSFET on and the
switching cycle repeats.
Dropout Operation
When the input supply voltage decreases towards the
output voltage, the rate of change of inductor current
during the ON cycle decreases. This reduction means that
the external P-channel MOSFET will remain on for more
than one oscillator cycle since the inductor current has not
ramped up to the threshold set by EAMP. Further reduc-
tion in input supply voltage will eventually cause the
P-channel MOSFET to be turned on 100%, i.e., DC. The
output voltage will then be determined by the input voltage
minus the voltage drop across the MOSFET, the sense
resistor and the inductor.
Undervoltage Lockout
To prevent operation of the P-channel MOSFET below safe
input voltage levels, an undervoltage lockout is incorpo-
rated into the LTC1772. When the input supply voltage
drops below approximately 2.0V, the P-channel MOSFET
and all circuitry is turned off except the undervoltage
block, which draws only several microamperes.
Figure 2. Maximum Output Current vs Duty Cycle
DUTY CYCLE (%)
110
100
90
80
70
60
50
40
30
20
10
S
O
/
O
1772 F02
0
70 80
90 100
60
10
20 30
40 50
I
RIPPLE
= 0.4I
PK
AT 5% DUTY CYCLE
I
= 0.2I
AT 5% DUTY CYCLE
V
IN
= 4.2V
Short-Circuit Protection
When the output is shorted to ground, the frequency of the
oscillator will be reduced to about 120kHz. This lower
frequency allows the inductor current to safely discharge,
thereby preventing current runaway. The oscillator’s fre-
quency will gradually increase to its designed rate when
the feedback voltage again approaches 0.8V.
Overvoltage Protection
As a further protection, the overvoltage comparator in the
LTC1772 will turn the external MOSFET off when the
feedback voltage has risen 7.5% above the reference
voltage of 0.8V. This comparator has a typical hysteresis
of 20mV.
Slope Compensation and Inductor’s Peak Current
The inductor’s peak current is determined by:
I
V
R
(
PK
ITH
SENSE
=
)
10
when the LTC1772 is operating below 40% duty cycle.
However, once the duty cycle exceeds 40%, slope com-
pensation begins and effectively reduces the peak induc-
tor current. The amount of reduction is given by the curves
in Figure 2.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LTC1773 | Synchronous Step-Down Regulator Controller(同步步降穩(wěn)壓器) |
| LTC1775C | Quadruple 2-Input Positive-NAND Gate 14-TVSOP -40 to 85 |
| LTC1775IGN | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| LTC1775CGN | Quadruple 2-Input Positive-NAND Gate 14-TVSOP -40 to 85 |
| LTC1775CS | Quadruple 2-Input Positive-NAND Gate 14-SOIC -40 to 85 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC1772BES6 | 制造商:Linear Technology 功能描述:IC CTRLR DC/DC S-DWN SOT23-6 |
| LTC1772BES6#PBF | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Down 2.5V to 9.8V Input 6-Pin TSOT-23 制造商:Linear Technology 功能描述:DC-DC CONTROLLER BUCK 5A TS 制造商:Linear Technology 功能描述:DC-DC CONTROLLER, BUCK, 5A, TSOT-23-6; Primary Input Voltage:9.8V; No. of Outputs:1; Output Current:5A; No. of Pins:6; Operating Temperature Min:-40C; Operating Temperature Max:85C; Package / Case:6-TSOT-23; Supply Voltage Max:9.8V;RoHS Compliant: Yes 制造商:Linear Technology 功能描述:DC-DC CONTROLLER, BUCK, 5A, TSOT-23-6; Primary Input Voltage:9.8V; No. of Outputs:1; Output Current:5A; No. of Pins:6; Operating Temperature Min:-40C; Operating Temperature Max:85C; Package / Case:6-TSOT-23 ;RoHS Compliant: Yes |
| LTC1772BES6#TR | 功能描述:IC REG CTRLR BUCK PWM CM SOT23-6 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) |
| LTC1772BES6#TRM | 功能描述:IC REG CTRLR BUCK PWM CM SOT23-6 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) |
| LTC1772BES6#TRMPBF | 功能描述:IC REG CTRLR BUCK PWM CM SOT23-6 RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 特色產(chǎn)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(shù):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(chǎn)品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
發(fā)布緊急采購，3分鐘左右您將得到回復。