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參數(shù)資料
| 型號(hào)： | LTC3721EUF-1 |
| 廠商： | Linear Integrated Systems |
| 英文描述： | Push-Pull PWM Controller |
| 中文描述： | 推挽式PWM控制器 |
| 文件頁(yè)數(shù)： | 10/16頁(yè) |
| 文件大小： | 192K |
| 代理商： | LTC3721EUF-1 |
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LTC3721-1
10
sn37211 37211fs
OPERATIOU
V
CC
should be bypassed with a 0.1
μ
F to 1
μ
F multilayer
ceramic capacitor to decouple the fast transient currents
demanded by the output drivers and a bulk tantalum or
electrolytic capacitor to hold up the V
CC
supply before the
bootstrap winding, or an auxiliary regulator circuit takes
over.
C
HOLDUP
= (I
CC
+ I
DRIVE
) t
DELAY
/3.8V
(minimum UVLO hysteresis)
Regulated bias supplies as low as 7V can be utilized to
provide bias to the LTC3721-1. Refer to Figure 2 for
various bias supply configurations.
Programming Undervoltage Lockout
The LTC3721-1 provides undervoltage lockout (UVLO)
control for the input DC voltage feed to the power con-
verter in addition to the V
CC
UVLO function described in the
preceding section. Input DC feed UVLO is provided with
the UVLO pin. A comparator on UVLO compares a divided
down input DC feed voltage to the 5V precision reference.
When the 5V level is exceeded on UVLO, the SS pin is
released and output switching commences. At the same
time a 10
μ
A current is enabled which flows out of UVLO
into the voltage divider connected to UVLO. The amount of
DC feed hysteresis provided by this current is: 10
μ
A
R
TOP
, (Figure 3). The system UVLO threshold is: 5V
{(R
TOP
+ R
BOTTOM
)/R
BOTTOM
}. If the voltage applied to
UVLO is present and greater than 5V prior to the V
CC
UVLO
circuitry activation, then the internal UVLO logic will
prevent output switching until the following three condi-
tions are met: (1) V
CC
UVLO is enabled, (2) V
REF
is in
regulation and (3) UVLO pin is greater than 5V.
UVLO can also be used to enable and disable the power
converter. An open drain transistor connected to UVLO as
shown in Figure 3 provides this capability.
Off-Line Bias Supply Generation
If a regulated bias supply is not available to provide V
CC
voltage to the LTC3721-1 and supporting circuitry, one
must be generated. Since the power requirement is small,
approximately 1W, and the regulation is not critical, a
simple open-loop method is usually the easiest and lowest
cost approach. One method that works well is to add a
winding to the main power transformer, and post regulate
the resultant square wave with an L-C filter (see Figure 4a).
The advantage of this approach is that it maintains decent
regulation as the supply voltage varies, and it does not
require full safety isolation from the input winding of the
transformer. Some manufacturers include a primary wind-
ing for this purpose in their standard product offerings as
well. A different approach is to add a winding to the output
inductor and peak detect and filter the square wave signal
(see Figure 4b). The polarity of this winding is designed so
Figure 2. Bias Configurations
37211 F02
12V
±
10%
1.5k
V
CC
V
IN
V
CC
C
HOLD
1N5226
3V
1
μ
F
1
μ
F
V
BIAS
< V
UVLO
R
START
1N914
+
Figure 3. System UVLO Setup
ON OFF
R
BOTTOM
R
TOP
UVLO
37211 F03
Figure 4a. Auxiliary Winding Bias Supply
Figure 4b. Output Inductor Bias Supply
19211 F04a
+
V
CC
V
IN
C
HOLD
1
μ
F
R
START
2k
15V*
*OPTIONAL
19211 F04b
V
CC
V
OUT
V
IN
C
HOLD
R
START
+
1
μ
F
L
OUT
ISO BARRIER
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
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| LTC3721EUF-1#PBF | 功能描述:IC REG CTRLR ISO PWM CM 16-QFN RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)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(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱(chēng):LM1771SSDX |
| LTC3721EUF-1#TR | 功能描述:IC REG CTRLR ISO PWM CM 16-QFN RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)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(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱(chēng):LM1771SSDX |
| LTC3721EUF-1#TRPBF | 功能描述:IC REG CTRLR ISO PWM CM 16-QFN RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)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(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱(chēng):LM1771SSDX |
| LTC3722EGN-1 | 功能描述:IC REG CTRLR DIV ISO PWM 24SSOP RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)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(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱(chēng):LM1771SSDX |
| LTC3722EGN-1#PBF | 功能描述:IC REG CTRLR DIV ISO PWM 24SSOP RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)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(wú) 升壓:是 回掃:是 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:8-TSSOP（0.173"，4.40mm 寬） 包裝:帶卷 (TR) |
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