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參數(shù)資料
| 型號(hào)： | LTC3803IS6-3 |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1 A SWITCHING CONTROLLER, 330 kHz SWITCHING FREQ-MAX, PDSO6 |
| 封裝： | 1 MM HEIGHT, PLASTIC, MO-193, TSOT-23, 6 PIN |
| 文件頁數(shù)： | 4/16頁 |
| 文件大?。?/td> | 165K |
| 代理商： | LTC3803IS6-3 |
12
LTC3803-3
38033fa
One potential design pitfall is undersizing the value of
capacitor CVCC. In this case, the normal supply current
drawn by the LTC3803-3 will discharge CVCC too rapidly;
before the third winding drive becomes effective, the VCC
turn-off threshold will be reached. The LTC3803-3 turns
off, and the VCC node begins to charge via RSTART back up
to the VCC turn-on threshold. Depending on the particular
situation, this may result in either several on-off cycles
before proper operation is reached or permanent relax-
ation oscillation at the VCC node.
Component selection is as follows:
Resistor RSTART should be made small enough to yield a
worst-case minimum charging current greater than the
maximum rated LTC3803-3 start-up current, to ensure
there is enough current to charge CVCC to the VCC turn-on
threshold. It should be made large enough to yield a worst-
case maximum charging current less than the minimum
rated LTC3803-3 supply current, so that in operation, most
of the LTC3803-3’s supply current is delivered through the
third winding. This results in the highest possible efficiency.
Capacitor CVCC should then be made large enough to avoid
the relaxation oscillation behavior described above. This is
complicated to determine theoretically as it depends on
the particulars of the secondary circuit and load behavior.
Empirical testing is recommended.
The third transformer winding should be designed so that
its output voltage, after accounting for the D2’s forward
voltage drop, exceeds the maximum VCC turn-off thresh-
old. Also, the third winding’s nominal output voltage
should be at least 0.5V below the minimum rated VCC
clamp voltage to avoid running up against the LTC3803-3’s
VCC shunt regulator, needlessly wasting power.
VCC SHUNT REGULATOR
In applications including a third transformer winding, the
internal VCC shunt regulator serves to protect the
LTC3803-3 from overvoltage transients as the third
winding is powering up.
In applications where a third transformer winding is unde-
sirable or unavailable, the shunt regulator allows the
LTC3803-3 to be powered through a single dropping
resistor from VIN to VCC, in conjunction with a bypass
capacitor, CVCC, that closely decouples VCC to GND (see
Figure 3). This simplicity comes at the expense of reduced
efficiency due to the static power dissipation in the RVCC
dropping resistor.
The shunt regulator can draw up to 25mA through the VCC
pin to GND to drop enough voltage across RVCC to regulate
VCC to around 9.5V. For applications where VIN is low
enough such that the static power dissipation in RVCC is
acceptable, using the VCC shunt regulator is the simplest
way to power the LTC3803-3.
APPLICATIO S I FOR ATIO
WU
UU
LTC3803-3
VCC
RVCC
CVCC
38033 F03
VIN
GND
Figure 3. Powering the LTC3803-3 Via the
Internal Shunt Regulator
EXTERNAL PREREGULATOR
The circuit in Figure 4 shows a third way to power the
LTC3803-3. An external series preregulator consisting of
series pass transistor Q1, Zener diode D1, and bias resis-
tor RB brings VCC to at least 7.6V nominal, well above the
maximum rated VCC turn-off threshold of 6.8V. Resistor
RSTART momentarily charges the VCC node up to the VCC
turn-on threshold, enabling the LTC3803-3.
LTC3803-3
VCC
RSTART
RB
D1
8.2V
Q1
CVCC
38033 F04
VIN
GND
Figure 4. Powering the LTC3803-3 with an External Preregulator
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| LTC3803IS6-3#PBF | 制造商:Linear Technology 功能描述:Bulk |
| LTC3803IS6-3#TRMPBF | 功能描述:IC REG CTRLR FLYBK PWM TSOT23-6 RoHS:是 類別: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:2,500 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) |
| LTC3803IS6-3#TRPBF | 功能描述:IC REG CTRLR FLYBK PWM TSOT23-6 RoHS:是 類別: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:2,500 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) |
| LTC3803IS6-5#PBF | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Sync Flyback 5V Input 6-Pin TSOT-23 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Sync Flyback 5V Input 6-Pin TSOT-23 Bulk |
| LTC3803IS6-5#TRMPBF | 功能描述:IC REG CTRLR FLYBK PWM TSOT23-6 RoHS:是 類別: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:2,500 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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