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参数资料
| 型号： | LTC3803ES6-3#TRMPBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/16页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR FLYBK PWM TSOT23-6 |
| 标准包装： | 500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 330kHz |
| 占空比： | 90% |
| 电源电压： | 5.7 V ~ 8 V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | SOT-23-6 细型，TSOT-23-6 |
| 包装： | 带卷 (TR) |
| 相关产品： | 732-2263-6-ND - TRANS FLYBACK LTC3803 16.9UH 732-2263-1-ND - TRANS FLYBACK LTC3803 16.9UH 732-2263-2-ND - TRANS FLYBACK LTC3803 16.9UH |
LTC3803-3
APPLICATIONS INFORMATION
One potential design pitfall is undersizing the value of
capacitor C VCC . In this case, the normal supply current
drawn by the LTC3803-3 will discharge C VCC too rapidly;
before the third winding drive becomes effective, the V CC
turn-off threshold will be reached. The LTC3803-3 turns
off, and the V CC node begins to charge via R START back up
to the V CC turn-on threshold. Depending on the particular
situation, this may result in either several on-off cycles
before proper operation is reached or permanent relaxation
oscillation at the V CC node.
Component selection is as follows:
Resistor R START 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 C VCC to the V CC turn-
In applications where a third transformer winding is
undesirable or unavailable, the shunt regulator allows
the LTC3803-3 to be powered through a single dropping
resistor from V IN to V CC , in conjunction with a bypass
capacitor, C VCC , that closely decouples V CC to GND (see
Figure 3). This simplicity comes at the expense of reduced
ef?ciency due to the static power dissipation in the R VCC
dropping resistor.
The shunt regulator can draw up to 25mA through the
V CC pin to GND to drop enough voltage across R VCC to
regulate V CC to around 9.5V. For applications where V IN
is low enough such that the static power dissipation in
R VCC is acceptable, using the V CC shunt regulator is the
simplest way to power the LTC3803-3.
V IN
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 ef?ciency.
R VCC
C VCC
LTC3803-3
V CC
GND
38033 F03
Capacitor C VCC 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 V CC turn-off threshold.
Also, the third winding’s nominal output voltage should be
at least 0.5V below the minimum rated V CC clamp voltage
to avoid running up against the LTC3803-3’s V CC shunt
regulator, needlessly wasting power.
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 resistor
R B brings V CC to at least 7.6V nominal, well above the V CC
turn-off threshold. Resistor R START momentarily charges
the V CC node up to the V CC turn-on threshold, enabling
the LTC3803-3.
V IN
V CC SHUNT REGULATOR
R B
Q1
R START
LTC3803-3
V CC
In applications including a third transformer winding,
D1
8.2V
C VCC
GND
the internal V CC shunt regulator serves to protect the
LTC3803-3 from overvoltage transients as the third wind-
ing is powering up.
38033 F04
Figure 4. Powering the LTC3803-3 with an External Preregulator
38033fd
11
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3803ES6-5 | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Sync Flyback 5V Input 6-Pin TSOT-23 |
| LTC3803ES6-5#PBF | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Sync Flyback 5V Input 6-Pin TSOT-23 Bulk |
| LTC3803ES6-5#TRM | 功能描述:IC REG CTRLR FLYBK PWM TSOT23-6 RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3803ES6-5#TRMPBF | 功能描述:IC REG CTRLR FLYBK PWM TSOT23-6 RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3803ES6-5#TRPBF | 功能描述:IC REG CTRLR FLYBK PWM TSOT23-6 RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
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