参数资料
| 型号： | LT1683EG#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 14/26页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR PWM CM 20-SSOP |
| 标准包装： | 66 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 250kHz |
| 占空比： | 46% |
| 电源电压： | 4 V ~ 20 V |
| 降压： | 无 |
| 升压： | 是 |
| 回扫： | 是 |
| 反相： | 是 |
| 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： | 20-SSOP（0.209"，5.30mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1328 (CN2011-ZH PDF) |
LT1683
APPLICATIONS INFORMATION
R1 = R2 ? OUT ? 1 ?
This part creates a second higher frequency rolloff of
harmonics that inversely depends on the slew time, the
time that voltage or current spends between the off state
and on state. This time is adjustable through the choice of
the slew resistors, the external resistors to ground on the
R VSL and R CSL pins and the external components used for
the external voltage feedback capacitors C AV , C BV (from
CAP A or CAP B to their respective MOSFET drains) and
the sense resistor. Lower slew rates (longer slew times,
lower frequency for harmonics rolloff) is created with
higher values of R VSL , R CSL , C AV , C BV and the current
sense resistor.
Setting the voltage and current slew rates should be done
empirically. The most practical way of determining these
components is to set C AV , C BV and the sense resistor value.
Then, start by making R VSL , R CSL each a 50k resistor pot
in series with 3.3k. Starting from the lowest resistor set-
ting (fast slew) adjust the pots until the noise level meets
your guidelines. Note that slower slewing waveforms will
dissipate more power so that efficiency will drop. You
can monitor this as you make your slew adjustment by
measuring input and output voltage and their respective
currents. Monitor the MOSFET temperature as slew rates
are slowed. These components will heat up as efficiency
decreases.
Measuring noise should be done carefully. It is easy to
introduce noise by poor measurement techniques. Consult
AN70 for recommended measurement techniques. Keeping
probe ground leads very short is essential.
Usually it will be desirable to keep the voltage and cur-
rent slew resistors approximately the same. There are
circumstances where a better optimization can be found by
adjusting each separately, but as these values are separated
further, a loss of independence of control may occur.
It is possible to use a single slew setting resistor. In this
case the R VSL and R CSL pins are tied together. A resistor
with a value of 1.8k to 34k (one-half the individual resis-
tors) can then be tied from these pins to ground.
In general only the R CSL value will be available for adjust-
ment of current slew. The current slew time does also
depend on the current sense resistor but this resistor is
normally set with consideration of the maximum current
in the MOSFETs.
Setting the voltage slew also involves selection of the
capacitors C AV , C BV . The voltage slew time is proportional
to the output voltage swing (basically input voltage), the
external voltage feedback capacitor and the R VSL value.
Thus at higher input voltages smaller capacitors will be
used with lower R VSL values. For a starting point use
Table 2.
Table 2
INPUT VOLTAGE CAPACITOR VALUE
<25V 5pF
50V 2.5pF
100V 1pF
Smaller value capacitors can be made in two ways. The
first is simply combining two capacitors in series. The
equivalent capacitance is then (C1 ? C2)/(C1 + C2).
The second method makes use of a capacitor divider. Care
should be taken that the voltage ratings of the capacitors
satisfy the full voltage swing (2x input voltage for push-
pull configurations) thus essentially the same rating as
the MOSFETs.
MOSFET DRAIN
C2 C1
CAP A OR B
C3
1683 F02
Figure 2
The equivalent slew capacitance for Figure 2 is
(C1 ? C2)/(C1 + C2 + C3).
Positive Output Voltage Setting
Sensing of a positive output voltage is usually done us-
ing a resistor divider from the output to the FB pin. The
positive input to the error amp is connected internally to
a 1.25V bandgap reference. The FB pin will regulate to
this voltage.
Referring to Figure 3, R1 is determined by:
? V ?
? 1.25 ?
1683fd
14
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1683IG | 功能描述:IC REG CTRLR PWM CM 20-SSOP 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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 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:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LT1683IG#PBF | 功能描述:IC REG CTRLR PWM CM 20-SSOP 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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 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:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LT1683IG#TR | 功能描述:IC REG CTRLR PWM CM 20-SSOP 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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 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:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LT1683IG#TRPBF | 功能描述:IC REG CTRLR PWM CM 20-SSOP 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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 V 降压:是 升压:无 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:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LT1684 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower Ring Tone Generator |
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