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参数资料
| 型号： | LT1943EFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 13/20页 |
| 文件大小： | 0K |
| 描述： | IC REG SW QUAD TFT LCD 28-TSSOP |
| 标准包装： | 2,000 |
| 应用： | 转换器，TFT，LCD |
| 输入电压： | 4.5 V ~ 22 V |
| 输出数： | 4 |
| 输出电压： | 1.25 V ~ 40 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-SOIC（0.173"，4.40mm 宽）裸露焊盘 |
| 供应商设备封装： | 28-TSSOP 裸露焊盘 |
| 包装： | 带卷 (TR) |
LT1943
OPERATIO
Output Capacitor Selection
For 5V and 3.3V outputs, a 10 μ F 6.3V ceramic capacitor
(X5R or X7R) at the output results in very low output
voltage ripple and good transient response. Other types
and values will also work; the following discussion ex-
plores tradeoffs in output ripple and transient perfor-
mance.
The output capacitor filters the inductor current to gener-
ate an output with low voltage ripple. It also stores energy
in order satisfy transient loads and stabilizes the LT1943’s
control loop. Because the LT1943 operates at a high
frequency, minimal output capacitance is necessary. In
addition, the control loop operates well with or without the
presence of output capacitor series resistance (ESR).
Ceramic capacitors, which achieve very low output ripple
and small circuit size, are therefore an option.
Because loop stability and transient response depend on
the value of C OUT , this loss may be unacceptable. Use X7R
and X5R types.
Electrolytic capacitors are also an option. The ESRs of
most aluminum electrolytic capacitors are too large to
deliver low output ripple. Tantalum and newer, lower ESR
organic electrolytic capacitors intended for power supply
use are suitable, and the manufacturers will specify the
ESR. Chose a capacitor with a low enough ESR for the
required output ripple. Because the volume of the capaci-
tor determines its ESR, both the size and the value will be
larger than a ceramic capacitor that would give similar
ripple performance. One benefit is that the larger capaci-
tance may give better transient response for large changes
in load current. Table 2 lists several capacitor vendors.
Table 2. Low ESR Surface Mount Capacitors
You can estimate output ripple with the following
equations:
V RIPPLE = ? I L /(8 ? f ? C OUT ) for ceramic capacitors, and
V RIPPLE = ? I L ? ESR for electrolytic capacitors (tantalum
and aluminum);
where ? I L is the peak-to-peak ripple current in the induc-
tor. The RMS content of this ripple is very low so the RMS
current rating of the output capacitor is usually not of
Vendor
Taiyo Yuden
AVX
Kemet
Sanyo
Panasonic
TDK
Type
Ceramic
Ceramic
Tantalum
Tantalum
Ta Organic
Al Organic
Ta or Al Organic
Al Organic
Ceramic
Series
X5R, X7R
X5R, X7R
TPS
T491, T494, T495
T520
A700
POSCAP
SP CAP
X5R, X7R
concern. It can be estimated with the formula:
I C(RMS) = ? I L / √ 12
Another constraint on the output capacitor is that it must
have greater energy storage than the inductor; if the stored
energy in the inductor transfers to the output, the resulting
voltage step should be small compared to the regulation
voltage. For a 5% overshoot, this requirement indicates:
C OUT > 10 ? L ? (I LIM /V OUT ) 2
The low ESR and small size of ceramic capacitors make
them the preferred type for LT1943 applications. Not all
ceramic capacitors are the same, however. Many of the
higher value capacitors use poor dielectrics with high
temperature and voltage coefficients. In particular, Y5V
and Z5U types lose a large fraction of their capacitance
with applied voltage and at temperature extremes.
Diode Selection
The catch diode (D1 from Figure 1) conducts current only
during switch off time. Average forward current in normal
operation can be calculated from:
I D(AVG) = I OUT (V IN – V OUT )/V IN
The only reason to consider a diode with a larger current
rating than necessary for nominal operation is for the
worst-case condition of shorted output. The diode current
will then increase to the typical peak switch current.
Peak reverse voltage is equal to the regulator input volt-
age. Use a diode with a reverse voltage rating greater than
the input voltage. Table 3 lists several Schottky diodes and
their manufacturers.
1943fa
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相关代理商/技术参数 |
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| LT1944 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Quad DCDC Converter for Triple Outputs TFT Supply Plus LED Driver |
| LT1944-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Micropower Step-Up DC/DC Converter |
| LT1944-1EMS | 功能描述:IC REG BST ADJ 0.1A/175MA 10MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
| LT1944-1EMS#PBF | 功能描述:IC REG BST ADJ 0.1A/175MA 10MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| LT1944-1EMS#TR | 功能描述:IC REG BST ADJ 0.1A/175MA 10MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
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