参数资料
| 型号： | TPS54478RTER |
| 厂商： | Texas Instruments |
| 文件页数： | 24/38页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 4A 16WQFN |
| 标准包装： | 3,000 |
| 系列： | SWIFT™ |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.6 V ~ 4.5 V |
| 输入电压： | 2.95 V ~ 6 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 500kHz |
| 电流 - 输出： | 4A |
| 同步整流器： | 是 |
| 工作温度： | -40°C ~ 150°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 16-WQFN 裸露焊盘（3x3） |
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SLVSAS2 – JUNE 2011
For this example, the transient load response is specified as a 3% change in Vout for a load step from 1 A (25%
load) to 3 A (75% load). For this example, Δ Iout = 3 - 1 = 2.0A and Δ Vout= 0.03 × 1.8 = 0.054 V. Using these
numbers gives a minimum capacitance of 74.1 μ F. This value does not take the ESR of the output capacitor into
account in the output voltage change. For ceramic capacitors, the ESR is usually small enough to ignore in this
calculation.
Equation 24 calculates the minimum output capacitance needed to meet the output voltage ripple specification.
Where fsw is the switching frequency, Vripple is the maximum allowable output voltage ripple, and Iripple is the
inductor ripple current. In this case, the maximum output voltage ripple is 30 mV. Under this requirement,
vertical spacer
Co >
2 ′ D Iout
| sw ′ D Vout
vertical spacer
(23)
Co >
1
8 ′ | sw
′
1
Voripple
Iripple
Where Δ Iout is the change in output current, f sw is the regulators switching frequency and Δ Vout is the
allowable change in the output voltage.
(24)
vertical spacer
Equation 25 calculates the maximum ESR an output capacitor can have to meet the output voltage ripple
specification. Equation 25 indicates the ESR should be less than 28.6 m ? . In this case, the ESR of the ceramic
capacitor is much less than 28.6 m ? .
Additional capacitance de-ratings for aging, temperature and DC bias should be factored in which increases this
minimum value. For this example, two 47 μ F 10 V X5R ceramic capacitors with 3 m ? of ESR are used. The
estimated capacitance after derating is 2 x 45 μ F = 90 μ F.
Capacitors generally have limits to the amount of ripple current they can handle without failing or producing
excess heat. An output capacitor that can support the inductor ripple current must be specified. Some capacitor
data sheets specify the RMS (Root Mean Square) value of the maximum ripple current. Equation 26 can be used
to calculate the RMS ripple current the output capacitor needs to support. For this application, Equation 26 yields
303 mA.
Resr <
Voripple
Iripple
(25)
vertical spacer
Icorm s =
Vout ′ (Vinm ax - Vout)
12 ′ Vinm ax ′ L1 ′ | sw
(26)
INPUT CAPACITOR
The TPS54478 requires a high quality ceramic, type X5R or X7R, input decoupling capacitor of at least 10 μ F of
effective capacitance and in some applications a bulk capacitance. The effective capacitance includes any DC
bias effects. The voltage rating of the input capacitor must be greater than the maximum input voltage. The
capacitor must also have a ripple current rating greater than the maximum input current ripple of the TPS54478.
The value of a ceramic capacitor varies significantly over temperature and the amount of DC bias applied to the
capacitor. The capacitance variations due to temperature can be minimized by selecting a dielectric material that
is stable over temperature. X5R and X7R ceramic dielectrics are usually selected for power regulator capacitors
because they have a high capacitance to volume ratio and are fairly stable over temperature. The output
capacitor must also be selected with the DC bias taken into account. The capacitance value of a capacitor
decreases as the DC bias across a capacitor increases.
24
Copyright ? 2011, Texas Instruments Incorporated
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相关代理商/技术参数 |
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| TPS54478RTET | 功能描述:直流/直流开关调节器 2.95V-6Vin,6A,Sync Step-Down Converter RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| TPS54494 | 制造商:TI 制造商全称:Texas Instruments 功能描述:4A/2A Dual Channel Synchronous Step-Down Switcher with Integrated FET |
| TPS54494EVM-057 | 制造商:Texas Instruments 功能描述:Evaluation Module Access To The Features Of The TPS54494 制造商:Texas Instruments 功能描述:TPS54494EVM-057 - Boxed Product (Development Kits) 制造商:Texas Instruments 功能描述:EVAL MODULE FOR TPS54494-057 制造商:Texas Instruments 功能描述:TPS54494 Eval Mod |
| TPS54494PWP | 功能描述:直流/直流开关转换器 4A Dual Channel Sync SD Switcher RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| TPS54494PWPR | 功能描述:直流/直流开关转换器 4A Dual Channel Sync SD Switcher RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
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