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| 型号： | LT1956IFE-5#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 19/28页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 5V 1.5A 16TSSOP |
| 标准包装： | 95 |
| 类型： | 降压（降压） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 5V |
| 输入电压： | 5.5 V ~ 60 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 500kHz |
| 电流 - 输出： | 1.5A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 16-TSSOP-EP |
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LT1956/LT1956-5
APPLICATIO S I FOR ATIO
V OUT 2 ( I OUT / 36 )
P DIODE =
Boost current loss:
P BOOST =
V IN
( V F )( V IN – V OUT )(I LOAD )
V IN
V F = Forward voltage of diode (assume 0.63V at 1A)
Quiescent current loss:
P Q = V IN ( 0 . 0015 ) + V OUT ( 0 . 003 )
P DIODE =
(0 .63 )(12 – 5 )(1)
12
= 0 . 37 W
( 5 ) ( 1 / 36 ) = 0 . 058 W
R SW = switch resistance (≈0.3) hot
t EFF = effective switch current/voltage overlap time
= (t r + t f + t Ir + t If )
t r = (V IN /1.2)ns
t f = (V IN /1.7)ns
t Ir = t If = (I OUT /0.05)ns
f = switch frequency
Example: with V IN = 12V, V OUT = 5V and I OUT = 1A:
P SW = ( 0 . 3 )( 1 ) 2 ( 5 ) + ( 57 ? 10 ? 9 ) ( 1 / 2 )( 1 )( 12 ) ( 500 ? 10 3 )
12
= 0 . 125 + 0 . 171 = 0 . 296 W
2
P BOOST =
12
P Q = 12 ( 0 . 0015 ) + 5 ( 0 . 003 ) = 0 . 033 W
Total power dissipation in the IC is given by:
P TOT = P SW + P BOOST + P Q
= 0.296W + 0.058W + 0.033W = 0.39W
Thermal resistance for the LT1956 packages is influenced
by the presence of internal or backside planes.
SSOP (GN16) Package: With a full plane under the GN16
package, thermal resistance will be about 85 ° C/W.
TSSOP (Exposed Pad) Package: With a full plane under the
TSSOP package, thermal resistance ( θ JA ) will be about
45 ° C/W.
To calculate die temperature, use the proper thermal
resistance ( θ JA ) number for the desired package an add in
worst-case ambient temperature:
T J = T A + ( θ JA ? P TOT )
When estimating ambient, remember the nearby catch
Notice that the catch diode’s forward voltage contributes
a significant loss in the overall system efficiency. A larger,
low V F diode can improve efficiency by several percent.
P INDUCTOR = (I LOAD )(L DCR )
L DCR = inductor DC resistance (assume 0.1 ? )
P INDUCTOR = (1)(0.1) = 0.1W
Typical thermal resistance of the board is 10 ° C/W. Taking
the catch diode and inductor power dissipation into ac-
count and using the example calculations for LT1956 dis-
sipation, the LT1956 die temperature will be estimated as:
T J = T A + ( θ JA ? P TOT ) + (10 ? [P DIODE + P INDUCTOR ])
With the GN16 package ( θ JA = 85 ° C/W), at an ambient
temperature of 70 ° C:
T J = 70 + (85 ? 0.39) + (10 ? 0.47) = 108 ° C
With the TSSOP package ( θ JA = 45 ° C/W) at an ambient
temperature of 70 ° C:
T J = 70 + (45 ? 0.37) + (10 ? 0.47) = 91 ° C
Die temperature can peak for certain combinations of
V IN , V OUT and load current. While higher V IN gives greater
switch AC losses, quiescent and catch diode losses, a
lower V IN may generate greater losses due to switch DC
losses. In general, the maximum and minimum V IN levels
should be checked with maximum typical load current for
calculation of the LT1956 die temperature. If a more
accurate die temperature is required, a measurement of
the SYNC pin resistance (to GND) can be used. The SYNC
pin resistance can be measured by forcing a voltage no
greater than 0.5V at the pin and monitoring the pin
current over temperature in a oven. This should be done
with minimal device power (low V IN and no switching
[V C = 0V]) in order to calibrate SYNC pin resistance with
ambient (oven) temperature.
diode and inductor will also be dissipating power.
1956f
19
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1956IGN | 功能描述:IC REG BUCK ADJ 1.5A 16SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 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:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT1956IGN#PBF | 功能描述:IC REG BUCK ADJ 1.5A 16SSOP 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 |
| LT1956IGN#PBF | 制造商:Linear Technology 功能描述:IC STEP-DOWN REGULATOR SSOP-16 |
| LT1956IGN#TR | 功能描述:IC REG BUCK ADJ 1.5A 16SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 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:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT1956IGN#TRPBF | 功能描述:IC REG BUCK ADJ 1.5A 16SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 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:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
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