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| 型号： | LT1956IGN-5 |
| 厂商： | Linear Technology |
| 文件页数： | 20/28页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 5V 1.5A 16SSOP |
| 标准包装： | 100 |
| 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-SSOP（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 供应商设备封装： | 16-SSOP |
| 其它名称： | LT1956IGN5 |
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LT1956/LT1956-5
APPLICATIO S I FOR ATIO
V OUT ? ( I SW / 36 ) ? V C 2
12 ? ( 1 / 36 ) ? 12
12 ? ( 1 / 36 ) ? 5
Note:SomeoftheinternalpowerdissipationintheIC,due
to BOOST pin voltage, can be transferred outside of the IC
to reduce junction temperature by increasing the voltage
drop in the path of the boost diode D2 (see Figure 9). This
reduction of junction temperature inside the IC will allow
higher ambient temperature operation for a given set of
conditions. BOOST pin circuitry dissipates power given by:
P DISS (BOOST Pin) =
V IN
Typically, V C2 (the boost voltage across the capacitor C2)
equals V OUT . This is because diodes D1 and D2 can be
considered almost equal, where:
V C2 = V OUT – V F (D2) – [–V F (D1)] = V OUT .
Hence, the equation for boost circuitry power dissipation
given in the previous Thermal Calculations section, is
stated as:
A zener, D4, placed in series with D2 (see Figure 9), drops
voltage to C2.
Example:
The BOOST pin power dissipation for a 20V input to 12V
output conversion at 1A is given by:
P BOOST = = 0 . 2 W
20
If a 7V zener is placed in series with D2, then power
dissipation becomes:
P BOOST = = 0 . 084 W
20
For an FE package with thermal resistance of 45 ° C/W,
ambient temperature savings would be:
T (ambient) savings = 0.116W ? 45 ° C/W = 5 ° C
P DISS ( BOOST )
=
V OUT ? ( I SW / 36 ) ? V OUT
V IN
For a GN package with thermal resistance of 85 ° C/W,
ambient temperature savings would be:
T (ambient) savings = 0.116W ? 85 ° C/W = 10 ° C
Here it can be seen that boost power dissipation increases
as the square of V OUT . It is possible, however, to reduce
V C2 below V OUT to save power dissipation by increasing
the voltage drop in the path of D2. Care should be taken
The 7V zener should be sized for excess of 0.116W
operation. The tolerances of the zener should be consid-
ered to ensure minimum V BOOST exceeds 3.3V + V DROOP .
that V C2 does not fall below the minimum 3.3V boost
voltage required for full saturation of the internal power
switch. For output voltages of 5V, V C2 is approximately 5V.
During switch turn on, V C2 will fall as the boost capacitor
C2 is discharged by the BOOST pin. In the previous BOOST
D2
D2
D4
Pin section, the value of C2 was designed for a 0.7V droop
BOOST
C2
L1
in V C2 (= V DROOP ). Hence, an output voltage as low as 4V
would still allow the minimum 3.3V for the boost function
using the C2 capacitor calculated.
V IN
C3
V IN
SHDN
SYNC
LT1956
SW
BIAS
FB
R1
+
V OUT
C1
If a target output voltage of 12V is required, however, an
GND
V C
D1
R2
excess of 8V is placed across the boost capacitor which is
not required for the boost function but still dissipates
additional power.
What is required is a voltage drop in the path of D2 to
R C
C C
C F
achieve minimal power dissipation while still maintaining
minimum boost voltage across C2.
Figure 9. BOOST Pin, Diode Selection
1956 F09
1956f
20
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| LT1956IGN-5#PBF | 功能描述:IC REG BUCK 5V 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 |
| LT1956IGN-5#TR | 功能描述:IC REG BUCK 5V 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-5#TRPBF | 功能描述:IC REG BUCK 5V 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 |
| LT1956IGNPBF | 制造商:Linear Technology 功能描述:DC-DC Converter Step-Down 5.5-60V SSOP16 |
| LT1959 | 制造商:LINER 制造商全称:Linear Technology 功能描述:4.5A, 500kHz Step-Down Switching Regulator |
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