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| 型号： | LT1976HFE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 19/28页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 1.5A 16TSSOP |
| 标准包装： | 95 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.2 V ~ 54 V |
| 输入电压： | 3.3 V ~ 60 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 200kHz |
| 电流 - 输出： | 1.5A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 150°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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LT1976/LT1976B
APPLICATIO S I FOR ATIO
drops to 15 μ A. The PG pin will be active low during the
“on” portion of the SHDN waveform due to the C T capaci-
tor discharge when SHDN is taken low. See the Power
Good section for further information.
CATCH DIODE
The catch diode carries load current during the SW off
time. The average diode current is therefore dependent on
the switch duty cycle. At high input to output voltage ratios
the diode conducts most of the time. As the ratio ap-
proaches unity the diode conducts only a small fraction of
the time. The most stressful condition for the diode is
when the output is short circuited. Under this condition the
diode must safely handle I PEAK at maximum duty cycle.
To maximize high and low load current efficiency a fast
switching diode with low forward drop and low reverse
leakage should be used. Low reverse leakage is critical to
maximize low current efficiency since its value over tem-
perature can potentially exceed the magnitude of the
LT1976 supply current. Low forward drop is critical for
high current efficiency since the loss is proportional to
forward drop.
These requirements result in the use of a Schottky type
diode. DC switching losses are minimized due to its low
forward voltage drop and AC behavior is benign due to its
lack of a significant reverse recovery time. Schottky diodes
are generally available with reverse voltage ratings of 60V
and even 100V and are price competitive with other types.
Table 5. Catch Diode Selection Criteria
The effect of reverse leakage and forward drop on effi-
ciency for various Schottky diodes is shown in Table 4. As
can be seen these are conflicting parameters and the user
must weigh the importance of each specification in choos-
ing the best diode for the application.
The use of so-called “ultrafast” recovery diodes is gener-
ally not recommended. When operating in continuous
mode, the reverse recovery time exhibited by “ultrafast”
diodes will result in a slingshot type effect. The power
internal switch will ramp up V IN current into the diode in an
attempt to get it to recover. Then, when the diode has
finally turned off, some tens of nanoseconds later, the V SW
node voltage ramps up at an extremely high dV/dt, per-
haps 5V to even 10V/ns! With real world lead inductances
the V SW node can easily overshoot the V IN rail. This can
result in poor RFI behavior and, if the overshoot is severe
enough, damage the IC itself.
BOOST PIN
For most applications the boost components are a 0.33 μ F
capacitor and a MMSD914 diode. The anode is typically
connected to the regulated output voltage to generate a
voltage approximately V OUT above V IN to drive the output
stage (Figure 7a). However, the output stage discharges
the boost capacitor during the on time of the switch. The
output driver requires at least 2.5V of headroom through-
out this period to keep the switch fully saturated. If the
output voltage is less than 3.3V it is recommended that an
alternate boost supply is used. The boost diode can be
connected to the input (Figure 7b) but care must be taken
LEAKAGE
I Q at 125 ° C EFFICIENCY
V IN =12V V IN =12V
to prevent the boost voltage (V BOOST = V IN ? 2) from
exceeding the BOOST pin absolute maximum rating. The
DIODE
V OUT = 3.3V
25 ° C 125 ° C
V F AT 1A
25 ° C 125 ° C
V OUT = 3.3 V OUT = 3.3V
I L = 0A I L = 1A
additional voltage across the switch driver also increases
power loss and reduces efficiency. If available, an inde-
IR 10BQ100
0.0 μ A
59 μ A
0.72V
0.58V
125 μ A
74.1%
pendent supply can be used to generate the required
Diodes Inc.
B260SMA
Diodes Inc.
B360SMB
IR
MBRS360TR
IR 30BQ100
0.1 μ A 242 μ A 0.48V
0.2 μ A 440 μ A 0.45V
1 μ A 1.81mA 0.42V
1.7 μ A 2.64mA 0.40V
0.41V
0.36V
0.34V
0.32V
215 μ A
270 μ A
821 μ A
1088 μ A
82.8%
83.6%
83.7%
84.5%
BOOST voltage (Figure 7c). Tying BOOST to V IN or an
independent supply may reduce efficiency but it will re-
duce the minimum V IN required to start-up with light
loads. If the generated BOOST voltage dissipates too
much power at maximum load, the BOOST voltage the
LT1976 sees can be reduced by placing a Zener diode in
series with the BOOST diode (Figure 7a option).
1976bfg
19
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| LT1976IFE | 功能描述:IC REG BUCK ADJ 1.5A 16TSSOP 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 |
| LT1976IFE#PBF | 功能描述:IC REG BUCK ADJ 1.5A 16TSSOP 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 |
| LT1976IFE#PBF | 制造商:Linear Technology 功能描述:DC/DC Converter IC |
| LT1976IFE#TR | 功能描述:IC REG BUCK ADJ 1.5A 16TSSOP 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 |
| LT1976IFE#TRPBF | 功能描述:IC REG BUCK ADJ 1.5A 16TSSOP 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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