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参数资料
| 型号： | LTC1522CS8#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 5/8页 |
| 文件大小： | 0K |
| 描述： | IC REG SWITCHED CAP 5V 8SOIC |
| 标准包装： | 100 |
| 类型： | 切换式电容器（充电泵） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 5V |
| 输入电压： | 2.7 V ~ 5 V |
| 频率 - 开关： | 700kHz |
| 电流 - 输出： | 20mA |
| 同步整流器： | 无 |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 供应商设备封装： | 8-SOIC |
LTC1522
APPLICATIO N S I N FOR M ATIO N
A ceramic capacitor is recommended for the flying capaci-
tor with a value in the range of 0.1 μ F to 0.22 μ F. Note that
a large value flying cap (> 0.22 μ F) will increase output
LTC1522
V OUT
3
+
15 μ F
TANTALUM
1 μ F
CERAMIC
V OUT
5V
ripple unless C OUT is also increased. For very low load
applications, C FLY may be reduced to 0.01 μ F to 0.047 μ F.
This will reduce output ripple at the expense of efficiency
and maximum output current.
LTC1522
V OUT
3
+
3.9 ?
10 μ F
+
10 μ F
V OUT
5V
Output Ripple
TANTALUM
TANTALUM
1522 F01
Normal LTC1522 operation produces voltage ripple on the
V OUT pin. Output voltage ripple is required for the LTC1522
to regulate. Low frequency ripple exists due to the hyster-
esis in the sense comparator and propagation delays in the
charge pump enable/disable circuits. High frequency ripple
is also present mainly due to ESR (Equivalent Series
Resistance) in the output capacitor. Typical output ripple
under maximum load is 50mV P-P with a low ESR 10 μ F
output capacitor.
The magnitude of the ripple voltage depends on several
factors. High input voltages (V IN > 3.3V) increase the output
ripple since more charge is delivered to C OUT per clock
cycle. A large flying capacitor (> 0.22 μ F) also increases
ripple for the same reason. Large output current load and/
or a small output capacitor (< 10 μ F) results in higher ripple
due to higher output voltage dV/dt. High ESR capacitors
(ESR > 0.5 ? ) on the output pin cause high frequency
voltage spikes on V OUT with every clock cycle.
There are several ways to reduce the output voltage ripple.
A larger C OUT capacitor (22 μ F or greater) will reduce both
the low and high frequency ripple due to the lower C OUT
charging and discharging dV/dt and the lower ESR typi-
cally found with higher value (larger case size) capacitors.
A low ESR ceramic output capacitor will minimize the high
frequency ripple, but will not reduce the low frequency
ripple unless a high capacitance value is chosen. A reason-
able compromise is to use a 10 μ F to 22 μ F tantalum
capacitor in parallel with a 1 μ F to 3.3 μ F ceramic capacitor
on V OUT to reduce both the low and high frequency ripple.
An RC filter may also be used to reduce high frequency
voltage spikes (see Figure 1).
Figure 1. Output Ripple Reduction Techniques
In low load or high V IN applications, smaller values for
C FLY may be used to reduce output ripple. A smaller flying
capacitor (0.01 μ F to 0.047 μ F) delivers less charge per
clock cycle to the output capacitor resulting in lower
output ripple. However, the smaller value flying caps also
reduce the maximum I OUT capability as well as efficiency.
Inrush Currents
During normal operation, V IN will experience current tran-
sients in the 50mA to 100mA range whenever the charge
pump is enabled. During start-up, these inrush currents
may approach 250mA. For this reason, it is important to
minimize the source resistance between the input supply
and the V IN pin. Too much source resistance may result in
regulation problems or even prevent start-up.
Ultralow Quiescent Current (I Q = 2.1 μ A)
Regulated Supply
The LTC1522 contains an internal resistor divider (refer to
the Block Diagram) that draws only 1 μ A (typ) from V OUT .
During no-load conditions, the internal load causes a
droop rate of only 100mV per second on V OUT with
C OUT = 10 μ F. Applying a 2Hz to 100Hz, 95% to 98% duty
cycle signal to the SHDN pin ensures that the circuit of
Figure 2 comes out of shutdown frequently enough to
maintain regulation during no-load or low-load condi-
tions. Since the part spends nearly all of its time in
shutdown, the no-load quiescent current (see Figure 3a) is
approximately equal to (V OUT )(1 μ A)/(V IN )(Efficiency).
5
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| LTC1522IS8 | 功能描述:IC REG SWITCHED CAP 5V 8SOIC 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 |
| LTC1522IS8#PBF | 功能描述:IC REG SWITCHED CAP 5V 8SOIC 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: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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