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参数资料
| 型号： | LTC1551LCMS8#TR-4.1 |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHED CAPACITOR REGULATOR, 900 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | PLASTIC, MSOP-8 |
| 文件页数： | 11/12页 |
| 文件大小： | 271K |
| 代理商： | LTC1551LCMS8#TR-4.1 |
8
LTC1550L/LTC1551L
The LTC1550L/LTC1551L consist of two major blocks
(see Block Diagram): an inverting charge pump and a
negative linear regulator. The charge pump uses two
external capacitors, C1 and CCP to generate a negative
voltage at CPOUT. It operates by charging and discharging
C1 on alternate phases of the internal 900kHz clock. C1 is
initially charged to VCC through switches S1 and S3. When
the internal clock changes phase, S1 and S3 open and S2
and S4 close, shorting the positive side of C1 to ground.
This forces the negative side of C1 below ground, and
charge is transferred to CCP through S4. As this cycle
repeats, the magnitude of the negative voltage approaches
VCC. The 900kHz internal clock frequency helps keep noise
out of the 400kHz to 600kHz IF bands commonly used by
portable radio frequency systems and reduces the size of
the external capacitors required. Most applications can
use standard 0.1
F ceramic capacitors for C1 and CCP.
Increasing C1 and CCP beyond 0.1F has little effect on the
output ripple or the output current capacity of the
LTC1550L/LTC1551L.
The negative voltage at CPOUT supplies the input to the
negative regulator block. This block consists of an
N-channel MOSFET pass device and a feedback amplifier
that monitors the output voltage and compares it to the
internal reference. The regulated output appears at the
VOUT pin. The regulation loop is optimized for fast tran-
sient response, enabling it to remove most of the switch-
ing artifacts present at the CPOUT pin. Output ripple is
typically below 1mVP-P with output loads between 0mA
and 10mA. The output voltage is set by a pair of internal
divider resistors for the fixed voltage versions. The N-
channel pass device minimizes dropout, allowing the
output to remain in regulation with supply voltages as low
as 2.7V for an output voltage of –2V. An output capacitor
of at least 4.7
F from VOUT to ground is required to keep
the regulator loop stable; for optimum stability and mini-
mum output ripple, at least 10
F is recommended.
Adjustable Hook-Up
For the adjustable LTC1550L/LTC1551L, the output volt-
age is set with a resistor divider from GND to VOUT
(Figure 2). Note that the internal reference and the internal
feedback amplifier are set up as a positive-output regula-
tor referenced to the VOUT pin, not as a negative regulator
APPLICATIONS INFORMATION
WU
U
Figure 2. External Resistor Connections
referenced to ground. The output resistor divider must be
set to provide 1.225V at the ADJ pin with respect to VOUT.
For example, a – 3V output would require a 17.4k resistor
from GND to ADJ, and a 12.1k resistor to VOUT.
CAPACITOR SELECTION
The LTC1550L/LTC1551L requires four external capaci-
tors: an input bypass capacitor, two 0.1
F charge pump
capacitors and an output filter capacitor. The overall
behavior of the LTC1550L/LTC1551L is strongly affected
by how the capacitors are used, and by how the capacitors
are laid out on the printed circuit board (PCB). In particu-
lar, the output capacitor’s value and ESR have a significant
effect on the output ripple and noise performance. In
addition, the ground connections for the VCC bypass
capacitor, the CPOUT capacitor and the VOUT bypass ca-
pacitor must employ star-ground techniques at the GND
pin of the LTC1550L/LTC1551L. Proper capacitor selec-
tion is critical for optimum performance of the LTC1550L/
LTC1551L.
Output Ripple vs Output Capacitor
Figure 4 shows the effect of using different output capaci-
tor values on the LTC1550L/LTC1551L output ripple.
These curves are taken using the LTC1551L circuit in
Figure 3, with CIN = 2.2F and ILOAD = 5mA. The upper
curve shows the performance with a standard tantalum
capacitor alone and the lower curve shows that of the
tantalum capacitor in parallel with a 0.1
F ceramic capaci-
tor. As a general rule, larger output capacitors provide
lower output ripple. To keep output voltage ripple below
1mVP–P, 10F, or greater, in parallel with a 0.1F ceramic
capacitor is required. To guarantee loop stability under all
conditions, a minimum of 4.7
F is required at the output.
PGND, AGND
LTC1550L
VOUT
ADJ
R1
R2
VOUT = –1.225V
R1 + R2
R2
()
1550L/51L F02
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相关代理商/技术参数 |
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| LTC1551LCS8 | 功能描述:IC REG SWITCHD CAP INV ADJ 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:500 系列:- 类型:切换式电容器（充电泵），反相 输出类型:固定 输出数:1 输出电压:-3V 输入电压:2.3 V ~ 5.5 V PWM 型:Burst Mode? 频率 - 开关:900kHz 电流 - 输出:100mA 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:SOT-23-6 细型，TSOT-23-6 包装:带卷 (TR) 供应商设备封装:TSOT-23-6 其它名称:LTC1983ES6-3#TRMTR |
| LTC1551LCS8#PBF | 功能描述:IC REG SWITCHD CAP INV ADJ 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:500 系列:- 类型:切换式电容器（充电泵），反相 输出类型:固定 输出数:1 输出电压:-3V 输入电压:2.3 V ~ 5.5 V PWM 型:Burst Mode? 频率 - 开关:900kHz 电流 - 输出:100mA 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:SOT-23-6 细型，TSOT-23-6 包装:带卷 (TR) 供应商设备封装:TSOT-23-6 其它名称:LTC1983ES6-3#TRMTR |
| LTC1551LCS8#TR | 功能描述:IC REG SWITCHD CAP INV ADJ 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 |
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