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参数资料
| 型号： | LT1571EGN-5#TR |
| 厂商： | Linear Technology |
| 文件页数： | 8/16页 |
| 文件大小： | 0K |
| 描述： | IC CHARGER BATT CONST V/I 16SSOP |
| 标准包装： | 2,500 |
| 功能： | 充电管理 |
| 电池化学： | 铅酸，锂离子，镍镉，镍氢 |
| 电源电压： | 8 V ~ 26 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 供应商设备封装： | 16-SSOP |
| 包装： | 带卷 (TR) |
LT1571 Series
OPERATIO
0 . 29 ( V BAT ) ? 1 ? BAT ?
I RMS =
The LT1571 is a current mode PWM step-down (buck)
charger. The battery charge current is programmed by a
resistor R PROG (or a DAC output current) at the PROG pin
(see Block Diagram). Amplifier CA1 converts the charge
current through R S1 to a much lower current I PROG (500 μ A/
A) fed into the PROG pin. Amplifier CA2 compares the
output of CA1 with the programmed current and drives the
PWM loop to force them to be equal. High DC accuracy is
achieved with averaging capacitor C PROG . Note that I PROG
has both AC and DC components. I PROG goes through R1
and generates a ramp signal that is fed to the PWM control
comparator C1 through buffer B1 and level shift resistors
R2 and R3, forming the current mode inner loop. The
BOOST pin drives the NPN switch (Q SW ) into saturation
and reduces power loss. For batteries like lithium-ion that
APPLICATIO S I FOR ATIO
Input and Output Capacitors
In the charger circuits in Figures 1 and 2, the input
capacitor C IN is assumed to absorb all input switching
ripple current in the converter, so it must have adequate
ripple current rating. Worst-case RMS ripple current will
be equal to one half of the output charge current. Actual
capacitance value is not critical. Solid tantalum capacitors
such as the AVX TPS and Sprague 593D series have high
ripple current rating in a relatively small surface mount
package, but caution must be used when tantalum capaci-
tors are used for input bypass. High input surge currents
are possible when the adapter is hot-plugged to the
charger and solid tantalum capacitors have a known
failure mechanism when subjected to very high turn-on
surge currents. Selecting a high voltage rating on the
capacitor will minimize problems. Consult with the manufac-
turer before use. Alternatives include new high capacity
ceramic capacitors from Tokin or United Chemi-Con/
MARCON, et al. OS-CON can also be used.
The output capacitor C OUT is also assumed to absorb
output switching ripple current. The general formula for
capacitor ripple current is:
8
require both constant-current and constant-voltage charg-
ing, the 0.5%, 2.465V reference and the amplifier VA
reduce the charge current when battery voltage reaches
the preset level. For NiMH and NiCd, VA can be used for
overvoltage protection. When input voltage is removed,
the V CC pin drops to 0.7V below the battery voltage forcing
the charger into a low-battery drain (5 μ A typical) sleep
mode. To shut down the charger, simply pull the V C pin low
with a transistor.
Comparator E6 monitors the charge level and signals
through the FLAG pin when charging is in voltage mode
and the charge current has reduced to 20% or less. This
charge complete signal can be used to start a timer for
charging termination.
? V ?
? V CC ?
( L 1 )( f )
For example, with V CC = 16V, V BAT = 8.4V, L1 = 33 μ H and
f = 200kHz, I RMS = 0.18A.
EMI considerations usually make it desirable to minimize
ripple current in the battery leads. Beads or inductors can
be added to increase battery impedance at the 200kHz
switching frequency. Switching ripple current splits
between the battery and the output capacitor depending
on the ESR of the output capacitor and the battery imped-
ance. If the ESR of C OUT is 0.2 ? and the battery impedance
is raised to 4 ? with a bead of inductor, only 5% of the
ripple current will flow into the battery.
Soft-Start
The LT1571 is soft-started by the 0.33 μ F capacitor on V C
pin. On start-up, the V C pin voltage will rise quickly to 0.5V,
then ramp at a rate set by the internal 45 μ A pull-up current
and the external capacitor. Charge current starts ramping
up when the V C pin voltage reaches 0.9V and full current
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相关代理商/技术参数 |
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| LT1572 | 制造商:LINER 制造商全称:Linear Technology 功能描述:100kHz, 1.25A Switching Regulator with Catch Diode |
| LT1572CS | 功能描述:IC REG MULTI CONFIG 1.25A 16SOIC 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:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT1572CS#PBF | 功能描述:IC REG MULTI CONFIG 1.25A 16SOIC 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:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT1572CS#TR | 功能描述:IC REG MULTI CONFIG 1.25A 16SOIC 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:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT1572CS#TRPBF | 功能描述:IC REG MULTI CONFIG 1.25A 16SOIC 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:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
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