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参数资料
| 型号： | LTC4088EDE |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 3 A BATTERY CHARGE CONTROLLER, 2.7 kHz SWITCHING FREQ-MAX, PDSO14 |
| 封装： | 4 X 3 MM, 0.75 MM HEIGHT, PLASTIC, DFN-14 |
| 文件页数： | 8/24页 |
| 文件大小： | 272K |
| 代理商： | LTC4088EDE |
LTC4088
16
4088f
APPLICATIO S I FOR ATIO
WU
U
CLPROG Resistor and Capacitor
As described in the Step-Down Input Regulator section,
the resistor on the CLPROG pin determines the average
input current limit in each of the six current limit modes.
The input current will be comprised of two components,
the current that is used to drive VOUT and the quiescent
current of the switching regulator. To ensure that the USB
specication is strictly met, both components of input cur-
rent should be considered. The Electrical Characteristics
table gives the typical values for quiescent currents in all
settings as well as current limit programming accuracy.
To get as close to the 500mA or 100mA specications as
possible, a precision resistor should be used.
An averaging capacitor is required in parallel with the
resistor so that the switching regulator can determine
the average input current. This capacitor also provides
the dominant pole for the feedback loop when current
limit is reached. To ensure stability, the capacitor on
CLPROG should be 0.47F or larger. Alternatively, faster
transient response may be achieved with 0.1F in series
with 8.2
Ω.
Choosing the Inductor
Because the average input current circuit does not measure
reverse current (i.e., current from VOUT to VBUS), cur-
rent reversal in the inductor at light loads will contribute
an error to the VBUS current measurement. The error is
conservative in that if the current reverses, the voltage
at CLPROG will be higher than what would represent the
actual average input current drawn. The current available
for charging and the system load is thus reduced. The
USB specication will not be violated.
This reduction in available VBUS current will happen when
the peak-peak inductor ripple is greater than twice the
average current limit setting. For example, if the average
current limit is set to 100mA, the peak-peak ripple should
not exceed 200mA. If the input current is less than 100mA,
the measurement accuracy may be reduced, but it does
not affect the average current loop since it will not be in
regulation.
The LTC4088 includes a current-reversal comparator which
monitors inductor current and disables the synchronous
rectier as current approaches zero. This comparator will
minimize the effect of current reversal on the average input
current measurement. For some low inductance values,
however, the inductor current may reverse slightly. This
value depends on the speed of the comparator in relation
to the slope of the current waveform, given by VL/L, where
VListhevoltageacrosstheinductor(approximately–VOUT)
and L is the inductance value.
An inductance value of 3.3H is a good starting value. The
ripple will be small enough for the regulator to remain in
continuous conduction at 100mA average VBUS current. At
lighter loads the current-reversal comparator will disable
the synchronous rectier at a current slightly above 0mA. As
the inductance is reduced from this value, the part will enter
discontinuous conduction mode at progressively higher
loads. Ripple at VOUT will increase, directly proportionally
to the magnitude of inductor ripple. Transient response,
however, will be improved. The current mode controller
controls inductor current to exactly the amount required
by the load to keep VOUT in regulation. A transient load
step requires the inductor current to change to a new level.
Since inductor current cannot change instantaneously, the
capacitance on VOUT delivers or absorbs the difference in
current until the inductor current can change to meet the
new load demand. A smaller inductor changes its current
more quickly for a given voltage drive than a larger inductor,
resulting in faster transient response. A larger inductor will
reduce output ripple and current ripple, but at the expense
of reduced transient performance (or more CVOUTrequired)
and a physically larger inductor package size.
The input regulator has an instantaneous peak current
clamp to prevent the inductor from saturating during tran-
sient load or start-up conditions. The clamp is designed
so that it does not interfere with normal operation at
high loads with reasonable inductor ripple. It will prevent
inductor current runaway in case of a shorted output.
The DC winding resistance and AC core losses of the
inductor will affect efciency, and therefore available
output power. These effects are difcult to characterize
and vary by application. Some inductors which may be
suitable for this application are listed in Table 3.
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| LTC4088EDE#PBF | 功能描述:IC CHRGR BATT HE 14-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电池管理 系列:- 其它有关文件:STC3100 View All Specifications 特色产品:STC3100 - Battery Monitor IC 标准包装:4,000 系列:- 功能:燃料，电量检测计/监控器 电池化学:锂离子（Li-Ion） 电源电压:2.7 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-TSSOP，8-MSOP（0.118"，3.00mm 宽） 供应商设备封装:8-MiniSO 包装:带卷 (TR) 其它名称:497-10526-2 |
| LTC4088EDE#TRPBF | 功能描述:IC BATT CHARGER/USB 14-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电池管理 系列:- 标准包装:61 系列:- 功能:电源管理 电池化学:锂离子（Li-Ion）、锂聚合物（Li-Pol） 电源电压:4.35 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:22-WFDFN 裸露焊盘 供应商设备封装:22-DFN（6x3）裸露焊盘 包装:管件 |
| LTC4088EDE-1#PBF | 功能描述:IC BATT CHARGER/USB 14-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电池管理 系列:- 标准包装:61 系列:- 功能:电源管理 电池化学:锂离子（Li-Ion）、锂聚合物（Li-Pol） 电源电压:4.35 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:22-WFDFN 裸露焊盘 供应商设备封装:22-DFN（6x3）裸露焊盘 包装:管件 |
| LTC4088EDE-1#TRPBF | 功能描述:IC BATT CHARGER/USB 14-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电池管理 系列:- 标准包装:61 系列:- 功能:电源管理 电池化学:锂离子（Li-Ion）、锂聚合物（Li-Pol） 电源电压:4.35 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:22-WFDFN 裸露焊盘 供应商设备封装:22-DFN（6x3）裸露焊盘 包装:管件 |
| LTC4088EDE-1-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Effi ciency Battery Charger/USB Power Manager with Regulated Output Voltage |
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