参数资料
| 型号： | LTC4081EDD#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 14/24页 |
| 文件大小： | 0K |
| 描述： | IC USB POWER MANAGER 10-DFN |
| 标准包装： | 2,500 |
| 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： | 3.75 V ~ 5.5 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-WFDFN 裸露焊盘 |
| 供应商设备封装： | 10-DFN（3x3） |
| 包装： | 带卷 (TR) |
LTC4081
OPERATIO
Constant-Frequency (PWM) Mode Operation
The switching regulator operates in constant-frequency
(PWM) mode when the MODE pin is pulled below V IL . In
this mode, it uses a current mode architecture including
an oscillator, an error ampli?er, and a PWM comparator
for excellent line and load regulation. The main switch
MP2 (P-channel MOSFET) turns on to charge the inductor
at the beginning of each clock cycle if the FB pin voltage
is less than the 0.8V reference voltage. The current into
the inductor (and the load) increases until it reaches the
peak current demanded by the error amp. At this point,
the main switch turns off and the synchronous switch
MN1 (N-channel MOSFET) turns on allowing the inductor
current to ?ow from ground to the load until either the
next clock cycle begins or the current reduces to the zero
current (I ZERO ) level.
Oscillator : In constant-frequency mode, the switching
regulator uses a dedicated oscillator which runs at a ?xed
frequency of 2.25MHz. This frequency is chosen to mini-
mize possible interference with the AM radio band.
Error Ampli?er : The error ampli?er is an internally com-
pensated transconductance (g m ) ampli?er with a g m
of 65 μmhos. The internal 0.8V reference voltage is
compared to the voltage at the FB pin to generate a
current signal at the output of the error ampli?er. This cur-
rent signal represents the peak inductor current required
to achieve regulation.
PWM Comparator : Lossless current sensing converts
the PMOS switch current signal to a voltage which is
summed with the internal slope compensation signal.
The PWM comparator compares this summed signal to
determine when to turn off the main switch. The switch
current sensing is blanked for ~12ns at the beginning of
each clock cycle to prevent false switch turn-off.
Burst Mode Operation
Burst Mode operation can be selected by pulling the
MODE pin above V IH . In this mode, the internal oscil-
lator is disabled, the error ampli?er is converted into a
comparator monitoring the FB voltage, and the inductor
current swings between a ?xed I PEAK (~100mA) and I ZERO
(35mA) irrespective of the load current as long as the FB
pin voltage is less than or equal to the reference voltage
of 0.8V. Once V FB is greater than 0.8V, the control logic
shuts off both switches along with most of the circuitry
and the regulator is said to enter into SLEEP mode. In
SLEEP mode, the regulator only draws about 20μA from
the BAT pin provided that the battery charger is turned
off. When the output voltage droops about 1% from its
nominal value, the regulator wakes up and the inductor
current resumes swinging between I PEAK and I ZERO . The
output capacitor recharges and causes the regulator to
re-enter the SLEEP state if the output load remains light
enough. The frequency of this intermittent burst operation
depends on the load current. That is, as the load current
drops further, the regulator turns on less frequently. Thus
Burst Mode operation increases the ef?ciency at light loads
by minimizing the switching and quiescent losses. However,
the output voltage ripple increases to about 2%.
To minimize ripple in the output voltage, the current limits
for both switches in Burst Mode operation are reduced
to about 20% of their values in the constant-frequency
mode. Also the zero current of the synchronous switch
is changed to about 35mA thereby preventing reverse
conduction through the inductor. Consequently, the regu-
lator can only deliver approximately 67mA of load current
while in Burst Mode operation. Any attempt to draw more
load current will cause the output voltage to drop out of
regulation.
Current Limit
To prevent inductor current runaway, there are absolute
current limits (I LIM ) on both the PMOS main switch and
the NMOS synchronous switch. These limits are internally
set at 520mA and 700mA respectively for PWM mode. If
the peak inductor current demanded by the error ampli?er
ever exceeds the PMOS I LIM , the error ampli?er will be
ignored and the inductor current will be limited to PMOS
I LIM . In Burst Mode operation, the PMOS current limit is
reduced to 100mA to minimize output voltage ripple.
4081f
14
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相关代理商/技术参数 |
参数描述 |
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| LTC4085 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Efficiency Battery Charger/USB Power Manager |
| LTC4085-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:USB Power Manager with Ideal Diode Controller and 4.1V Li-Ion Charger |
| LTC4085-3 | 制造商:LINER 制造商全称:Linear Technology 功能描述:USB Power Manager with Ideal Diode Controller and 3.95V Li-Ion Charger |
| LTC4085EDE | 制造商:Linear Technology 功能描述:USB Power Manager 14-Pin DFN EP |
| LTC4085EDE#PBF | 功能描述:IC USB POWER MANAGER 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 |
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