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参数资料
| 型号： | FAN5242QSCX |
| 文件页数： | 8/20页 |
| 文件大小： | 123K |
| 代理商： | FAN5242QSCX |
FAN5201
8
P
Voltage Control Loop
The internal transconductance voltage amplifier controls the
FAN5201’s output voltage. The battery voltage is fed to the
non-inverting input of the amplifier from the VFB pin. The
voltage at the amplifier’s inverting input is set by an 8-bit DAC,
which is controlled by a ChargingVoltage( ) command on the
SMBus (See the FAN5201 Logic section and SMBus Inter-
face Specification for more information). The output of the
amplifier drives an inverting “or’ring” transistor; the or’ring
provides control of the PWM to the lowest of the three ampli-
fiers, while the inversion provides the negative feedback
needed for proper control. The ChargingVoltage( ) command
of the SMBus provides a 10.000V offset, and 32mV steps, so
that the charging voltage can be anywhere from 10.000V to
10.000V + 255 * 32mV = 18.16V. Because a lithium-ion
(Li+) battery’s typical per-cell voltage is 4.2V maximum, this
charger is best suited for 3- and 4-cell batteries. It can also be
used for several different cell counts with NiMH batteries.
The voltage amplifier’s output is connected to the CompV pin,
which compensates the voltage-regulation loop. Typically, a
series-resistor/capacitor combination is used to form a pole-
zero pair. The pole introduced rolls off the gain starting at low
frequencies. The zero provides AC gain at mid-frequencies.
The output capacitor of the switcher then rolls off the mid-
frequency gain to below 1 to guarantee stability, before
encountering the zero introduced by the output capacitor’s
ESR. Further information on loop stabilization is available
in Applications Bulletin AB-18.
Current Control Loop
The internal transconductance current amplifier controls the
battery current while the charger is regulating current. Battery
current is sensed by monitoring the voltage across a sense
resistor (pins IFB and BAT) with an amplifier that removes
the common mode battery voltage. The battery current is fed
to the non-inverting input of the amplifier. The voltage at the
amplifier’s inverting input is set by an 8-bit DAC, which is
controlled by a ChargingCurrent( ) command on the SMBus
(See the FAN5201 Logic section and SMBus Interface Spec-
ification for more information). The output of the amplifier
drives an inverting “or’ring” transistor; the or’ring provides
control of the PWM to the lowest of the three amplifiers,
while the inversion provides the negative feedback needed
for proper control. The ChargingCurrent( ) command of the
SMBus provides 32mA steps with an 18m
sense resistor,
so that the charging current can be anywhere from 0.000A to
255 * 32mA = 8.16A.
The current amplifier’s output is connected to the CompI pin,
which compensates the current-regulation loop. Typically, a
series-resistor/capacitor combination is used to form a pole-
zero pair. The pole introduced rolls off the gain starting at low
frequencies. The zero provides AC gain at mid-frequencies.
The output capacitor of the switcher then rolls off the mid-
frequency gain to below 1 to guarantee stability, before
encountering the zero introduced by the output capacitor’s
ESR. Further information on loop stabilization is available
in Applications Bulletin AB-18.
Power Control Loop
The internal transconductance power amplifier controls the
system’s total power consumption (notebook plus battery
charging). Input voltage is monitored on pin DCIN, and
input current is sensed by monitoring the voltage across a
sense resistor (pins PSIN+ and PSIN-) with an amplifier that
removes the common mode input voltage. These two signals
are then multiplied together with an analog multiplier, and
the result is fed to the non-inverting input of the amplifier.
The voltage at the amplifier’s inverting input is set by a 4-bit
DAC, which is controlled by a ChargingPower( ) command
on the SMBus (See the FAN5201 Logic section and SMBus
Interface Specification for more information). The output of
the amplifier drives an inverting “or’ring” transistor; the
or’ring provides control of the PWM to the lowest of the
three amplifiers, while the inversion provides the negative
feedback needed for proper control. The ChargingPower( )
command of the SMBus provides a 25W offset, and 5W
steps, so that the total power drawn can be anywhere from
25W to 25W + 15 * 5W = 100W.
The power amplifier’s output is connected to the CompP pin,
which compensates the power-regulation loop. Typically, a
series-resistor/capacitor combination is used to form a pole-
zero pair. The pole introduced rolls off the gain starting at low
frequencies. The zero provides AC gain at mid-frequencies.
The output capacitor of the switcher then rolls off the mid-
frequency gain to below 1 to guarantee stability, before
encountering the zero introduced by the output capacitor’s
ESR. Further information on loop stabilization is available
in Applications Bulletin AB-18.
A sudden surge in power required by the notebook will result
in a momentary overload on the AC adapter. This has no ill
effects, because the power loop recovery time is much shorter
than the adapter's thermal time constant, and the minimum
adapter output voltage equals the battery voltage, which is
sufficient to run the notebook.
PWM Controller
The battery voltage or current or input power is controlled by
the pulse-width-modulated (PWM) DC-DC converter control-
ler. This controller drives two external MOSFETs, an N- and
a P-channel, which switch the voltage from the input source.
This switched voltage feeds an inductor, which filters the
switched rectangular wave. The controller sets the pulse width
of the switched voltage so that it supplies the desired voltage
or current to the battery. The heart of the PWM controller is
its multi-input comparator. This comparator compares the
lowest of three input signals with a ramp, to determine the
pulse width of the switched signal, setting the battery voltage
or current. The three signals being or’red together are the
current-sense amplifier’s output, the voltage-error amplifier’s
output, and the power-error amplifier’s output.
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| FAN5250_ADB3026B WAF | 制造商:Fairchild Semiconductor Corporation 功能描述: |
| FAN5250_AZB3026B WAF | 制造商:Fairchild Semiconductor Corporation 功能描述: |
| FAN5250QSC | 功能描述:DC/DC 开关控制器 DC/DC RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| FAN5250QSC_Q | 功能描述:DC/DC 开关控制器 DC/DC RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
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