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参数资料
| 型号： | FAN5094MTC |
| 厂商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 中文描述： | 3 A SWITCHING CONTROLLER, 2000 kHz SWITCHING FREQ-MAX, PDSO28 |
| 封装： | TSSOP-28 |
| 文件页数： | 7/22页 |
| 文件大小： | 182K |
| 代理商： | FAN5094MTC |
PRODUCT SPECIFICATION
FAN5094
REV. 1.0.2 5/13/02
15
Application Information
Operation
The FAN5094 Controller
The FAN5094 is a programmable synchronous multi-phase
DC-DC controller IC. When designed around the appropriate
external components, the FAN5094 can be congured to
deliver more than 100A of output current, as appropriate for
the new generation of high-current processors. The
FAN5094 functions as a xed frequency PWM step down
regulator, with a high efciency mode (E*) at light load.
Main Control Loop
Refer to the FAN5094 Block Diagram on page 7. The
FAN5094 consists of two interleaved synchronous buck con-
verters, implemented with summing-mode control. Each
phase has its own current feedback, and there is a common
voltage feedback.
The two buck converters controlled by the FAN5094 are
interleaved, that is, they run 180
° out of phase with each
other. This minimizes the RMS input ripple current, mini-
mizing the number of input capacitors required. It also
doubles the effective switching frequency, improving
transient response.
The FAN5094 implements “summing mode control”, which
is different from both classical voltage-mode and current-
mode control. It provides superior performance to either by
allowing a large converter bandwidth over a wide range of
output loads and external components.
The control loop of the regulator contains two main sections:
the analog control block and the digital control block. The
analog section consists of signal conditioning ampliers
feeding into a comparator which provides the input to the
digital control block. The signal conditioning section accepts
inputs from a current sensor and a voltage sensor, with the
voltage sensor being common to both phases, and the current
sensor separate for each. The voltage sensor amplies the
difference between the VFB signal and the reference voltage
from the DAC and presents the output to each of the two
comparators. The current control path for each phase takes
the difference between its PGND and SW pins when the
low-side MOSFET is on, reproducing the voltage across the
MOSFET and thus the input current; it presents the resulting
signal to the same input of its summing amplier, adding its
signal to the voltage amplier’s with a certain gain. These
two signals are thus summed together. This sum is then pre-
sented to a comparator looking at the oscillator ramp, which
provides the main PWM control signal to the digital control
block. The oscillator ramps are 180
° out of phase with each
other, so that the two phases are on alternately.
The digital control block takes the analog comparator input
to provide the appropriate pulses to the HDRV and LDRV
output pins for each phase. These outputs control the exter-
nal power MOSFETs.
Remote Voltage Sense
The FAN5094 has true remote voltage sense capability, elim-
inating errors due to trace resistance. To utilize remote sense,
the VFB and AGND pins should be connected as a Kelvin
trace pair to the point of regulation, such as the processor
pins. The converter will maintain the voltage in regulation at
that point. Care is required in layout of these grounds; see
the layout guidelines in this datasheet.
High Current Output Drivers
The FAN5094 contains four high current output drivers that
utilize MOSFETs in a push-pull conguration. The drivers
for the high-side MOSFETs use the BOOT pin for input
power and the SW pin for return. The drivers for the low-side
MOSFETs use the VCC pin for input power and the PGND
pin for return. Typically, the BOOT pin will use a charge
pump as shown in Figures 1–2. Note that the BOOT and
VCC pins are separated from the chip’s internal power and
ground, BYPASS and AGND, for switching noise immunity.
Adaptive Delay Gate Drive
The FAN5094 embodies an advanced design that ensures
minimum MOSFET transition times while eliminating
shoot-through current. It senses the state of the MOSFETs
and adjusts the gate drive adaptively to ensure that they are
never on simultaneously. When the high-side MOSFET turns
off, the voltage on its source begins to fall. When the voltage
there reaches approximately 2.5V, the low-side MOSFETs
gate drive is applied with approximately 50nsec delay. When
the low-side MOSFET turns off, the voltage at the LDRV pin
is sensed. When it drops below approximately 2V, the high-
side MOSFET’s gate drive is applied.
Maximum Duty Cycle
In order to ensure that the current-sensing and charge-
pumping work, the FAN5094 guarantees that the low-side
MOSFET will be on a certain portion of each period. For low
frequencies, this occurs as a maximum duty cycle of approxi-
mately 90%. Thus at 500KHz, with a period of 2sec, the
low-side will be on at least 2sec 10% = 200nsec. At higher
frequencies, this time might fall so low as to be ineffective.
The FAN5094 guarantees a minimum low-side on-time of
approximately 330nsec, regardless of what duty cycle this
corresponds to.
Current Sensing
The FAN5094 has two independent current sensors, one for
each phase. Current sensing is accomplished by measuring
the source-to-drain voltage of the low-side MOSFET during
its on-time. Each phase has its own power ground pin, to per-
mit the phases to be placed in different locations without
affecting measurement accuracy. For best results, it is impor-
tant to connect the PGND and SW pins for each phase as a
Kelvin trace pair directly to the source and drain, respec-
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| FAN5094MTC_Q | 功能描述:DC/DC 开关控制器 Buck Converter Hi Cur Sys Voltage 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 |
| FAN5094MTCX | 功能描述:DC/DC 开关控制器 Buck Converter Hi Cur Sys Voltage 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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| FAN5098-BAB3116B WAF | 制造商:Fairchild Semiconductor Corporation 功能描述: |
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