參數(shù)資料
型號(hào)： FAN5091
廠商： Fairchild Semiconductor Corporation
英文描述： Synchronous Multi-Slice DC-DC Controller(同步多片DC-DC轉(zhuǎn)換控制器)
中文描述： 同步多層DC - DC控制器（同步多片的DC - DC轉(zhuǎn)換控制器）
文件頁(yè)數(shù)： 14/20頁(yè)
文件大?。?/td> 116K
代理商： FAN5091
FAN5091
14
A
Application Information
Operation
The FAN5091 Controller
The FAN5091 is a programmable synchronous multi-slice
DC-DC controller IC. When designed around the appropriate
external components, the FAN5091 can be configured to
deliver more than 50A of output current, as appropriate for
the new generation of high-current processors. The
FAN5091 functions as a fixed frequency PWM step down
regulator.
Main Control Loop
Refer to the FAN5091 Block Diagram on page 1. The
FAN5091 consists of two interleaved synchronous buck con-
verters, implemented with summing-mode control. Each
slice has its own current feedback, and there is a common
voltage feedback.
The two buck converters controlled by the FAN5091 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.
The FAN5091 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 amplifiers
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 slices, and the current
sensor separate for each. The voltage sensor amplifies 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 slice 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 amplifier, adding its
signal to the voltage amplifier’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 slices 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 slice. These outputs control the external
power MOSFETs.
Remote Voltage Sense
The FAN5091 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.
High Current Output Drivers
The FAN5091 contains four high current output drivers that
utilize MOSFETs in a push-pull configuration. 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 to generate the drive voltage, as shown in Figures 1
and 2; this provides 12V to drive the high-side gate. A +5V
system could use 12V directly on the BOOT pins, but then
the high-side gate will only be driven with 7V, increasing
losses. Note that the BOOT and VCC pins are separated from
the chip’s power and ground, BYPASS and AGND, for
switching noise immunity.
Adaptive Delay Gate Drive
The FAN5091 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-pump-
ing work, the RC5091 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 approximately 90%.
Thus at 200KHz, with a period of 5μsec, the low-side will be
on at least 5μsec * 10% = 500nsec. At high frequencies, this
time might fall so low as to be ineffective. The RC5091 guar-
antees a minimum low-side on-time of approximately
150nsec, regardless of what duty cycle this corresponds to.
Current Sensing
The FAN5091 has two independent current sensors, one for
each slice. Current sensing is accomplished by measuring
the source-to-drain voltage of the low-side MOSFET during
its on-time. Each slice has its own power ground pin, to per-
mit the slices 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 slice as a
Kelvin trace pair directly to the source and drain, respec-
tively, of the appropriate low-side MOSFET.
相關(guān)PDF資料
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
FAN5091_CAB3116B WAF 制造商:Fairchild Semiconductor Corporation 功能描述:
FAN5091MTC 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Sync Buck Converter 2Phs Interleaved RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
FAN5091MTC_Q 功能描述:DC/DC 開關(guān)控制器 Sync Buck Converter 2Phs Interleaved RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
FAN5091MTCX 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Sync Buck Converter 2Phs Interleaved RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
FAN5091MTF 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel
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