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參數(shù)資料
| 型號： | RC5057M |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | High Performance Programmable Synchronous DC-DC Controller for Low Voltage Microprocessors |
| 中文描述： | SWITCHING CONTROLLER, 345 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | SOIC-16 |
| 文件頁數(shù)： | 14/20頁 |
| 文件大?。?/td> | 177K |
| 代理商： | RC5057M |
RC5057
PRODUCT SPECIFICATION
14
REV. 1.2.0 2/10/00
Application Information
The RC5057 Controller
The RC5057 is a programmable synchronous DC-DC con-
troller IC. When designed around the appropriate external
components, the RC5057 can be configured to deliver more
than 16A of output current, as appropriate for the Katmai
and Coppermine and other processors. The RC5057 func-
tions as a fixed frequency PWM step down regulator.
Main Control Loop
Refer to the RC5057 Block Diagram on page 1. The RC5057
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.
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
input from the IFB (current feedback) and VFB (voltage
feedback) pins and sets up two controlling signal paths. The
first, the voltage control path, amplifies the difference between
the VFB signal and the reference voltage from the DAC and
presents the output to one of the summing amplifier inputs.
The second, current control path, takes the difference between
the IFB and SW pins when the high-side MOSFET is on,
reproducing the voltage across the MOSFET and thus the
input current; it presents the resulting signal to another input
of the summing amplifier. These two signals are then summed
together. This output is then presented to a comparator look-
ing at the oscillator ramp, which provides the main PWM
control signal to the digital control block.
The digital control block takes the analog comparator input
and the main clock signal from the oscillator to provide the
appropriate pulses to the HIDRV and LODRV output pins.
These two outputs control the external power MOSFETs.
There is an additional comparator in the analog control section
whose function is to set the point at which the RC5057 current
limit comparator disables the output drive signals to the external
power MOSFETs.
High Current Output Drivers
The RC5057 contains two identical high current output drivers
that utilize high speed bipolar transistors in a push-pull config-
uration. The drivers’ power and ground are separated from
the chip’s power and ground for switching noise immunity.
The power supply pin, VCCP, is supplied from an external
12V source through a series resistor. The resulting voltage is
sufficient to provide the gate to source drive to the external
MOSFETs required in order to achieve a low R
DS,ON
.
Internal Voltage Reference
The reference included in the RC5057 is a precision band-gap
voltage reference. Its internal resistors are precisely trimmed
to provide a near zero temperature coefficient (TC). Based on
the reference is the output from an integrated 5-bit DAC. The
DAC monitors the 5 voltage identification pins, VID0-4. When
the VID4 pin is at logic HIGH, the DAC scales the reference
voltage from 2.0V to 3.5V in 100mV increments. When VID4
is pulled LOW, the DAC scales the reference from 1.30V to
2.05V in 50mV increments. All VID codes are available,
including those below 1.80V.
Power Good (PWRGD)
The RC5057 Power Good function is designed in accordance
with the Pentium II & III DC-DC converter specifications
and provides a continuous voltage monitor on the VFB pin.
The circuit compares the VFB signal to the VREF voltage
and outputs an active-low interrupt signal to the CPU should
the power supply voltage deviate more than ±12% of its
nominal setpoint. The output is guaranteed open-collector
high when the power supply voltage is within ±7% of its nomi-
nal setpoint. The Power Good flag provides no other control
function to the RC5057.
Output Enable/Soft Start (ENABLE/SS)
The RC5057 will accept an open collector/TTL signal for con-
trolling the output voltage. The low state disables the output
voltage. When disabled, the PWRGD output is in the low state.
Even if an enable is not required in the circuit, this pin should
have attached a capacitor (typically 100nF) to softstart the
switching. A larger value may occasionally be required if the
converter has a very large capacitor at its output.
Over-Voltage Protection
The RC5057 constantly monitors the output voltage for protec-
tion against over-voltage conditions. If the voltage at the VFB
pin exceeds the selected program voltage, an over-voltage
condition is assumed and the RC5057 disables the output
drive signal to the external high-side MOSFET. The DC-DC
converter returns to normal operation after the fault has been
removed. If it is desired to have an active over-voltage pro-
tection circuit, the RC5052, which includes all the features
of the RC5057, may be chosen instead of the RC5057.
Oscillator
The RC5057 oscillator section uses a fixed frequency of
operation of 300KHz. If it is desired to adjust this frequency
for reasons of efficiency or component size, the RC5052,
which includes all of the features of the RC5057, may be
chosen instead of the RC5057.
Design Considerations and Component
Selection
Additional information on design and component selection
may be found in Fairchild’s Application Note 57.
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| RC5057MT | 功能描述:開關變換器、穩(wěn)壓器與控制器 Syn DC-DC Controller Programmable 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 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| RC5057N | 功能描述:開關變換器、穩(wěn)壓器與控制器 DIP-16 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 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| RC5058 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:High Performance Programmable Synchronous DC-DC Controller for Multi-Voltage Platforms |
| RC5058M | 功能描述:開關變換器、穩(wěn)壓器與控制器 SOIC-24 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 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| RC5058MT | 功能描述:開關變換器、穩(wěn)壓器與控制器 SOIC-24 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 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
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