參數(shù)資料
型號(hào)： RT8800BGQV
廠商： Richtek Technology Corporation
英文描述： General Purpose 2/3-Phase PWM Controller for High-Density Power Supply
中文描述： 通用2/3-Phase PWM控制器，用于高密度電源
文件頁(yè)數(shù)： 14/26頁(yè)
文件大?。?/td> 546K
代理商： RT8800BGQV
RT8800/B
14
DS8800/B-06 March 2007
www.richtek.com
All brand name or trademark belong to their owner respectively
Application Information
RT8800/B are multiphase DC/DC controllers for extreme
low cost applications that precisely regulate CPU core
voltage and balance the current of different power channels
using time sharing current sensing method. The converter
consisting of RT8800/B and its companion MOSFET driver
RT96xx series provide high quality CPU power and all
protection functions to meet the requirement of modern
VRM.
Phase Setting and Converter Start Up
RT8800/B interface with companion MOSFET drivers (like
RT9602, RT9603, and RT9605) for correct converter
initialization. RT8800/B will sense the voltage on PWM
pins at the instant of POR rising. If the voltage is smaller
than (V
DD
1.2V) the related channel is activated. Tie the
PWM to V
DD
and the corresponding current sense pins to
GND or left float if the channel is unused. For example, for
2-Channel application, tie PWM3 to V
DD
and ISP3 to GND
(or let ISP3 open).
PGOOD Function and Soft Start
To indicate the condition of multiphase converter,
RT8800/B provide PGOOD signal through an open drain
connection. The output becomes high impedance after
internal SS ramp > 3.5V.
1) Mode 1 (SS< Vramp_valley)
Initially the COMP stays in the positive saturation. When
SS< V
RAMP_Valley
, there is no non-inverting input available
to produce duty width. So there is no PWM signal and
V
OUT
is zero.
2) Mode 2 (V
RAMP_Valley
< SS< Cross-over)
When SS>V
RAMP_Valley
, SS takes over the non-inverting
input and produce the PWM signal and the increasing
duty width according to its magnitude above the ramp
signal. The output follows the ramp signal, SS. However
while V
OUT
increases, the difference between V
OUT
and
SSE(SS
V
GS
) is reduced and COMP leaves the
saturation and declines. The takeover of SS lasts until it
meets the COMP. During this interval, since the feedback
path is broken, the converter is operated in the open loop.
3) Mode3 ( Cross-over< SS < V
GS
+ V
REF
)
When the Comp takes over the non-inverting input for PWM
Amplifier and when SSE (SS
V
GS
) < V
REF
, the output of
the converter follows the ramp input, SSE (SS
V
GS
).
Before the crossover, the output follows SS signal. And
when Comp takes over SS, the output is expected to follow
SSE (SS
V
GS
). Therefore the deviation of V
GS
is
represented as the falling of V
OUT
for a short while. The
COMP is observed to keep its decline when it passes the
cross-over, which shortens the duty width and hence the
falling of V
OUT
happens.
Since there is a feedback loop for the error amplifier, the
output
’
s response to the ramp input, SSE (SS
V
GS
) is
lower than that in Mode 2.
4) Mode 4 (SS > V
GS
+ V
REF
)
When SS > V
GS
+ V
REF
, the output of the converter follows
the desired V
REF
signal and the soft start is completed
now.
Voltage Control
The voltage control loop consists of error amplifier,
multiphase pulse width modulator, driver and power
components. As conventional voltage mode PWM
controller, the output voltage is locked at the positive input
of error amplifier and the error signal is used as the control
signal of pulse width modulator. The PWM signals of
different channels are generated by comparison of EA
output and split-phase sawtooth wave. Power stage
transforms V
IN
to output by PWM signal on-time ratio.
Output Voltage Program
The output voltage of a RT8800/B converter is programmed
to discrete levels between 1.08V and 1.85V. The voltage
identification (V
ID
) pins program an external voltage
reference (DACQ) with a 6-bit digital-to-analog converter
(DAC). The level of DACQ also sets the OVP threshold.
The output voltage should not be adjusted while the
converter is delivering power. Remove input power before
COMP
V
CORE
SSE_Internal
SS_Internal
Cross-over
V
RAMP_Valley
相關(guān)PDF資料
PDF描述
RT8800BPQV General Purpose 2/3-Phase PWM Controller for High-Density Power Supply
RT8800BPS General Purpose 2/3-Phase PWM Controller for High-Density Power Supply
RT8800GQV General Purpose 2/3-Phase PWM Controller for High-Density Power Supply
RT8800GS General Purpose 2/3-Phase PWM Controller for High-Density Power Supply
RT8800PQV General Purpose 2/3-Phase PWM Controller for High-Density Power Supply
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
RT8800BGS 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:General Purpose 2/3-Phase PWM Controller for High-Density Power Supply
RT8800BPQV 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:General Purpose 2/3-Phase PWM Controller for High-Density Power Supply
RT8800BPS 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:General Purpose 2/3-Phase PWM Controller for High-Density Power Supply
RT8800GQV 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:General Purpose 2/3-Phase PWM Controller for High-Density Power Supply
RT8800GS 制造商:RICHTEK 制造商全稱:Richtek Technology Corporation 功能描述:General Purpose 2/3-Phase PWM Controller for High-Density Power Supply
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