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參數(shù)資料
| 型號： | SI9166 |
| 廠商： | Vishay Intertechnology,Inc. |
| 英文描述： | High Frequency Programmable Topology Controller |
| 中文描述： | 拓撲高頻可編程控制器 |
| 文件頁數(shù)： | 7/8頁 |
| 文件大?。?/td> | 217K |
| 代理商： | SI9166 |
Si9166
New Product
Vishay Siliconix
FaxBack 408-970-5600, request 70847
www.siliconix.com
S-60752—Rev. B, 05-Apr-99
7
PWM Mode
With PWM/PSM mode pin in logic high condition, the Si9166
operates in constant frequency (PWM) mode. As the load
and line varies, switching frequency remain constant. The
switching frequency is programmed by the R
OSC
value. In the
PWM mode, the synchronous drive is always enabled, even
when the output current reaches 0 A. Therefore, the
converter always operates in continuous conduction mode
(CCM) if a synchronous switch is used. In CCM, transfer
function of the converter remains almost constant, providing
fast transient response. If the converter operates in
discontinuous conduction mode (DCM), overall loop gain
decreases and transient response time can be ten times
longer than if the converter remain in continuous current
mode. This transient response time advantage can
significantly decrease the hold-up capacitors needed on the
output of dc/dc converter to meet the transient voltage
regulation. The PWM/PSM pin is available to dynamically
program the controller. If the synchronous rectifier switch is
not used, the converter will operate in DCM at light load.
The maximum duty cycle of the Si9166 can reach 100% in
buck mode. The duty cycle will continue to increase as the
input voltage decreases until it reaches 100%. This allows the
system designers to extract the maximum stored energy from
the battery. Once the controller delivers 100% duty cycle, the
converter operates like a saturated linear regulator. At 100%
duty cycle, synchronous rectification is completely turned off.
Up to 80% maximum duty cycle at 2-MHz switching
frequency, the controller maintains perfect output voltage
regulation. If the input voltage drops below the level where
the converter requires greater than 80% duty cycle, the
controller will deliver 100% duty cycle. This instantaneous
jump in duty cycle is due to fixed BBM time, MOSFET delay/
rise/fall time, and the internal propagational delays. In order to
maintain regulation, controller might fluctuate its duty cycle
back and forth from 100% to something lower than 80% while
the converter is operating in this input voltage range. If the
input voltage drops further, controller will remain on 100%. If
the input voltage increases to a point where it’s requiring less
than 80% duty cycle, synchronous rectification is once again
activated.
The maximum duty cycle under boost mode is internally
limited to 70% to prevent inductor saturation. If the converter
is turned on for 100% duty cycle, inductor never gets a chance
to discharge its energy and eventually saturate. In boost
mode, synchronous rectifier is always turned on for minimum
or greater duration as long as the switch has been turned on.
The controller will deliver 0% duty cycle, if the input voltage is
greater than the programmed output voltage. Because of
signal propagation time and MOSFET delay/rise/fall time,
controller will not transition smoothly from minimum
controllable duty cycle to 0% duty cycle. For example,
controller may decrease its duty cycle from 5% to 0% abruptly,
instead of gradual decrease you see from 70% to 5%.
Pulse Skipping Mode
The gate charge losses produced from the Miller capacitance
of MOSFETs are the dominant power dissipation parameter
during light load (i.e. < 10 mA). Therefore, less gate switching
will improve overall converter efficiency. This is exactly why
the Si9166 is designed with pulse skipping mode. If the
PWM/PSM pin is connected to logic low level, converter
operates in pulse skipping modulation (PSM) mode. During
the pulse skipping mode, quiescent current of the controller is
decreased to approximately 200 μA, instead of 500 μA during
the PWM mode. This is accomplished by turning off most of
internal control circuitry and utilizing a simple constant on-
time control with feedback comparator. The controller is
designed to have a constant on-time and a minimum off-time
acting as the feedback comparator blanking time. If the output
voltage drops below the desired level, the main switch is first
turned on and then off. If the applied on-time is insufficient to
provide the desired voltage, the controller will force another on
and off sequence, until the desired voltage is accomplished. If
the applied on-time forces the output to exceed the desired
level, as typically found in the light load condition, the
converter stays off. The excess energy is delivered to the
output slowly, forcing the converter to skip pulses as needed
to maintain regulation. The on-time and off-time are set
internally based on inductor used (1.5-μH typical), MODE pin
selection and maximum load current. Therefore, with this
control method, duty cycle ranging from 0 to near 100% is
possible depending on whether buck or boost is chosen. In
pulse skipping mode, synchronous rectifier drive is also
disabled to further decrease the gate charge loss and
increase overall converter efficiency.
Reference
The reference voltage for the Si9166 is set at 1.3 V. The
reference voltage is internally connected to the non-inverting
inputs of the error amplifier. The reference pin requires 0.1-μF
decoupling capacitor.
Error Amplifier
The error amplifier gain-bandwidth product and slew rate are
critical parameters which determines the transient response
of converter. The transient response is function of both small
and large signal responses. The small signal response is
determined by the feedback compensation network while the
large signal is determined by the error amplifier dv/dt and the
inductor di/dt slew rate. Besides the inductance value, error
amplifier determines the converter response time. In order to
minimize the response time, the Si9166 is designed with
2-MHz error amplifier gain-bandwidth product to generate the
widest converter bandwidth and 3.5 V/μsec slew rate for
ultra-fast large signal response.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SI9166_04 | 制造商:VISHAY 制造商全稱:Vishay Siliconix 功能描述:High Frequency Programmable Topology Controller |
| SI9166BQ-T1 | 功能描述:電壓模式 PWM 控制器 2MHz Prog Controller RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| SI9166BQ-T1-E3 | 功能描述:電壓模式 PWM 控制器 Programable Topology Controller RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| SI9166DB | 功能描述:電源管理IC開發(fā)工具 SI9166 Demo Board RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| SI9166DB-K | 制造商:Vishay Intertechnologies 功能描述:DEMO BOARD, SI9166, BUCK, BOOST, PWM / PSM, Silicon Manufacturer:Vishay, Silicon |
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