參數(shù)資料
型號： L6996D
廠商： STMICROELECTRONICS
元件分類： 穩(wěn)壓器
英文描述： SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO24
封裝： MO-153AD, TSSOP-24
文件頁數(shù)： 7/26頁
文件大?。?/td> 272K
代理商： L6996D
15/26
L6996
in this case the maximum value is QMAXLS = 125nC.
The low side driver has been designed to have a low resistance pull-down transistor, around 0.5 ohms. This
prevents the voltage on LGATE pin raises during the fast rise-time of the pin PHASE, due to the Miller effect.
1.8 Digital to analog converter
The built-in digital to analog converter (DAC) allows the adjustment of the output voltage in correspondence to
the Table1 in pag 4: from 0.6V to 1V with 25mV steps, and from 1V to 1.75V with 50mV steps. The DAC can
receive the digital input from the CPU. The programmed voltage is available on VPROG pin, which is capable
of sourcing or sinking up to 250
A. The internal reference accuracy is ±1%.
1.9 Dynamically changing DAC code
L6996 detects as a transition any change in VID code which duration is larger than 200ns. Then, a timer forces
the chip in a ’transition state’ for about 100
s. In such a state, output protections are disabled and OVP pin goes
high.
Current limit threshold can be reduced during the transition state duration by using an external mos shorting part
of the RILIM resistor. The MOSFET gate is driven by OVP. Reducing current limit threshold prevents from output
voltage overshoot/undershoot once the new-programmed voltage has been reached (see waveforms reported
below), especially when the droop is not implemented. Note that the reduced threshold must be however high
enough to allow the output capacitor to charge/discharge within the transition time. During the transition state
duration, zero-cross comparator is disabled and inductor current is allowed to reverse. A negative current limit
is introduced. During OFF time, if inductor current is negative and reaches the threshold, low side MOSFET is
forced OFF, and remain OFF, allowing negative current to flow across high side body diode, for at least TON.
After then, the low side or high side turns ON again, depending on PWM comparator output. This allows switch-
ing frequency to be close to steady state frequency also when the device works in negative current limit protec-
tion.
Dynamically changing the VID code is useful for portable computers, where the CPU is supply at a higher volt-
age when the AC-DC adapter is plugged-in, to increase speed. A lower voltage is instead provided when only
the battery powers the CPU, to save energy.
The dynamic transition is usually made at light load condition, to allow the full current to be available for charg-
ing/discharging the output capacitor:
Iout ~ 300mA
Voutmax ~250mV
The current limit threshold should be set high enough to charge/discharge the output capacitor within the tran-
sition state duration (see below). If the output voltage changing is higher than 250mV the system can detect an
overvoltage or undervoltage that can shut down the device.
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
L6996DTR 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:DINAMICALLY PROGRAMMABLE SYNCHRONOUS STEP DOWN CONTROLLER FOR MOBILE CPUs
L6997 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:STEP DOWN CONTROLLER FOR LOW VOLTAGE OPERATIONS
L6997-28 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT
L6997-5 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT; Accessory Type:Tuning Element; For Use With:High Quality Variable Reactance Tuning Microwave Cavities, Filters & other Resonant Structures
L6997-9 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT
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