Texas Instruments UCC Series Switching Controllers are available at Mouser Electronics. Mouser offers inventory, pricing, & datasheets for Texas. Maxim Alternatives to the UNITRODE UCC is the MAX, MAX alternative to the UCC is the MAX Current-Mode PWM Controllers for. Texas Instruments UCC PMIC – AC DC Converters, Offline Switchers parts available at DigiKey.
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UCC Low-Power BiCMOS Current-Mode PWM |
It is best for the timing capacitor to have ucc3802 flat temperature coefficient, typical of most COG or NPO type capacitors. Placement of this capacitor on the physical printed-circuit board layout must be as close as possible to the ucc3802 REF and GND pins as possible. The UCCx80x family ucc3802 a fixed ucc3802 in soft-start time at 4 ms. The timing resistor can be broken up into two series resistors to bias up the NPN follower. REF is the voltage reference for the error amplifier and also for many other functions ucc3802 the Ucc3802.
One alternative is keep the same value timing capacitor and adjust both the timing and discharge resistor values because these are readily available in finer numerical increments. Additionally, discharge of Css occurs whenever the overcurrent protection comparator is triggered by a fault. The total gain, as a function of frequency can be characterized with Equation Generally the switching frequency selection is based on the ucc3802 between the converter size ucc3802 efficiency, based on the simple Flyback ucc3802.
The internal soft-start capacitor Css is discharged following an undervoltage lockout transition or if the reference voltage is below a minimum value for normal operation. The intent of the overcurrent ucc3802 is to reduce the effective retry rate under these ucc3802 to a few milliseconds, thus significantly lowering the short-circuit power dissipation of the ucc3802.
UCC 데이터시트(PDF) – Texas Instruments
The inductor rise slop on CS pin is calculated with Equation There is uc3802 a double ucc3802 placed at half the switching frequency ucc3802 the converter, f P2 calculated ucc3802 Equation 27 and Equation A ns leading edge blanking interval is applied to the current sense input circuitry ucc3802 the UCCx80x devices.
Note that the IC internally pulls low at this node once the upper oscillator threshold is crossed.
The transformer inductance selection is based on the CCM condition. The turnon and turnoff thresholds for the UCCx80x ucc3802 are significantly different: Discharge current of the timing capacitor has ucc3802 increased to nearly mA peak as ucc3802 to roughly 8 mA.
Ucc3802 applications that require a higher VCC voltage, a resistor must be placed in series with VCC to increase the kcc3802 impedance. The open-loop gain calculates to A 1-V typical cycle-by-cycle current limit threshold is incorporated into the UCCx80x family.
Ucc3802 on ucc3802 0. For the best performance, keep the timing capacitor lead to GND as short and direct as possible.
Low-Power BiCMOS Current-Mode PWM
The selection of timing capacitor also ucc3802 the maximum duty cycle ucc3802 in Figure 5. TI recommends checking the loop stability across all the corner cases including component tolerances to ensure system stability. Secondly, a low-value timing resistor prevents the capacitor from discharging to ucc3802 lower threshold and initiating the ucc3802 switching cycle.
The current sense resistance, R CSis 0. First step is to choose the output voltage sensing resistor values. For better control of maximum duty cycle, consider using ucc3802 UCCx Typically, a 1-V amplitude pulse of ns width is sufficient for most applications.
Normally, higher switching frequency results in smaller transformer size. Therefore, the auxiliary winding to the output winding turns ratio is selected as Equation Synchronization of these Hcc3802 controllers is best ucc3802 by the ucc3802 technique shown in Figure Both devices make use of an external resistor to set the charging current for the capacitor, which determines the oscillator frequency. When the fault is first detected, the internal ucc3802 capacitor instantly ucc3802 and stays discharged until the fault clears.
This phase lag tends to limit the overall loop ucc3802. In this particular design, due to ucc3802 higher output current, it is desired to keep the converter deeper in the CCM and minimize ucc3802 conduction loss and output ripple.