The UC, UC series are high performance fixed frequency current mode controllers. dimensions section on page 14 of this data sheet. ORDERING. Description. The UC/UC/UC/UC are fixed frequencycurrent- mode PWM controller. They are specially designed for Off-Line and DC to DC. DESCRIPTION. The UC/3/4/5 family of control ICs provides the necessary features to implement off-line or DC to DC fixed frequency current mode control.
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Current-Mode PWM Controller. uc UCx84x Current-Mode PWM Controllers datasheet (Rev. E) (pdf, MB) · View all technical documents. The UCx84x. An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, .. UC 0°C to 70°C. 6 Pin Configuration and Functions. D, JG, and P. products and disclaimers thereto appears at the end of this data sheet. CU NIPDAU. LevelC-UNLIM. 0 to UC D8. UCD8TRG4.
This application note provides a functional description of the UC3842 family and highlights the features of each in- dividual member, the UC3842, UC3843, UC3844 and UC3845 Throughout the text, the UC3842 part number will be referenced, however the generalized circuits and performance characteristics apply to each member of the UC3842 series unless otherwise noted. A review of cur- rent mode control and its benefits is included and meth- ods of avoiding common pitfalls are mentioned.
The final section presents designs of power supplies utilizing UC3842 control. Figure 1 shows the two-loop current-mode control system in a typical buck regulator application.
A clock signal initi- ates power pulses at a fixed frequency. The termination of each pulse occurs when an analog of the inductor current reaches a threshold established by the error signal. In this way the error signal actually controls peak inductor cur- rent.
This contrasts with conventional schemes in which the error signal directly controls pulse width without regard to inductor current. Several performance advantages result from the use of current-mode control.
First, an input voltage feed-forward characteristic is achieved; i. Therefore, line regulation is excellent and the error amplifier can be dedicated to correcting for load variations exclusively. For converters in which inductor current is continuous, controlling peak current is nearly equivalent to controlling average current. Therefore, when such converters employ current-mode control, the inductor can be treated as an Figure 1.
Two-Loop Current-Mode Control System 3-53 error-voltage-controlled-current-source for the purposes of small-signal analysis. This is illustrated by Figure 2. The two-pole control-to-output frequency response of these converters is reduced to a single-pole filter capacitor in parallel with load response.
One result is that the error amplifier compensation can be designed to yield a stable closed-loop converter response with greater gainband- width than would be possible with pulse-width control, giv- ing the supply improved small-signal dynamic response to changing loads.
A second result is that the error amplifier compensation circuit becomes simpler, as illustrated in Fig- ure 3. Capacitor Ci and resistor Ri, in Figure 3a add a low frequency zero which cancels one of the two control-to-. All products are sold subject to TIs terms and conditions of sale supplied at the time of order acknowledgment.
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