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Current Mode PWM Controller
The AAC242/43 are PWM controllers designed as upgrades on the workhorse UC1/2/3842 and UC1/2/3843 family of Current Mode PWM Controllers, available from various sources. The AAC242/43 are intended for Offline or DC/DC power converter applications.
Features in common with the x842/x843 design include current mode control, pulse-pulse current limiting, undervoltage lockout with hysteresis and an on-board voltage reference. In addition, as with the x842/x843 controllers, the AAC242 is differentiated from the AAC243 by its undervoltage lockout thresholds. The AAC242 has turnon/turn-off thresholds of 16V and 10V respectively, while the AAC243 thresholds are 8.4V and 7.6V respectively. The AAC243 is targeted for battery applications, based on their lower undervoltage and hysteresis levels. The lower V-ILimit options of the AAC242/43 of 0.25V, as compared to the 1.0V for the AAC142/43, allow for lower current sense measurements.
Other features designed into this family of Current Mode Controllers are intended to enhance their functionality and range of use. The maximum Start-Up current is substantially lower than the x842/x843. Output drive rise and fall times of 50ns for the AAC242/43 compare to 150ns maximum rise and fall times for the x842/x843. Other unique features of the AAC242/43 include an integrated soft-start function tied to the clock of the internal oscillator approximately 330 cycles, leading edge current blanking of 100ns and a more robust, higher current MOS output drive stage capable of driving much higher source and sink currents. The enhancements in drive capability, as well as rise and fall times, enable the AAC242/43 to operate up to 1MHz vs. the 500kHz maximum typically ascribed for the x842/843.
Features
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- Pulse-Pulse Current Limiting, with 0.25V I-Limit Threshold AAC242/43
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- On-Chip Bandgap Voltage Reference
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- AAC242 Undervoltage Lockout with Hysteresis for 16V Turn-on/10V Turn-off
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- AAC243 Undervoltage Lockout with Hysterisis for 8.4V Turn-on/7.6V Turn-off
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- Overvoltage Protection Zener
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- Enhanced Rise and Fall Performance, Higher Current Output Drive Stage for Operation to 1MHz
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- Peak Current Mode Control
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- Integrated Soft-Start Function, ~330 Clock Cycles
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- Leading Edge Current Blanking for Reduced Filtering 100ns
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- Offered in RoHS Compliant 8-Pin SOIC, 8-Pin PDIP, and 3mm x 3mm DFN Packages
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- Rated for Extended Industrial Temperature Range -40° C to +105° C
Applications
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- Offline Power Converters
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- DC/DC Converter
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- LED Lighting