AS3843 Astec Power, AS3843 Datasheet
AS3843
Available stocks
Related parts for AS3843
AS3843 Summary of contents
Page 1
... This sync input is a high impedance input and can easily be used for externally clocked systems. The new flip-flop topol- ogy allows the duty cycle on the AS3844 guaranteed between 49 and 50%. The AS3843/5 requires less than 0 start-up cur- rent over the full temperature range. 8L SOIC (8D) ...
Page 2
AS384x Functional Block Diagram 1 COMP + – ERROR AMP PWM COMPARATOR CURRENT SENSE (3 (1 (0.6 V) Pin Function Description Pin Number Function 1 COMP This ...
Page 3
AS384x Electrical Characteristics Electrical characteristics are guaranteed over full junction temperature range (0 to 105°C). Ambient temperature must be derated based on power dissipation and package thermal characteristics. The conditions are: V otherwise stated. To override UVLO Parameter ...
Page 4
Current Mode Controller Typical Performance Curves Supply Current vs Supply Voltage – Supply Voltage (V) CC Figure 2 Regulator Output Voltage vs Ambient Temperature 5.04 5.02 5.00 4.98 ...
Page 5
AS384x Typical Performance Curves Regulator Load Regulation 0 –4 –8 –12 150 C –16 –20 – – Regulator Source Current (mA) SC Figure 6 Timing Capacitor vs Oscillator Frequency 100 2.2 ...
Page 6
Current Mode Controller Typical Performance Curves Current Sense Input Threshold vs Error Amp Output Voltage 1 125 C A 0.6 0.4 0 – –0.2 –0.4 0 ...
Page 7
AS384x Application Information The AS3842/3/4/5 family of current-mode control ICs are low cost, high performance controllers which are pin compatible with the industry stan- dard UC3842 series of devices. Suitable for many switch mode power supply applications, these ICs have ...
Page 8
AS384x the following paragraphs. The basic operation of the oscillator is as follows: A simple RC network is used to program the fre- quency and the maximum duty ratio of the AS3842 output. See Figure 15. Timing capacitor (C ) ...
Page 9
Current Mode Controller 1 – REG R • T 1–D I – (0.736) (0.432) D 582 • 1–D (0.736) (0.432 REG L ...
Page 10
AS384x and repeatable duty ratio clamping virtually impossible due to other IC tolerances. The AS3844/5 provides true 50% duty ratio clamping by virtue of excluding from its flip-flop scheme, the normal output blanking associated with the discharge ...
Page 11
Current Mode Controller In most typical power supply designs, the con- verter’s output voltage is divided down and moni- tored at the error amplifier’s inverting input simple resistor divider network is used and is scaled such that the ...
Page 12
Current Mode Controller AS3842/3/4/5 COMP 1 ERROR AMP + 2 – PWM COMPARATOR – CURRENT SENSE 4 RT/ Leading Edge Filter Figure 20. Current Sense/PWM Latch ...
Page 13
AS384x latch is still fully operative, and the normal termi- nation of this cycle by the current sense com- parator will latch the output low until the over-temperature condition is rectified. Cycling the power will reset the over-temperature disable mechanism, ...
Page 14
Current Mode Controller when operated at duty ratios greater than 50%. Two different phenomena can occur as shown graphically in Figure 22. First, current-mode controllers detect and control the peak inductor current, whereas the con- verter’s output corresponds to the ...