UC3845B ON Semiconductor, UC3845B Datasheet
UC3845B
Available stocks
Related parts for UC3845B
UC3845B Summary of contents
Page 1
... The UC3844B, UC3845B series are high performance fixed frequency current mode controllers. They are specifically designed for Off–Line and dc–to–dc converter applications offering the designer a cost–effective solution with minimal external components. These integrated circuits feature an oscillator, a temperature compensated ...
Page 2
... Maximum package power dissipation limits must be observed. 2. Adjust V above the Startup threshold before setting Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible for UC3844B, UC3845B low = – for UC2844B, UC2845B = – for UC3844BV, UC3845BV ( [Note 2 3.3 nF. For typical values Symbol ...
Page 3
... V – Sink OL(UVLO – – 7.8 V CC(min) 9.0 7 for UC3844B, UC3845B high = + 85 C for UC2844B, UC2845B = +105 C for UC3844BV, UC3845BV = http://onsemi.com for min/max values A UC284XB UC384XB, XBV Typ Max Min Typ Max 2.5 2.55 2.42 2.5 2.58 – 0.1 – ...
Page 4
... I CC – – for UC3844B, UC3845B high = + 85 C for UC2844B, UC2845B = +105 C for UC3844BV, UC3845BV Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä http://onsemi.com ...
Page 5
... UC3844B, UC3845B, UC2844B, UC2845B Figure 6. Error Amp Open Loop Gain and Phase versus Frequency Figure 8. Reference Voltage Change versus Source Current Figure 10. Reference Load Regulation Figure 7. Current Sense Input Threshold versus Error Amp Output Voltage Figure 9. Reference Short Circuit Current versus Temperature Figure 11 ...
Page 6
... UC3844B, UC3845B, UC2844B, UC2845B Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä Ä ...
Page 7
... UC3844B, UC3845B, UC2844B, UC2845B Pin 8–Pin 14–Pin Function 1 1 Compensation 2 3 Voltage Feedback 3 5 Current Sense Gnd 6 10 Output ref 8 Power Ground Gnd 2,4,6,13 NC PIN FUNCTION DESCRIPTION Description This pin is the Error Amplifier output and is made available for loop compensation. This is the inverting input of the Error Amplifier normally connected to the switching power supply output through a resistor divider ...
Page 8
... Current Sense Comparator and PWM Latch , the oscillator The UC3844B, UC3845B operate as a current mode T controller, whereby output switch conduction is initiated by the oscillator and terminated when the peak inductor current reaches the threshold level established by the Error Amplifier Output/Compensation (Pin 1). Thus the error signal controls the peak inductor current on a cycle– ...
Page 9
... UC3844B, UC3845B, UC2844B, UC2845B Figure 16. Representative Block Diagram Figure 17. Timing Diagram http://onsemi.com 9 ...
Page 10
... UC3844B, UC3845B, UC2844B, UC2845B Undervoltage Lockout Two undervoltage lockout comparators have been incorporated to guarantee that the IC is fully functional before the output stage is enabled. The positive power supply terminal (V ) and the reference output (V CC each monitored by separate comparators. Each has built–in hysteresis to prevent erratic output behavior as their respective thresholds are crossed ...
Page 11
... UC3844B, UC3845B, UC2844B, UC2845B ) ) Figure 20. Adjustable Reduction of Clamp Level ) + * * ) Figure 22. Adjustable Buffered Reduction of Clamp Level with Soft–Start [ Figure 21. Soft–Start Circuit [ Figure 23. Current Sensing Power MOSFET http://onsemi.com ...
Page 12
... UC3844B, UC3845B, UC2844B, UC2845B Figure 24. Current Waveform Spike Suppression Figure 25. MOSFET Parasitic Oscillations Figure 26. Bipolar Transistor Drive http://onsemi.com 12 ...
Page 13
... UC3844B, UC3845B, UC2844B, UC2845B Figure 27. Isolated MOSFET Drive Figure 28. Latched Shutdown Figure 29. Error Amplifier Compensation http://onsemi.com ...
Page 14
... UC3844B, UC3845B, UC2844B, UC2845B Figure 30 Off–Line Flyback Regulator Test Line Regulation: 5 Vac to 130 Vac Load Regulation: 5 115 Vac 115 Vac Output Ripple: 5 115 Vac Efficiency V = 115 Vac in All outputs are at nominal load currents unless otherwise noted. http://onsemi.com Conditions Results = ...
Page 15
... UC3844B, UC3845B, UC2844B, UC2845B Figure 31. Step–Up Charge Pump Converter Figure 32. Voltage–Inverting Charge Pump Converter http://onsemi.com 15 Output Load Regulation (Open Loop Configuration) I (mA 29.9 2 28.8 9 28.3 18 27.4 36 24.4 ) Output Load Regulation I (mA –14.4 2 –13.2 9 –12.5 18 –11.7 32 –10.6 ...
Page 16
... UC3844B, UC3845B, UC2844B, UC2845B Device UC384XBD UC384XBDR2 UC384XBD1 UC384XBD1R2 UC384XBN UC2845BD UC284XBDR2 UC2845BD1 UC284XBD1R2 UC2844BN UC384XBVD UC3844BVDR2 UC384XBVD1 UC384XBVD1R2 UC384XBVN X indicates either define specific device part numbers. ORDERING INFORMATION Operating Temperature Range Package SO–14 SO–14 SO– + SO–8 PDIP–8 SO–14 SO–14 SO– ...
Page 17
... UC3844B, UC3845B, UC2844B, UC2845B MARKING DIAGRAMS N SUFFIX CASE 626 8 8 UC384xBN UC3844BVN AWL AWL YYWW YYWW SUFFIX CASE 751 8 8 384xB ALYW SUFFIX CASE 751A 14 14 UC384xBD UC384xBVD AWLYWW AWLYWW WL, L YY Work Week http://onsemi.com PDIP– UC3845BVN UC2844BN FAWL ...
Page 18
... UC3844B, UC3845B, UC2844B, UC2845B –B– F –A– NOTE 2 C –T– –X– –Y– –Z– PACKAGE DIMENSIONS PDIP–8 N SUFFIX CASE 626–05 ISSUE SO–8 D1 SUFFIX CASE 751–07 ISSUE http://onsemi.com ...
Page 19
... UC3844B, UC3845B, UC2844B, UC2845B –A– –B– G –T– PACKAGE DIMENSIONS SO–14 D SUFFIX CASE 751A–03 ISSUE http://onsemi.com ...
Page 20
... UC3844B, UC3845B, UC2844B, UC2845B SENSEFET is a trademark of Semiconductor Components Industries, LLC. ON Semiconductor and are trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. “ ...