Current-mode PWM controller (UC3844)
UC3844 current-mode PWM controller (DIP-8) · UVLO on 16 V / off 10 V · 0.5 mA start-up current · output at half the RT/CT oscillator, 50 % maximum duty · current sense trips at 1 V · COMP sets the peak current: (V_COMP − 1.4 V) / 3 · 5 V reference · 1 A totem-pole gate drive
Try it on the benchThe lab drops it on an empty bench and opens its datasheet card.
Pins
- 1 COMP
- 2 VFB
- 3 CS (current sense)
- 4 RT/CT
- 5 GND
- 6 OUT (gate)
- 7 VCC
- 8 VREF (5 V)
Lessons and builds that use it
- 65 W USB-C PD charger from scratch: mains flyback (UC3844, 800 V MOSFET, PQ2625 transformer), TL431 + PC817 feedback, PD controller (build)
- Real device: phone charger, 220 V AC wall to 5 V USB (build)
- Real device: laptop charger, 220 V AC wall to 20 V with PFC (build)