Product Overview
Texas Instruments UC3844N Current-Mode PWM Controller, 8-Pin DIP
Condition
New. The photo shows a representative unit from our stock. Same or next business day shipping from our Idaho warehouse. Honest pricing, no nonsense. Online since 1999. We are here for our customers, with a no-hassle satisfaction guarantee.
Product Overview
The top face reads UC3844N over a Unitrode triangle-U logo and 9343, and the underside of the same body carries two lines reading SN340 over 55MMAL. It is a black 8-pin plastic DIP, which is what the N suffix denotes, and Texas Instruments is the corporate successor to Unitrode, so the brand on this card stands. The UC384x family is the current-mode PWM controller line used in off-line and DC-to-DC converters; 20 pieces are on the shelf, sold each.
Key Features
- Current-mode PWM controller in an 8-pin plastic DIP, the N package
- Maximum duty cycle internally toggled to about 50 percent, which is the hard difference from the UC3842, per TI's published UCx84x data
- Undervoltage lockout 16 V on and 10 V off, the same pair the UC3842 carries, per TI's published UCx84x data; the low 8.4 V and 7.6 V pair belongs to the 3843 and 3845, not here
- Start-up current 0.5 to 1 mA, matching this listing's "less than 1 mA", per TI
- VCC absolute maximum 30 V from a low-impedance source, output peak current +/-1 A, per TI
- 5.0 V reference trimmed to 2 percent on the 384x line, current-sense threshold about 1.0 V and clamped to 1 V, per TI
- Oscillator usable to 500 kHz, set by external RT and CT, per TI
- 384x leading digits set a 0 C to 70 C temperature grade, per TI's published grade table
- Body marking read from these photos: UC3844N, triangle-U logo, 9343
Verify against Texas Instruments' published UCx84x data before designing in.
Applications
- Off-line flyback supplies where duty is deliberately held at or below half
- DC-to-DC converter control with pulse-by-pulse current limiting
- Service of vintage switching supplies built around the UC384x line
- Bench work on current-mode control loops
Frequently Asked Questions
How many should I order?
Order what the repair or the build calls for; there are 20 on the shelf here, sold each, and a controller plus a spare is a common pair on one order. Shipping is $8 flat rate and free on orders over $28, so small parts like this ship smartest as part of a larger order.
Can I drop this into a UC3842 socket?
Not safely. The 3844 is internally toggled to about 50 percent maximum duty while the 3842 runs up to nearly 100 percent, so a 3844 in a 3842 socket halves the on-time the supply can reach. The undervoltage lockout is not the difference: both carry the same 16 V and 10 V pair.
Thirty-odd years off the line, and the 3844 is the half-duty one of the pair.
