Key facts
- Brand
- STMicroelectronics
- Model
- UC3842A
- Category
- Other Electronics
- Industry
- Electronics
- Documents
- 2
- Languages
- EN
- Last added
- 2012-08-06
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SGS-THOMSON UC3842 Application Note
The document provides a detailed functional description of the UC3842 integrated pulse width modulator (PWM) designed for low-cost current-mode control in power supplies. It explains how the IC achieves good electrical performance and efficiency, particularly for off-line converters driving POWERMOS devices.
Key topics covered include the principles of current-mode control versus conventional schemes, the internal block diagram including the oscillator, error amplifier, and latch, and specific circuit configurations for under-voltage lockout (UVLO) and power sequencing. The note also details oscillator timing calculations, duty cycle limiting methods, synchronization techniques, and compensation strategies for various converter topologies.
STMicroelectronics UC3842A specifications
| Supply Voltage (low‑impedance source) | 30 V |
|---|---|
| Operating Temperature Range | -65 °C to 150 °C |
| Power Dissipation (Minidip package) | 1.25 W |
| Output Low Level Sink Current | 20 mA |
| Under‑Voltage Lockout Threshold (UC3842A) | 16 V (on) / 10 V (off) |
Source: STMicroelectronics UC2842A/3A/4A/5A and UC3842A/3A/4A/5A Datasheet
All STMicroelectronics UC3842A documents by type
How to use the product for one specific task, with worked examples.
Ratings, dimensions and ordering codes, for selection and design work.
Questions answered in these manuals
What is the operating voltage range for the UC3842?
The IC operates from a low impedance DC source of 10 V to 30 V.
What are the turn-on and turn-off thresholds for the under-voltage lockout?
The UVLO turn-on and turn-off thresholds are fixed internally at 16 V and 10 V respectively.
What is the maximum supply voltage for the UC2842A/3A/4A/5A devices?
The maximum supply voltage is 30 V.
From: STMicroelectronics UC2842A/3A/4A/5A and UC3842A/3A/4A/5A Datasheet
What are the under‑voltage lockout thresholds for the UC3842A variant?
The UVLO thresholds are 16 V when on and 10 V when off.
From: STMicroelectronics UC2842A/3A/4A/5A and UC3842A/3A/4A/5A Datasheet