Product overview
Description
The UC284xB family of control ICs provides the necessary features to implement off-line or DC to DC fixed frequency current mode control schemes with a minimal external parts count. Internally implemented circuits include a trimmed oscillator for precise DUTY CYCLE CONTROL under voltage lockout featuring start-up current less than 0.5mA, a precision reference trimmed for accuracy at the error amp input, logic to insure latched operation, a PWM comparator which also provides current limit control, and a totem pole output stage designed to source or sink high peak current. The output stage, suitable for driving N-Channel MOSFETs, is low in the off-state.
Differences between members of this family are the under-voltage lockout thresholds and maximum duty cycle ranges. The UC2842B and UC2844B have UVLO thresholds of 16V (on) and 10V (off), ideally suited off-line applications The corresponding thresholds for the UC2843B and UC2845B are 8.5V and 7.9V. The UC2842B and UC2843B can operate to duty cycles approaching 100%. A range of the zero to < 50 % is obtained by the UC2844B and UC2845B by the addition of an internal toggle flip flop which blanks the output off every other clock cycle.
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All features
- LOW START-UP AND OPERATING CURRENT
- UNDERVOLTAGE LOCKOUT WITH HYSTERESIS
- INTERNALLY TRIMMED REFERENCE WITH UNDERVOLTAGE LOCKOUT
- CURRENT LIMITING
- TRIMMED OSCILLATOR FOR PRECISE FREQUENCY CONTROL
- CURRENT MODE OPERATION TO 500kHz
- OSCILLATOR FREQUENCY GUARANTEED AT 250kHz
- LATCHING PWM FOR CYCLE-BY-CYCLE
- HIGH CURRENT TOTEM POLE OUTPUT
- AUTOMATIC FEED FORWARD COMPENSATION
Circuit Diagram
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STMicroelectronics - UC3845B
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Quality and Reliability
| Part Number | Marketing Status | Package | Grade | RoHS Compliance Grade | Material Declaration** |
|---|---|---|---|---|---|
| UC3845BD1 | Active | SO-8 | Industrial | Ecopack2 | |
| UC3845BD1013TR | Active | SO-8 | Industrial | Ecopack2 | |
| UC3845BN | Active | DIP-8 | Industrial | Ecopack2 |
(**) The Material Declaration forms available on st.com may be generic documents based on the most commonly used package within a package family. For this reason, they may not be 100% accurate for a specific device. Please contact our sales support for information on specific devices.
Sample & Buy
| Part Number | Marketing Status | Budgetary Price (US$)*/Qty | Order from ST | Order from distributors | Package | Packing Type | RoHS | Country of Origin | ECCN (US) | ECCN (EU) | Operating Temperature (°C) (min) | Operating Temperature (°C) (max) | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UC3845BN | | | distributors No availability of distributors reported, please contact our sales office | ||||||||||
| UC3845BD1 | | | distributors No availability of distributors reported, please contact our sales office | ||||||||||
| UC3845BD1013TR | | | distributors No availability of distributors reported, please contact our sales office |
UC3845BN Active
UC3845BD1 Active
UC3845BD1013TR Active
(*) Suggested Resale Price (USD) per defined quantity for BUDGETARY USE ONLY. For quotes, prices in local currency, please contact your local ST Sales Office or our Distributors