Product details


Topology Boost, Flyback, Forward Control method Current, Feedforward, Voltage VCC (Min) (V) 15 VCC (Max) (V) 19 Duty cycle (Max) (%) 70 UVLO thresholds on/off (V) 15/8 Frequency (Max) (kHz) 1000 Operating temperature range (C) -40 to 85 Gate drive (Typ) (A) 0.8 Features Adjustable Switching Frequency, Multi-topology, Soft Start Rating Catalog open-in-new Find other PWM controllers & resonant controllers

Package | Pins | Size

SOIC (D) 8 19 mm² 3.91 x 4.9 TSSOP (PW) 8 19 mm² 3 x 6.4 VSSOP (DGK) 8 15 mm² 3 x 4.9 open-in-new Find other PWM controllers & resonant controllers


  • User Programmable Soft Start With Active Low Shutdown
  • User Programmable Maximum Duty Cycle
  • Accessible 5V Reference
  • Undervoltage Lockout
  • Operation to 1MHz
  • 0.4A Source/0.8A Sink FET Driver
  • Low 100µA Startup Current
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The UCC3809 family of BCDMOS economy low power integrated circuits contains all the control and drive circuitry required for off-line and isolated DC-to-DC fixed frequency current mode switching power supplies with minimal external parts count. Internally implemented circuits include undervoltage lockout featuring startup current less than 100µA, a user accessible voltage reference, logic to ensure latched operation, a PWM comparator, and a totem pole output stage to sink or source peak current. The output stage, suitable for driving N-Channel MOSFETs, is low in the off state.

Oscillator frequency and maximum duty cycle are programmed with two resistors and a capacitor. The UCC3809 family also features full cycle soft start.

The family has UVLO thresholds and hysteresis levels for off-line and DC-to-DC systems as shown in the table to the left.

The UCC3809 and the UCC2809 are offered in the 8 pin SOIC (D), PDIP (N), TSSOP (PW), and MSOP (P) packages. The small TSSOP and MSOP packages make the device ideal for applications where board space and height are at a premium.

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Technical documentation

= Top documentation for this product selected by TI
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Type Title Date
* Datasheet Economy Primary Side Controller datasheet (Rev. B) Nov. 19, 2004
User guide 10-Watt Flyback Converter Utilizing the UCC3809 (Rev. B) Sep. 14, 2001
User guide U-165 Reference Design: Isolated 50 Watt Flyback Converter Using Jun. 20, 2001
Application note Programming the UCC3809 for 90% Maximum Duty Cycle Clamp Jun. 04, 2001
Application note DN-62 Switching Power Supply Topology Voltage Mode vs. Current Mode Sep. 05, 1999
Application note DN-89 Comparing the UC3842, UCC3802, and UCC3809 Primary Side PWM Controllers Sep. 05, 1999
Application note U-165 Design Rvw: Isolated 50 W Flyback Converter Using UCC3809 and UC3965 Sep. 05, 1999
Application note U-168 Implementing a Practical Off-line Lithium-Ion Charger Using the UCC3809 Sep. 05, 1999

Design & development

For additional terms or required resources, click any title below to view the detail page where available.

Hardware development


The UCC3809EVM evaluation module is an isolated 10-W, 3.3-V converter designed for telecom input voltages, nominally -48 Vdc, but ranging from -32 Vdc to -75 Vdc. The UCC3809 economy primary-side controller is used as the pulse-width modulator (PWM), combined with a TLV431 low-voltage (...)

Design tools & simulation

SLUM087A.ZIP (49 KB) - PSpice Model
SLUM137.ZIP (23 KB) - TINA-TI Spice Model
SLUM138.TSC (846 KB) - TINA-TI Reference Design

Reference designs

36VDC - 75VDC Input, 3.3V@3A Output Isolated Flyback and Synchronous Buck
PMP4113 — This reference design uses the UCC2809 to control an isolated flyback that converts a standard 48V telecom input to an isolated 80V. An additional winding on the secondary of the flyback transformer generates an unregulated 12V rail. The TPS40193 controls a synchronous buck that generates a 3.3V/3A (...)
18-60VDC Input Isolated Flyback Reference Design with a 54V/1.1A Output
PMP7361 PMP7361 is an isolated flyback converter with a 54V/1.1A output.  The 18-60VDC input is suitable for 24VDC industrial and 48VDC telecom applications.  The 54VDC output can be used to power PoE power sourcing equipment (PSE).
document-generic Schematic
Universal AC Input 5V/2A USB Adaptor with Fixed Frequency Operation Reference Design
PMP9203 This reference design provides an isolated 5V/2A output from a universal 85-265VAC input. It uses the UCC2809 PWM controller to provide a fixed 100kHz operation. Maximum load efficiency is over 80%. The output is power limited (not current limited) so an additional load switch such as a TPS2001C may (...)
Design files
Battery Charger with 50V DC Input 20A
PMP4308 The PMP4308 is a 50V DC in 20A battery charger solution which uses Buck upside-down topology. PWM controller UCC2809 is selected in the design.
Design files
Isolated Sync Flyback (5V @ 0.2A) for Motor Control
PMP2431 — This low-cost (1W) isolated synchronous flyback regulator produces a 5V output from a low 24V input voltage and obtains a full-load efficiency of 85%. Possible applications include security systems, industrial, telecom and medical.

CAD/CAE symbols

Package Pins Download
SOIC (D) 8 View options
TSSOP (PW) 8 View options
VSSOP (DGK) 8 View options

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