UCC24630 Synchronous Rectifier Controller With Ultra-Low-Standby Current
1 Features
- Secondary-Side SR Controller Optimized for 5-V to 24-V Flyback Systems
- Operating Frequency Up to 200 kHz
- Volt-Second Balance SR On-Time Control
- Minimize Effect of MOSFET Device and Layout Inductance
- CCM Operation Compatibility
- Compatible with PSR and SSR Control
- Auto Low-Power Detect and 110-µA Standby Mode Current
- Wide VDD Range from 3.6 V to 28 V
- Rail-to-Rail Gate Driver with 13-V Clamp
- Open and Short Pin Fault Protection
2 Applications
3 Description
The UCC24630 SR controller is a high-performance controller and driver for N-channel MOSFET power devices used for secondary-side synchronous rectification.
The combination of controller and MOSFET emulates a near-ideal diode rectifier. This solution not only directly reduces power dissipation of the rectifier but also reduces primary-side losses as well, due to compounding of efficiency gains.
Utilizing a volt-second balancing control method, the UCC24630 is ideal for flyback power supplies over a wide-output voltage range since the device is not connected directly to the MOSFET drain. The SR drive turn-off threshold is not dependent on the MOSFET RDS(on) which allows optimizing for maximum conduction time. Also secondary current ringing due to device and layout inductance does not affect the SR turn-off threshold.
The UCC24630 controller offers a programmable false-trigger filter, a frequency detector to automatically switch to standby mode during low power conditions and pin fault protections. The UCC24630 is compatible with DCM, TM and CCM operation.
The wide VDD operating range, wide programming range of the VPC voltage and blanking time, allows use in a variety of flyback converter designs.
Device Information(1)
| PART NUMBER | PACKAGE | BODY SIZE (NOM) |
|---|---|---|
| UCC24630 | SOT23 (6) | 2.92 mm x 1.30 mm |
- For all available packages, see the orderable addendum at the end of the data sheet.
Simplified Schematic
Gate-Drive Timing vs VDS Sensing SR Driver
4 Revision History
Changes from * Revision (March 2015) to A Revision
- Changed Applications section typo. Go
5 Pin Configuration and Functions
Pin Functions
| PIN | I/O(1) | DESCRIPTION | |
| NAME | NO. | ||
| DRV | 4 | O | DRiVe is an output used to drive the gate of an external synchronous rectifier N-channel MOSFET switching transistor, with source pin connected to GND. |
| GND | 5 | G | The GrouND pin is both the reference pin for the controller and the low-side return for the drive output. Special care should be taken to return all AC decoupling capacitors as close as possible to this pin and avoid any common trace length with analog signal return paths. |
| TBLK | 3 | – | Time BLanK pin is used to select the blanking time of the VPC rising edge. A programmable range from 200 ns to 1 µs is available to prevent false detection of the primary on-time due to ringing during DCM operation. |
| VDD | 6 | P | VDD is the bias supply input pin to the controller. A carefully placed bypass capacitor to GND is required on this pin. |
| VPC | 1 | I | The Voltage during Primary Conduction pin is connected to a resistor divider from the SR MOSFET drain. This pin determines a sample of the primary-side MOSFET volt seconds during the primary on-time. This voltage programs a voltage controlled current source for the internal VPC ramp charging current. |
| VSC | 2 | I | The Voltage during Secondary Conduction pin is connected to a resistor divider from the power-supply output. This pin determines a sample of the secondary-side output voltage used to determine SR MOSFET conduction time. This voltage programs a voltage controlled current source for the internal VSC ramp charging current. |
