Features: ` Operation Down to an Input Voltage of 1.8 V
` High Efficiency Boost, SEPIC or Flyback (Buck-Boost) Topologies
` Drives External FETs for High-Current Applications
` Up to 2-MHz Oscillator
` Synchronizable Fixed Frequency Operation
` High-Efficiency Low-Power Mode
` High-Efficiency at Very Low-Power with Programmable Variable Frequency Mode
` Pulse-by-Pulse Current Limit
` 5-A Supply Current in Shutdown
` 150-A Supply Current in Sleep Mode
` Selectable NMOS or PMOS Rectification
` Built-In Power-On Reset (UCC39422 Only)
` Built-In Low-Voltage Detect (UCC39422 Only) simplified schematic block diagram and application circuitSpecificationsSupply Voltage (VIN, VOUT,VPUMP) . . . . . . . . . . . . . . . . . . . . 8 V
CP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 V
RSEN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.3 V to 12 V
SYNC/SD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.3 V to 5 V
ISENSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.3 V to 1 V
Storage Temperature, Tstg . . . . . . . . . . . . . . .65°C to 150°C
Junction Temperature, TJ . . . . . . . . . . . . . . . . .55°C to 150°C
Lead Temperature (Soldering, 10 seconds) . . . . . . . . . . . 300°C
† Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
‡ All voltages are with respect to ground. Currents are positive into and negative out of the specified terminals. Consult the Packaging Section of the Databook for thermal limitations and considerations of the package.
DescriptionThe UCC39421 family of synchronous PWM controllers is optimized to operate from dual alkaline/NiCd cells or a single
Lithium-Ion (Li-Ion) cell, and convert to adjustable output voltages from 2.5 V to 8 V. For applications where the input
voltage does not exceed the output, a standard boost configuration is used.
For other applications where the input voltage can swing above and below the output, a 1:1 coupled inductor (Flyback or SEPIC) is used in place of the single inductor. Fixed frequency operation can be programmed, or synchronized to an external clock source. In applications where (at light loads) variable frequency mode is acceptable, the IC can be programmed to automatically enter PFM (pulse frequency modulation) mode for an additional efficiency benefit.
Synchronous rectification provides excellent efficiency at high power levels, where N- or P- type MOSFETs can be used. At lower power levels (between 10% and 20% of full load) where fixed frequency operation is required,low power mode is entered. This mode optimizes efficiency by cutting back on the gate drive of the charging FET. At very low power levels, the IC enters a variable frequency mode (PFM). PFM can be disabled by the user.
Other features include pulse-by-pulse current limiting, and a low 5-A quiescent current during shutdown. The UCC39422 incorporates programmable power-on reset circuitry and an uncommitted comparator for low voltage detection. The available packages are 20-pin TSSOP or 20-pin N for the UCC39422, and 16-pin TSSOP or 16-pin N for the UCC39421.
UCC29421 Data Sheet
