UC2825A High Speed PWM Controller | TI.com

UC2825A
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High Speed PWM Controller

 

Description

The UC3823A and UC3823B and the UC3825A and UC3825B family of PWM controllers are improved versions of the standard UC3823 and UC3825 family. Performance enhancements have been made to several of the circuit blocks. Error amplifier gain bandwidth product is 12 MHz, while input offset voltage is 2 mV. Current limit threshold is assured to a tolerance of 5%. Oscillator discharge current is specified at 10 mA for accurate dead time control. Frequency accuracy is improved to 6%. Startup supply current, typically 100 µA, is ideal for off-line applications. The output drivers are redesigned to actively sink current during UVLO at no expense to the startup current specification. In addition each output is capable of 2-A peak currents during transitions.

Functional improvements have also been implemented in this family. The UC3825 shutdown comparator is now a high-speed overcurrent comparator with a threshold of 1.2 V. The overcurrent comparator sets a latch that ensures full discharge of the soft-start capacitor before allowing a restart. While the fault latch is set, the outputs are in the low state. In the event of continuous faults, the soft-start capacitor is fully charged before discharge to insure that the fault frequency does not exceed the designed soft start period. The UC3825 CLOCK pin has become CLK/LEB. This pin combines the functions of clock output and leading edge blanking adjustment and has been buffered for easier interfacing.

The UC3825A and UC3825B have dual alternating outputs and the same pin configuration of the UC3825. The UC3823A and UC3823B outputs operate in phase with duty cycles from zero to less than 100%. The pin configuration of the UC3823A and UC3823B is the same as the UC3823 except pin 11 is now an output pin instead of the reference pin to the current limit comparator. "A" version parts have UVLO thresholds identical to the original UC3823 and UC3825. The "B" versions have UVLO thresholds of 16 V and 10 V, intended for ease of use in off-line applications.

Consult the application note, The UC3823A,B and UC3825A,B Enhanced Generation of PWM Controllers, (SLUA125) for detailed technical and applications information.

Features

  • Improved Versions of the UC3823/UC3825 PWMs
  • Compatible with Voltage-Mode or Current-Mode Control Methods
  • Practical Operation at Switching Frequencies to 1 MHz
  • 50-ns Propagation Delay to Output
  • High-Current Dual Totem Pole Outputs (2-A Peak)
  • Trimmed Oscillator Discharge Current
  • Low 100-µA Startup Current
  • Pulse-by-Pulse Current Limiting Comparator
  • Latched Overcurrent Comparator With Full Cycle Restart

Parametrics

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Part number Order Topology Control method VCC (Min) (V) VCC (Max) (V) Frequency (Max) (kHz) UVLO thresholds on/off (V) Duty cycle (Max) (%) Gate drive (Typ) (A) Features Rating Operating temperature range (C) Package Group Package size: mm2:W x L (PKG)
UC2825A Order now Boost
Flyback
Forward
Full-Bridge
Half-Bridge
Push-Pull    
Current
Voltage    
9.2     22     1000     9.2/8.4     50     2     Adjustable Switching Frequency
Current Limiting
Dead Time Control
Error Amplifier
Leading Edge Blanking
Multi-topology
Programmable Max Duty Cycle
Soft Start
Synchronization Pin    
Catalog     -40 to 85     PDIP | 16
SOIC | 16    
16PDIP: 181 mm2: 9.4 x 19.3 (PDIP | 16)
16SOIC: 77 mm2: 7.5 x 10.3 (SOIC | 16)    
UC28025 Order now Boost
Flyback
Forward
Full-Bridge
Half-Bridge
Push-Pull    
Current
Feedforward
Voltage    
9.2     12     1000     9.2/8.4     45     1.5     Adjustable Switching Frequency
Current Limiting
Error Amplifier
Multi-topology
Programmable Max Duty Cycle
Soft Start
Synchronization Pin    
Catalog     -40 to 105     PDIP | 16
SOIC | 16    
16PDIP: 181 mm2: 9.4 x 19.3 (PDIP | 16)
16SOIC: 77 mm2: 7.5 x 10.3 (SOIC | 16)    
UC2825 Order now Boost
Flyback
Forward
Full-Bridge
Half-Bridge
Push-Pull    
Current
Feedforward    
9.2     12     1000     9.2/8.4     80     1.5     Adjustable Switching Frequency
Current Limiting
Error Amplifier
Multi-topology
Programmable Max Duty Cycle
Soft Start
Synchronization Pin    
Catalog     -40 to 85     PDIP | 16
SOIC | 16    
16PDIP: 181 mm2: 9.4 x 19.3 (PDIP | 16)
16SOIC: 77 mm2: 7.5 x 10.3 (SOIC | 16)    
UC2825B Samples not available Boost
Flyback
Forward
Full-Bridge
Half-Bridge
Push-Pull    
Current
Voltage    
16     22     1000     16/10     50     2     Adjustable Switching Frequency
Current Limiting
Dead Time Control
Error Amplifier
Leading Edge Blanking
Multi-topology
Programmable Max Duty Cycle
Soft Start
Synchronization Pin    
Catalog     -40 to 85     PDIP | 16
SOIC | 16    
16PDIP: 181 mm2: 9.4 x 19.3 (PDIP | 16)
16SOIC: 77 mm2: 7.5 x 10.3 (SOIC | 16)