Explanation

UCC3810 is a high-speed BICMOS controller that integrates two synchronous pulse width modulators for offline and DC-DC power. The UCC3810 series provides perfect synchronization between two PWM by using the same oscillator. If necessary, the oscillator's sawtooth waves can be used for slope compensation.

UCC3810 uses the trigger to alternate between the modulation to ensure that one PWM does not move, interference, or other PWM in other ways. This trigger also ensures that the width of each pulse width is limited to a maximum duty ratio of 50%to ensure that sufficient shutdown time reset magnetic elements. This device contains many of the same elements of the UC3842 current mode controller series and combines the enhancement function of UCC3802. This can reduce the number of power components. The enhanced function includes the cutting edge of the current detection signal, the full -cycle failure restart, the CMOS output drive, and the low output that remains low when the power supply voltage is removed.

Absolutely maximum rated value

exceeding the free air temperature range (unless otherwise explained)

(1) The current is positive input to input , Negative output. All voltages are related to grounding.

(2) The stress that exceeds the absolute maximum rated value may cause permanent damage to the device. These are only stress rated values and do not mean that the function operations of the device under these or any other conditions exceed the instructions of the recommended operation conditions. Long -term exposure to absolute maximum rated conditions may affect the reliability of the device.

(3) In normal operations, VCC is powered by a streaming resistor. When the low impedance is driven, the maximum absolute voltage is 11 V, so that the VCC current does not exceed 20 mAh.

How to connect the external power level to UCC3810. The grille of the external power N vitrrus MOSFET is connected to the output end through a small current limit resistance. For most applications, a 10 ohm resistor is enough to limit the peak current, and it is also very practical in the resonance between suppressing the grid drive and MOSFET input resistance. The length of the long grid leads increases the gate capacitance, which requires a higher series grid pole resistance to damping the lead, MOSFET input power resistance, and the R-L-C groove formed by the output resistance of the device drive.

UCC3810 has two current detection input input input input of the inner front edge of the current detection signal. The blank time starts from OUT and lasts 55ns. During 55ns, the signal on CS was ignored. For most PWM applications, this means that CS input can be connected to the current fluid resistance, as shown in Figure 1. However, high -speed grounding practice and short -line length still require good performance.

oscillator

UCC3810 oscillator generates serrated waves at the CT. The rising time of sawtooth is set from RT to GND. Since the RT partial pressure is 1V, the current of the RT is 1V/RT. The actual charging current is 10 times higher. The decrease time is set by the internal transistor's pipe resistance, about 100Ω. During the drop time, all outputs were closed, and the maximum duty cycle was reduced to less than 50%. The larger timing capacitor increases the discharge time and reduces the frequency. However, the maximum duty cycle percentage is only a function of the timing resistor RT and the internal 100Ω discharge resistor.

Error amplifier output level

UCC3810 error amplifier is an operational amplifier with low output resistance and high input resistance. The output level of an error amplifier is shown in Figure 3. This output level allows an error error amplifier output swing close to GND, as high as a diode drop below 5V, and the performance loss of the amplifier is very small.

Application information (continued)

Synchronous high -voltage power supply

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Typical application

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