Features

Accurate positive linear voltage

1A, 0.5V voltage drop

guarantee reverse input/ Output low leakage voltage isolation

low static current, loaded

can be adjusted output voltage version

3.3V and 5V The fixed version output logic shutdown ability

short -circuit power limit 3% vehicle identification number current limit

Remote load voltage load adjustment

Explanation

ucc381 -3/-5/-ADJ positive linear series tingler is designed for low dropout applications for low static power. Made with BICMOS technology, it is very suitable for low input and output decentrals. UCC381 will pass 1A, and also requires only 0.5V input voltage to clean. The voltage reduction linear decline has the output current, making it less than 100 millivolves at 200 mAh. Static current is always less than 650 Wei'an. In order to prevent reverse current, the upper circuit limits the minimum forward voltage to 50mV. Once the forward voltage limit is reached and the input voltage is reduced, the input output leaning voltage will remain unchanged until the underwriter locks the regulator.

UCC381-3 and UCC381-5 versions are pre-set with 3.3V or 5.0V, respectively. In addition, remote sensing can be loaded directly by connecting VOUTS pin. The output voltage was then adjusted at room temperature to 1.5%, and the temperature exceeded 2.5%. The UCC381-Adj version has a adjustable output voltage that can be defined by external users to define the resistor RA programming.

(continuity) Low pressure difference 1 Ampel linear stabilizer series

Absolutely maximum rated value

Vehicle recognition number. 9V current transformer. -0.3 to 3V

Storage temperature. -65 ° C to+150 ° C

Conclusion temperature. -55 ° C to+150 ° C

Lead temperature (welding, 10 seconds). +300 degrees Celsius

current storage, negative output to the specified terminal. See the packaging part of the data manual to understand the thermal coupling and consideration of the packaging. All voltages are related to grounding.

Explanation (continued)

The internal limitation of short -circuit current is limited. The device responded to the continuous over -current state by closing after delay. The device then closed for a period of time, that is, 32 times in TDELAY. The device then starts to connect and disconnect the pulse of the 3%T/(T+T) duty cycle. This is greatly reducedPower loss at short circuit, so if it is necessary to heat dissipation, it must only adapt to normal work. On the fixed output version of the device, TON is fixed at 400 microseconds -the minimum value of guarantee. On the adjustable version, the opening time of the external capacitor settings.

Tube Foot Instructions

Computer tomography: For UCC381-3 and UCC381-5 versions, this is to close the sales. When pulling down Essence For the UCC381-Adj version, a capacitor requires a capacitor between CT pin and GND in order to set TTIME:

ground: All voltage during the current (typical) equation They are measured relative to the pin. This is a low -noise ground reference input used to adjust. The output off -coupled container should be connected to the pin 7.

Vehicle recognition number: The positive power input of the regulator. If the power supply distance is more than 1 inches, the low ESR and ESL capacitors of at least 1 μF are used to bypass the foot.

The regulator output. The stabilizer does not require the minimum output capacitance to ensure stability. Select the appropriate size capacitor,

Typical application circuit

SPECT to the required transient load. For example, if the load is very dynamic, a large capacitor will smoothly respond to the load jump.

Guarantor: feedback for adjusting the output voltage of the regulator. For loads with a large resistance distance with the VOUT tube foot, the VOUTS tube foot can be used to move the control loop of the resistor into the regulator, thereby effectively eliminating IR associated with the load path. For local regulations, you only need to connect this pin directly to the VOUT pin. For the UCC381-Adj version, the output voltage can be set by two external resistors according to the following relationship: where R1 is a resistor connected between Vout and VOUTs, and R2 is a resistor connected to VOUTS and GND.

Application information

Overview

UCC381 series low voltage differential linear (LDO) voltage regulator provides adjustable output voltage for applications with a load current as high as 1A. This stabilizer has a low -voltage difference and short -circuit protection function, making it very suitable for large current applications that require fault tolerance.

Short -circuit protection

UCC381 provides a unique short -circuit protection circuit, which can reduce power consumption during the failure. When the overload is detected, the device enters the pulse working mode with a 3%duty ratio of 3%, thereby reducing the requirements of the heat sink during the failure. As shown in Figure 1, UCC381 has two current thresholds to determine its behavior during the failure.

When the current of the regulator exceeds the current threshold, the UCC381 will turn off the time of 32 times(T). If the short -circuit current exceeds the peak current limit, the regulator will limit the current to the peak current limit within this time period. The peak current limit is 1 amp than the current threshold. As shown in Figure 1, the regulator will continue to be in the pulse mode until the fault is cleared. Open and turn on and open

During the startup process, the capacitance load on the regulator output will be displayed as a short circuit. If the capacitance is too large, the output voltage within the initial period will not be adjusted, and UCC381 will enter the pulse working mode. The peak current limit, cycle and load characteristics determine the maximum value of the output capacitor charging. For the constant current load, the maximum output capacitor is as follows:

For the worst case, the minimum value of the opening time (T) and the peak current limit (i) should be used. The adjustable version is allowed to adjust TTIME through the capacitor on the CT pin:

For the resistance load (R), the maximum output capacitor can be estimated through the following formulas:

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UCC381 short -circuit is positive.

Application information (continued)

A dropping performance

The reference box diagram, the leakage voltage of UCC381 is equal to the minimum voltage drop (v to v) on the MOSFET on the n channel. The voltage drop depends on working conditions, such as load current, input and load voltage and temperature. UCC381 achieves low RDSON by using the internal charge pump (V) of the driver's MOSFET gate. Figure 2 shows the relationship between the typical voltage and load current of 3.3V and 5V versions of the 3.3V and 5V versions of 3.0V.

The typical leakage performance of the adjustable version with different output voltage and load current showed a icon.

The operating temperature affects the RDS (opening) and voltage drops of UCC381. Figure 4 depicts the typical pressure drops of 3.3V and 5V versions when the 3A loads exceeds the temperature.

Voltage Programming

Reference typical application circuit, the output voltage of the adjustable version is performed by the resistance division at the Vouts pin, as shown in the figure.

For a fixed voltage version, the resistor division is set inside, and VOUTS pin should be connected to the VOUT pin. The maximum programming output voltage of the adjustable part is limited by the absolute rated value of the integrated circuit 9V (including the charge pump voltage) and its enhanced N -channel MOSFET capability. Unless the load current is far lower than the 1A rated value of the device, the output voltage is higher than 7V. The minimum output voltage is 1.25V, but the input voltage must always be greater than the UVLO of the part.

Shipping function

All versions include shutdown function, restricting static current restrictionsIt is 25 Wei'an. Turn off UCC381 by pulling the CT tube foot to 0.25V. As shown in the application circuit, a small logic -grade MOSFET or BJT transistor connected to the CT tube can be turned off by digital signal to turn off the device. If the CT pin does not lower, the IC will be pulled up in the pins to enable the regulator. The CT pin should not be forced to increase, because this will interfere with the short -circuit protection function. ShortcircuitPro explained the selection of adjustable timing capacitors-

Application information (sequel)

The packaging information of the data manual contains various packaging heat rated values. References. This section also includes the heat of an excellent article on the surface of the article, which is the basis of the following discussion.

The thermal design of UCC381 includes two working modes: normal mode and pulse mode. In normal operation, linear regulators and radiator must consume the power of the maximum forward voltage to the maximum load current. Assuming the constant current load, the expected heat rise at the junction joint can be calculated as follows:

where the θ is the thermal resistance and the power is dispersed. The thermal resistance of the two SOIC-8DP packaging (connected to the shell) is 22 degrees Celsius/watt. In order to prevent the regulator from entering the heat shutdown state, the shell of the ambient temperature θ must be kept below 150 ° C. For example, if the LDO is installed on a 5-square-inch 1 ounce copper pad, the thermal resistance of the knot temperature to the ambient temperature will become 40-70 degrees Celsius per watt. If the application requires lower thermal resistance, the heat dissipation performance of the device needs to be improved.

When the UCC381 regulator is in the pulse mode, due to the overload or short circuit in the application, the maximum average power consumption calculation is as follows:

As shown in the equity 6 as the equal form 6 The average power during the failure will be significantly reduced due to the duty cycle, so that the size of the radiator is suitable for normal operation. Although the peak power of the regulator during the cycle is significant, the heat quality of the packaging usually does not increase the knot temperature, unless the cycle increases to tens of milliseconds.

Polkaral suppression

Although UCC381 linear stabilizer has not optimized the rapid transient application (see UC182 fast LDO linear regulator ")