Features

UL1950 recognition

DIP-18 and SO- 10 Packaging

55 W/in3 (3.3 W/CM3) Power Dengnei

Synchronous

Hot protection

1000 VRMS isolation

#8226 ; 400 kHz switch

125 suitable for 55 ° C short circuit protection

12 # 8722; v, 24 v input

5 v output

Application

# 8226; Use point power conversion

Digital interface power supply

Power noise reduction

Instructions DCR02

series is a series of high -efficiency, input isolation, output adjustment DC /DC converter. In addition to the 2-W nominal and electrical isolation output power capabilities, this series of converters also provide very low output noise and high precision.

The DCR02 series is packaged in standard mold pressure equipment, which provides standard JEDEC outlines suitable for large -scale assembly.

DCR uses the same technology as a standard equipment package, so it has achieved very high reliability.

Typical features

Function description

Overview

DCR02 series provided provides provided It isolates the unsettled power supply from an input voltage. This series of products provides various adjustment output voltage when the rated output power is 2W.

Power level

The input power supply is cut with a frequency of 400 kHz (internal oscillator divided by 2) to drive the centered tap ring transformer.

Rectification

Transformer output is a full -wave rectification and smooth external capacitor connectionReceive VREC.

regulator

The internal low voltage differential regulator provides a good adjustment output voltage within the work range of the entire device.

oscillator and door dog

DCR02 uses an internal jagidifier generator to provide 800 KHz on the 800 KHz. The operation of the oscillator is monitored by the door dog. If the oscillator fails or the synchronous pipe foot is at a low level (shutdown mode), the door dog will make three states of the output drive circuit. When the synchronous pin is returned to high level, it is restored to normal work.

Synchronous

If multiple DCR02 is used, frequent shooting and other electrical interference will occur. This interference is caused by slight changes in the switching frequency between the converter. DCR02 overcome this by allowing the device to synchronize with each other. By connecting the synchronous pipe foot together, you can synchronize up to eight equipment. At the same time, you should pay attention to minimize the tracking capacitance.

A large number of strange capacitors on the synchronous pipe foot reduce the frequency of the internal oscillator. If this reduces a large amount, DCR02 may be taken out with its optimized operating parameters, and may cause magnetic saturation to damage the device.

If the device is synchronized, it should be noted that all equipment consumes the maximum current at the same time when starting. This will cause the input voltage to decrease. If the minimum input voltage is lower, the device may not be started. Low equivalent series resistance (ESR) 2.2 F ceramic capacitor should be connected as close to the device input pins as possible.

If you need to synchronize more than 8 equipment, it is recommended to use external synchronization. The detailed information of this program contains the external synchronization of the DCP01/02 series DC/DC converter in the application report, which can be downloaded from the following URL.

Structure

DCR02 is made of the same technology as standard IC packaging. There is no substrate in the packaging. DCR02 is composed of a driver IC, low voltage differential voltage regulator, rectifier diode and winding magnetic ring, all of which are installed on a lead frame. DCR02 does not require a special printing circuit board (PCB) assembly and processing because there is no soldering in the package. As a result, a DC/DC converter with inherent high reliability.

additional function

Disable/enable

DCR02 can be disabled or enabled by using the leakage CMOS door drive synchronization foot. If the synchronous pin is low, DCR02 is disabled. The failure time depends on external load. The internal disable function is implemented within 2 μs. Remove the pull -down function can be enabled by DCR02.

The capacitor load on the synchronous pipe foot should minimize the frequency of internal oscillator. For information about how to eliminate the additional capacitance on the synchronous pipe foot, see the application report sbaa035Essence The oscillator frequency can be measured at VREC, because this is the base frequency of ripples.

Output enable/disable

By pulling the pins (which will be connected to 0Vout), the adjustment output of DCR02 can be disabled. The enable pins will be kept at a high level (which will be connected to VREC) to enable the adjustment output voltage, so as to allow the output from the isolation side, as shown in Figure 3.

Error logo

As long as the internal regulator is in a adjustable state, DCR02 has an error pin, which provides a good sign of power supply.

Definement

Reduce ripples

Because the positive resistance of the DMOS switch transistor is very low, high current demand for the input power supply in a short time. By placing a high -quality low ESR 2.2 F ceramic capacitor near the IC power input pin, the impact on the power supply can be minimized.

The high switching frequency of 400kHz allows the use of relatively small capacitors to filter the rectifier output voltage. High -quality, low ESR 1 μF ceramic capacitor close to the VRC pin and output ground, which can reduce ripples.

It is not recommended to install DCR02 with IC sockets because it will reduce performance.

The output of VREC is a full -wave rectification and generating a ripple of 800 kg.

It is recommended to connect 0.1 F low ESR ceramic capacitor to the position near the output pin and ground to reduce the output noise. The listed capacitance value is the minimum value. If a lower ripple is required, the value of the ceramic filter capacitor should be increased to 2.2 μF.

Note: Like all switching power supply, only the low ESR ceramic capacitor is connected to their respective bus can the best performance. If low ESR ceramic capacitors are not used, ESR will generate voltage drops when the capacitor is powered on the load. Under normal circumstances, when low ESR capacitors can also play a role, larger capacitors are usually selected.

Application Instructions

DCR02 single voltage output

As shown in Figure 3, DCR02 can provide single voltage output by connecting circuit. For a specific DCR02 used, the error output signal is pulled to the VOUT value. The value of RERR depends on the load on the error line; however, the total load on the error line must not exceed the given value given in the specification.

By connecting the pins to the VREC pin, the output can be permanently enabled. DCR02 can be connected to VREC remotely through the pull -up resistor (REN); the value of this resistor is not important for DCR02 because there is only a small current flow. The switch SW1 can be used to pull the pins and lower the output. Switching deviceIt can be a bipolar transistor, field effect transistor or mechanical equipment; the main load of its sensing is REN.

The two positive output voltage is generated

Two DCR02 can be used to create two+5 V output voltage, as shown in Figure 4. Two DCR02 is connected by a synchronization manner to lock the oscillator of the two devices to a frequency.

Error and enabled facilities can be used in similar configurations of a single DCR02. Filter capacitors connected to the VREC pin (CFILTER) should maintain each other and be closely connected to the corresponding DCR02. If a similar output voltage is used, it is not recommended to connect a single filter capacitor (increased capacitance) that connects the two VREC tubes together, because this may cause one of the equipment to overload.

The bipolar voltage is generated by two self -synchronous DCR02

can be configured with two DCR02 to generate double pole power supply (that is, ± 5 V); The circuit must be connected as shown in Figure 5.

Pay attention to both DCR02 as a positive voltage regulator; therefore, the error tube foot, enable pipe foot and VREC tube foot are related to their respective devices, 0 V, must not be connected together.

PCB layout

Polite and noise

Consider the layout of PCB to obtain the best results.

DCR02 is a kind of switching power supply, so the peak current needs can be applied to the input power supply. In order to prevent the power supply from instantly decreased instantly during the fast switching pulse, the grounding and power plane should be used to track the power of the DCR02 input; this also helps reduce the noise on the circuit. If this is impossible, the supply must be connected into a star, and the track is as wide as possible.

If the synchronous pipe foot is used, the tracking between the equipment synchronization foot should be short to avoid bandate capacitors. If synchronous pins are not used, it is recommended to place a protective ring (connected to input grounding) around the pin to avoid any noise pickup.

The output should be obtained from the device with ground and power plane. This can ensure the minimum loss.

A high -quality, low ESR ceramic capacitor is placed where as close to the input end to reduce the reflex ripple and ensure the stable start.

In addition, a high -quality, low ESR ceramic capacitor is placed as close to the output end and output ground as possible, and also provides the best ripples and noise performance.

Hot Management

Due to the high power density of the device, it is recommended to provide ground layers on the output end. The output regulator is installed on a copper lead frame, and the floor is used as an effective cooling tablet.