7

®

DCV01

FIGURE 1. Connecting the DCV01 in Series.

FUNCTIONAL DESCRIPTION

OVERVIEW

The DCV01 offers up to 1W of unregulated output power

with a typical efficiency of up to 85%. This is achieved

through highly integrated packaging technology and the

implementation of a custom power stage and control IC. The

circuit design utilizes an advanced BiCMOS/DMOS pro-

cess. Separate primary and secondary transformer windings

give good isolation and low barrier capacitance.

POWER STAGE

This uses a push-pull, center-tapped topology switching at

400kHz (divide by 2 from 800kHz oscillator).

OSCILLATOR AND WATCHDOG

The onboard 800kHz oscillator generates the switching

frequency via a divide by 2 circuit. The oscillator can be

synchronized to other DCV01 circuits or an external source,

and is used to minimize system noise.

A watchdog circuit checks the operation of the oscillator

pin LOW. The output pins will be tri-stated. This will occur

in 2

µs.

THERMAL SHUTDOWN

The DCV01 is protected by a thermal shutdown circuit. If the

on-chip temperature exceeds 150

°C, the device will shut

down. Once the temperature falls below 150

°C, normal

operation will resume.

SYNCHRONIZATION

In the event that more than one DC/DC converter is needed

onboard, beat frequencies and other electrical interference

can be generated. This is due to the small variations in

switching frequencies between the DC/DC converters.

The DCV01 overcomes this by allowing devices to be

synchronized to one another. Up to eight devices can be

ing care to minimize the capacitance of tracking. Stray

capacitance (> 3pF) will have the effect of reducing the

switching frequency, or even stopping the oscillator circuit.

If synchronized devices are used, it should be noted that, at

start up, all devices will draw maximum current simulta-

neously. This can cause the input voltage to dip and should

it dip below the minimum input voltage (4.5V), the devices

may not start up. A 2.2

µF capacitor should be connected

close to the input pins.

If more than eight devices are to be synchronized, it is

nal device. Details are contained in a separate applications

bulletin (AB-153).

CONSTRUCTION

The DCV01’s basic construction is the same as standard ICs.

There is no substrate within the molded package. The

DCV01 is constructed using an IC, rectifier diodes, and a

wound magnetic toroid on a leadframe. As there is no solder

within the package, the DCV01 does not require any special

PCB assembly processing. This results in an isolated

DC/DC converter with inherently high reliability.

ADDITIONAL FUNCTIONS

DISABLE/ENABLE

The DCV01 can be disabled or enabled by driving the SYNC

pulled low, the DCV01 will be disabled. The disable time

depends upon the external loading; the internal disable func-

tion is implemented in 2

µs. Removal of the pull down will

cause the DCV01 to be enabled.

in order to prevent a reduction in the oscillator frequency.

DECOUPLING

Ripple Reduction

The high switching frequency of 400kHz allows simple

filtering. To reduce ripple, it is recommended that at least a

1

µF capacitor is used on V

decoupled to pin 5. A 2.2

µF low ESR capacitor on the input

of the 5V in versions, and a 0.47

µF low ESR cap on the 24V

DCV01 in versions is recommended.

DCV

01

V

OUT 1

V

SUPPLY

V

S

0V

DCV

01

V

OUT 2

V

SYNC

IN

SYNC

IN

V

S

0V

0V

0V

COM