DCR01 Series

11

SBVS013C

ERROR FLAG

The DCR01 has an ERROR pin which provides a “power

good” flag, as long as the internal regulator is in regulation.

DECOUPLING

Ripple Reduction

Due to the very low forward resistance of the DMOS

switching transistors, high current demands are placed upon

the input supply for a short time. By using a good quality

low Equivalent Series Resistance (ESR) capacitor of 2.2

µF

(minimum) for the 5V input devices and a 0.47

µF capacitor

for the 12V and 24V devices, placed close to the IC supply

input pins, the effects on the power supply can be mini-

mized.

The high switching frequency of 400kHz allows relatively

small values of capacitors to be used for filtering the recti-

fied output voltage. A good quality low ESR capacitor of

1

µF placed close to the V

reduce the ripple.

It is not recommended that the DCR01 be fitted using an

IC socket as this will degrade performance.

ripple of 800kHz.

It is recommended that a 0.1

µF low ESR capacitor is

connected close to the output pin and ground to reduce noise

on the output. The capacitor values listed are minimum

values. If lower ripple is required then the filter capacitor

should be increased in value to 2.2

µF.

NOTE: As with all switching power supplies the best

performance is only obtained with low ESR capacitors

connected close to the switcher. If low ESR capacitors are

not used, the ESR will generate a voltage drop when the

capacitor is supplying the load power. Often a larger capaci-

tor is chosen for this purpose when a low ESR smaller

capacitance would perform as well.

APPLICATION NOTES

DCR01 SINGLE VOLTAGE OUTPUT

The DCR01 can be used to provide a single voltage output

by connecting, see Figure 1. The ERROR output signal will

the ERROR line however, the total load on the ERROR line

must not exceed the value given in the specification.

The output may be permanently enabled by connecting the

the DCR01 as only a small current flows. The switch SW1 can

be used to pull the ENABLE pin LOW, thus disabling the

output. The switching devices can be a bipolar transistor, FET

GENERATING TWO POSITIVE

OUTPUT VOLTAGES

Two DCR01s can be used to create output voltages of +3.3V

and +5V, as shown in Figure 2. The two DCR01s are

connected in self-synchronization, thus locking the oscilla-

tors of both devices to a single frequency.

The ERROR and ENABLE facilities may be used in a

similar configuration for a single DCR01. The filter capaci-

separate from each other and connected in close proximity to

their respective DCR01. If similar output voltages are being

used, it is not recommended that a single filter capacitor

connected together, as this could result is the overloading of

one of the devices.

DCR

01

V

OUT

V

IN

C

IN

(1)

C

R

C

V

O1

0V

ENABLE

V

REC

ERROR

V

S

U1

0V

SYNC

ERROR

DCR

01

V

OUT

V

IN

C

IN

(1)

C

R

C

V

O2

0V

ENABLE

V

REC

ERROR

V

S

U2

0V

SYNC

0V

OUT

ERROR

NOTE: (1) 2.2

µF capacitor with low ESR for 5V

devices and 0.47

µF for 12V and 24V devices.

FIGURE 2. Generating Two Positive Voltages from Self-Synchronized DCR01s.