REG711

8

SBVS027A

CAPACITOR SELECTION

For minimum output voltage ripple, the output capacitor

capacitors generally have a higher Effective Series Resis-

tance (ESR) and may contribute to higher output voltage

ripple. Leaded capacitors also increase ripple due to the

higher inductance of the package itself. To achieve best

operation with low input voltage and high load current, the

also be surface-mount ceramic types. In all cases, X7R or

X5R dielectric are recommended. See the Typical Operating

Circuit shown in Figure 3 for component values.

The approximate efficiency is given by:

or

Table II lists the approximate values of the input voltage at

which the device changes internal operating mode.

OPERATING MODE

PRODUCT

REG711-2.5

> 3.2V

REG711-2.7

> 3.4V

REG711-3.0

> 3.7V

REG711-3.3

> 4.0V

REG711-5.0

Step-up only

TABLE II.

See efficiency curves in the Typical Performance Curves

section for various loads and input voltages.

LAYOUT

traces. To minimize both input and output ripple, keep the

capacitors as close as possible to the regulator using short,

direct circuit traces.

A suggested PCB routing is shown in Figure 4. The trace

lengths from the input and output capacitors have been kept

as short as possible. A star ground system has been imple-

mented, with pin 5 as the center of the star. No ground plane

is provided in other layers, as this will provide capacitive

coupling for noise spikes.

FIGURE 4. Suggested PCB Design for Minimum Ripple.

With light loads or higher input voltage, a smaller 0.1

µF

minimize output voltage ripple, increase the output capaci-

The capacitors listed in Table I have been used with the

REG711. This is only a representative list of those parts that

are compatible, and not the results of a complete survey of

an industry-wide offering.

EFFICIENCY

The efficiency of the charge pump regulator varies with the

output voltage version, the applied input voltage, the load

current, and the internal operation mode of the device.

FIGURE 3. Typical Operating Circuit.

C

PUMP

0.22

µF

V

IN

V

OUT

C

IN

2.2

µF

PGND

ENABLE

GND

2

76

8

54

3

C

OUT

2.2

µF

REG711

NOTE: All Capacitors 1206 Size

RATED

DIELECTRIC

PACKAGE

WORKING

MANUFACTURER

PART NUMBER

VALUE

TOLERANCE

MATERIAL

SIZE

VOLTAGE

Kemet

C1206C255K8RAC

2.2

µF

±10%

X7R

1206

10V

C1206C224K8RAC

0.22

µF

±10%

X7R

1206

10V

Panasonic

ECJ3YB1A225K

2.2

µF

±10%

X7R

1206

10V

ECJ3VB1C224K

0.22

µF

±10%

X7R

1206

16V

Taiyo Yuden

LMK325BJ106KN

10

µF

±10%

X5R

1210

10V

EMK316BJ225KL

2.2

µF

±10%

X7R

1206

16V

TKM316BJ224KF

0.22

µF

±10%

X7R

1206

25V

TABLE I. Capacitors That Have Been Successfully Used With The REG711.