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AS1339

Datasheet - A p p l i c a t i o n I n f o r m a t i o n

9 Application Information

The AS1339 is designed to supply power amplifiers for RF applications. The output power of the PA can directly be

controlled via the output voltage of the AS1339. Figure 50 shows a typical application.

Figure 50. Typical Application Diagram

Capacitor Selection for Step-Down Converter

Input Capacitor

To reduce the current peaks drawn from the battery or power source and to reduce the switching noise in the device an

input capacitor is highly recommended. At the switching frequency the impedance of the capacitor should be very low.

It’s recommended to use a X5R or X7R dielectric multilayer ceramic capacitor due to their small size, low ESR and

small temperature coefficients. For most applications a 4.7µF capacitor is sufficient. To decrease the interfering noise

and to lower the input ripple the capacitor value can be set higher (e.g. 10µF).

Output Capacitor

To ensure a stable loop regulation and a small output voltage ripple a low impedance capacitor should be used. It’s

recommended to use a X5R or X7R dielectric multilayer ceramic capacitor due to their small size, low ESR and small

temperature coefficients. For most applications a 4.7µF capacitor is sufficient. To achieve a better load-transient perfor-

mance and to decrease the output ripple the capacitor value can be set higher (e.g. 10µF).

Table 6. Recommended Capacitors for the Step-Down Converter

Name

Part Number

C

Voltage

Type

Size

Manufacturer

GRM21BR60J106KE01

10µF

6.3V

X5R

0805

Murata

www.murata.com

GRM21BR61C475KA88

4.7µF

16V

X5R

0805

C0603C475K8PAC7867

4.7µF

10V

X5R

0603

KEMET

www.kemet.com

BIAS

IN

PA1

BIAS

IN

PA2

BASEBAND

PROCESSOR

GPIO

GPIO

GPIO

DAC

+

PA_EN

EN1

EN2

TEST

IN2

REFIN

IN1B

IN1A

Li+ Battery

LDO2

LDO1

AGND

NC

PGND

LX

PAB

PAA

2.2µH

Not

Connected

AS1339