as1339 austriamicrosystems, as1339 Datasheet - Page 18

• Manufacturer Part Number: as1339
• Description: 650ma Rf Step-down Dc-dc For Pa, With Two Ldos
• Manufacturer: austriamicrosystems

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. 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
www.austriamicrosystems.com
C
IN1
PROCESSOR
Name
BASEBAND
, C
Li+ Battery
OUT
GPIO
GPIO
GPIO
DAC
GRM21BR61C475KA88
C0603C475K8PAC7867
+
C
GRM21BR60J106KE01
IN2
Connected
Part Number
PA_EN
Not
REFIN
TEST
IN1A
IN1B
EN1
EN2
IN2
AS1339
4.7µF
4.7µF
10µF
C
Figure 50
Revision 1.02
Voltage
6.3V
16V
10V
shows a typical application.
NC
AGND
LX
PAB
PAA
PGND
LDO1
LDO2
Type
X5R
X5R
X5R
2.2µH
C
C
C
LDO1
RF
LDO2
OUT
0805
0805
0603
Size
IN
BIAS
PA2
RF
IN
Murata
www.murata.com
KEMET
www.kemet.com
IN
BIAS
PA1
Manufacturer
IN
RF
OUT
RF
18 - 24
OUT